$ \
 UNEP  WMO
Greenhouse    as Inventory
           Reference Manual
                                      First Draft
 IPCC/OECD
Joint Programme
         IPCC Draft Guidelines for National
             Greenhouse Gas Inventories
           •
                !
                i          Volume 3

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                   IMPORTANT NOTICE
The material contained in this document is in draft, and is sent to you
for comment as part of the IPCC review process. The document has
not yet been approved by the IPCC and must not be published or cited
as an official IPCC report.

As a result of the review process this draft is expected to undergo
amendment and correction before being presented for approval by
IPCC WGI in September 1994 and by IPCC plenary in November
1994.

Material contained in this draft may be copied in whole or in part for
review by others, but a copy of this notice should be attached to all
such copies.
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                          ACKNOWLEDGEMENTS
The IPCC/OECD Programme on the Development of a Methodology for National
Inventories of Net Greenhouse Gas Emissions would like to thank those governments,
international organizations, and individuals whose contributions have made the
development of this methodology possible.

Financial support for the programme has been provided by the United Nations
Environment Programme, the Global Environment Facility, the Organization for Economic
Co-operation and Development Environment Directorate, the International Energy
Agency, the European Community, and the governments of the United States, the United
Kingdom, Switzerland, Italy, Norway, Sweden, and the Netherlands, Germany, France,
Canada, and Australia. Significant (non-financial) contributions and resources in kind came
from the United Nations Environment Programme, the United States, the Netherlands,
the United Kingdom, Japan, the Organization for Economic Cooperation and
Development, and the International Energy Agency.
Many individuals have contributed in various ways to the programme.  Those who have
drafted, commented, and advised in the direct support of the production of these
documents include: Jane Ellis, Tim Simmons, and Karen Treanton, of the International
Energy Agency; Craig Ebert and Barbara Braatz of ICF Inc.; Karl jorss of the Federal
Environment Agency in Germany; Gordon Mclnnes of the CEC/European  Environment
Agency Task Force & UNECE Task Force on Emission Inventories; James Penman of the
UK Department of the Environment; Andre van Amstel of the National Institute for Public
Health and Environmental Protection (RIVM) in the Netherlands; Jan Feenstra, Ella
Lammers, and Pier Vellinga, of the Institute for Environmental  Studies in the Netherlands;
Berrien Moore of the University of New Hampshire; Gerald Leach, Jack Siebert, Susan
Subak,  and Paul Raskin, of the Stockholm Environment Institute; Lucy Butterwick, Martin
Parry, and Martin Price, of the University of Oxford;; Michael Short and Peter Usher of the
United Nations Environment Programme; N Sundararaman of the IPCC Secretariat; Bert
Bolin, Chairman of the Intergovernmental Panel on Climate Change; Tim Weston, Peter
Bolter  and Austin Pearce of TMS Computer Authors Ltd.; Sir John Houghton, Bruce
Callander, Buruhani Nyenzi and Kathy Maskell of the IPCC Working Group I Secretariat;
Paul Schwengels, Jan Corfee-Morlot, Jim McKenna, Scott Lurding, and Hans Sperling, of the
OECD Environment Directorate.

The IPCC/OECD Programme would like to thank all the participants in the expert groups
and in the various regional workshops, especially the coordinators and co-chairs of expert
groups process to provide improvements in technical methods; L Gylvan Meira Filho of
the National Institute for Space Research, Brazil;  Berrien Moore of the University of New
Hampshire; Paul Crutzen of the Max Planck Institute for Chemistry; Elaine Matthews of
NASA; A P Mitra, of the National Physics Laboratory in India; Nigel Roulet of York
                                                                    ACKNOWLEDGEMENTS. I

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ACKNOWLEDGEMENTS
                       University in Canada; K Minami of the National Institute for Agro-Environmental Sciences
                       in Japan; M A K Khalil of the Oregon Graduate Institute; Alan Williams of the University of
                       Leeds; Dina Kruger, Susan Thornloe, and Lee Beck, of the US Environmental Protection
                       Agency; Audun Rosland of the State Pollution Control Authority in Norway; Frank
                       Shephard of British Gas pic; Richard Grant of the E&P Forum; Michael Gibbs and Jonathan
                       Woodbury of ICF Inc.; Lis Aitchison of the Energy Technology Support Unit; Ron Lerig of
                       the University of New England in Australia; Mark Howden of the Bureau of Resource
                       Sciences, Australia; T Ramasami of the Central Leather Institute in India; Robert Delmas of
                       the Universite Paul Sabatier; Dilip Ahuja of the Bruce Company; Chris Veldt and Jan
                       Berdowski of the National Organisation for Applied Scientific Research (TNO-IMW) in
                       the Netherlands; and Jos Olivier of the RIVM.
                       National case  studies were contributed by: Audun Rosland of the State Pollution Control
                       Authority in Norway, Peter Cheng of the Department of Arts, Sport, the Environment,
                       and Territories in Australia, Jane Legget of the US Environmental Protection Agency, Art
                       Jacques of Environment Canada, Sture Bostrom of Finland, and Karl Jorss of the Federal
                       Environment Agency in Germany, Simon Eggleston of Warren Spring Laboratory in die
                       United Kingdom, Andre van Amstel of the National Institute for Public  Health and
                       Environmental Protection (RIVM) in the Netherlands! I B Obioh of Obafemi Awolowo
                       University Nigeria, P A Ratnasiri of the Ceylon Institute of Scientific and Industrial
                       Research, Gordon Mclnnes of the CEC/European Environment Agency Task Force &
                       UNECE Task  Force on Emission Inventories, Anne Niederberger-Arquit of the Federal
                       Office of Environment, Forests and Landscape in Switzerland, and Kendaro Doi of the
                       Japan Environment Agency.
                       A very large number of experts have participated in IPCC/OECD expert groups and
                       workshops. All of these contributors have played contructive roles in shaping methods
                       presented here. These efforts reflect an important contribution to the implementation of
                       the Framework Convention on Climate Change, and are greatly appreciated.
 ACKNOWLEDGEMENTS.!

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                                                          PREFACE
The signature of the UN Framework Convention on Climate Change (UNFCCC) by
around 150 countries in Rio de Janeiro in June 1992 indicated widespread recognition that
climate change is a potentially major threat to the world's environment and economic
development. Human activities have substantially increased atmospheric concentrations of
greenhouse gases, thus perturbing the earth's radiative balance. According to projections
from climate models, a global  rise of temperature is a likely consequence. The potential
impacts of climate change such as sea level rises and changes in local climate conditions -
such as temperatures and precipitation patterns - could have important negative impacts
on the socio-economic development of many countries.
The ultimate objective of the  Convention is the stabilisation of greenhouse  gas
concentrations in the atmosphere at a level that would prevent dangerous anthropogenic
interference with the climate  system. Such a level is to be achieved within a time frame
sufficient to allow ecosystems to adapt naturally to climate change.. The Convention also
calls for all Parties to the Conference to commit themselves to three objectives:
•  To develop, update periodically, publish, and make available to the Conference of the
    Parties their national inventories of anthropogenic emissions of all greenhouse gases
    not controlled  by the Montreal Protocol.
•  To use comparable methodologies for inventories of greenhouse gas emissions and
    removals, to be agreed upon by the Conference of the Parties.
•  To formulate, implement, publish and update regularly national programmes
    containing measures to mitigate climate change by addressing anthropogenic
    emissions.
By the time of the Second World Climate Conference in Geneva in October - November
 1990, the need for  a standard methodology for compiling national emission inventories
was obvious. Under the auspices of the Organisation for Economic Cooperation and
Development (OECD) and the International Energy Agency (IEA), with support from the
USA, the UK and Norway, an initial compendium of methods (covering all gases except
chlorofluorocarbons (CFCs)  which were already accounted for under the Montreal
Protocol). This document was discussed  in detail by a meeting of experts (including many
representatives of non-OECD countries) in  Paris in February 1991. It was then adopted in
a slightly modified form at the fifth session of the Intergovernmental Panel on Climate
Change (IPCC) in March 1991 as the starting point for a set of IPCC guidelines to be used
by countries  drawing up national inventories of greenhouse gas emissions.
The IPCC Guidelines for National Greenhouse Gas Inventories consists of three volumes: the
Greenhouse Gas Inventory Reporting Instructions, the Greenhouse Gas Inventory  Workbook and

                                                                                          PREFACE.I

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PREFACE
                       the Greenhouse Gas Inventory Reference Manual. The Guidelines are being distributed world-
                       wide to national experts for review before adoption.

                       Further development of the methodology has been undertaken by the Scientific
                       Assessment Working Group (WGI) of the IPCC, working in close collaboration with the
                       OECD and the IEA under the IPCC/OECD programme on emissions inventories. The
                       objectives of the programme are:

                       •   Development and refinement of an internationally agreed methodology and software
                           for calculation and reporting of national net emissions.

                       •   Efforts to encourage widespread use of the methodology by countries participating in
                           the IPCC and Parties to the UN Framework Convention on Climate Change.

                       •   Establishment of procedures and a data management system for collection, review and
                           reporting of national data.

                       In the Guidelines, default methods and assumptions have  been developed for
                       characterising the major sources and sinks of greenhouse gases. Countries have the option
                       of using the various methods depending on their own needs and capabilities. Other more
                       detailed methods are also discussed. However, the IPCC/OECD programme is developing
                       a common reporting and documentation framework for all inventories. This will provide
                       for comparison of these methodologically diverse national estimates. It is essential that
                       guidelines for this methodology are internationally agreed upon, and this will be achieved
                       through workshops and expert groups with a broad geographical base.

                       Additionally, the IPCC/OECD programme is charged with continuing to improve the
                       methodology. This is being achieved through:

                       •   expert groups which review and recommend changes to the method

                       •   results from country studies
                       •   comments and preliminary inventories from countries

                       •   feedback from technical workshops held in Asia, Africa, Latin America and Central and
                           Eastern Europe

                       About thirty five countries from all over the world have submitted their preliminary
                       inventory data on anthropogenic greenhouse gas emissions and  removals from different
                       sources, using a range of approaches including the IPCC methodology. The  results of all
                       the above activities have been considered in developing the current Guidelines.

                       The IPCC/OECD programme gives technical support to the greenhouse gas inventory
                       components of country study projects sponsored by UNEP, Asian Development Bank,
                       individual countries etc.. Countries participating in these projects are developing national
                       emission  inventories. These country studies will contribute to:

                       •   development of national capacity and capability (including improving baseline data)

                       •   promulgation of the methodology

                       •   realistic testing of the methodology and its guidelines in order to identify strengths
                           and weaknesses

                       Over thirty countries are currently working on  country studies with support from various
                       sponsors.
PREFACE.2

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                                                       CONTENTS
                                                                              -.K f
Introduction..
Conclusion....
References ....
I    Using the IPCC Guidelines
Before you start.     .  ™ .
UVIWI *•» ^WM UkU> M» ................................................. ...i
General Notes on the Guidelines......	„....
            ivIJgSJfc?.',
Chapter I Emissions From Energy
I. I   Introduction	
| .2   Emission Factor Data...............	„	_	
1.3   Enerev Activity Data..............................	
         O/  ««•*»"•/ .^.-•w..... [[[
1.4   Carbon Dioxide Emissions from Energy	
1.5   Greenhouse Gas Emissions from Stationary Combustion	
1.6   Burning Traditional Biomass Fuels	
1.7   Greenhouse Gas Emissions from Mobile Combustion.—	
1.8   Fugitive Emissions from Coal Mining, Handling and Utilization....
1.9   Fugitive Emissions From Oil And Natural Gas Systems	
	1-5
	1-6
	1-7
	1-10
	1-40
	1-61
	1-66
	1-89
.	1-105

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CONTENTS
                  2   Industrial  Processes
                  2.1   Overview    --------- ..... [[[ 2-3
                  2.2  Carbon Dioxide Emissions From Industrial Processes .................................................. 2-4
                  23  References   [[[ [[[ 2-13

                  3   Solvent Use
                  3.2  NMVOC Emissions from Solvent Use [[[ 3-3
                  3.3  References  [[[ 3-5

                  4   Emissions From Agriculture
                  4.|  Overview   [[[ 4-3
                  4.2  Methane Emission From Domestic Livestock Enteric Fermentation
                       And Manure Management [[[ 4-5
                  4.11 References    [[[ 4-23
                  Appendix A
                       Data Underlying Default Emission Factors for Enteric Fermentation .................... 4-32
                  Appendix B
                       Data Underlying Default Emission Factors for Manure Management ..................... 4-39
                  Appendix C
                       Derivation of Tier 2 Enteric Fermentation Equations .................................................. 4-48
                  4.3  Methane Emissions from Flooded Rice Fields [[[ 4-52
                  4.4  Agricultural Burning [[[ 4-69
                  4.5  Nitrous Oxide Emissions from Agricultural Soils [[[ 4-85

                   5    Emissions From Land Use Change And Forestry

                   5.2   Basic Calculations [[[ 5-10

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                                                                                        CONTENTS
6        Methane Emissions From Waste
6.1   Methane Emissions From Landfills.	...............	...................	.......................	6-5
6.2   Methane Emissions From Wastewater Treatment	6-21
6.3   Emissions From Waste Incineration............	........................	._...„....	.....6-33
6.4   References	6-35
                                                                                              CONTENTS.3

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                      PART I
            INTRODUCING THE
          REFERENCE MANUAL
PART I
INTRODUCTION.I

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                                                                                            INTRODUCTION
              INTRODUCTION

              This Reference Manual is one of three volumes of the IPCC Draft Guidelines for
              National GHG Inventories. It provides a compendium of information on the
              various human activities which cause greenhouse gas emissions to or
              removals from the atmosphere. It builds on work carried out in preparation
              of the OECD Report: Estimation of Greenhouse Gas Emissions and Sinks, Final
              Report From the OECD Experts Meeting, 18-21 February 1991, (OECD, 1991).
              In August 1991, the IPCC/OECD  joint programme distributed this
              document as a starting point for development of guidelines for national
              inventories of greenhouse gases. In some sections for which no recent
              methodologies are available, it incorporates text with very little change from
              that document. In some areas, detail presented in the earlier report is
              summarized here. The OECD (1991) document remains a valuable
              reference document for national experts and others interested in the
              development of the IPCC National GHG Inventory Methods. In particular,
              detailed discussions of the reasoning behind some of the technical decisions
              made early in the IPCC/OECD programme can be found there.

              Another major published resource document heavily used in the preparation
              of this Manual is the Proceedings of an International IPCC Workshop on Methane
              and Nitrous Oxide, Amersfoort, NL, 3-5 February 1993 (van Amstel, 1993). To
              provide technical information for  improvement of the early methods known
              to be weak, the IPCC/OECD programme established informal expert groups
              to work toward reaching international agreement on proposed revisions to
              the  guidelines. A major landmark in this effort was the Amersfoort
              workshop sponsored by the Dutch government and hosted by the
              Netherlands National  Institute of  Public Health and Environmental
              Protection (RIVM). National experts presented their findings at the
              workshop and then discussions were held in working group sessions. The
              conclusions and recommendations have been drawn upon in the preparation
              of the Guidelines.

              In preparing this document, the IPCC/OECD has also received valuable
              technical input from a number of other international workshops. The overall
              purpose of these workshops was to provide a forum for experts to discuss
              ways to improve the methodologies and  reporting procedures and to ensure
              widespread participation in the development process. Many of the
              recommendations received have been incorporated into this revised Manual.
              In general, the basic approach to estimating national emissions is similar
              across the various gases and human activities which are sources or sinks.
              Fundamentally, emissions are a product of activity data and emission factors.

              Activity data are some quantitative measures of the level of the relevant
              human activity which occurs in the country (or region) of interest, during
              the  inventory year. Activity data range from fuel combustion and industrial
              production statistics to numbers of domesticated animals of various types,
              to hectares of forest land converted to other uses.

              Emission Factors are average relationships between a level of activity and the
              expected level of emissions which would result. Ideally they are derived
              from a number of data points of monitored emission levels from a single
              type of activity or technology being used  in different places under different
              conditions.
PART I
                                                                                           INTRODUCTION.3

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INTRODUCTION
                                    In reality, these calculations are often more complicated than this would
                                    indicate, with several steps being involved in the calculation of each of the
                                    general terms - activity data and emission factors. But it is useful to keep this
                                    general structure in mind as it provides an organizing framework for all of
                                    the calculations and a means of evaluation and comparison.

                                    The Reference Manual frequently provides a number of different possible
                                    methodologies or variations for calculating a given emission. In most cases
                                    these represent calculations of the same form but the differences are in the
                                    level of detail at which the original calculations are carried out. Wherever
                                    possible the methodology provides a "tiered" structure of calculations which
                                    describes and connects the various levels of detail at which national experts
                                    can work depending on the importance of the source category, availability of
                                    data, and other capabilities. All national experts are encouraged to work at
                                    the most detailed level which is possible and appropriate for their situation.
                                    The tiered structure ensures that estimates calculated at a very detailed
                                    level can be aggregated up to a common minimum level of detail for
                                    comparison with all other reporting countries.
                                    The methodology is by necessity broken down into segments and presented
                                    category by category. It is important to recognize some key linkages and
                                    interactions among components. For example, calculations in land use
                                    change and forestry methods (chapter 5), energy (chapter I) and agriculture
                                    (chapter 4) are  connected with one another through the calculation of
                                    emissions from  biomass as fuel. Several sub-categories  within the energy
                                    chapter make use of common data elements which must be consistent.
                                    There are many other such examples which are noted in the appropriate
                                    sections of the Manual.
                                    Reviewers and users of this document will recognize that a full scale final
                                    editing has not yet been completed. There are significant inconsistencies in
                                    formats and styles among the various chapters and sometimes  even within
                                    chapters. For example while most of the document uses footnotes, there
                                    are a few sections which provide notes at the end of the chapter or page.
                                    These editing problems will be corrected during the review process. The
                                    IPCC/OECD programme elected to place emphasis on completing the
                                    technical update and to produce a review draft quickly rather than
                                    correcting all of the appearance problems at the draft  stage.
                                    Another known problem of a more  technical nature is the inconsistency in
                                    treatment of full molecular weight of nitrogen oxides (NOX). Nitrogen
                                    oxides as emitted consist of NO and NO2. The convention among engineers
                                    working with emissions from industrial combustion is  to assume that all of
                                    the N is emitted as NO2. However, experts on emissions from biomass
                                     burning have generally adopted a different convention, assuming that all of
                                     the N is emitted as NO. In the document, both conventions are used in
                                     different sections, and noted in each case. The programme recognizes that
                                     this is an unsatisfactory  compromise, as a particular term or formula must
                                     have only one meaning in order to ensure comparability. This  problem will
                                     be corrected in the final IPCC Guidelines.
  INTRODUCTIONS

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                                                                                         INTRODUCTION
             Conclusion

             This Guidelines document draws on the input of expert groups and national
             experts from around the world. The methodologies presemted offer a
             recommended process for estimating and tracking national emissions
             inventories. Along with offering the best current methodologies for
             developing consistent national inventories, these Guidelines discuss
             weaknesses in the existing methodologies and identify technical areas where
             additional work is needed to develop better methods in the future.

             The chapters are divided by subject areas and correspond to the same
             subject chapters in the Workbook. This document should be used by national
             experts as a reference tool to accompany the Workbook and the Reporting
             Instructions when constructing and reporting national inventories of GHG
             emissions and removals.
             References

             OECD (1991) Estimation of Greenhouse Cos Emissions and Sinks, Final Report
             from the OECD Experts Meeting, 18-21 February 1991. The Organization for
             Economic Cooperation and Development, Paris. Revised August 1991.

             van Amstel, A.R., (ed.)  1993. Methane and Nitrous Oxide: Methods in National
             Emissions Inventories and Options for Control. Proceedings of an International IPCC
             Workshop, Amersfoort, NL 3-5 February 1993. RIVM Report no. 481507003.
             Bilthoven, NL. July.
PART  I
INTRODUCTION.5

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INTRODUCTION
                                   I        USING  THE  IPCC  GUIDELINES

                                  This document is one volume of the IPCC Guidelines for National
                                  Greenhouse Gas Inventories. The series consists of three books:

                                  •   THE GREENHOUSE GAS INVENTORY REPORTING INSTRUCTIONS

                                  •   THE GREENHOUSE GAS INVENTORY WORKBOOK

                                  •   THE GREENHOUSE GAS INVENTORY REFERENCE MANUAL
                                  These books together provide the range of information needed to plan,
                                  carry out and report results of a national inventory using the IPCC system.

                                  The Reporting Instructions (Volume I) provide step-by-step directions for
                                  assembling, documenting and transmitting completed national inventory data
                                  consistently, regardless of the method used to produce the estimates. These
                                   instructions are intended for all users of the IPCC Guidelines and provide
                                   the primary means of ensuring that all reports are consistent and
                                   comparable.
                                   The Workbook (Volume 2) contains suggestions about planning and getting
                                   started on a national inventory for participants who do not have a national
                                   inventory available already and are not experienced in producing such
                                   inventories. It also contains step-by-step instructions  for calculating
                                   emissions of carbon dioxide (CO2) and methane (CH4)  (also some other
                                   trace gases) from  six major emission source categories. It is intended to
                                   help experts in as many countries as possible to start developing inventories
                                   and become active participants in the IPCC/OECD programme.
                                   The Reference Manual (Volume 3) provides a compendium of information on
                                   methods for estimation of emissions for a broader range of greenhouse
                                   gases and a complete list of source types for each. It summarizes a range of
                                   possible methods for many source types. It also provides summaries of the
                                   scientific basis for the inventory methods recommended and gives extensive
                                   references to the technical literature. It is intended to help participants at all
                                   levels of experience to understand the processes which cause greenhouse
                                   gas emissions and the estimation methods used in compiling inventories.

                                   The three  books are designed to be used together and  include these
                                   features:
                                   •   all three volumes  use an identical arrangement and numbering by source
                                       category for ease of cross reference
                                   •   all the books have a common index which allows you to follow  up all
                                       references to a topic
                                       (The common index will be included in the final, approved version but
                                       not in the February 1994 review draft.)
                                   •   icons  in the margin of each book indicate the source category

                                   •   colour coding on the page indicates source category.

                                       (Colour will be included in the final, approved version but not in the
                                       February 1994 review draft.)
  INTRODUCTIONS

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                                                                                    INTRODUCTION

             Before  you  start...
            This diagram explains the stages needed to make a national inventory which
            meets IPCC standards.
                                       Do you have a detailed
                                        National inventory?
                                                                    Yes
                                                                           Aggregate/transform
                                                                            data and put into
                                                                            standard format
                                         Do you want to use
                                      IPCC Computer Software?
                                        Reporting
                                        recommendations
                                        - documentation
                                        - verification
                                        - uncertainty
                                        Ref. manual
                                       Final National Inventory
PART  I
INTRODUCTION.7

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INTRODUCTION

                                   The stages are:

                                   Question I
                                   Do you have a detailed national inventory?

                                   Answer: Yes
                                   If your country already has a complete national inventory, you should
                                   transform the data it contains into a form suitable for use by IPCC. This
                                   means transforming it into a standard format. In order to do this, use
                                   Volume I of the IPCC Guidelines, Reporting Instructions. This gives details of the
                                   way in which data should be reported and documented.

                                   Answer: No
                                   You should start to plan your inventory and assemble the data you will need
                                   to complete the Worksheets in this book. Refer to the Getting Started
                                   section of this Workbook.

                                   Question 2
                                   Do you want to use the IPCC computer software?

                                   Answer: Yes
                                   If you want to use the IPCC software, you will still follow the instructions
                                   are included in the Workbook to assemble the data you have collected into
                                   an inventory (see margin box). You will use the software instead of the
                                   printed worksheets to enter data.

                                   Answer: No
                                   If you do not use the IPCC software, use the Workbook and the Worksheets
                                   it contains to assemble the data you have collected into an  inventory.

                                   Finally...
                                   Inventory data should be returned to IPCC in the form recommended in the
                                   Reporting Instructions. It is important that,  where you have used a
                                   methodology other than the IPCC Default Methodology, it is properly
                                   documented. This will ensure that national inventories can  be aggregated
                                   and compared in a systematic way in order to produce a coherent regional
                                   and global picture.
                                    General  Notes  on  the  Guidelines

                                    I    The flow diagram above is intended as a simple schematic to illustrate
                                        the different types of users (working at different levels of inventory
                                        detail) and how they should be able to use the various volumes of the
                                        Guidelines. You should recognise that reality is more complex than this
                                        simplest explanatory chart. Many countries may have some parts of the
                                        inventory complete at a high level of detail but may only be getting
                                        started on other parts. It is quite likely that some users will need to do
                                        several iterations of the thinking process reflected in the diagram with
                                        regard to different parts of their inventory.

                                    2   Throughout the Guidelines there is an intentional double-counting of
                                        carbon released from human activities. On one hand, CC>2 is calculated
                                        based on the assumption that all of the carbon in original fuel, biomass,
 INTRODUCTIONS

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                                                                                            INTRODUCTION
                  soils etc. which oxidizes produces CC>2. For combustion sources,
                  however, methods are also provided to estimate portions of the original
                  carbon which are released as CH^ and CO. The prima.ry reason for
                  double counting this is that carbon is that carbon released as CH4 or
                  CO is eventually converted to COj in the atmosphere. This occurs in
                  less than IS years, which is short relative to the 100+ years lifetime of
                  CO2 in the atmosphere. Therefore carbon emitted as CH4 and CO can
                  have two effects. First, in the form initially emitted, and, second, as part
                  of long term COj accumulation in the atmosphere. In order to have a
                  very precise estimate of the actual emissions of carbon species for a
                  given year (i.e. as input to a complex atmospheric model) you should
                  subtract  carbon in reported CH^ and CO from CO2 to get net annual
                      emissions.
                  Many of the categories of greenhouse gas emissions and removals can
                  only be estimated with large ranges of uncertainty. Quite naturally,
                  some national experts have -developed methods which are designed to
                  produce ranges of estimates rather than point estimates for highly
                  uncertain categories.. The IPCC Guidelines, however, require that users
                  provide a single point estimate for each gas and emissions/removal
                  category. This is simply to make the task of compilation, comparison
                  and evaluation of national reports manageable. Users are encouraged to
                  provide uncertainty ranges or other statements of confidence or quality
                  along with the point estimates. The procedures for reporting
                  uncertainty information are discussed in the Greenhouse Gas Inventory
                  Reporting Instructions.
PART I
                                                                                            INTRODUCTIONS

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  PART 2
SECTORS

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               CHAPTER I
EMISSIONS FROM ENERGY
                           ENERGY

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                                                                             EMISSIONS FROM  ENERGY
                CHAPTER  I    EMISSIONS FROM  ENERGY
       I.I     Introduction

                This chapter discusses inventory methods for the energy sources of greenhouse gases,
                which include CO2, CH4, N2O, NOX, NMVOC and CO. Energy systems are extremely
                complex and pervasive components of national economies. The full range of greenhouse
                gases are emitted from a wide variety of different aspects of energy production,
                transformation handling and consumption activities. The various emissions from energy
                systems are organized in two main categories -  I) emissions from combustion, and 2) non-
                combustion, or "fugitive" emissions.
                In dealing with fuel combustion emissions, CO2 is discussed in a separate section because
                it can be calculated accurately at a highly aggregate level,  unlike other gases. CO2 emissions
                are primarily dependent on fuel properties. The IPCC reference method for CO2
                emissions from fuel combustion is a simple, accurate and internationally transparent
                approach which takes advantage of this fact. Non-CO2 greenhouse gases are more related
                to technology and combustion conditions, and hence, must be  estimated from detailed
                sectoral energy activity data.
                CO2 from energy activities can be estimated on a mass balance basis using information on
                the amount and carbon content of the fuels consumed. Primary energy data, with a few
                adjustments such as for non-oxidized products, serve as  the basis of the inventory
                calculation. Energy data on all commercial fuels are widely available from internationally-
                validated data bases for individual countries of the world. These data provide an accurate
                starting point for the estimation of CO2 inventories. However, since fuel qualities vary by
                region, so will emission factors. For global or regional estimations of CO2, these variations
                are slight enough that they will not significantly affect inventories. However, wide variation
                among the types of fuels consumed within the primary fuel categories from one nation to
                another will affect the accuracy of each national inventory. For example, certain countries
                may depend on lignite, whereas others will use only bituminous coals. As discussed later,
                the variation in emission factors within fuel categories can be as high as 10%. As a result,
                national energy data and appropriate emission factors should reflect the actual mix of fuel
                types within each country.
                Unlike CO2, national inventories of CH4, N2O, NOX, CO and NMVOCs all  require more
                detailed information. This is due to the dependence of non-CO2 emissions on several
                interrelated factors, including combustion conditions, technology, and control policies, as
                well  as fuel characteristics. These other gases cannot be estimated on the same mass
                balance basis as used for CO2, as the use of average emission factors for broad emission
                categories will introduce high levels  of uncertainty. Average emission factors can represent
                a wide distribution of values even across a single source" category or sub-category. CO2
                emissions can also be calculated at the more detailed level required for other gases. When
                national experts calculate other GHG emissions from energy combustion at a detailed
                level, they should use the same data to estimate CO2 at the more detailed level as well.
                Comparison and reconciliation of the aggregate and detailed CO2 emissions calculations
                can serve as a valuable verification process. Procedures for estimating CO2 at both levels
                of detail are discussed in this chapter. For all emissions estimates, the range of uncertainty
                should be stated to the extent feasible. Volume I: Reporting Instructions discusses
                approaches for estimating and expressing uncertainty.
                The non-CO2 gases from energy are discussed according to two major combustion source
                categories: stationary sources and mobile sources. The us;e of these two main categories
PART 2
                                                                                                                   1.5

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EMISSIONS FROM  ENERGY
                       is the most common method for the initial disaggregation of energy combustion activities. These
                       two categories also best represent differences in the types of service, which also captures
                       technology differences. A special section on traditional biomass fuels is included because they
                       may need to be treated with a somewhat different approach from other stationary combustion
                       sources. This is due to their dispersed nature and scarcity of data on this category.
                       Fugitive emissions are essentially intentional or unintentional releases of greenhouse gases
                       during production including from venting and flaring, processing transmission and storage of
                       fuels. The most significant greenhouse gas emissions in this category are methane emissions
                       from coal mining and from oil and gas systems. There are also emissions of other gases, such as
                       CO2 and NMVOC as fugitive or by-product emissions from energy systems.
                        I.I.I   Organization of  the Chapter

                       In addition to this introduction, this chapter is organized into six separate energy sections:

                       •   CO2 emissions from fossil fuels: CO2 emissions from all combustion sources are
                            estimated using an aggregate carbon balance approach to account for all carbon
                            across all energy categories.

                       •   Non-CO2 emissions from stationary sources:  Separated by common type of
                            service sector, and further by technology, estimation of non-CO2 emissions from
                            stationary source activities focuses  on large facilities for NOX and on the commercial
                            and residential sectors for CO and  VOC.
                       •   Non-COz emissions from burning of traditional biomass fuels:  A simplified
                            approach is provided because data are often inadequate for estimating emissions
                            from this category based on technology-specific emission factors. This approach is
                            designed to be used  with data obtainable in developing countries where traditional
                            fuels make up a large fraction of total energy use.

                       •   Non-CO2 emissions from mobile sources:  Mobile source activities are divided
                            by transport mode, vehicle type and size to characterize a diverse range of engine
                            types and their respective emission characteristics.

                       •   Fugitive emissions from coal production and handling activities: Emissions
                            are generated as a result of the production and handling of coal, primarily methane
                            emissions from coal  mining. Other  emissions of GHG from coal mine and waste fires,
                            are briefly discussed.

                       •   Fugitive emissions from oil and gas systems: Methane emissions from natural
                            gas flaring and venting, and from natural gas production, transmission and distribution
                            are the most important for this category. COZ emissions from venting and flaring are
                            included as are NMVOC emissions from production, processing and distribution of
                            oil and oil products.
              1.2    Emission  Factor  Data
                       Emissions of GHGs from fuel combustion and fuel supply activities are calculated by
                       multiplying levels of activity by emission factors. Emission factors are usually presented in
                       the form of mass of pollutant per unit of activity (e.g., g N2O/GJ). The most commonly
                       used activity measure for energy-related emissions is the amount of fuel combustion or,
                       where fugitive emissions are concerned, the amount of fuel produced or distributed. In
                       some cases other measures of activity are used, most notably in calculating emissions from
                       the transport sector.
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                                                                               EMISSIONS FROM ENERGY
                For CO2 emission factors are a function of fuel quality, but for all other gases emission
                factors are also related to other factors (e.g., combustion technology, combustion
                conditions, control technology). A number of international and national sources of energy
                and industry emission factors exist largely as a result of international and national analyses
                of alternative control policies for SOX, NOX and NMVOC, A few sources have also
                recently emerged on various other GHGs. The more detailed factors (for gases other than
                CO2) do not relate directly to national energy activity data described below, but require
                some additional information. The sources of emission factor data and procedures for
                making these linkages are discussed in the context of specific gases and source types, in
                the relevant sections which follow.
       1.3    Energy  Activity  Data

                Subject to the requirements outlined below and intended to ensure the comparability of
                country inventories, the IPCC approach to the calculation of emission inventories
                encourages the use of fuel statistics collected by an officially recognised, national body as
                this is usually the most appropriate and accessible activity data. In some countries,
                however, those charged with the task of compiling inventory information may not have
                ready access to the entire range of data available within their country and may wish to use
                data specially provided by their country to the international organisations whose policy
                functions require knowledge of energy  supply and use in the world.

                There are, currently, two main  sources of international energy statistics: the International
                Energy Agency of the Organization for  Economic Cooperation and Development
                (OECD/IEA), and the United Nations (UN). The primary energy data sources cited in this
                report include:

                •   From the OECD/IEA:  Energy Statistics and Balances for Non-OECD Countries
                     (OECD/IEA, I993a); Energy  Balances of OECD Countries (OECD/IEA, I993b); and
                     Energy Statistics (OECD/IEA, I993c).

                •   From the United Nations: Energy  Statistics Yearbook (UN, 1993).

                There is a substantial amount of overlap among  these two systems. The UN uses data
                supplied by the IEA for  the countries of the OECD, and the IEA starts  with the UN data
                for non-OECD countries when preparing its world energy data publication. While the UN
                data set starts with IEA data for OECD countries, in its book-form publications it reports
                slightly more detail by fuel. This is simply a preference for1 reporting, since all data points
                exist in the original IEA source  and are available in machine-readable format (i.e.,  magnetic
                tape or computer diskette).

                Another issue is the "official" nature of the statistics reported by each source. The UN
                data source represents  the official energy profile of both OECD countries (via the IEA
                source) and the rest of the world, via their own national  data collection and review
                procedures. Alternatively, the IEA begins with the UN data for non-OECD countries,
                compiles it in their format, and augments it with information not available to the UN, e.g.,
                data from oil companies and other energy industries provided to the IEA. These additions
                to the basic UN data are checked for internal consistency and against other sources of
                data for the country, and when discrepancies exist, experts are contacted in the country
PART 2
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EMISSIONS FROM ENERGY
                       for an opinion as to which data to use. Coverage of the nations of the world in the IEA
                       data is not complete.1
                        1.3.1  Comparability  of Reporting

                       In order to meet the objectives of the IPCC/OECD programme, inventories submitted by
                       parties to the agreement must be readily comparable. This requires a large measure of
                       commonality of definitions of activities and fuel product groups and the use of a reporting
                       discipline which makes evident the construction of the inventory from the activity data.
                       Specific guidelines for reporting have been prepared. In order to reduce the uncertainty
                       created by possibly different definitions, the IPCC methodology recommends the use of
                       those utilised by the IEA for the regular collection of energy data from OECD member
                       countries. The active cooperation between the UN Statistical Division (Mew York), the
                       'JNECE (Geneva), Eurostat and the IEA has ensured that there are now very few
                       differences between the definitions employed by these organisations for the collection of
                       their energy data. The IEA definitions may be found in Energy Balances of OECD Countries
                        1990-91.
                       The paragraphs above make clear that the reporting country, when constructing the
                       inventory, is entitled to use national data from local sources or the national data as
                       reported to the international organisations. If local data are used, this should be stated,
                       identified and the reasons for preferring it to those provided to the international
                       organisations discussed in the documentation accompanying the submission. The activity
                       data used should also be reported.
                       A group of experts convened recently to discuss in detail  the existing  internationally
                       compiled energy data bases and their use in estimating GHGs, primarily carbon dioxide.
                       This group included representatives of the two major data collection activities (UN and
                       IEA), the IPCC/OECD programme and a number of experts who have used or currently
                       are using these data for the purposes of estimating GHG emissions. The experts in  this
                       meeting confirmed that, of existing data sources, "the data bases of the UN Statistical
                        Division in New York and of the IEA are the most comprehensive and provide the basis
                       for others. There is good consistency between the UN data base, the IEA data base and
                        other data bases such as those of the UN-ECE and CEC (EUROSTAT data set)."

                       An important result of the experts' meeting, which led to the  IPCC methodology, was to
                        highlight the importance of careful and comprehensive reporting of national energy data in
                        relation to its use in GHG emissions  estimation and analysis. Experts recommended that
                        every effort be made to communicate to national agencies who provide energy data that
                        this data plays  a crucial role in international evaluation of national GHG emissions. It is
                        hoped that this awareness will provide an additional motivation for national energy  data
                        sources to allocate adequate effort to the development and reporting of energy data so
                        that comprehensive and high quality information will be available as input to GHG
                        assessments. This recommendation is being conveyed through traditional channels to
                        energy statistics sources and also reinforced through environmental channels such as  the
                        IPCC and INC.
                           1 Approximately 120 countries (of about 170 UN Member countries) are included in
                        the IEA data, but the countries it includes account for about 98% of worldwide energy
                        consumption and nearly all energy production.

                           2 This meeting was convened by the International Atomic Energy Agency (IAEA), and
                        detailed results are described in  IAEA. 1993.
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                                                                                EMISSIONS  FROM  ENERGY
                 Inconsistent reporting standards among both national and international energy data sets
                 can lead to differences that hinder comparison and comparable inventory development. At
                 least five aspects of energy data reporting need to be checked prior to using data for
                 greenhouse gas inventories:
                 •   Are energy data reported in terms of lower heat values (LHV) or higher heat values
                     (HHV)?3 Since most of the world uses lower heat values, the IPCC Guidelines use
                     lower heating values.
                 •   Are waste  or waste-derived fuels included if combusted for energy production?
                     These fuels should be accounted for in the IPCC methodology, but are included  with
                     biomass fuels.
                 •   Is non-energy fuel usage (if non-oxidized) accounted for?4
                 •   How are international bunker fuels for air and ship transport treated?5
                 •   Are non-commercial fuels, including wood and other biomass fuels, included?6
                 Given responses to these questions, several adjustments may need to  be made to the
                 energy data being used in order to formulate a complete inventory of greenhouse gases. If
                 published IEA data are being used the following corrections must be made:
                 I    Bunker fuels  and vegetal fuels (both commercially-traded and traditional or non-
                     commercial biomass fuels) need to be added  to each country of origin. The IEA has
                     some data  on commercially-traded vegetal fuels, but traditional biofuels consumption,
                     e.g., wood  collected for cooking by individuals, is typically not included in official
                     energy statistics.
                 2   Non-energy fuel use needs to be estimated and deducted from apparent energy
                     consumption.7  Adjustments also need to be  made for the portion of non-energy
                     uses that do  not oxidize.
                 3   Vegetal fuels  should be separated and added as a separate fuel group.
                      The IEA generally reports data in lower heat values. The; difference between the lower
                 and the higher heating value of a fuel is the heat of condensation of moisture in the fuel during
                 combustion. The lower heating value excludes this. The IEA assumes that lower heating values
                 are 5% lower than higher heating values for oil and coal and 10% lower for natural gas.

                     4 This is normally reported in primary energy requirements but is not combusted and
                 therefore does not contribute directly to greenhouse gas emissions.

                     5 Bunker fuels are combusted at sea and by airplanes and therefore should be included
                 in greenhouse gas estimations. The question is how to allocate emissions among nations or
                 regions. As discussed later, the Paris workshop recommended that emissions from bunker
                 fuels be estimated as a separate category under energy-related emissions, and that the
                 issue of how to allocate these emissions be addressed and agreed upon internationally in
                 follow-up efforts. Okken and Tiemersma (1984) provide an example of the contribution of
                 shipping bunker fuels to the Netherlands' CO2 budget.

                      While some of these fuels (such as wood) may be included in national or
                 international data sets, it is likely that they are underestimated due to poor record keeping
                 and lack of statistical information for non-commercial fuels..

                    7 IEA data on bunker fuels and non-energy fuel use represent only a partial accounting of
                 these activities and would need to be supplemented with outside information. Specifically, non-
                 energy natural gas products and aviation bunker fuels are not separated in the IEA statistics.
PART 2
                                                                                                                       1.9

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EMISSIONS FROM  ENERGY
                       These adjustments can be quite significant to the energy balance and hence to the
                       calculation of greenhouse gases. For example, in  1987 international bunker fuels for
                       shipping represented about 3 per cent of the global oil requirement, but in some countries
                       accounted for a much higher share. Non-commercial vegetal fuels in 1 987 are estimated to
                       represent less than 4% of total primary energy requirements (TPER) in the OECD and
                       CPE, but nearly 22% for Developing Countries. Non-energy use of fuel products
                       represented about 10% of the world oil TPER in  I987.8
              1.4    Carbon  Dioxide  Emissions from  Energy

                       In this section methodology for estimating CO2 emissions from energy is discussed.
                       Carbon dioxide (CO^ is the most common greenhouse gas produced by anthropogenic
                       activities, accounting for about 60% of the increase in radiative forcing since pre-industrial
                       times. (IPCC, 1 992) By far the largest source of CO2 emissions is from the oxidation of
                       carbon when fossil fuels are burned, which accounts for 70-90% of total anthropogenic
                       COj emissions. When fuels are burned, most carbon is emitted as CO2 immediately
                       during the combustion process. Some carbon is released as CO, CH4, or non-methane
                       hydrocarbons, which oxidize to CO2 in the atmosphere within a period from a few days to
                       10-11 years. The IPCC methodology accounts for all of the carbon from these emissions
                       in the total for CO2 emissions. The other carbon-containing gases are also estimated and
                       reported separately (see following sections for methodologies for estimating CH4, CO,
                       and non-methane VOCs).9
                       Fuel combustion is widely dispersed throughout most activities in national economies, and
                       assembly of a complete record of the quantities of each fuel type consumed in each "end
                       use" activity is a considerable task, which some countries have not yet completed.
                       Fortunately, it is possible to obtain an accurate estimate of national CO2 emissions by
                       accounting for the carbon in fuels supplied to the economy. The supply of fuels is simple
                       to record and is more likely to be available in many countries, than detailed end use
                       consumption statistics. For this reason, the IPCC Reference Approach for estimating
                       emissions of CO2 from fossil fuels is somewhat different than the approach used for other
                       greenhouse gases. For CO2 emissions depend mostly on the basic fuel characteristics
                       rather than on technology or emission controls (as with gases such as NOX or CO).

                       The Reference Approach requires a careful accounting of fossil fuel production by energy
                       type, carbon content of fossil fuels consumed, fossil  fuel consumption by type, and
                       production of products with long term carbon storage. In this respect the methodology
                       for estimating CO2 emissions represents more of a "top-down" approach compared to the
                       "bottom-up" approach recommended for the other  gases. This does not mean that a
                       "bottom-up" approach used for other gases cannot also be followed for estimating CO2
                           8 Also combustion of non-energy oil products, such as plastics or refuse-derived fuel,
                       may not be consistently counted in the energy statistics compared to other solid fuels, nor
                       would they be included in the base energy statistics if combusted without energy recovery.
                       No global estimate of their significance is available.

                           9 It is important to note, as discussed in the introduction to this document, that there
                       is an intentional double counting of carbon emitted from combustion. This format treats
                       the  non-CO2 gases as a subset of CO2 emissions and ensures that the  CO2  emission
                       estimates reported by each country  represent the entire amount of carbon that would
                       eventually be present in the atmosphere as CO2. The reasons for this double  counting are
                       discussed in the introduction.
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                                                                                 EMISSIONS FROM ENERGY
                 emissions. A method for estimating emissions with a "bottom-up" approach is briefly discussed
                 later in this section. It is recommended that national experts who do detailed estimates of
                 emissions of non-CO2 gases, should also apply CO2 emission factors at this detailed level. In all
                 cases, experts should estimate CO2 emissions from fuel combustion using the IPCC reference
                 method also. This method provides the basis for international comparison, and all national
                 estimates should be reconciled with the results of this approach.

                 For all calculations of CO2 emissions from fuel combustion, emissions are directly
                 related to the amount of fuel consumed and  the carbon content of the fuel. Coal
                 contains close to twice  the carbon of natural gas and roughly 25 per cent more than
                 crude oil per unit of useful energy. A number of complicating factors need to be
                 considered carefully:

                 •   Common Energy Units: There is considerable variation in the energy content by
                     weight of some fuels, especially coals. For comparison all energy data must first be
                     converted to common energy units (e.g., gigajoules) before emission factors (or
                     coefficients) are applied.

                 •   Variations in Fuel Carbon: For a given fuel type, even when quantified in energy
                     units, the carbon per unit of useful energy varies. For example, not all coal types
                     contain the same proportion of carbon. Generally speaking, the lower the quality of
                     the coal (such as sub-bituminous coal and lignite), the higher the carbon emission
                     factor (i.e., carbon per unit of energy).10  There are similar carbon differences among
                     the different types of liquids and gases.
                 •   Unoxidized Carbon: When energy is consumed not all of the carbon in the fuel
                     oxidizes to CO2. Incomplete oxidation occurs due to inefficiencies in the combustion
                     process that leave some of the carbon unburned or partially oxidized  as soot or ash.
                 •   Stored Carbon: Not all fuel supplied to an economy is burned for heat energy.
                     Some is used as a raw material (or feedstock) for manufacture of products such as
                     plastics, fertilizer, or in a non-energy use (e.g. bitumen for road construction,
                     lubricants). In  some cases, as in fertilizer production, the carbon from the fuels is
                     oxidized quickly to  CO2 once applied and exposed to air. In other cases, as in road
                     construction, the carbon is stored (or sequestered) in the product, sometimes for as
                     long as centuries. The amounts stored for long periods are called stored carbon (or
                     sequestered carbon), and should be deducted from the carbon emissions calculation.
                     Estimation of stored carbon requires data on fuel used as feedstock and/or quantities
                     of non-fuel energy products produced. The calculations are discussed within each of
                     the alternative approaches  presented in this section.

                  •  Bunker Fuels: Bunker fuels refer to quantities of fuels used for international marine or
                     aviation purposes. The IPCC methodology accounts for these fuels as part of the energy
                     balance of the country in which they were delivered to ships or aircraft Thus the CO2
                     emissions from combustion of those fuels would also appear in the country of delivery,
                     even though most of the actual emissions occur outside its boundaries. This is done to
                     ensure that all fuel use is accounted for in the methodology. However, for informational
                     purposes, the quantities and  types of fuels delivered for international bunker purposes
                     should be separately subtotaled.
                     10 The major  exception to this  relationship is  anthracite or  very hard  coal, which
                 typically has a higher carbon emission coefficient than bituminous coal.
PART 2
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EMISSIONS FROM  ENERGY
                       •    Biomass Fuels: Biomass fuels are included in the national energy and emissions
                            accounts for completeness, as an information item. These emissions should not be
                            included in the summation of national CO2 emissions from energy. If biomass is being
                            regrown at roughly the same rate as it is being harvested on an annual basis, die net
                            flux of CO2 to the atmosphere is zero. If energy use, or any other factor, is causing a
                            long term decline in the total carbon embodied in standing biomass (e.g. forests), this
                            net release of carbon should be evident in the calculation of CO2 emissions described
                            in the Land Use Change and Forestry chapter.
                       All of the above issues are addressed within each of the alternative approaches presented
                       in the remainder of this section.


                        1.4.1  Approaches  For Estimating CO2 Emissions

                       The conceptual approach for estimating CO2  emissions from energy consumption is well-
                       known and straightforward. The basic calculations can be characterized as six fundamental
                       steps that explicitly identify all of the factors necessary to measure CO2 emissions from
                       energy consumption:
                            Estimating consumption of fuels by fuel product type.
                            Converting fuel data to energy units (if necessary).
                            Selecting carbon emission factors for each fuel product type and total carbon
                            potentially released from use of the fuels.
                            Estimating the amount of carbon stored in products for long periods of time.
                            Accounting for carbon not oxidized during combustion.
                            Converting emissions as carbon to full molecular weight of CO2.
I

2
3

4
5
6
There are three basic approaches for estimating CO2 emissions discussed in this document
that vary primarily according to the level of detail at which these six steps are carried out.
The methods are:              . .
 I    The IPCC Reference Approach: Detailed Fuels. The Detailed Fuels approach is
     the basic methodology recommended by the IPCC and requires information on
     several different types of energy products. This approach is sometimes referred to as
     "top-down" estimation since a country only needs information on the quantities of
     fuels produced domestically, and flowing into and out of the country. Accounting for
     actual consumption of fuels at the sectoral or sub-national level is not required.
2    Detailed Technology Based Calculation: "Bottom-Up" Method. Most
     countries would ultimately like more detail on emissions of CO2 by energy using sub-
     sector than provided in the reference approach. This information is clearly necessary
     for evaluating policy options for reducing GHG emissions. In addition, if national
     experts are calculating emissions of non-CO2 GHGs from energy combustion, they
     are very likely working at a much finer level of energy use and technology detail. It is
     desirable to estimate CO2 emissions and other gases at the same levels of detail for
     consistency purposes. The basic calculations to estimate CO2 can be applied a very
     detailed level, including by sector and fuel types consumed in specific end-uses. This
     level of calculation is called  "bottom-up" because it is very data-intensive, requiring a
     substantial amount of information about national energy consumption patterns in
     each sector of a nation's economy. Some of the additional complexities which must
     be addressed at this level are discussed briefly at the end of this section. If national
     experts use this approach, it is recommended that they also use the IPCC reference
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                                                                                EMISSIONS  FROM  ENERGY
                      approach and reconcile any differences between results at the two levels of detail.
                      This can be a very useful verification exercise.

                      Aggregate Fuel Approach. The aggregate fuel approach only requires information
                      on the generic types of fossil fuels consumed in each country, specifically the
                      quantities of solid, liquid, and gaseous fossil fuels consumed, and the amount of
                      biomass consumed.  No further detail on fuel product types is used in this approach.
                      Since most countries have access to energy data that iis more detailed than these
                      general categories, this overly simplified approach is not recommended by the IPCC
                      unless the reference approach cannot be implemented. Discussion of this aggregate
                      fuels approach can be found in Annex A. As an alternative to the IPCC reference
                      approach, this level of detail still allows a country to estimate CO2 emitted, due to
                      consumption  of various types of fossil fuels, but at a very aggregate, and less accurate
                      level.
                 1.4.2  IPCC  Reference  Approach::  Detailed  Fuels

                 The Reference Approach is based on an accounting of the carbon in fuels supplied to the
                 economy. It involves the careful estimation of each country's production of fuels, imports
                 of fuels and refined products, exports of fuels and refined products, and changes in the
                 stock levels for these fuels and products within the country. It makes use of a simple
                 assumption: once carbon is brought into a national economy in fuel, it is either saved in
                 some way (e.g., in increases if fuel stocks,  stored in products, left unoxidized in ash) or it
                 must be released to the atmosphere. It is  not necessary to know exactly how the fuel was
                 used or what intermediate transformations it underwent in order to calculate the carbon
                 released.

                 Carbon accounting is based mainly on the totahsupply of primary fuels and the net
                 quantities of secondary fuels brought into a country. Using these values apparent
                 consumption (i.e., energy supply) can be estimated  Once apparent consumption is
                 estimated, subsequent steps account for carbon emission factors and other adjustments
                 for the stored carbon, fraction oxidized, and other complications discussed in the
                 introduction to this section.
                The first step of the IPCC Reference Approach is to estimate apparent consumption of
                fuels within the country. This requires a balance of primary fuels produced, plus imports,
                minus exports, and net changes in stocks, stock change."  In this way carbon is
                "transferred" into the country from energy production and imports (adjusted for stock
                changes) and transferred out of the country through exports. In this accounting system for
                fuels supplied it is important to distinguish between primary fuels (i.e., fuels which are found
                in nature such as coal, crude oil, natural gas), and secondary fuels or fuel products, such as
                gasoline and lubricants, which are derived from primary fuels.
                      This approach is similar to, but not as detailed as, standard energy balance
                accounting. Energy balances, by their nature, are an attempt to reconcile supply (apparent
                consumption) with observed consumption where all the end-use sectors are separately
                identified. The Reference Approach includes only the data necessary to account for carbon
                flows into and out of a country. Therefore, the level of detail needed for this approach to
                CO2 emissions estimation is not as great as for a complete national energy balance.
PART 2
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EMISSIONS FROM ENERGY
                       To calculate the supply of fuels to the country, the following data are required for each
                       fuel and inventory yean
                       •    the amounts of primary fuels produced (production of secondary fuels and fuel
                            products is excluded)
                       •    the amounts of primary and secondary fuels and fuel products imported

                       •    the amounts of primary and secondary fuels and fuel products exported

                       •    the net increases or decreases in stocks of fuels
                       Production data would be provided for the primary (untreated) fuels, including crude oil,
                       natural gas liquids (NGL), coking coal, steam coal, sub bituminous coal, lignite (brown
                       coal), peat, and natural gas. These production data would define the initial amount of
                       carbon available for consumption in a country from which CO2 emissions are generated.
                       To determine the net amount of carbon consumed, i.e., apparent consumption, any
                       exports of these fuels would be subtracted and any imports added. Adjustments for stock
                       changes are also needed. The apparent consumption of primary fuels is, therefore,
                       calculated as:
                                           Production + Imports - Exports - Stock Change.
                        An increase in stocks is a positive stock change. As this is subtracted in the equation, a
                        positive stock change results in a decrease in apparent consumption. A stock reduction is
                        a negative stock change which, when subtracted in the equation, causes an increase in
                        apparent consumption.
                        Flows of secondary fuels should be added to primary apparent consumption. The
                        production (or manufacture) of secondary fuels should be ignored in the calculations of
                        apparent consumption since the carbon in these fuels will already have been accounted for
                        in the supply of primary fuels from which they were derived (e.g.. the estimate for
                        apparent consumption of crude oil already contains the carbon from which gasoline would
                        be refined). However, information on production of some secondary fuel products is
                        required in a later step to adjust carbon stored in these products. Flows of secondary fuels
                        are calculated as:
                                                 Imports - Exports - Stock Change.
                         Note that this calculation can result in negative numbers for Apparent Consumption. This
                         is a perfectly acceptable result for the purposes of this calculation since it indicates a net
                         export or stock increase in the country when domestic Production is not considered.

                         This procedure, in effect, calculates the supply of primary fuels to a country, with
                         adjustments for net imports (imports-exports) and stock changes in secondary fuels.

                         Since carbon content typically varies by fuel type, data should  be reported for detailed
                         categories of fuel and product types as shown in Table I-I. The table also illustrates the
                         inputs and calculations recommended for the IPCC Reference Approach. The data are
                         specified in the form available in the OECD/IEA Energy Statistics (1993). As discussed
                         above, biomass fuels and bunker fuels have been included in the emission inventory
                         calculations for information only. These subtotals are not added to the totals calculated for
                         fuels above the line.
   1.14

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                                                       EMISSIONS FROM ENERGY
                                    TABLE l-l
                               IPCC REFERENCE APPROACH
                        ENTRIES AND CALCULATIONS FOR STEPS (I) AND (2)



Fuel
A) Liquid Fossil
Primary Fuels
1) Crude Oil
2) N.Gas Liquids
Secondary Fuels/Products
3) Gasoline
4) Kerosene
5) Jet Fuel NA
6) Gas/Diesel Oil
7) Residual Fuel Oil
8)LPG
9) Naphtha NA
10) Bitumen
1 1) Lubricants
12) Petroleum Coke
13) Refinery F-stocks
14) Other Oil
B) Solid Fossil
Primary Fuels
15) Coking Coal
16) Steam Coal
17) Lignite input
18) Sub-bit. Coal
19) Peat
Secondary Fuels
20) BKB & Patent Fuel
21) Coke
C) Gaseous Fossil
22) Nat. Gas(Dry)
Total
(1)

Produc
tion


input
input

NA
NA
input
NA
NA
NA
input
NA
NA
NA
NA
NA


input
input
input
input
input

NA
NA

input

(2)


Imports


input
input

Input
input
input
input
input
input
input
input
input
input
input
input


input
input
input
input
input

input
input

input

(3)


Exports


input
input

input
input
input
input
input
input
input
input
input
input
input
input


input
input
input
input
input

input
input

input

(4)

Stock
Change


input
input

input
input
calc
input
input
input
calc
input
input
input
input
input


input
input
calc
input
input

input
input
sumQ
input

(5)

Apparent
Cons.1
sumO2

calc
calc

calc
calc
input
calc .
calc
calc
input
calc
calc
calc
calc
calc
sumO

calc
calc
input4
calc
calc

calc
calc

calc
sumQ1
(6)

Conver.
Factor


input
input

input
input
calc
input
input
input
calc
input
input
input
input
input


input4
input4
calc
input4
input

input
input
surr>0
input

(7)
Apparent
Cons,
(GJ=IO*)
sumQ

calc
calc

calc
calc

calc
calc
calc

calc
calc
calc
calc
calc
sumQ

calc
calc

calc
calc

calc
calc

calc
sum()
Information Entries (Not Summed!
Biomass
23) Solid Biomass
24) Liquid Biomass

input
input

input
input

input
input

input
input
sumO
calc
calc

input
input
sumO
calc
calc
Bunkers - (Fuel Used for International Transport)
Total'
Jet Fuel Bunkers
Gas/Diesel Oil Bunkers
Resid. Fuel Oil Bunkers
"Other Oil" Bunkers

NA
NA
NA
NA

NA
NA
NA
NA

NA
NA
NA
NA

NA
NA
NA
NA
surnQ
input
input
input
input

input
input
input
input
sum()
calc
calc
calc
calc
PART 2
                                                                               1.15

-------
EMISSIONS FROM ENERGY
                                          TABLE l-l (CONTINUED)
                                        IPCC REFERENCE APPROACH
                                  ENTRIES AND CALCULATIONS FOR STEPS (3) - (6)




Eusl
A) Liquid Fossil
Primary Fuels
1) Crude Oil
2) N. Gas Liquids
Secondary Fuels/Products
3) Gasoline
4) Kerosene
S) Jet Fuel calc
6) Gas/Diesel Oil
7) Residual Fuel Oil
8)LPG
9) Naphtha
10) Bitumen
1 1) Lubricants
12) Petroleum Coke
13) Refinery F-stocks
14) Other Oil
B) Solid Fossil
Primary Fuels
IS) Coking Coal
16) Steam Coal
17) Ugnite
I8)Subbic.Coal
19) Peat
Secondary Fuels/Products
20) BKB & Pat. FueJ
21) Coke
Q Gaseous Fossil
22) Natural Gas (Dry)
Total7
Information Entries (Not S
Biomass Total
23) Solid Biomass
24) Liquid Biomass
(7)

Apparen
Cons
(GJ)
sumO

calc
calc

calc
calc
19.5
calc
calc
calc
calc
calc
calc
calc
calc
calc
sumQ

calc
calc
calc
calc
calc

calc
calc
sumO
calc
sumQ
ummed)
sum()
calc
calc
(8)
Carbon
Emission
Factor5
IK.% acn


20.0
15.2

18.9
19.5
calc
20.2
21.1
17.2
NA(20.0)
22.0
NA(20.0)
27.5
NA(20.0)
NA(20.0)
sumO

25.8
25.8
27.6
26.2
28.9

NA(25.8)
29.5

15.3



a«=t-.o
NA(20.0)
(9)

Potential
Emissions6
(GgQ
sumO

calc
calc

calc
calc

calc
calc
calc
calc
calc
calc
calc
calc
calc
sumQ

calc
calc
calc
calc
calc

calc
calc
sumO
calc
sum()

sumQ
calc
calc
(10) (II)
Net
Carbon Carbon
Stored Emissions
(GgQ (Gg CV
sumQ sumQ

calc
calc

calc
calc
calc calc
calc
calc
Table 1-4 calc
Table 1-4 calc
Table 1-4 calc
Table 1-4 rale
calc
calc
calc
sum() sum()

Table 1-4 calc
calc
calc
calc
calc

calc
calc
sumQ sum()
Table 1-4 calc
sum() sum()

sumQ
calc
calc
(12)
Adjusted
Carbon
Emissions
(Sg^
i;um()

calc
calc

calc
calc
calc
calc
calc
calc
calc
calc
calc
calc
calc
calc
sum()

calc
calc
calc
calc
calc

calc
calc
sum()
calc
sum()

sum()
calc
calc
Bunkers - (Fuel Use in international Transport)
Total
Jet Fuel Bunkers
Gas/Diesel Oil Bunkers
Resid. Fuel Oil Bunkers
Other Oil Bunkers 	
sumQ
calc
calc
calc
calc

19.5
20.2
21.1
NA(20.0)
sumO
calc
calc
calc
calc
sumQ
calc
calc
calc
calc
sumQ
calc
calc
calc
calc
(13)

CO2
Emissions
(Gg CO21
sumO

calc
calc

calc
calc

calc
calc
calc
calc
calc
calc
calc
calc
calc


calc
calc
calc
calc
calc

calc
calc
sumQ
calc
sum()

sumO
calc
calc

5>o
-------
                                                                                          EMISSIONS  FROM  ENERGY
                                                   TABLE l-l (CONTINUED)
                                                     EXPLANATORY NOTES

                  calc = value to be calculated,  NA = not applicable
                  1 Apparent Consumption equals production plus imports minus exports minus stock changes. Apparent
                  Consumption includes energy use for bunkers, although the subset of each category consumed as bunker fuels
                  should be calculated separately to allow for differential treatment at a later date.
                  2 Apparent Consumption for the aggregate categories of Liquid Fossil, Solid Fossil, Gaseous Fossil, and Biomass
                  Fuels equal the sum of Apparent Consumption over the fuel types within the appropriate categories.
                  3 Total should include Liquid, Solid, and Gaseous Fossil Fuel subtotals only. Biomass and Bunkers subtotals are
                  for informational purposes only, and should not be included in the totals,
                  4 If data is in lO'mt. separate conversion factors are available for Production, Imports, Exports, and Stock
                  Changes in Table 1-2. Each of these entries should be multiplied by the appropriate conversion factor. Then,
                  the results should be summed to find Apparent Consumption in GJ (Col. 7).
                  5 NA = Carbon Emission Factor (CEF) not available; value in parenthesis is a default value until a fuel-specific
                  CEF is determined. For oil products the default value is the emission for crude oil; for coal products the default
                  value is die emission factor for steam coal. All values taken from Grubb (1989), except LPG, which was taken
                  from Marland and Pippin (in press), and subbicuminous coal which was tsiken from Bowling (1989).
                   calc = calculation to be made by respondent; in this case, Consumption (column I) is multiplied by the
                  Carbon Emission Factor (column 2) and converted to Gg.
                  7 Total includes Liquid Fossil, Solid Fossil, and Gaseous Fossil subtotals only. Biomass emissions are not
                  considered "net" emissions, and bunker data is already included in the totals for the fuel types from which it is
                  derived. Separate biomass and bunker fuel totals are provided for information only.
                  Fuel statistics are needed on an energy basis (preferably in gigajoules; I gigajoule =  I09 joules) for
                  accurate estimation of CO2 emissions. In the OECD/IEA Energy Statistics, and in many other
                  energy data compilations, production and consumption of solid and liquid fuels are specified in
                  IO3 metric tons (I O3 mt). To convert metric tons to gigajoules, conversion factors must be
                  applied.  For unrefined fuels, energy content per tonne of fuel can vary widely from country to
                  country. Default conversion factors for a number of countries based on IEA energy data. These
                  values to convert from I O3 metric tons to gigajoules are in Tattle I -2. Note that in  many cases
                  different conversion factors are given for production, imports and exports in a given  country.
                  These can be used to convert each of these categories separately in die calculation of apparent
                  consumption. For stock changes national experts can use a weighted average of the different
                  conversion (actors, or use die one which represents die largest quantity of total apparent
                  consumption for that coal  type. For refined products die conversion factors from  I O3 metric
                  tons to gigajoules do not normally vary by country and global default values are provided in
                  Table  1-3.'*

                  National experts may use more detailed locally available conversion factors. In this case, die
                  conversion factors used should also be reported and documented. If original data are expressed
                  in odier energy units such as British thermal units (Btu's), million tons of oil equivalent (Mtoe),
                  diey should be converted to gigajoules using standard conversion factors. If energy data are
                  already available in gigajoules, no conversion is necessary and column 6 of Table l-l can be
                  ignored.
                      12 The IEA has agreed to provide die relevant energy statistics data, along with die
                   appropriate conversion {actors, to any interested countries ufion request The IEA will provide
                   data combining die fuel product detail found in die Energy Statistics (OECD/IEA, 1993)
                   publication with die common energy unit format found in die Energy Balances publication.
PART 2
1.17

-------
EMISSIONS  FROM ENERGY
                                                               TABLE 1-2
                                           1990  COUNTRY-SPECIFIC CONVERSION FACTORS
                                                        (Gigajoule per metric ton)
                                   Albania  Algeria  Angola  Argen-  Arme-  Azer-   Bahrain Bangla-   Bela-    Benin
                                                    Cabinda tina    nia     baijan           desh     russia.
                                                                                                                     Bolivia
           Oil
             Crude OH
                                     41.45
                                              43.29    42.75    42.29
                                                                              42.08    42.71
                                                                                              42.16
                                                                                                      42.08    42.S8   43.33
             NGL
                                              43.29
                                                              4Z50
                                                                                      42.71
                                                                                              42.71
                                                                                                                      43.33
            Coal
            Hard Coal
            Production
                                              25.75
                                                              24.70
            Imports
                                     27.21
                                              25.75
                                                              30.14    18.58    18.58
                                                                                              20.93
                                                                                                      25.54
            Exports
                                                              24.70    18.58    18.58
                                                                                                      25.54
            Brown Coal and Sub-Bituminous Coal
            Production
                                      9.84
            Imports
                                                                      14.65    14.65
                                                                                                       14.65
            Exports
                                      9.84
                                                                       14.65
                                                                              14.65
                                                                                                       14.65
            Coal Products
             Patent Fuel/BKB
                                                                      29.31
                                                                              29.31
                                                                                                       29.31
             Coke
                                     27.21
                                              27.21
                                                              28.46    25.12   25.12
                                                                                                       25.12
                                     Brazil   Brunei  Bulgaria  Came-   Chile   China   Colo-
                                                              roon                    mbia
Congo
Cuba  Cyprus   Czech
               Republic
            Oil
             Crude Oil
                                     4ZS4
                                              42.75    42.62    42.45   42.91    42.62    42.24
                                                                                              42.91
                                                                                                       41.16    42.48    41.78
             NGL
                                     45.22
                                              42.75
                                                                      42.87
                                                                                      41.87
            Coal
            Hard Coal
             Production
                                      18.42
                                                      24.70
                                                                      28.43   20.52   27.21
                                                                                                                       24.40
             Imports
                                      30.56
                                                      24.70
                                                                       28.43   20.52
                                                                                                       25.75    25.75    23.92
             Exports
                                                                              20.52   27.21
                                                                                                                       27.98
            Brown Coal and Sub-Bituminous Coal
             Production
                                                       7.03
                                                                       17.17
                                                                                                                       12.26
             Imports
             Exports
                                                                                                                       15.26
            Coal Products
             Patent Fuel/BKB
                                                       20.10
                                                                                                                       21.28
             Coke
                                      28.30
                                                       27.21
                                                                       28.43    28.47   20.10
                                                                                                       27.21
                                                                                                                       27.01
                          Crude oil conversion factors are based on weighted average production data.

                          The conversion factors are those used by the IEA In the construction of energy balances.

                          Source: OECD/IEA, 1993.
  1.18

-------
                                                                                     EMISSIONS FROM ENERGY
                                                     TABLE I-2 (CONTINUED)
                                          1990 COUNTRY-SPECIFIC CONVERSION FACTORS

                                                     (Gigajoule per metric ton)
                                Ecuador  Egypt   Estonia Ethiopia Gabon Georgia Ghana
                                       Guate-   Hong  Hungary  India
                                        mala    Kong
       Oil
        Crude Oil
                                 42.45     42.54
                                                          42.62    42.62    42.08    42.62    42.45
                                                                                                           40.36    42.79
        NGL
                                 42.45
                                          42.54
                                                                                                           45.18    43.00
       Coal
       Hard Coal
        Production
                                                                          18.58
                                                                                                            16.42    19.98
        Imports
                                          25.75
                                                  18.58
                                                                          18.58   25.75
                                                                                                   25.75    26.33    25.75
        Exports
                                                  18.58
                                                                          18.58
                                                                                                           24.15    19.98
       Brown Coal and Sub-Bituminous Coal
        Production
                                                  14.65
                                                                                                            10.55    9.80
        Imports
                                                  14.65
                                                                           14.65
                                                                                                            9.91
        Exports
                                                  14.65
                                                                           14.65
       Coal Products
         Patent Fuel/BKB
                                                  20.10
                                                                          29.31
                                                                                                            21.44    20.10
         Coke
                                          27.21
                                                  25.12
                                                                          25.12
                                                                                                   27.21     30.11
                                Indonesia  Iran
Iraq
Israel   Ivory  Jamaica Jordan
        Coast
Kazakh-
  stan
Kenya   Kuwait   Kyrgy-
                 zstan
        Oil
         Crude Oil
                                  42.66
                                          42.66    42.83    42.54    42.62   42.16   42.58    42.08
                                                                                                   42.08    42.54    42.08
         NGL
                                  42.77    42.54
                                                  42.83
                                                                                                            42.62
        Coal
        Hard Coal
        Production
                                  25.75    25.75
                                                                                           18.58
                                                                                                                     18.58
        Imports
                                  25.75
                                          25.75
                                                           26.63
                                                                           25.75
                                                                                           18.58
                                                                                                    25.75
                                                                                                                     18.58
        Exports
                                  25.75
                                                                                           18.58
                                                                                                                     18.58
        Brown Coal and Sub-Bituminous Coal
        Production
                                                                                           14.65
                                                                                                                     14.65
        Imports
                                                                                           14.65
                                                                                                                     14.65
        Exports
                                                                                           14.65
                                                                                                                     14.65
        Coal Products
         Patent Fuel/BKB
                                                                                           29.31
                                                                                                                     29.31
         Coke
                                27.21
                                                                                         25.12
                                                                                                                   25.12
                  Crude oil conversion factors are based on weighted average production data.

                  The conversion factors are those used by the IEA in the construction of energy balances.

                  Source: OECD/IEA. 1993.
PART  2
                                                                                                                              1.19

-------
EMISSIONS  FROM  ENERGY
                                                         TABLE I-2 (CONTINUED)
                                              1990  COUNTRY-SPECIFIC CONVERSION FACTORS

                                                         (Gigajoule per metric ton)
                                     Latvia
                                              Leb-
                                              anon
Libya
Lithu-  Malaysia  Malta  Mexico Moldava
 ania
Mor-   Mozam-
occo    bique
Myan-
 mar
           Oil
             Crude Oil
                                              42.16    43.00    42.08    42.71
                                                                                      42.35
                                                                                                      43.00
                                                                                                                      42.24
             NGU
                                                                      43.12
                                                                                      46.81
                                                                                                                      42.71
           Coal
            Hard Coal
            Production
                                                                      25.75
                                                                                      24.72
                                                                                                      23.45    25.75
                                                                                                                      25.75
            Imports
                                      18.58
                                                               18.59
                                                                      25.75    25.75    30.18
                                                                                              13.58
                                                                                                      27.63    25.75
                                                                                                                      25.75
            Exports
                                      18.58
                                                               18.59    25.75
                                                                                      22.41
                                                                                              13.58
            Brown      Coal     and
            Sub-Bituminous Coal
            Production
                                                                                                                       8.37
            Imports
                                      14.65
                                                               14.65
                                                                                              14.65
            Exports
                                      14.65
                                                               14.65
                                                                                              14.65
            Coal Products
             Patent Fuel/BKB
                                      29.31
                                                              29.31
                                                                                              29.31
Coke

25.12
Nepal
-
Neth.
Antilles
-
Neutral
Zone
25.12
Nigeria
27.21
North Oman
Korea
27.96
Paki-
stan
25.12
Panama
27.21
Para-
guay
27.21
Peru Philip-
pines
Oil
             Crude Oil
                                              42.16   42.12    42.75   42.16   42.71    42.87    42.16    42.54    42.75
                                                                                                                       42.58
             NGL
                                                                                                              42.75
            Coal
            Hard Coal
            Production
                                                               25.75    25.75
                                                                                      18.73
                                                                                                              29.31
                                                                                                                       20.10
            Imports
                                      25.12
                                                                       25.75
                                                                                      27.54    25.75
                                                                                                              29.31
                                                                                                                       20.52
            Exports
                                                               25.75    25.75
            Brown Coal and Sub-Bituminous Coal
            Production
                                                                       17.58
                                                                                                                       8.37
            Imports
            Exports
            Coal Products
             Patent Fuel/BKB
             Coke
                                                               27.21
                                                                       27.21
                                                                                                               27.21
                                                                                                                       27.21
                          Crude oil conversion factors are based on weighted average production data.

                          The conversion (actors are those used by the IEA in the construction of energy balances.

                          Source: OECD/IEA. 1993.
 1.20

-------
                                                                                      EMISSIONS  FROM  ENERGY
                                                  TABLE 1-2 (CONTINUED)
                                       1990 COUNTRY-SPECIFIC CONVERSION FACTORS

                                                  (Gigajoule per metric ton)

Poland Qatar
Romania Russia Saudi Senegal Sing- South South Slovak Sri
Arabia apore Africa Korea Republic Lanka

Oil
Crude Oil
NGL
41.27 42.87
43.00
40.65 42.08 42.54 42.62 42.71 44.13 42.71 41.78 42.16
42.62 ... ...
Coal
Hard Coal
Production
Imports
Exports
Brown Coal and
Production
Imports
Exports
22.95
29.41
25.09
Sub-Bituminous Coal
8.36
-
9.00
16.33 18.58 - - - 25.09 19.26
25.12 18.58 - 27.21 23.92 25.75
18.58 - - - 25.09

7.24 14.65 ..... 12.26
7.24 14.65 .... ...
14.65 ..... 15.26
Coal Products
Patent Fuel/BKB
Coke
20.93
27.76
14.65 29.31 ..... 21.28
20.81 25.12 - - 27.21 - - 27.01
                              Sudan    Syria   Taiwan  Tajik-   Tanz-   Thai-   Trini-  Tunisia
                                                        istan    ania    land    dad /
                                                                              Tobago
Turk-  Ukraine   Utd
meni-            Arab
 stan             Emir-
                 ates
    Oil
     Crude Oil
                              42.62
                                       42.04    41.41
                                                        42.08    42.62    42.62   42.24
                                                                                        43.12
                                                                                                42.08    42.08    42.62
     NGL
                                                                        46.85
                                                                                        43.12
    Coal
    Hard Coal
     Production
                                               25.96
                                                        18.58    25.75
                                                                                                        21.59
     Imports
                                               27.42
                                                        18.58
                                                                        26.38
                                                                                        25.75
                                                                                                18.58    25.54
     Exports
                                                        18.58
                                                                                                18.58    21.59
    Brown Coal and Sub-Bituminous Coal
     Production
                                                                        12.14
                                                                                                         14.65
     Imports
                                                        14.65
                                                                                                14.65
                                                                                                         14.65
     Exports
                                                        14.65
                                                                                                14.65
                                                                                                         14.65
    Coal Products
      Patent Fuel/BKB
                                                        29.31
                                                                                                29.31
                                                                                                         29.31
      Coke
                                                        25.12    27.21    27.21
                                                                                        27.21
                                                                                                25.12    25.12
                  Crude oil conversion factors are based on weighted average production data.

                  The conversion factors are those used by the IEA in the construction of energy balances.

                  Source: OECD/IEA, 1993.
PART  2
                              1.21

-------
EMISSIONS  FROM  ENERGY
                                                       TABLE 1-2 (CONTINUED)
                                            1990 COUNTRY-SPECIFIC CONVERSION FACTORS

                                                       (Gigajoule per metric ton)
                                          Uruguay  Uzbek-  Vcnez-
                                                    istan    uela
Viet   Yemen Former Zaire
Nam           Yugo-
               slavia
                                                                                                 Zambia
 Zim-
babwe
                   Oil
                    Crude OH
                                            42.71
                                                    42.08    42.06    42.61    43.00   42.75   42.16    42.16
                    NGL
                                                            41.99
                   Coal
                   Hard Coal
                   Production
                                                    18.58    25.75
                                                                    20.91
                                                                                   23.55    25.23    24.71
                                                                                                          25.75
                    Imports
                                                    18.58
                                                                                   30.69    25.23
                                                                                                          25.75
                    Exports
                                                    18.58    25.75
                                                                    20.91
                                                                                                  24.71
                                                                                                          25.75
                   Brown Coal and Sub-Bituminous Coal
                    Production
                                                                                    8.89
                    Imports
                                                    14.65
                                                                                    16.91
                    Exports
                                                    14.65
                                                                                    16.90
                   Coal Products
                    Patent Fuel/BKB
                                                    29.31
                                                                                   20.10    29.31
                    Coke
                                                    25.12    27.21
                                                                    27.21
                                                                                   26.90    27.21
                                                                                                          27.21
                        Crude oil conversion factors are based on weighted average production data.

                        The conversion factors are those used by the IEA in the construction of energy balances.

                         Source: OECD/IEA. 1993.
 1.22

-------
                                                                           EMISSIONS  FROM ENERGY
                                            TABLE I-2 (CONTINUED)
                                  1990 COUNTRY-SPECIFIC CONVERSION FACTORS
                                            (Gigajoule per metric ton)
Australia Austria Belgium
Canada
Den- Finland France
mark
Ger-
many
Greece Iceland Ireland Italy
Oil
Crude Oil
NGL
Refinery Feedst.
43.21 42.75 42.75
45.22 45.22
42.50 42.50 42.50
42.79
45.22
42.50
42.71 42.66 42,75
45.22
42.50 42.50 42.50
42.75
-
42.50
42.75 - 42.83 42.75
45.22 - - 45.22
42.50 - 42.50 42.50
Coal
Coking Coal
Production
Imports
Exports
28.34
28.00 29.31
28.21
28.78
27.55
28.78
28.91
34.33 30,50
-
28.96
28.96
28.96
.
27.44 29.10 30.97
.
Bituminous Coal and Anthracite
Production
Imports
Exports
24.39 - 25.00
28.00 25.00
25.65 - 25.00
28.78
27.55
28.78
26.71
26.09 26.38 25,52
26.09 - 26.43
24.96 ,
26.52
31.71
26.13 26.16
27.21 25,85 29.98 26.16
26.13
Sub-Bituminous Coal
Production
17.87 - 18.06
17.38
.
-
-
Imports - ........ ....
Exports
18.20
-
.
-
.
Brown Coal
Production
Imports
Exports
9.31 10.90
10.90 21.56
10.90
14.25
-
14.25
17.94
17.94
.
8.41
14.88
8.40
5.74 - - 10.47
19.82 10.47
.
Coal Products
Patent Fuel/BKB
Coke
21.00 19.30 23.81
25.65 28.20 29.31
-
27.39
18.27 - 28.80
31.84 28.89 28.71
20.64
28.65
15.28 - 20.98
29.30 26.65 32.66 29.30
                The conversion factors for oil and coal are those used by the IEA in the construction of energy balances.
                The conversion factors for coal product groupings listed are calculated from the conversion factors of their
                constituents.
                Source: OECD/IEA, 1993.
PART  2
1.23

-------
EMISSIONS  FROM  ENERGY
                                               TABLE 1-2 (CONTINUED)
                                      1990  COUNTRY-SPECIFIC CONVERSION FACTORS
                                               (Gigajoule per metric ton)
Japan
Luxem- Ncther-
bourg lands
NZ Norway Port- Spain Sweden Switzerl Turkey
ugal and
UK
USA

Oil
Crude Oil 42.62
NGL. 46.05
Refinery Feedjt. 4Z50
42.71
45.22
42.50
43.12 42.96 42.71 42.66 42.75 42.96 42.79
46.05 45.22 - 45.22
44.80 42.50 42.50 42.50 42.50 42.50 42.50
42.83
46.89
42.50
42.71
45.22
42.50
Coal
Coking Coal
Production 30.63
Imports 30.23
Exports
-
29.30
-
28.00 - - 29.16 - - 33.49
28.00 - 29.30 30.14 30.00 - 33.49
28.00 .... - -
29.27
30.07
29.27
29.68
:
29.68
Bituminous Coal and
Anthracite
Production 23.07
Imports 24.66
Exports
-
29.30 29.30
29.30
26.00 28.10 - 21.07 14.24 - 29.30
28.10 26.59 25.54 26.98 28.05 27.21
28.10 - 23.00 26.98 28.05
24.11
26.31
27.53
26.66
27.69
28.09
Sub-Bituminous Coal
Production
Imports
-
-
21.30 - 17.16 11.35
11.35
-
-
19.43
-
Exports • ~ ~ ~ "•"
Brown Coal
Production
Imports
Exports
-
20.03 20.00
20.00
14.10 - - 7.84 - - 9.63
8.37 - 12.56
-
-
-
-
14.19
-
14.19
Coal Products
Patent Futl/BKB 27.05
Coke 28.64
20.10 23.53
28.50 28.50
20.31 20.10 21.76 20.93
28.50 28.05 30.14 28.05 28.05 29.28
26.26
26.54
-
27.47
                      The conversion factors for coal product groupings listed are calculated from the conversion factors of their
                      constituents.
                      Source: OECD/IEA, 1993.
  1.24

-------
                                                                               EMISSIONS FROM ENERGY
TABLE 1-3
CONVERSION FACTORS FOR OTHER
PRODUCTS
Factors (GJ/IO tonnes)
'Refined Petroleum Products
Gasoline (aviation and auto)
Kerosene
Jet Fuel
Gas/Diesel Oil
Residual Fuel Oil
LPG
Naphtha
Bitumen
Lubricants
Petroleum Coke
Refinery Feedstocks
Other Oil Products
44800
447SO
44590
43330
40190
47310
45010
40190
40190
40190
44800
40190
Other Products
Coal Oils and Tars
                                       derived from Coking Coal
                                                                     28000
                 Source: OECD/IEA, Paris. 1993.
                 CO2 emission estimates also need to consider that the amount of carbon per unit of
                 energy varies considerably both among and within primary fuel types:

                 •   For natural gas, the carbon emission factor depends on the composition of the gas
                     which, in its delivered state, is primarily methane, but can include small quantities of
                     ethane, propane, butane, and heavier hydrocarbons. Natural Gas flared at the
                     production site will usually be "wet", i.e. containing far larger amounte of non-
                     methane hydrocarbons. The carbon emission factor will be correspondingly different

                 •   For crude oil, Marland and  Rotty (1984) suggest that the API gravity acts as an
                     indicator of the carbon/hydrogen ratio. Carbon content per unit of energy is usually
                     less for light refined products such as gasoline than for heavier products such as
                     residual fuel oil.

                 •   For coal, carbon emissions  per ton vary considerably depending on the coal's
                     composition of carbon, hydrogen, sulfur, ash, oxygen, and nitrogen. While variability
                     of carbon emissions on a mass basis can be considerable, carbon emissions per unit
                     of energy (e.g., per gigajoule) vary much less (with lower ranked coals such as
                     subbituminous and lignites usually containing slightly more carbon than higher-ranked
                     coals; anthracite is an exception since it typically contains more carbon than
                     bituminous coal).
PART 2
1.25

-------
EMISSIONS  FROM ENERGY
                                                            TABLE 1-4
                                  CARBON EMISSION COEFFICIENTS FOR FUELS FROM DIFFERENT STUDIES
                                                (kg C/gigajoule,"net" heating value basis)
Study
Marland &Rotty (1984)
Marland &Rppin( 1990)
Grubb (1989)
OECD (1991)
Study
Anthracite Bit. Coal Sub-Bit.
Coal
25.5'
25.4'
26.8' 25.8'
25.8'
Crude Oil Gasoline Kerosene Diesel/Gas-
Lignite Peat


27.6' 28.9'

Fuel Oils NaturalGas
                                                                                Oil
Marland&Rotty(l984)
Marland & Pippin (1990)
Grubb (1989)
OECD (1991)
2I.01
2I.01 I9.41
20.0 ' I8.91
20.0
IS.21
I9.41 I9.91 21.1 W I5.31
I9.51 20.01 21.1 ' IS.31
15.3

                         assuming a 5% difference in heating value for coal and oil, and 10% for natural gas. These percentage
                         adjustments are the IEA assumptions on how to convert from gross to net heating values.

                         Z Average value for all coal: sub-bituminous through anthracite.

                         3 Midpoint of range from 20.7 for light fuel oil (#4 fuel oil) to 21.6 for residual fuel oil (#6 fuel oil).
                        Estimates of carbon emission factors for fuels from several studies are summarized in
                        Table 1-4. The largest differences in emission factors between the studies occur with
                        bituminous coal and oil, although these differences are relatively minor.

                        One approach'for estimating the carbon emission factors was presented in Marland and
                        Rotty (1984). For natural gas, the carbon emission factor was based on die actual
                        composition of dry natural gas. They estimated the composition for natural gas from 19
                        countries based on sampling data and then calculated a weighted average global gas
                        composition, breaking the gas out into methane, ethane, propane, other hydrocarbons,
                        CO2, and other gases. The composition of the gas then determined both the heating value
                        of the gas and the carbon content. The carbon emission factor of the gas (kg C/gigajoule,
                        using gross "calorific" units13) was expressed using the following relationship:
                                             Cg = 13.708 + (0.0828 X IO'3) X (Hv - 37.234)
                        where C{ is the carbon emission factor of the gas in kg C/gigajoule (GJ) and Hv is the
                        heating value of the gas (heating value in "gross" calorific units, see OECD/IEA, I990b) in
                        kj/meter3. The coefficients of the equation (13.708.0.0828 X IO"3. and 37,234) were
                        estimated using regression analysis based on data from the 19 countries. The carbon
                        content of oil was estimated to be a function of the API gravity: using an estimate of
                        world average API gravity of 32.5° ± 2°, they estimated a composition of 85% ± 1% carbon.

                            13 Two ways are used to express the energy content of fuels: gross calorific value and
                        net calorific value, sometimes expressed as high heating value and low heating value. The
                        IPCC methodology requires that all energy data be expressed using net calorific (or lower
                        heating) value.
 1.26

-------
                                                                              EMISSIONS FROM ENERGY
                Converting this to units of carbon per gigajoule yielded an estimate of 21.0 kg C/GJ on a
                net heating value basis (assuming 42.62 gigajoules per tonne, higher heating value, as
                reported in Marland & Rotty, 1984). For coal, the literature suggested that the carbon
                content of coal was predominantly a function of the energy content and that the carbon
                content on a per ton coal-equivalent basis was around 74.6% + 2% (Marland and Rotty
                1984). The carbon emission factor was estimated to be 25.5 kg C/GJ.
                The approach used by M.J.Grubb (1989) to estimate carbon emission factors is very similar
                but based on more recent research. All carbon emission factors were originally reported
                on a "gross" heating value basis, but are converted here to a net heating value basis. He
                provides carbon factors for methane, ethane, propane, and butane and using data from
                Marland and Rotty (1984), he estimates an average emission factor for natural gas of 15.3
                kg C/Gj ±  1%. For oil and some refined petroleum products the estimates are based on
                data from the literature, as summarized in Table 1-4. The carbon emission factor of coal,
                excluding anthracite, was defined as:
                                             Cc = 32.15- (0.234 X Hv)
                where Cc is the carbon emission factor in kg C/GJ and H¥ is the heating value of the coal
                ("gross" calorific value) when the heating value is from 31 to 37 GJ/ton on a dry mineral
                matter free (dmf) basis. Anthracites fall outside this range and are estimated using a value
                of 26.8 kg C/GJ.

                Since the publication of the original OECD Background Document (OECD 1991),
                additional information has been made available on carbon emission factors. Key points
                from this new information are summarized below (all factors are in lower heating value):

                •    At an (PCC-sponsored workshop in October 1992 (IPCC/OECD, 1993),  experts
                     recommended several revised emission factors based on national inventory
                     submissions to the OECD:
                     Oven or Gas Coke
                     Natural Gas Liquids
                     Petroleum Coke
                     Refinery Gases
       29.5 kg C/GJ
       15.2 kg C/GJ
       27.5 kg C/GJ
       !8.2kgC/Gj
                     Wood
                     Blast Furnace Gas
                     Coke Oven Gas
                     Bitumen
14
                     29.9 kg C/GJ
                     66 kg C/GJ
                     13 kg C/GJ
                     22 kg C/GJ
Of the country submissions received by the IPCC/OIECD programme to date only
Canada has reported a specific emission factor for subbituminous coals. This was a
value of 27.1  kg C/GJ ()aques, 1992). Detailed analysis conducted in the United
States reported an average value of 26.2 kg C/GJ (USDOE/EIA, 1992). Based on these
two results, it appears that the value previously  recommended in OECD (1991)
should be lowered. Because the U.S. analysis is documented in a detailed report, and
                    14 This emission factor would only be  necessary if a bottom-up methodology were
                being used (e.g., see Approach #3).

                    15 This is the mid-point of a range of values.
PART 2
                                                                               1.27

-------
EMISSIONS FROM  ENERGY
                           U.S. production of subbituminous coals is much higher than in Canada, the new
                           recommended default value is 26.2 kg C/GJ.

                       •   A number of countries have provided emission factors for jet fuel including those
                           reported in IPCC/OECD (1993) and more recent reports. Based on a weighted
                           average of these values the recommended emission factor for jet fuel is 19.5 kg; C/GJ.

                       The IPCC Reference Approach relies primarily on the emission factors from Grubb
                       (1989), with additions from other studies as discussed above, to estimate total potential
                       carbon. The suggested carbon emission factors are listed in Step  3 of Table l-l, Column 8.
                       Table  l-l. Step 3, also provides the calculations needed to estimate the total carbon that
                       could  potentially be released from the use of fuels. The basic methodology is:
                                                    Total Carbon (Gg C) =
                                        Apparent Energy Consumption (by fuel type in GJ)
                               X Carbon emission factor (by fuel type in kg C/GJ), added across all fuel
                                                            types
                       Apparent consumption of the fuels is estimated in Step 2 of Table l-l (Column 7). The
                       carbon emission factors for the fuels are average values based on net calorific value (lower
                       heating value). As noted, this approach relies on carbon emission factors from Grubb
                       (1989), adjusted for net calorific value, plus factors recently available from other studies.
                       This approach has been recommended by the IPCC because it explicitly treats each major
                       fuel type differently according to its carbon emission factor. However, while carbon
                       emission factors are available for most fuel types, some gaps in the data still remain. It is
                       also possible that the default values provided here are not as accurate as country-specific
                       factors that may be available. To the extent that other assumptions are used, countries
                       should note the differences with the default values and provide documentation supporting
                       the values used in the national inventory calculations.


                       ESTIMATE CARBON  STORED  liji  pVoDUCTS   f      ~*
                                            *' ' NVw  <  t'^«   '  *t$t , ~*     rt-'n w,    s,      •  *?   •
                       After estimating the total carbon contained in the fuels, the next step is to estimate the
                       amount of carbon from these fuels that is stored (or sequestered) in non-energy  products
                       and the portion of this carbon expected to oxidize over a long time period (e.g., greater
                       than 20 years). All of the fossil fuels are used for non-energy purposes to some degree.
                       Natural gas is used for ammonia production. LPGs are used for a number of purposes,
                       including production of solvents and synthetic rubber. A wide variety of products are
                       produced from oil refineries, including asphalt, naphthas, and lubricants. Coal is used  to
                       produce coke; two by-products of the coking process include crude light oil and crude tar,
                       which are used in the chemical industry.
                       Not all non-energy uses of fossil fuels, however, result in the sequestering of carbon. For
                       example, the carbon from natural gas used in ammonia production is oxidized quickly.
                       Many products from the chemical and refining industries are burned or decompose within
                       a few years, while the carbon in coke is oxidized when used. Several approaches for
                       estimating the portion of carbon stored in products are reviewed in Box 2-1.
 1.28

-------
                                                                               EMISSIONS  FROM ENERGY
                                                     Box 2-1
                             Approaches for Estimating Carbon Stored in Products

                The approach used by Marland and Rotty (1984) relied on historical data for determining
                non-energy applications and varied depending on fossil fuel -type. For natural gas they
                assume that close to I /3 of the carbon used for non-energy purposes (equivalent to I % of
                total carbon from natural gas production) does not oxidize over long periods of time. For
                oil products they assume that some portion of LPG, ethane, naphthas, asphalt, and
                lubricants do not oxidize quickly. Specifically, they assume that about 50% of LPG and
                ethane from gas processing plants is sold for chemical and industrial uses and that 80% of
                this amount, or 40% of all LPG and ethane, goes into products that sequester the carbon.
                About 80% of the carbon in naphthas is assumed to end up in products such as plastics,
                tires, and fabrics and oxidize slowly. All of the carbon in asphalt is assumed to remain
                unoxidized for long periods, while about 50% of the carbon in lubricants is assumed to
                remained unoxidized. For coal they assume that on average 5.91% of coal going to coke
                plants ends up as light oil and crude tar, with 75% of the carbon in these products
                remaining unoxidized for long periods.

                M.J.Grubb (1989) basically uses the Marland and Rotty (1984) approach, but suggests
                several changes, including higher estimates of methane losses during production and
                transportation of natural gas to market and a wide range of estimates concerning the
                fraction of carbon in refinery products that remain unoxidized. He does use Marland and
                Rotty's estimate of the amount of carbon in coal that does not oxidize, but also quantifies
                the amount of carbon emissions from SO2 scrubbing (in which CO2 is released during the
                chemical interactions in the desulfurization process) using the formula: (% sulfur by
                weight) X (coal consumption) X 12/32.

                Okken  and Kram (1990) introduce the concept of actual and potential emissions of CO2
                where potential emissions are defined as carbon that is stored in products from non-
                energy  uses or by-products from combustion and actual emissions as all carbon from fuels
                that are emitted immediately or within a short period of time. Actual emissions plus
                potential emissions equal total carbon in the fuels. They assume that carbon from the
                following non-energy uses of fossil fuels oxidizes quickly: fertilizer production (ammonia),
                lubricants, detergents, volatile organic solvents, etc. Carbon from the following non-energy
                uses of fossil fuels remains stored for long periods of time (in some cases, hundreds of
                years): plastics, rubber, asphalt,  bitumen, formaldehyde, and silicium carbide.	

                For the IPCC Reference Approach, the suggested formula for estimating carbon stored in
                products for each country is:
                                               Total Carbon Stored =
                         (Non-energy Use, I03 mt) x (Conversion Factor, GJ/IO3 mt) x (Emission
                                                 Factor, kg C/GJ) x
                                             (% Stored), by product type
                 This approach is slightly revised from the original methodology in OECD (1991). The main
                 changes are converting all values to gigajoules rather than leaving all values in metric
                 tonnes and using an emission factor rather than an assumption for percent carbon
                 content. The resulting carbon estimates from non-energy uses would be considered
                 "potential" emissions, and are assigned to the country that produces the products. Most of
                 the suggested categories conform to those used by Marland and Rotty (1984) and include
                 naphthas, bitumen (asphalt), lubricants, LPG, and crude lighi: oil and crude tar. The data
                 available from the UN reports (e.g., 1990) correspond to these categories, with the
                 exception of crude light oil and tar, which is not reported.
PART 2
1.29

-------
EMISSIONS FROM ENERGY
                       In addition, recent information has suggested some other modifications to the approach
                       originally proposed in OECD (1991). These recommended modifications include:

                       •    Naphtha will be stored when used as a feedstock in the petrochemical industry.
                            However, in many countries naphtha is not always  used as a feedstock. As the
                            original methodology was based on total consumption of naphtha and not just that
                            portion intended for use as a feedstock, it has been recommended that the
                            methodology be changed to include only naphtha used as a feedstock. Furthermore,
                            available evidence from Western European countries indicates that approximately
                            75% of naphtha used as feedstock is transformed into intermediate products in the
                            petrochemical industry. The value of 75% is slightly lower than the 80% value
                            originally assumed, which was based on U.S. information only.

                       •    Gas/Diesel oil may also be used as a feedstock. This category was not included
                            originally in the methodology, but is added here. Evidence from Western European
                            countries indicates that about 50% of gas/diesel oil  used as feedstock is transformed
                            into intermediate products in the petrochemical industry.

                       The assumptions of 75% for naphtha as a feedstock and  50% for gas/diesel oil as a
                       feedstock should be viewed as potential overestimates since not all of the carbon from the
                       intermediate products will be stored. For example, carbon emissions may occur due to
                       losses in the production of final products or incineration of final products. At this time
                       these percentages can be used as the upper bound when determining stored carbon.
                       This suggested approach for estimating carbon stored in products is illustrated in Table I-
                       5. Whenever possible, countries should substitute assumptions that are more
                       representative of practices  within their own countries and provide documentation for
                       these assumptions. The resulting estimates from Table I -5 (Column 7) should be
                       subtracted from potential emissions to determine net emissions of carbon that could  be
                       oxidized. This calculation is done by entering the values  from  Table 1-5 (Column 7) for the
                       relevant fuels/products into Table I-I (Column 11). In Table I-1, carbon  stored in
                       products is subtracted from total carbon in the fuels to  get net carbon emissions.
 1.30

-------
                                                                                 EMISSIONS  FROM ENERGY
                                                     TABLE 1-5
                                     ESTIMATION OF CARBON STORED IN PRODUCTS
                                       I         234567
                                   Estimated  Conversion    Fuel     Emission   Estimated   Potential   Percent
                                     Fuel      Factor   Quantities Coefficient   Carbon    Carbon    Carbon
                                   Quantities                                Stored    Stored    Stored
Product/Fuel
Lubricants
Bitumen
Coal Oils and Tars from
Coking Coal
Naphtha as Feedstock
Gas/Diesel Oil
(Original
Units)
catc2
ca!c
calc
calc
calc
GJ/Units
Table 1-3
Table 1-3
Table 1-3
Table 1-3
Table 1-3
(GJ)
calc3
calc
calc
calc
calc
(Kg/GJ)
Table l-l
Table l-l
Table l-l6
Table l-l
Table l-l
(Gg)
calc4
calc
calc
calc
calc
(%)
50%
100
75
75
50
(Gg)
calc5
calc
calc
calc
calc
as Feedstock
Gas as Feedstock
LPG as Feedstock
calc
calc
Table 1-3
Table 1-3
calc
calc
Table l-l
Table l-l
calc
calc
33
80
calc
calc
                 This is only a partial list of products/fuels which accounts for the majority of carbon stored. Where data is
               available for other fuels, the estimation of stored carbon is strongly encouraged.
                 Production plus Imports minus Exports minus Stock Change, or Feedstock Use.
                 Apparent Consumption (Col. 3) equals Apparent Consumption (Col. I) times a Conversion Factor (Col. 2).
               4 Potential Carbon Stored (Col. 5) equals Apparent Consumption (Col. 3) times an Emission Coefficient (Col. 4).
               4 Carbon Stored (Cot. 7) equals Potential Carbon Stored (Col. 5) times Actual Percent Carbon Stored (Col. 6).

               6 Use the emission coefficient for coking coal (25.8 Kg C/GJ)

                 ESTIMATE CARBON  OXIDIZED  FROM  ENERGY  USES

                 As described earlier, not all carbon is oxidized during the combustion of fossil fuels. The
                 amount of carbon that fells into this category is usually a small fraction of total carbon, and
                 a large portion of this carbon oxidizes in the atmosphere shortly after combustion. Based
                 on work by Marland and Rotty  (1984), the IPCC has been recommending that 1% of the
                 carbon in fossil fuels would remain unoxidized. This assumption was based on the
                 following findings from Marland and Rotty for the amount unoxidized:

                 •   For natural gas less than 1% of the carbon in natural gas is unoxidized during
                     combustion and remains as soot in the burner, stack, or in the environment.

                 •   For oil  1.5% ±1% passes through the burners and is deposited in the environment
                     without being oxidized. This estimate is based on 1976 U.S. statistics of emissions of
                     hydrocarbons and total suspended particulates.

                 •   For coal 1% ±1% of carbon supplied to furnaces is discharged unoxidized, primarily in
                     the ash.

                 However, several countries have commented that the amount of carbon remaining
                 unoxidized is more variable than indicated by the 1% assumption across all fuels. For
                 example, it has been noted that the amount of unburnt carbon varies depending on several
                 factors, including type of fuel  consumed, type of combustion technology, age of the
                 equipment, and operation and maintenance practices, among other factors.
PART 2
1.31

-------
EMISSIONS FROM ENERGY
                       Information submitted by the Coal Industry Advisory Board of the OECD (Summers
                       1993), provided the following observations for coal combustion technologies:

                       •    Unoxidized carbon from electric power stations in Australia averaged about 1%. Test
                            results from stoker-fired industrial boilers, however, were higher, with unoxidized
                            carbon amounting to 1% to 12% of total carbon with coals containing from 8-23%
                            ash. As average values, 2% carbon loss was suggested for best practices, 5% carbon
                            loss for average practices, and 10% carbon loss for worst practices. In those cases
                            when coal is used in the commercial or residential sectors, carbon losses would be
                            on the order of 5-10% (Summers,  1993).
                       •    In related work British Coal has provided information on the percentage of unburnt
                            carbon for different coal combustion technologies:
                            Pulverised Coal

                            Travelling Grate Stoker

                            Underfeed Stoker

                            Domestic Open Fire

                            Shallow Bed AFBC
                            PFBC/CFBC
1.6%

2.7-5.4%

4.0-6.6%

0.6-1.2%

Up to 4.0%

3.0%
                        •    Evaluations at natural gas-fired boiler installations indicate that combustion efficiency
                            is often 99.9% at units reasonably well-maintained.

                        It is clear from the available information that a single global default assumption of I %
                        unoxidized carbon is not always accurate. While some additional information is available to
                        refine the assumptions for this portion of the methodology, most of the new information
                        requires some level of detail on the type of technology in which the fuel is combusted or
                        information on which sector is consuming the fuel. For this approach, the methodology
                        only requires data on the amount of fuels consumed in a country, not data by technology
                        type or sector'of the economy. As a result, based on the information available at this
                        point, the default values presented in Table 1-6 are recommended for the percentage of
                        unoxidized during combustion by fuel. It should be recognized that the value for coal is
                        highly variable based .on fuel quality and technology types. National experts are encouraged
                        to vary this assumption if they have data on these factors which indicates that different
                        average values for their countries are appropriate. It is clear from the information available
                        at this time that additional research should be conducted on this topic.
                                                           TABLE 1-6
                                                    CARBON OXIDIZED DURING
                                                          COMBUSTION
                                                     RECOMMENDED DEFAULT
                                                          ASSUMPTIONS
                                                                        percent
                                                       Liquid Fuels
                                                                         99%
                                                       Solid Fuels

                                                      Gaseous Fuels
                  98%

                  99.5%
 1.32

-------
                                                                              EMISSIONS FROM  ENERGY
                Net carbon emissions (column  12 in Table I-1) are then multiplied by the fraction of
                carbon oxidized (column 13 of Table I-I), and then summed across all fuel types, to
                determine the total amount of carbon oxidized from the combustion of the fuel. Next, to
                express the results as Carbon Dioxide (CO2), there is one more step. Total carbon
                oxidized should be multiplied by the molecular weight ratio of CO2 to C (44112) to find
                total carbon dioxide emitted from fuel combustion.
                1.4.3  Detailed  Technology  Based Calculations

                This section briefly discusses procedures already used by some countries for estimating
                CO2 emissions from fuel consumption at a more detailed and data-intensive level. This is a
                "bottom-up" approach in that emissions are estimated by sector of economic activity
                and/or by type of technology in which the fuel is consumed. The results for a wide range
                of "end-uses" and transformation activities must be summed to arrive at total national
                emissions. This discussion does not represent step by step guidance, but rather an initial
                conceptual discussion, that raises some issues which should be considered.

                A greater level of detail than is provided by the IPCC Reference Approach may ultimately
                be needed by most, if not all, countries participating in international climate change
                discussions. Such detail is important for analysis of policy options for reducing emissions,
                which are frequently related to specific end uses rather than aggregate fuel use. As
                discussed in the  next three sections, a more detailed approach is needed to credibly
                estimate emissions of several non-CO2 greenhouse gases from energy combustion.
                Countries which have developed detailed energy and technology data for calculating
                emissions of NOX, CO, etc., will very likely want to ensure that CO2 emissions estimates
                are consistent and comparable. For this reason many countries may wish to utilize a
                detailed approach for CO2 along with their detailed calculations for other GHG's from
                energy. This current discussion is intended to assist those\countries which are trying to
                build CO2 estimates into their existing detailed calculation procedures by indentifying
                some of the calculation issues which will have to be'resolved.
                This very detailed technology based approach does not provide a completely satisfactory
                result for two reasons. First it is extremely data intensive and may not be possible for the
                full range of IPCC countries in a reasonable time horizon. Second, even the most detailed
                technology based estimates produced in some countries, do not always carry with them
                the data necessary to conect emissions with economic subsectors of interest. In the
                future, the IPCC/OECD programme plans to provide more detailed guidance on practical
                application of a more detailed sectoral approach which will be less detailed than the
                technology based estimates but will still provide emissions broken down by economic
                sectors and sub-sectors of concern.
                The detailed technology based calculations should be essentially the same as those carried
                out in the Reference Approach, but should be carried out at a finer level of resolution.
PART 2
                                                                                                                   1.33

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EMISSIONS FROM  ENERGY
                       The formula is:
                               fuel consumption (actual now rather than apparent) expressed in energy
                              units (GJ) at the level of transformation or end use sub-sector and possibly
                                                  by specific technology/process
                                                    x carbon emission factor
                                                       x fraction oxidized
                       Stored carbon would be calculated as is done in the reference approach although this, too,
                       may be done at a finer level of product/process detail.
                       These steps are also conceptually quite similar to the calculations used to estimate
                       emissions other than CO2 from stationary and mobile source combustion. The
                       methodologies for estimating emissions from these sources are discussed in detail in the
                       following three sections. The Reference Approach for CO2 only requires data by fuel type
                       at the national level, but for the detailed calculations, national experts would be required
                       to provide data on energy consumption patterns at a much greater level of detail. Once
                       countries have obtained the activity data required for estimating detailed "bottom-up"
                       inventories of NOX, CO, etc., from combustion in stationary and mobile sources (i.e., fuel
                       consumption data by sector by technology type), CO2 emissions can also be estimated as
                       part of the inventory estimates for these other gases. The amount of fuel consumed for
                       each disaggregated category can be multiplied by an  appropriate emissions factor to
                       determine potential carbon emissions from fuel combustion. The fraction oxidized must
                       also be accounted for each category.
                       There are some important complexities which must be recognized in working from the
                       "bottom-up". Theoretically, it should make no difference in a country's total CO2 emission
                       estimate if the Detailed Technology Based Approach or the Reference Approach  is applied
                       since the amount of fuel consumed, and hence the amount of carbon oxidized, should be
                       the same with both approaches. Differences may result, however, if the source activity
                       data or emission factor data are not the same between the two approaches. These
                       differences could be the result oft

                       •   Actual differences may be due to better estimation methods with one approach (e.g.,
                            a country may choose alternative emission coefficients using the Detailed Technology
                            Based Approach that are thought to more closely represent fuel qualities for a
                            particular application)
                       •   Statistical inconsistencies may exist between two different data sets (e.g., estimates of
                            national coal consumption do not match).

                       •   A special problem may be in accurately accounting for losses of carbon in
                            transformation processes (as discussed below).
                       •   Stored carbon (or non-fuel use) should be accounted for in much the same way as in
                            the reference approach. However, this may produce somewhat different results if
                            carried out at a finer level of detail.

                       The most important value of the Reference  Approach is that it provides a simple,
                       transparent and verifiable means of accounting for all of the carbon  in fuels which could
                       potentially be  emitted to the atmosphere. Because of all of the above complexities, and
                       others, it may not always be the case that adding up the fuel used from detailed data sets
                       will account for all of the carbon in original fuels. For this reason, countries calculating
                       their emissions at the Detailed Technology Based level should cross-check their emission
                       estimates by also using the Reference Approach for verification, and reconcile any major
                       differences.
 1.34

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                                                                              EMISSIONS FROM ENERGY
               Some of these difficulties at the detailed technology based level are discussed conceptually
               below related to specific aspects of the calculations. If national experts have or are
               developing detailed inventories of other gases they are encouraged to incorporate CO2
               estimates in this process as well. Experts should read through the stationary combustion
               and mobile combustion sections  and should incorporate as much of the CO2 estimation as
               possible in the same calculations. The emission factors necessary to apply the Detailed
               Technology Based Approach for COZ emissions are repeated in the relevant sections.
               In this approach countries would estimate fuel consumption for at least the same fuel
               categories specified for the Reference Approach. A few additional fuel types such as Blast
               Furnace Gas and Refinery Gas may need to be added to account for all of the fuels in the
               form of their end use. The concept of "apparent consumption" used in the Reference
               Approach allows users to ignore some of the details in fuel transformations. For example,
               while we know that in fact crude oil is not actually consumed as an end use fuel, we also
               know that all the carbon in the original crude oil is emitted to the atmosphere unless a) it
               is converted to a non-fuel product (stored carbon), or b) it is incompletely oxidized and
               remains as ash at a combustion or transformation step.
               When working at the detailed level, countries would estimate actual fuel consumption for
               these fuel categories rather than apparent consumption. Moreover, rather than
               determining total national fuel consumption for these categories, a country would need to
               determine the amount of fuel consumed in each sector in order to estimate emissions for
               each sector of the economy. It may be necessary to account for actual consumption of
               specific fuels  in various end  use subcategories, further broken down by specific processes
               and technologies. Then one needs to work backwards to arrive at the total amounts of
               fuel carbon supplied to an economy.
               A major area of difficulty in this process is accounting for the carbon released in
               transformation of energy from one form to another. The largest emissions from the
               energy transformation sub-sector are associated with electric power generation, in which
               fossil fuels are converted into electricity. These emissions are treated exactly like end use
               fuel combustion emissions in most detailed inventories so this component should be
                relatively straightforward.
                Other transformations such as the refining of crude oil into oil products and the
                production of coke from coal can be more complicated and may be difficult to fully
                account for in the "bottom-up" approach. A simple input-output analysis may be helpful in
                accounting for the carbon releases during transformation si:eps.  For example, a refinery
                (or for all refineries of a specific type) is a complex set of processes, but can be considered
                as a single box. Total carbon in the form of crude oil (and possibly other input energy
                forms) can be estimated. Total carbon out of the box in the form of secondary fuels or
                fuel products can  be estimated. Any carbon disposed of in die form of wastes (such as
                ash), which represent stable long term storage, can be estimated. Any carbon not
                accounted for  in one of these output forms must be assumed to have oxidized as a result
                of the transformation process.
                Primary fuels that are not combusted directly, would thus not appear in end use
                combustion, although they may be considered as input to the input-output analysis of
                transformation Steps. In both transformation and in some end use applications, the
                detailed technology based level will require explicit accounting of some intermediate
                products -e.g., blast furnace gas, refinery gas - which can be ignored in the Reference
PART 2
                                                                                                                    1.35

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EMISSIONS  FROM  ENERGY
                       Approach. At a minimum it is recommended that countries using the Detailed Technology
                       Based Approach report emissions by the major fuel-consuming sectors defined in Volume
                       /: Reporting Instruction.

                           •Energy and Transformation Industries
                            —*r
                            •   Industry
                            •   Transport
                            •   Commercial/Institutional
                            •   Residential
                            •   Agriculture/Forestry
                            •   Other
                            •   Biomass Burned for Energy (Unallocated to any of the other sectors listed
                                above)
                       Within each consuming sector emission estimates could also be developed according to
                       the technology type in which the fuel was consumed. The following sections on stationary
                       and mobile source combustion list possible technology source categories that could be
                       estimated. Additional work needs to be done to further define a comprehensive set of
                       appropriate categories.
                       This is handled exactly as in the Reference Approach. Wherever detailed fuel consumption
                       data are collected in original physical units such as  I03 mt or other energy units such as
                       tons of oil equivalent (toe), they should be converted to gigajoules (GJ) using the same
                       conversion procedures discussed  in the Reference Approach.

                      l»aKs»PTA:x;H'-'':/:%, j,,;yv.v;^J.%5Ssa^a|3M^^^                               •,•-•'•.•-iS(j:,v*is-«;»,T:
                      |^lft£&&,Nl;.!£jM;iy5;§^
                       Once fuel consumption data are provided in GJ for the relevant sectors and/or technology
                       types, these consumption estimates can be multiplied by the appropriate carbon emission
                       factors to determine potential carbon emissions in kilograms (kg). The default carbon
                       factors are the same as those used in the Reference Approach since the carbon content of
                       specific fuel types does not change by sector or technology application. For example, if
                       bituminous coal is used in an industrial boiler, a country could use the same emission
                       factor for bituminous coal it would select under the Reference Approach. This does not
                       mean that a country may not vary the emission factor from one application to another if it
                       has reason to believe that the fuel qualities may differ. For example, if it is known that
                       bituminous coal consumed in the industrial sector has significantly different fuel qualities
                       than the average bituminous coal consumed in the country, then a country may wish to
                       specify an alternative emission factor. Unless such information is available, however, the
                       default emission factors used in the Reference Approach are acceptable.

                       These factors are provided again in the following sections on stationary and mobile source
                       combustion. In some cases the factors are also converted to different forms (e.g. kg total
                       COj/GJ, g CO2/km) where these are more appropriate for specific end uses. Countries
                       using alternative emission factors should note these differences and report the reasons for
                       using an alternative factor.

                       As in the IPCC Reference Approach, bunker fuel and biomass fuel and CO2 subtotals are
                       for informational purposes only, and should not be added to overall totals. They should be
                       shown as separate information totals when reporting.
1.36

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                                                                              EMISSIONS FROM ENERGY
               As discussed above under the Reference Approach, the amount of carbon that may remain
               unoxidized from combustion activities can vary for many reasons, including type of fuel
               consumed, type of combustion technology, age of the equipment, and operation and
               maintenance practices, among other factors. Since the Detailed Technology Based
               Approach relies on fuel consumption data on a more disaggregated level, it is possible to
               specify the assumptions for unoxidized carbon by application. Unless other data are
               available, as default values countries should use the assumptions recommended in the
               Reference Approach: 2% of carbon in fuel consumed is unoxidized for coal, 1% for oil-
               derived fuels and 0.5% for natural gas. In addition, the following assumptions (from
               Summers, 1993) are recommended:
               •   For stoker-fired industrial boilers an average value for carbon unoxidized is 5%. If
                    countries believe that their operation and maintenance procedures achieve maximum
                    efficiency, a 2% carbon loss is suggested. If these procedures are believed to lead to
                    very poor efficiency, then a 10% carbon loss is recommended.
               •   In those cases when coal is used in the commercial or residential sectors, the
                    assumption for unoxidized carbon should be 5%.
               Clearly, much additional research needs to be done in this area. These adjustments are
               suggested as initial default values. As  more work is done, countries are encouraged to
               report any additional information they may have to refine understanding of the amount of
               carbon unoxidized in various applications.
                Calculations of stored carbon for countries choosing to use a detailed technology based
                approach should be more straightforward since the counti-y would already be collecting
                fuel consumption data, at a disaggregated level. The methodology for calculating stored
                carbon (non-fuel uses) is the same as the procedures used in the Reference Approach.
                That is, fuel quantities for which carbon may be stored should be estimated, then
                converted to GJ, multiplied by the carbon emission factor to determine potential
                emissions, and then multiplied by the actual share of carbon stored to determine the
                carbon stored for each fuel. It may be that national experts working at a detailed
                technology based level may account for non-fuel uses for a more detailed level of products
                and processes. In this case, default factors may not apply, and fractions of carbon actually
                stored and in some cases carbon emission factors will have to be supplied by the national
                experts.
                The adjustments for stored carbon (deductions of Gg CO2 stored) would have to be made
                to the appropriate sector for which emissions are being estimated. In most cases, these
                adjustments are made to emission estimates from the industrial sector since most uses for
                which potential storage of carbon have been identified are from this sector. Countries
                should explicitly identify the sectoral category to which they have assigned the estimates of
                stored carbon.
PART 2
                                                                                                                   1.37

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EMISSIONS FROM ENERGY
                    This is also similar to the Reference Approach. For some end use categories emission
                    factors may be provided directly as kg CO2/Gj. Wherever emissions have been calculated
                    as carbon, the must be expressed as Carbon Dioxide (COj). To convert to CO* total
                    carbon oxidized should be multiplied by the molecular weight ratio of CO2 to C (44/12) to
                    find total carbon dioxide emitted from fuel combustion.
1.38

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                                                                             EMISSIONS  FROM  ENERGY
       1.5    Greenhouse  Gas  Emissions  from  Stationary
                Combustion
                1.5.1  Overview

                This section discusses greenhouse gas emissions (CO2, NOX, N2O, CO, CH4, and
                NMVOCs) from energy consumption in stationary sources. This section focuses on
                emissions from commercial fuel consumption, which includes virtually all fossil fuel
                combustion, but also includes the portion of biomass fuels traded commercially and used
                in large scale technology applications. These biomass emissions are estimated in exactly
                the same manner as fossil fuel combustion emissions, except for CO2 emissions 6. A large
                share of total global biomass fuel consumption, however, is not accounted for in
                commercial energy statistics. GHG emissions from this "traditional" biomass fuel use,
                primarily in developing countries, are calculated differently and discussed in the next
                section of this chapter.
                Emissions of non-CO2 greenhouse gases across activities (sectors, sub-sectors) will
                depend upon fuel, technology type, and pollution control policies. Emissions will also vary
                more specifically with size and vintage of the combustion technology, its maintenance, and
                its operation. As discussed in the previous section, CO2 emissions are not technology-
                dependent, although these emissions can be estimated by technology using a "bottom-up"
                approach, as described in this section.
                In addition to CO2, stationary fuel combustion is a major component of total NOX
                emissions in most countries. As defined here (i.e., excluding; "traditional" biomass), this
                category generally contributes a smaller but still significant share of national emissions of
                CO and NMVOC. With the exclusion of "traditional"  biomass, the stationary combustion
                category is generally a small contributor to total N2O and CH4, but these two gases are
                nonetheless discussed in some detail because of their  priority status within the
                IPCC/OECD programme.

                Organization of this section
                The next sub-section provides a general discussion of the emissions calculation method
                common to the estimation of all GHGs from detailed  fuel combustion data. This includes
                discussion of data needed including extensions required  based on energy data discussed
                earlier, and highlights the importance of fuel and technology specific emission factors in
                this approach. The following sub-section provides a series of tables of representative
                emission factors which illustrate the range of technologies of concern and the variations of
                emission rates across these technologies.
                   16 CO2 emissions resulting from biomass fuel consumption should not be included in a
                national energy emission totals to avoid double counting CO2. This double-counting would
                occur either because:  (I) biomass fuels may have been produced on a sustainable basis,
                particularly for commercial consumers, such that no net increase in CO2 occurs, or (2)
                production of CO2 from due to extraction of biomass fuels from existing stocks on a non-
                sustainable basis would be captured as part of emissions which are calculated as described
                in the Land Use Change and Forestry chapter in this manual. The IPCC method
                recommends that countries estimate CO2 emissions from biomass fuel consumption and
                report this as an information item.
r*ART 2
1.39

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EMISSIONS  FROM  ENERGY
                       Two additional sub-sections, discuss each of the relevant gases of interest is discussed
                       briefly. This discussion is presented in two parts - dealing with direct GHGs (CO2, N2O
                       and CH.,), and indirect GHGs (NOX, CO, and NMVOC) respectively. The priority area of
                       work for the IPCC/OECD programme in the initial stages was methodologies for direct
                       GHGs. Thus, improvements in methods for these gases are discussed in some detail. For
                       CO2 some additional discussion is provided to assist national experts who wish to do
                       these calculations at a "bottom-up" level  of detail. N2O and CH4 from stationary
                       combustion are relatively minor as shares of total emissions. Nonetheless, as priority
                       gases, a review of recent research results is included for each.

                       For indirect gases, the IPCC/OECD programme has not carried out any original methods
                       development work. However, these gases are traditional air pollutants, as well as indirect
                       GHGs, and have been the focus of a great deal of ongoing work outside the IPCC/OECD
                       programme. The discussion of these gases, is primarily oriented toward identification of
                       comprehensive, up-to-date references which have been published by other inventor)'
                       programmes, including CORINAIR, and programmes of individual countries.

                       Finally, the last subsection discusses some priorities for future work.
                        1.5.2  Recommended  Methodology

                        General Method
                        Estimation of emissions from stationary sources can be described using the following basic
                        formula:
                                                 Emissions = £ (EFabc x Activityab(.)
1
                        where:
                        EF = Emission Factor (g/GJ);

                        Activity = Energy Input (GJ);
                        a = Fuel type;

                        b = Sector-activity; and
                        c = Technology type.

                        Total emissions for a particular nation is the sum across activities, technologies and fuels of
                        the individual estimates.

                        Emission estimation is based on at least three distinct sets of assumptions or data:  I)
                        emission factors; 2) energy activities; and 3) relative share of technologies in each of the
                        main energy activities. Sources of the emission factors and energy activities data that are
                        relevant internationally are described briefly below and suggestions on appropriate use of
                        such data are made.
                        Technology share or technology splits for each of the various energy activities are needed
                        at least on a national level for non-CO2 greenhouse gas estimation since emission levels
                        are affected by the technology type. Unfortunately, there are no complete international
                        sources of data on technology splits and, as a result, each nation will need to develop its
                        own technology splits for each energy activity.
 1.40

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                                                                                EMISSIONS FROM  ENERGY
                The main steps in the inventory method can be summarized as follows:

                 I    Determine source of, and the form of, the best available, internationally verifiable,
                     national (or sub-national) energy activity data;

                2    Based on a survey of national energy activities, determine the main categories of
                     emission factors;

                3    Compile best available emission factor data for the country, preferably from national
                     sources. If no national source is available, select from the options described here.
                     Selection among the options should be based on an assessment of the similarity of
                     the country to the source of original measurements for types of technology and
                     operating conditions across main energy activities. The selection should also consider
                     the extent to which control technologies may be in place and the ability to clearly
                     separate and understand control policy assumptions that may be embedded in the
                     emission factor data.
                4    Based on the form of the selected emission factor data, develop assumptions
                     regarding  the technology categories to be used in the national inventory;17
                 5    Using these assumptions on technology categories, develop estimates, main activity
                     by main activity, of each of the greenhouse gases.

                6    Sum the individual activity estimates to arrive at the national inventory total for the
                     greenhouse gases.

                 Data Needs
                A considerable amount of detailed and specialized data is required to construct a national
                 inventory of GHGs from stationary fuel combustion. At minimum, the following types of
                 data are needed:
                 •   Energy Activity Data:
                 Energy data sources are discussed in the introduction. The same basic energy information
                 is needed in estimating other GHGs from fuel combustion.
                 International sources or locally available sources of energy activity data can be used,
                 provided that the definitions and formats specified in the IPCC methodology are used to
                 ensure comparability and transparency. However, national sources will be needed for
                 activity data relating to specific technologies. It should be noted, that in many countries,
                 energy consumption data may be available in truly "bottom-up" data collection efforts,
                 associated with major programmes to develop detailed emissions. That is, energy
                 consumption data may be collected, along with technology information on a source by
                 source, region  by region, or other disaggregated level. It is, of course, highly desirable to
                 have actual data on fuel use by technology type, rather than having to allocate down from
                 national statistics. It is  important, however, in  this situation, to carefully reconcile total
                 national energy accounts with "bottom-up" fuel use data to ensure that all fuel combustion
                 is being accounted for  and none is double counted.
                 •   Technology Splits for Energy Data
                 National data or assumptions on the technology shares of each of the main source sector
                 categories that have been identified  as important in each country are necessary to create
                 the linkage between  national energy balances and the emission factors. Again, this may be
                 bases on "bottom-up"  data collection at as detailed a level as individual sources, or it may
                   17 This may also require assumptions about the control technologies in place.
PART 2
1.41

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EMISSIONS  FROM  ENERGY
                       be more of a top down allocation based on statistical sampling, or engineering judgement
                       The objective is to match up fuel use, by fuel type, with specific technologies or classes of
                       technologies, for which credible emission factors for non-COi gases can be provided.

                       •   Emission Factor Data
                       Emission factors represent the average emission performance of a population of similar
                       technologies. Emission factors for all non-CO2 greenhouse gases from combustion
                       activities vary to lesser or greater degrees with:

                                •       fuel type;

                                «       technology;

                                •       operating conditions; and

                                •       maintenance and vintage of technology.

                       Good emission factors for gases other than COj are therefore usually technology specific,
                       but may still represent a wide distribution of possible values. In addition to technology
                       type, the impacts of equipment vintage, operating conditions, maintenance conditions, and
                       pollution control also affect emission factors. When available, the standard deviation of the
                       emission factor should be used to show the range of possible emissions factors, and hence
                       emissions, for each particular energy activity.18
                       There already exists a considerable body of literature and other data bases on emission
                       factors, particularly for the  indirect GHGs (NOX, CO,  and NMVOC) which are of great
                       interest as local and regional air pollutants, in addition  to their affect on global radiative
                       forcing of the atmosphere. In addition to the basic emissions for specific technology types,
                       in some cases adjustments for control technologies may be needed. Accounting for
                       controls is particularly critical to estimation of emissions from large stationary sources in
                       OECD countries, but probably has  a minor effect on emission estimates for the rest of the
                       world since control technologies are not typically used in these countries (See OECD/IEA,
                        1991).
                       Some tables of representative emission factors by main technology and fuel types were
                       presented in the previous preliminary methodology manual (OECD,  1991) distributed by
                       the IPCC. This information is still useful in illustrating the range and variation of sources
                       and emission rates, and is reproduced in the next section. More detail on current emission
                       factors and references is  presented in the gas-by-gas discussions which follow after the
                       next section.
                          18 Unfortunately, the standard deviation of emission factors is rarely reported with
                        emission factor data. One study shows that when considered, variation of emissions
                        factors within an energy activity vary widely, from 20 to more than 50 per cent (Eggleston
                        andMclnnes,  1987).
 1.42

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                                                                               EMISSIONS FROM ENERGY
                 1.5.3  Illustrative Emission  Factor  Data

                 Some tables of representative emission factors for NOX", CO, CH4, N2O, and NMVOCs
                 by main technology and fuel types (based on Radian, 1990) were presented in the previous
                 preliminary methodology manual (OECD, 1991) distributed by the IPCC. This information
                 is still useful in illustrating the range and variation of sources and emission rates, and is
                 reproduced  in Tables 2-8 to 2-12 for the major sectoral categories.20  All factors are
                 expressed on a grams per gigajoule of energy input basis (unless stated otherwise) and are
                 stated on a full molecular weight basis assuming that all NOX emissions are emitted as
                 NO2. These data are taken from Radian (1990) and show uncontrolled emission factors
                 for each of the technologies indicated. These emission factor data therefore do not include
                 the level of control technology that might be in place in some countries. For instance, for
                 use in countries where control policies have significantly influenced the emission profile,
                 either the individual factors or the final  estimate will need to be adjusted.

                 It may be necessary to make adjustments to "raw" emission estimates to account for
                 control technologies, in place. Alternative control technologies, with representative
                 percentage reductions, are shown  in Tables 2-13 to 2-16 (Radian, 1990) for the main
                 control technologies applicable to each sector. These lists reflect technologies in use for
                 large stationary sources in OECD countries. Preliminary indications are that, in the rest of
                 the world, control technologies are not typically used (See OECD/IEA, 1991). These data
                 should be used in combination with the uncontrolled emission factors to develop a "net"
                 representative emission factor for  each of the technologies to be characterized in the
                 national emission  profile; alternatively, the total emission estimate could be adjusted
                 downward according to the indicated percentage reduction.

                 Table 1-17 provides the fuel property assumptions upon which the Radian  data are based.
                 The emission factor data in these tables is provided primarily for illustrative purposes.
                 These factors could be used as a starting point or for comparison by national experts
                 working on detailed "bottom-up" inventories. However, much more detailed data are
                 available and should also be consulted in this process. More detail on current emission
                 factors and references is presented in the gas-by-gas discussions in the next two sections.
                     The convention in this document is that NOX emissions from fossil fuel combustion
                 are expressed on a full molecular basis assuming that all NOX emissions are emitted as
                 NO2. It should be noted that this is inconsistent with the convention reflected in the
                 methods on NOX emissions from traditional biomass burning, which are expressed on a
                 full molecular weight basis assuming the emissions are all in the form of NO. This is a
                 convention common in literature on biomass burning. This inconsistency should be
                 reconciled in future versions of the methodology.

                   20 Little reliable information on N2O and NMVOCs emission factors was available at the
                 time these tables were developed.  Some more recent information is presented or
                 reference later in this section.
PART 2
1.43

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EMISSIONS FROM  ENERGY
                                                                 TABLE 1-7
                                                   UTILITY BOILER SOURCE PERFORMANCE

Source
Natural Gas - Boilers
Gas Turbine Combined Cycle
Gas Turbine Simple Cycle
Residual Oil Boilers
Distillate Oil Boilers
Shale Oil Boilers
MSW - Mass Feed2
Coal - Spreader Stoker
Coal - Fluidized Bed Combined Cycle
Coal - Fluidized Bed
Coal - Pulverized Coal
Coal - Tangentially Fired
Coal - Pulverized Coal Wall Fired
Wood-Fired Boilers2

CO
19
32
32
15
IS
15
98
121
N/A
N/A
14
14
14
1,473
Emissions
CH4
O.I
6.1
5.9
0.7
0.03
0.7
N/A
0.7
0.6
0.6
0.6
0.6
0.6
18
Factors (g/GJ energy input)
NOX
267
187
188
201
68
201
140
326
N/A
255
857
330
461
112
N2O
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0.8
N/A
N/A
0.8
0.8
0.8
N/A
NMVOCs
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
                      1 Values were originally based on "gross" (or higher) heating value; they were converted to "net" (or lower) heating value by
                      assuming that net heating values were 5% lower than gross heating values for coal and oil, and 10% lower for natural gas.
                      These percentage adjustments are the OECD/IEA assumption on how to convert from gross to net heating values.

                      1 Emission factors were adjusted to lower heating value assuming a 5% difference in energy content between lower heating
                      value and higher heating value.

                      Source: Radian, 1990.                                                          	
                                                                   TABLE 1-8
                                                       INDUSTRIAL BOILER PERFORMANCE
Emissions Factors (g/GJ energy input)1
Source
Coal-Fired Boilers
Residual Oil-Fired Boilers
Natural Gas-Fired Boilers
Wood-Fired Boilers2
Bagasse/Agricultural Waste-Fired
Boilers2
MSW - Mass burn2
MSW - Small Modular2
CO
93
15
17
1,504
1,706
96
19
CH4
2.4
2.9
1.4
15
N/A
N/A
N/A
NOX
329
161
67
115
88
140
139
N2O
N/A
N/A
N/A
N/A
N/A
N/A
N/A
NMVOCs
N/A
N/A
N/A
N/A
N/A
N/A
N/A
                          ' Values were originally based on "gross" (or higher) heating value; they were converted to "net" (or lower) heating
                          value by assuming that net heating values were 5% lower than gross heating values for coal and oil, and 10% lower
                          for natural gas. These percentage adjustments are the OECD/IEA assumption on how to convert from gross to net
                          heating values.
                          2 Emission factors were adjusted to lower heating value assuming a 5% difference in energy content between lower
                          heating value and higher heating value.

                          Source: Radian,  1990.                                                                 	
  1.44

-------
                                                                                        EMISSIONS  FROM ENERGY
                                                           TABLE 1-9
                                        KILNS, OVENS, AND DRYERS SOURCE PERFORMANCE
Emissions Factors (g/Gj energy input)1
Industry
Cement, Lime
Cement, Lime
Cement, Lime
Coking, Steel
Source
Kilns - Natural Gas
Kilns - Oil
Kilns - Coal
Coke Oven
CO
83
79
79
211
CH4
I.I
1.0
1.0
1
NOX
1,111
527
527
N/A
N20
N/A
N/A
N/A
N/A
NMVOCs
N/A
N/A
N/A
N/A
              Chemical Processes, Wood, Asphalt,  Dryer - Natural Gas
              Copper, Phosphate
                                                                                       64
                                                                                                N/A
                                                                                                           N/A
              Chemical Processes, Wood, Asphalt,  Dryer - Oil
              Copper, Phosphate
                                                                   16
                                                                             1.0
                                                                                       168
                                                                                                N/A
                                                                                                           N/A
              Chemical Processes, Wood, Asphalt,  Dryer - Coal
              Copper, Phosphate
                                                                  179
                                                                             1.0
                                                                                      226
                                                                                                N/A
                                                                                                           N/A
               Values were originally based on "gross" (or higher) heating value; they were converted to "net" (or lower) heating value by
              assuming that net heating values were 5% lower than gross heating values for coal and oil, and 10% lower for natural gas.
              These percentage adjustments are the OECD/IEA assumption on how to convert from gross to net heating values.

              Source: Radian, 1990.
                                                          TABLE 1-10
                                               RESIDENTIAL SOURCE PERFORMANCE
Emissions Factors (g/GJ energy input)
Source
Wood Pits2
Wood Fireplaces
Wood Stoves
Propane/Butane Furnaces
Coal Hot Water Heaters
Coal Furnaces
Coal Stoves
Distillate Oil Furnaces
Gas Heaters
CO
4,949
6,002
18,533
10
18
484
3,580
13
10
CH4
200
N/A
74
I.I
N/A
N/A
N/A
5
1
NOX
147
116
200
47
158
232
179
51
47
N2O
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
NMVOCs
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
                        Values were originally based on "gross" (or higher) heating value; they were converted to "net" (or
                       lower) heating value by assuming that net heating values were 5% lower than gross heating values for
                       coal and oil, and 10% lower for natural gas. These percentage adjustments are the OECD/IEA
                       assumption on how to convert from gross to net heating values.

                        Emission factors were adjusted to lower heating value assuming a 5% difference in energy content
                       between lower heating value and higher heating value.

                       Source: Radian, 1990.
PART  2
1.45

-------
EMISSIONS  FROM  ENERGY
TABLE Ml
COMMERCIAL SOURCE PERFORMANCE
Emissions Factors (g/GJ energy input)
Source
Wood Boilers'
Gas Boilers
Residual Oil Boilers
Distillate Oil Boilers
MSW Boilers''
Coal Boilers
Shale Oil Boilers
Open Burning - MSW
Open Burning - Agriculture
Incineration - high efficiency
Incineration - low efficiency
CO
199
9.6
17
16
19
195
17
42 kg/Mg
58 kg/Mg
5 kg/Mg
10 kg/Mg
CH4
15
1.2
1.6
0.6
N/A
10
1.6
6.5 kg/Mg
9 kg/Mg
N/A
N/A
NOX
33
48
155
64
463
236
186
3 kg/Mg
N/A
1.5 kg/Mg
1 kg/Mg
N2O
4.3
2.4
46.5
15.7
N/A
59.1
46.5
N/A
N/A
N/A
N/A


NMVOCs
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
                            ' Values were originally based on "gr°ss" (or higher) heating value; they were converted to "net" (or
                            lower) heating value by assuming that net heating values were 5% lower than gross heating values for coal
                            and oil. and 10% lower for natural gas. These percentage adjustments are the OECD/IEA assumption on
                            how to convert from gross to net heating values.
                             Emission factors were adjusted to lower heating value assuming a 5% difference in energy content
                            between lower heating value and higher heating value.

                            Source: Radian, 1990.
 1.46

-------
                                                                                     EMISSIONS  FROM  ENERGY
                                                        TABLE 1-12
                                         UTILITY EMISSION CONTROLS PERFORMANCE
Efficiency     CO
                                                               CH4
                                                           NOX
N20
                                                                                          NMVOCs
                                                                                                      Date
                      Technology
                                           Loss     Reduction  Reduction   Reduction   Reduction  Reduction  Available2
Low Excess Air (LEA)
Overfire Air (OFA) - Coal
OFA - Gas
OFA - Oil
Low NOX Burner (LNB) - Coal
LNB - Tangent. Fired
LNB - Oil
LNB - Gas
Cyclone Combustion Modification
Ammonia Injection
-0.5
0.5
1.25
0.5
0.25
0.25
0.25
0.25
0.5
0.5
+ +
+ +
+ +
+ +
+ +
+ +
+ 4-
+ +
N/A N/A
+ +
IS
25
40
30
35
35
35
50
40
60
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
1970
1970
1970
1970
1980
1980
1980
1980
1990
1985
Selective Catalytic Reduction
(SCR) - Coal
                                                                          80
                                                                                   N/A
                                                                                             N/A
                                                                                                      1985
              SCR - Oil, AFBC
                                                                          80
                                                                                   N/A
                                                                                             N/A
                                                                                                      1985
              SCR - Gas
                                                                          80
                                                                                   60
                                                                                            N/A
                                                                                                      1985
Water Injection - Gas Turbine
Simple Cycle
                                                                          70
                                                                                   N/A
                                                                                            N/A
                                                                                                      1975
SCR - Gas Turbine
CO2 Scrubbing - Coal
CO2 Scrubbing - Oil
CO2 Scrubbing - Gas
Retrofit LEA
Retrofit OFA - Coal
Retrofit OFA - Gas
Retrofit OFA - Oil
Retrofit LNB - Coal
Retrofit LNB - Oil
Retrofit LNB - Gas
Burners Out of Service
1 8
22.5 N/A
16.0 N/A
11.3 N/A
-0.5 +
0.5 +
1.25 +
0.5 +
0.25 +
0.25 +
0.25 +
0.5 +
+• 80
N/A N/A
N/A N/A
N/A N/A
+ IS
+ 25
+ 40
* 30
+ 35
+ 35
+ 50
+ 30
60
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
1985
2000
2000
2000
1970
1970
1970
1970
1980
1980
1980
1975
               Efficiency loss as a percent of end-user energy conversion efficiency (ratio of energy output to energy input for each
              technology) due to the addition of an emission control technology. Negative loss indicates an efficiency improvement.

               Date technology is assumed to be commercially available.

              Note: A "+" indicates negligible reduction.

              Source: Radian, 1990.
PART  2
                                                                                                                          1.47

-------
EMISSIONS  FROM  ENERGY
                                                             TABLE 1-13
                                          INDUSTRIAL BOILER EMISSION CONTROLS PERFORMANCE
                                               Efficiency
                                                           CO
                                                                    CH4
NOX
                                                                                                NMVOCs
                                                                                                           Date
                            Technology
                                                Loss1    Reduction  Reduction  Reduction   Reduction   Reduction  Available^
Low Excess Air (LEA)
Overfire Air (OFA) - Coal
OFA -Gas
OFA -Oil
Low NOX Burner (LNB) - Coal
LNB -Oil
LNB - Gas
Flue Gas Recirculation
Ammonia Injection
Selective Catalytic Reduction
(SCR) - Coal
SCR-Oil.AFBC
SCR - Gas
Retrofit LEA
Retrofit OFA - Coal
Retrofit OFA - Gas
Retrofit OFA -Oil
Retrofit LNB - Coal
Retrofit LNB -Oil
Retrofit LNB - Gas
-0.5 + H
0.5 + •>
1.25 + •>
0.5 + H
0.25 +•
0.25 +
0.25 +
0.5 +
0.5 +
1 8
1 8
1 8
-0.5 +
0.5 +
1.25 +
0.5 +
0.25 +
0.25 +
0.25 +
r 15
^ 25
^ 40
H 30
H 35
^ 35
^ 50
^ 40
4- 60
<- 80
+ 80
+ 80
+ 15
+ 25
+ 40
+ 30
+ 35
+ 35
+ 50
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
60
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
1970
1970
1970
1970
1980
1980
1980
1975
1985
1985
1985
1985
1970
1970
1970
1970
1980
1980
1980
                     ' Efficiency loss as a percent of end-user energy conversion efficiency (ratio of energy output to energy input for each
                     technology) due to the addition of an emission control technology. Negative loss indicates an efficiency improvement.

                     ^Date technology is assumed to be commercially available.

                     Note: A "+" indicates negligible reduction.

                     Source: Radian, 1990.	
  1.48

-------
                                                                                  EMISSIONS  FROM ENERGY
TABLE 1-14
KILN, OVENS, AND DRYERS EMISSION CONTROLS PERFORMANCE
Technology
LEA - Kilns, Dryers
LNB - Kilns, Dryers
SCR - Coke Oven
Nitrogen Injection
Fuel Staging
Efficiency
Loss1
-6.4
0
1.0
N/A
N/A
CO
Reduction
•f
+
8
N/A
N/A
CH4 NO'X
Reduction Reduction
+ 14
+ 35
+ 80
N/A 30
N/A 50
N20
Reduction
N/A
N/A
60
N/A
N/A
NMVOCs
Reduction
N/A
N/A
N/A
N/A
N/A
Date
Available2
1980
1985
1979
1990
1995
               ' Efficiency loss as a percent of end-user energy conversion efficiency (ratio of energy output to energy input for each
               technology) due to the addition of an emission control technology. Negative loss indicates an efficiency improvement

               2Date technology is assumed to be commercially available.

               Note: A"+" indicates negligible reduction.

               Source: Radian,  1990.
PART  2
                                                                                                                        1.49

-------
EMISSIONS  FROM  ENERGY
TABLE 1-15
RESIDENTIAL AND COMMERCIAL EMISSION CONTROLS PERFORMANCE
Technology
Catalytic Woodstove
Non-Catalytic Modified
Combustion Stove
Flame Ret. Burn. Hd.
Heed. Mix. Burn. Hd.
Integr. Furn. Syst
Blueray BurnVFurn.
MAN. Burner
Radiant Screens
Secondary Air Baffle
Surface Comb. Burner
Amana HTM
Modulating Furnace
Pulse Combuster
Catalytic Combuster
Replace Worn Units
Tuning, Seasonal Maintenance
Red. Excess. Firing
Red fir with new ret b
Pos. Chimney Dampers
Inc. thermal anticip.
Night therm, cutback
Low Excess Air
Hue Gas Recirculation
Over-fire Air
Over-fire Air
Low NOx Burners
Low NOX Burners
Efficiency
Loss1
(%)
-44
-30
-9
-7
-12
-12
-13
-7
N/A
N/A
-21
-7
-36
-29
N/A
-2
-19
-40
-8
-1
-IS
-0.8
0.6
1
1
0.6
0.6
CO
Reduction
(%)
90
15
28
43
13
74
N/A
62
16
55
-55
N/A
N/A
N/A
65
16
14
14
II
43
17
N/A
N/A
N/A
N/A
N/A
N/A
CH4
Reduction
(%)
90
50
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
NOX
Reduction
(%)
-27
-5
N/A
44
69
84
71
55
40
79
79
32
47
86
N/A
N/A
N/A
N/A
N/A
N/A
N/A
15
50
20
30
40
50
N20
Reduction
(%) :
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
NMVOCs
Reduction
(%)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Date
Available2
1985
1985




1980














1970
1975
1970
1970
1980
1980
                   'Efficiency loss as a percent of end-user energy conversion efficiency (ratio of energy output to energy input
                   for each technology) due to the addition of an emission control technology. Negative loss indicates an
                   efficiency improvement.
                   2Date technology is assumed to be commercially available.
                   Note: A "+" indicates negligible reduction.
                   Source: Radian, 1990.
1.50

-------
                                                                              EMISSIONS FROM  ENERGY
TABLE 1-16
FUEL PROPERTIES'
Fuel
GAS
Butane/Propane
Coke Oven Gas
Methane (pure)
Natural Gas
Process Gas
LIQUID
Crude Shale Oil
Diesel/Distillate
Gasoline
Jet A
Methanol
Residual Oil
SOLID
Bagasse/ Agriculture
Charcoal
Coal
MSW
Wood
Heating Value
(GJ/tonne)2

45.7
36.7
45.0
46.0
48.6

40.9
42.9
H6.9MJ/gal
41.0
56.1 MJ/gal
40.9

8.6
27.6
22.0
10.7
10.1
Carbon
(wt percent)

82.0
56.1
75.0
70.6
70.6

84.5
87.2
85.7
86.1
37.5
85.6

22.6
87.0
65.0
26.7
27.0
                   Values were originally based on "gross" (or higher) heating value; they were converted to "net" (or
                  lower) heating value by assuming that net heating values were 5% lower than gross heating values for
                  coal and oil, and 10% lower for natural gas. These percentage adjustments are the OECD/1EA
                  assumption on how to convert from gross to net heating values.

                  2 Unless otherwise indicated.

                  Source: Radian, 1990.
                 1.5.4  Discussion  Of Direct  GHGs

                 In the initial stages of the IPCC/OECD programme it was recognized that work on both
                 methods development and national inventories needed to be prioritized, as it was not
                 possible to deal with all of the gases and sources simultaneously. The direct greenhouse
                 gases were established as the priority, with priority within this category in the following
                 order CO2, methane and nitrous oxides  (IPCC/OECD, 1991). CO2from fuel
                 combustion has been discussed in detail in the previous section. It is discussed again here
                 briefly to emphasize the possible linkage of detailed CO2 calculations with the detailed
                 approach required for estimation of other GHGs from combustion.

                 Methods for estimating emissions of methane and nitrous oxide are not yet well
                 established, but are evolving rapidly based on a great deal of research underway within the
                 global change research community and elsewhere. For this reason, expert groups have
                 been established to recommend improvements in estimation methods for a variety of
                 source categories - including fuel combustion - which produce these gases. Information
                 developed  by these groups provides some improvements in emission estimation methods
                 as described below.
PART 2
                                                                                                                   1.51

-------
EMISSIONS FROM  ENERGY
                       Carbon Dioxide (CO2): The IPCC Reference Approach to estimation of CO2 emissions
                       from fuel combustion is described in the previous section. This method is designated as a
                       reference method because it is transparent, easy  to implement, and produces very reliable
                       and comparable estimates for all IPCC countries. It is also clear that more detailed
                       information on CO2 emissions by source type can be useful to most countries. Countries
                       which have detailed data bases for estimating emissions of non-CO2 gases are encouraged
                       to also estimate CO2 emissions at a "bottom-up" level of detail based on the data
                       developed to estimate non-CO2 emissions.

                       Specifically, in order to estimate non-CO2 emissions using the emission factors provided in
                       Tables 2-9 to 2-13, countries will need to determine the amount of energy consumed by
                       sector, technology type, and fuel type. Since the fuel type is known, the carbon emission
                       coefficients provided in Table  I-1 by fuel type could, in theory, be applied to the total
                       amount of input energy for each fuel/technology type by sector to  determine total carbon
                       consumed for that category. To determine total CO2 emissions, one would sum across all
                       technology/fuel combinations and all sectors, and then follow the steps outlined in die
                       CO2 section including adjusting for any carbon unoxidized during combustion (see Table I -
                       7). It would also be necessary to account for non-energy uses emitting carbon (see Table
                       1-6), in order to ensure that total carbon in fuels is covered.
                       As noted in the previous section, there may be some variations in the carbon emission
                       factors (due  to variations in fuel quality),  and very likely will be differences in fraction
                       oxidized for different technologies. If more detailed factors are available based on local
                       conditions and measurements, these should be used (and documented). In addition, as
                       discussed in  the previous section, there are a number of complex accounting problems
                       which can be ignored at the "top-down" level, but have to be addressed at a "bottorn-up"
                       level of detail. These are especially difficult in accounting for all of the carbon released
                       during transformation of energy from one form to another (e.g., refining of crude oil). The
                       IPCC Guidelines do not yet provide detailed guidance for dealing with these complexities.
                       Rather, it is recommended that national experts currently working at the detailed  use
                       their own judgement to deal with the detailed questions which must be answered at the
                       "bottom-up" level. It is also strongly recommended that all countries also prepare
                       estimates using the IPCC Reference Approach and reconcile the results. This will help
                       identify any carbon in original fuels (e.g., transformation losses) which may not have been
                       accounted for in the detailed "bottom-up" accounts.

                       Methane (CH«): CH4 is produced from fuel combustion in small  quantities due to
                       incomplete combustion of hydrocarbons in fuel. In large, efficient combustion facilities, the
                       emission rate is very low. In smaller combustion  sources, emissions rates can be higher,
                       particularly where smoldering combustion conditions occur. In global terms, total
                       emissions from this source category (here defined to exclude "traditional" biomass burning
                       discussed in  the next section) are believed to be small relative to other anthropogenic
                       source categories. Nevertheless, because of the importance of this gas, these emissions
                       are being studied carefully.

                       In a background paper prepared for the informal experts group, Berdowski, et al., (1993)
                       summarized the average emission rates for fuel combustion within broad subsectors. The
                       highest rates of methane emissions from fuel combustion are reported for residential
                       applications, where coal and "traditional" biomass fuels are used in small stoves for cooking
                       and heating.  Emissions from "traditional" fuels such and fuelwood and agricultural residues
                       are discussed in the next section. Emissions from coal use in residential stoves can also be
                       quite high relative to other combustion  applications, as shown in Table 1-18. This table
                       gives average emission factors for broad  classes of combustion. It is clear that actual
                       emissions would vary within each category by technology type, fuel quality, and operating
                       conditions. However, the very aggregated information presented is sufficient to show that
 1.52

-------
                                                                                EMISSIONS  FROM ENERGY
                methane emissions from fossil fuel combustion in large scale utility and industrial
                applications are low, with utility emission rates being less than I % of average rates for
                residential coal combustion.
                Based on the average emission factors in the above table, Berdowski, et al., (1993) estimate
                global emissions from residential coal use to be in the range of 2.5-5.0 Tg/year, despite the fact
                that residential coal use is common in only a few countries. The total emissions from utility and
                industrial coal use and all other fossil fuel use was estimated to be less than  1.5 Tg/year. Despite
                the fact that large amounts of fuel are used in these latter applications, the very low average
                emission rates result in very small contributions to total emissions.

                                                     TABLE 1-17
                      GLOBAL EMISSION FACTORS AND EMISSIONS OF METHANE FROM COMBUSTION OF SOLID FUELS.
Fuel (type)

Coal
Residual oil
Distil, oils
Natural gas, LPG

Utilities
1
3
-
1
Emission factor (g/GJ)
Industry
10
3
1
4

Residential
300 (range 200-400)
-
7
3
             Table adapted for Berdowski, et al., 1993
             References: For residential coal use, USEPA, 1985; Zeedijk, 1986. All other categories from Veldt, 1991.


                 Nitrous Oxide (N2O): N2O is produced from combustion of fuels, although this source
                 category (stationary combustion, excluding "traditional" biomass burning) is presently
                 considered to be minor, relative to other anthropogenic source categories. The
                 mechanisms that cause the formation of N2O during the combustion of fossil fuel are now
                 fairly well understood (see De Soete, 1993). The basic knowledge on both gas phase and
                 heterogeneous N2O chemistry is well able to explain and to forecast at least in a
                 qualitative manner N2O emissions from different combustion sources and flue gas
                 treatment techniques.
                 Nitrous oxide (N2O) is produced directly from the combustion of fossil fuels. Gas phase
                 N2O chemistry is relatively well understood as it is part of NO kinetics and N2O appears
                 as a by-product of the so-called fuel-NO mechanism. For combustion temperatures well
                 below 1000 K or above 1200 K the emission factor for N2O is almost zero or negligible; in
                 the temperature range between about 800 and 1100 K N2O emissions are reaching the
                 highest levels with a maximum around  1000 K. Increasing the oxygen concentration or the
                 pressure tends to increase the  emissions.

                 Fundamental studies of non-catalytic heterogeneous reactions on the formation and
                 destruction of N2O only started in recent years,  so the available experimental data is still
                 rather scarce. The main mechanisms for the N2O chemistry appear to be: destruction of
                 N2O on bound carbon atoms, the formation of N2O from  char bound nitrogen atoms, and
                 the formation of N2O from NO and reduced sulfates. Catalytic N2O chemistry may play a
                 role in the following cases:

                 •    at overall reducing conditions (catalysts in spark ignition cars and trucks),

                 •    at overall oxidizing conditions (de-NOx-techniques  such as Selective Catalytic
                      Reduction [SCR], emission abatement of diesel engines and lean-burn spark ignition
                      engines), and

                 •    catalytic formation and destruction (e.g. during fluidized bed combustion caused by
                      the presence of CaO).
PART 2
1.53

-------
EMISSIONS FROM  ENERGY
                       Recent re-evaluation of available emission factor data from fuel combustion showed that in
                       measurements before July 1988 often a so-called artefact appeared stemming from the
                       presence of NOX and SO2 in samples, which resulted in erroneous emission factors whjch
                       were much too high, thereby highly overestimating the importance of this source category
                       (Muzio and Kramlich, 1988). Since the recognition of this artefact in June 1988 new
                       measurements have lead to new reliable emission factors from different conventional
                       stationary combustion sources (De Soete, 1993).

                       Emission factors can be limited to one value per fuel type for all applications, since relevant
                       knowledge is now readily available, (see De Soete (1993) and references therein)
                       Advanced (Pressurized) Fluidized Bed Combustion [(P)FBC] emissions are dependent on
                       the rank of the coal: brown coal produces less emissions than bituminous coal. The
                       emission factors for waste combustion and especially for sludge incineration are very high,
                       with a tendency to increase when FBC technology is applied.

                       Combustors with application of catalytic reduction techniques for emission abatement (e.g.
                       SCR or Non-Catalytic Selective Reduction [NCSR] of NO,,) also have estimated emission
                       factors. NCSR experiments suggest that the application of this control technology
                       increases the emission factor for N2O; for SCR no differences are observed. In the case of
                       NCSR the N2O emissions are higher from urea or cyanuric acid injection than in the case
                       of ammonia injection. These control technologies may not only be applied on large scale
                       facilities exploited by utilities or industry, but may also be applied in modern woodstoves.
                       Due to the uncertainty for the last categories at present an uncertainty range for these
                       sources is most appropriate. Default uncertainty ranges  still have  to be determined, but a
                       preliminary range is presented in this report.

                       Default emission factors and uncertainty ranges are shown in Table 1-19. When a country
                       has its own locally determined emission factors, these are of course preferred above the
                       default factors reported here. However, care should be  taken that no artefact data were
                       used in deriving the factors.
                       Reliable emission factors for non-commercial fuel combustion in particular fuelwood and
                       charcoal are currently not yet available because of lack of data on emission measurements
                       for these combustion technologies. This  refers amongst others to fuelwood, charcoal
                       (production and use in residential, commercial and industrial sectors), crop residues and
                       dung. Published data are scarce and the representativeness for global application is
                       questionable. Also, in the preparation of national inventories care should be taken to avoid
                       double counting, since emissions of fuelwood use may also be included  in the category of
                       biomass burning. (Olivier, 1993)
 1.54

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                                                                                  EMISSIONS FROM  ENERGY
                                                      TABLE 1-18
                                    ESTIMATED DEFAULT EMISSION FACTORS FOR STATIONARY
                                                 COMBUSTION FACILITIES.
                              Technology
  Emission factors
  (S N2O/GJ energy
      input)
(or g NjO/ton waste)
Uncertainty range
    (ibidem)
                               Conventional facilities, uncontrolled
                               Coal
                                                          1.4
                                                                            0-10
                               Oil
                                                          0.6
                                                                            0-2.8
                               Gas
                                                          0.1
                                                                            0-1.1
                               Conventional facilities, controlled
                               Selective catalytic
                               reduction (SCR) of NOx
                                                     see uncontrolled
                      see uncontrolled
                               NCSR
                                                          NA
                                                                          10-100
                                                                               **5T
                              Other combustion facilities:
                               Fluidized bed com-
                               bustion - hard coal
                                                          NA
                         10-95
                               FBC - brown coal, peat,
                               wood
                                                          NA
                         10-30
                               Gas turbines - oil, gas
                                                          NA
                          0-5'
                               N.B.
                                       NA = Not Available
                                         If the combustion temperature exceeds 1000 °C one may use
                                       a range of 0-10.
                                          Preliminary estimate with NH3 injection at lower end and
                                       with urea injection at higher end of range.
                              Source:   De Soete (1993) and references therein.


                  1.5.5  Discussion Of Indirect  GHGs

                 The IPCC/OECD programme has not yet addressed the indirect GHGs in detail. This is
                 consistent with the initial priorities within the IPCC/OECD programme. As noted above,
                 fuel combustion is a major source for all of these gases. Because they are important
                 contributors to a range of local and regional, as well  as global atmospheric pollution
                 problems, NOX, CO and NMVOC have been widely studies and reported. The Radian data
                 cited above reflect estimates of performance ranges  of main combustion technologies in
                 place worldwide, as of 1990. They are still considered to be reasonably representative.
                 However, since in most instances the data are based on measurement samples taken from
                 the United States, they represent averages of operating conditions, sizes and vintages of
                 units found there.  In all cases they are averages over a range of technologies, fuel qualities,
                 and operating conditions.

                 More detailed alternative emission factor source data representative of the precise
                 technologies and other conditions in a particular country would always be desirable.
                 National experts working on detailed emission of non-CO^ GHGs (particularly the
                 indirect gases) should consult the extensive literature on emission factors and other
                 estimation procedures which has been  developed by other inventory programmes outside
                 of the framework of the IPCC/OECD programme. As distinguished from the Radian
                 emission factors, these data generally contain more technology detail, and are  further
                 detailed by sizes of the various technologies. There is also a slight difference in the
PART 2
                                                                                                                        1.55

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EMISSIONS FROM  ENERGY
                       technology representation, but this may be more a terminology than a technical difference.
                       The specific nature of these control assumptions should be known and carefully matched
                       with actual conditions in the specific country in selecting the specific factors to be used.

                       Some key examples of data sources are:
                       •   The CORINAIR Inventory: Default Emission Factors Handbook (Bouscaren, 1992);

                       •   U.S. EPA's Compilation of Air Pollutant Emissions Factors (AP-42), 4th Edition  1985,
                                (U.S. EPA,  1985), and Supplement F, (U.S. EPA, 1993);

                       •   Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory
                            (Stockton and Stelling, 1987)
                       •   Proceedings of the TNO/EURASAP Workshop (TNO Inst of Environmental
                            Sciences, 1993)
                        J   Emissions Inventory Guidebook (European Environment Agency, forthcoming)
                        •   EMEP and CORINAIR Emission  Factors and Species  Profiles for Organic Compounds.
                            (Veldt, 1991);
                        •   Other National Compilations of Emission Factors Include
                                  Netherlands
                                  Norway
                                  Germany
                                  Walbeck, et al., 1988
                                  Japan
                                  United Kingdom
                                Bakkum, et al., 1987, Okken, 1989
                                Statens forurensningstilsyn, 1990
                                Brieda, 1989, Fritsche, 1989, Rentz et al., 1988,
                                JAERI, 1988
                                Essleston and Mclnnes, 1987
Nitrogen Oxides (NOX): Electricity generation and industrial fuel combustion activities
are similar in that they provide combustion conditions conducive to NOX formation. NOX
emissions depend in part on the nitrogen contained in the fuel (this may be especially
important for coal), but more importantly on the firing configuration of the technology.
Excess air and .high temperatures contribute  to high NOX emissions. Such conditions are
highly variable by type of boiler; for instance, for oil-fired plants, tangential burner
configurations generally have lower emission coefficients than horizontally opposed units.
Also, the size of the boiler will affect the NOX emission rate due to the lower
temperatures of smaller units.
Usage of the technology can also significantly alter the pattern of NOX emissions.
Measurements of emissions show a 0.5% to  1.0% decrease in NOX emission rates for
every 1.0% decrease in load from full load operation. That is, as the usage rate increases,
so does the emission rate associated with the facility.
Finally, control policies and related technological changes to meet emission limits directly
influence NOX emissions. Emissions from large facilities can be  reduced by up to 60% by
straightforward adjustments to the burner technology.2'  These adjustments are often
standard in new facilities, but may not exist in older facilities in many OECD countries and
may be especially rare in non-OECD countries. NOX controls may also increase the rate
of CO emissions. Information on the stock of combustion facilities, their vintage, and level
of control are therefore necessary to accurately estimate emissions from large combustion
facilities.
                            21  This can be done, for example, by limiting the excess air in combustion or by
                         staging the combustion process.
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                                                                                 EMISSIONS  FROM  ENERGY
                 NOX emissions from small combustion facilities (small industry, commercial and residential)
                 tend to be much less significant than for large facilities due to lower combustion
                 temperatures. Nevertheless, emissions will depend on the specific combustion conditions
                 of the activity in question, and an effort should be made to carefully characterize the type
                 of activity, on average, in order to select appropriate emission factors.

                 For many years, NOX has been the target of environmental policies for its role in forming
                 ozone (O3), as well as for its direct acidification effects. As a result, NOX emission
                 inventories and related data such as emission factors are more widely available than those
                 for the other non-CO2 greenhouse gases considered here. The sources listed above
                 provide a large number of emission factors depending on technology, fuel characteristics,
                 operating conditions, size, vintage, etc.

                 Carbon  Monoxide (CO): By comparison to NOX, combustion conditions in large
                 facilities are less conducive to formation and release of CO emissions. CO is an unburnt
                 gaseous combustible that is emitted in small quantities due to incomplete combustion. It
                 have also been the target of emission control policies in some countries and hence must
                 be estimated with these controls in mind. It is directly influenced by usage patterns,
                 technology type and size, vintage, maintenance and operation of the technology. Emissions
                 can vary by several orders of magnitude, for example, for facilities that are improperly
                 maintained  or poorly operated, such as may be the case for many older units. Similarly,
                 during periods of start-up, combustion efficiency  is lowest, and CO emissions are higher
                 than during periods of full operation.

                 Size of the unit may indicate that combustion is less controlled and hence the CO
                 emission  coefficients for  smaller units are likely to be higher than for large plants. Also
                 wood stoves, due to their largely inefficient combustion of the fuel, have particularly high
                 emission  rates of CO.  For these reasons, an understanding of commercial and residential
                 activities are key to the estimation of CO from stationary sources,  particularly in non-
                 OECD countries where residential consumption  of wood and other vegetal fuels is
                 commonly high.

                 CO emissions from stationary sources are estimated in the same way as for NOX
                 emissions. Detailed energy data provide  the basis for estimation, but there may be
                 significant variation in the precise size and type of combustion technologies in place. A
                 main combustion source of CO is the residential  sector, where there is great variation in
                 technology by geographic region due to a variety  of manufacturers as well as
                 unconventional combustion modes that may be found throughout the world. This may be
                 especially the case for wood fuel use22 — an area where data are weak both on total
                 energy consumption and characterization of the range of technologies in use in different
                 regions of the world.

                 With these notes of caution in mind, another data source for CO emission factors from
                 stationary sources is provided in {.'Office Federal de la Protection de [.'Environment, Bern,
                 Switzerland (OFPE, 1987). This source is based on other European  sources; it does
                    22Some wood fuel use which is covered in commercial energy statistics and for which
                 technology and emission factor data are known, may be included in the calculation
                 described in this section. For developing countries, however, there is frequently a large
                 share of "traditional" biomass use, which is generally not included in commercial energy
                 statistics, and data on the mix of specific technologies used is lacking. For these countries
                 an optional simpler method of calculating emissions from "traditional" biomass fuel use is
                 provided in the next section. National experts must take care to ensure  that there is not
                 double counting,  if more than one method is used.
PART 2
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EMISSIONS FROM ENERGY
                       provide a range for each of the activity categories for CO emission factors when combined
                       with the Radian factors above.
                       Non-Methane Volatile Organic Compounds (NMVOC):  As with CO, combustion
                       conditions in large facilities are less conducive to formation and  release of NMVOC
                       emissions. VOCs are also unburnt gaseous combustibles that are emitted in small
                       quantities due to incomplete combustion. They have also been the target of emission
                       control policies in some countries and hence must be estimated with these controls in
                       mind. They are directly influenced by usage patterns, technology type and size, vintage,
                       maintenance and operation of the technology. Emissions can vary by several orders of
                       magnitude, for example, for facilities that are improperly maintained  or poorly operated,
                       such as may be the case for many older units. Similarly, during periods of start-up,
                       combustion efficiency is lowest, and NMVOC emissions are higher than during periods of
                       full operation.
                       Size of the unit may indicate that combustion is less controlled and hence the NMVOC
                       emission coefficients for smaller units are likely to be higher than for large plants. Also
                       wood stoves, due to their largely inefficient combustion of the fuel, have particularly high
                       emission rates of VOCs. For these reasons, an understanding of commercial and
                       residential activities are key to the estimation of these greenhouse gases, particularly in
                       non-OECD countries where residential consumption of wood and other vegetal fuels is
                       commonly high.
                       Extensive emission factor data for non-methane volatile organic compounds (NMVOCs)
                       from energy combustion sources are available from most of the sources listed above. In
                       some older sources total volatile organic compounds, including methane have been
                       considered together. The recent work of the CORINAIR programme, the U.S. EPA
                       sources cited above, and most other more current sources distinguish both NMVOC and
                       methane in emission factors and emission estimates. Analysts should be careful to
                       understand the exact category of pollutant being specified when selecting emission factor
                       data. There is considerable uncertainty in most available information on NMVOC
                       emissions as is the case for methane.
                       The CORINAIR and U.S.  EPA factors show rough agreement on most categories of fuel
                       combustion, though both acknowledge considerable uncertainty. These data highlight the
                       importance of small combustion facilities as the main energy-related source of emissions,
                       but emission factor data for small facilities is also particularly unreliable. In any case, a
                       review of the literature confirms that NMVOCs from energy combustion (excluding
                       traditional biomass fuels)  is a relatively minor source of the total NMVOC emissions in any
                       given country or region.
                        1.5.6  Priorities  For  Future  Work

                        Data for Non-OECD Regions of the World
                        A high priority for follow-up work is to develop representative energy technology and
                        emission factor data for developing countries and other non-OECD regions of the world.
                        Emission factor data are likely to differ significantly among OECD and non-OECD regions
                        due to differences in types of fuels, combustion technologies, their vintage, their size and
                        operating conditions.

                        Uncertainty in Emission Factor Data

                        Emission factor data are normally presented as single point estimates. In fact, emission
                        factors are characterized by a great deal of variation around these point estimates.
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                                                                                EMISSIONS  FROM  ENERGY
                  Therefore, it would be preferable to have emission factor data presented with appropriate
                  ranges, as well as with accompanying statistics such as representative operating conditions.
                  These statistics should help relate the  range of emission factors to the associated
                  operating conditions.

                  Priorities by Gas

                  Emission factor data are particularly weak for N2O, CH4, NMVOC and CO. Monitoring
                  and measurement studies for these gases to improve the base emission factor data would
                  further the development of complete greenhouse gas inventories. The extent to which it
                  is necessary to fill data gaps depends upon the importance of these greenhouse gases in
                  national inventories.

                  However, CH4 and N2O emissions from stationary combustion sources (excluding
                  "traditional" biomass fuel burning) are a small share of total emissions, although  a few
                  specific technologies appear to have higher emission rates and may warrant extensive
                  study.

                  Similarly, NMVOC and CO can be quite significant in areas where wood or vegetal fuels
                  make up a major share of total energy  consumption. Again, these are areas with substantial
                  "traditional" biomass fuel consumption, discussed in the next section.

                  Development of Simplified Workbook Methods

                  As noted several times in  this chapter,  the non-CO2 gases do not lend themselves to
                  simple "top-down" aggregate emissions estimation. Nonetheless, the IPCC and parties to
                  the Framework Convention on  Climate Change are committed to providing methods
                  which are both comprehensive over all GHGs and accessible to all participating  countries.
                  Further work is needed to define default methods for estimating the non-CO2 gases from
                  fuel combustion. This may require development of a "mid-level" approach which
                  incorporates more detail than the national top down CO2 approach, but provides an
                  intermediate level of detail which can capture the most important variations  by technology
                  without going directly to the most detailed level of technology information which may be
                  difficult for some countries to obtain.

                  Reconciling Energy and ISIC Categories with Engineering-Technology
                  Category Definitions

                  A priority for those countries where extensive emission data bases are being developed is
                  a means of relating categories used in IEA energy statistics, a:> well as more detailed ISIC
                  categories to standard  engineering-technology or process category definitions. One key
                  example is the ongoing effort to reconcile the proposed IPCC source category structure
                  with the engineering/technology based structure in CORINAIR. This  is discussed in Volume
                  I: Reporting Instructions.
PART 2
                                                                                                                   1.59

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EMISSIONS FROM  ENERGY
               1.6     Burning Traditional  Biomass  Fuels
                        1.6.1  Overview
                        For all burning of biomass fuels, the IPCC methodology requires that net: CO2 emissions
                        are treated as zero in the energy sector. Some biomass fuels are sustainably produced, in
                        which case the actual net emissions are zero. However, even if all or part of the biomass
                        fuel burned is extracted unsustainably from existing biomass stocks (e.g., forests), it would
                        be difficult to determine, at the point of combustion, what fraction actually represents net
                        emissions. Therefore, net CO2 emissions, which are reflected in reductions in biomass
                        stocks, are accounted for in the Land Use Change and Forestry section of the
                        methodology.23 However, other (non-CO2) gases are emitted from  burning of biomass
                        fuels. Emissions of these gases (e.g., methane - CH4, carbon monoxide - CO,  nitrous oxide
                        - N2O, and oxides of nitrogen - NOX) are net emissions and are accounted for as energy
                        emissions. This section provides a method for calculating emissions  of these non-CO2
                        gases from burning of traditional biomass fuels.
                        Burning of "traditional biomass" is intended to include all traditional, small-scale use of
                        biomass fuels, such as cook stoves and open fires. It also includes the production as well as
                        consumption of charcoal in small scale traditional processes. In these conditions, emissions
                        can be estimated using emission ratios of CH4 and other gases to total carbon oxidized in
                        the biomass, as is done in the various non-energy types of open burning. Non-CO2 trace
                        gas emissions from commercial  use of biomass in large-scale combustion facilities or other
                        technologies for converting energy, are treated elsewhere in the energy combustion
                        chapter. This is because the recommended methods for calculating  emissions for these
                        source types are different from this proposed method for traditional, small-scale bioenergy
                        use. Emissions from large-scale facilities are very much a function of the particular
                        technology used and are treated very much like emissions from stationary fossil fuel
                        combustion -- with specific emission factors for each technology/fuel combination.
                        Emissions from traditional biomass fuel use also vary significantly based on technology,
                        operating conditions, etc. However, available data often does not support a technology
                         specific approach for traditional biomass fuel use. Therefore, the emission ratios approach
                         is provided as a common method for crude estimation which can be used by all national
                         experts.
                         This separation between  commercial and traditional biomass does introduce the possibility
                         of double counting some biomass energy use. Care should be taken to ensure that the
                         "commercial" component of bioenergy use is carefully defined and deducted from  total
                         bioenergy consumed before doing the calculations of emissions from traditional biomass
                         fuel use described in this section. It should also be noted that other possibilities for double
                         counting of emissions from biomass fuels exist in the methodology. Agricultural residues
                         and dung are two of the traditional fuels included in this section. Both are also sources of
                            23 For  policy analysis  purposes  in the energy sector, it may be very important to
                         consider the net CO2 emissions from biomass fuel burning as an energy related emission.
                         This can facilitate the comparison of biomass fuel combustion with other energy options
                         on the basis of CO2 or total GHG emissions. It is possible to reallocate the implied CO2
                         emissions to biomass burning for such analytic purposes.  However, it is essential, for
                         consistency, that all national inventories be reported as specified in the IPCC Guidelines,
                         that is, no net CO2 emissions are counted for biomass burning.
   1.60

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                                                                                EMISSIONS  FROM ENERGY
                 emissions calculated in the agriculture section. Some portion of agricultural residues may
                 be burned in the fields and produce the same set of trace gases in that situation. Dung is
                 treated as a potential source of methane emissions from anaerobic decomposition in the
                 calculation of emissions from animal wastes. In both cases it is the responsibility of users of
                 this methodology to ensure that these materials are allocated to their different uses and
                 not counted in both places.

                 For traditional biomass fuels, the approach is essentially the same as that used for non-
                 CO2 trace gases from all burning of unprocessed biomass, such as field burning of
                 agricultural  residues and savanna burning (Chapter 4: Agriculture) and open burning of
                 cleared forests (Land use change and forestry, Chapter 6). For all these activities there is a
                 common approach in the proposed methodology, in that crude estimates of non-CO2
                 trace gas emissions can be based on ratios to the total carbon released. The carbon trace
                 gas releases (CH4 and CO) are treated as direct ratios to total carbon released. To handle
                 nitrogen trace gases ratios of nitrogen to carbon in biomass fuels are first used to derive
                 total nitrogen released. Then emissions of N2O and NOX are based on ratios to total
                 nitrogen released. Default values for non-CO2 trace gas emission ratios are provided,
                 including ranges which emphasize their uncertainty. However, the basic calculation
                 methodology requires that users select a best estimate value.24
                 1.6.2  Recommended  Methodology

                 Calculations: There are two basic components to the calculation. First, it is necessary to
                 estimate the amount of carbon released to the atmosphere from biomass fuel burning.
                 These carbon releases are not net emissions, but are needed to derive non-CO2 trace gas
                 emissions which are net emissions. The activity data required are the annual consumption
                 of the various types of biomass fuels. Box I provides some suggestions for developing
                 these data. Based on the type of fuel burned, the amount of carbon released can be
                 calculated (a reflection of carbon content and combustion efficiencies, see Table A). The
                 second component is the same as for other biomass burning categories -- emission ratios
                 are applied to estimate the amount of non-CO2 trace gas released based on the amount of
                 carbon released (Box 2)
                 Part I: Total Carbon Released. First, for combustion by fuel, the mass of fuel as dry
                 matter is converted to carbon units, and  second, an efficiency of burn is assigned. The
                 general equation for estimating CO2 emissions is:
                        Emissions from Biomass Fuel (by type) = Total Fuel Consumed (10 mt dm)
                             X Carbon Fraction X Fraction Oxidized (combustion efficiency)
                 For emissions from charcoal production a single factor is applied based on total carbon
                 released in charcoal production. One estimate indicates that the amount of carbon
                 released during charcoal production roughly equals the carbon in charcoal consumed. In
                 other words, roughly half of the original carbon in the wood is lost during charcoal
                      Emissions inventory developers are encouraged to provide estimates of uncertainty
                 along with these best estimate values where possible, or to provide some expression of
                 the level of confidence associated with various point estimates provided in the inventory.
                 Procedures for reporting  this uncertainty or  confidence information  are  discussed in
                 Volume I: Reporting Instructions.
PART 2
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EMISSIONS FROM  ENERGY
                       manufacture.25 Therefore, to account for this release, as a default value, one could simply
                       use the estimated release of carbon from charcoal burning as the estimate of carbon
                       released from charcoal production.
                       Part 2: Non-CO2 Trace Gas Emissions. Once the carbon released from biomass fuel
                       burning has been estimated, the emissions of CH4, CO, N2O, and NOX can be calculated
                       as follows.26 The amount of carbon released due to burning is multiplied by the emission
                       ratios of CH« and CO relative to total carbon emissions to yield total emissions of CH4
                       and CO (each expressed in units of C). The emissions of CH, and CO are multiplied by
                        16/12 and 28/12, respectively, to convert to full molecular weights.

                                                             Box I
                                                 FUEL CONSUMPTION ACCOUNTING

                       For traditional biomass fuel use, direct consumption statistics are often incomplete or
                       unavailable. Large amounts of traditional fuels used may not be traded through normal
                       commercial fuel markets. Instead they may be traded in the informal sector or directly
                       gathered by consumers.  In this situation, it is often considered  more accurate to base fuel
                       consumption estimates on surveys of household and small commercial fuel use patterns. In
                       many countries, such surveys have produced rules of thumb concerning per capita use of
                       traditional fuels (charcoal, fuelwood, dung, etc.). Survey results may be available as national
                       averages, or broken down between rural and urban populations, or by region within
                       countries. Users of this methodology may determine this to be the most reliable approach
                       for all or part of biomass fuel consumption. In that case, available values for per capita
                       consumption of biomass fuels should be documented and multiplied  by population to
                       obtain total consumption values by fuel type.


                       To calculate emissions of N2O and NOX, first the total carbon  released is multiplied by the
                        estimated N/C ratio of the fuel by weight (default values for biomass fuels are provided in
                        table A) to yield the total amount of nitrogen (N) released. The total N released is then
                        multiplied by the ratios of emissions of N2O and NOX relative  to the N content of the fuel
                        to yield emissions of N2O and NOX (expressed in units of N). To convert to full molecular
                        weights, the emissions of N2O and NOX are multiplied by 44/28 and 30/14, respectively.27
                          75 Delmas,  1993.  Based on  measurements  indicating that 26%  by weight of input
                        fuelwood (dm) was produced as charcoal, with 87% carbon.  This results in about  1/2 the
                        carbon in original biomass remaining in charcoal, with  1/2 released during charcoal
                        production.  Hall  (1993) suggests much different values assuming that only 12.5% of dry
                        biomass in original wood is produced as charcoal and that carbon content of traditionally
                        produced charcoal ranges from 60-80%. This would indicate that less than 25% of carbon
                        in original dry biomass is incorporated  into charcoal produced.  Thus, 75+% of carbon is
                        released in production.  Additional work is needed to resolve these differences.
                          26
                             From Crutzen and Andreae, 1990.
                          27 There is an inconsistancy in the methodology in the treatment of the full molecular
                        weight of NO*. In fossil energy and industry discussions NOX is expressed as though all of
                        the N were in the form of NOj. In biomass burning literature, (e.g., Crutzen and Andreae,
                        1990)  NOX is  often  discussed  as  though the emissions were in  the  form  of  NO.
                        Therefore, the biomass  burning discussions in these  Guidelines convert  NOX-N to full
                        weight using the conversion factor  (30/14) for NO.  All other references to NOX are
                        based on the full weight of NO2 (i.e., the conversion factor from NOX-N would be 46/14).
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                                                                                 EMISSIONS  FROM  ENERGY
                 The non-CO2 trace gas emissions from burning calculation is summarized as follows:
                         CH4 Emissions = (carbon released) x (emission ratio) x 16/12
                         CO Emissions = (carbon released) x (emission rai:io) x 28/12
                         N2O Emissions = (carbon released) x  (N/C ratio) x (emission ratio) x 44/28
                         NOX Emissions = (carbon released) x  (N/C ratio) x (emission ratio) x 30/14
TABLE 1-19
BIOMASS FUELS DEFAULT DATA
Fuel Type
Fuelwood
Charcoal Consumption
Charcoal Production
Dung
Agricultural Residues
Carbon Fraction
0.45-0.5
0.87
0.45-0.5
0.36-0.42
0.4-0.48
Nitrogen-Carbon (N/C)
Ratioz
0.01
}
0.01
)
0.01-0.02
Combustion Efficiency
87
88
30
85
88
                    Sources:  Delmas and Ahuja, 1993; 2 Crutzen and Andreae, 1990."' Delmas, I993b
                     These are general default values for crop residues. Specific carbon fraction and N/C ration data for
                    residues from individual crops are provided in the agricultural burning discussion in chapter 4. If
                    consumption data on biomass fuels are specific by crop type, these crop specific values can be used.
PART 2
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EMISSIONS FROM  ENERGY
                                                                Box 2
                                                     TRACE GAS EMISSIONS RATIOS

                        Emissions of CHt, CO, N2O and NOX from burning of traditional biomass fuels (and other types of
                        blomass burning associated with forest clearing and agriculture)  are generally estimated by first
                        calculating the total carbon emitted (mostly as CO2) from combustion and applying a series of ratios.
                        First, a ratio of nitrogen to carbon in fuel is applied to estimate total nitrogen released. Then specific
                        ratios of CH< and CO to total carbon, and N2O and NOX to total nitrogen are used  to estimate
                        these trace gas emissions.  Crutzen and Andreae (1990) provided a range of values considered
                        representative of biomass burning generally.

                                   Compound  Ratios

                                   CH<     0.01      (0.007-0.013)

                                   CO      0.10      (0.075-O.I25)

                                   N2O     0.007    (0.005 - 0.009)

                                   NO*     0.121     (0.094-0.148)

                                  Source: Crutzen and Andreae.  1990

                         More recently, Lacaux et al.(!993) have suggested a lower emissions ratio range for CO: 0.06 (0.04-
                        0.08).
                         Delmas (I993a) and Delmas and Ahuja (1993) have developed more specific ratios for CH, from
                        different types of biomass burning, including values for specific biomass fuels and open burning from
                        forest clearing and agriculture. Delmas and Ahuja,  1993, also provide a ratio for estimating methane
                        from the charcoal production process. This value is much higher than the Crutzen and Andreae
                         range for relatively  open burning, and should be used to estimate what could be  a significant
                         methane source in many countries. Fuel values are shown below.
                               Fuel Type

                               Fuelwood
                                 Ratio - C-CH^total C

                                 0.012 (0.009-0.015)
                                                         0.005 (0.003-0.007)

                                                         0.017
                                                         0.005 (0.0014-0.0085)

                                                         0.063 (0.04-0.09)
      Agricultural Residues

      Dung

      Charcoal combustion

      Charcoal production

These more recent values are considered more accurate than the Crutzen and Andreae ranges
where available for individual components of biomass burning.
 1.64

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                                                                              EMISSIONS FROM ENERGY
       1.7    Greenhouse  Gas  Emissions  from  Mobile
                Combustion
                I .7.  I  Overview

                This section discusses emissions of greenhouse gases from mobile sources, including
                carbon dioxide (CC>2), carbon monoxide (CO), nitrogen oxides (NOX), methane (CH4),
                nitrous oxide (N2O), and non-methane volatile organic compounds (NMVOCs). Emissions
                from mobile sources are most easily estimated by major transport activity, i.e., road, air,
                rail, and ships. Several major fuel types need to be considered, including gasoline, diesel, jet
                fuel, aviation fuel, natural gas, liquified petroleum gas, and residual fuel oil. Road transport
                accounts for the majority of mobile source fuel consumption (e.g., 82% in 1988 for the
                OECD), followed by air transport (about 13%). This suggests that the primary emphasis in
                developing emission inventories should be placed on  road vehicles, followed by aircraft.
                As a one of the major energy consuming sectors, globally and in most countries, transport
                is a significant source  of CO2 emissions. As discussed previously, these emissions should
                be accounted for in the "top-down" IPCC Reference Approach to CO2 from fuel
                combustion described earlier. However, it is also useful to develop more detailed
                information about the role of specific end use activities, such as mobile sources, in causing
                CO2 emissions. National experts  are therefore encourage to also calculate CO2 emissions
                at a more detailed level (as described in this section for transport) and to aggregated these
                estimates up for comparison with the Reference Method. Therefore, the discussion in this
                section includes information needed to estimate CO2 emissions as well as other gases at a
                detailed level.
                Motor vehicles release a large portion of total anthropogenic NOX emissions. These
                emissions are related to air-fuel mixes and combustion temperatures, as well as pollution
                control equipment. For uncontrolled vehicles, NOX emissions from diesel-fueled vehicles
                are generally lower than from gasoline-fueled vehicles and lower from heavy duty vehicles
                (HDV) on an emissions per ton/kilometer basis than  light duty vehicles (LDV). HDV still
                contribute significant emissions and are more difficult to control than light duty vehicles.
                The majority of CO emissions from fuel combustion comes from motor vehicles. CO
                emissions are a function of the efficiency of combustion and post-combustion emission
                controls. Emissions are highest when air-fuel mixtures are "rich," with less oxygen than
                required for complete combustion. This occurs especially in idle, low speed, and cold start
                conditions in spark ignition engines.
                CH4 and NMVOC emissions are  a function of the methane content of the motor fuel, the
                amount of hydrocarbons passing  unburnt through the engine, and any post-combustion
                control of hydrocarbon emissions, such as use of catalytic converters. In uncontrolled
                engines, emissions of unburned HC, including CH4, are lowest when the combustion
                conditions (quantity of hydrogen, carbon, and oxygen present) are exactly right for
                complete combustion. They are generally highest in low speed and engine idle conditions.
                Poorly tuned engines (typical of many developing countries) may have particularly high
                output of total HC, including CH4. Emissions are also dependent on  engine type, emission
                controls and the fuel combusted.
                N2O emissions from  vehicles have only recently been studied in detail. Emissions from this
                source are still thought to be small relative to total anthropogenic emissions.  Emission
                rates are, however, substantially higher when some emission control technology
PART 2
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EMISSIONS FROM ENERGY
                       (especially catalysts on road vehicles) are used, and this could cause the total emissions to
                       grow in the future.

                       Emission control policies adopted in many OECD member countries, will substantially
                       reduce CO, NMVOC, CH4, and NOX emissions per automobile in these countries, but
                       may cause N2O emissions to increase.

                       Organization of this section

                       The next sub-section provides a discussion of the basic inventory methodology
                       recommended for this mobile source emissions. Following illustrative information on
                       emission factors is provided. This is summarized from a 1991 document, but useful in
                       illustrating the range of mobile source types of concern and rates of emissions of various
                       gases. Subsequently, some more recent information, developed by expert advisory groups
                       to the IPCC/OECD programme, is provided on two direct GHGs - N2O and CH4. A short
                       subsection discusses indirect GHGs - NOX, CO and NMVOC. No new work has been
                       done within the IPCC/OECD programme on these gases, but considerable detailed
                       information is available from other national and international emissions inventory
                       programmes. Some key references to this body of technical work are provided. A final
                       sub-section suggests some priorities for future work on GHG emissions from mobile
                       sources.
                       1.7.2  Basic  Inventory Method:
                       Emissions
Mobile  Source
                       Estimation of mobile source emissions is a very complex undertaking that requires
                       consideration of many parameters, including information on such factors as:
                       •   transport class
                       •   fuel consumed

                       •   operating characteristics
                       •   emission controls

                       •   maintenance procedures

                       •   fleet age

                       •   other factors

                       The need for data on several parameters and the wide variety of conditions that can affect
                       the performance of each category of mobile sources makes it very difficult to generalize
                       the emission characteristics in this area. This area is so complex that is difficult even for
                       countries with extensive experience to develop highly-precise emission inventories.

                       Nevertheless, a basic emission estimation methodology was developed and included in the
                       in the report of the OECD Experts Meeting in which was circulated to IPCC national
                       experts as a starting point for the methods development programme (OiECD, 1991). This
                       basic discussion is still useful and repeated with few changes in this section. The method is
                       consistent with the calculations  carried out in those countries which already have detailed
                       mobile source emissions inventory data bases. It is  presented in a somewhat simplified,
                       aggregate form to assist countries, with limited experience estimating emissions from
                       mobile sources, in getting started.

                       In order to develop estimates for greenhouse gas emissions from mobile sources, basic
                       information is required on the types of fuels consumed in the transport sector, the
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                                                                                EMISSIONS FROM ENERGY
                combustion technologies that are used to consume the fuels, operating conditions during
                combustion, and the extent of emission control technologies employed during and after
                combustion. The basic calculation for estimating these emissions can be expressed as:
                                          Emissions = £ (EFab<: x Activityabc)
                where:  EF =    emissions factor
                        Activity = amount of energy consumed or distance traveled for a given mobile
                        source activity
                        a =     fuel type (diesel, gasoline, LPG, bunker, etc.)
                        b =     vehicle type (e.g., passenger, light duty or heavy duty for road vehicles)
                        c =     emission control
                Based on this formula, the following basic steps are required to estimate mobile source
                emissions:
                •    Determine the amount of energy consumed by fuel type for all mobile sources using
                     national data or, as an alternative, IEA or UN international data sources (all values
                     should be reported in gigajoules).
                •    For each fuel type, determine the amount of energy that is consumed by each vehicle
                     type, e.g., light-duty gasoline vehicles, etc. (all units are in gigajoules). If distance
                     traveled is the basis, determine the total distance traveled by each vehicle type. In
                     this case; the energy consumption associated with these distance travelled figures
                     should be calculated and aggregated by fuel for comparison with national energy
                     balance figures.  If necessary, further subdivide each vehicle type into uncontrolled and
                     key classes of emission control technology.
                •    Multiply the amount of energy consumed, or the distance traveled, by each vehicle,
                     or vehicle/control technology, category by the appropriate emission factor for that
                     category. Data presented in the next section (Illustrative Emission Factors) can be
                     used as a starting point. However, national experts are encouraged to consult other
                     data sources referenced in this chapter and locally available before determining
                     appropriate factors for a particular country.
                •    Emissions can be -summed across all fuel and technology type categories, including for
                     all levels of emission control, to determine total emissions from mobile source-
                     related activities.
                Regardless of the specific methodology that is used to determine emissions, it is important
                to remember that there is a substantial amount of uncertainty surrounding the estimation
                of emissions from mobile sources. National experts are encouraged to provide indications
                of uncertainty in their estimates as described in Volume I: Reporting  Instructions.

                Data Sources
                Emission factors (such as those in Tables 2-20 through 2-31) can only be used if energy
                consumption can be adequately characterized by the fuel and vehicle/control technology
                categories.  For example, for transportation needs, information is required on the
                 percentage of light-duty versus heavy-duty vehicles by fuel type (gasoline- versus  diesel-
                fueled) and the extent of emission controls for each  category. There is no single  data
                 source that comprehensively provides all relevant information. There are several sources,
                 however, that can help to determine this information.
PART 2
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                       For example, activity data on vehicle fleet characteristics will be needed. There are two
                       main international sources of data available on transport, both of which are recommended
                       to be used as the international point of reference. For road transport, both the UNECE
                       (Annual Bulletin of Transport Statistics for Europe, e.g., 1989, Geneva) and the International
                       Road Federation (World Road Statistics, e.g., 1990, Washington, D.C.) provide annual data
                       on various aspects of vehicle fleets and traffic conditions. While the former is more
                       detailed for the various modes of transport,  it is available for Europe only. The latter is
                       worldwide in coverage but provides only a few key statistics. These include data on
                       vehicles in use, road traffic, motor fuels, and data on the flows of vehicles produced and
                       sold (imports and exports) among countries. Individual regional and national data sources
                       can also be used and may in fact be more disaggregate and up-to-date than these
                       international data sources.
                       Information on energy consumption in the transport sector is also needed to determine
                       emissions. As discussed earlier, the most reliable sources for international energy statistics
                       are the International Energy Agency and the UN Statistical Division, where data on
                       transport activities are detailed by fuel type and basic transport mode. These data are
                       available for most mobile source energy consumption in the world. National energy data
                       sources may be preferable to these international sources but the reporting definitions and
                       conventions of the IEA energy balance should be used to summarise these energy data.
                       This provides a check for internal consistency of the energy assumptions used to estimate
                       emissions from mobile source combustion.
                        1.7.3  Illustrative  Emission  Factors

                       This section summarizes results of a detailed analysis of mobile source emission factors for
                       gases contributing to global warming which was carried out in 1991. A more detailed
                       discussion of the methods and assumptions used can be found in OECD 1991. It has not
                       been possible, in the preparation of this Reference Manual, to update this earlier analysis in
                       a systematic way. The results are still useful in illustrating the range of emission rates from
                       different types of vehicles and how those rates vary by vintage and control technology. It is
                       also very useful in providing side by side expressions of the same emission factors in three
                       different forms. Therefore, the results are summarized in this section, as originally
                       presented, for illustrative purposes.

                       However, for actual calculations of national emissions, users are encouraged to also
                       consult a range of more recent and more detailed information sources. Particularly for
                       indirect GHGs, more comprehensive and up-to-data sources as well are available based on
                       programmes outside the GHG emissions area. More recent data on some gases, and
                       references to other detailed data sources are provided in the gas  by gas subsections later
                       in this section.

                       Emission factor estimates are presented for CO2, CO, NOX, N2O, methane, and non-
                       methane VOCs for several classes of highway vehicles, railway locomotives, ships and
                       boats, farm and construction equipment, and aircraft. All emission factor data are stated
                       on the basis of full molecular weight of the respective pollutant; NOX factors are stated as
                       NOZ.

                       Road Vehicles - Conventional Fuels

                       Technical Approach

                       The emissions estimates for NOX, CO, methane, and NMVOC from highway vehicles are
                       based on the U.S. EPA's MOBILE4 model (EPA, 1989). MOBILE4 calculates exhaust
                       emission factors for U.S. vehicles using gasoline and diesel fuel, based on the year in which
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                                                                               EMISSIONS  FROM ENERGY
                they were manufactured. For gasoline vehicles, it also calculates VOC emissions due to
                evaporative, running, and refueling losses (VOC emissions from diesel vehicles due to
                these causes are negligible).

                Assumptions
                Specific U.S. model years were used to represent the different possible control
                technologies. Emissions were calculated for a five year old vehicle of each type (approxi-
                mately halfway through their useful lives). Similarly, emissions estimates for advanced-
                technology vehicles were based on 1990 model vehicles, calculated in 1995. Table 1-20
                shows the correspondence between technology types and the U.S. model years used to
                represent them in the model. The conditions chosen for the modeling were "typical"
                values of 75 °F, with a diurnal range from 60 to 85 °F (24±8 °C), and Reid vapor pressure
                of gasoline at 9.0 PSI (62 kPa). Average speed was taken as the MOBILE4 default of 31.4
                km/hr, typical of uncongested urban driving. An effective inspection/  maintenance and anti-
                tampering program, was assumed to be in place.
                Since MOBILE4 does not estimate N2O or CO2 emissions, these were estimated
                separately. CO2 emissions were calculated from typical fuel economy data for U.S. vehicles
                for representative model years  in which the technology was used together with the
                average carbon content for each type of fuel.28 Fuel economy estimates for heavy-duty
                gasoline and diesel trucks, are from Machiele, (1988), and from Weaver and Turner (1991)
                for other vehicle classes. The specific fuel economy value assumed for U.S. vehicles in each
                case is shown in the tables. The estimated vehicle fuel economies were also used to
                calculate fuel-specific (g/kg fuel) and energy-specific (g/MJ)2' emission factors for all of the
                pollutants. The CO2 factors on  an energy input (g/MJ) wen; taken from Grubb (1989); all
                other emission factors are from Turner and Weaver (1991). Since emissions and fuel con-
                sumption tend to vary in parallel (vehicles and operating modes causing high emission rates
                also tend to result in high fuel consumption, and vice versa), these energy-specific emission
                factors are expected to be more generally applicable than the factors in grams/km.
                N2O emissions factors were developed based on the limited available test data. Prigent and
                Soete (1989), Dasch (1991), Ford (1989-1991), and Warner-Selph and Smith  (1991) gave
                N2O emissions for light-duty gasoline vehicles which were divided into four groups of
                technologies: uncontrolled, oxidation catalyst, early three-way catalyst, and modern three-
                way catalyst technologies. For light-duty gasoline trucks and motorcycles, fuel-specific N2O
                emissions were assumed to be  the same as for the corresponding passenger car
                technology. No data on N2O emissions from heavy-duty gasoline trucks were available, but
                they were assumed to emit at the same rate per unit of fuel burned  as passenger cars
                having similar technology. However, since these trucks undergo a heavier duty cycle, and
                experience fewer cold-starts, it was considered  more appropriate to use N2O emission
                factors based on the U.S. highway fuel economy test (HFFf) rather than  the cold-start FTP
                procedure.  Fuel-specific N2O emissions for passenger cars  in the HFET procedure were
                obtained from the same data sources listed above. Dietzmann, Parness, and Bradow (1980)
                reported N2O emission factors for heavy-duty diesel vehicles. No N2O emissions data
                   28As is the convention throughout these Guidelines, CO2 emissions are calculated to
                 include the carbon emitted as CO and as VOC.   The rationale for  this approach  is
                 explained in the Introduction.

                   29 MJ=megajoule=l06 joules.  Energy-specific emission factors were based on the lower
                 heating value of the fuel in each case.
PART 2
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EMISSIONS  FROM  ENERGY
                       were available for light-duty diesel vehicles, but they were assumed to have the same fuel-
                       specific emission rates as for diesel passenger cars.

                       Results of this analysis are presented by categories defined by the U.S. EPA as listed below:

                       Table 1-21: Light-duty gasoline passenger cars - vehicles with rated gross weight less
                       than 8,500 Ib (3,855 kg) designed primarily to carry 12 or fewer passengers. Five levels of
                       gasoline-vehicle control technology are shown:

                        I    Uncontrolled (still typical of most vehicles around the world)

                       2    Non-catalyst emission controls - including modifications to ignition timing and air-fuel
                            ratio to reduce emissions, exhaust gas  recirculation (EGR), and air injection into the
                            exhaust manifold.

                       3    Oxidation catalyst systems normally including many of the same techniques, plus a
                            two-way catalytic converter to oxidize HC and CO.

                       4    "Early" three-way catalyst results representative of vehicles sold in the U.S. in the
                            early to mid '80s, which were mostly equipped with carburetors having electronic
                            "trim".

                       5    "Advanced" three-way catalyst values based on current U.S. technology vehicles, using
                            electronic fuel injection under computer control.
                       Table 1-22: Light-duty gasoline trucks - vehicles having rated gross vehicle weight less
                       than 8,500 Ib (3,855 kg), and which are designed primarily for transportation of cargo or
                       more than 11  passengers at a time, or which are equipped with special features for off-
                       road operation. They include most pickup trucks, passenger and cargo vans, four-wheel
                       drive vehicles, and derivatives of these. The technology classifications used are the same as
                       those for gasoline passenger vehicles.

                       Table 1-23: Heavy-duty gasoline vehicles - manufacturer's gross vehicle weight rating
                       exceeding 8,500 Ib (3,855 kg). This includes  large pickups, vans and specialized trucks using
                       pickup and van chassis, as well as the larger  "true" heavy-duty trucks, which have gross
                       vehicle weights of eight short tons  or more. In the U.S., the large pickups and vans in this
                       category greatly outnumber the heavier trucks, so that the emission factors calculated by
                       MOBILE4, and fuel economy estimates, are more representative of these vehicles. Three
                       levels of emission control technology are shown:

                        I    Uncontrolled.

                       2    Non-catalyst emission controls, including control of ignition  timing and air-fuel ratio
                            to minimize emissions, EGR, and air injection into the exhaust manifold to reduce
                            HC and CO emissions.

                       3    Three-way catalyst technology presently used in the U.S. includes electronically-
                            controlled fuel injection, EGR, air injection, and electronic control of ignition timing,
                            as well as the catalyst itself.

                       Table 1-24: Light-duty diesel passenger cars - a diesel passenger car designed primarily
                       to carry fewer than 12 passengers, with gross vehicle weight less  than 8,500 Ib (3,855 kg).
                       Three levels of emission control technology are shown:

                        I    Uncontrolled

                       2    Moderate emissions control (achieved by changes in injection timing and combustion
                            system design).

                       3    Advanced emissions control utilizing modern electronic control of the fuel injection
                            system, and exhaust gas recirculation.
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                                                                                 EMISSIONS FROM  ENERGY
                 Table I-2S: Light-duty diesel trucks - light-duty diesel trucks defined like their gasoline
                 counterparts, including weight, utility, and off-road operation features. The technology
                 classifications are the same as those for diesel passenger car's.
                 Table 1-26: Heavy-duty diesel vehicles - the classification for heavy-duty diesel vehicles
                 is the same as for gasoline vehicles, but the characteristics of the U.S. vehicle fleets are
                 different. Heavy-duty diesel vehicles are primarily large trucks, with gross vehicle weight
                 ratings of 10 to 40 tons. Therefore, the MOBILE4 emission factors are more
                 representative of large trucks (and buses) than the smaller pickup and van-type vehicles,
                 and this is reflected in the fuel economy estimates. Three  levels of control are presented:
                 I    Uncontrolled.
                 2    Moderate control (typical of 1 983 U.S. engines).
                 3    Advanced control (for engines meeting U.S. 1 99 1  emissions standards)
                 Table 1-27: Motorcycles - The MOBILE4 emission factors for these vehicles are based
                 on the U.S. motorcycle population, which probably reflects higher average power ratings
                 and fuel consumption than for many developing countries. The factors for uncontrolled
                 motorcycles include a mixture of two-stroke and four-stroke engines, with the VOC
                 emissions due primarily to the two-strokes, and the NOX to the four-stroke engines. The
                 factors for motorcycles with  non-catalyst emission controls reflect four-stroke engines
                 only, as U.S. emission control regulations have essentially eliminated two-stroke engines
                 from the market.
                 Emission factors for certain greenhouse gas emissions from road vehicles can be
                 developed using the MOBILE4 computer model.' This model was the basis for most of
                 the emission factors presented in Tables 2-2 1 to 2-27, and can be used to calculate
                 average emission rates for any selected calendar year (from 1 960 to 2020) essentially by
                 aging the fleet and weighting the emission factors by the shares of distance travelled by
                 vehicles of various ages. The emission factors are estimated as a function of several
                 parameters, including: vehicle type; model year (technology); vehicle age and accumulated
                 mileage; percent of driving in cold start, hot start or stabilized conditions;

                 average speed; ambient temperatures; fuel volatility; and tampering rates with emission
                 control systems. Since *these variables can be manipulated by the user, the conditions can
                 be altered to reflect conditions in a variety of geographic regions and regulatory situations.

                 MOBILE4 calculates emission factors for total and non-methane hydrocarbons (HC and
                 NMHC), NOX and CO, and two fuels (gasoline and diesel). The emissions performance in
                 MOBILE4 for vehicles under various conditions is estimated based on years of extensive
                 testing of vehicles in use in the United States. The user can specify input data for the
                 particular region or country, and emission factors that are tailored to that particular
                 region will be estimated.

                 Several notes of caution  need to be given on the use of MOBILE4 for development of
                 greenhouse gas emission factors. First, the pollutant coverage is incomplete (including only
                 NOX, CO, VOC, and NMVOCs with methane as a calculated result of the  difference
                 between NMVOC and VOC).

                 Second, alternative fuel vehicles are not yet incorporated into the model. Supplementary
                 information must therefore be used to develop these factors should the fuel  mix in
                 transport activities require them. Any assumptions  used to build  these factors should be as
                 comparable as possible with those for conventional motor fuels.
PART 2
1.71

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EMISSIONS FROM ENERGY
                       Third, special attention must be given to the definition of MOBILE4 fleet assumptions to
                       include two-stroke engines in order to make the results useful to many non-OECD
                       nations. A substantial portion of the automobile fleets in countries of Eastern Europe and
                       perhaps in other parts of the non-OECD world are two-stroke engines. These engine
                       types have a substantially different emission profile than the standard (Otto) gasoline or
                       four-stroke engine which is predominant in the OECD. Fleet data on two-stroke engine
                       vehicle stocks will therefore be a first priority in understanding the necessary
                       modifications to MOBILE4 emission factor estimates, which have been largely developed
                       for OECD countries and regions.
                       1 The MOBILE4 Model and its User's Guide can be obtained from the U.S. National Technical
                       Information Service, U.S. Department of Commerce, Springfield, Virginia,  22161, United States.
TABLE 1-20
EMISSION CONTROL TECHNOLOGY TYPES AND U.S. VEHICLE MODEL
YEARS USED To REPRESENT THEM
Technology
Model Year
Gasoline Passenger Cars and Light Trucks
Uncontrolled
Non-catalyst controls
Oxidation catalyst
Early three-way catalyst
Advanced three-way catalyst
1963
1972
1978
1983
1990
Heavy-Duty Gasoline Vehicles
Uncontrolled
Non-catalyst control
Three-way catalyst
1968
1983
1991
Diesel Passenger Cars and Light Trucks
Uncontrolled
Moderate control
Advanced control
1978
1983
1990
Heavy Duty Diesel Vehicles
Uncontrolled
Moderate Control
Advanced control
1968
1983
1991
Motorcycles
Uncontrolled
Non-catalyst controls
1972
1990
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                                         EMISSIONS FROM ENERGY
TABLE 1-21
ESTIMATED EMISSIONS FACTORS FOR GASOLINE PASSENGER CARS

EMISSIONS
NOx
CH4
NMVOC
CO
N20
C02
Advanced Three- Way Catalyst Control; Assumed Fuel Economy: 1 1.9 km/I
Total - g/km
Exhaust
Evaporative
Refueling
Running loss
g/kg fuel
g/MJ
0.50
0.50
7.94
0.18
0.020
0.020
0.32
0.0072
0.66
0.26
0.11
0.15
0.14
10.48
0.24
3.14
3.14
49.87
1.13
0.019
0.019
0.30
0.0069
200
200
3172
69.3
Early Three-Way Catalyst; Assumed Fuel Economy: 9.4 km/I
Total - g/km
Exhaust
Evaporative
Refueling
Running loss
g/kg fuel
g/MJ
0.52
0.52
6.49
0.15
0.04
0.04
0
0
0
0.50
0.0113
0.67
0.25
0.12
0.16
0.14
8.36
0.19
3.12
3.12
38.93
0.88
0.046
0.046
0.57
0.0130
254
254
3172
69.3
Oxidation Catalyst; Assumed Fuel Economy: 6.0 km/I
Total - g/km
Exhaust
Evaporative
Refueling
Running loss
g/kg fuel
g/MJ
1.59
1.59
12.63
0.29
0.09
0.09
0
0
0
0.71
0.0162
1.75
1.13
0.19
0.21
0.22
13.90
0.32
12.98
12.98
103.07
2.34
0.027
0.027
0.21
0.0049
399
399
3172
69.3
Non-Catalyst Control; Assumed Fuel Economy: 6.0 km/I
Total - g/km
Exhaust
Evaporative
Refueling
Running loss
g/kg fuel
g/MJ
1.97
1.97
15.64
0.36
0.174
0.174
0
0
0
1.38
0.0314
3.15
2.14
0.45
0.29
0.27
25.01
0.57
23.8
23.8
188.99
4.30
0.005
0.005
0.04
0.0009
399
399
3172
69.3
Uncontrolled; Assumed Fuel Economy: 6.0 km/I
Total - g/km
Exhaust
Evaporative
Refueling
Running loss
g/kg fuel
g/MJ
2.14
2.14
16.99
0.39
0.174
0.174
0
0
0
1.38
0.0314
6.33
4.36
1.37
0.28
0.32
50.27
1.14
40.62
40.62
322.56
7.33
0.005
0.005
0.04
0.0009
399
399
3172
69.3
PART 2
1.73

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EMISSIONS FROM ENERGY
TABLE 1-22
ESTIMATED EMISSION FACTORS FOR LIGHT-DUTY GASOLINE TRUCKS.
EMISSIONS

NOx
CH4
NMVOC
CO
N2O
Advanced Three-Way Catalyst Control; Assumed Fuel Economy: 9.4 km/I
otal - g/km
Exhaust
Evaporative
Refueling
Running loss
g/kg fuel
g/MJ
0.67
0.67
8.36
0.19
0.04
0.04
0
0.50
0.0113
0.75
0.4
O.I
0.2
0.04
9.36
0.21
4.68
4.68
58.40
1.33
0.024
0.024
0.30
0.0068
C02

254
254
3172
69.3
Early Three-Way Catalyst; Assumed Fuel Economy: 6.8 krn/l
"otal - g/km
Exhaust
Evaporative
Refueling
Running loss
g/kg fuel
g/MJ
1.00
1.00
9.08
0.21
Oaa.07
0.07
0
0
0
0.64
0.0144
1.17
0.78
0.13
0.21
0.04
10.62
0.24
9.23
9.23
83.76
1.90
0.063
0.063
0.57
0.0130
350
350
3172
69.3
Oxidation Catalyst; Assumed Fuel Economy: 5.1 km/I
Total - g/km
Exhaust
Evaporative
Refueling
Running loss
g/kg fuel
g/MJ
Non-Catalyst; Assumed
Fuel Economy: 5.1 km/I
1.62
1.62
11.03
0.25
Total - g/km
Exhaust
Evaporative
Refueling
Running loss
g/kg fuel
g/MJ
Uncontrolled; Assumed
Fuel Economy: 5.1 km/I
2.82
2.82
19.19
0.44
0.09
0.09
0
0
0
0.61
0.0139
1.95
1.22
0.22
0.29
0.22
13.27
0.30
12.15
12.15
82.70
1.88
0.031
0.031
0.21
0.0048
466
466
3172
69.3

0.174
0.174
0
0
0
1.18
0.0269
Total
Exhaust
Evaporative
Refueling
Running loss
g/kg fuel
g>MJ

2.63
2.63



17.90
0.41
0.174
0.174
0
0
0
1.18
0.0269
4.55
3.01
0.9
0.34
0.29
30.97
0.70
28.81
28.81
196.09
4.46
0.006
0.006
0.04
0.0009
466
466
3172
69.3

8.54
4.98
2.92
0.32
0.32
58.13
1.32
44.55
44.55
303.23
6.89
0.006
0.006
0.04
0.0009
466
466
3172
69.3
 1.74

-------
                                        EMISSIONS FROM ENERGY
TABLE 1-23
ESTIMATED EMISSION FACTORS FOR HEAVY-DUTY GASOLINE VEHICLES

EMISSIONS
NOx
CH4 | NMVOC
CO
N2
-------
EMISSIONS FROM ENERGY
TABLE 1-24
ESTIMATED EMISSION FACTORS FOR DIESEL PASSENGER CARS

EMISSIONS
NOx
CH4
NMVOC
CO
N20
C02
Advanced Control; Assumed Fuel Economy: 1 0.6 km/I
Total - g/km
g/kg fuel
g/MJ
0.65
8.04
0.19
0.01
0.12
0.003
0.29
3.59
0.084
0.86
10.64
0.25
0.007
0.08
0.0019
258
3188
73.3
Moderate Control; Assumed Fuel Economy: 6.8 km/I *
Total - g/km
g/kg fuel
g/MJ
0.93
7.36
0.17
0.01
0.08
0.002
0.29
2.30
0.054
0.86
6.81
0.16
0.010
0.08
0.0019
403
3188
73.3
Uncontrolled; Assumed Fuel Economy: 5.1 km/I
Total - g/km
g/kg fuel
g/MJ
1.02
6.05
0.14
0.01
0.06
0.001
0.52
3.09
0.073
1.06
6.29
0.15
0.014
0.08
0.0019
537
3188
73.3
TABLE 1-25
ESTIMATED EMISSION FACTORS FOR LIGHT-DUTY DIESEL TRUCKS

EMISSIONS
NOx
CH4
NMVOC
CO
N2O
C02
Advanced Control; Assumed Fuel Economy: 7.7 km/I
Total - g/km
g/kg fuel
g/MJ
0.76
6.77
0.16
0.01
0.09
0.0021
0.42
3.74
0.09
0.98
8.73
0.21
0.009
0.08
0.0019
358
3188
73.3.
Moderate Control; Assumed Fuel Economy: 5. 1 km/I
Total - g/km
g/kg fuel
g/MJ
1.04
6.17
0.15
0.01
0.06
0.0014
0.42
2.49
0.06
0.98
5.82
0.14
0.014
0.08
0.0019
537
3188
73.3
Uncontrolled; Assumed Fuel Economy: 4.3 km/I
Total - g/km
g/kg fuel
g/MJ
I.4S
7.17
0.17
0.02
0.10
0.00
0.83
4.11
0.10
1.61
7.96
0.19
0.017
0.08
0.0019
559
3188
73.3
 1.76

-------
                                                                            EMISSIONS FROM ENERGY
TABLE 1-26
ESTIMATED EMISSION FACTORS FOR HEAVY DUTY DIESEL VEHICLES

EMISSIONS
NOx
CH4
NMVOC
CO
N2O
C02
Advanced Control; Assumed Fuel Economy: 2.8 km/I
Total - g/km
g/kg fuel
g/MJ

Total - g/km
g/kg fuel
g/MJ
5.01
16.27
0.38
0.06
0.19
0.005
1.26
4.09
0.10
6.8
22.09
0.52
0.025
0.08
0.0019
982
3188
73.3
Moderate Control; Assumed Fuel Economy: 2.8 km/I
11.94
38.41
0.90
0.07
0.23
0.01
1.7
5.47
0.13
8.28
26.64
0.63
0.025
0.08
0.0019
991
3188
73.3
Uncontrolled; Assumed Fuel Economy: 2.2 km/I
Total - g/km
g/kg fuel
g/MJ
16.79
42.86
1.01
O.I
0.26
0.01
2.99
7.63
0.18
8.54
21.80
0.51
0.031
0.08
0.0019
1249
3188
73.3
TABLE 1-27
ESTIMATED EMISSION FACTORS FOR MOTORCYCLES

EMISSIONS
NOx
CH4
NMVOC
CO
N2O
C02
Non-catalytic Control; Assumed Fuel Economy: 1 4.9 km/I
Total - g/km
g/kg fuel
g/MJ
0.53
10.52
0.24
0.15
2.98
0.07
2.2
42.9
0.97
13.2
261
5.9
0.002
0.04
0.0009
160
3188
69.3
Uncontrolled; Assumed Fuel Economy: 1 2.8 km/I
Total - g/km
g/kg fuel
g/MJ
0.19
3.23
0.07
0.329
5.60
0.13
6.5
III
2.5
23.8
405
9.2
0.002
0.04
0.0009
186
3172
69.3
                Road Vehicles - Alternative Fuels
                Alternative motor vehicle fuels such as natural gas, LP gas, methanol, and ethanol are
                presently being used in a limited way, and are the subjects of a great deal of research and
                development effort aimed at increasing their usage in the future. This section presents
                some preliminary estimates of the emissions to be expected from vehicles using these
                fuels, based on fuel properties and the limited emissions data available.30

                Natural gas
                Because natural gas is mostly methane, natural gas vehicles (NGVs) have lower exhaust
                NMVOC emissions than gasoline vehicles, but higher emissions of methane. There are no
                evaporative or running-loss emissions, refueling emissions and cold-start emissions are
                    Actual emission levels from these vehicles may be very different, and further testing is
                needed to confirm these estimates.
PART 2
1.77

-------
EMISSIONS  FROM  ENERGY
                        low, and have leaner fuel-air ratios. These conditions reduces both NMVOC and CO
                        emissions relative to gasoline vehicles. CO2 emissions from NGVs will be lower than for
                        gasoline vehicles, since natural gas has a lower carbon content per unit of energy. It
                        possible to attain increased efficiency by increasing the compression ratio. Optimized
                        heavy-duty NGV engines can approach diesel efficiency levels. NOX emissions from
                        uncontrolled NGVs may be higher or lower than comparable gasoline vehicles, depending
                        on the engine technology. NGV NOX emissions are more difficult to control using three-
                        way catalysts. N2O emissions from NGVs were not included.

                        Table 1-28 shows three types of NGVs: passenger cars, gasoline-type heavy-duty vehicles,
                        and diesel-type heavy-duty vehicles.31 Two sets of emission factors are ishown for each:
                        uncontrolled (typical of a simple  natural gas conversion, without catalytic converter or
                        optimization for emissions) and advanced control (reflecting an engine and catalytic
                        converter factory-produced and  optimized for natural gas). The estimates for the
                        passenger car and gasoline-type heavy duty vehicle are based on a gasoline-type engine,
                        converted to use natural gas. For the uncontrolled vehicles, no changes in the engine are
                        assumed beyond the fitting of a natural gas mixer and modified spark timing such that the
                        efficiency would be the same. For the vehicles with advanced control, a higher
                        compression ratio is assumed to give 15% better fuel efficiency.

                        For the diesel-type heavy-duty vehicles, the engine assumed is a diesel-type engine,
                        converted to lean. Otto-cycle operation using natural gas. The uncontrolled case reflects
                        no further optimization beyond the conversion, while the controlled case includes
                        extensive combustion optimization for NOX control  and an oxidation catalytic converter.

                        LPgas
                        LPG is primarily  propane (or a propane/butane mixture) rather than methane which
                        affects the composition of exhaust VOC emissions, but otherwise it similar to NG.
                        Evaporative and refueling emissions are virtually zero, and CO and exhaust NMVOC
                        emissions are usually lower than gasoline vehicles. The CO2 emissions should be
                        somewhat lower than gasoline, due to the lower carbon-energy ratio, and the higher
                        octane allows some increase in efficiency, although less than for natural gas.  NOX
                        emissions from LPG vehicles tend to be higher than for gasoline,  but can also be
                        controlled using three-way catalysts. N2O emissions  were not included.
                        Table 1-29 shows four categories of LPG vehicles. The engines and technologies
                        considered are the same as those for natural gas, except that the lean, diesel-derived
                        natural gas engine with propane  is not considered.
                        Methanol and ethanol. The two alcohols have similar properties, and are discussed together.
                        Development efforts have focussed primarily on mixtures of alcohols with gasoline, in
                        flexible fuel vehicles, capable of running on any combination of gasoline and up to 85%
                        methanol or ethanol. Engines and emission control systems are similar to those for
                        advanced-technology gasoline vehicles, and the overall energy efficiency and emissions
                        properties are similar. Table 2-30 shows estimated emissions for a vehicle of this type
                        using M85 (85%  methanol/15% gasoline) fuel. Also shown are some rough emissions
                        estimates for heavy-duty vehicles equipped with methanol or ethanol engines.
                           3lThe emissions considered are only those of the vehicle itself-additional emissions due
                        to, e.g.,  compression or liquefaction of gas for storage  on the vehicle, leakage from
                        pipelines, etc. are  not included, nor are the potential  emissions  credits  due to,  e.g.
                        production of methane from biomass. This is consistent with the trezitment of emissions
                        from vehicles using oil based fuels.
 1.78

-------
                                         EMISSIONS FROM ENERGY
TABLE 1 -28
ESTIMATED EMISSION FACTORS FOR LIGHT- AND HEAVY-DUTY NATURAL CAS VEHICLES
EMISSIONS
| NOx
CH4
NMVOC
CO
N2O
C02
Passenger Car
Advanced Control; Assumed Fuel Economy: I4.9km/Mj
g/km
g/kgfuel
g/MJ
0.5
10.3
0.21
0.7
14.5
0.29
O.OS
1.0
0.0?.
0.3
6.2
0.12

N/A
N/A
N/A
Uncontrolled; Assumed Fuel Economy: 6.5 km/MJ
g/km
g/kg fuel
g/MJ
2.1
19.0
0.38
3.5
31.6
0.63
0.5
4.5
0.09
4.0
36.1
0.72
N/A
N/A
N/A

133
2750
56.1

305
2750
56.1
Heavy-Duty Vehicles: Stoichiometrlc Engine (compare with gasoline)
Advanced Control; Assumed Fuel Eiconomy: 3.6 km/MJ
g/km
g/kgfuel
g/MJ .
2.6
13.0
0.26
3.0
15.0
0.30
0.20
1.0
0.02
1.0
5.0
0.10
N/A
N/A
N/A

550
2750
56.1
Uncontrolled; Assumed Fuel Economy: 2.2 km/MJ
g/km
g/kg fuel
g/MJ

5.7
17.4
0.35
10.0
30.6
0.61
1.4
4.3
0.09
12.0
36.7
0.73
N/A
N/A
N/A
900
2750
56.1
Heavy-Duty Vehicles: Lean Burn Engine (compare with diesel)
Advanced Control; Assumed Fuel Economy: 2.4 km/M 3
g/km
g/kg fuel
g/MJ
4.0
13.3
0.27
4.0
13.3
0.27
0.40
1.3
0.03
1.5
5.0
0.10
N/A
N/A
N/A

825
2750
56.1
Uncontrolled; Assumed Fuel Economy: 2.0 km/MJ
g/km
g/kg fuel
g/MJ
23.0
63.9
1.28
10.0
27.8
0.56
2.0
5.<>
0.11
8.0
22.2
0.44
N/A
N/A
N/A
990
2750
56.1
PART 2
                                                            1.79

-------
EMISSIONS FROM ENERGY
TABLE 1-29
ESTIMATED EMISSION FACTORS FOR LIGHT- AND HEAVY-DUTY LP GAS VEHICLES.

EMISSIONS
NOx
CH4
NMVOC
CO
N2O
C02
Passenger Car
Advanced Control
g/km
I/kg fuel
g/MJ
0.5
8.8
0.19
0.02
0.4
0.01
0.25
4.4
0.10
0.3
5.3
0.11
N/A
N/A
N/A
170
3000
63.1
Uncontrolled
g/km
g/kgfuel
g/MJ
2.1
17.7
0.38
0.18
1.5
0.03
3.5
29.S
0.64
8.0
67.5
1.45
N/A
N/A
N/A
356
3000
63.1
Heavy-Duty Vehicles: Stoichiometric Engine (compare with gasoline)
Advanced Control
g/km
g/kgfuel
g/MJ
2.6
11.2
0.24
0.1
0.4
0.01
0.70
3.0
0.07
1.0
4.3
0.09
N/A
N/A
N/A
695
3000
63.1
Uncontrolled
g/km
g/kgfuel
g/MJ
S.7
16.8
0.36
0.4
1.2
0.03
8.0
23.5
0.51
24.0
70.6
1.52
N/A
N/A
N/A
1020
3000
63.1
1.80

-------
                                                                             EMISSIONS FROM ENERGY
TABLE 1-30
ESTIMATED EMISSION FACTORS FOR LIGHT- AND HEAVY-OUTY METHANOL VEHICLES
EMISSIONS


NOx
CH4
NMVOC
CO
NiO

C02
Passenger Car (M85 Fuel)
Advanced Control
g/km
g/kg fuel
g/MJ
0.5
4.5
0.19
0.02
0.2
0.01
0.66
5.9
0.25
3.14
28.0
1.19
N/A
N/A
N/A

183
1632
69.7
Heavy-Duty Vehicle -Methanol-Diesel Engine- M 100 Fuel
Advanced Control
g/km
g/kg fuel
g/MJ
4.0
6.1
0.30
O.I
0.2
0.01
1.50
2.3
0.11
4.0
6.1
0.30

N/A
N/A
N/A

908
1375
68.8
                Non-Rood Mobile Sources
                Emission factors are provided for major non-road vehicle source categories including farm
                and construction equipment, railway locomotives, boats, and ships (all primarily equipped
                with diesel engines), jet aircraft, and gasoline-fueled piston aircraft in Table 1-31.
                Emission factors for diesel engines used in railway locomotives, farm equipment such as
                tractors and harvesters, construction equipment such as bulldozers and cranes, and diesel
                boats, are from Weaver (1988). These estimates are specilk to the U.S., may be applicable
                to other regions as well. N2O emission factors for off-road diesels are assumed to be the
                same as those for heavy-duty on-highway diesel engines.
                Large ocean-going cargo ships are driven primarily by large, slow-speed and medium-speed
                diesel engines, and occasionally by steam turbines and gas nurbines (the latter in high pow-
                er-weight ratio vessels such as fast ferries and warships). The number of vessels equipped
                with  steam or gas-turbine propulsion is small, however, since these vessels are unable to
                compete with the more efficient diesels in most applications. The results shown for NOX
                and CO are from Hadler (I990)32. N2O emissions for these engines were assumed to be
                the same, on a fuel-specific basis, as those for other heavy-duty diesels, and VOC
                emissions from these large diesels are probably negligible.
                   32Other sources consulted for comparison  are Melhus  (1990),  Bremnes  (1990),
                Alexandersson (1990)
PART 2
                                                                                                                   1.81

-------
EMISSIONS FROM  ENERGY
TABLE 1-3!
ESTIMATED EMISSION FACTORS FOR NON-HIGHWAY MOBILE SOURCES

UNCONTROLLED EMISSIONS
NOx
CH4
NMVOC
CO
N2O
C02
OCEAN GOING SHIPS
g/kgfuei
g/MJ
87
2.1
n/a
n/a
n/a
n/a
1.9
0.046
0.08
0.002
3212
77.4
BOATS
g/kg fuel
g/MJ
67.5
1.6
0.23
0.005
4.9
0.11
21.3
0.50
0.08
0.002
LOCOMOTIVES
g/kg fuel
g/MJ
74.3
1.8
0.25
0.006
5.5
0.13
26.1
0.61
0.08
0.002
3188
73.3

3188
73.3
FARM EQUIPMENT
g/kg fuel
g/MJ
63.5
1.5
0.45
0.01 1
9.6
0.23
25.4
0.60
0.08
0.002
3188
73.3
CONSTRUCTION AND INDUSTRIAL EQUIPMENT
g/kg fuel
g/MJ
50.2
1.2
0.18
0.004
3.9
0.09
16.3
0.38
0.08
0.002
3188
73.3
JET AND TURBOPROP AIRCRAFT
g/kg fuel
g/MJ
12.5
0.29
0.087
0.002
0.78
0.018
5.2
0.12
n/a
n/a
3149
71.5
GASOLINE (PISTON) AIRCRAFT
g/kg fuel
g/MJ
3.52
0.08
2.64
0.06
24
0.54
1034
24
0.04
0.0009
3172
69.3
                     Data on emissions from aircraft are limited or presented in forms which are difficult to
                     compare. The factors shown for aircraft were developed by Radian (1990) - for jet
                     (turbine) emissions based on a Pratt and Whitney JT-17 engine (one of the most
                     commonly used types), and for small gasoline-fueled piston aircraft based on a Cessna
                     engine. These are considered very approximate. For the gasoline piston engines, fuel-
                     specific N2O emissions were assumed to be similar to those for uncontrolled passenger
                     cars.
1.82

-------
                                                                             EMISSIONS FROM ENERGY
               1.7.4  Recent Information  Updates

               Methane
               As background for an expert group meeting to advise the IPCC/OECD programme,
               Berdowski, Olivier and Veldt (1993) provided some updated emission factors for methane,
               in general derived from total VOC factors and studies on VOC profiles. In Table I -32 the
               emission factor estimate for each fuel and vehicle type is summarized. Some of these
               factors are presented in a somewhat different format, but aire generally very similar to
               those presented in the previous section, where they overlap. Some factors, notably for
               uncontrolled gasoline road vehicles are somewhat higher in the more recent material. The
               expert group in its report (Berdowski, et al., 1993) emphasized that uncertainties in all
               CH4 estimates to date are large, and that no fully satisfactory set of emission factors is
               currently available for use in national inventory development.
               Highest emission factors for CH4 appear for (uncontrolled) gasoline vehicles (cars, light
               and heavy duty vehicles), and for consumption of aviation gasoline (avgas) which is
               generally used by general aviation aircraft (e.g. business aircraft). All factors are averages
               including all transport modes of a specific vehicle (e.g. city (traffic, highways; cruise flights,
               take-off, landing, etc.). Uncertainty ranges are difficult to specify, since factors are derived
               by taking a fraction of total VOC emission factors, both introducing uncertainties. In
               addition, estimating global averages of total VOC, and thus methane, factors is an other
               cause of uncertainty. Mobile sources, in particular gasoline consumption, are a source
               category which is of some importance, and the uncertainty' of which may be quite large.
PART 2
                                                                                                                  1.83

-------
EMISSIONS FROM ENERGY
TABLE 1-32
GLOBAL METHANE EMISSION FACTORS FOR MOBILE SOURCES
Modofveh tele type * Y ,"*",
-~"~ „ t) T * ,
Cars/ 4-stroke, uncontr.
LDV-Freighc
2-stroke, uncontr.
4-stroke, 3-way cat.


3-way cat

HDV (Freight)
Rail, water
Aircraft
Fuel type
gasoline
gasoline
gasoline
diesel
LPG
natural gas
alcohol
gasoline
diesel
diesel, res. oil
coal
biomass
jetfuel
avgas
Emission factor****} »

*)
Olivier, 1991
Radian 1990***)
*)
*)
*)**)
*)**)
*)**)
Olivier, 1991
Radian, 1990
Radian, 1990
Notes:
LDV = Light Duty Vehicle (car. van); HDV = Heavy Duty Vehicle (trucks)
*) Emission factors derived from VOC factors and studies on VOC profiles.
**) Emission factor derived from boiler emissions.
***) Emission factor for methanol.
****) Emission factor all mode average (including all transport phases e.g. highways,
city traffic; cruise flight, take-off etc.). Original factors are in g/kg [marked *)].
                       Nitrous Oxide

                       An  expert  group convened to advise the  IPCC/OECD programme  on N2O  from
                       combustion concluded that the basic estimation methodology previously recommended by
                       the OECD (1991) was generally still appropriate, though future imporvements should be
                       considered  in characterizing catalyst equipped road  vehicles. (Olivier,  1993)   This  is
                       especially important as vehicles equipped with new catalysts have emission factors which
                       are 4 to 5 times higher than those of uncontrolled vehicles (De Soete, 1993); and emission
                       factors of vehicles with medium aged catalysts (about 25 000 km) are 10 to 16 times higher
                       than  uncontrolled vehicles  (De  Soete,  1993; Baas,  1991). In principle,  an  improved
                       methodology for estimating N2O emissions from catalyst controlled gasoline cars would
                       be a further distinction between:

                       (a)  cars equipped with a new catalyst (e.g. <  15 000 km)

                       (b)  cars equipped with aged catalysts (e.g. > 15 000 km).

                       (c)  cars with malfunctioning catalysts.

                       However, since in practice the fraction of catalyst equipped cars which has a "new" catalyst
                       will be quite small, these refinement will likely result in a minor correction of the factors
                       used for category (b) to be used as average figures for the whole fleet including all vintages
1.84

-------
                                                                               EMISSIONS  FROM  ENERGY
                of catalyst equipped cars of a specific type as defined under category 2. Also the fraction of
                the catalyst car fleet with  malfunctioning catalysts will generally not be known as are the
                appropriate N2O emission factors for this category. Some  countries may improve the
                calculations by distinguishing between various types of catalysts or between different parts
                of the driving cycle - when activity data are available of course.
                For non-catalyst equipped vehicles the estimated emission factors for gasoline and diesel
                cars reported in  the Revised IPCC/OECD Report of August  1991  are in line  with the
                ranges reported in  the evaluation by De Soete (1993) and Baas (1991). For other fuels
                such as LPG, natural gas, and biofuels (e.g. ethanol and methanol) default emission factors -
                expressed  as g/GJ -for different types of road vehicles still have to be determined. In Table
                1-33  the estimated emission factors and uncertainty ranges  are shown for a number  of
                types of road vehicles, where the figures in the column "emission factor" are preliminary
                estimates for the vehicle fleet in the USA. For default emission factors of catalyst  equipped
                cars it is recommended to use a value within the uncertainly range shown in the table.
                For non-road  vehicles  (ships,  locomotives and off-road  vehicles e.g.  for farming and
                construction) emission factors have been assumed to be the same as for heavy duty diesel
                trucks. For gasoline  piston aircraft fuel-specific emission factors were assumed to be
                similar to those for uncontrolled gasoline passenger cars; for jet aircraft no N2O estimated
                emission factors are available. Table 1-34 shows the estimated  emission factors  for these
                categories.

                Indirect Greenhouse Gases
                The IPCC/OECD programme has not yet addressed the  indirect GHGs in detail. This is
                consistent with the initial priorities within the programme.  As noted above, mobile source
                combustion is  a major contributor to all of  these gases.  Because they  are  important
                contributors to a  range  of local and regional, as well as global atmospheric  pollution
                problems,  NOX, CO and NMVOC have been widely studies and reported. The illustrative
                data  cited  above  reflect  estimates of average emission   rates for  main transport sub-
                categories  worldwide, as  of   1991.  They  are  still  considered  to  be  reasonably
                representative. However, the  data are based  on  analyses  done for the United States
                vehicle fleets, and they may be  less representative elswhere.  In all cases they are averages
                over a range of vehicle and control technologies, and operating conditions.
PART 2
                                                                                                                     1.85

-------
EMISSIONS  FROM  ENERGY
TABLE 1-33
ESTIMATED EMISSION FACTORS AND UNCERTAINTY RANGES FOR ROAD VEHICLES.
Vehicle type
Gasoline car
Gasoline car. 2 stroke engine
Diesel car
LPGcar
Natural gas (CNG) car
Motor cycle
Blofuel car (echanol, methanol)
Passenger, controlled:
Non-catalytic controlled gasoline car
Oxidation catalyst gasoline car
Early 3-way catalyst gasoline car
Advanced 3-way catalyst gasoline car
Aged catalyst gasoline car
Moderate controlled diesel car
Advanced controlled diesel car
Catalyst equipped LPG car
Catalyst equipped methanol car
Non-catalytic controlled motor cycle
Freight, uncontrolled:
Low-duty gasoline vehicles
Low-duty diesel vehicles
Low-duty LPG vehicles
Low-duty CNG vehicles
Heavy-duty gasoline vehicles
Heavy-duty diesel vehicles
Heavy-duty LPG vehicles
Heavy-duty CNG vehicles
Freight, controlled:
Non-catalyst LD gasoline truck
Oxidation catalyst LD gasoline truck
Early 3-way catalyst LD gasoline truck
Advanced 3-way catalyst LD gasoline truck
Moderate controlled LD diesel truck
Advanced controlled LD diesel truck
Catalyst equipped LD LPG truck
Non-catalyst controlled HD gasoline truck
Oxidation catalyst HD gasoline truck
3-way catalyst HD gasoline truck
Moderate controlled HD diesel truck
Advanced controlled HD diesel truck
Emission factors* (g N2O/km)
(g N2O/GJ energy input)
NA/0.005
NA
NA/0.014
N/A
NA
NA/0.002
NA

NA/0.005
NA/0.027
NA/0.(M6
N A/0.0 19
NA
N A/0.01
NA/0.007
NA
NA
NA/0.002

NA/0.006
N A/0.0 17
NA
NA
NA/0.009
NA/0.031
NA
NA

NA/0.006
NA/0.031
NA/0.063
NA/0.024
NA/0.014
NA/0.009
NA
NA/0.006
NA
NA/0.006
NA/0.025
NA/0.025
NA/0.9
NA
NA/1.9
NA
NA
NA/0.9
NA

NA/0.9
NA/4.9
NA/13.0
NA/6.9
NA
NA/1.9
NA/1.9
NA
NA
NA/0.9

NA/0.9
NA/1.9
NA
NA
NA/0.5
NA/1.9
NA
NA

NA/0.9
NA/4.8
NA/13.0
NA/6.8
NA/1.9
NA/1.9
NA
NA/0.5
NA
NA/0.5
NA/1.9
NA/1.9
Uncertainty range4*"
(g N20/kmXg N.20/GJ energy)
0.004-0.06
NA
0.02-0.06
NA
NA
NA
NA

NA
NA
NA
NA
0.05-0.32
• NA
NA
NA
NA/0.002-0.004
NA

0.004-0.06
0.02-0.06
NA
NA
NA
NA
NA
NA

NA
0.03-0.084
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
1.5-22
NA
8-25
NA
NA
NA
NA

NA
NA
NA
NA
18-120
NA
NA
NA
NA/0.2-0.4*"™
NA

1.5-22
8-25
NA
NA
NA
NA
NA
NA

NA
12-35
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
                     N.B.   NA = Not Available
                              Preliminary estimate for US vehicles.
                            ^^
                              Assumed fuel economy. 12 km/I gasoline; 15 km/I diesel.
                               Preliminary estimate for Japanese vehicles.
                     source: emission factor estimates for US vehicles: EPA (1989); Prigent and De Soete (1989); Dasch (1990); Ford
                            (1989-1991); Warner-Selph and Smith (1991);
                            uncertainty range: De Soete (1993), Baas (1991)
                            controlled methanol cars: Iwasaki et of. (1990), Susuki et al. (1992).
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                                                  TABLE 1-34
                   ESTIMATED DEFAULT EMISSION FACTORS AND UNCERTAINTY RANGES FOR NON-ROAD
                                                  TRANSPORT.
Activity
Sea ships (diesel)
Ships (int. nav.)(diesel)
Locomotives (diesel)
Off-road vehicles" (diesel)
Aircraft (jet fuel)
Aircraft (aviation gasoline)
Emission factor
(gN20/kg)
2*
2*
2*
2*
NA
0.9'
Uncertainty range
(gN20/kg)
NA
NA
NA
NA
NA
NA
                N.B.     NA = Not Available
                        * Preliminary estimate (assumed to be similar to HD dieseil vehicles and uncontrolled gasoline
                        passenger cars).
                          e.g. farm and construction equipment.
                source:   See note	^____

                More detailed alternative emission factor source data representative of the precise vehicle
                types, control technologies and other conditions in a particular country would always be
                desirable. National experts working on detailed emissions of non-CO2 GHGs (particularly
                the indirect gases)  should  consult the extensive  literature on emission factors  and
                estimation procedures which has been developed by other inventory programmes outside
                of the framework of the IPCC/OECD programme.  As distinguished from the illustrative
                emission factors, these data generally contain more vehicle and control technology detail,
                and are further detailed by operating conditions (e.g., catalyst vintages, driving cycles). The
                specific nature of these assumptions should be known and carefully matched with actual
                conditions in the specific country in selecting the specific factors to be used.

                Some key examples of data sources are:
                •    The CORINAIR Inventory: Default Emission Factors Handbook (Bouscaren,  1992);

                •    CORINAIR Working Group on Emission Factors for Calculating 1990 Emissions
                     from Road Traffic, Volume I: Methodology and Emission Factors (Eggleston, et al.,
                     1992)
                •    CORINAIR Working Group on Emission Factors for Calculating 1990 Emissions
                     from Road Traffic, Volume 2: COPERT Model, Users Mannuel (Andrias, etal., 19.92)

                •    Emissions Inventory Guidebook (European Environment Agency, forthcoming)

                •    U.S. EPA's Compilation of Air Pollutant Emissions Factors: Highway Mobile Vehicles
                     (AP-42), 4th Edition  1985,    (U.S. EPA, 1985);

                •    U.S. EPA's Mobile4 Model and User's Guide. U.S. NTIS (1991)

                •    Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory
                     (Stockton and Stelling, 1987)
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                       1.7.5  Priorities  For Future  Work

                      Access to Exisiting Data: There is a significant amount of past and on-going work in the
                      area of mobile source emissions estimation that could be very useful for all countries. ,
                      Major references are cited in the previous section. However, at this time there is no
                      simple mechanism for published information, and especially underlying data bases be
                      disseminated it to other interested countries. The IPCC/OECD Programme should
                      address information exchange more explicitly, in conjunction with other interested
                      organizations and programmes, possibly resulting in a clearinghouse or some other
                      mechanism to improve access to such information.

                      Data for Non-OECD Regions of the World: Most of the information which does
                      exist on emissions performance of vehicles, is based on data collected in the OECD
                      countires. A critical need is for measurement data to determine the characteristics of
                      vehicle fleets in non-OECD countries and to develop adjusted emission factors  if
                      necessary.

                      Key Emission Factor Uncertainties: At  this moment there are some key areas for
                      which available emission factors are not adequate for to support national inventory
                      development. Expert groups have identified several specific categories for priority work:

                      CH«   uncontrolled gasoline road vehicles particularly as affected by age and
                             maintenance
                      N2O - biofuels for all applications

                             ships, aircraft and  rail

                             gasoline and diesel vehicles (with and .without catalyst control)

                             LPG, natural gas and biofuels used for road transport (with and without catalyst
                             control)
              1.8    Fugitive  Emissions  from  Coal  Mining,
                      Handling and  Utilization
                       1.8.1  Overview

                      This section covers "fugitive" emissions of greenhouse gases (GHGs) from production,
                      processing, handling and utilization of coal. Conceptually, this includes all emissions from
                      coal-related activities which are not the result of combustion of coal as a fuel. Thus,
                      intentional or unintentional releases of gases such as methane in mining are included here,
                      as are emissions from inadvertent combustion of coal in coal mine fires. By far the most
                      important component of this sub-category is methane (CH4) emissions from coal mining
                      and handling. The bulk of this section, deals with these emissions. Two other fugitive
                      emission sources are discussed briefly at the end of the section. These are CO2 from
                      burning coal mines and waste piles, and CO2 from SO2 scrubbing. There are very likely
                      other fugitive emissions associated with the coal fuel cycle. If important sources are
                      identified, these will be considered for inclusion in future editions of the Guidelines.
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                                                                              EMISSIONS FROM ENERGY
                1.8.2  CH<  From  Coal  Mining  And  Handling

                The process of coal formation, commonly called coalification, inherently generates
                methane and other byproducts. The formation of coal is a complex physio-chemical
                process occurring over millions of years. The degree of coalification (defined by the rank
                of the coal) determines the quantity of methane generated and, once generated, the
                amount of methane stored in the coal is controlled by the pressure and temperature of
                the coal seam and other, less well-defined characteristics of the coal. The methane will
                remain stored in the coal until the pressure on the coal is reduced, which can occur
                through the erosion of overlying strata or the process of coal mining. Once the methane
                has been released, it flows through the coal toward a pressure sink (such as a coal mine)
                and into the atmosphere (Boyer,  1990). Methane emissions: from coal mining in 1990
                contributed an estimated 23 to 39 Tg of methane (USEPA, I993a; CIAB, 1992; Airuni,
                1992).
                The amount of CH4 generated during coal mining is primarily a function of coal rank and
                depth, gas content, and mining methods, as well as other factors such as moisture. Coal
                rank represents the differences in the stages of coal formation and is dependent on
                pressure and temperature of the  coal seam; high coal ranks;, such as bituminous, contain
                more CH4 than low coal ranks, such as lignite. Depth is important because it affects the
                pressure and temperature of the  coal seam, which in turn determines how much  CH4 is
                generated during coal formation.  If two coal seams have the same rank, the deeper seam
                will hold larger amounts of CH4 because the pressure is greater at lower depths,  all other
                things being equal. As a result, the methane emission factor's for surface mined coal are
                assumed to be lower than for underground mining.
                In most underground mines, methane is removed by ventilating large quantities of air
                through the mine and exhausting this air (typically containing a concentration of I percent
                methane or less) into the atmosphere. In some mines, however, more advanced methane
                recovery systems may be used to supplement the ventilation systems and ensure mine
                safety. These recovery systems typically produce a higher concentration product, ranging
                from 35% to 95% methane. In some  countries, some of thiis recovered methane is used as
                an energy source, while other countries vent it to the atmosphere. Recent technological
                innovations are increasing the amount of medium- or high-quality methane that can be
                recovered during coal mining and the options available to use it. Thus, methane emissions
                could be reduced from this source in the future.
                In surface mines, exposed coal faces  and surfaces, as well as areas of coal rubble created by
                blasting operations, are believed to be the major sources of methane. As in underground
                mines, however,  emissions may come from the overburden (in limited cases where these
                strata contain gas), which is rubblized during the mining process, and underlying strata,
                which may be fractured and destressed due to removal of the overburden. Because
                surface mined coals are generally lower rank and less deeply buried, they do not tend to
                contain as much methane as underground mined coals. Thus, emissions per ton of coal
                mined are generally much lower for .surface mines. Research is underway in the United
                States and elsewhere to increase the understanding of CH,, emissions from surface mines
                (Kirchgessner, I992;USGS, 1993).
                A portion of the CH4 emitted from coal mining comes from post-mining activities such as
                coal processing, transportation, and  utilization. Coal processing involves the breaking,
                crushing, and thermal drying of coal, making it acceptable for sale. Methane is released
                mainly because the increased surface area allows more CH4 to desorb from the coal.
                Transportation of the coal contributes to CH4 emissions, because CH4 desorbs directly
                from the coal to the atmosphere while in transit (e.g., in railroad cars). Utilization of
                metallurgical coal also emits, methane. For instance, in metallurgical coke production, coal
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                       is crushed to a particle size of less than 5 mm, vastly increasing the surface area of the coal
                       and allowing more CH4 to desorb. During coking process, methane, carbon dioxide, and
                       other volatile gases are released. In modern coke ovens, this gas is typically collected and
                       utilized as a fuel source, but in older coke ovens, particularly those used in less developed
                       regions, coke gas is vented to the atmosphere (Boyer, 1990; coke production is covered in
                       Chapter 3).
                       Some methane is also released from coal waste piles and abandoned mines. Coal waste
                       piles are comprised of rock and small amounts of coal that are produced during mining
                       along with marketable coal. There are currently no emission measurements for this
                       source.  Emissions are believed to be low, however, because much of the methane would
                       likely be emitted in the mine and the waste rock would have a low gas content compared
                       to the coal being mined. Emissions from abandoned mines may come from unsealed shafts
                       and from vents installed to prevent the buildup  of methane in mines. There is very little
                       information on the number of abandoned mines, and data are currently unavailable on
                       emissions from these mines. Most available evidence indicates that methane flow rates
                       decay rapidly once deep mine coal production ceases (Williams and Mitchell, 1992;
                       Creedy, 1991). In some abandoned mines, however, methane can continue to be released
                       from surrounding strata for many years. In Belgium, France, and  Germany, for example,
                       several abandoned mines are currently being used as a source of methane which can be
                       added to the gas system (Smith  and Sloss, 1992; KfA, 1993). Due to the absence of
                       measurement data for both coal waste piles and abandoned mines, no emissions estimates
                       have been developed for these sources.

                       Review of Previous Methane Emission Estimation Studies

                       Over the years, a variety of methane emissions estimates have been developed for coal
                       mining,  as shown in Table I. As the table shows, the variation  in estimates has been quite
                       large, although more recent studies are showing more similar results. Many of the
                       emission studies conducted to date have confronted difficulties in developing estimation
                       methodologies that have resulted in the widely varying estimates and large uncertainties.
                       These difficulties include:
                       •   Absence of data on which  to base estimates:  Many methane emission estimation
                            studies were developed without access to detailed data on methane emissions
                            associated with various components of the coal cycle. For certain sources such as
                             surface mines and post-mining activities, moreover, reliable emissions measurements
                             are still lacking.
                       •    Use of national data to develop global estimates: Some studies have relied on data
                            from a single country to estimate global methane emissions from coal mining. This
                             approach can introduce large errors into the estimates due to the difficulty of
                             generalizing from one country's coal and mining conditions to other countries.  Mining
                             experience has shown that there are frequently significant differences in methane
                             emission factors within countries, coal basins, and even coal mines for a variety of
                             geologic and other reasons.
                       •    Failure to include all possible  emission sources: Some studies prepared to date have
                             only estimated underground coal mining emissions from ventilation systems and have
                             not included degasification system emissions or post-mining emissions. In addition,
                             many estimates have assumed emissions from surface mines to be negligible and have
                             not included this source. At this point, moreover, there are still potential emission
                             sources such as abandoned mines for which emissions cannot be estimated due to
                             the absence of necessary data.
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                                                                                EMISSIONS  FROM  ENERGY
                 •   Overreliance on statistical estimation methodologies: Several studies have attempted
                     to estimate global emission factors using statistical models that relate methane
                     emissions to various coal properties. For the most part, these models have proven
                     unreliable when estimates are compared to those developed using more detailed
                     country-specific information. The principal problem with using statistical
                     methodologies is the number of variables that can affect methane emissions. Mining
                     experience has shown that a complete understanding of methane emissions requires
                     detailed examination of coal and geological characteristics and that methane
                     emissions can be highly variable within mines, basins and countries. Collecting
                     comprehensive data and developing statistical models of methane emissions that can
                     reliably predict methane emissions on a global basis is thus extremely difficult.
                 In general, the results of the more recent country-specific and global methane emission
                 studies are likely to be more reliable than previous efforts. For several of the mafor coal
                 producing countries, for example, detailed data on methane; emissions from underground
                 mine ventilation and degasification systems are reported to central institutes and are
                 publicly available. More recent studies have been able to use this available data from
                 several countries in preparing and validating their estimates of methane emissions from
                 underground mines. Data is still lacking on emissions from surface mines and post-mining
                 activities, however, and thus even the emission estimates from more recent studies should
                 be considered uncertain.

                 Suggested Emission Estimation Methods
                 Methane emission  estimates should be developed for the three principal sources of
                 methane emissions: underground mines, surface mines, and post-mining activities. To
                 assist in  developing these estimates, the IPCC recommends use of a "tiered" approach for
                 estimating emissions. For each source, two or more approaches (or "tiers") are presented
                 for estimating emissions, with the first tier requiring basic and readily available data and
                 higher tiers requiring additional data. The selection among iJie tiers will depend upon the
                 quality of the data available in the country.

                 Underground Mining
                 Methane emissions from underground mines should include! estimated emissions from
                 ventilation systems and from degasification systems, if any of a country's mines use
                 degasification systems to supplement ventilation. In the approaches outlined below,
                 methods of estimating emissions from both of these sourceis are presented.
                 Three possible methodological approaches are suggested by the IPCC, with the choice
                 among them depending upon the availability of data and the degree to which coal mining  is
                 considered a significant source of emissions by particular countries. For those countries
                 with comparatively large methane emissions from coal mining, the use of more detailed
                 estimation methodologies may be warranted. In smaller coal producing countries,
                 however, the most simple approach may provide a reasonably accurate first approximation
                 of CH4 emissions from underground mines.
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TABLE 1-35
SUMMARY OF EMISSIONS ESTIMATES FROM SELECTED STUDIES
Study Author
Koyama (1963)
Hitchcock & Wechsler (1972)
Seller (1984)
Crutzen(l987)
Okkcn & Kram (1989)
Zimmcrmcyor (1989)
Seltzer &Zittel( 1990)
Barns & Edmonds. USDOE (1990)
Boyer.USEPA(l990)
Margraves (1990)
Airuni(l992)
C1AB(I992)
USEPA(l993a)
Emissions
Estimate
(Tg)
20
8-28
30
34
15-45
24
23
25
33-64
29
28
24
23-39
Year of Estimate
I960
1967
1975
n/a
n/a
n/a
n/a
1986
1988
n/a
1990
1990
1990
Methodological Issues
Hard coal only; no emissions estimates for
surface mining or pose-mining activities. 1 960
coal production data.
Post-mining not included; Source of emission
factors, particularly low end, unspecified. 1 967
coal production data.
Based on Koyama, with 1 975 coal production
data.
Source of emission factors unclear. Hard coal
only; no emissions estimates for surface mining
or post-mining activities.
Source of emission factors unclear. Hard coal
only; no emissions estimates for surface mines or
post-mining activities.
Only underground mining considered; no
emissions estimates for surface mines or post-
mining activities.
Adjusted Zimmermeyer by: ( 1 ) including surface
mines; (2) assuming that 1 5 percent of
underground mining emissions (3.6 Tg) not
emitted to the atmosphere due to methane
utilization.
Assumed mathematical relationship between coal
rank and depth and that in-situ methane content
was equal to the mining emission factor.
Statistical approach related methane emissions to
in situ methane content. Correlation based on
U.S. data only. Large uncertainty in application of
results for global estimates.
Method based on current methane production
rates due to continued coalification.
Methodology unspecified.
Country specific data used where available for
underground mines. Surface and post-mining
emissions developed using low emission
assumptions. No uncertainty analysis.
Country specific data used where available for
underground mines. Global average emission
factors for rest of countries for underground
mines and for all surface mining and post-mining
emissions.
                     The first tier approach—called the Global Average Method—uses a pre-determined range
                     of emission factors (based on experience in a number of countries) to estimate emissions.
                     The most complex, third tier, approach—called the Mine Specific Method—develops
                     emissions estimates using detailed emission data for most, if not all, of a country's
                     underground coal mines. In between these two methods is an intermediate, second tier,
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                                                                             EMISSIONS FROM ENERGY
                approach-called the Basin or Country Average Method-in which more limited
                information, including either measurements from a subset of mines or geological and other
                data, can be used to refine the range of possible emission factors presented in the Global
                Average Method. Each of these approaches is described in more detail below.
                Tier I: Global Average Method

                The simplest method for estimating methane emissions is to multiply underground coal
                production by a factor or range of factors representing global average emissions from
                underground mining, including both ventilation and degasification system emissions. This
                method may be selected in cases where total coal production from underground mines is
                available but more detailed data on mining emissions, geological conditions, coal
                characteristics, and the like are not. The emission estimates generated using this method
                should be presented as a range to reflect the high degree of uncertainty associated with it.
                The Tier I Equation is shown below.
                      EQUATION I
                        TIER I: GLOBAL AVERAGE METHOD - UNDERGROUND MINES
                      Low CH.4 Emissions  =     Low CH4 Emission Factor
                       (tonnes)
                         (m3 CH4/tonne of coal mined)
                      High CH4 Emissions  =
                        (tonnes)
                        x Underground Coal Production
                        (tonnes)
                        x Conversion Factor
                        High CH4 Emission Factor
                        (m3 CH4/tonne of coal mined)
                        x Underground Coal Production
                        (tonnes)
                        x Conversion Factor
Where:
• Low CH4 Emission Factor = 10 m3/tonne
• High CH4 Emission Factor = 25 m3/tonne
• Conversion Factor converts the volume of CH4 to a weight measure based
on the density of methane at 20C and I  atm, which  is:
          1.49 x I09 m3 per I million metric tons
                In the original IPCC methodology, a single emission factor of 27.1  m3 of methane per
                tonne of coal mined was recommended for all underground mining. This factor included
                both emissions from mining and from post-mining emissions associated with underground
                coal production.33
                   33  Due to a  mistake in  OECD (1991), it appeared  that this  factor did not
                include emissions from mine degasification systems and post-mining activities.  In
                fact, however, this emission factor did include these two additional emission
                sources.
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                       Based on more recent studies and additional country-specific emission data, the IPCC
                       recommends revising this emission factor to reflect some additional issues. First, use of a
                       range of emission factors is suggested to reflect the large variation possible in methane
                       emissions from underground mines in different coal basins and countries. Second, this
                       emission factor should represent only those emissions associated with underground
                       mining (ventilation and degasification systems); post-mining emissions should be handled
                       separately.
                       The IPCC recommends revised global average emission factors of 10 to 25 m /tonne of
                       coal mined (not including post-mining activities). This range reflects the findings of various
                       country studies, as shown in Table 1-36. As more detailed emissions data are published by
                       various countries, the factors can be further revised, if necessary.

                       Tier 2: Country or Basin Average Method
                       The suggested Tier 2 approach-called the "Country or Basin Average Method"~can be
                       used to refine the range of emission factors used for underground mining by incorporating
                       some additional country or basin-specific information. Basically, this method enables a
                       country with  limited available data to determine a more appropriate and most likely
                       narrower range of emission factors for their underground mines. For many countries, it is
                       expected that this range will fall within the global average emission factor range of 10 to
                       25 mVtonne.  The range of possible emission factors is not constrained under the Tier 2
                       approach, however, and some countries may find that their underground mining emission
                       factors lie outside the global average emission factor range.
                       To implement the Tier 2 approach, national experts must examine measurement data
                       from at least  a limited number of underground coal mines in their country or region. Using
                       this data, either statistical analysis or expert judgement should be applied to develop a
                       reasonable range of emission factors for the country or region.34  Making this estimate will
                       require judgment on the part of the estimator regarding the adequacy of the available data
                       and its uncertainty. If sufficient expertise is not available to make such judgments, it is
                       recommended that the Tier  I approach (the Global Average Method) be used to prepare
                       emissions estimates.
TABLE i-36
ESTIMATED UNDERGROUND EMISSION FACTORS FOR SELECTED COUNTRIES
Country
Former Soviet Union
United States
Germany (East & West)
United Kingdom
Poland
Czechoslovakia

Emissions Factors (mJ/ton)
17.8-22.2
11.0- 15.3
22.4
15.3
6.8- 12.0
23.9
15.6
Source
USEPA, I993a
USEPA, 19936
Zimmermeyer, 1989
BCTSRE, 1992
Richer, 1991
Elibler, 1992
Lama, 1992
                           34  If measurement data is available for most or all or a country's underground
                         coal  mines, the Tier 3 approach-called the  "Mine Specific Method"--should  be
                         used to estimate emissions.
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                                                                                 EMISSIONS  FROM  ENERGY
                  In some cases, measurement data on emissions from mines may be unavailable but a
                  country will still seek to develop a narrower estimate based on other types of available
                  data. In such cases, a country may seek to develop a simple emissions model based on
                  physical principals or make judgments based on an evaluation of available data. Among the
                  key types of data that should be considered in such a model or evaluation are:

                  •   the gas content of the coal, which contributes to the total amount of methane
                      available for emission during mining;

                  •   the frequency of coal within the strata above and below the mined coal seam, which
                      also contributes to the total amount of methane available for emission during mining;
                      and,

                  •   the method of mining, which determines  the amount of ground that is disturbed by
                      mining the coal and the extent to which the methane contained in the mined coal
                      seam and the coal seams in the surrounding strata is liberated during mining.

                  It should be noted that while the Tier 2 approach can provide some additional information
                  about methane emissions in a particular country or coal basin, the  estimates will still be
                  quite uncertain because of the absence of comprehensive and  reliable emissions data. This
                  approach should thus be used only in cases where  there is a strong need to make an
                  estimate that is narrower than the Tier I (Global Average Method) and not enough data
                  are available to prepare an estimate  using the Tier  3 (Mine Specific Method) described in
                  the next section. It should further be noted that these narrower estimates will not
                  necessarily be more accurate than those developed under Tier I because they have not
                  been developed or verified with comprehensive measurement data.

                  In all cases where the Tier 2 approach is used,  a detailed discussion of the types of data
                  available and the manner in which it  was used to determine the refined range of emission
                  factors should be presented, so  as to allow for the independent verification of estimates
                  and ensure comparability with estimates being  prepared by other countries.
                  Tier 3: Mine Specific Method

                  Because methane is a serious safety hazard  in underground mines, many countries have
                  collected data on methane emissions from mine ventilation systems, and some also collect
                  data on methane emissions from mine degasification systems. Where such data are
                • available, the more detailed Tier 3 approach-called the "Mine Specific Method"-should
                 provide the most accurate estimate of methane emissions from underground mines. Since
                 these data have been collected for safety, not environmental reasons, however, it is
                 necessary to ensure that they account for total emissions from coal mines. The key issues
                 that should be considered when using mine safety data, as well as the recommendations of
                 the IPCC for resolving them, are shown in Table 1-37.

                 Treatment of Methane Utilization

                 All of the methods described above,  with the possible exception of the Mine Specific
                 Method, assume that all of the methane liberated by mining will be emitted to the
                 atmosphere. In many countries, however, some of the methane recovered by mine
                 degasification systems is used as  fuel  instead of  being emitted. Wherever possible, the
                 emission estimates should be corrected for the amount of methane that is used as fuel, by
                 subtracting this amount from total estimated emissions.

                 In several countries, data on the disposition of  methane recovered by degasification
                 systems (i.e., whether it is used or emitted to the atmosphere) can  be obtained from the
                 coal industry or energy ministries. Poland, for example, reports that its mine degasification
                 systems recovered 286 million m3 of methane in  1989, of which 201 million m3 was used
                 and the remaining 85 million m3 was  emitted to the atmosphere (Polish Central Mining
PART 2
                                                                                                                   1.95

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                         Institute, 1990). Regardless of the method used to develop the emissions estimates, the
                         Polish emission estimate should be adjusted to reflect the use of methane by subtracting
                         201 m3 from total emissions.
                         In some countries, data on the disposition of methane recovered by degasification systems
                         may not be reported, but it may still be possible to estimate utilisation amounts. In some
                         cases, for example, it may be possible to collect utilization data from end-users of the
                         methane if such data are unavailable from the mining industry. It may also be possible to
                         estimate utilization amounts based on information about the specific utilization options
                         being employed (i.e.. if the methane is being used to fuel a gas turbine of a specific size).
                                                               TABLE 1-37
                                   KEY ISSUES FOR CONSIDERATION WHEN USINGTIER 3 ~ MINE SPECIFIC METHOD
                        ISSUE
                                                            DESCRIPTION
                                                                                                RECOMMENDATION
               Where and how are ventilation system
               emissions monitored?
When used to develop overall methane
emission estimates, the optimal location for
ventilation air monitors is at the point
where ventilation air exhausts to the
atmosphere.
If ventilation emissions are not monitored
at the point of exhaust, emission data
should be corrected based on estimated
additional methane emissions between the
point of measurement and the point of
exhaust to the atmosphere.
               Arc ventilation system emissions
               monitored and/or reported for all mines?
In some countries, emissions are only
reported for "gassy mines".
Estimates should be developed for non-
gassy mines as well. Estimates can be
prepared using information about the
definitions of gassy and non-gassy mines
and data on the total number of mines and
the coal production at these mines.
               Are methane emissions from degasification
               systems reported?
Some countries collect and report methane
emissions from ventilation and
degasification systems, while others only
report ventilation system emissions. Both
emission sources must be included in
emissions estimates.
If degasification system emissions are not
included, those mines with degasification
systems should be identified and estimates
prepared on emissions from their
degasification systems. Emissions estimates
can be based on knowledge about the
efficiency of the degasification system in use
at the mine or the average efficiency of
degasification in the country.
                          The data sources for any adjustments to emissions that are made to reflect the utilization
                          of methane should be clearly specified to ensure the independent verification of the
                          emissions estimates developed. If data are unavailable, no adjustment for utilization should
                          be made.

                          Surface Mining
                          Two possible approaches for estimating methane emissions from surface mining are
                          suggested by the IPCC. For the most part, these approaches resemble those developed
                          for underground mining, but the results will be much more uncertain due to the absence
                          of emissions data. If emissions measurements are developed in the future, it should be
                          possible to refine these estimation methodologies.

                          Tier I:  Global Average Method
                          As for underground mining, the simplest Tier I approach for surface mines-called the
                          "Global Average Method"-is to multiply surface coal production by a range of emission
                          factors representing global average emissions, as shown in the equation below.
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                                                                             EMISSIONS FROM ENERGY
                                               EQUATION 2
                              TIER I: GLOBAL AVERAGE METHOD — SURFACE MINES
                Low CH4 Emissions =
                 (tonnes)
                High CH4 Emissions =
                 (tonnes)
                       Low CH4 Emission Factor
                       (m3 CH^/tonne of coal mined)
                       x Surface Coal Production
                       (tonnes)
                       x Conversion Factor
                       High CH4 Emission Factor
                       (m3 CH^tonne of coal mined)
                       x Surface Coal Production
                           (tonnes)
                       x Conversion Factor
Where:
•   Low CK4 Emission Factor = 0.3 m3/tonne
•   High CH4 Emission Factor = 2.0 m3/tonne
•   Conversion Factor converts the volume of CH4 to a weight measure based on
    the density of methane at 20C and I atm, which is:
                1.49 x I09 m3 per I million metric tons
                In the original 1PCC methodology, an average emission factor of 2.5 m /tonne was
                recommended (OECD, 1991), based on the results of Boyer (I990).35 Based on more
                recent analyses and additional studies, a revised emission factor range of 0.3 to 2.0
                m3/tonne is recommended by the IPCC, not including post-mining emissions (USEPA,
                !993a;CIAB, I992;BCTSRE, I992;CMRC, 1992; Kirchgessner, 1992).
                Given the lack of information and measurements on methane emissions from surface
                mines, this range must be considered extremely uncertain, and it should be refined in the
                future as more data become available.
                Tier 2: Country or Basin Specific Method
                A second tier estimation of methane emissions—called the "Country or Basin Specific
                Method"--can be used  if additional information is available on in-situ methane content and
                other characteristics of a country's surface mined coals. This approach enables a country
                to develop emission factors that better reflect specific conditions in their countries.
                Depending on the degree of detail desired, emissions can be estimated for specific coal
                basins or countries, using the equation below.
                   35  In OECD (1991), it mistakenly appears that the surface mining emission factor does
                 not include emissions from post-mining activities; In fact, i:he factor of 2.5 m3/ton includes
                 both direct emissions from surface mining and those from post-mining activities.
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EMISSIONS FROM ENERGY
                                                         EQUATION 3
                                        TIER 2:  COUNTRY OR BASIN SPECIFIC METHOD - SURFACE MINES
                             CH^ Emissions =   [ In-Situ Gas Content
                              (tonnes)         (m3 CH4/tonne)
                                              x Surface Coal Production
                                               (tonnes)
                                              x Conversion Factor ]
                                       +       [Assumed Emission Factor for Surrounding Strata
                                               (m3/tonne)
                                              x Surface Coal Production
                                               (tonnes)
                                              x Conversion Factor ]
                             Where:
                             n   In-Situ Gas Content and Assumed Emission Factor for Surrounding
                                 Strata are described in the text.
                             n   Conversion Factor converts the volume of CH4 to a weight measure
                                 based on the density of methane at 20C and I atm, which is:
                                       1.49 x IO9 m3 per I million metric tons
                       In Equation 3, In-Situ Gas Content represents the methane actually contained in the coal
                       being mined, as determined by measuring the gas content of coal samples. Average values
                       for a coal mine, coal basin or country could be developed, depending on the level of detail
                       in the estimate. For surface mines, unlike underground mines, it is frequently assumed that
                       all of the methane contained in the coal is released during mining and that post-mining
                       emissions from surface mined coals are effectively zero (BTSCRE, 1992; CIAB,  1992;
                       CMRC,  1992). Some countries may choose to modify this assumption based on their
                       specific conditions.  Care should be taken, however, to ensure that estimates of any
                       emissions assumed  to occur during post-mining activities are subsequently prepared.

                       Assumed Emission Factor for Surrounding Strata represents the possibility that more
                       methane will be emitted during surface mining than is contained in the coal itself because
                       of emissions from the strata below (or in limited cases, above) the coal seam. Some
                       countries have assumed that there are not emissions from surrounding strata associated
                       with surface mined  coals (BTSCRE, 1992; CMRC, 1992). If available information indicates
                       that there are gas bearing strata surrounding the mined coal seam and that these strata are
                       emitting their gas in conjunction with the mining, however, countries should include these
                       emissions in their estimates.
                       Emission factors for the surrounding strata can be developed using one of two
                       approaches. Ideally, the assumed emission factor should be based on  an evaluation  of the
                       gas  content of the surrounding strata and verified by measurements.  If such data are
                       unavailable, an alternative method of developing an emission factor is to assume that some
                       multiple of the gas content of the mined coal is emitted by the surrounding strata.  It
                       should be noted that the alternative approach is highly speculative, however, given  the lack
                       of data upon which to base such assumptions.
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                                                                             EMISSIONS FROM  ENERGY
               Post-Mining Activities
               Like surface mining emissions, there are currently few measurements of methane
               emissions from post-mining activities. In fact, many past studies have overlooked this
               emission source, while others have developed only rudimentary estimation methodologies.
               Two possible approaches for estimating emissions from post-mining activities are
               recommended by the IPCC.
               Tier I:  Global Average Method
               For the most simple estimates, a global average emission factor can be multiplied by coal
               production for underground and surface mining, as shown in the equation below. It is
               important to distinguish between underground and surface: mined coals because the gas
               contents are likely to be very different and hence emissions could vary significantly.
                      High CH4 Emissions =
                       (tonnes)
                            EQUATION 4
      TIER I: GLOBAL AVERAGE METHOD - POST-HINING ACTIVITIES
Low CH4 Emissions =      Low CH4 Emission Factor
 (tonnes)          (m3 CH4/tonne of coal mined)
                         x Underground Coal Production
                         (tonnes)
                         x Conversion Factor
                         High CH4 Emission Factor
                         (m3 CH4/tonne of coal mined)
                         x Surface Coal Production
                         (tonnes)
                         x Conversion Factor
Where:
•   Underground Low CH4 Emission Factor = 0.9 m3/tonne
•   Underground High CH4 Emission Factor = 4.0 m3/tonne
•   Surface Low CH4 Emission Factor = 0 nrVtonne
•   Surface High CH4 Emission Factor = 0.2 m3/tonne
•   Conversion Factor converts the volume of CH4 to a weight measure
    based on the density of methane at 20C and I  atm, which is:
          1.49 x I09 m3 per I million metric tons
                Underground Mined Coals: The IPCC recommends emission factors of 0.9 to 4 m /ton
                for underground mined coal, based on recent studies (CIAB, 1992; BCTSRE, 1992; USEPA,
                I993a).
                Surface Mined Coals:  Emission factors of 0 to 0.2 m3/ton are recommended by the IPCC
                for post-mining activities involving surface mined coal (GAB, 1992; CMRC, 1990; USEPA,
                I993a).
                Tier 2:  Country or Basin Specific Method
                Emissions estimates can be refined if additional data are available on coal characteristics.
                This method may be preferable if higher tier methods have been used to estimate
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EMISSIONS FROM ENERGY
                                                         EQUATION 5
                                TIER 2:  COUNTRY OR BASIN SPECIFIC METHOD POST-MINING ACTIVITIES
                             a) Underground CH4  =   In-Situ Gas Content
                                Emissions (tonnes)      (m3 CH4/tonne)
                             Activities (%)
                             When Necessary:
                             b) Surface CH<
                               Emissions (tonnes)

                             Activities (%)
                             Where:
x Fraction of Gas Released  During Post-Mining

x Underground Coal Production (tonnes)
x Conversion Factor

=  In-Situ Gas Content
(m3 CH^/tonne)
x Fraction of Gas Released During Post-Mining

x Surface Coal Production (tonnes)
x Conversion Factor
                                 In-Situ Gas Content and Fraction of Gas Released During Mining are
                                 described in the text
                                 Conversion Factor converts the volume of CH4 to a weight measure
                                 based on the density of methane at 20C and  I atm, which is:
                                       1.49 x  IO9 m3 per I million metric tons
                       In-Sltu Gas Content represents the methane actually contained in the coal being mined, as
                       determined by measuring gas contents in coal samples. Average values for a coal mine, coal
                       basin or country could be developed, depending on the level of detail in the estimate.

                       Fraction of Gas Released During Post-Mining Activities represents the percentage of the
                       in-sicu gas content that is assumed to be emitted during post-mining activities. There are
                       three key issues related to the development of this fraction:
                       •    For Surface Mined Coal: In most cases, if the Tier 2 approach is used to estimate
                            methane emissions from surface mines, post-mining emissions from surface mined
                            coals are assumed to be zero. In these cases, the use of Equation 5(b) is unnecessary
                            and countries should be careful to avoid double-counting. If a country has not
                            assumed that all of the methane contained in surface mined coal is released during
                            mining, however, Equation 5(b) should be used to estimate post-mining emissions and
                            the value selected for "Fraction of Gas Released During Post-Mining Activities"
                            should be consistent with the previous assumption used.

                       •    For Underground Mined Coal: The assumed fractions for underground mining will
                            be based on information about coal permeability, desorption rates, mining methods
                            and other factors. Recent studies have assumed that 25 to 40 percent of the in-situ
                            CH< content of underground mined coal is emitted during post-mining activities
                            (USEPA. I993b; BCTSRE, 1992).

                       •    Potential Fraction of Methane Not Emitted: It is currently assumed that all of the
                            CH| contained in mined coal will be emitted to the atmosphere, although it is
                            possible that a fraction could remain in the coal until the point of combustion and be
                            burned instead of emitted. At this time, estimates of the extent to which this may be
                            the case have not been developed. If countries have such information, however, they
                            could further incorporate this factor into Equation  5.
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                                                                            EMISSIONS  FROM  ENERGY
              Total Emissions from Coal Mining Activities
              Total methane releases as a result of coal mining activities will be the summation of
              emissions from underground mining (ventilation and degasilkation systems), surface
              mining, and post mining activities. The IPCC recommends that emissions be estimated for
              each of these categories, in tonnes of CH4, then aggregated to determine total national
              methane releases. To the extent that methane is recovered and used that would
              otherwise have been released to the atmosphere during coal mining, the recovered
              quantity should be subtracted from the .emission total.

              Availability and Quality of Activity Data
              Data are readily available to develop general emissions estimates using the Tier I
              approach-die Global Average Methods for underground, surface and post-mining
              activities. For these estimates, the only required data are country statistics on
              underground and surface coal production, which are available from domestic sources, such
              as energy ministries, or from the OECD/IEA, which publishes Coal Information (e.g.,
               I990a) and Coal Statistics (e.g.. I990b). These data are thought to be reliable.

              The IPCC recommends that countries involve their coal mining personnel in the
              development of emissions estimates as much as possible, because of the improved
              accuracy of emissions estimates prepared with more detailed coal and mining data. The
              availability and quality of data collected by mining personnel for mine safety purposes
               should be assessed on a case-by-case basis, however, to ensure that it can be appropriately
               used for preparing emissions estimates.
               The IPCC further recommends that future efforts attempc to better characterize the
               factors affecting methane emissions from coal mining for tiliose countries and emission
               sources with limited data, so as to develop more refined emission factors. Specific
               activities should include:
               •   Obtaining more data on coal and geologic characteristics in selected coal-producing
                   countries;
               •   Monitoring emissions from surface mines and post-mining activities; and,

               •   Monitoring emissions from closed or inactive mining operations, and some other
                   potential methane sources, such as mine water.


                1.8.3  CO2  Emissions  From   Burning Coal
                Deposits  And  Waste  Piles

                Marland and Rotty (1984) estimated that burning  of coal in coal deposits is less than 0.3%
                of total coal produced and that burning of all coal in waste banks in the US. over a ten
                year period would represent less than 1% of U.S. coal consumption. Subsequently, they
                chose to ignore these emissions.
                If these sources are estimated, the amount of coal burned in waste piles and coal deposits
                must be specified along with an emission coefficient that (represents the percentage of coal
                that is carbon times the percentage of carbon oxidized. We suggest an arbitrary value of
                50% of the carbon present in the coal to represent this emission coefficient; this value
                would be highly variable from one country to another and one site to another. This
                assumption of 50% for an emission coefficient should be evaluated to determine its
                validity. The formula for calculating these emissions would be:
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EMISSIONS  FROM  ENERGY
                              Emissions from Coal Burning (I03 mt C) = (Quantity of Coal Burning; I03
                                                            mt)
                                                    X Emission Coefficient
                               (i.e., Percentage of Carbon in Coal X Percentage of Carbon Oxidized;
                                                     default value is 50%)
                      Note that other GHG's such as N2O, CO, NOX, etc. are also emitted from combustion of
                      coal wastes
                       1.8.4 CO2  Emissions  From  SO2  Scrubbing

                      When SO2 scrubbing (or flue gas desulfuization) technology is used in conjunction with
                      combustion of coal, the process which removes sulfur dioxide from the Hue gas also
                      releases CO2 from the chemical interactions during the process. This can be considered a
                      fugitive emission resulting from coal utilization, since the emissions are  emitted only as a
                      result of the combustion process. Typically calcium carbonate reacts with sulfur oxides in
                      flue gas to produce calcium sulfate and release carbon dioxide. Marland and Rotty (1984)
                      suggest that CO2 emissions from SO2 scrubbing are small enough to be ignored in global
                      calculations.  However, for completeness, some national experts may wish to included this
                      subcategory.

                      To estimate carbon emissions from SO2 scrubbing, the approach is derived from Grubb
                      (1989) with slight modifications. In Grubb's approach, carbon emissions would equal the
                      total amount of coal scrubbed times the fraction of sulfur by weight in the coal, adjusted
                      for the differences in molecular weight between carbon and sulfur (12/32). Since this
                      procedure assumes that all of the sulfur is removed, it should be adjusted by the sulfur
                      removal efficiency of die desulfurization process (an average removal efficiency of 90% is
                      suggested). The formula for calculating these emissions would be:
                             Emissions from SO2 Scrubbing (I03 mt C) = (Total Coal Consumption; I03
                                                            mt)
                                                   X Fraction Scrubbed (%)
                                         X Average Sulfur Content of Coal Scrubbed (%)
                                        X Sulfur Removal Efficiency (default value is 90%)
                                             X 12/32 (i.e., the Carbon/Sulfur Ratio)
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                                                                             EMISSIONS FROM ENERGY
       1.9    Fugitive  Emissions From  Oil  And  Natural
                Gas Systems
                1.9.1   Overview

                This section covers "fugitive" emissions of greenhouse gases- (GHGs) from oil and natural
                gas systems. This category includes all emissions from production, processing handling and
                transport of oil and natural gas, and their derivative products, which are not the result of
                combustion of these oil, gas or other products as fuel. It excludes use of oil and gas of
                derived fuel products to provide energy for internal use in energy production processing
                and transport The latter are considered fuel combustion and treated in earlier section of
                this chapter.
                By far the most important components of this sub-category are methane emissions from
                oil and gas production, and from all aspects of natural gas systems. The bulk of this section
                identifies and describes different methane emission sources from oil and gas  systems and
                presents a default methodology to estimate these emissions, on a national level. The basis
                for estimating methane emissions from oil and gas systems is, however, weak for most
                regions at this time. Only a few detailed studies of emissions rates have been performed.
                Better emissions data that take into account region- and country-specific factors are
                needed. Currently available information indicates that gas  production and transportation in
                the former USSR and Eastern Europe are by far the most important sources, accounting
                for perhaps 50 percent of global CH4 emissions from oil and gas systems. Because the data
                are so limited at present, global and regional estimates of CH4 emissions from this source
                category, should be considered highly uncertain.
                Oil and gas systems are also responsible for significant fugitive emissions of CO2, NOX, and
                especially NMVOC during production from venting and flaring; and from leakages at all
                stages. No original work has been done on CO^ NOX, and NMVOC emission from oil and
                natural gas systems, within the IPCC/OECD programme, consistent with the programmes
                priorities for the first phase. Considerable information has been developed in other
                national and international emissions inventory programmes,, however, because of the
                importance of these gases for local and regional (as well as global) pollution. This is
                especially the case
                for NMVOC as fugitive emissions from production, processing and distribution of oil and
                oil products is a major source of this gas. References to some of the available sources of
                emission factor data and other information for calculating emissions from this category are
                provided in the last sub-section of this section.
                 1.9.2  Fugitive Methane  Emissions

                Background
                Fugitive emissions from oil and gas systems are an important source of methane, probably
                accounting for about 30 to 60 Tg per year of emissions. Meithane is emitted during Oil and
                gas production, processing, storage, transportation and distribution. "Fugitive" sources of
                emissions within oil and gas systems include: releases during normal operation, such as
                emissions associated with venting and flaring during oil and gas production, chronic leaks
                or discharges from process vents; emissions during routine maintenance, such as pipeline
                repair; and emissions during system upsets and accidents.
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                       Oil and Natural Gas System Overview: Oil and gas systems are divided into three
                       main parts, for this discussion:

                        I    Oil and Gas Production: Oil and gas are withdrawn from underground formations
                            using on-shore and off-shore wells. Oil and gas are frequently withdrawn
                            simultaneously from the same geologic formation, and then separated. Gathering lines
                            are generally used to bring the crude oil and raw gas streams to one or more
                            collection point(s) within a production field. Because methane is the major
                            component of natural gas, leaks or venting from these systems result in methane
                            emissions. Oil and/or gas are produced in approximately  186 countries worldwide.

                       2   Crude Oil Transportation and Refining: Crude oil is transported by pipelines
                            and tankers to refineries. Often, the crude oil is stored in tanks for a period of time.
                            Methane is usually found in the crude oil stream, and leaks or venting of vapours
                            from these facilities result in methane emissions, particularly from crude oil tankering.
                            Methane emissions from crude oil streams are strongly dependent on the original
                            methane content of the crude oil and its preparation for transport.

                            Refineries process crude oil into a variety of hydrocarbon products such as gasoline
                            and kerosene. During the refining process, methane and other hydrocarbons are
                            separated and methane may be leaked or vented in some processes;. Refinery
                            outputs, referred to as  "refined products," generally contain negligible amounts of
                            methane. Consequently, methane emissions are not estimated for transporting and
                            distributing refined products. Refineries are operated in 102 countries.
                        3   Natural Gas Processing, Transportation, and Distribution: Natural gas is
                            processed to recover heavier hydrocarbons, such as ethane, propane and butane, and
                            to prepare the dried gas for transporting to consumers. Most gas is transported
                            through transmission and distribution pipelines. A small amount of gas is shipped by
                            tanker as liquefied natural gas (LNG). Because only a small portion of gas is
                            transported as LNG, emissions from LNG facilities are not included in default
                            emission methods.
                            The following are the main processing, transportation, and  distribution activities:

                            •    Gas processing plane Natural gas is usually processed in gas plants to produce
                                 products with specific characteristics. Depending on the composition of the
                                 'unprocessed gas, it is dried and a variety of processes may be used to remove
                                 most of the heavier hydrocarbons, or condensate, from the gits. The processed
                                 gas is then injected into the natural gas transmission system and the heavier
                                 hydrocarbons are marketed separately. Unintentional leaks of methane occur
                                 during natural gas processing.
                            •    Transmission pipelines: Transmission facilities are high pressure lines that
                                 transport gas from production fields, processing plants, storage facilities, and
                                 other sources of supply over long distances to distribution  centres, or large
                                 volume  customers. Although transmission lines are  usually buried, a variety of
                                 above ground facilities support the overall system including metering stations,
                                 maintenance facilities, and compressor stations located along the pipeline
                                 routes.
                            Compressor stations, which maintain the pressure in the pipeline, generally include
                            upstream scrubbers where the incoming gas is cleaned of particles and liquids before
                            entering the compressors. Reciprocating engines and turbines are used to drive the
                            compressors. Compressor stations normally use pipeline gas to fuel the
                            compressors. They also use the gas to fuel electric power generators to meet the
                            station's electricity requirements.    ,
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                                                                               EMISSIONS  FROM ENERGY
                     •    Distribution systems: Distribution pipelines are extensive networks of generally
                          small diameter, low pressure pipelines. Gas enters distribution networks from
                          transmission systems at "gate stations" where the pressure is reduced for
                          distribution within cities or towns.
                Sources of Methane Emissions in the Oil and Natural Gas Systems: Emissions
                from oil and gas systems can be categorized into: (I) emissions during normal operations;
                (2) routine maintenance; and (3) system upsets and accidents. In Table 1-38 these emission
                types are linked to the different stages in oil and gas systems. Typically the majority of
                emissions are from normal operations.

                I    Normal Operations: Normal operations are the day-to-day operations of a facility
                     absent the occurrence of abnormal conditions.  Emissions from normal operations
                     can be divided into two main source categories: (I) venting and flaring and (2)
                     discharges from process vents, chronic leaks, etc.

                     Venting and Flaring - Venting and flaring refers to the disposal of gas that cannot be
                     contained or otherwise handled. Such venting and flaring activities are associated with
                     combined oil and gas production and take place in production areas where gas
                     pipeline infrastructure is incomplete and the natural jps is not injected into reservoirs
                     (Emissions from process vents are not included here - see next  sub-section).

                     Venting activities release methane because the vented gas typically has a high
                     methane content If the excess gas is burned in flares the emissions of methane will
                     depend on how efficient the burning processes are. Generally the combustion
                     efficiency for flare sources are assumed to be between 95 and 100%. However a new
                     study based upon measurements carried out by Norwegian Oil  Industry Association -
                     OLF (Forthcoming) indicates very small amounts of unburned methane from flares,
                     less than 0.1% of the gas burned. To estimate the methane emissions from venting
                     and flaring activities satisfactorily it is required to know the flare efficiency rates and
                     the distributed quantity of gas vented and gas flared.
                     The combined quantity of gas vented and flared is reported by countries that produce
                     oil and gas (Barns et al., 1990). A few countries also are able to  report the
                      distribution between gas vented and gas flared. The reliability of the data is
                     questionable in many cases because vented and flared amounts normally are not
                      metered and are often an "accounting balance" whereby withdrawal totals are set
                      equal to disposition totals by putting any discrepancies in the estimates in  the
                      category of vented and flared.
                      Discharges from Process Vents. Chronic Leaks etc. - Methane emissions will also
                      occur when gas pipelines infrastructure is available and the market for  natural gas is
                      well developed. Oil and gas production, gas processing, oil and gas transportation and
                      gas distribution facilities emit methane due to a wide variety of operating practices
                      and factors, including:

                      •     Emissions from pneumatic devices (gas-operated controls  such as valves and
                           actuators). These emissions depend on the size, type, and  age of the devices,
                           the frequency of their operation, and the quality of their maintenance.
                      •     Leaks from system components. These emissions are unintentional and usually
                           continuous releases associated with leaks from the failure  of a seal or the
                           development of a flaw, crack or hole in a component designed to contain or
                           convey oil or gas. Connections, valves, flanges, instruments, and compressor
                           shafts can develop leaks from flawed or worn seals, while  pipelines and storage
                           tanks can develop leaks from cracks or from corrosion.
                      •     Emissions from process vents, such as vents on glycol dehydrators and vents on
                           crude oil tankers and storage tanks. Vapours, including methane,  are emitted
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EMISSIONS  FROM  ENERGY
                                 from the vents as part of the normal operation of the facilities. However such
                                 process vents are minor methane sources in most gas production facilities.
                            •    Emissions from starting and stopping reciprocating engines and turbines.
                            •    Emission during drilling activities, e.g., gas migration from reservoirs through
                                 wells.

                        2   Routine Maintenance: Routine maintenance includes regular and periodic activities
                            performed in the operation of the facility. These activities may be conducted
                            frequently, such as launching and receiving scrapers (pigs) in a pipeline, or
                            infrequently, such as evacuation of pipes ("blowdown") for periodic testing or repair.
                            In each case, the required procedures release gas from the affected equipment.
                            Releases also occur during maintenance of wells ("well workovers") and during
                            replacement or maintenance of fittings.
                        3   System Upsets and Accidents: System upsets are unplanned events in the
                            system, the most common of which is a sudden pressure surge resulting from the
                            failure of a pressure regulator. The potential for unplanned pressure surges is
                            considered during facility design, and facilities are provided with pressure relief
                            systems to protect the equipment from damage due to the increased pressure.
                                 Relief systems vary in design. In some cases, gases released through relief valves
                            may be collected and  transported to a flare for combustion or re-compressed and
                            re-injected into the system. In these cases, methane emissions associated with
                            pressure relief events will be small. In older facilities, relief systems may vent gases
                            directly into the atmosphere or may send gases to flare systems where complete
                            combustion may not be achieved.
                            The frequency of system upsets varies with the facility design and operating practices.
                             In particular, facilities operating well below capacity are less likely to experience
                             system upsets and related emissions. Emissions associated with accidents are also
                             included under the category of upsets. Occasionally, gas transmission and distribution
                             pipelines are accidentally ruptured by construction equipment or other activities.
                             These  ruptures not only result in methane emissions, but they can be extremely
                             hazardous as well.
                             Table  1-38 lists those emissions types that are the most important: sources within
                             each segment of the oil and gas industry. Based on available information, the sources
                             listed as "major" account for the majority of emissions from each segment Because
                            •data are limited and there is considerable diversity among oil and gas systems
                             throughout the world, other potential sources are also listed which  may, in  some
                             cases,  be important contributors to emissions.
                        Available Emissions Data: Only very limited data are available that describe methane
                        emissions from natural gas and oil systems. Estimating the types of emissions defined above
                        is complicated by the fact that emissions rates from similar systems in various regions and
                        countries are influenced by differences in the industry's supporting infrastructure,
                        operating and maintenance practices, and level of technology used. Because natural gas and
                        oil systems  are comprised of a complex set of facilities, simple relationships between
                        emissions and gross descriptors of the systems are not easily defined.
  1.106

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                                                                                  EMISSIONS  FROM  ENERGY
                                                      TABLE 1-38
                                     EMISSIONS FROM OIL AND NATURAL GAS SYSTEMS
                     Segment
          Oil and Gas Production
                  Oil and Gas Wells
                  Gathering lines
                  Treatment facilities
          Grade oil transportation and
          Refining
                  Pipelines
                  Tankers
                  Storage tanks
                  Refineries
          Natural Gas Processing,
          Transportation, and
          Distribution
                  Gas Plants
                  Underground storage
                  reservoirs
                  Transmission Pipelines
                  Distribution Pipelines
    Major Emission Sources
Venting
Normal operations: fugitive
emissions; deliberate releases from
pneumatic devices and process vents
Normal operations: fugitive
emissions; deliberate releases frortii
process vents at refineries, during
loading and unloading of tankers arid
storage tanks
Normal operations: fugitive
emissions; deliberate releases from
pneumatic devices and process vents
    Other Potential Emission
            Sources
Flare and combustion in e.g. gas
turbines, 1C engines.
Routine maintenance
System upsets and Accidents
Combustion in e.g. gas turbines, 1C
engines.
Routine maintenance
System upsets and Accidents
Combustion in e.g. gas turbines, 1C
engines
Routine maintenance
System upsets and Accidents
                 To estimate emissions, the available published data were reviewed to identify emissions
                 estimates that include: a detailed consideration of the physical attributes of oil and gas
                 systems; theoperation and maintenance characteristics of key facilities; and country- or
                 region-specific factors that may influence emissions rates. The following data were
                 identified:

                 •    Surveys: Several studies have surveyed system operators to estimate emissions as a
                      portion of production or throughput. These studies include Alphatania (1989), AGA
                      (1989), and INGAA (1989). While these studies provide a basis for identifying the
                      portions of the systems that operators believe are likdy to be major sources of
                      emissions, they are not based on detailed assessments of emissions rates.
                      Consequently, these studies do not provide a quantitative basis for making estimates
                      of methane emissions from oil and natural gas systems;.

                 •    Estimates Based on Reported Unaccounted For Gas: Several studies, such as
                      Hitchcock and Wechsler (1972), Abrahamson (1989) and Cicerone and Oremland
                      (1988), have assumed that emissions can be approximated by reported amounts of
                      "unaccounted for" gas. Unaccounted for gas is defined as the difference between gas
                      production and gas consumption on an annual basis. Like estimates of venting and
                      flaring, unaccounted for gas often is used as an accounting convenience to balance
                      company or national production and consumption estimates.

                      •    The applicability of unaccounted for gas estimates is  very limited because factors
                           other than emissions account for the majority of the gas listed as unaccounted
                           for, including: meter inaccuracies, use of gas within the system itself, theft of gas
                           (PG&E,  1990), variations in temperature and pressure and differences in billing
                           cycles and accounting procedures between companies receiving and delivering
                           the gas (INGAA, 1989). Furthermore, because known releases of gas are not
PART 2
                                                                          1.107

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EMISSIONS FROM ENERGY
                              reflected in unaccounted for gas estimates, such as emissions from compressor
                              exhaust, the unaccounted for gas estimates cannot unambiguously be
                              considered an upper or lower bound on emissions.
                              Engineering Studies and Measurements: A small number of studies are based on
                              detailed engineering and/or field measurement analyses. Several
                              engineering analyses have considered the manner in which actual or
                              model facilities are built and operated, andextrapolate facility emissions
                              to a system-wide basis. Several measurement studies have measured
                              emissions from operating facilities or identified actual leaks and
                              extrapolated these measurements to estimate system-wide emissions.
TABLE 1-39.
SUMMARY OF EMISSION FACTORS
Data source!
EPA (1992)
All emissions have been
scaled down to 1988 energy
consumption or production
levels
Study methodology
Compilation of estimates
from detailed engineering
analyses and field
measurement studies
Emission factors
Applicability
Oil and Gas Production:
290 - 4670 kg/PJ of oil produced
39590- 104220 kg/PJ of gas
produced
2870 - 13920 kg/PJ of total oil and
gas produced
Emissions from non-gas
producing oil wells including
fugitive emissions and routine
maintenance emissions in the
US.
Emissions from gas production,
including fugitive emissions,
dehydrator venting, bleeding
from pneumatic devices, routine
maintenance, and systems upsets
in the U.S.
Venting and flaring emissions
from oil and gas production and
fugitive emissions from gas
producing oil wells in the U.S.
Crude Oil Transportation and Refining:
110- 1666 kg/PJ of oil refined
Emissions from oil refining and
related oil storage tanks in the
U.S.
Natural Gas Processing, Transmission acid Distribution:
59660- II 66 10 kg/PJ of gas
consumed
Emissions from gas processing,
transmission and distribution
including fugitive emissions,
dehydrator venting, bleeding
from pneumatic devices, routine
maintenance, and system upsets
in the U.S.
                       Generally, data from engineering studies and measurements are the preferred
                       basis for making estimates. Unfortunately, only several of these types of studies
                       have been performed, which limits the ability to estimate emissions nationally,
                       regionally and globally from oil and gas systems. Table 1-39 lists the studies
                       identified and the information they contain. The emissions estimates from the
  1.1 08

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                                                                         EMISSIONS  FROM  ENERGY
               studies in the table have been converted to common units of kilograms of
               emissions per petajoule of energy (kg/PJ). A total of 5 studies are listed, with
               emissions estimates for portions of North America (EPA, 1992), Eastern Europe
               (Rabchuk et al.. 1991), and Western Europe (Schneider-Fresenius et al.. 1989,
TABLE 1-39
CONTINUED): SUMMARY OF EMISSION FACTORS
Data source
Rabchuk etal. (1991)
Schneider-Fresenius et al.
(1989)
Barns etal. (1990)
Study Methodology
Compilation of estimates from
previous measurement studies
and from official data for 1 989
Compilation of results from the
Batelle study's 1988 literature
survey
Compilation of official reports
and projections on
international emissions
Emission Factors
Applicability
Oil and Gas Production:
218000 - 567600 kg/P) of gas
produced
Emissions from leakages at gas wells
including routine equipment venting
in the former USSR
Natural Gas Processing, Transmission and Distribution:
340000 - 715800 kg/PJ of gas
consumed
Emissions from leakages at
underground storage facilities,
compressor stations, linear part of
main pipelines and distribution
networks in the former USSR
Oil and Gas Production:
14800 - 27000 kg/PJ of gas produced
Emissions from gas production and
treatment facilities in Germany
Natural Gas Processing, Transmission and Distribution:
58000 - 1 1 1000 kg/PJ of gas consumed
Emissions from transportation,
distribution and storage of gas in
Germany
Oil and Gas Production:
96000 kg/PJ of natural gas production
6300- 1019000 kg/PJ of gas
production
Emissions from gas production and
separation facilities in the world
Emissions from venting and flaring
activity by region of the world
               Norwegian SPCA, 1992 and Norwegian Oil Industry Association, 1993 in prep.).
               Additionally, Barns etal. (1990) present estimates based on a global assessment. Additional
               studies of this type are needed to improve the basis for making emissions estimates.
                1.9.3  Methodology For  Estimatiing  Emissions

               A three tiered approach is presented for estimating CH4 emissions from oil and gas
               systems. The specific tiers are listed below in the order of increasing sophistication, data
               requirements, and accuracy:

               •    Tier I - Production Based Average Emissions Factors,

               •    Tier 2 - Mass Balance, and

               •    Tier 3 - Rigorous Source-specific Evaluations
PART  2
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EMISSIONS  FROM ENERGY
TABLE 1-39 (CONTINUED)
SUMMARY OF EMISSION FACTORS
Data Source
Norwegian SPCA (1992)
Norwegian Oil Industry
Association (OLF), 1993 (in
prep.)
Study Methodology
Summary of emissions
estimates for 1989 based on
nformation and measurements
collected from oil companies
and industry associations
Summary of emission estimates
based on information and
measurements collected from
oil associations
Emission Factors
Applicability
Oil and Gas Production:
12800 kg/PJ of gas produced
3200 kg/Pj of gas produced
200 kg/PJ of gas produced
Emissions from cold vents and
Fugitive emissions
Flare and gas turbines
Pre-production emissions (Well
testing)
Crude oil transportation:
2500 kg/PJ oil tankered
Emissions from offshore loading of
crude oil
Natural gas processing:
1800 kg/PJ of gas processed
Emissions from one Norwegian gas
processing terminal
Oil and Gas Production:
3000 - 7500 kg/PJ of gas produced
1 00 - 400 kg/Pj of gas produced
Emissions from cold vents and
fugitive emissions
Pre-production emissions
                       The intent is to allow countries to select an approach or combination of approaches that
                       may be most suited to their circumstances. Some important considerations may include
                       the relative cohtribution of oil and gas systems to total CH4 emissions for the country, the
                       available information and resources, and the complexity of the local oil and gas industry.

                       Regardless of the method that is used, the results must be aggregated back to a Tier I
                       format to provide a consistent basis for comparison. Moreover, CH4 emissions due to
                       incomplete combustion by flares and other process combustion equipment are excluded
                       from these calculations; they are accounted for separately in the section on CH4 emissions
                       from combustion and industry.
                       Tier I - Production Based Average Emission Factors
                       This is the simplest approach  for estimating CH4 emission from oil and gas systems, and is
                       the only one that does not require any direct interaction with the oil and gas industry and
                       associated regulatory agencies. Accordingly, it is the least reliable of the methods.
                       The required activity data may be easily referenced from a published documents of the IEA
                       or the United Nations Statistical Division, and the necessary emission factors are provided
                       in this document. The production based average emission  factors approach can be used as
                       a starting point for any country, and may be all that is needed where the emissions from a
                       country's oil and gas industry are comparatively small and/or where data or resources are
                       not available to pursue a more rigorous approach.
  I.I 10

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                                                                                 EMISSIONS FROM  ENERGY
                 Production Base: To estimate emissions, the following steps are recommended as a
                 default estimation procedure:

                 I    Global oil and gas systems have been divided into regions with the objective of each
                     region having relatively homogeneous oil and gas system characteristics. Each country
                     should decide which system characterisation best fits its own oil and gas system(s).

                 2   For each region, representative emissions factors for ea.ch emissions type within each
                     segment have been selected with the objective of taking into account the various
                     system designs and operating practices found in each region.

                 3   For each country, country-specific activity levels must be obtained and multiplied by
                     the appropriate emissions factor. Emissions factor for countries should be selected
                     from those corresponding to the appropriate region.

                 As more data become available for oil and gas producing activities within different
                 countries, the default methodology described above (including activity data and emission
                 factors) should be refined. Each step is discussed below in more detail.
                 Regional Definitions: Regions have been defined considering the limitations in data on
                 emissions factors and activity levels, but also recognizing the key differences in oil and gas
                 systems that are found globally. The following 5 regions are recommended at this time:
                 •    U.S. and Canada: The U.S is a large producer and importer of oil and is a large
                      producer of gas. Detailed emissions estimates are available for the U.S.
                 •    Former USSR and Eastern Europe:  Indications are that emissions rates from this
                      region are much higher than emissions rates from other regions, in particular for the
                      gas system. This region includes the former USSR (which is by far the largest oil and
                      gas producer in the region), Albania, Bulgaria, Czech & Slovak Republics, Hungary,
                      Poland, Romania, and the former Yugoslavia.
                 •    Western Europe:  This region is a net importer of oil and gas, and mainly produces
                      oil and gas off shore. This region includes: Austria, Belgium, Denmark, Faroe Islands,
                      Finland, France, Germany, Gibraltar, Greece, Iceland, Ireland, Italy, Luxembourg,
                      Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and UK.
                 •    Other Oil Exporting Countries: This region includes the world's other major oil
                      producing countries: the 13 OPEC members (Algeria,  Gabon, Libya, Nigeria, Ecuador,
                      Venezuela, Indonesia, Iran, Iraq, Kuwait, Qatar, Saudi Arabia and the United Arab
                      Emirates) and Mexico. Generally, these countries produce large quantities of oil and
                      have limited markets for gas.

                 •    Rest of the World: This region includes the remaining countries of Asia, Africa,
                      Middle East, Oceania and Latin America.
                 In defining these regions, countries were aggregated with relatively similar oil and gas
                 systems. Additional investigation would likely improve the definition  of the regions.
                 Emissions Factors: As discussed above, the basis for selecting emissions factors is weak
                 because very few detailed studies of emissions have been performed. Using the
                 information summarized in Table  1-39, emissions factors should be selected by industry
                 segment and emissions type for each of the regions. In some cases data from  the U.S. were
                 used when region-specific information was not available.
                 Tables 2-42 through 2-46 list suggested emissions factors for each region. Emissions
                 factors from EPA (1992) were used for the U.S. Key emissions factors for Eastern Europe
                 and the Former USSR were taken from Rabchuk et al. and EJarns et al. Estimates were
                 used for emissions factors for venting and flaring for the several regions, including Eastern
                 Europe.
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I. I I  I

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EMISSIONS FROM  ENERGY
                       Studies by Schneider-Fresenius et al. and Norwegian SPCA were adopted as
                       representative of emissions factors for Western European gas production and venting and
                       flaring. No region-specific data were available for the Other Oil Exporting countries and
                       the Rest of the World. Emissions factors in these regions are expected to fall between the
                       relatively low rates found in North America and Western Europe and tine relatively high
                       rates found in Eastern Europe. Consequently, a range of emissions factors is suggested for
                       these regions unless more information can be obtained.
                       Activity Levels: Data on the quantity of oil and gas produced, refined, and consumed can
                       be obtained from the IEA or the U.N. Statistical Division. Sources are described in the
                       introduction to this chapter. Data on oil refining capacity can be used to approximate oil
                       refined. Data on oil tankered were not available by region. It is important for national
                       experts to ensure that production figures used in calculation of apparent consumption for
                       CO2 emissions estimates (described in section B of this Chapter) are consistent with
                       those used in this section.
                       Tier 2 - Mass Balance
                       The mass  balance approach employs standard, generally easy-to-obtain, oil and gas data
                       (i.e., production volumes, gas-to oil ratios (GORs), and gas compositions) to estimate the
                       maximum amount of methane that could potentially be available for emissions to the
                       atmosphere by different sectors of the oil and gas industry. These amounts are then
                       adjusted to reflect actual emissions by applying appropriate system adjustment and loss
                       factors. The system adjustment factors account for the amount of gas that is disposed by
                       control devices, consumed by combustion equipment, conserved, or reinjected. Loss
                       factors account for specific losses from these control/utilization systems.
                       A particular advantage of conducting a mass balance analysis is that it helps avoid any
                       double counting of emissions. This may be most important in the crude oil transportation
                       and refining sector where the methane fraction is difficult to track.
                       The basic procedures for performing the mass balance calculations are delineated below
                       by sector of the oil and gas industry. Total CH4 emissions is the sum of emissions for each
                       of these sectors. Default data and factors are provided where possible.
                       Oil and Associated Gas Production: Emissions from oil and associated gas production
                       may be estimated using the relation,
                                                                 M,

                                                                  'STP

where
Eoil     =
Qoil    =
GOR   =
YAGCH4=
MCH4  =
gc
                                   rnass (Tg) of CH4 emitted to the atmosphere due to oil and associated gas production,
                                   volume of oil produced (mj /y),
                                   gas to oil ratio (mj /mj ),
                                   average mole fraction of CH4 in the associated gas (dimensionless),
                                   molecular weight of CH4
                                   16,043.
                                   volume (m* ) of I kmole of gas at reference temperature and pressure of the GOR factor
                                   (e.g., 23.645 mj  at 15 C and 101.325 kPa),
                                   system adjustment factor which accounts for any gas utilization, conservation and disposal
                                   schemes  and their effectiveness (dimensionless).
                                   constant of proportionality,
                                   IO"7.
 I.I 12

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                                                                               EMISSIONS  FROM ENERGY
               The value of the system adjustment factor is determined using the equation presented
               below.
KO« =
   p
                                              L+(
                                           fared

                where,
                QAG    =       volume of associated gas disposed by control devices (e.g., flare
                                systems), consumed (burned as fuel) or conserved (reinjected or sold)
                                and therefore unavailable for emission to the atmosphere (nT3 ), and

                L       =       loss factors that account for emissions from the gas control and
                                utilization systems (e.g., losses due to fugitive equipment leaks,
                                blowdown activities, and use of natural gas as the supply medium for
                                gas-operated devices). (Note: Emissions due to incomplete combustion
                                are accounted for in the section on CH4  from combustion and
                                industry.)

                If none of the associated gas is controlled or utilized (i.e., L< = I for all x), then the system
                adjustment factor (K) is equal to one. This situation occurs when it is not economical to
                conserve or reinject the gas (e.g., there is no local market for the gas  and the volumes are
                relatively small) and when venting of the gas is preferable to disposal by flaring. It is not
                necessary to evaluate the different paths by which CH4 emissions may occur (e.g., fugitive
                equipment  leaks, process venting, system upsets, etc.) in these cases since the end effect is
                the same: essentially all the CH4 produced is emitted to the atmosphere.
                If all of the  associated gas is controlled or utilized (i.e., none is vented), then the value of
                the system  adjustment factor will be nearly equal to zero. The difference from zero is due
                to fugitive leaks, blowdown activities and other system losses.
                Crude Oil Transportation and Refining: The crude oil from production facilities will
                initially contain a certain amount of gas in solution. This gas, particularly the CH4 fraction,
                evaporates quickly as this oil progresses through the storage and transportation systems
                enroute to the refinery. When the oil reaches the refinery, it is usually fully weathered and
                essentially free of any CH4 .
                Accordingly, the basic mass balance relation for oil transportation and refining activities
                may be expressed as follows:
                                                                A
                                                                  CH.
                 where,
                 FSG     =
                 YSGCH4
                 gc
           solution gas factor (m3 /m3 ),
           mole fraction of CH4 in the solution gas (dimensionless),

           system adjustment factor to account for the amount of vapour collected
           and subsequently flared, incinerated or recovered, and
           constant of proportionality,
           10-9.
PART 2
                                                                                                                   I.! 13

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EMISSIONS  FROM  ENERGY
                      The value of the solution gas factor and the corresponding mole fraction of methane is
                      determined by the type of crude oil (light, medium, heavy, or crude bitumen), the
                      composition of the associated gas, and the initial vapour pressure of the crude oil when it
                      is placed in the storage tanks or compartments at the production site. Typically, the initial
                      vapour pressure will be equal to the operating pressure of the first vessel upstream of the
                      storage facilities.

                      Table I -40 presents some estimated values for these two parameters at onshore and
                      offshore  facilities.  Better estimates may be determined by performing site specific process
                      simulations.
                      The value of the system adjustment factor is determined using the equation below:

                                                   K_ I
                                                   -'"
                                                              T^oil
                       In the absence of any data regarding the volume of CH4  collected, the value of system
                       adjustment factor should be set to a default value of one.
                       Exploration and Drilling Losses
                       Total CHH emissions from the exploration and drilling sector will usually be small
                       compared to the amount emitted by other sectors of the oil and gas industry.
                       Consequently, a simple Tier I approach is perhaps most appropriate for use here.
                       The basic relation is shown below:
                                                        ED — Nw(,i|. . Fn
                       where.
                       ED     =      total CH4 emissions (Tg) from drilling and testing of oil and gas wells,

                       Nwcits   =      number of wells drilled and tested, and

                       FD     =      average amount of CH4 emitted per well (Tg/well).

                       Gas Systems - Production, Processing and Transmission: Methane emissions from
                       gas systems may be estimated by applying appropriate loss factors to the total volume of
                       gas that passes through the different stages of the system, and by adding to this value
                       emissions do to accidental releases (e.g., pipeline ruptures and well blowouts). This latter
                       component can be quite significant for gas systems in developing countries.
TABLE 1-40 SOLUTION GAS FACTORS AND CORRESPONDING CH4 MODE FRACTIONS FOR DIFFERENT TYPES
OF CRUDE OIL PRODUCTION AT ON SHORE AND OFFSHORE FACILITIES
Type of Crude Oil
Light
Medium
Heavy (Primary)
Heavy (Thermal)
Onshore Facilities
FSG
3.3 to 5.0
3.2 to S.O
1.0
8.3
YCH4
0.5642
0.1001
0.8723
0.6666
Offshore Facilities
FSG
n.a.
n.a.
n.a.
n.a.
YCH4
n.a.
n.a.
n.a.
n.a.
I.I 14

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                                                                               EMISSIONS  FROM ENERGY
                The resulting mass balance relation for gas systems is as follows:
                                gas  Logos'\gasG   gasp  gasj  ^accidents-'  gasCH'  CHJ/'°c
                where,

                Egas
                Qgas


                Lgas_
                total CH4 emissions (Tg) from gas systems,

                total volume of natural gas produced into the gas system (possibly including some
                associated gas) (1113),
                loss factors for the gathering/production (G), processing (P) and transmission (T) stages
                of the system  (dimensionless),
                Qaccidents =    total volume of unburned natural gas released into the atmosphere due to major
                                accidents such as pipeline ruptures and well blowouts (mj), and
                gc
                average mole fraction of CH4 in the produced gas dimensionless),

                constant of proportionality,
                                 ID'7
                The loss factor for a given stage "i" of the gas system may be estimated using a relation,
                                                        0,   +0
                                                        Meats,  ^venting.
                                                   gas~      Q
                                                     1        ^as
                                volume of gas lost to the atmosphere due: to fugitive equipment leaks (mj ), and
where,

Qleaksi
Qventingi   =    volume of gas lost to the atmosphere duei to process venting and use of natural gas as
                the supply medium for gas operated devices (m3).

Table 1-41 presents some default values for the different loss factors.
TABLE 1-41
DEFAULT LOSS FACTORS FOR DIFFERENT STAGES OF ONSHORE AND OFFSHORE NATURAL GAS
SYSTEMS.
Stage
Gathering/Production
Processing
Transmission
Onshore
0.2 to 1.0
0.04 to 0.10
0,03 to ?
Offshore
n.a.
n.a.
n.a.
                 Tier 3 - Rigorous Source-specific Evaluations

                 Rigorous source-specific evaluations will generally involve compiling the following types of
                 information and may require significant interaction with industry and associated regulatory
                 agencies:

                 •    detailed inventories of the amount and types of process infrastructure (e.g., wells,
                      minor field installations, a major production and processing facilities),
PART 2
                                                                                                 I.I 15

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EMISSIONS FROM ENERGY
                       •    production disposition analyses (e.g., oil and gas production; vented, flared and
                            reinjected volumes of gas; and fuel gas consumption),

                       •    accidental releases (i.e., well blow-outs and pipeline ruptures),
                       •    typical design and operating practices and their impact on the overall level of
                            emission control.
                       The amount of emissions is then assessed by applying appropriate emission factors,
                       empirical correlations, process simulation results, and field measurements to these data.

                       Some examples of detailed emission inventories that have been developed in this manner
                       are listed below:
                       •    U.S. Environmental Protection Agency (U.S. EPA). Anthropogenic Methane Emissions
                            in the United States. Estimates for 1990: Report to the Congress. October 1992.
                       •    Picard,  D.J., B.D. Ross, and D.W.H. Koon. A Detailed Inventory of CH4 and VOC
                            Emissions from Upstream Oil and Gas Operations in Alberta. Clearstone
                            Engineerineg Ltd., for the Canadian Petroleum Association, Mars 1992.
                       •    UK Offshore Operators Association Ltd. Methane Emissions From Offshore Oil &
                            Gas Exploration & Production Activities. Submitted to The Watt Committee on
                            Energy. 1993.
                       •    Norwegian  Oil Industry Association  - OLF. Report from OLF Environmental
                            Programme - Phase 2. Will be available Mars 1993.
                        1.9.4  Uncertainty

                        Because relatively few detailed emissions studies have been conducted, the emissions
                        estimates resulting from application of these methodologies must be considered very
                        uncertain. The overall magnitude of the emissions that will be obtained for some countries
                        is driven by two key studies:
                        •    Rabchuk et al. report that emissions from gas production and transportation  in the
                            former USSR is very high, about 3 to 7 percent of total gas production. Recent visits
                            to this region indicate that system construction, maintenance, and operations may be
                            consistent with high  emissions rates (Craig, 1992). However, a  better quantitative
                            evaluation is needed to validate the current emissions estimates.
                        •    Barns et al. report emissions from venting and flaring by region. The emissions
                            estimates for the OPEC countries are relatively high, and account for most of the
                            emissions from this category! The safety concerns associated with venting, and  the
                            value of re-injecting gas into oil reservoirs to maintain reservoir pressures, would
                            tend to  question the high  emissions estimates. Improved data are needed to  resolve
                            this question.
                        The adoption of emissions factor estimates from EPA (1992) for various regions also adds
                        uncertainty to the overall estimates. U.S. oil and gas production facilities and refineries are
                        subject to emission control requirements. The U.S. emissions factors, particularly for
                        refining, may  under-estimate emissions in other regions. Nevertheless, this may not be a
                        significant uncertainty since, if the emissions factors for oil production and oil refining
                        were increased by a factor of 10 for the entire world, the estimate of total global
                        emissions would only increase by about I to 6 Tg for 1988.
 I.I 16

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                                        EMISSIONS FROM ENERGY
TABLE 1-42
U.S AND CANADA - EMISSIONS FACTORS
Emissions Type
Oil and Gas Production
Oil
Gas
Oil & Gas
Crude Oil Transportation and Refining
Transportation
Refining
Storage Tanks
Natural Gas Processing, Transport, and
Distribution
Gas Processing
Gas Pipelines
Gas Distribution
Emissions Factor
kg/PetajouIe
290 - 4,670 of Oil Production
39,590 - 104,220 of Gas Production
2,870 - 1 3,920 of Oil & Gas Prod.
745 of Oil Tankered
90 - 1 ,400 of Oil Refined
20 -260 of Oil Refined
59,660 - 1 16,610 of Gas Consumption
Source
EPA (1992)
EPA (1992)
EPA (1992)
API (1987)
EPA (1992)
EPA (1992)
EPA (1992)
TABLE 1-43
EASTERN EUROPE AND FORMER USSR - EMISSIONS FACTORS
Emissions Type
Oil and Gas Production
Oil
Gas
Oil & Gas
Crude Oil Transportation and Refining
Transportation
Refining
Storage Tanks
Natural Gas Processing, Transport, and
Distribution
Gas Processing
Gas Pipelines
Gas Distribution
Emissions Factor
kg/Petajoule
290 - 4,670 of Oil Produced
218,000 - 567,600 of Gas Produced
6,300 - 29,700 of Gas Produced
745 of Oil Tankered
90- 1,400 of Oil Refined
20 -260 of Oil Refined
340,000 - 715,800 of Gas Consumption
Source
EPA (1992)
Rabchukeial. (I9?l)
Barns etal. (19901
API (1987)
EPA (1992)
EPA (1992)
Rabchuk etal. (1991)
PART 2
                                                          I.I 17

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EMISSIONS  FROM  ENERGY
                                                               TABLE 1-44
                                                  WESTERN EUROPE - EMISSIONS FACTORS
                 Emissions Type
       Emissions Factor
          kg/Petajoule
                                                                                                       Source
                 Oil and Gas Production
                         Oil
                         Gas

                         Oil & Gas
    290 - 4,670 of Oil Produced
  14,800 - 27,000 of Gas Produced
   13,000-16,000 of Gas Produced
   3,000-8,000 of Gas Produced
     EPA (1992)
  Schneider-Fresenius
     etaUI989)
Norwegian SPCA( 1992)
  OLF in prep. (1993)
                 Crude Oil Transportation and Refining
                         Transportation

                         Refining
                         Storage Tanks
       745ofOilTankered
      2,500 of Oil Tankered
     90- 1,400 of Oil Refined
      20 - 260 of Oil Refined
     API (1987)
Norwegian SPCA( 1992)
     EPA (1992)
     EPA (1992)
                 Natural Gas Processing, Transport, and
                 Distribution
                         Gas Processing
                         Gas Pipelines
                         Gas Distribution
58,000 - 111,000 of Gas Consumption
      1,800 of Gas Processed
  Schneider-Fresenius
     etal. (1989)
Norwegian SPCA (1992)
TABLE 1-45
OTHER OIL EXPORTING COUNTRIES - EMISSIONS FACTORS
Emissions Type
Oil and Gas Production
Oil
Gas
Oil & Gas
Crude Oil Transportation and Refining
Transportation
Refining
Storage Tanks
Natural Gas Processing, Transport, and
Distribution
Gas Processing
Gas Pipelines
Gas Distribution
Emissions Factor
kg/Petajoule
290 - 4,670 of Oil Produced
39,590 - 96,000 of Gas Produced
739,470 - 1,019,220 of Gas Produced
745 of Oil Tankered
90- 1,400 of Oil Refined
20 -260 of Oil Refined
1 16,610 - 340,000 of Gas Consumption
Source
EPA (1992)
EPA (1992) and Barns
etal. (1990)
Barns etal. (1990)
API (1978)
EPA (1992)
EPA (1992)
EPA (1992 and
Rabchuk etal. (1991)
 1.1 18

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                                                                                 EMISSIONS  FROM ENERGY
                                                     TABLE 1-46
                                       REST OF THE WORLD - EMISSIONS FACTORS
         Emissions Type
         Oil and Gas Production
                 Oil
                 Gas


                 Oil & Gas
         Crude Oil Transportation and Refining
                 Transportation
                 Refining
                 Storage Tanks
         Natural Gas Processing, Transport, and
         Distribution
                 Gas Processing
                 Gas Pipelines
                 Gas Distribution
       Emissions Factor
         kg/Petajoule
    290 - 4,670 of Oil Produced
  39,590 - 96,000 of Gas Produced
 170,000 - 209,000 of Gas Produced
      745 of Oil Tankered
     90- 1,400 of Oil Refined
      20-260 of Oil Refined
116,610-340,00 of Gas Consumption
                                                                                            Source
      EPA (1992)
EPA (1992) and Barns etal.
        (1990)
   Barns etal. (1990)
      API (1987)
      EPA (1992)
      EPA (1992)
     EPA (1992 and
  Rabchuketal. (1991)
                 Recent Revisions to Emission Factors

                 The above methodology and emission factors are based on the report of an expert group
                 convened to advise the IPCC/OECD programme on methods and data in this specific area
                 (Ebert, et al.,  1993). Since that group delivered its report in mid 1993, a more recent
                 analysis (U.S.  EPA, in press) has provided a somewhat different interpretation of some
                 emission factors. While this very detailed analysis endorses the basic tiered methodology
                 included in this manual, its evaluation of emission factors differs somewhat. This evaluation
                 was based on essentially the same set of measurement data cited herein, but draws
                 somewhat different results from the limited available data. The results of the recent EPA
                 analysis are summarized in Table I -47. The most significant differences are in natural gas
                 processing,  transportation and distribution, where a somewhat more detailed set of
                 emission factor ranges are recommended for non-OECD countries. These factors include
                 some which are based on production  of natural gas and some which are based on
                 consumption  of natural gas (which is the case for all of the factors provided above).
                 Where emission factors are provided for more than one sub-category, they are intended
                 to be additive, and would result in somewhat higher total emissions estimates. Other
                 differences in this U.S. EPA analysis are that venting and flaring emissions for Western
                 Europe are based on oil rather than gas production, and there are minor revisions to
                 some factors  for fugitive and other emissions from gas production.

                 These differences are significant, even given the overall uncertainty in this category, and
                 should be considered carefully by national experts in regions  where emissions from this
                 source category are significant. It is hoped that the differences can be resolved of
                 explained in more detail in the final version of these Guidelines.
PART 2
                                                                    I.I 19

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EMISSIONS  FROM  ENERGY
                       1.9.5  Fugitive  Emissions  Of  Other GHGs

                       Methane is by far the most important greenhouse gas emitted on a "fugitive" basis from oil
                       and gas systems. However, other GHG's are clearly emitted from this source category and
                       should be included in a comprehensive national inventory. There is one type of
                       combustion - flaring of natural gas during production, which is consider a "fugitive"
                       emission.36 From this combustion, CO2 and NOX are certainly produced and other
                       combustion related gases - N2O, CO, and NMVOC may be emitted at least in small
                       quantities.
                       However, after methane, the most significant fugitive emissions from oil and gas
                       production, processing transport and distribution are of non-methane volatile organic
                       compounds (NMVOC). Oil and gas are largely composed of organic compounds, and
                       releases through evaporation or leakages are likely at all stages wherever the fuels or their
                       products contact the atmosphere. Fugitive emissions from  refining, transport and
                       distribution of oil products is a major component of national NMVOC emissions in many
                       countries.
                       The IPCC/OECD programme has not yet addressed the indirect GHG's (including
                       NMVOC) in detail. This is consistent with the initial priorities within the programme - .
                       which focused on the direct greenhouse gases, CO2, CH4, and N2O. However, because
                       these gases are important contributors to a range of local and regional (as well as global)
                       atmospheric pollution problems, they have been widely studied and repotted elsewhere.
                       National experts interested including the other fugitive emissions of GHG's from oil and
                       natural gas systems should consult the existing literature which provides detailed emissions
                       factors and procedures for calculating emisions. Some key examples are:
                       •   The CORINAIR Inventory:  Default Emission Factors Handbook (Bouscaren, 1992);
                       •   Proceedings of the TNO/EURASAP Workshop (TNO Inst of Environmental
                           Sciences, 1993)
                       •   Emissions' Inventory Guidebook (European Environment Agency, forthcoming)
                       •   EMEP and CORINAIR Emission Factors and Species Profiles for Organic Compounds.
                           (Veldt, 1991);
                       •   U.S. EPA's Compilation of Air Pollutant Emissions Factors (AP-42), 4th Edition 1985,
                           (U.S. EPA, 1985), and Supplement F, (U.S. EPA, 1993);
                       •   Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory
                           (Stockton and Stelling, 1987)
                          36This is because the combustion is  not for energy purposes and  takes  place
                       before gas produced is included in national energy accounts.
 1.120

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                                        EMISSIONS FROM ENERGY
TABLE 1-47
REVISED REGIONAL EMISSION FACTORS FOR METHANE FROM OIL AND GAS SYSTEMS (Kc/Pj)
Source Type
Basis
Western Europe
US & Canada
Former USSR,
Central & Eastern
Europe
Other Oil Exporting
Countries
Rest of the World
OIL & GAS PRODUCTION
Fugitive and Other
Routine Maintenance
•missions from Oil
Production
:ugitive and Other
Routine Maintenance
•missions from Gas
'reduction
Venting & Flaring from
Oil and Gas Production
Oil Produced
Gas Produced
Oil & Gas Produced1
Oil Produced
Gas Produced
300 - 5,000
15,000-27,000

1,000-3,000
-
300 - 5,000
46,000 - 84,000
3,000- 14,000
-
-
300 - 5,000
140,000-314.000

-
6,000 - 30,000
300 - 5,000
46,000 - 96,000

-
758,000- 1.046,000
300 - 5,000
46,000 - 96,000

1
175,000-209,000
CRUDE OIL TRANSPORTATION, STORAGE AND REFINING
Transportation
Refining
Storage Tanks
Oil Tankered
Oil Refined
Oil Refined
745
90-1,400
20 - 250
745
90-1,400
20 - 250
745
90- 1,400
20 - 250
745
90- 1,400
20 - 250
745
90- 1,400
20 - 250
NATURAL GAS PROCESSING, TRANSPORT AND DISTRIBUTION
Emissions from
'recessing, Distribution
and Transmission
Leekage at industrial
slants and power
stations
Leekage in the
residential and
commercial sectors
Gas Produced
Gas Consumed
Non-Residential Gas
Consumed
Residential Gas
Consumed
~
72,000- 133,000
-
-
~
57,000- 118,000
-
-
288,000 - 628,000
-
175,000 - 384,000
87,000- 192,000
288,000 (high)2
II 8,000 (low)3
0- 175,000
0 - 87,000
288,000 (high)2
II 8,000 (low)3
0-175,000
0 - 87,000
1. In the US and Canada, the emissions are based on total production of both oil and gas produced.
2. The emissions factor of 288,000 kg/Pj of gas produced is used only for the high emissions estimate.
3. The emissions factor of 1 1 8,000 kg/Pj of gas consumed is used only for the low emissions estimate.
4. Gas consumption by utilities and industries.
5. Gas consumption by the residential and commercial sectors.
PART 2
1.121

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EMISSIONS FROM  ENERGY
                       1.9.6  References

                       Introduction
                       IAEA. 1993. Assessment of Data Bases on Energy Demand and Supply in Terms of their
                       Adequacy for Use in Studies of Greenhouse Gas Emissions: Report of Advisory Group
                       Meeting, IAEA, Vienna, 5-7 April, 1993. International Atomic Energy Agency, Vienna.

                       OECD/IEA. 1993a. Energy Statistics and Balances for Non-OECD Countries: 1990-1991
                       International Energy Agency, OECD, Paris.
                       OECD/IEA. I993b. Energy Balances of OECD Countries, 1990-1991. International  Energy
                       Agency, OECD, Paris.
                       OECD/IEA. I993c. Energy Statistics for OECD Countries, 1990-1991. International Energy
                       Agency, OECD, Paris.
                       OECD/IEA. 1991. Greenhouse Gas Emissions: The Energy Dimension. OECD, Paris.
                       UN (United Nations). 1993. 1991 Energy Statistics Yearbook. United Nations, New York.

                       Carbon Dioxide Emissions From Fossil Fuels
                       Grubb, M.J. 1989. On Coefficients for Determining Greenhouse Gas Emissions From Fossil Fuel
                       Production and Consumption. Energy and Environmental Programme, Royal Institute of
                       International Affairs, London, UK. April.  Prepared for IEA/OECD Expert Seminar on
                       Energy Technologies for Reducing Emissions of Greenhouse Gases, Paris.
                       IPCC. 1992. Climate Change 1992: The Supplementary Report to the IPCC Scientific Assessment.
                       The Intergovernmental Panel on Climate Change (World Meteorological
                       Organization/United Nations Environment Programme). Cambridge University Press.

                       IPCC/OECD. 1993. IPCCIOECD Workshop on National GHG Inventories: Transparency in
                       Estimation and Reporting, I October, 1992, Bracknell, U.K. IPCC/OECD Joint Programme on
                       National GHG Inventories, Intergovernmental Panel on Climate Change and Organization
                       for Economic Cooperation and Development, Paris, April.
                       Jaques, A.P. 1992. Canada's Greenhouse Gas Emissions for 1990. Report EP5/AP/4.
                       Environment Canada.
                       Marland, G.,and R.M.  Rotty. 1984. Carbon Dioxide Emissions from  Fossil Fuels: A
                       Procedure for Estimation and Results for 1950-1982. TeHus 36b:232-26l.

                       Marland, G. and A. Pippin. 1990. "United States Emissions of Carbon Dioxide to the
                       Earth's Atmosphere by Economic Activity," Energy Systems and Policy, Volume 14, pp. 319-
                       336.
                       OECD/IEA (Organisation for Economic  Cooperation and Development/International
                       Energy Agency). 1989. Energy Statistics, 1986-1987.  International Energy Agency, OECD,
                       Paris.
                       OECD/IEA. I990a. WorW Energy Statistics and Balances: 1985-1988. International Energy
                       Agency, OECD, Paris.
                        OECD/IEA. I990b. Energy Botonces of OECD Countries, 1987-1988. International Energy
                       Agency, OECD, Paris.
                        OECD/IEA. 1991. Greenhouse Cos Emissions: The Energy Dimension. OECD, Paris.
  1.122

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                                                                               EMISSIONS  FROM  ENERGY
                 Okken, P.A., and T. Kram. 1990. Calculation of Actual C02 Emissions from Fossil Fuels.
                 Presented at ETSAP-IV workshop Petten, the Netherlands, 9-12 April 1990 and IPCC
                 Preparatory Workshop, Paris, 22-23 May 1990.

                 Summers, G. 1993. Personal communication on behalf of the Coal Industry Advisory
                 Board, Global Climate Committee. 22nd July.

                 UN (United Nations). 1993. 1991 Energy Statistics Yearbook. United Nations, New York.

                 USDOE/EIA. 1992. Analysis of the Relationship Between the Heat and Carbon Content of U.S.
                 Coals. Energy Information Administration, U.S. Department of Energy, September.

                 Other GHG Emission From Stationary Combustion

                 Bakkum, A., and C. Veldt. 1986. PHOXA: Statistical Data and Emission Factors. MT-TNO,
                 Department of Environmental Technology, Apeldoorn, Netherlands.

                 Bakkum, A., H. Bartelds, J.A. Duiser, and C. Veldt. 1987. Handbook of Emission Factors:
                 Pan 3 - Emissions from Stationary Sources. Ministry of Housing, Physical Planning, and
                 Environment (VROM), Government Publishing Office. The Hague, The Netherlands,
                 November.
                 Berdowski, J., J. Olivier, and C. Veldt. 1993. Methane From Fuel Combustion and Industrial
                 Processes, in A.R. van Amstel, (ed.), Proceedings of an International IPCC Workshop on
                 Methane and Nitrous Oxide: Methods in National Emissions Inventories and Options for
                 Control. RIVM Report no. 481507003,  Bilthoven, The Netherlands.

                 Brieda, F., and K.-O.Pakleppa. 1989. Development of a Model for the Compiling of National
                 Totals Emission Inventories for the European OECD Member Countries. Unweltforschungs Plan
                 Des Bundesminister fur Unwelt, Naturschutz, und Reaktorsichereit November.

                 Bouscaren, R. (1992). CORINAIR Inventory: Default Emission Factor Handbook, 2nd Ed.
                 12:1 -3. Published by CITEPA, Paris,  France.
                 De Soete, G.G. 1993. Nitrous Oxide from Combustion and Industry: Chemistry, Emissions and
                 Control, in A.R. van Amstel, (ed.), Proceedings of an International IPCC Workshop on
                 Methane and Nitrous Oxide: Methods in National Emissions Inventories and Options for
                 Control. RIVM Report no. 481507003,  Bilthoven, The Netherlands.
                 Eggleston, H.S., and G. Mclnnes. 1987. Method for the Compilation of UK Air Pollutant Emission
                 Inventories. ISBN-0-85624-493-7. Warren Spring Laboratory, Stevenage, UK.
                 European Environment Agency. Forthcoming. Emissions Inventory Guidebook for the
                 UNECE and CORINAIR Emissions Inventories.
                 Fritsche, U. 1989. Zusammenstellung von klimarelevanten Emissionsdaten  fuer Energiesysteme in
                 der BRD, Endbericht.
                 Fritsche, U., L. Rausch, and K.H. Simon. 1989. Umweltwirkungsanalvse von Energiesystemen:
                 Gesamt-Emissions-Modell Integrierter Systeme (GEMIS) Endbericht. OEKO-lnstitut,
                 Darmstadt/Kassel, Germany. August.
                 Garret, C. 1990. Personal communication. Office of Research and Development, U.S. EPA,
                 Research Triangle Park,  North Carolina. December 7.

                 Hao, W.M., S.C. Wofsy, M.B. McElroy, J.M. Beer, and M.A. Toqan. 1987. Sources of
                 atmospheric nitrous oxide from combustion. Journal of Geophysical Research 92:3098-3104.
PART 2
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EMISSIONS FROM  ENERGY
                       IPCC/OECD Programme on National GHG Inventories. 1991. Proceedings of a Workshop
                       on National GHG Emission Methods, Geneva, 3-7 December, 1991. Intergovernmental Panel
                       on Climate Change, Working Group I, Bracknell, U.K. and Organization for Economic
                       Cooperation and Development, Environment Directorate, Paris.
                       JAERI (Japanese Atomic Energy Research Institute). 1988. Data provided through personal
                       communicaton with Mr. Doug Hill, Operating Agent for the IEA Energy Technology
                       Systems Analysis Project (ETSAP), Annex III.
                       Linak, W.P., J.A. McSorley, R.E. Hall, J.V. Ryan, R.K. Srivastava, J.O.L Wendt, and j.B.
                       Mereb. 1990. Nitrous oxide emissions from fossil fuel combustion. Journal of Geophysical
                       Research 95:7533-7541.
                       Montgomery, T.A., G.S. Samuelsen, and L.J. Muzio. 1989. Continuous infrared analysis of
                       N2O in combustion products. Journal of the American Chemical Society 39:721-726.

                       Muzio, L.J., and J.C. Kramlich.  1988. An artifact in the measurement of N2O from
                       combustion sources. Geophysical Research Letters 15:1369-1372.

                       Muzio, L.J., M.E.Teague,J.C. Kramlich, J.A. Cole.J.M. McCarthy, and R.K.Lyon.  1989.
                       Errors in grab sample measurements of N2O from combustion sources. Journal of the
                       American Chemical Society 39:287-293.
                       OECD/IEA (Organisation for Economic Cooperation and Development/International
                        Energy Agency). 1989. Energy Statistics,  1986-1987. International Energy Agency, OECD,
                        Paris.
                        OECD/IEA. 1990a. Wor/d Energy Statistics and Balances: 1985-1988 (OECD/IEA, I990b).
                        International Energy Agency, OECD, Paris.
                        OECD/IEA. I990b. Energy Balances of OECD Countries, 1987-1988. International Energy
                        Agency, OECD, Paris.
                        OECD/IEA. 1991. Greenhouse Gas Emissions: The Energy Dimension. OECD/IEA, Paris.
                        OFPE (L'Office Federal de la Protection de PEnvironnement).  1988. Emissions Poffuontes en
                        Su/sse Dues a I'Activite Hunaime (de 1950 a 2010, et Complement). Les Cahiers de
                        I'Environnement, No. 76, Berne, Switzerland, decembre 1987 et septembre 1988.
                        Okken, P.A. 1989. Impact of NOX and  CO2 constraints on the Netherlands energy system.
                        in  Proceedings of the 8th World Clean Air Congress, The Hague, September.

                        Olivier, J.G.J. 1993. Working Group Report: Nitrous Oxide Emissions from Fuel Combustion and
                        Industrial Processes, in A.R. van Amstel,  (ed.), Proceedings of an International IPCC
                        Workshop on Methane and Nitrous Oxide: Methods in National Emissions Inventories
                        and Options for Control. RIVM Report no. 481507003, Bilthoven, The Netherlands.

                        Radian Corporation. 1990. Emissions and Cost Estimates for Globally Significant Anthropogenic
                        Combustion Sources ofNOv N20, CH<, CO, and C02. Prepared for the Office of Research and
                        Development, U.S. Environmental Protection Agency, Washington, D.C.

                        Rentz, O., H.D, Haasis, T. Morgensterm, F. Pewrello-Aracena, J. Remmers, and G. Schons.
                         1988. Optimal Control Strategies for Reducing Emissions from Energy Conversion and Energy Use.
                        Institute for Industrial Production, Karlsruhe, FRG, March.

                        Statens forurensningstilsyn. 1990. Klimagass Regnskap for Norge. Oslo, Norway.

                        Stockton M.B. and J. Stelling.  1987. Criteria Pollutant Emission Factors for the 1985 NAPAP
                        Emissions Inventory. EPA-600/7-87-015. Office of Research and Development, U.S. EPA.
                        May.
  1.124

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                                                                                EMISSIONS FROM ENERGY
                 TNO (1993). Proceedings of the TNO/EUROSAP Workshop, Delft, June 1993. TNO,
                 Institute of Environmental Sciences, Petten, NL.

                 UN (United Nations). 1990. 1988 Energy Statistics Yearbook. United Nations, New York.

                 U.S. EPA (1985). Compilation of air pollutant emission factors, Vol. I, Stationary point and area
                 sources, AP-42, 4th Edit/on 1985; Suppl. A/1986, Suppl. B/1988, Suppl. C/1990. U.S.
                 Environmental Protection Agency.

                 U.S. EPA (1993). Compilation of air pollutant emission factors, Vol. I, Stationary point and area
                 sources, AP-42, Supplement F. U.S. Environmental Protection Agency.

                 Veldt, C. (1991). Development ofEMEP and COKINAIR emission factors and species profiles for
                 emissions of organic compounds. 1MET-TNO report 91 -299.

                 Walbeck, M, H.J. Wagner, D. Martinsen, and V. Bundschuh. 1988. Energie und Umwelt als
                 Optimierungsaufgabe:  Das MARNES-Modell/ Springer-Verlag, Berlin.

                 Zeedijk,  H. (1986). Emissions by combustion of solid fuels in domestic stoves. Proc. 7th World
                 Clean Air Congress, Sydney (Aus), H.F. Hartmann (ed.)., Vol.  IV, 78-85.

                 Burning Of Traditional Biomass Fuels

                 Barnard, G.W. 1990. Use of agricultural residues as fuel. In: PasztorJ., and L.A.
                 Kristoferson (eds.). Bioenergy and the Environment. Westview Press, Boulder, Colorado, pp.
                 85-112.

                 Crutzen, P.J., M.O. Andreae. 1990. Biomass burning in the Tropics: Impact on atmospheric
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                 Delmas,  R. I993a. An Overview of Present Knowledge on Methane Emission from
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PART 2
                                                                                                                  1.125

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EMISSIONS FROM ENERGY
                       GHG Emissions From Mobile Combustion
                       Alexandersson, A. (1990). The Swedish investigation - Exhaust emissions from ships. Proc
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                       Baas.j. (1991). Study of literature on emission of nitrous oxide by road traffic (in Dutch
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                       Berdowski, J., J.  Olivier, and C. Veldt. 1993. Methane From Fuel Combustion and Industrial
                       Processes, in A.R. van Amstel, (ed.), Proceedings of an International IPCC Workshop on
                       Methane and Nitrous Oxide: Methods in National Emissions Inventories and Options for
                       Control. RIVM Report no. 481507003, Bilthoven, The Netherlands.

                       Berdowski, J., L Beck, S. Piccot, J. Olivier and C. Veldt (1993). Working Group Report:
                       Methane Emissions from Fuel Combustion and Industrial Sources, in A.R. van Amstel, (ed.),
                       Proceedings of an International IPCC Workshop on Methane and Nitrous  Oxide: Methods
                       in National Emissions Inventories and Options for Control. RIVM Report no. 481507003,
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                       Bremmes, P.K.  1990.  Calculations of exhaust gas emissions from sea transport:
                       Methodology and results. Proc EMEP Workshop on Emissions from Ships. Oslo, Norway, June
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                       Dasch, J.M. 1990. Nitrous oxide emissions from vehicles. General Motors  Research
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                       De Soete, G.G. 1993. Nitrous Oxide from Combustion and Industry: Chemistry, Emissions  and
                       Control, in A.R. van Amstel, (ed.), Proceedings of an International IPCC Workshop on
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                       Control. RIVM  Report no. 481507003, Bilthoven, The Netherlands.
                       Dietzmann, H.E., MA. Parness, and R.L. Bradow. 1980. Emissions from Trucks by Chassis
                       Version of 1983  Transient Procedure. SAE Paper No. 801371.  SAE International, Warrendale,
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                       Eggleston, H.S.  et al., (1992). CORINAIR Working Group om Emission Factors for
                       Calculating 1990 Emissions from Road  Traffic, Volume I: Methodology, Final Report,
                       December.
                       Ford Motor Company. 1989. Annual report to EPA on non-regulated pollutants for
                       calendar year 1988. Dearborn, Ml.
                       Ford Motor Company. 1990. Annual report to EPA on non-regulated pollutants for
                       calendar year 1989. Dearborn, Ml.
                        Ford Motor Company. 1991. Annual report to EPA on non-regulated pollutants for
                        calendar year 1990. Dearborn, Ml.
                        Hadler, C. 1990. Investigation of exhaust gas emission from heavy fuel operated diesel
                        engines on board ships. Proc EMEP Workshop on Emissions From Ships. Oslo, Norway, June
                        7-8, 1990. State Pollution Control Authority, Oslo.

                        International Road Federation.  1990. World Road Statistics 1986-1990. Edition 1990,
                        Washington, D.C. and Geneva, Switzerland. September.
  1.126

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                                                                               EMISSIONS FROM  ENERGY
                Iwasaki, Y., S. Tatsuichi, S. Fukuoka, Y. lida, M. Funeshima, H. Yokota and Y. Takenaga
                (1990): Determination of N2O from automobiles. Proc. of the 3 /* Annual meeting of the
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PART 2
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EMISSIONS FROM ENERGY
                       Emissions From Coal Mining, Handling And Utilization

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                       Bibler, C.J., et al. (1992), Assessment of the Potential for Economic Development and
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  1.1 28

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                                                                               EMISSIONS  FROM ENERGY
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                OECD Experts Meeting, Paris, France, 18-21 February 1991.

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                Utilization of Coalbed Methane in Poland. EPA/400/1-91/032, U.S. Environmental
                Protection Agency, Washington, D.C.

                Polish Central  Mining Institute (1990), Official Polish Methane Emissions Data for 1989.
                provided to Raven Ridge Resources, November 1990.

                Seller, W. (1984), "Contribution of Biological Processes to the Global Budget of CH4 in
                the Atmosphere," in Current Perspectives in Microbial Ecology. American  Society for
                Microbiology, Washington, D.C.

                Seltzer, H. and W. Zittel (1990), Emissions of Methane Gas Affecting the Climate: an
                Investigation of Global Methane Emissions from the Use of Fossil Fuels. Waste
                Incineration. Agriculture, and the Earth. LBST-Report No. 10/90, Ottobrunn, Germany.

                Smith, I.M. and L.L Sloss (1992), Methane Emissions from Coal: IEA Perspectives.
                IEAPER/04, London, United Kingdom, November  1992.

                USEPA (I993a), Global Anthropogenic Methane Emissions: Estimates for  1990. Report to
                the U.S. Congress. U.S. Environmental Protection  Agency, Office of Policy, Planning and
                Evaluation, Washington, D.C. (in preparation).
                USEPA (1993b), Anthropogenic Methane Emissions in the United States:  Estimates for
                1990. Report to the U.S. Congress. U.S. Environmental Protection Agency, Office of Air
                and Radiation,  Washington, D.C. (in press)

                USGS (1993), personal communication.

                Williams, A. and C. Mitchell (1992), "Methane Emissions from Coal Mining," Department
                of Fuel and Energy, The University of Leeds, Leeds, United Kingdom (in preparation).

                Zimmermeyer, G. (1989), "Methane Emissions and Hard Coal Mining," Glueckaufhaus,
                Essen, Germany, Gesamtverband des deutschen Steinkohlenbergbaus, personal
                communication.

                Emissions From Oil And Gas Systems

                Abrahamson D. 1989. "Relative Greenhouse Effect of Fossil Fuels and the Critical
                Contribution of Methane,"  presented to The Oil Heat Task Force

                AGA. 1989. "Natural Gas Transmission and Distribution Methane Emissions," AGA,
                Engineering Technical Note, Arlington, VA.

                Alphatania. 1989. Methane Leakage from Natural Gas Operations. The Alphatania Group.

                API (American Petroleum Institute). 1987. "Atmospheric Hydrocarbon Emissions from
                Marine Vessel Transfer Operations,"  API publication 25I4A, Washington, DC.

                Bouscaren, R. (1992). CORINAIR Inventory: Default Emission Factor Handbook, 2nd Ed.
                12:1-3. Published by CITEPA, Paris, France.

                BP Statistical Review of World Energy. 1992. Published by BP. London.
PART 2
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                       Barns, D.W. andJ.A. Edmonds. 1990. "An Evaluation of the Relationship Between the
                       Production and Use of Energy and Atmospheric Methane Emissions," prepared for the
                       Office of Energy Research, U.S. Department of Energy, Washington, D.C.
                       Cicerone, R.J. and R.S. Oremland. 1988. "Biogeochemical Aspects of Atmospheric
                       Methane," Global Biogeochemical Cycles, Vol. 2, No. 4, Dec. 1988, pp. 299 - 327.
                       Craig, Bruce. 1991. Personal communication. U.S. Environmental Protection Agency,
                       Global Change Division, Washington, D.C.
                       Ebert, C, D. Picard, P. Pope, and A. Roslund. 1993. Methane Emissions from Oil and
                       Natural Gas Systems: a Methodology to Estimate national Emissions, in A.R, van Amstel
                       (ed.). Proceedings of an International IPCC Workshop: Methane and Nitrous Oxides, Methods in
                       National Emissions Inventories and Options for Control, 3-5 February 1993, Amersfoort, NL RIVM
                       Report no. 481507003, Bilthoven, NL, July.
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                       UNECE and CORINAIR Emissions Inventories.
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                       prepared for the National Aeronautics and Space Administration, Washington, D.C.,
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                       Methane Loss from Interstate Natural Gas Pipeline," Rate and Policy Analysis Department,
                       Washington, D.C.
                       International Petroleum Encyclopedia. 1990. Vol 23, PennWell Publishing Co., Tulsa,
                       Oklahoma.
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                       Gases in Norway - 1989. National versus IPCC estimation method (Transparency study).
                       Rapport 92:29.
                       Norwegian SPCA (State Pollution Control Authority). 1992. Letter on "Methane Emissions
                       from Oil Activities" from Audun Rosland, SPCA to Craig D. Ebert, ICF Incorporated.
                       Norwegian Oil Industry Association - OLF,  1993  in prep. Report from OLF Environmental
                       Programme - Phase 2. Will be available Mars 1993.
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                       PG&E Research & Development; San Ramon, CA; GRI-90/0067.1.
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                       Intergovernmental Panel on Climate Change Work Group I. May  1992.
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                       Soviet Natural Gas Supply System," prepared for the Battelle Pacific Northwest
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                       and Storage in the U.S. Natural Gas Industry,"  Updated Draft Report prepared for the
                       U.S. EPA and the Gas Research Institute.
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                 Schneider-Fresenius, W. R.A. Hintz, U. Hoffmann-Meienbrock, W. Klopffer, and J.
                 Wittekind. 1989. "Determination of Methane Emission into the Atmosphere due to Losses
                 in the Natural Gas Supply System of the Federal Republic of Germany - Contribution of
                 Methane to the Global Greenhouse Effect." Battelle-lnstitut, Frankfurt, Germany.

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                 Volume (in preparation) SOCAL Research & Development; Los Angeles, CA.

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                 Emissions Inventory. EPA-600/7-87-015. Office of Research and  Development, U.S. EPA.
                 May.

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                 Institute of Environmental Sciences, Petten, NL.

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                 Gas Exploration & Production Activities. Submitted to The Watt Committee on Energy.
                 UN (United Nations).  1992. UN Energy Statistics Yearbook 1990, UN, New York.

                 U.S. EPA (1985).  Compilation of air pollutant emission factors, Vol. I, Stationary point and
                 area sources, AP-42, 4th Edition 1985; Suppl. A/1986, Suppl. B/1988, Suppl. C/1990. U.S.
                 Environmental Protection Agency.

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                 the United States - Report to Congress," prepared by Global Change Division, Office of
                 Air and Radiation, US EPA, Washington, DC.

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                 profiles for emissions of organic compounds. IMET-TNO report 91-299.
PART 2
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                        CHAPTER 2
            INDUSTRIAL PROCESSES
PART 2
2.1

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                       INDUSTRIAL  PROCESSES
    2.1     Overview

             Greenhouse gas emissions are produced from a variety of non-energy related industrial
             activities. The main emission sources are industrial production processes which chemically
             or physically transform materials from one state to another. During these production
             processes, many different greenhouse gases (CO2, CH4, N2O, CO) can be released.
             Cement production is perhaps the most notable example of such an industrial
             (transformation) process that releases a significant amount of CO2.

             In some instances industrial process emissions are produced in combination with energy
             combustion emissions. To the extent that these emissions are the direct result of the fuel
             combustion, they are included as energy emissions not industrial process emissions. This
             will avoid double-counting since these emissions should  be estimated as a result of energy
             consumption activities (see the Energy Chapter). Also, all emissions, including evaporative
             emissions which occur in energy transformation activities (e.g., petroleum refining) are
             discussed in the Energy Chapter. Other evaporative emissions, primarily of NMVOC, are
             not included in the Industrial Processes Chapter. These  sources, also referred to as "area
             sources" are now treated separately in the Solvent Use  Chapter. Refer to Volume I,
             Greenhouse Gas Inventory Reporting Instructions for further discussion of source category
             definitions and reporting issues.
             At this time, cement production is the only process for which a detailed methodology is
             proposed for emissions estimation. However, it has been recommended that all processes
             generating emissions be identified, the level of emissions from these processes evaluated,
             and appropriate emission estimation methodologies developed. Some preliminary
             information is provided for CO2, CH4 and N2O emissions estimation from industrial
             processes. Experts have suggested general additions to the range of source activities to be
             addressed in this Guidelines document. Some of these are listed in Table 2-1 of this
             chapter. This is not intended to be a definitive list, but rather  to be a working list which
             will evolve over time as methods improve.
             2.1.1   Chapter  Organization

             The remainder of the chapter is organized by gases of concern. The next section discusses
             CO2 emissions from industrial processes including cement manufacturing. The next two
             sections summarize available preliminary information on industrial process sources of CH4
             and N2O respectively. The final section discusses sources of other GHGs from industrial
             processes. The IPCC/OECD programme has not yet addressed these gases in detail.
             Instead, this section identifies some of the major information sources already available
             from other international and national emissions inventory programs. The sections in this
             chapter dealing with industrial process emissions give background information on the
             sources and uncertainties  associated with estimating emissions for the most important
             gases and source categories. This is consistent with the initial priorities under the
             IPCC/OECD programme. National experts are encouraged to report any other relevant
             data, along with documentation of methods and assumptions used. This will greatly assist
             in the development of more complete methods for future editions of the IPCC Guidelines.
PART 2
2.3

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INDUSTRY
          2.2     Carbon  Dioxide  Emissions  From  Industrial
                    Processes
                    2.2.1   Cement Manufacturing

                    Carbon dioxide emitted during the cement production process represents the most
                    important non-energy industrial process source of global carbon dioxide emissions.
                    Cement production accounts for about 2.4 percent of total global industrial and energy
                    CO2 emissions (Marland et at., 1989). Carbon dioxide is produced during the production
                    of clinker, an intermediate product from which cement is made. High temperatures in
                    cement kilns chemically change raw materials into cement clinker (grayish-black pellets
                    about the size of ^-inch-diameter marbles). Specifically, calcium carbonate (CaCO3) from
                    limestone, chalk, or other calcium-rich materials is heated, forming lime (calcium oxide or
                    CaO) and carbon dioxide in a process called calcination or calcining:
                                              CaCO3 + Heat -> CaO + CO2
                    This lime combines with silica-containing materials, provided to the kiln as clays or shales,
                    to form dicalcium or tricalcium silicates, two of the four major compounds in cement
                    clinker (Griffin, 1987). The clinker is then removed from the kiln, cooled, and pulverized
                    into an extremely fine gray powder. During this operation a small amount of gypsum is
                    added to regulate the setting time of the cement. The finished product is called "portland"
                    cement.
                    Most of the cement currently produced in the world is portland cement type, which
                    contains 60 to 67 percent lime by weight. Other speciality cements are lower in lime, but
                    are typically used in small quantities. Research is underway on cement formulations that
                    have similar structural properties to portland cement, but require less lime (Tresouthick
                    and Mishulovich, 1990). Carbon dioxide emissions from cement production are essentially
                    directly proportional to lime content, so production of cements lower in lime yield less
                    CO2.
                    Because carbon dioxide is emitted during clinker production (rather than cement
                    production itself), emission estimates should be based on the lime content and production
                    of clinker. Estimating emissions based on the lime content and  production of finished cement
                    ignores the consideration that some domestic cement may be made from imported
                    clinker, or that some finished cement may use additional lime that is not accounted for in
                    the cement calculations. Clinker statistics, however, may not be readily available in some
                    countries. If this is the case, cement statistics can be used. The differences between the
                    lime content and production of clinker and cement, in most countries, are not significant
                    enough to affect the emission estimates.

                    Estimating CO2 Emissions from Cement

                    Estimation of CO2 emissions from cement production is accomplished by applying an
                    emission factor, in tonnes of CO2 released per tonne of clinker produced, to the annual
                    clinker output.1 The emission factor is the product of the fraction of lime used  in the
                    cement clinker and a constant reflecting the mass of CO2 released per unit lime:
                       1 Note that the estimation of CO2 from energy use during cement production is
                    explained in the energy chapter; these emissions should be reported under Energy-fuel
                    combustion activities.
 2.4


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                                                                                                     INDUSTRY
                                = Fraction CaO x (44 g/mole CO2 / 56.08 g/hnole CaO)
                                                    or
                                       EFdinker = Fraction CaO x 0.785
             There are two methods for calculating this emission factor. The first is to assume an
             average CaO fraction in clinker. Since clinker is mixed with gypsum, which contains less
             lime per unit, to make cement, clinker has a higher lime percentage than finished cement.
             The average clinker lime percentage was found to be 64.6%2. This number was multiplied
             by the molecular weight ratio of CO2/CaO (0.785) to achieve a clinker emissions factor of
             0.5071 tonnes  of CO2/tonne of clinker produced.
                                       EFd,-nker = 0.646 * 0.785 = 0.5071
             A second method is to assemble country or regional data on clinker production by type
             and clinker CaO content by type, then calculate a weighted average for cement lime
             content in the country. In most countries, the difference in the results of these two
             methods is likely to be small; any error in the lime content assumption is likely to be
             smaller than the uncertainty in clinker and cement production figures (Griffin, 1987).
             If information on clinker production is not readily available, an emissions factor in tonnes
             of CO2 released per tonne of cement produced can be applied to annual cement
             production instead. This approach has been followed by Marland et al. (1989), who took
             the average CaO content of cement to be 63.5%, yielding an emission factor of 0.4985
             COj/cement (0.136 te CO2 as C/te cement).
                                           EFcement = 0.635* 0.785
                                                  0.4985
             Additional research indicates that "masonry cement", as opposed to "portland cement"
             requires additional lime, over and above the lime used in its clinker. The following formula
             can be used to account for this activity:
                    a x (All Cement Production) x ((I -(I /1 +b) x c) x 0.785 = tonnes CO2 from
                                       CaO added to masonry cement
             where:
                  a = fraction of all cement produced that is masonry cement (e.g. O.I, 0.2)
                  b = fraction of weight added to masonry cement by non-plasticizer additives such as
                               lime, slag, and shale (e.g. .03, .05)
                  c = fraction of weight of non-plasticizer additives that is lime (e.g. 0.6, 0.8)

                  a x (All Cement Production) = Masonry Cement Production
                  ((l-l/l +b) x c) = fraction of lime in masonry cement not attributable to clinker

                  ((I -1 /1 +b) x c) x 0.785 = an emissions factor of CO2 from masonry cement additives
                1 - Gregg Marland, ORNL, Personal communication.
PART 2
2.5

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INDUSTRY
                    Data Sources
                    International cement production data are available from the United Nations (1988) and
                    from the U.S. Bureau of Mines (1988). In some countries, national data may be available
                    from appropriate government ministries. There is substantial overlap between the U.S.
                    Bureau of Mines and the UN data sets, but the former is more complete. Published
                    information is also available from the European Cement Association (CEMBUREAU,
                     1990).

                    Recommended Method
                    The recommended method for estimating CO2 emissions from cement production is to
                    multiply the most reliable figures available for tonnes of clinker produced by an emission
                    factor of 0.5071 CO7/clinker. Alternatively, cement production can be multiplied by an
                    emission factor of 0.4985 COi/cement.
                     2.2.2  Other  Industrial  Processes
                     There are many other processes which may be significant sources of CO2 for some
                     countries. In the national inventories collected by the IPCC/OECD joint programme, CO2
                     emissions from the following processes have been reported:
                     Production:       coke, iron, steel, aluminum, ferro alloys, carbon carbide,
                                      fertilizers, limestone, lime, dolomite, bricks, glass, paper, pulp, and
                                      print.
                     Consumption:     limestone
                     In estimating emissions from these sources, it is expected that most categories will use the
                     following simple method:
                            Physical units of production (e.g. tonnes) x Emission Factor = Emissions
                                 (e.g. tonnes CO7/tonne
                                                         product)
                     As more national data is collected and evaluated in this area, we expect to be able to
                     develop and provide formulae and default emissions for additional categories (IPCC, 1993).

                     Methane Emissions From Industrial Processes

                     Most global methane budget estimates do not included a large and diverse group of minor
                     industrial sources which emit methane into the atmosphere. This source class deals with
                     non-combustion processes in industry, which excludes methane emitted from fuel
                     combustion in the production process. Individually, these sources emit minor quantities of
                     methane, but collectively their contribution to the global budget may be significant.

                     Non-combustion processes include the following:

                     •    primary metals production and associated processes (coke, sinter, pig iron, steel);

                     •    chemical manufacturing processes; production of a variety of chemicals like carbon
                          black, ethylene, dichloro-ethylene, styrene and methanol.

                     Table 2.2 summarizes estimated global methane emissions from some specific non-
                     combustion industrial processes. These processes include: production of iron/steel (coke
                     included); oil refining; production of carbon black, ethylene, dichloroethylene, styrene and
                     methanol.
 2.6

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                                                                                                        INDUSTRY
              Iron & steel production, appearing as the major source in this category, may be further
              subdivided in coke, sinter and pig iron production as sources of process emissions. The
              other processes that have been analyzed for process emissions of methane are of minor
              importance due to low estimated production level and/or emission. (Berdowski et al.,
              I993b)

              Uncertainties

              Further study and clarification of the sources included  in this category and their global
              average emission factors are required in order to arrive at final conclusions with respect
              to the importance of this source category in total global methane emissions. Table 2.3
              presents the estimated global total methane emissions from non-combustion industrial
              processes along with estimated ranges. The estimated  range presented in the table
              illustrates the uncertainty of point estimates. Wide ranges, such as those presented, imply
              the need for further examination of the data used, particularly for iron and steel industries
              and oil refineries.

              Methane from industrial processes is estimated to be only 3% of all fossil fuel related CH4
              emissions, and hence seems negligible on a global scale. However, it is recommended that
              national experts make a critical review of all possible sources in this category because
              their inclusion may be quite relevant in some national inventories.

              N2O Emissions From Industrial Processes

              Non-combustion industry processes resulting in N2O emissions are recognized as
              important anthropogenic contributors to global nitrous oxide emissions. It is estimated
              that this source category represents 10 to 50% of anthropogenic N2O emissions and 3 to
              20% of all global emissions of N2O emissions. (IPCC, 1992)  Three sources of N2O
              emissions have been identified within this category: adipic acid production, nitric acid
              production, and other chemicals production.

              Adipic acid

              Adipic acid is a raw material primarily used for the manufacturing of 6,6 nylon and is
              generally produced from cyclohexane. Cyclohexane is  used to produce so-called "KA",
              which is subsequently oxidized with nitric acid to produce adipic acid. This oxidation step
              unavoidably produces nitrous oxide as a side-product with an associated emission factor
              (for  unabated emissions) of 300 g N2O/kg adipic acid produced. (Thiemens and Trogler,
              1991)

              Figures for global adipic acid production are estimated  to be 1.8 Tg, with associated
              emissions of 0.37 Tg N2O or 0.24 Tg N2O-N. This emissions estimate assumes a total of
              0.55 Tg of N2O initially produced during the adipic acid production process with an
              average abatement of about 32%. (Reimer et al., 1992) The abatement of N2O results
              from the treatment of the off-gases in a reductive furnace. A number of adipic acid
              producers treat the off-gases with the aim of reducing  NOX emissions, but the treatment
              also  coincidentally destroys nitrous oxide. (Reimer et al., 1992, and McCulIoch, 1993).

              Nitric acid

              Nitric acid (HNO3)is a raw material used mainly as a feedstock  in fertilizer production. As
              mentioned above, nitric acid  is also a component in the production process of adipic acid.
              Of the 50 to 65 Tg nitric acid globally produced annually, about 1.6 Tg is used by the adipic
              acid  industry. (Reimer et al.,  1992) Off-gas measurements at. DuPont showed emission
              factors ranging from 2-9 g N2O/kg HNO3 or 7-27 g N2O-N/l
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INDUSTRY
                     Although no abatement techniques are specifically directed at removing nitrous oxide, the
                     emission factors presented include any effect of other abatement systems that may be
                     applied. (McCulioch, 1993)  The generation of N2O in this production process is likely to
                     be accidental, not unavoidable. The representativity of the DuPont nitric acid production
                     process or of the derived emission factor for N2O for the global production of nitric acid
                     is not known. (Olivier, 1993a)

                     Emissions calculation methodology
                     Estimation of N2O emissions from adipic acid and nitric acid production requires four
                     distinct assumptions or type of data: I) production data on adipic acid and nitric acid,
                     respectively; 2) default emission factors (without specific  N2O abatement); 3) applicable
                     abatement factors for N2O; and 4) the part of the activity level for which a specific
                     abatement factor applies.
                     The recommended calculation scheme is described by the following basic formula:
                                               N2O Emissions = 2 (Activity,, x
                      where:
                           Activity
                           EF,
                = production level (tonne of product annually produced)

                = Effective Emission Factor (kg/tonne product)

                = Emission Factor EF, x abatement factor;

     i           = Total Activity of type i
     j           = Part of activities of type  i with a specific applicable abatement factor

     Abatement factor = I - percentage abated / 100
Total emissions for a country  is the sum across activities and sub-activities with distinct
abatement levels. In the absence of information on the abatement factor one may either
chose to disregard it or instead use a range  for this factor. When production figures are
not available, instead production capacity figures of national production facilities can be
used to estimate associated emissions. (Olivier, 1993b) Table 2.4 lists the emission  factors
and level of abatement discussed in the adipic acid and nitric acid sections.
In general, emission abatement also needs to be considered when estimating emissions
from industrial sources. Technical options for reducing the N2O emissions have been
developed. Table 2.5 lists some of these options. Some of the options may not be
technically or economically feasible at the current time, but further research should
improve the possibilities.

Other chemicals production
The industrial production of other chemical compounds has been identified as a source of
nitrous oxide. There has not been enough study to determine whether this represents a
significant global source of N2O. Emissions  reported in the  Netherlands in the chemical
industry showed an emission of about 1.7 Gg N2O in 1990 from the production of
chemicals other than adipic acid or nitric acid. (Project Emission Registration,  1990)

The precise nature and location of the processes that produce these emissions are not
 known. Suggested sources are related to either a process using a N-compound or a
 catalytic reduction step. Although global N2O emissions from this source category will
 probably be small as compared to emissions associated with adipic acid and nitric acid
 production, further investigation  is recommended. It is possible that other industrial
 sources make significant contributions at a  national level. The Netherlands reports about
  2.8


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                                                                                                     INDUSTRY
              25% of the total energy related emissions of national N2O in 1988-1990, or about 6.6 kton
              N2O/yr. (Van den Born et al., 1991) The study suggests thai: any process in which a
              nitrogen compound is used or catalytic reduction is applied can be a source of N2O
              emissions. (Olivier, 1993a)

              Emissions calculation methodo/ogy
              It is recommended that national inventories include the adipic acid and nitric acid
              production processes at this time, adipic acid and nitric acid manufacture should be
              included as source categories in national inventories. Other industrial  processes can be
              included if the national experts have data on relevant processes. It is likely that these
              figures will be highly country specific, since both process conditions and application of
              abatement technology of some kind may be very different for  different countries.
              It is recommended that further research on industrial processes focus on N2O emissions
              in measurements of the off-gases and other emissions. A more comprehensive study of
              industrial processes and N2O emission measurements at production sites may reveal more
              processes in which nitrous oxide is released.  More representative measurements will
              further reduce the uncertainty in the current estimate of global emissions from this source
              category. (Olivier, 1993b)

              Other GHGs From Industrial Processes

              Although the major GHG emissions have been dealt with above, there are other GHG
              emissions from these processes. These may be significant sources for  some countries. The
              following simple method can be used to estimate these GHGs:
              Physical units of production
              (e.g. tonnes)
x  Emission Factor

(e.g. tonnes CO2/

   tonne product)
=  Emissions
              The IPCC/OECD documents do not provide specific examples of emissions factors for
              other GHGs. For information on emissions factors and estimation procedures for GHGs
              which are currently not provided in this chapter, experts should consult extensive existing
              literature developed by other emissions inventory programmes. Some key examples are:

              •    CORINAIR. Default Emissions Handbook (Bouscaren, 1992);

              •    U.S. EPA's Compilation of Air Pollutant Emissions Factors (AP-42) (US EPA,  1985)
                   and Supplement F (AP-42) (US EPA, 1993);

              •    Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory
                   (Stockton and Stelling, 1985).

              •    Proceedings of the TNO/EURASAP Workshop (TNO Inst. of Environmental
                   Sciences, 1993).

              •    Emission Inventory Guidebook (European Environmental Agency, 1994).
              2.2.3  Conclusion

              There is not much information available on national emission factors and levels of
              abatement for emissions of GHG from industrial processes. This chapter describes basic
              methods and global mean values for emission factors for the following GHG sources:
              •   CO2 from cement production;

              •   N2O from adipic acid production;
PART 2
                                                               2.9

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INDUSTRY
                   •    NZO nitric acid production.
                   In addition, the chapter discusses possible sources and basic approaches to estimate CO2,
                   CH,,, and N2O from other industrial processes. National experts are encouraged to report
                   any relevant emissions for which data are available, along with documentation of methods
                   used. This will greatly assist in the development of more complete methods for future
                   editions of IPCC guidelines.
  2.10

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                                                      INDUSTRY
TABLE 2.1
EMISSIONS FROM PRODUCTION PROCESSES
PROCESS

Cement Production
Limestone Production
Agricultural Liming
Aluminum Production
Ferro-alloy Production
Silisium Carbide Production
Coke Production
Nitric Acid Production
Nitrogen Fertilizer Production
Steel Plant (electric, BOF, etc.)
Ammonia Production
Sodium Carbonate
Urea Production
Carbon Black
Titanium Dioxide
Ethylene Production
Propylene Production
1 ,2 Dichlorothane Production
Vinylchloride Production
Polyethylene Low Density
Production
Polyethylene High Density
Production
Polyvinylchloride Production
Polypropylene Production
Styrene Butadiene
ABS Resins
Ethylene Oxide
Formaldehyde Production
Ethylbenzene Production
Styrene Butadiene Latex
Styrene Butadiene Rubber
Phtalic Anhydride Production
Acrylonitrile Production
Chipboard Production
Paper Pulp Production
Bread Production
Wine Production
Beer Production
Spirits Production
Nitrate Production
POLLUTANTS
NOX




X


X
X
X





X























NMVO
C






X



X


X


X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X

CH4






X


X
X




























CO



X

X
X


X





























C02
X
X
X
X
X
X
X


X
X
X



X















X


X
X
X
X
X
N2O







X


X

X


























PART 2
2.1

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INDUSTRY
TABLE 2.2
GLOBAL EMISSION FACTORS AND EMISSIONS OF METHANE FROM INDUSTRIAL MANUFACTURING PROCESSES
EXCLUDING COMBUSTION EMISSIONS MENTIONED IN TABLE 4.
Manufacturing process •*•••-' ..;.
Integrated iron & steel plant
of which: Coke production
Sinter production
Pig iron production
Carbon black
Ethylene
Dichloroethylene
Styrene
Methanol
Production *)
(T?i ;
750
400
650
550
5
40
20
15
15
Emission factor
(g/kg).
<3
0.5
0.5
0.9
II
1
0.4
4
2
Emission
OB)'
<2
0.2
0.3
0.5
0.06
0.04
0.01
0.06
0.03
References
emission factor.
[1-6] ,
[1,5.6]
[3.4,6]
P]
[3], [7]
[3], [7]
[3], [7]
[3], [7]
[3], [7]
Note:
*) Production data are estimated from various data sources (UN a.o.).
Source: Berdowski et at., I993b
[1] Schade, H. (1980)
P] Stallings.R.L(l984)
[3] Shareef, G.S., WA Buder, LA. Bravo and M.B. Stockton (1988)
[4] Stoehr,R^.(l982)
[5] Prefect Emission registration.
[6] Barnard. W.R. (1990)
[7] Stockton. M.B. and J.H.E Stelling (1987)
                                                        TABLE 2.3
                      ESTIMATED GLOBAL METHANE EMISSIONS FROM INDUSTRIAL PROCESSES (Tg CH4 PER YEAR)
                              Source
                              category
Emission
estimate
Estimate
range
                     Industrial processes
                     > Iron & steel
                                                                                         0.4- 4
                     > Chemical manufacturing
                                                                       0.2
                                                                                         O.I - 2
                     1 Miscellaneous
                                                                       0.6
                                                                                          0.6
                            Total
                                                                        3.3
                                                                                          1.6 - 9.5
                     Source: Berdowski et al.,!993a
  2.12


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                                                                                                        INDUSTRY
                                                  TABLE 2.4
             ESTIMATED EMISSION FACTORS AND ABATEMENT FACTORS FOR INDUSTRIAL SOURCES OF t*iO
Activity
Adipic acid production
Nitric acid production
Emission factor
(gN20/kg)
300
NA
Emission factor range
(gN20/kg)
-
2-9
Percentage
abated
32
0
               Global average value for total AA industry; global value for Du Pont: 5.3%; national uncertainty range not available.

       **      (7-27 g N2O-N/HNO3-N)

       **"*     At present no specific N2O abatement techniques are in use.

       Source: (Olivier, I993b) and references therein (Thiemens and Trogler, 1991); (McCulioch, 1993).
                                                  TABLE 2.5
                             OVERVIEW OF TECHNICAL OPTIONS FOR N2<3 REDUCTION
                Source
Global strength
(Tg N20-N/yr)
                                                                               Options
                Industry
           I. adipic acid
                                            0.4-0.6
                          Incineration (technically and economically
                          feasible); research programme

                          On long term:

                          •  alternative production process for
                             adipic acid
                          •  alternatives for applications of 6,6-
                             nylon
           2. nitric acid
                                            0.1-0.3
                          On long term:
                          •  alternative production process for
                             nitric acid
                          •  alternatives for applications of 6-nyIon
                          •  modify/optimize production processes
           Source: (Olivier, I993b)
    2.3     References

              Barnard, W.R. (1990). Emission factors for iron and steel sources - criteria and toxic
              pollutants. EPA-600/2-90-024 (PB 90-242314).

              Berdowski, J., J. Olivier, C. Veldt. (1993)a. Methane from Fuel Combustion and Industrial
              Processes. In A.R. van Amstel (ed.), Proceeding of an International IPCC Workshop on
              Methane and Nitrous Oxide: Methods in National Emissions Inventories and Options for
              Control. RIVM Report no. 481507003, Bilthoven, The Netherlands.

              Berdowski, J.J.M., L Beck, S. Piccot, J.G.J. Olivier, & C. Veldt (1993)b. Working Group
              Report; Methane Emissions from Fuel Combustion and Industrial Processes. In A.R. van
              Amstel (ed.), Proceeding of an International IPCC Workshop on Methane and Nitrous
              Oxide: Methods in National Emissions Inventories and Options for Control. RIVM Report
              no. 481507003, Bilthoven, The Netherlands.
PART 2
                                                                                                                     2.13

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INDUSTRY
                    Bouscaren R. (1992). CORINAIR Inventory, Default Emissions Handbook, 2nd ed., 12: 1-3.
                    Published by CITEPA.
                    CEMBUREAU. 1990. World Cement Market in Figures and World Statistics Review.

                    European Environmental Agency. 1994. Emissions Inventory Guidebook.

                    Griffin, R.C. 1987. CO2 release from cement production, 1950-1985. In Marland, G., T.A.
                    Boden, R.C. Griffin, S.F. Huang, P. Kanciruk, and T.R. Nelson.  Estimates of CO2 Emissions
                    from Fossil Fuel Burning and Cement Manufacturing, Based on the United Nations Energy
                    Statistics and the U.S. Bureau of Mines Cement Manufacturing Data. Report #ORNL/CDIAC-
                    25, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak
                    Ridge, Tennessee. May 1989. 643-680.

                    IPCC, 1992. Climate Change  1992. The Supplementary Report to the IPCC Scientific
                    Assessment Published for The Intergovernmental Panel on Climate Change (IPCC),
                    World Meteorological Organization/United Nations Environment Programme. Cambridge
                    University Press.  Edited by J.T. Houghton, G.J. Jenkins, and j.J. Ephraums.

                    IPCC parts I & II, 1993. National GHG Inventories: Transparency in Estimation and
                    Reporting, p.  11.  Prepared by The Intergovernmental Panel on Climate Change (IPCC) and
                    Organization for  Economic Co-operation and Development, World Meteorological
                    Organization/United Nations  Environment Programme.

                    Marland, G., T.A. Boden,  R.C. Griffin, S.F. Huang, P.  Kanciruk, and T.R. Nelson. 1989.
                    Estimates of C02 Emissions from Fossil Fuel Burning and Cement Manufacturing, Based on the
                    United Nations Energy Statistics and the U.S. Bureau of Mines Cement Manufacturing Data.
                    Report #ORNL/CDIAC-25, Carbon Dioxide  Information Analysis Center, Oak Ridge
                    National Laboratory, Oak Ridge, Tennessee. May.
                    McCulloch, A. [ICI] (1993). Personal communication 21-1-93.

                    Olivier,]. (I993)a. Nitrous Oxide Emissions from Industrial Processes. In A.R. van Amstel
                    (ed.). Proceeding of an International IPCC Workshop on Methane and Nitrous Oxide:
                    Methods in National Emissions Inventories and Options for Control. RIVM Report no.
                    481507003, Bilthoven, The Netherlands.
                    Olivier,]. (I993)b. Working Group Report: Nitrous Oxide Emissions from Fuel
                    Combustion and  Industrial Processes. In A.R. van Amstel (ed.), Proceeding of an
                    International IPCC Workshop on Methane and Nitrous Oxide: Methods in National
                    Emissions Inventories and Options for Control. RIVM Report no. 481507003, Bilthoven,
                    The Netherlands.
                    Project Emission  registration. Ministry of Housing, Physical Planning and the Environment
                    (Mln. VROM), The Hague, The Netherlands.
                    Reimer, R.A., R.A. Parrett and C.S. Slaten (1992). Abatement of N2O emission produced in
                    adipic acid. Proc. of 5th Int. Workshop on Nitrous Oxide emissions, Tsukuba (JP), July I-3,
                     1992.

                    Schade, H. (1980). Die Schadstoffemissionen der Eisen- und Stahlindustrie in den
                    Belastungsgebieten Ruhrgebiet-West und Ruhrgebiet-Ost Schriftenr. d. Landesanstalt fur
                    Immissionsschutz des Landes N.W. 52 55-62.

                    Selzer, H. (1989). Energiebedingte  Methanemissionen. Ludwig-Bolkow-Systemtechnik
                    GmbH, quoting Frische, Emissions-Matrix 1989 (without further reference).

                    Shareef, G.S., W.A. Butler, L.A. Bravo and M.B. Stockton (1988). Air emissions species
                    manual Vol. I, Volatile organic Compounds (VOC) Species profiles. EPA-450/2-88-003a (PB
                    88-215792); Addendum (1989), EPA-450/2-88-003c (PB 90-146416).
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                                                                                                    INDUSTRY
            Stallings, R.L (1984). Metallurgical industries: compilation of emission factors and control
            technologies. EPA-600/2-84-003 (PB 84-141548).
            Stockton M.B., and J.H.E. Stelling. 1987. Criteria Pollutant Emission Factors for the 1985
            NAPAP Emissions Inventory. U.S. EPA Washington, Ouverage, EPA-600/7-87-015 XV-211.

            Stoehr, R.A. (1982). Organic emissions from iron ore sinter-ing plants. EPA-600/2-82-091
            (PB 83-116897).
            Thiemens, M.H. and W.C Trogler (1991). Nylon production: an unknown source of
            atmospheric nitrous oxide. Science 251 932-934.
            TNO Institute of Environmental Sciences. 1993. Proceedings of the TNO/EURASAP
            Workshop on the Reliability of VOC Emission Databases. Edited by H.P. Baars, P.J.H.
            Builtjes, M.P.J. Pulles, C. Veldt. IMW-TNO Publication P 93/040. Delft, The Netherlands.
            Tresouthick, S.W., and A. Mishulovich. 1990. Energy and environment considerations for
            the cement industry. In conference proceedings Energy and Environment in the 21st Century.
            Massachusetts Institute of Technology, Cambridge, Massachusetts. March 26-28, 1990. B-
             IIOtoB-123
            United Nations, 1988. United Nations Statistical Yearbook. United Nations, New York.
            U.S. Bureau of the Mines. 1988. Cement Minerals Yearbook, authored by Wilton Johnson.
            U.S. Bureau of the Mines, U.S. Department of the Interior, Washington, D.C.
            U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards. 1985.
            Compilation of Air Pollutant Emission Factors (Fourth Edition), Volume I: Stationary Point
            and Area Sources. EPA-AP-42 (GPO 055-000-00251-7), Research Triangle Park.
            U.S. Environmental Protection Agency. 1993. Office of Air Quality Planning and Standards.
             1985. Compilation of Air Pollutant Emission Factors, Volume I: Stationary Point and Area
             Sources. EPA-AP-42, Supplement F.
            Van den Born, G.J., A.F. Bouwman, J.G.J. Olivier and R.J. Swart (1991). The emission of
            greenhouse gases in the Netherlands. RIVM, Bilthoven, July 1991. RIVM report 222 901
             003.
PART 2
                                                                                                                2.15

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                        CHAPTER 3
                     SOLVENT USE
PART 2
3.1

-------

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                                                                                                      SOLVENTS
                         SOLVENT USE
       3.1     Overview

                Solvents and related compounds are important for greenhouse gas (GHG) and other
                emission inventories because they are a significant source of emissions of non-methane  '
                volatile organic compounds (NMVOC). No other GHGs are emitted in significant amounts
                from this category, which includes chemical cleaning substances used in dry cleaning,
                printing, metal degreasing, and a variety of industrial applications as well as household use.
                Also included in this category are paints, lacquers, thinners and related materials used in
                coatings in a variety of industrial, commercial and household applications. Table 3.1  lists
                some of the potentially important subcategories  included under this source category.
                All of the substances included here contain significant amounts of NMVOC. Emissions are
                produced through evaporation  of the volatile chemicals when  these products are exposed
                to air. Non-methane volatile organic compounds (NMVOC) are often emitted in significant
                quantities from evaporation during the variety of dispersed activities discussed above.
                These emissions are sometimes referred to as "area" sources  because they occur in large
                numbers of small dispersed applications, rather than from lairge centralized industrial
                processes (or "point sources").
                Solvent use is treated as a separate category in detailed inventory procedures (e.g.,
                CORINAIR) because the nature of this area source requires a somewhat different
                approach to emissions estimation than that used for calculating other emissions categories.
                The draft IPCC Guidelines treats the category separately for this reason.
       3.2    NMVOC  Emissions  from  Solvent  Use

                NMVOC emissions estimates are characterized by high uncertainty. This is especially true
                for the solvent use source category on a global scale. The contribution of this source
                category is believed to be quite significant. A preliminary analysis estimated total global
                NMVOC release from solvent use to be about 11 percent of total NMVOC emissions.
                (Watson, et al., 1991)
                Based on national GHG emissions inventories, NMVOC emissions from solvent use can
                represent a much larger share of the total NMVOC emissions for some countries.
                NMVOC from solvent use represents 31% of the total NMVOC emissions for both Italy
                and Denmark. (ENEA, 1991, Fenger etal., 1990) The Netherlands estimates solvent use
                to account for 25%, and both Finland and the United States estimate emissions to be 24%
                of their total NMVOC emissions, (van den Born et al., 1991, Bostrom et al., 1992, US EPA,
                 1991)  By contrast, emissions from solvent use in Nigeria were only 3% of the total
                NMVOC. (Obioh etal., 1992)
                3.2.1   Estimating  Emissions
                The wide variations in national emissions from solvent use highlight the differences in
                solvent use in countries and some of the difficulties associated with accurately estimating
                emissions from this source category.
PART 2
3.3

-------
SOLVENTS
                       There are two basic approaches to estimation of emissions from Solvent: Use, which
                       depend of the availability of data on the activities producing emissions and the emission
                       factors.
                        I    Production based - In some cases, solvent or coating use is associated with
                            centralized industrial production activities, such as automobile and ship production,
                            textile manufacture, paper coating, chemical products manufacture, etc. In these
                            cases it is generally possible to develop NMVOC emission factors based on unit of
                            product output. These are based on the amount of paint, solvents, or other
                            chemically volatile products consumed per unit of production of the final products.
                            Once reasonable factors are developed it is straightforward to estimate annual
                            emissions based on production  data which is generally available on an annual basis for
                            most countries. Industrial production data is also compiled and published by
                            international organizations (e.g., United Nations, 1992) and these data can be used to
                            supplement locally available data.
                        2   Consumption based - In many applications of paints, solvents and similar products,
                            the end uses are too small-scale, diverse, and dispersed to be tracked directly.
                            Therefore emissions estimates are generally based on total consumption (i.e., sales)
                            of the solvents, paints, etc. used in these applications. The assumption is that once
                            these products are sold to end users, they are applied and  emissions produced
                             relatively rapidly. For most surface coating and general solvent use, this approach is
                             used. Emission factors are developed based on the likely ultimate release of NMVOC
                            to the atmosphere per unit of product consumed. These emission factors can then
                             be applied to sales data for the specific solvent or paint products.
                        The IPCC/OECD joint programme has not produced any original work on estimation of
                        NMVOC from solvent use. This is for two reasons. First,  NMVOC is a greenhouse gas
                        (actually a class of gases) covered under the programme, but it has been assigned a lower
                        priority for national experts just initiating greenhouse gas inventory work. Most methods
                        development work within  the IPCC/OECD programme has focused on providing methods
                        and default information for the first priority gases - CO2,  CH4, and N2O, which are direct
                        greenhouse gases. Second, NMVOC is one of the gases already  under heavy scrutiny in
                        national and international inventory programmes because of its role as a local and regional
                        air pollutant Hence there is a large and growing body of literature containing guidance on
                        estimation procedures and emission factors for NMVOC from solvent use and other
                        source categories. National experts who are already familiar with  these procedures and
                        have emissions data available  or under development, should report these data to the
                        IPCC/OECD programme, as discussed in Volume I: Reporting Instructions. Other experts
                        needing information should consult the existing major references such as:

                        •   CORINAIR Default Emissions Handbook (Bouscaren, 1992);
                        •   U.S. EPA's Compilation  of Air Pollutant Emissions Factors  (AP-42) (US EPA, 1985)
                             and Supplement F (AP-42) (US EPA, 1993);
                        •   Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory
                             (Stockton and Stelling, 1985).
                        •   Proceedings of the TNO/EURASAP Workshop (TNO Inst. of Environmental
                             Sciences, 1993).
                        •   Emission Inventory Guidebook (European Environmental Agency,  1994).
  3.4


-------
                 3.2.2  Uncertainties

                 Because NMVOC emission controls vary widely throughout; the world, it is important for
                 national experts to account for the level of emission control application in their country.
                 Also, there may be significant differences among countries regarding the processes and
                 equipment used. These differences can affect the level of NMVOC emissions. Finally,
                 because estimates based on commodities data provide only an approximation of the
                 activities associated with the manufacture of all products wichin a particular subcategory,
                 there is a degree of uncertainty in the estimates. (Watson, eital.,  1991)
                                                                                                       SOLVENTS
TABLE 3.1
POTENTIALLY IMPORTANT SUBCATEGORIES INCLUDED UNDER SOLVENT USE
Surface coating (e.g., painting) operations
Paper coating operations
Printing and Publishing
General Solvent Use
Production of Automobiles and Trucks
Ship building -
Chemical Products Manufacture and Processing
Applications of paints, lacquer, enamel and primer to cans, wood
products, metal parts, buildings, etc. Use of thinning solvents.
Coating operations, mixing and use of thinning solvents.
Press operations, lithography, use of thinning solvents.
Vapor degreasing;, dry cleaning, textile manufacture, household
solvent use.
Surface coating, deaning/degreasing operations.
Surface coating, deaning/degreasing operations.
Solvents are used in a variety of applications in the manufacturing of
chemicals and chemical products.
        3.3     References

                 Bostrom, S., R. Backman, M. Hupa. 1992. Greenhouse Gas Emissions in Finland 1988 and
                 1990, Energy, Industrial, and Transport Activities. Published by Innsinooritoimisto
                 Prosessikemia.

                 Bouscaren R. 1992. CORINAIR Inventory, Default Emissions Handbook, 2nd ed., 12: 1-3.
                 Published by CITEPA.

                 ENEA.  1991. National Emission Inventories of SOX, NOX, NMVOCs, CO, TSP, NH3, CH4,
                 CO2, N20 in Italy, 1985-1989.

                 European Environmental Agency. 1994. Emissions Inventory Guidebook.

                 Fenger, J., j. Fenhann, N. Kilde. 1990. Danish Budget for Greienhouse Gases. Nordic
                 Council of Ministers, Copenhagen. Nord 1990:97.

                 Obioh, I.B., A.F. Oluwole, F.A. Akeredolu. 1992. The Methodology and Status of
                 Greenhouse Gases (GHG) Inventory In Nigeria: 1988 Inventory Results. Paper presented
                 at the IPCC/OECD Workshop on National Inventories of CiHGs, Hadley Centre,
                 Bracknell, UK.

                 Stockton M.B., and J.H.E. Stelling. 1987. Criteria Pollutant Emission Factors for the 1985
                 NAPAP Emissions Inventory. U.S. EPA Washington, Ouverage, EPA-600/7-87-015 XV-211.

                 TNO Institute of Environmental Sciences. 1993. Proceedings of the TNO/EURASAP
                 Workshop on the Reliability of VOC Emission Databases. Edited by H.P. Baars, P.J.H.
                 Builtjes, M.P.j. Pulles, C. Veldt IMW-TNO Publication P 93/1340. Delft, The Netherlands.

                 United  Nations.  1992. United Nations Statistical Yearbook. United Nations Statistical Office,
                 New York.
PART 2
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SOLVENTS
                       U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards. 1985.
                       Compilation of Air Pollutant Emission Factors (Fourth Edition), Volume I: Stationary Point
                       and Area Sources. EPA-AP-42 (GPO 055-000-00251 -7), Research Triangle Park.
                       U S Environmental Protection Agency, Office of Air Quality Planning and Standards. 1991.
                       National Air Pollutant Emission Estimates 1940-1989. EPA-450/4-91-004, Research
                       Triangle Park.
                       U.S. Environmental Protection Agency. 1993. Office of Air Quality Planning and Standards.
                        1985. Compilation of Air Pollutant Emission Factors, Volume I: Stationary Point and Area
                       Sources. EPA-AP-42, Supplement F.
                       van den Born. G.J., A.F. Bouwman, J.G.J. Olivier, and R.J. Swart. 1991. The Emission of
                       Greeenhouse  Gases in the Netherlands (Report no. 222901003). National Institute of
                       Public Health and Environmental Protection, The Netherland.
                       Watson. J.J., J.A. Probert and S.D. Picot.  1991. Global Inventory of Volatile Organic Compound
                        Emissions from Anthropogenic Sources. Prepared for the Office of Research and
                        Development, USEPA. Washington, D.C.
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                         CHAPTER 4
       EMISSIONS FROM AGRICULTURE
PART 2
4.1

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                                                                                           AGRICULTURE
                      EMISSIONS FROM  AGRICULTURE
    4.1     Overview

             Agricultural activities contribute directly to emissions of greenhouse gases through a
             variety of different processes. This chapter discusses four greenhouse gas-emitting
             activities:

             •    CH4 emissions from animals and animal wastes

                  —   CH4 emissions from enteric fermentation in domestic animals
                      Methane is produced in herbivores as a by-product of enteric fermentation, a
                      digestive process by which carbohydrates are broken down by microorganisms
                      into simple molecules for absorption into the bloodstream. Both ruminant
                      animals (e.g., cattle, sheep) and some non-ruminant animals (e.g., pigs, horses)
                      produce CH4, although ruminants  are the largest source since they are able to
                      digest cellulose due to the presence of specific microorganisms in their digestive
                      tracts. The amount of CH4 that is  released depends on the type, age, and weight
                      of the animal, the quality and quantity of the feed, and the energy expenditure of
                      the animal.
                  —   CH4 emissions from anaerobic decomposition of animal wastes
                      CH4 is produced from the decomposition of manure under anaerobic
                      conditions. These conditions often occur when large numbers of animals are
                      managed in a confined  area (e.g., dairy farms, beef feedlots, and swine and
                      poultry farms), where manure is typically stored in large piles or disposed of in
                      lagoons.
             •       CH4 emissions from rice cultivation
                     Anaerobic decomposition of organic material in flooded rice fields produces
                     methane, which escapes to the atmosphere primarily by transport through the
                     rice plants. The amount emitted is believed to be & function of rice species,
                     number and duration of harvests, soil type and temperature, irrigation practices,
                     and fertilizer use.

             •       CH4, CO, N2O, and NOX emissions from agricultural burning:

                      C/-/4, CO, N2O, and NOX emissions from the prescribed burning of savannas
                      The burning of savannas — areas in tropical and sub-tropical formations with
                      continuous grass coverage — results in the instantaneous emissions of carbon
                      dioxide. But because the vegetation regrows between burning cycles, the
                      carbon dioxide released into the atmosphere is reabsorbed during the next
                      vegetation growth period. CO2 emissions are therefore assumed to be zero.
                      But savanna burning also releases gases other tha.n CO2, including methane,
                      carbon monoxide, nitrous oxide and oxides of nitrogen. Unlike CO2 emissions,
                      these are net emissions.
PART 2
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AGRICULTURE
                                CHj, CO, N20, and NOX emissions from the prescribed burning of agricultural wastes
                                Crop residues burning is not thought to be a net source of carbon dioxide
                                because the carbon released to the atmosphere is  reabsorbed during the next
                                growing season. However crop residue burning is a significant source of
                                emissions of methane, carbon monoxide, nitrous oxide, and nitrogen oxides. It
                                is important to note that some crop residues are removed from the fields and
                                burned as a source of energy, especially in developing countries. Emissions from
                                this type of burning are dealt with in the Energy module of this manual. Crop
                                residue burning must be properly allocated to these two components in order
                                to avoid double counting.
                               N2O emissions from agricultural soils
                               Emissions of N2O from agricultural soils are primarily due to the microbial
                               processes of nitrification and denitrification in the soil. Increases in the amount of
                               N  added to the soil generally result in higher N2O emissions (Bouwman, 1990).
                               Increases in the input of N to the soil may result from (I) atmospheric
                               deposition, (2) commercial fertilizer, (3) animal manures and plant residues, (4)
                               biological N fixation, and (5) soil organic matter mineralization.
  4.4

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4
AGRICULTURE
     4.2     Methane  Emission  From  Domestic
              Livestock  Enteric  Fermentation  And
              Manure  Management
              4.2.1   Overview  Of  Methane  Emissions From
              Livestock

              This section covers methane emissions from enteric fermentation and manure of domestic
              livestock. Cattle are the most important source of methane from enteric fermentation in
              most countries because of their high numbers, large size, arid ruminant digestive system.
              Methane emissions from manure management are usually smaller than enteric
              fermentation emissions, and are principally associated with confined animal management
              facilities where manure is handled as a liquid. This section presents a brief overview of the
              key factors affecting methane emissions from these sources..  The methods for estimating
              these emissions are then presented.

              Enteric Fermentation
              Methane is produced during the normal digestive processes; of animals. The amount of
              methane produced and excreted by an individual animal is dependent primarily on the
              following:
              •   Digestive System
                  The type of digestive system has  a significant influence on the rate of methane
                  emission. Ruminant animals have the highest emissions because a significant amount of
                  methane-producing fermentation occurs within the rumen. The main  ruminant
                  animals are cattle, buffalo, goats, sheep, and camels. Pseudo-ruminant animals (horses,
                  mules, asses) and monogastric animals (swine) have relatively lower methane emissions
                  because much less methane-producing fermentation tikes place in their digestive
                  systems.
              •   Feed Intake
                  Methane is produced by the fermentation of feed within the animal's digestive system.
                  Generally, the higher the feed intake, the higher the methane emission. Feed intake is
                  positively related to animal size, growth rate, and production (e.g., milk production,
                  wool growth, or pregnancy).
              The amount of methane emitted by a population of animals is calculated by multiplying the
              emission rate per animal by the number of animals. To reflect the variation in emission
              rates among animal types, the population of animals is divided into subgroups, and an
              emission rate per animal is estimated for each subgroup. Population subgroups are
              recommended in the method1.                        '          .    • •  .
                 'Countries are encouraged to carry out emissions inventory calculations at a finer level
              of detail if possible.  Many countries have available more detailed information than was
              used in  constructing default values here.  Countries may wish to calculate emissions
              estimates at a finer level of detail by sub-category — further disaggregating recommended
              activity categories and sub-categories — or they may choose to subdivide the categories on
              some other basis which they feel is appropriate to their particular national circumstances.
              Working at  finer  levels  of disaggregation  does not change the  basic nature of the
 PART  2
                   4.5

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AGRICULTURE
                       Manure Management
                       Livestock manure is principally composed of organic material. When this organic material
                       decomposes in an anaerobic environment (i.e., in the absence of oxygen) it produces
                       methane. Methanogenic bacteria produce the methane as part of an interrelated
                       population of microorganisms.
                       The principal factors affecting methane emission from animal manure are the amount of
                       manure produced and the portion of the manure that decomposes anaerobically. The
                       amount of manure that is produced is dependent on the amount produced per animal and
                       the number of animals. The portion of the manure that decomposes anaerobically depends
                       on how the manure is managed. When manure is stored or treated as a liquid (e.g., in
                       lagoons, ponds, tanks, or pits), it tends to decompose anaerobically and produce a
                       significant quantity of methane. When manure is handled as a solid (e.g., in stacks or pits)
                       or when it is deposited on  pastures and  rangelands, it tends to decompose aerobically and
                       little or no methane is produced.
                       To estimate methane emission, the animal population must be divided into subgroups to
                       reflect the varying amounts of manure produced per animal, and the manner in which the
                       manure is handled. Population subgroups are recommended in the method.
                       4.2.2 Inventory  Method
                       Overview
                       The method for estimating methane emission from enteric fermentation and manure
                       management requires three basic steps:
                       Step I: Divide the livestock population into subgroups and characterize each subgroup.

                       Step 2: Estimate emission factors for each subgroup in terms of kilograms of methane per
                       animal per year — separate emission factors are required for enteric fermentation and
                       manure.
                       Step 3: Multiply the subgroup emission factors  by the subgroup populations to estimate
                       subgroup emission, and sum across the subgroups to estimate total emission.

                       These three steps can be performed at varying levels of detail and complexity. This
                       chapter presents the following two approaches:

                       •   Tier I
                            A simplified approach that relies on default emission factors drawn from previous
                            studies. The Tier I approach is likely to be sufficient for most animal types in most
                            countries.

                       •   Tier 2
                            A more complex approach that requires country-specific information on livestock
                            characteristics and manure management practices. The Tier 2 approach is
                        calculations.  Once emissions  have  been calculated  at whatever is determined by the
                        national  experts to  be the most appropriate  level of  detail,  results should also be
                        aggregated up to the minimum  standard level  of information requested  in the  IPCC
                        proposed methodology.  This will allow for comparability of results among all participating
                        countries. The data and assumptions used for finer levels of detail should also be reported
                        to the IPCC to ensure transparency and replicability of methods.  Volume I: Reporting
                        Instructions discusses these issues in more detail.
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                                                                                               AGRICULTURE
                  recommended when the data used to develop the default values do not correspond
                  well with the country's livestock and manure management conditions. Because cattle
                  characteristics vary significantly by country, it is recommended that countries with
                  large cattle populations consider using the Tier 2 approach for estimating methane
                  emissions from cattle and cattle manure. Similarly, because buffalo and swine manure
                  management practices vary significantly by country, it is recommended that countries
                  with large buffalo and swine populations consider using the Tier 2 approach for
                  estimating methane emissions from buffalo and swine manure.

             Some countries for which livestock emissions are particularly important may wish to go
             beyond the Tier 2 method and incorporate additional country-specific information in their
             estimates. Although countries are encouraged to go beyond the Tier 2 approach
             presented below when data are available, these more complex analyses are only briefly
             discussed here. Table 4-1 summarizes the recommended approaches for the livestock
             emissions included in this inventory.

             Tier I Approach
             This Tier I method is simplified so that only readily-available animal population data are
             needed to estimate emissions. Default emission factors are presented for each of the
             recommended population subgroups. Each step is discussed in turn.
              The average annual population of animals is required for each of the livestock categories
              listed in Table 4-1. In some cases the population fluctuates during the year. For example, a
              census done before calving will give a much smaller number than a census done after
              calving. A representative average of the population is therefore needed. In the case of
              poultry and swirie, the number of animals produced each year exceeds the annual average
              population because the animals live for less than 12 month:;. The population data can be
              obtained from the FAO Production Yearbook (FAO, 1990) or similar country-specific
              livestock census reports.
              The dairy cow population is estimated separately from other cattle (see Table 4-2). Dairy
              cows are defined in this method as mature cows that are producing milk in commercial
              quantities for human consumption. This definition corresponds to the dairy cow
              population reported in the FAO Production Yearbook.
              In some countries the dairy cow population is comprised of two well-defined segments:
              high-producing "improved" breeds in commercial operations; and low-producing cows
              managed with traditional methods. These two segments can be combined, or can be
              evaluated separately by defining two dairy cow categories. However, the dairy cow
              category does not include cows kept principally to produce calves or to provide draft
              power. Low productivity multi-purpose cows should be considered as other cattle (non-
              dairy).
              Data on the average milk production of dairy cattle is also required. These data are
              expressed in terms of kilograms of whole fresh milk produced per year per dairy cow, and
              can be obtained from the FAO Production Yearbook or similar country-specific reports. If
              two or more dairy cow categories are defined, the average milk production per cow is
              required for each category.
              Finally, the livestock populations must be described in terms of warm, temperate, or cool
              climates for purposes of estimating emissions from livestock manure. Data on the annual
PART 2
                                                                                                                  4.7

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AGRICULTURE
                       average temperature of the regions where livestock are managed should be used as
                       follows:

                       •   Areas with annual average temperatures less than 15°C are defined as cool.

                       •   Areas with annual average temperatures greater than 15°C and less than 25°C are
                           defined as temperate.

                       •   Areas with annual average temperatures greater than 25°C are defined as warm.

                       For each animal population, the fraction in each climate should be estimated. These data
                       can be developed from country-specific climate maps and livestock census reports. To the
                       extent possible, the temperature data should reflect the locations where the livestock are
                       managed. If necessary, data from nearby cities can be used. Table4-2 summarizes the
                       animal population data that must be collected in Step I.
                       TIER  lYsxEP  2*  --  EMISSION "FACTORS!
                         .;*  -^ ^	    	      i V  '•'^   - r"«r*>    V   -'" ""J>*4»  *"-M* .
                       The purpose of this step is to select emission factors that are most appropriate for the
                       country's livestock characteristics. Default emission factors for enteric fermentation and
                       manure management have been drawn from previous studies, and are organized by region
                       for ease of use. The basis for the emission factors, described more fully under Tier 2,
                       includes the following:

                       •    Enteric Fermentation:
                            -    Feed Intake: Feed intake is estimated based on the energy intake required by the
                                 animal for maintenance (the basic metabolic functions needed to stay alive) and
                                 production (growth, lactation, work, and gestation). The animal characteristics
                                 required to estimate feed intake are taken from regional and country-specific
                                 studies and include: population structure (portion of adults and young); weight;
                                 rate of weight gain; amount of work performed; portion of cows giving birth
                                 each'year; and milk production per cow.
                            -    Conversion of Feed Energy to Methane: The rate at which feed energy is converted
                                 to methane is estimated based on the quality of the feed consumed - low
                                 quality feed has a slightly higher methane conversion rate. Feed quality is
                                 assessed in terms of digestibility on a regional basis.
                       •    Manure Management
                            —    Manure Production: Manure  production is estimated based on feed intake and
                                 digestibility,  both of which are used to develop the enteric fermentation
                                 emission factors.
                            -    Methane Producing Potential: Methane producing potential (referred to as B0) is
                                 the maximum amount of methane that can be  produced from a given quantity of
                                 manure. The methane producing potential varies by animal type and the quality
                                 of the feed consumed. Reported measurements for selected animals are used.
                            -    Methane Conversion Factor (MCF): The MCF defines the portion of the methane
                                 producing potential (B0) that is achieved. The MCF varies with the manner in
                                 which the manure is managed and the climate, and can theoretically range from
                                 0 to 100 percent Manure managed as a liquid  under hot conditions promotes
                                 methane formation and emissions. These manure management conditions have
                                 high MCFs, of 65 to 90 percent. Manure managed as dry material in cold
                                 climates does not readily produce methane, and consequently has an MCF of
                                 about I percent. Laboratory measurements were used to estimate MCFs for
                                 the  major manure management techniques.
 4.8

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                                                                                                AGRICULTURE
                  -    Manure Management Practices: Regional assessments of manure management
                       practices are used estimate the portion of the manure that is handled with each
                       manure management technique.
             The data used to estimate the default emission factors for enteric fermentation and
             manure management are presented in Appendix A and Appendix B respectively.
             Table 4-3 shows the enteric fermentation emission factors for each of the animal types
             except cattle. As shown in the table, emission factors for sheep and swine vary for
             developed and developing countries. The differences in the emission factors are driven by
             differences in feed intake and feed characteristic assumptions (see Appendix A). Although
             point estimates are given for the emission factors, an uncertainty of about +20 percent
             exists due to variations in animal management and feeding. Deviations from the emission
             factors can be larger than 20 percent under specialized feeding or management conditions.

             Table 4-4 presents the enteric fermentation emission factors for cattle. A range of
             emission factors is shown for typical regional conditions. As. shown in the table,  the
             emission factors vary by over a factor of four on a per head basis.
             While the default emission factors shown in Table 4-4 are broadly representative of the
             emission rates within each of the regions described, emission factors vary among countries
             within regions. Also, as with the emission factors shown in Table 4-3, an uncertainty of
             about ±20 percent exists due to variations  in animal management and feeding. Animal size
             and milk production are important determinants of emission rates for dairy cows.
             Relatively smaller dairy cows with low levels of production are found in Asia, Africa, and
             the Indian subcontinent. Relatively larger dairy cows with high levels of production are
             found in North America and Western Europe.
             Animal  size and population structure are important determinants of emission rates for
             non-dairy cattle. Relatively smaller non-dairy cattle are found in Asia, Africa, and the Indian
             subcontinent. Also, many of the non-dairy cattle in these regions are young. Non-dairy
             cattle in North America, Western Europe and Oceania are larger, and young cattle
             constitute a smaller portion of the population2.
             Select emission factors from Tables 4-2 and 4-3 by identifying the region most applicable
             to the country being evaluated. The data collected on the average annual milk production
             by dairy cows should be used to help select a dairy cow emission factor. If necessary,
             interpolate between dairy cow emission factors shown in tine table using the data collected
             on average annual milk production per head.
             Table 4-5 shows the default manure management emission factors for each animal type
             except  cattle, buffalo, and swine. Separate emission factors are shown for developed and
             developing countries, reflecting  the general differences in feed intake and feed
             characteristics of the animals in  the two regions. These emission factors reflect the fact
             that virtually all the manure from these animals is managed in dry manure management
             systems, including pastures  and  ranges, drylots, and daily spreading on fields (Woodbury
             and Hashimoto, 1993).
                 2 One method which has been suggested to account for animal growth (increase in
              weight) over time is to use the mean live weight for a given animal category over the year
              of the inventory.   A weight  correction factor (integrator) equal to the ratio  of the
              averaged annual weight and the projected end weight (which is derived from statistics) is
              multiplied by the number of animals in a category to get the live weight of animals in that
              category.
PART 2
                                                                                                                    4.9

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AGRICULTURE
                       The ranges of values shown in Table 4-5 reflect the range of MCF values of I to 2 percent.
                       The higher value is appropriate for manure managed in warm climates, while the lower
                       value is appropriate for manure managed in cooler and dryer climates. A middle value is
                       assigned to temperate conditions. The uncertainty in the emission factors remains
                       substantial, however, because field measurements are  required to validate the laboratory
                       measurements that form the  basis for the MCFs used  in the analysis. Appendix B
                       summarizes the data used to  estimate the emission factors shown in Table 4-6.
                       The climate data collected in  Step  I is used to select the emission factors from Table 4-6.
                       A weighted average emission factor for each animal type is computed by multiplying the
                       percentages of the animal populations in each climate  region by the emission factor for
                       each climate region. For example, if sheep in a developing country were 25 percent in a
                       temperate region and 75 percent in a warm region, the emission factor for sheep would
                       be estimated at about 0.2 kg/head/yr  as follows:
                                  Emission Factor = (25% x 0.16) + (75% x 0.21) = 0.1975 kg/head/yr.
                        An alternative way of handling these calculations is to sub-divide the category of sheep into
                        two populations: one in warm and one in temperate region. Calculations could then be
                        done separately and summed.
                        Because the manure from cattle, buffalo, and swine is managed in a variety of ways,   •
                        including both dry and liquid systems, the variations in manure management practices
                        among regions and countries must be considered to develop emission factors for these
                        animals. Table 4-6 presents emission factors based on regional manure management
                        practices described in Safley et al. (1992).
                        As shown in the table, the emission factors for dairy cattle range between 81 kg/head/year
                        in warm parts of Western Europe to 0 kg/head/year in cool parts of Latin America. The
                        emission factors for non-dairy cattle range between 38 kg/head/yr in warm parts of
                        Western Europe to I kg/head/year in  cool parts of North America and Latin America. In
                        addition to climate, the range of emission factors is due to the manure management
                        practices used in each region. For example, the emission factors for North American dairy
                        cattle manure and European dairy and non-dairy cattle manure are relatively high because
                        the manure is often managed using liquid systems that promote methane production. The
                        emission factors for North American non-dairy cattle and for all animals in Africa and the
                        Middle  East are relatively low because their manure is generally managed using dry systems
                        that do not promote methane production.
                        To select emission factors from Table 4-6, first identify the appropriate region, such as
                        Latin America. Within that region, identify the animal type of interest. For that animal type
                        three values are given for the three climate regions. Compute a weighted average emission
                        factor for the animal type by multiplying the percentages of the animal population in each
                        climate region by the emission factor for each climate region. Appendix B summarizes the
                        estimates of manure management system usage and MCFs that underlie the emission
                        factors in Table 4-6.
                        As with the other manure management emission factors, there is substantial uncertainty in
                        the estimates shown in Table 4-6 because field measurements are required to validate the
                        laboratory measurements that form the basis for the MCFs used in the analysis, and
                        because there is uncertainty and variability  in the manner  in which manure is managed in
                        each region.
 4.10

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4
AGRICULTURE
              To estimate total emission the selected emission factors are multiplied by the associated
              animal population and summed. The emission estimates should be reported in gigagrams
              (Gg).3 Because the emission factors are reported in kilograms per head per year, the total
              emissions in Gg is estimated as follows for each animal category:
                     emission factor (leg/head) x population (head) / 10* kg/Gg - emissions in Gg.
               As a point of reference, in 1990 total annual global methane emissions from domestic
               livestock enteric fermentation were on the order of .060 to . 100 Gg (Gibbs and Johnson,
               1993). Enteric fermentation emissions from countries with large populations of livestock
               may be on the order of .001 to .005 Gg per year. Countries with smaller populations of
               livestock would likely have emissions of less than .001 Gg per year.

               In  1.990 total annual global methane emissions from manure management was on the order
               of .010 to .018 Gg (Woodbury and Hashimoto, 1993). Manure management emissions
               from countries where manure is managed in liquid-based systems may be on the order of
               .001 to .002 Gg per year. Countries where manure is not managed in liquid-based systems
               would likely have emissions of much less than .001 Gg per year.

               Tier 2 Approach For Enteric Fermentation Emissions
               The Tier  2 approach is recommended for estimating methane emissions from enteric
               fermentation from cattle for those countries with large cattle populations. As contrasted
               with the Tier I method, this approach requires much more detailed information on the
               cattle population. Using this detailed information, more precise estimates of the cattle
               emission factors are developed. When the Tier 2 method is used the default emission
               factors listed in Tier I for cattle are not used.
               This Tier 2  approach is similar to the August 1991 OECD method (OECD, 1991), with
               some modifications:
               •    The Blaxter and Clapperton (1965) equation is replaced with a recommended set of
                    methane conversion rate "rules of thumb."
               •    Feed energy intake requirements for pregnancy have been added.
               •    The energy requirements required for grazing have been reduced based on newly
                    available data from AAC (1990).
               •    The equations used  to relate gross energy intake to net energy used by the animal
                    have been made more general to accommodate a wider variety of feed conditions.
               The three steps outlined  for Tier I are also used here.
               To develop precise estimates of emissions, cattle should be divided into categories of
               relatively homogeneous groups. For each category a representative animal is chosen and
               characterized for purposes of estimating an emission factor. Table 4-7 presents a set of
               recommended representative animal types for cattle. Three main categories, Mature Dairy
                  3  I Tg = I012 grams = I09 kilograms = I06 metric tons.
  PART  2
                                                                                                                4.1  I

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AGRICULTURE
                        Cows, Mature Non-Dairy Cattle, and Young Cattle, are recommended as the minimum set
                        of representative types. The sub-categories listed should be used when data are available.
                        In particular, the sub-population of cows providing milk to calves should be identified
                        among non-dairy cattle because the feed intake necessary to support milk production can
                        be substantial. In some countries the feedlot category is needed so that the implications of
                        the high-grain diets can be incorporated.
                        For each of the representative animal types defined, the following information is required:

                        •   annual average population (number of head);
                        •   average daily feed intake (megajoules (MJ) per day and kg per day of dry matter); and

                        •   methane conversion rate (percentage of feed energy converted to methane).

                        Generally, data on average daily feed intake are not available, particularly for grazing
                        animals. Consequently, the following data should be collected for estimating the feed
                        intake for each representative animal type:

                        •   weight (kg);
                        •   average weight gain per day (kg);4
                        •   feeding situation: confined animals; animals grazing good quality pasture; and animals
                            grazing over very large areas;
                        •   milk production per day (kg/day);5
                        •   average amount of work performed per day (hours/day);

                        •   percent of cows that give birth in a year;6 and

                        •   feed digestibility (%).7
                        These data should be obtained from country-specific cattle evaluations. Some data, such as
                        weight, weight gain, and milk production, may be available from production statistics. Care
                        should be taken to use the live cattle weights, as contrasted with slaughter weights.
                        Appendix B lists the data used to develop the default emission factors presented in Tier I.
                        Individual country data can be compared to the data presented in Appendix A to ensure
                        that the data collected are reasonable.
                        Data on methane  conversion rates are  also not generally available. The following rules  of
                        thumb are recommended for the methane conversion rates:
                        •    Developed Countries. A 6% conversion rate (±0.5%) is recommended for all cattle in
                             developed countries except feedlot cattle consuming diets with a large quantity of
                             grain. For feedlot cattle on high grain diets a  rate of 4% (±0.5%) is recommended. In
                             circumstances where good feed resources are available (i.e., high digestibility and  high
                           * This may be assumed to be zero for mature animals.
                           5  Milk production  is required  for dairy cows and non-dairy cows providing milk to
                         calves.
                           6 This is only relevant for mature female cows.
                           1  Feed digestibility is defined  as the  proportion of  energy in  the feed  that is  not
                         jxcreted in the feces.  Digestibility is commonly expressed as a percentage (%). Common
                         ranges for feed digestibility for cattle are 50% to 60% for crop by-products and rangelands;
                         60% to 70% for good  pastures, good preserved forages,  and  grain-supplemented forage-
                         based diets; and 75% to 85% for grain-based diets fed in feedlots.
 4.12

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                                                                                               AGRICULTURE
                  energy value) the lower bounds of these ranges can be used. When poorer feed
                  resources are available, the higher bounds are more appropriate.

             •    Developing Countries. Several recommendations are made for different animal
                  management situations in developing countries:

                  -   All dairy cows and young cattle are recommended to have a conversion rate of
                      6.0% (±0.5%). These cattle are generally the best-fed cattle in  these regions.
                  -   All non-dairy, non-young stall-fed animals consuming low-quality crop by-
                      products are recommended to have a conversion rate of 7.0% (±0.5%) because
                      feed resources are particularly poor in many cases in these regions.
                  —   Grazing cattle are recommended to have a conversion rate of 6.0% (±0.5%),
                      except for grazing cattle in Africa, which are  recommended to have a rate of
                      7.0% (±0.5%) because of the forage characteristic; found in many portions of
                      tropical Africa.
             These rules of thumb are a rough guide based on the general feed characteristics and
             production practices found in many developed and developing countries. Country-specific
             exceptions to these  general rules of thumb should be taken into consideration as
             necessary based on detailed data from cattle  experts.

             The emission factors for each category of cattle are estimated based on the feed intake
             and methane conversion rate for the category. Feed intake is estimated based on the feed
             energy requirements of the representative animals, subject to feed-intake limitations. The
             net energy system described in NRC (1984 and 1989) is recommended as the starting
             point for the estimates. Because the NRC system was developed for feeding conditions in
             temperate regions, several adjustments were made to avoid potential biases when applied
             to evaluate feed-energy intakes for tropical cattle (see Appendix C). Comparisons with
             alternative feeding systems (e.g., ARC, 1980) indicate that the emissions estimates are not
             sensitive to the feeding system used as the basis for making the estimates.
             The net energy system specifies the amount of feed energy required for the physiological
             functions of cattle, including maintenance, growth, and lactation. Feed energy requirements
             for work have also been estimated, and are included in this analysis for the draft animals in
             developing countries. Energy requirements for pregnancy have also been added for the
             portion of cows that give  birth in each year. The following information is required to
             estimate feed energy intakes:
             •    Maintenance
                  Maintenance refers to the apparent feed energy required to keep the animal in
                  energy equilibrium, i.e., there is no gain or loss of energy in the body tissues (Jurgens,
                  1988).  For cattle, net energy for maintenance (NEm) has been estimated to be a
                  function of the weight of the animal raised to the 0.75 power (NRC, 1984):
PART 2
                                                                                                                 4.13

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AGRICULTURE
                                                        EQUATION I
                                             NEm (Mj/day) = 0.322 x (weight in kg)075
                               NRC (1989) recommends that lactating dairy cows be allowed a slightly
                                                 higher maintenance allowance:
                                      NEm (MJ/day) = 0.335 x (weight in kg)075   {dairy cows}
                            Additional energy is required for animals to obtain their food. Grazing animals
                            require more energy for this activity than do stall-fed animals. The following energy
                            requirements are added for this activity based on their feeding situation:8

                            -   Confined animals (pens and stalls): no additional NEm;
                            -   Animals grazing good quality pasture: 17% of NEm; and
                            —   Animals grazing over very large areas: 37% of NEm.
                            Growth
                            The energy requirements for growth can be estimated as a function of the weight of
                            the animal and the  rate of weight gain.  NRC (1989) presents formulae for large- and
                            small-frame males and females, the estimates from which vary by about ±25%. The
                            equation for large-frame females is recommended, which is about the average for the
                            four types:
                                                         EQUATION 2
                                      NEg (MJ/day) = 4.18 x (0.035 W075 x WG1
                                                   WG)  (2)
                                              animal weight in kilograms (kg); and
                                              weight gain in kg per day.
where:
W
WG
The relationships for NEg were developed for temperate agriculture conditions, and
may over-estimate energy requirements for tropical conditions, particularly for draft
animals that may have a lower fat content in their weight gain (Graham, 1985).
However, no data are available for improving the estimates at this time.
Lactation
Net energy for lactation has been expressed as a function of the amount of milk
produced and its fat content (NRC, 1989):
                                                         EQUATION 3
                                        NE, (MJ/day) = kg of milk/day x (1.47 + 0.40 x Fat %)
                            At 4.0% fat, the NE, in MJ/day is about 3.1 x kg of milk per day.

                            Draft Power
                            Various authors have summarized the energy intake requirements for providing draft
                            power (e.g., Lawrence, 1985; Bamualim and Kartiarso, 1985; and Ibrahim, 1985). The
                            strenuousness of the work performed by the animal influences the energy
                            requirements, and consequently a wide range of energy requirements have been
                            estimated. The values by Bamualim and Kartiarso show that about 10% of NEm
                           8  The original OECD method recommended slightly higher energy additions.  These
                        revised figures are based on newly-published information in AAC (1990).
 4.14

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                                                                                               AGRICULTURE
                  requirements are required per hour of typical work for draft animals. This value is
                  used as follows:
                                                EQUATION 4
                              NEdraft (MJ/day) = 0.10 x NEm x hours of work per day
                  Pregnancy
                  Daily energy requirements for pregnancy are presented in NRC (1984). Integrating
                  these requirements over a 281-day gestation period yields the following equation:
                                                EQUATION 5
                                     (MJ/281 -day period) = 28 x calf birth weight in kg
                  The following equation can be used to estimate the approximate calf birth weight as a
                  function of the cow's weight:9
                                                EQUATION 6
                              Calf birth weight (kg) = 0.266 x (cow weight in kg)079
                  Manipulating Equations 5 and 6, in conjunction with Equation I, shows that the NE
                  required for pregnancy is about 7.5% of NEm for the range of cow sizes considered in
                  this analysis. Therefore, a factor of 7.5% of NEm is added to account for the energy
                  required for pregnancy for the portion of cows giving birth each year.

              Based on these equations, each of the net energy components for each of the cattle
              categories can be estimated from the data collected in Step I: weight in kilograms; feeding
              situation; weight gain per day in kilograms; milk production in kilograms of 4% fat-
              corrected milk; number of hours of work performed per day; and portion that give birth.
              These net energy requirements must be translated into gross energy intakes. Also, by
              estimating the gross energy intake, the net energy estimates can be checked for
              reasonableness against expected ranges of feed intake as a percentage of animal weight. To
              estimate gross energy intake, the relationship between the net energy values and gross
              energy values of different feeds must be considered. This relationship can be summarized
              briefly as follows:

                  Digestible Energy    = Gross Energy - Fecal Losses

                  Metabolizable Energy = Digestible Energy - Urinary and Combustible Gas Losses

                  Net Energy        = Metabolizable Energy - Heat Increment
                  Net Energy         = Gross Energy - Fecal Losses - Urinary and Combustible
                                             Gas Losses - Heat Increment

              The quantitative relationship among these energy values varies among feed types.
              Additionally, the values depend on how the feeds are prepared and fed, and the level at
              which they are fed. For purposes of this method, simplifying assumptions are used to
              derive a relationship between net energy and digestible energy that is reasonably
                 9 This species-specific equation from Robbins and Robbins (1979) was adjusted to the
              mean cow and calf weight of a typical beef breed of cattle. This adjustment increases the
              coefficient in the equation from 0.214 to 0.266.
PART 2
4.15

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AGRICULTURE
                       representative for the range of diets typically fed to cattle. Gross energy intake is then
                       estimated using this relationship and the digestibility data collected in Step I.

                       Given the digestibility of the feed (defined in Step I), a general relationship between
                       digestible energy and metabolizable energy can be used as follows (NRC, 1984):
                                                         EQUATION 7
                                      Metabolizable Energy (ME) = 0.82 x Digestible Energy (DE)
                       Equation 7 is a simplified relationship; larger (smaller) methane conversion rates would
                       tend to reduce (increase) the coefficient to values below (above) 0.82.
                       NRC (1984) presents separate quantitative relationships between metabolizable energy
                       and net energy used for growth versus net energy used for other functions. Using
                       Equation 7, the NRC relationships can be re-arranged to quantify the ratio of NE to DE, as
                       follows:
                              NE/DE
                  EQUATION 8
=  1. 123 - 4.092 x 10J x DE% + 1. 126 x I O's x (DE%)2 - 25.4/DE%
                                                          EQUATION 9
                              NEj/DE   = 1. 164 - 5.160 x IO'3 x DE% +  1.308 x IO'5 x (DE%)2 - 37.4/DE%
                            where:
                            NE/DE     =      the ratio of net energy consumed for maintenance, lactation,
                            work and pregnancy to digestible                      energy consumed;
                            NEg/DE     =      the ratio of net energy consumed for growth to digestible
                            energy consumed; and
                            DE%       =      digestible energy as percentage of gross energy, expressed in
                            percent (e.g., 65%).
                        Because the NRC (1984) relationships were developed based on diets with relatively high
                        digestibilities (generally above 65%), they may not be appropriate for the relatively low
                        digestibility diets that are commonly found in tropical livestock systems. In particular, the
                        non-linear nature of the relationships could bias the estimates of feed intake upward for
                        low-digestibility feeds. An upward bias in feed intake would lead to an upward bias in
                        emissions estimates.
                        Based on a review of other energy  systems (e.g., ARC, 1980), a linear relationship between
                        digestible energy and net energy was derived for digestibilities below 65% as follows (see
                        Appendix C):
                                                NE/DE
                  EQUATION 10
                  = 0.298 + 0.00335 x DE%
 4.16

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                                                                                             AGRICULTURE
                                              EQUATION 11
                                              = -0.036 + 0.00535 x DE%
              Given the estimates for feed digestibility (from Step I) and equations 8 through 11, the
              gross energy intake (GE in MJ/day) can be estimated as follows:
                       EQUATION 12
GE = [(NEm+NEfMd+NEl+NEw+NEp) / {NE/DE}
                         (DE%/IOO)
                                                                  (NEg / {NE/DE})] /
                  where:

                  {NE/DE} is computed from equation 8 for digestibility greater than 65% and from
                  equation 1 0 for digestibility less than or equal to 65%;
                          is computed from equation 9 for digestibility greater than 65% and from
                  equation 1 1 for digestibility less than or equal to 65%; and

                  DE% is digestibility in percent (e.g., 60%).
             To check the estimate of daily gross energy intake from equation 1 2, the estimate can be
             converted in daily intake in kilograms by dividing by 1 8.45 MJ/kg. This estimate of intake in
             kilograms should generally be between 1 .5% and 3.0% of the animal's weight.
             Using Equation 12 and the cattle data summarized in Appendix A, Gibbs and Johnson
             (1993) found that the intake estimates are consistent with expected intakes as a percent
             of body weight and previously published values. For example, the intake estimate for Indian
             cattle is the equivalent of about 1 0,000 MJ per year of metabolizable energy (ME).
             Winrock (1978) estimates the average ME requirements for Indian cattle at 10,600 MJ per
             year. Similarly, the ME values implied for U.S. dairy and beef cows are 58,000 MJ and
             3 1 ,000 MJ per year, respectively, which are similar to estimates of 62,000 MJ and 3 1 ,700
             MJ derived in U.S. EPA (1993). Consequently, for a diverse set of conditions, the intake
             estimates correspond to reasonably expected ranges from previously published estimates.
             To estimate the emission factor for each cattle type, the feed intake is multiplied by the
             methane conversion rate (from Step  I ) as follows:
                                              EQUATION 13
                    Emissions (kg/yr) = Intake (MJ/day) x Ym x 365 days / 55.65 MJ/kg of methane
             where Ym is the methane conversion rate expressed in decimal form (such as 0.06 for 6%).
             The result of this step of the method is an emission factor for each cattle type defined in
             Step I.
              L*ei"< t£f,f  t
                       io,FE,RMEN;r/moN  TI^R  2:  STEP 3 -- TOTAL
                       Hf^** *       \    *f A. s*. Jt.                           ^
                                        -•  *
             To estimate total emissions the selected emission factors are multiplied by the associated
             animal population and summed. As described above under Tier I, the emissions estimates
             should be reported in gigagrams (Gg).
PART 2
                                                                                      4.17

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AGRICULTURE
                       Tier 2 Approach For Manure Management Emissions
                       The Tier 2 approach provides a more detailed method for estimating methane emissions
                       from manure management systems. The Tier 2 approach is recommended for countries
                       with large cattle, buffalo and swine populations managed under confined conditions.
                       Compared to the Tier I approach, this method requires additional detailed information on
                       animal characteristics and the manner in which manure is managed. Using this additional
                       detailed information, emission factors are estimated that are specific to the conditions of
                       the country, and the default emission factors from Tier I are not used.
                       The Tier 2 approach is similar to the original OECD method described in OECD (1991).
                       Improvements to the method have been made to incorporate more recent figures on
                       methane conversion factors and to link the method more closely to  the animal
                       characteristic data collected for estimating enteric fermentation.
                       MANURE  MANAGEMENT T
                       LIV ESTO C K P C> P'U LATi O N Sl
2:  STEP
•---•-•••  •
                       To develop precise estimates of emissions, the animals should be divided into categories of
                       relatively homogeneous groups. For each category a representative animal is chosen and
                       characterized for purposes of estimating an emission factor. Suggested categories for cattle
                       are discussed above under the enteric fermentation Tier 2 method and are summarized in
                       Table 4-7. Similar categories can be used for buffalo. Categories for swine could include
                       sows, boars, and growing animals (farrows to finishers). For each of the representative
                       animal types defined, the following information is required:
                       •    annual average population (number of head) by climate region (cool, temperate, and
                            warm);
                       •    average daily manure volatile solids (VS) excretion (kg per day of dry matter);10
                       •    methane producing potential (B0) of the manure (cubic meters (m3) of methane per
                            kgofVS);
                       •    manure management system usage (percentage of manure managed with each
                            manure management system).
                       Population data are generally available from country-specific livestock census  reports. As
                       described above under Tier I, the portion of each animal population in cool,  temperate,
                       and warm climate regions is required.
                       Often, data on average daily VS excretion are not available. Consequently, the VS values
                       may need to be estimated from feed intake levels. The enteric fermentation Tier 2 method
                       should be used to estimate feed intake levels for cattle and buffalo.''  For swine, country-
                       specific swine production data may be required to estimate feed intake. To develop the
                       default emission factors for swine presented in Tier I, average feed intake estimates for
                       swine in developed and developing countries were used from Crutzen et al. (1986) (see
                       Appendix B).
                           10 Volatile solids (VS) are the degradable organic material in livestock manure.

                           11   By  using the  enteric fermentation  Tier 2  method  to estimate  feed intake,
                        consistency is assured in the data underlying the emissions estimates for  both enteric
                        fermentation and manure management.
 4.18

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                                                                                               AGRICULTURE
             Once feed intake is estimated, the VS excretion rate is estimated as:12
                                               EQUATION 14
                      VS (kg/day dry) = Intake (MJ/day) * (I kg/18.45 MJ) * (I - DE%/IOO) * (I-
                                                 ASH%/IOO)
                  where:

                  VS = VS excretion per day on a dry weight basis;

                  Intake      = the estimated daily average feed intake in MJ/day;

                  DE%       = the digestibility of the feed in percent (e.g., 60%);

                  ASH%      = the ash content of the manure in percent (e.g., 8%).

              For cattle, the DE% value used should be the same value used to implement Tier 2 for
              enteric fermentation. The ash content of cattle and buffalo manure is generally around 8%.
              For swine, the default emission factors were estimated using 75% and 50% digestibility for
              developed and developed countries, respectively, and an ash content of 2% and 4% for
              developed and developed countries, respectively. Appendix B summarizes the data used to
              estimate the VS excretion rates for cattle, buffalo, and swim;.

              The maximum methane-producing capacity for the manure (B0) varies by species and diet.
              Country specific data should be used where feasible. A range of representative B0 values
              for cattle, buffalo, and swine populations were used to develop the default emission factors
              as follows (see Appendix B):

              •    Dairy Cattle

                       Developed Countries: 0.24 m3/kg VS
                  -   Developing Countries: 0.13 m3/kg VS
              •    Non-Dairy Cattle

                       Developed Countries: 0.17 m3/kg VS
                       Developing Countries: 0.10 m3/kg VS
              •    Buffalo in all regions: 0.10 m3/kg VS

              •    Swine

                       Developed Countries: 0.45 rrvVkg VS
                       Developing Countries: 0.29 m3/kg VS
              The portion of manure managed in each manure management system must also be
              collected for each representative animal type. Table 4-8  summarizes the main types of
              manure management systems. The first four types in the table, pasture, daily spread, solid
              storage, and drylot are all dry manure management systems. These systems produce little
              or no methane. The wet manure management systems, liquid/slurry, anaerobic lagoon, and
              pit storage are the primary sources of manure methane emissions. To implement this
              Tier 2 method, at a minimum the proportion of manure  managed in wet and dry systems
              must be estimated.

              The default emission factors presented in Tier I are based on manure management system
              usage data collected by Safley et al. (1992). Appendix B presents these data by region for
              cattle, buffalo, and swine. Although the data in Appendix B can be used as defaults,

                 12  The energy density of feed is about 18.45  MJ per kg of dry  matter.  This value is
              relatively  constant across  a wide  range  of forage and grain-based feeds  commonly
              consumed by livestock.
PART 2
                                                                                                                4.19

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AGRICULTURE
                       country-specific data, e.g., obtained through a survey, would improve the basis for
                       implementing the Tier 2 method. The resulting estimates must show the portion of
                       manure from each animal type managed within each management system, by climate
                       region.
                       Emission factors are estimated for each animal type based using the daia collected in
                       Step I and the methane conversion factors (MCFs) for each manure management system.
                       The MCF defines the portion of the methane producing potential (B0) that is achieved. The
                       MCF varies by manure management system and climate and can range between 0 and 100
                       percent. Table 4-8 presents the latest available MCF estimates for the major manure
                       managements systems that have been developed.

                       To calculate the emission factor for each animal type, a weighted average methane
                       conversion factor (MCF) is calculated using the estimates of the manure managed by waste
                       system within each climate region. The average MCF is then multiplied by the VS excretion
                       rate and the B0 for the animal type. In equation form, the estimate is as follows:
                                                         EQUATION 15
                            where:

                            EF,

                            VS,

                            Bo,
                             and
annual emission factor (kg) for animal type i (e.g., dairy cows);

daily VS excreted (kg) for ariimal type i;
maximum methane producing capacity (m3/kg of VS) for manure
produced by animal type /;
methane conversion factors for each manure management
system; by climate region k;


fraction of animal type fs manure handled using manure system j
in climate region k.
                        To estimate total emissions the selected emission factors are multiplied by the associated
                        animal population and summed. As described above under Tier I, the emissions estimates
                        should be reported in gigagrams (Gg).

                        Beyond Tier 2
                        The default values used in the Tier I and 2 methods were derived from available livestock
                        and manure management data and are generally representative of regional conditions.
                        Because livestock and manure management conditions can vary significantly across and
                        within countries, the default values may not reflect adequately the conditions in a given
                        country. Additionally, the variability of conditions has not been well characterized to date.
 4.20

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                                                                                              AGRICULTURE
            The emissions estimates can be improved by going beyond (the Tier 2 default data and
            collecting key country- or region-specific data. Data elements that would benefit from data
            collection initiatives (such as targeted surveys of major livestock types) include the
            following:

            •   Cattle weight
                 In many regions the weights of cattle are not well quantified.

            •   Feed intake
                 Field data on feed intake would be valuable for validating the feed intake estimates
                 made under Tier 2 for cattle.

            •   Manure production
                 Field data on manure production by livestock would be valuable for validating the
                 manure production estimates made under Tier 2.

            •   Manure management
                 Field data on manure management system usage would improve the basis for making
                 the estimates. Considerations of seasonal management practices could be
                 incorporated into the data.

             In addition to these data collection initiatives, measurement: programs can be used to
             improve the basis for making the estimates. In particular, measuring emissions from
             manure management systems under field conditions is needed. Techniques for making
             these measurements are described in  IAEA (1992). Additionally, measurements of the
             maximum methane producing ability of manure (B0) from livestock in tropical regions is
             needed.
             Additionally, new techniques are being deployed to measure emissions from cattle under
             field conditions (Johnson et al., 1993). Using these techniques, coefficients used in Tier 2
             can be verified (such as the methane conversion rate) and che emissions estimates can be
             validated. Targeted assessments of tropical cattle populations would be most valuable.
PART 2
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              4.2.1 References

                       AAC (Australian Agricultural Council) (1990), Feed Standards for Australian Livestock.
                       Ruminants, Commonwealth Scientific and Industrial Research Organization (CSIRO)
                       Publications, East Melbourne, Victoria, Australia.
                       ARC (Agriculture Research Council) (1980), The Nutrient Requirements of Ruminant
                       Livestock, Commonwealth Agricultural Bureaux, The Lavenham Press Ltd., the United
                       Kingdom.
                       Bamualim, A., and Kartiarso (1985). "Nutrition of draught animals with special reference to
                       Indonesia," in Copland, J.W., ed. Drought Animal Power for Production, Australian Centre for
                       International Agricultural Research (ACIAR) Proceedings Series No. 10. ACIAR, Canberra.
                       A.C.T., Australia.
                       Blaxter, K.L, and J.L Clapperton (1965), "Prediction of the amount of methane produced
                       by ruminants," British Journal of Nutrition 19:511-522.
                       Crutzen, P.J.. I. Aselmann, and W. Seiler (1986), "Methane Production by Domestic
                       Animals, Wild Ruminants, Other Herbivorous Fauna, and Humans," Teffus 386:271-284
                       FAO (Food and Agriculture Organization) (1990), Yearbook - Production Vol. 44, FAO,
                       United Nations, Rome, Italy.
                       Gibbs, M.J. and D.E.Johnson (1993). "Livestock Emissions,"  in International Methane
                       Emissions, U.S. Environmental Protection Agency, Climate Change Division, Washington,
                       D.C. (in press).
                       Graham, N.M. (1985), "Relevance of the British metabolisable energy system to the feeding
                       of draught animals," in Copland, J.W., ed.  Drought Animal Power for Production, ACIAR
                       (Australian Centre for International Agricultural Research) Proceedings Series No.  10.
                       ACIAR, Canberra, A.C.T., Australia.
                       Hashimoto, A. and J. Steed (1993). Methane Emissions from Typical U.S. Livestock Manure
                       Management Systems, Draft report prepared for ICF Incorporated under contract to the
                       Global Change Division of the Office of Air and Radiation, U.S. Environmental Protection
                       Agency, Washington, D.C.
                       IAEA (International Atomic Energy Agency) (1992), Mam/of on measurement of methane and
                       nitrous oxide emissions from agricu/ture, International Atomic Energy Agency Publication
                       IAEA-TECDOC-674, Vienna. Austria.
                       Ibrahim, M.N.M. (1985), "Nutritional status of draught animals in Sri Lanka," in Copland,
                       J.W., ed. Draught Animal Power for Production, ACIAR (Australian Centre for International
                       Agricultural Research) Proceedings Series No. 10. ACIAR, Canberra, A.C.T., Australia.
                       Johnson, KA, H. Westberg, M. Hyler, and B. Lamb (1993), Cattle Methane Measurement
                       Techniques Workshop, August 9-12,  1993, Washington State University, Pullman, WA,
                       sponsored by the Global Change Division, Office of Air and Radiation, U.S. Environmental
                       Protection Agency, Washington, D.C.
                       jurgens, M.H. (1988), Animal Feeding and Nutrition, Sixth Edition, Kendall/Hunt Publishing
                       Company, Dubuque, Iowa.
                        Lawrence, P.R. (1985), "A review of nutrient requirements of draught oxen," in Copland,
                       J.W., ed. Draught Animal Power for Production, ACIAR (Australian Centre for International
                       Agricultural Research) Proceedings Series No. 10. ACIAR, Canberra, A.C.T., Australia.
 4.22

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                                                                                              AGRICULTURE
             Lichtman, R. J. (1983), Biogos Systems in India, Volunteers In Technical Assistance (VITA),
             Arlington, Virginia.
             NRC (National Research Council) (1984), Nutrient Requirements of Beef Cattle, National
             Academy Press, Washington, D.C.
             NRC (National Research Council) (1989), Nutrient Requirements of Dairy Cattle, National
             Academy Press, Washington, D.C.
             OECD (Organization for Economic Cooperation and Development) (1991), Estimation of
             Greenhouse Gas Emissions and Sinks: Final Report from the OECD Experts Meeting, 18-21
             February 199 /, OECD, Paris, France.
             Robbins, C.T., and D.L Robbins (1979), "Fetal and neonatal growth patterns and maternal
             reproductive effqrt in ungulates and sub-ungulates," Amer. Naturalist  114:101.
             Safley, L.M., M.E. Casada, J.W. Woodbury, and K.F. Roos (1992). Global Methane Emissions
             from Livestock and Poultry Manure. U.S. Environmental Protection Agency, Global Change
             Division. Washington, D.C., February 1992, EPA/400/1091 /048.
             Safley, LM. Jr.,  and P.W. Westerman, (1992), "Performance! of a low temperature lagoon
             digester," Bioresource Technology 41:167-175.
             Stuckey, D.C. (1984), "Biogas: a global perspective," in EI-Halwagi, MM., ed. Biogos
             Technology, Transfer and  Diffusion, Elsevier, New York, pages  18-44.
             U.S. EPA (U.S.  Environmental Protection Agency) (1993), Anthropogenic Methane Emissions
             in the United States, Global Change Division, Office of Air and Radiation, Washington, D.C.
             Winrock (Winrock International) (1978), The Role of Ruminants in Support of Man, Winrock
             International, Morrilton, Arkansas.
             Woodbury, J.W. and A. Hashimoto (1993). "Methane Emissions from Livestock Manure,"
             in International Methane  Emissions, U.S. Environmental Protection Agency, Climate Change
             Division, Washington, D.C. (in press).
             Yancun, C, H. Cong, and Liang Pusen (1985), "Development of a new energy village -
             Xinbu, China," in El Mahgary, Y., and A.K. Biswas, eds. integrated Rural Energy Planning,
             Butter-worths Publishing, Guildsford, England, pages 99-108.
PART 2
                                                                                                                 4.23

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AGRICULTURE
                                                              TABLE 4-1
                                            DOMESTIC LIVESTOCK INCLUDED IN THE METHODS
              Livestock
Recommended Emissions Inventory Methods
                                                      Enteric Fermentation
                                                                                          Manure Management
              Dairy Cows
              Cattle Other than Dairy Cows
              Buffalo
              Sheep
              Goats
              Camels
              Horses and Mules
              Swine
              Poultry
Tier I
Tier I
Tier I
Tier I
Tier I
(Not Estimated)
Tier I
Tier I
Tier I
Tier I
Tier24
 T
fieri
              a The Tier 2 approach is recommended for countries with large livestock populations. Implementing the Tier 2 approach for additional
              Kvdtock subgroups may be desirable when the subgroup emissions are a large portion of total methane emissions for the country.
4.24

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                                                 AGRICULTURE
TABLE 4-2
ANIMAL POPULATION DATA COLLECTED IN TIER 1 STEP 1
Livestock




Dairy Cows

Cattle Other than Dairy
Cows
Buffalo

Sheep

Goats

Camels

Horses and Mules

Swine

Poultry

Data Collected
Population

(# head)

Average Annual
Population
Average Annual
Population
Average Annual
Population
Average Annual
Population
Average Annual
Population
Average Annual
Population
Average Annual
Population
Average Annual
Population
Average Annual
Population

Milk Production
(kg/head/yr)


Milk Production per
Head
Not Applicable (NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)


Population By Climate (%)


Cool Temperate


% Cool % Temp.

%Cool %Temp.

% Cool % Temp.

%Cool %Temp.

% Cool % Temp.

% Cool % Temp.

% Cool % Temp.

% Cool % Temp.





Warm


%Warm

%Warm

%Warm

%Warm

%Warm

%Warm

%Warm

%Warm

Data can be obtained from the FAO Production Yearbook and country-specific livestock census reports. Climates are defined in terms ot
average annual temperature as follows: Cool = less than 1 5°O Temperate = greater than 1 S°C and less than 2S°C; Warm = greater than
25°C.




TABLE 4-3
ENTERIC FERMENTATION EMISSION FACTORS
(kg per head per year)
Livestock
Buffalo
Sheep
Goats
Camels
Horses
Mules and Asses
Swine
Poultry
All estimates are ±20 percent
Developed Countries
55
8
5
46
18
10
1.5
Not Estimated


55
5
5
46
18
10
1.0


Sources: Emission factors for buffalo and camels from Gibbs and Johnson (1993). Emission factors for other livestock from Crutzen et al.
(1986).


^ 	 %,..,....,£...£.£... £„.£. ,^s.=^sss;.,^&V,^^^mS!^y!X!l^f!Sff!mi^/yl^f^im^t^!&
PART 2
                                                            4.25

-------
AGRICULTURE
TABLE 4-4
ENTERIC FERMENTATION EMISSION FACTORS FOR CATTLE
Regional Characteristics
North America: Highly productive commercialized dairy sector
Feeding high quality forage and grain. Separate beef cow herd,
primarily grazing with feed supplements seasonally. Fast-growing
beef steers/heifers finished in feedlots on grain. Dairy cows are a
small pan of the population.
Western Europe: Highly productive commercialized dairy
sector feeding high quality forage and grain. Dairy cows also
used for beef calf production. Very small dedicated beef cow
tent Minor amount of feedlot feeding with grains.
Eastern Europe: Commercialized dairy sector feeding mostly
forages. Separate beef cow herd, primarily grazing. Minor
amount of feedlot feeding with grains.
Oceania: Commercialized dairy sector based on grazing.
Separate beef cow herd, primarily grazing rangelands of widely
varying quality. Growing amount of feedlot feeding with grains.
Dairy cows are a small part of the population.
Latin America-. Commercialized dairy sector based on grazing.
Separate beef cow herd grazing pastures and rangelands. Minor
amount of feedlot feeding with grains. Growing beef catde
comprise a large portion of the population.
Asia-. Small commercialized dairy sector. Most catde are multi-
purpose, providing draft power and some milk within farming
regions. Small grazing population. Cade of all types are smaller
than those (bund in most other regions.
Africa and Middle East: Commercialized dairy sector based
on grazing with low production per cow. Most catde are multi-
xirpose, providing draft power and some milk within farming
regions. Some cattle graze over very large areas. Catde of all
types arc smaller than those found in most other regions.
ndlan Subcontinent: Commercialized dairy sector based on
crop byproduct feeding with low production per cow. Most
Hillocks provide draft power and cows provide some milk in
farming regions. Small grazing population. Catde in this region
are die smallest compared to catde found in all omer regions.
Animal Type
Dairy Cows
Non-Dairy Catde
Dairy Cows
Non-Dairy Catde
Dairy Cows
Non-Dairy Catde
Dairy Cows
Non-Dairy Catde
Dairy Cows
Non-Dairy Catde
Dairy Cows
Non-Dairy Catde
Dairy Cows
Non-Dairy Catde
Dairy Cows
Non-Dairy Catde
Emission Factor
(kg/head/yr)
118
47
100
48
81
56
68
S3
57
49
56
44
36
32
46
25
Comments
Average milk production of 6,700 kg/yr
Includes beef cows, bulls, calves, growing
steers/heifers, and feedlot cattle
Average milk production of 4,200 kg/yr
Includes bulls, calves, and growing
steers/heifers
Average milk production of 2,550 kg/yr
Includes beef cows, bulls, and young.
Average milk production of 1 ,700 kg/yr
Includes beef cows, bulls, and young.
Average milk production of 800 kg/yr
Includes beef cows, bulls, and young.
Average milk production of 1,650 kg/yr
ncludes multi-purpose cows, bulls, and
young.
Average milk production of 475 kg/yr
ncludes multi-purpose cows, bulls, and
young.
Average milk production of 900 kg/yr
ncludes cows, bulls, and young. Young
comprise a large portion of the
jopulation.
4.26

-------

                                                                                                          AGRICULTURE
                                                      TABLE 4-5
                                       MANURE MANAGEMENT EMISSION FACTORS
                                                  (kg per head per year)
   Livestock
                                                  Developed Countries
                      Developing Countries
                                                   Cool
Temp.a
                                                                          Warm
                                                                                     Cool
Temp.a
                                                                                                             Warm
    Sheep
                                                  0.19
                                                            0.28
                                                                         0.37
                                                                                   0.10
                                                                                              0.16
                                                                                                           0.21
    Goats
                                                  0.12
                                                            0.18
                                                                         O.B
                                                                                   O.I I
                                                                                              0.17
                                                                                                           0.22
    Camels
                                                  1.6
                                                            2.4
                                                                         3.2
                                                                                    1.3
                                                                                              1.9
                                                                                                           2.6
    Horses
                                                  1.4
                                                            2.1
                                                                         2.8
                                                                                              1.6
                                                                                                           2.2
    Mules and Asses
                                                  0.76
                                                            1.14
                                                                          1.51
                                                                                    0.60
                                                                                              0.90
                                                                                                           1.2
    Poultry
                                                  0.078
                                                            0.117
                                                                         O.I 57
                                                                                    0.012
                                                                                              0.018
                                                                                                           0.023
    The range of estimates reflects cool to warm climates. Climate regions are defined in terms of annual average temperature as follows:
    Cool = less than IS°C; Temperate = IS°C to 25°C; and Warm = greater than 25°C Trie Cool. Temperate and Warm regions are
    estimated using MCFs of I %, 1.5% and 2%. respectively.
    a Temp. = Temperate climate region.
    b Chickens, ducks, and turkeys.
    All estimates are ±20 percent.
    Sources: Emission factors developed from: feed intake values and feed digestibilities used to develop the enteric fermentation emission
    factors (see Appendix A); MCF, and Bo values reported in Woodbury and Hashimoto (1993). All manure is assumed to be managed in dry
    systems, which is consistent with the manure management system usage reported in Woodbury and Hashimoto (1993).	
PART 2
                                                                                                                               4.27

-------
AGRICULTURE
TABLE 4-6
MANURE MANAGEMENT EMISSION FACTORS FOR CATTLE, SWINE AND BUFFALO
Regional Characteristics Animal Type
North America: Liquid-based systems are common!/ used for
dairy and swine manure. Non-dairy manure is usually managed
as a solid and deposited on pastures or ranges.
Western Europe: Liquid/slurry and pit storage systems are
commonly used for cattle and swine manure. Limited cropland
is available for spreading manure.
Eastern Europe: Solid based systems are used for the
majority of manure. About one-third of livestock manure is
managed in liquid-based systems.
Oceania: Virtually all livestock manure is managed as a solid
on pastures and ranges. About half of the swine manure is
managed in anaerobic lagoons.
Latin America: Almost all livestock manure is managed as a
solid on pastures and ranges. Buffalo manure is deposited on
pastures and ranges.
Africa: Almost all livestock manure is managed as a solid on
pastures and ranges.
Middle Ease Over two-thirds of cattle manure is deposited on
pastures and ranges. About one-third of swine manure is
managed in liquid-based systems. Buffalo manure is burned for
fuel or managed as a solid.
Asia: About half of catde manure is used for fuel with the
remainder managed In dry systems. Almost forty percent of
swine manure is managed as a liquid. Buffalo manure is
managed in drylots and deposited in pastures and ranges.
Indian Subcontinent: About half of cattle and buffalo manure
is used for fuel with the remainder managed in dry systems.
About one-third of swine manure is managed as a liquid.
a Cool climates have an average temperature below IS°C; tern]
warm climates have an average temperature above 25°C. All clin
example, there are no significant warm areas in Eastern or West
Middle East. See Appendix B for the derivation of these emission
Mote: Significant buffalo populations do not exist in North Amer
Dairy Cows
Non-Dairy Cows
Swine
Dairy Cows
Non-Dairy Cows
Swine
Buffalo
Dairy Cows
Non-Dairy Cows
Swine
Buffalo
Dairy Cows
Non-Dairy Cows
Swine
Dairy Cows
Non-Dairy Cows
Swine
Buffalo
Dairy Cows
Non-Dairy Cows
Swine
Dairy Cows
Non-Dairy Cows
Swine
Buffalo
Dairy Cows
Non-Dairy Cows
Swine
Buffalo
Dairy Cows
Non-Dairy Cows
Swine
Buffalo
erate climates have an ave
late categories are not nee
ern Europe. Similarly, then
factors.
ica, Oceania, or Africa.
Emission Factor by Climate Region3
(kg/head/year)
Cool
36
1
10
14
6
3
3
6
4
4
3
31
5
19
0
1
1
1
1
0
0
1
1
1
4
7
1
1
1
Temperate
54
2
14
44
20
II
8
19
13
7
9
32
6
19
1
2

2
3
5
16
1
4
2
Warm
76
3
18
81
38
20
17
33
23
II
16
33
7
20
2
1
3
2
1
1
2
2
1
6
5
27
2
7
3
556
222
346
455
•age temperature between I5°C and 25°C;
essarily represented within every region. For
: are no significant cool areas in Africa and the
4.28

-------
                                                 AGRICULTURE
TABLE 4-7
RECOMMENDED REPRESENTATIVE CATTLIE TYPES
Main Categories
Mature Dairy Cows
Mature Non-Dairy Cattle
Young Cattle
Sub-Categories
Used principally for commercial milk production
Mature Females:
• Beef Cows: used principally for producing beef steers and heifers
• Multiple-Use Cows: used for milk production, draft power, and other uses
Mature Males:
• Breeding Bulls: used principally for breeding purposes
• Draft Bullocks: used principally for draft power
Pre-Weaned Calves
Growing Heifers, Steers/Bullocks and Bulls
Feedlot-Fed Steers and Heifers on High-Grain Diets
PART 2
                                                           4.29

-------
AGRICULTURE
TABLE 4-8
MANURE MANAGEMENT SYSTEMS AND METHANE CONVERSION FACTORS (MCFs)
System
Pasture/Range/Paddoclc The manure from pasture and range grazing animals
is allowed Co lie as is, and is not managed.
Daily Spread Manure is collected in solid form by some means such as scraping.
The collected manure is applied to fields regularly (usually daily).
Solid Storage: Manure is collected as in the daily spread system, but is stored in
bulk for a long period of time (months) before any disposal.
Drylot In dry climates animals may be kept on unpaved feedlots where the
manure Is allowed to dry until it is periodically removed. Upon removal the
manure may be spread on fields.
Liquid/Slurry These systems are characterized by large concrete lined tanks
built into the ground. Manure is stored in the tank for six or more months until it
can be applied to fields. To facilitate handling as a liquid, water may be added to
the manure.
Anaerobic Lagoon Anaerobic lagoon systems are characterized by flush
systems that use water to transport manure to lagoons. The manure resides in
the lagoon for periods from 30 days to over 200 days. The water from the lagoon
may be recycled as flush water or used to irrigate and fertilize fields.
Pit Storage Liquid swine manure may be stored In a pit while < 30 Days
awaiting final disposal. The length of storage time varies, and for
this analysis is divided into two categories: less than one month
or greater than one month.
> 30 Days
Anaerobic Digester The manure, in liquid or slurry form, is anae-robically
digested to produce methane gas for energy. Emissions are from leakage and vary
with the type of digester.
Burned for Fuel Manure is collected and dried In cakes and burned for heating
or cooking. Emissions occur while the manure is stored before it is burned.
Methane emission associated with the combustion of the manure are not
considered here. Combustion-related emissions are estimated in the Traditional
Btomass Fuels section of the Energy chapter.
MCF by Climate3
Cool , , Temperate Warm
1% 1.5% 2%
0.1% 0.5% 1.0%
1% 1.5% 2%
1% 1.5% 5%
10% 35% 65%
90% 90% 90%
5% 18% 33%
10% 35% 65%
5-15% 5-15% 5-15%
5-10% 5-10% 5-10%
Source
b
b
b
b
b
c
b
b
d
e
a Cool climates have an average temperature below I5°C; temperate climates have an average temperature between I5°C and 25°C;
warm climates have an average temperature above 25°C.
b Hashimoto and Steed (1993).
c Safley ec al., (1992) and Safley and Westerman (1992).
d Yancun et al. (1985), Stuckey (1984) and Uchtman (1983).
e Safleyetal. (1992).
4.30

-------
                                                                             AGRICULTURE
   Appendix A
           Data Underlying Default  Emission  Factors

           for Enteric Fermentation

           This appendix presents the data used to develop the default emission factors for methane
           emissions from enteric fermentation. The detailed information presented for cattle and
           buffalo was developed in Gibbs and Johnson (1993). The Tier 2 method was implemented
           with these data to estimate the default emission factors for cattle and buffalo. Also
           presented are the summary data from Crutzen et al. (1986) that were used to estimate
           the emission factors for the other species.
PART 2
                                                                                           4.31

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-------
AGRICULTURE
     Appendix B    Data  Underlying  Default  Emission

              Factors for Manure  Management

              This appendix presents the data used to develop the default emission factors for methane
              emissions from manure management The detailed information presented for cattle and
              buffalo were developed in Gibbs and Johnson (1993). The swine feed intake data are from
              Crutzen et al. (1986). The manure management system usage data and B0 estimates are
              from Safley et al. (1992). The methane conversion factor (MCF) data are from Woodbury
              and Hashimoto (1993). The Tier 2 method was implemented with these data to estimate
              the default emission factors for cattle, buffalo, and swine. Also presented are the summary
              feed intake data from Crutzen et al. (1986) and the manure-related data from Safley et al.
              (1992) and Woodbury and Hashimoto (1993) that were used to estimate the emission
              factors for the other species.
  PART 2
                                                                                                  4.37

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AGRICULTURE
          Appendix  C    Derivation  of  Tier 2  Enteric
                   Fermentation  Equations
                   This appendix summarizes the derivation of the relationship between net energy (NE) and
                   digestible energy (DE) that is used to estimate total feed-intake requirements for cattle.
                   This derivation is drawn from Gibbs and Johnson (1993).
                   As described in the main text, the relationship among the energy values of feed consumed
                   by cattle can be summarized as follows:
                       Digestible Energy   =
                       Metabolizable Energy =
                       Losses
                       Net Energy        =
Gross Energy - Fecal Losses
Digestible Energy - Urinary and Combustible Gas

Metabolizable Energy - Heat Increment
                       Net Energy        =      Gross Energy - Fecal Losses -
                                                Urinary and Combustible Gas Losses - Heat Increment
                   NRC (1984) presents the following quantitative relationships among these energy values:
                       ME        = 0.82 xDE    (C.I)
                       NEm       = 1.37 x ME-0.138 x ME2+ 0.0105 x ME3-1.12   (C.2)
                       NE£       = 1.42 x ME - 0.174 x ME2 + 0.0122 x ME3 - 1.65   (C.3)
                   where:
                       DE        = digestible energy in Meal/kg (dry matter basis);
                       ME        = metabolizable energy in Meal/kg (dry matter basis);
                       NEm       = net energy for maintenance in Meal/kg (dry matter basis); and
                       NEg       = net energy for growth in Meal/kg (dry matter basis).
                   Using these relationships, the ratio of NEm and NEg to ME or DE can be derived as
                   follows:
                       NE/DE =  I.I23-4.092X W3xDE% + I.l26x I0'sx (DE%)2- 25.4/DE% (C.4)
                       NEj/DE =  1.164 - 5.160 x IO'3 x DE% + 1.308 x IO'5 x (DE%)2 - 37.4/DE% (C.5)
                   where:
                       NE/DE     = the ratio of net energy consumed for maintenance, lactation, work
                       and pregnancy to digestible            energy consumed;
                       NEg/DE    = the ratio of net energy consumed for growth to digestible energy
                       consumed; and
                       DE%       = digestible energy as percentage of gross energy, expressed in  percent
                       (e.g., 65%).
                   Graph C-l shows the relationships in graphical form. As shown in the graph,  the ratio of
                   NE to DE is  non-linear, with an increasing slope with decreasing DE. These relationships
                   imply that at lower values of DE, cattle are able to recover a decreasing portion of the
                   energy to use for maintenance or growth.
4.46

-------
                                                                                               AGRICULTURE
             For purposes of estimating methane emissions from cattle, applying these relationships to
             cattle consuming relatively low-quality feeds (such as cattle in many tropical countries) may
             be inappropriate because the relationships were developed based on analyses of the
             higher-quality feeds typically found in the U.S. temperate agriculture system. Consequently,
             the experimental basis for extrapolating the non-linear relationships to low levels of DE is
             not very strong.
             In examining other energy systems, it is seen that they also indicate that the rate of net
             energy retention declines at lower values  of digestible energy. Unlike the NRC system,
             however, many imply a linear relationship  between NE and DE. The U.K. energy system
             (ARC, 1980), which is typical of the energy systems used in Europe, has a slope for the
             linear NEm:DE relationship that is similar to the slope  of the non-linear NRC relationship
             in the range of 65%-70% digestibility. Similarly, the slope of the U.K. NE^DE relationship is
             similar to the slope of the non-linear NRC relationship in the range of 60%-65%
             digestibility.
             To avoid possible biases in estimating feed-intake requirements in this study, the
             relationships were extrapolated linearly for DE values below 65% using the average slopes
             of the NRC relationships between 60% and 70% DE. The derived equations are as follows:

                     NE/DE = 0.298 + 0.00335 x DE% (C.6)
                     NEg/DE = -0.036 + 0.00535 x DE% (C.7)
             Graph C-2 shows the extrapolated linear relationships along with the non-linear estimates.
             As expected, the linear extrapolations fall above the original non-linear estimates.
             The implication of making this adjustment to the N RC (1984) relationship for the global
             emissions estimate is relatively minor. Gibbs and Johnson (1993) report that using the
             non-linear relationship to estimate global emissions from cattle increases the 1990
             emissions estimate by .001 Gg, from .0581 Gg to .0591 Gg. Considering the wide range of
             factors that contribute to uncertainty in the estimates, including characterization of animal
             populations, this adjustment has a minor influence on  the estimates.
PART 2
                                                                                                                 4.47

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AGRICULTURE
                Graph C-l: NRC NE:DE Relationship
                                   HE to DE Ratio by DE
                                     Derived from NRC (1984)
                  Ratio
                               48
52     56    60    64
  Digestible Energy (%)
                                                            68
                                                                 72
                                                                       76
                NEm
                NEf
4.48

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                                                                           AGRICULTURE
           Graph C-2: Linear Extrapolation Of The NRC NE:IOE Relationship
                                   NE to DE Ratio by DE
                   0.54
                   0.52
                   0.50
                   0.48
                   0.46
                   0.44
                   0.42
                   0.40
                   0.38
             RatiO 0.36
                   0.34
                   0.32
                   0.30
                   0.28
                   0.26
                   0.24
                   0.22
                   0.20
                   0.18
                       44
48
                                           r '

                                          72
76
                                       Digestible Energy (%)
            NETO       Linear Extrapolation
            NE(        Linear Extrapolation
PART 2
                                                                                          4.49

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AGRICULTURE
             4.3     Methane  Emissions from  Flooded  Rice
                       Fields
                       4.3.1  Overview

                       Anaerobic decomposition of organic material in flooded rice fields produces methane
                       (CH4). which escapes to the atmosphere primarily by diffusive transport through the rice
                       plants during the growing season. Upland rice fields, which are not flooded and therefore
                       do not produce significant quantities of CH4, account for approximately 10% of the global
                       rice production and about 15% of the global rice area under cultivation. The remaining
                       area is wetland rice, consisting of irrigated, rainfed, and deepwater rice. The global wetland
                       rice area harvested annually in the early 1980s was about 123.2 million hectares, over 90%
                       of which was in Asia (Neue et al., 1990).'3
                       Of the wide variety of sources for the atmospheric CH/}, rice paddy fields are considered
                       one of the most important sources. The Intergovernmental Panel on Climate Change
                       (Watson et al,  1992) estimated the global emission rate from paddy fields to be ranging
                       from 20 to I SO Tg/yr, averaged 60 Tg/yr. This is about 5-30% of the total emission from all
                       sources. This figure is mainly based on field measurements of CH4 fluxes from paddy fields
                       in the United States, Spain, Italy, China, India, Australia and Japan.

                       The measurements at various locations of the world show that there are large temporal
                       variations of CH4 fluxes and that the flux differs markedly with soil  type, application of
                       organic matter and mineral fertilizer. The wide variations in CH4 fluxes also indicate that
                       the flux is critically dependent upon several factors including climate, characteristics of
                       soils and paddy, and agricultural practices. On the other hand, about 90% of the world's
                       harvested area of rice fields is located in Asia. Of the total harvested area in Asia, about
                       60% is located in India and China.

                       Methane  production processes

                       The major pathways of CH4 production in flooded soils are the reduction  of CO2 with
                       H2, with fatty acids or alcohols as hydrogen donor, and the transmethylation of acetic acid
                       or methyl alcohol by methane producing bacteria (Takai 1970; Conrad 1989). In paddy
                       fields, the kinetics of the reduction processes are strongly affected by the composition and
                       texture of soil and its content of inorganic electron acceptors. The  period  between
                       flooding of the soil and  the onset of methanogenesis can apparently be different for the
                       various soils. However, it is unclear if soil  type also affects the rates of methanogenesis and
                       CH4 emission when steady state conditions have been reached (Conrad 1,989).
                          13 The term "harvested area" has a different meaning than "cultivated area" in that the
                       former accounts for double and triple cropping.  For example, if a country has 10 million
                       hectares of land under rice cultivation, all of which are double-cropped (i.e.,, two crops of
                       rice are grown on each hectare each year), then this country has 20 million hectares of
                       rice area harvested annually.
4.50

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                                                                                                AGRICULTURE
                       14
             The redox   potential is the most important factor for production of CH4 in soils. The Eh
             of the soil gradually decreases after flooding. This is due to a decrease in the activity of the
             oxidized phase and increased activity of the reduced phase. Takai etal. (1956)
             demonstrated that the redox potential of a soil must be below -200 mv in order to have
             CH4 production. Yamane and Sato (1964) also showed that: the evolution of CH4 from
             flooded paddy soils did not commence until the Eh fell below -200 mv. There is a
             correlation between the soil redox potential and methane emission (Patrick et al. 1981;
             Cicerone et al. 1983; Yagi and Minami 1990).

             Substrate and nutrient availability is also an important factor. Application of rice straw to
             paddy fields significantly increase CH4 emission rate compared with application of
             compost prepared from rice straw or chemical fertilizer.

             Soil temperature is known to be an important factor in affecting the activity of soil
             microorganisms. This is to a certain extent related to the soil moisture content because
             both the heat capacity and the heat conductivity are lower for a dry soil than for a wet
             soil. Yamane and Sato (1961) have already found that CH4 formation reached a maximum
             at 40°C in waterlogged alluvial soils. Above 40°C, CH4 formation decreased  and stopped
             at 60°C. The formation was very small below 20°C.

             It is generally recognized that CH4 formation is only efficient in a very narrow range
             around neutrality (pH from 6.4 to 7.8). Flooding will have an increasing effect on pH in
             acid soil, while it will decrease the pH in alkaline soil. The increase of pH in acid soils is
             mainly due to the reduction of acidic Fe   to Fe   .

             Growing plants on soils may also affect the emission of gaseous CH4. At later growth
             stages' of rice, more nitrogen gas and less CH4 were found in wetlands soils planted to rice
             than  in an unplanted rice field (Yoshida 1978). Yamane and Sato (1963) found that flooded
             soils  planted with rice frequently evolve less CH4 than the corresponding uncropped sites.
             The addition of sulfate as chemical fertilizer to flooded soils also influences the production
             of CH4 because of its effect on raising the redox potential  and of the toxic effect of its
             reduction product. Also, the addition of sulfate increases the activities of sulfate-reducing
             bacteria, which outcompete methanogens for the substrate. Sulfate must be reduced
             before CH4 is formed in paddy soils (Takai 1980).

             The addition of nitrate as chemical fertilizer to flooded  soils; may also suppress the
             production of CH4. Because nitrate acts as a terminal electron acceptor in the absence of
             molecular oxygen for anaerobic respiration and it poises the redox potential of soils at
             values such that the activity of strict anaerobes is prevented.

             There are three processes of CH4 release into the atmosphere from rice paddies.
             Methane loss as bubbles from paddy soils is a common and significant mechanism. Diffusion
             loss of CH4 across the water surface is another process. The third, CH4 transport
             through  rice plants, which has been reported (Seiler et al. 1984; Cicerone et al.  1983;
             Minami and Yagi 1988; Nouchi et al. 1990), as the most important phenomenon.

             Many researchers reported that more than 90% of the total CH4 released from rice
             paddies is diffusive transport through the aerenchym system of the rice plants and not
             through  diffusion or escape of bubbles across the air-water interface. Emission through
             plants may be expected to show great seasonal variations tied to environmental changes in
             soil conditions and variations in plant growth stage, respiration and photosynthesis rates.
                 14 Redox refers to oxidation-reduction, two processes that take place simultaneously.
              Oxidation is the loss of an electron by an atom, and reduction is the gain of an electron by
              an atom.
PART 2
4.51

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AGRICULTURE
                       Although CH4 flux rates are revealed to be a function of the total amount of CH4 in the
                       soil, there is a possibility that the gas may be consumed in the thin oxidized layer close to
                       the soil surface and in deep flooding water. It is known that soil methanogenic bacteria can
                       grow with CH4 as their sole energy source, and other soil bacteria, Nitrosomonas species
                       consume CH4 (Seller and Conrad 1987). Methane is also leached to ground water as a
                       small part is dissolved in water.

                       Global emissions from rice paddies
                       The area harvested of paddy rice has increased from 86 x IO6 ha in 1935 to 144 x IO6 ha
                       in 1985, which means an annual average increase of 1.05%. The average annual increase has
                       been 1.23% between 1959 and 1985. However, in the last few years, the expansion of the
                       total acreage of paddy is decreasing. (Minami, 1993)
                       About 90% of the world's harvested area of rice paddies is located in Asia. Of the total
                       harvested area in Asia, about 60% is located in India and China. Although we had no
                       detailed data available for the estimation of CH4 flux from India and China in 1990,
                       recently some data are published for Asian countries as shown in Table 2.
  4.52

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                                                                                          AGRICULTURE
                                                         TABLE 2
                           METHANE EMISSION FROM RICE PADDY FIELDS IN VARIOUS LOCATIONS OF THE WORLD
China (Hangzhou)
Early rice
Late rice
Single rice
China (Tuzu)
India
Italy
Japan
Ryugasaki (Peat soil)
Ryugasaki (Gley soil)
Tsukuba (Andosol)
Spain
Thailand
Suphan Buri
Khlong Luang
Chai Nat
USA
California
Texas
.Louisiana

0.19
0.69
0.44
1.39
0.04-0.46
0.10-0.68

0.39
0.07-0.37

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AGRICULTURE
                                                            TABLES
                              GLOBAL ANNUAL METHANE EMISSION FROM RICE CULTIVATION AS ESTIMATED BY
                                                       DIFFERENT AUTHORS
                              Koyama (1964)
                              Ehhalc and Schmidt (1978)
                              Cicerone and Shetter (1981)
                              KhalilandRasmussen(l983)
                              Seller etal (1984)
                              Blake (1984)
                              Crutzen (1985)
                              Holzapfel-Psdiorn and Seller (1986)
                              Cicerone and Oremland (1988)
                              Schutzetal. (1989)
                              Aselman and Crutzen (1989)
                              Schutz and Seller (1989)
                              Wang etal. (1990)
                              Ncucctal. (1990)
                              Bouwman (1990)
                              YagiandMlnami(l990)
                              IPCC(I990)
                              IPCC (1992)
                              MinamiandYagi(l993)
  190
  280
  59
  95
35-59
142-190
120-200
70-170
60-170
50-150
30-75
60-140
70-170
60-120
25-60
53-114
22-73
25-170
20-100
12-113
                        4.3.2  Methods  For  Estimating  Emissions15
                        Emissions of methane from rice fields can be represented as follows:
                        FC = compXE (I)
                        where Fc is the estimated emission of methane from a country (c) in Tg/yr, comp is the
                        "composite emission factor"  (Tg/hectare/yr) representative of the conditions in a country,
                        and E is the "extrapolant" (hectare-years). The composite emission factor is evaluated
                        from direct field measurements of methane fluxes, and the extrapolant consists of the
                        product of the rice area harvested per year and the fraction of the year the fields are used
                        for growing rice: E = A (hectares) x T (years). The extrapolant is obtained from
                        geographical and agricultural archives.
                        In practice it is simpler to calculate the total annual emissions from a country as a sum of
                        the emissions  over a number of conditions. The emissions differ under each condition and

                                                     .... Ttffc...    (2)
                        lsFrom Kalil, 1993, reporting recommendations of the expert group.
 4.54

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                                                                                                AGRICULTURE
             represent the effect of the biological, chemical, and physical factors that control methane
             emissions from rice fields.
             where ijk... are categories under which methane emissions from rice fields may vary. For
             instance, i may represent water levels in the rice fields such as fields inundated for the
             duration of the growing season (flooded regime) or fields under water only intermittently,
             either from managed irrigation when water is not readily available or when rains do not
             maintain flooded conditions throughout the growing season (intermittent regime) or
             highland rice when the fields are seldom flooded during the growing season (dry regime), j
             may represent fertilization regimes under each of the conditions represented by the index
             i, and so on. As more factors are identified, more categories need to be included. Inclusion
             of additional factors does not, however, lead to  an automatic improvement of the total
             emissions since errors propagate and may create large uncertainties. Similarly, using
             extremely simplified methods for calculating the representative flux (
-------
AGRICULTURE
                       Default Methodologies

                       In many cases, especially in the beginning of the process, there will be important rice
                       growing areas for which specific fluxes or details of extrapolants will not be available. In
                       such cases the recommended methodology is to adopt the emission factors from the
                       nearest region where data are available or the most similar climatic zone from which data
                       are available. If data on irrigation practices are not available, it should be taken as the
                       flooded regime.
                       4.3.3  Summary Of  Recommended  Method

                       I    Base years:  1990 as averaged over 1989-1991.

                       2    Use:

                                Area of rice agriculture under flooded regime = A (flooded) in m  .
                                Emission factor for flooded conditions, over the three years for emissions from
                                nearby region or similar climatic zone =  (Tg/m /day).
                                Number of days under cultivation when flooded = T (days/yr)
                                Calculate Flux(flooded) = A(flooded) x ({((flooded) x T(flooded) for each of the
                                three base years and take average.
                                Correct flux for temperature effect:

                                  multiplyby  [Q10
a
b

c
d
                                where Q|Q is the ratio of the flux at temperature IO°C above the base
                                temperature.
                            f    Repeat steps a)-e) for intermittently flooded rice agriculture:
                                Flux(intermittent).
                            g    Repeat steps a)-e) for dryland rice: Flux(dry).
                            h    Average annual country flux is F(country) = Flux(flooded) + Flux(intermittent) +
                                Flux(dry).
                       3    Where data are available on fertilizer type, it may be incorporated into the
                            calculations.

                            Calculate each of the three factors in h) as follows:
                            i    Flux(flooded) = Flux(flooded|organic) + Flux(flooded|chemical)
                                where Flux(flooded|organic) is calculated according to steps a)-e) using the
                                emission factors, areas, time of flooding, and temperatures applicable to the
                                amount of rice grown under flooded conditions using organic fertilizers.
                                Flux(flooded|chemical) is calculated analogously.
                            j    Calculate Flux(intermittent) and Flux(dry) analogously to i)


                       4    Each additional factor may be incorporated in the same manner by further subdividing
                            each category in 3).

                       The procedure is described by the following general formulae:
                                             Base:   F=Z((>.A.Tt
                                                   (3)
                       i represents water management regimes - flooded, intermittent, dry.
4.56

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                                                                                             AGRICULTURE
            Adding fertilizer effecc
                                                                           (4)
            where j represents different fertilizer types. Each component if (3) is calculated by (4).

            Additional factors:  soil type, for example:
                                                      (5)
            where k represents different soil types. Each component of (4) is calculated from (5) and
            then each component of (3) is calculated from (4).

            The process may be continued for more factors.

             Default Data.

             Tables 4-6 and 4-7 present regional and country specific information regarding rice
             production and emissions.
                       In Table 4-6 the area information is based on statistics from the FAO
            Yearbook, China Agricultural Yearbook, and World Rice Statistics from IRRI. The crop
            calendars of Matthews et al. (1991) were modified to reflect the period in which a
            particular crop was grown, rather than the total possible period in which a crop can be
            grown. Using the length of the season calculated from the crop calendar leads to an
            overestimate of the methane emission season. The two exceptions to this are Louisiana,
            where two crops are being grown, and Italy, which has a longer growing season for rice
             than the crop calendars suggest. The Matthews et al. tables were the basis for estimating
             season length and then were reduced by 10 to 45 days depending on the crop calendar
             season length. In Table 4-6, "Season Length" is the weighted average of all growing seasons
             after they have been adjusted for the crop calendar length.


             Table 4-7 provides default emission factors for intermittently flooded and flooded rice fields. If
             countries have local measurements data available to develop country-specific emission
             factors, these should be used and documented. Default values in Table 4-7 can be used for
             initial calculations where local measurements are not adequate. A "modal" average seasonal
             flux for Asian countries was estimated to be 20 (+/-5) mg/m2 nr, Q10 = 1.8, with a base
             temperature of (Tb) = 23 *C. The base temperature is representative of average seasonal
             temperatures in the areas of Asia where flux measurements are available (20-25 *C). These
             flux values are representative of flooded rice fields where organic amendments are used,
             which is common in rice growing countries where measurements are not available. Dryland
             rice was assigned a flux of 0 and shallow rainfed rice was used as a proxy for intermittently
             flooded rice fields.

             Based on the work of Chen et al. (1993) and Sass et al. (1992) intermittently flooded rice was
             assumed to have a flux rate that is 60% of flooded rice fields. Currently there are no data
             readily available on intermittently flooded rice. The current estimating procedure probably
             underestimates the flux of methane from this category, since it assumes that there is one
             drought episode in every crop of shallow rainfed rice fields worldwide.
PART 2
                                                                                                                 4.57

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AGRICULTURE
TABLE 4-6
DEFAULT ACTIVITY DATA- HARVESTED RICE
Country
1990 Area
1 OOOs ha
Season Length
(days)
Continuously
Flooded
(%)
Dry
(%)
Intermittently Flooded
(%)
AMERICAS
USA
Belize
Costa Rica
Cuba
Dominican Rep
El Salvador
Guatemala
Haiti
Honduras
lamalca
Mexico
Nicaragua
Manama
Puerto Rico
Trinidad & Tobago
Argentina
Bolivia
Brazil
Chile
Columbia
•quador
Guyana
Paraguay
'era
Surinam
Jruguay
Venezuela
1114
2
S3
ISO
93
IS
IS
52
19
0
123
48
92
0
S
103
110
4450
35
453
266
68
34
185
58
108
119
123
139
103
139
103
123
139
123
123
123
130
123
103
123
103
121
101
101
121
124
100
123
101
167
123
138
103
100
10
10
100
98
10
10
40
10
40
41
10
5
75
45
100
25
18
79
53
40
95
50
84
100
100
90
0
90
90
0
2
90
90
60
90
60
59
90
95
25
55
0
75
76
21
47
10
5
SO
16
0
0
10
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
6
0
0
50
0
0
0
0
0
0
4.58

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                                                 AGRICULTURE
TABLE 4-6 (CONTINUED)
DEFAULT ACTIVITY DATA - HARVESTED RICE
Country
1990 Area
1 OOOs ha
Season Length
(days)
Continuously
Flooded
(%)
Dry
(%)
Intermittently Flooded
<*»
ASIA
Jrunei
Hong Kong
Syria
Turkey
India
Pakistan
Bangladesh
Surma
Nepal
Afghanistan
Bhutan
China
Indonesia
Iran
Iraq
Japan
Malaysia
Philippines
Sri Lanka
Taiwan
Thailand
Kampuchea
Laos
Vietnam
N Korea
S Korea
1
0
0
52
42321
103
10303
4774
1440
173
25
33265
10403
570
78
2073
2073
3413
793
700
9878
1800
625
6069
673
1237
82
123
123
123
107
103
132
139
90
103
169
115
110
103
123
123
123
98
122
119
123
134
123
119
103
103
79
100
100
too
53
100
14
42
29
100
21
93
78
100
100
96
96
54
65
97
22
34
II
65
67
91
21
0
0
0
IS
0
I*
15
4
0
is
2
IS
0
0
4
4
-12
7
3
12
27
49
7
13
1
0
0
, 0 ,
0
32
0
72
43
67
0
64
5
7
0
0
0
0
34
28
0
66
39
40
28
20
8
PART 2
4.59

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AGRICULTURE
TABLE 4-6 (CONTINUED)
DEFAULT ACTIVITY DATA - HARVESTED RICE
Country
1990 Area
1 OOOs ha
Season Length
(days)
Continuously
Flooded
(%)
Dry
(%)
EUROPE
Albania
Bulgaria
'ranee
Greece
•lungary
Italy
'ortugal
Romania
Spain
winer USSR
tanner Yugoslavia
2
II
20
15
II
208
33
37
81
624
8
123
103
139
103
123
102
123
123
103
103
123
100
100
100
100
100
100
100
100
100
100
100
0
0
0
0
0
0
0
0
0
0
0
Intermittently Flooded
(%)

0
0
0
0
0
0
0
0
0
0
0
PACIFIC
Australia
Rji
Solomon Islands
"apua/New Guinea
97
13
0
0
128
81
102
102
100
50
38
38
0
0
0
0
0
0
0
0
AFRICA
Algeria
Angola
Jenin
iurklna Faso
Surundi
Cameroon
C African Rep
Chad
Comoros
Congo
Egypt
Gabon
Gambia
Ghana
Guinea Bissau
Guinea
Ivory Coast
Kenya
Liberia
Madagascar
1
18
7
19
12
15
10
39
13
4
427
0
14
85
57
608
583
15
168
1135
138
121
123
123
167
103
123
123
100
121
123
121
123
139
123
123
123
139
123
167
100
100
10
89
25
25
25
25
100
25
100
25
90
24
25
8
6
25
0
35
0
0
90
II
75
75
75
75
0
75
0
75
10
76
75
47
87
75
94
19
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
45
7
0
6
46
4.60

-------
4
AGRICULTURE
TABLE 4-6 (CONTINUED)
DEFAULT ACTIVITY DATA- HARVESTED RICE
Country
Malawi
Mali
Mauritania
Morocco
Mozambique
Niger
Nigeria
Rwanda
Senegal
Sierra Leone
Somalia
South Africa
Sudan
Swaziland
Tanzania
Togo
Uganda
Zaire
Zambia
Zimbabwe
1990 Area
1 OOOs ha
29
222
14
6
109
29
1567
3
73
339
5
1
1
0
375
21
37
393
II
0
Season Length
(days)
137
123
123
138
121
102
103
167
103
139
103
167
103
167
137
139
137
101
121
121
Continuously
Flooded
(%)
25
25
100
100
25
35
28
25
25
1
50
100
50
25
10
4
25
5
25
25
Dry
(%)
75
75
0
0
75
65
55
75
75
67
SO
0
SO
75
26
96
75
90
75
75
Intermittently Flooded
(%)
0
0
0
0
0
0
17
0
0
32
0
0
0
0
64
0
0
5
0
0
          Source: Khalil (1993), personal communication.
 PART 2
             4.61

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AGRICULTURE
TABLE 4-7
SEASONAL AVERAGE EMISSION FACTORS CORRECTEDFOR AVERAGE TEMPERATURE
Growing Season
Average Temperature
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
Emission Factor
kg/ha/day
Continuously Flooded
2.91
3.09
3.28
3.48
3.68
3.91
4.14
4.39
4.66
4.94
5.24
5.56
5.90
6.25
6.63
7.03
7.46
7.91
8.39
8.90
9.44
Intermittently Flooded
1.75
1.85
1.97
2.09
2.21
2.34
2.94
2.64
2.80
2.97
3.15
3.34
3.54
3.75
3.98
4.22
4.48
4.75
5.03
5.34
5.66
                 Source: Khalil (1993), personal communication
 4.62

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                                                                                             AGRICULTURE
             4.3.4  References

             Aselmann, I. and P.J. Crutzen 1989: The global distribution of natural freshwater wetlands
             and rice paddies, their net primary productivity, seasonality and possible methane
             emission. J. Atm. Chem., 8, 307-358.

             Bingemer, H.G. and P.J. Crutzen 1987: The production of methane from solid wastes. J.
             Geophys. Res., 92(D), 2181-2187.
             Blake, D.R. and F.S. Rowland 1988: Continuing worldwide increase in tropospheric
             methane,  1978 to 1987. Science, 239,  1129-1131.
             Bouwman, A.F. 1990: Exchange of greenhouse gases between terrestrial ecosystems and
             the atmosphere. Ed. A.F. Bouwman, In Soil and the greenhouse Effect. John Wiley and
             Sons, 62-127.
             Bremner, J.M.  and A.M. Blackmer 1982: Composition of soil atmospheres, In Methods of
             soil analysis, Part 2, Chemical and Microbiological Properties, Agronomy Monograph No.
             9,873-901.
             Chen, Z., D. Li, K.  Shao, and B. Wang  1983: Features of CH4 emission from rice paddy
             fields in Beijing and Nanjing, China. Chemosphere, 26( I -4):239-246.
             China Agricultural  Yearbook, 1990. Agribookstore, Hampton, VA.
             Cicerone, R.J., J.D. Shetter and C.C. Delwiche 1983: Seasonal variation  of methane flux
             from a California rice paddy. J. Geophys. Res., 88, 7203-7209.
             Cicerone, R.J.  and R.S. Oremland 1988: Biogeochemical aspects of atmospheric methane.
             Global Biogeochem. Cycles, 2, 299-327.
             Conrad, R.  1989: Control of methane  production in terrestrial ecosystems, In Exchange of
             Trace Gases between Terrestrial Ecosystems and the Atmosphere, eds. M.O. Andreae and
             D.S. Schimel, 39-58.
             Ehhalt, D.H. and U. Schmidt 1978: Sources and sinks  of atmospheric methane. Pure Appl.
             Geophys., .16,452-464.
             Graedel, T.E. and J.E. McRae 1980: On the possible increase of the atmospheric methane
             and carbon  monoxide concentrations during the last decade. Geophys.  Res. Lett, 7,977-
             979.
             Grist, D.H.  1986: Rice. Longman, Inc.,  New York, U.S.A. 6th edition.
             Holzapfel-Pschorn, A., R. Conrad, and W. Seller 1985: Production, oxidation, and emission
             of methane  in  rice  paddies. FEMS Microbiology Ecology, 31, 343-351.
             Holzapfel-Pschorn, A., and W. Seller 1986: Methane emission during a cultivation period
             from an Italian rice paddy. J. Geophys. Res., 91, 11803-1181.4.
             Huke, R.F. 1982: Rice area by type of culture; south, southeast and east Asia. International
             Rice Research Inst, IRRI, Los Banos, Los Banos, Philippines.
             IRRI, 1991: World Rice Statistics 1990. International Rice Research Inst., Los Banos,
             Laguna, Philippines.
             Khalil, M.A.K.  1993: Working Group Report: Methane Emissions from  Rice Fields. In A.R.
             van Amstel  (ed.), Proceeding of an International IPCC Workshop on Methane and Nitrous
             Oxide: Methods in National Emissions Inventories and Options for Control. RIVM Report
             no. 481507003, Bilthoven, The Netherlands, pp. 239-244.
PART 2
4.63

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                       Khalil, MAK., RA Rasmussen, M.X. Wang, and LRen 1991: Methane emission from rice
                       fields in China; Environ. Sci. Tech., 25:979-981.

                       Lai, S., S. Venkataramani, and B.H. Subbaraya 1993: Methane flux measurements from
                       paddy fields in the tropical Indian region; Atmos. Environ., 27A:I69I-I694.

                       Undau, C.W., and P.K. Bollich  1993: Methane emissions from Louisiana first and ratoon
                       rice crop; Soil Science, 156:42-48.
                       Matthews, E., I. Fung, and J. Lerner  1991: Methane emission from rice cultivation;
                       Geographic and seasonal distribution of cultivated areas and emissions. Global
                       Biogeochem. Cycles, 5, 3-24.
                       Minami, K. 1993: Methane Emissions from Rice Production. In A.R. van Amstel (ed.),
                       Proceeding of an International IPCC Workshop on Methane and Nitrous Oxide: Methods
                       in National Emissions Inventories and Options for Control. RIVM Report no. 481507003,
                       Bilthoven, The Netherlands, pp.  143-162.
                       Minami, K., and K. Yagi 1988: Method for measuring methane flux from rice paddies. Jpn. J.
                       Soil Sci. Plant Nutr., 59, 458-463 (in Japanese).

                       Minami, K., K. Kumagai, K. Yagi, and H. Tsuruta 1992: unpublished.
                       Neue, H.U., P. Becker-Heidmann and H.W. Scharpenseel. 1990: Organic matter dynamics,
                       soil properties and cultural practices in rice lands and their relationship to methane
                       production. Ed. A.F. Bouwman, In Soils and the Greenhouse Effect. John Wiley and Sons,
                       457-466
                       Nouchi, I., S. Mariko, and K. Aoki 1990: Mechanisms  of methane transport from the
                       rhizosphere to the atmosphere through  rice plant. Plant physiology, 94, 59-66.
                       Nozaki, M. 1989: Rice cultivation in Tropical Africa. Trop. Agr. Rec. Center. (In Japanese).

                       Patrick, W.H. Jr. 1981: The role  of inorganic redox systems in controlling reduction in
                       paddy soils. In Proc. Symp. Paddy Soil, 107-117, Science Press, Beijing, Spring Verlag.

                       Ponnamperuma, F.N. 1972: The  chemistry of submerged soils, Adv. Agron., 24, 29-69.

                       Rasmussen, RA, and MAK. Khalil 1981: Increase in  the concentration of atmospheric
                       methane. Atmos. Environ., 15,883-886.
                       Rasmussen. RA., and M.A.K. Khalil 1984: Atmospheric methane in the recent and ancient
                       atmospheres: concentrations,  trends, and interhemispheric gradient J. Geophys. Res.,
                       89(D),  11599-11605.
                        Rowland, F.S. 1991: Stratospheric ozone in the 21st century, The chlorofluorocarbon
                        problem, Environ. Sci. Technol.,  25, 622-628.
                        Sass, R.L, F.M. Fisher, P.A. Harcombe, and FT. Turner 1991 a: Mitigation of methane
                        emissions from rice fields: possible adverse effects of incorporated rice straw. Global
                        Biogeochemical Cycles, 5(3): 275-287.
                        Sass, R.L, F.M. Fisher. Y.B. Yang, FT. Turner, and M.F. Jund 1992: Methane emissions  from
                        rice fields: the effect of flood water management Global Biogeochemical Cycles, 6(3): 249-
                        262.
                        Seller, W., A. Holzapfel-Pschorn, R. Conrad, and D. Scharffe 1984: Methane emissions
                        from rice paddies. J. Atmos. Chem., I, 241-268.

                        Seller, W., and R. Conrad 1987: Contribution of tropical ecosystems to the global budgets
                        of trace gases, especially CH4, H2, CO and N2O, In  R.E. Dickinson (Ed.), Geophysiology
                        of Amazonia. Vegetation and Climate Interactions, 133-160, Wiley and Sons, New York.
 4.64

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                                                                                              AGRICULTURE
             Sheppard, J.C., H. Westberg, J.F. Hopper, K. Ganesan, and IP. Zimmerman 1982: Inventory
             of global methane sources and their production rates.]. Geophys. Res., 87(C), 1305-1312.

             Schutz, H., A. Holzapfel-Pschorn, R. Conrad, H. Rennenberg, and W. Seller 1989: A 3-year
             continuous record on the influence of daytime, season, and! fertilizer treatment on
             methane emission rates from an Italian rice paddy. J. Geophys. Res., 94, 16405-16416.

             Steele, L.P., E.J. Dlugokencky, P.M. Lang, P.P. Tans, R.C. Maitin, and K.A. Masarie 1992:
             Slowing down of the global accumulation of atmospheric methane during the 1980s.
             Nature, 358, 313-316.

             Takai, Y., T. Koyama, and T. Kamura 1956: Microbial metabolism in reduction process of
             paddy soils (Part I), Soil & Plant Food, 2, 63-66.

             Takai, Y. 1970: The mechnism of methane fermentation in Hooded paddy soil. Soil Sci.
             Plant Nutr., 16,238-244.

             Takai, Y. 1980: Microbial study on the behavior of the paddy soils. Pert. Sci., 3, 17-55 (in
             Japanese).

             Thompson, A.M., and R.J. Cicerone 1986: Possible perturbations to atmospheric CO, CH4
             and OH. J. Geophys. Res., 91 (D), 10858-10864.
             United Nations,  1992: FAO Production Yearbook, vol. 46. Food and Agriculture
             Organization of the United Nations, Rome.
             Wang, W.C., Y.L Yung, A.A. Lacis, J.E. Mo, and J.E. Hansen 1976: Greenhouse effects due
             to man-made perturbations of trace gases. Science, 194, 685-690.
             Wassman, R., H. Schutz, H. Papen, H. Rennenberg, W. Seiler, A. Dai, R. Shen, X.
             Shangguan, and M. Wang.  1993: Quantification of methane emissions from Chinese rice
             fields (Zhejiang Province) as influenced by fertilizer treatment. Biogeochemistry, 20:83-101.
             Watson, R.T., H. Rodhe, H. Oeschger, and  U. Siegenthaler 1990: Greenhouse gases and
             aerosol, In Climate Change, the IPCC scientific assessment, ed. j.T. Houghton et at., 1-40.
             Watson, R.T., LG. Meira Filho, E. Sanhueza, and A. Janetos 1992: Greenhouse gases:
             Sources and Sinks, In Climate Change 1992, The Supplementary Reports to The IPCC
             Scientific Assessment, eds. J.T. Houghton, B.A. Callander, and S.K. Varney, 25-46.
             Yagi, K., and K. Minami 1990: Effect of organic matter application on methane emission
             from some Japanese paddy fields. Soil Sci. Plant Nutr., 36, 599-610.
             Yagi, K., and K. Minami 1990: Estimation of global methane emission from paddy fields.
             Res. Rep. Div. Environ. Planning, NIAES, 6,  131-142 (in Japanese).
             Yagi, K., K. Minami, and Y. Ogawa 1990: Effects of water percolation on methane emission
             from paddy fields, NIAES, Res. Rep. Div. Environ. Planning, 6,  105-112 (1990).
             Yagi, K., and K. Minami 1991: Emission and production on methane in the paddy fields of
             Japan, JARQ, 25, 165-171.

             Yagi, K., and K. Minami 1993: Spatial and temporal variations of methane flux from a rice
             paddy field. In The Biogeochemistry of Global Change; Radiative Trace Gases, R.S.
             Oremland (ed.), Chapman & Hall, New York, in press.
             Yagi, K., H. Tsuruta, and K. Minami 1992: Methane emission from Japanese and Thai paddy
             fields. CH4 and N2O Workshop, Tsukuba, in press.
             Yamane, I., and K. Sato 1961: Effect of temperature on the formation of gases and
             ammonium nitrogen in the water-logged soils. Sci. Rep. Res. Inst. Tohoku Univ. D(Agr.),
              12,31-46.
PART 2
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                      Yamane, I., and K. Sato 1963: Decomposition of plant constituents and gas formation in
                      flooded soil. Soil Sci. Plant Nutr., 9, 28-31.
                      Yamane. I., and K. Sato 1964: Decomposition of glucose and gas formation in flooded soil,
                      Soil Sci. Plant Nutr., 10, 127-133.
                      Yoshida, T. 1978: Microbial metabolism in rice soils. In Soils and Rice, ln«. Rice Res. Inst,
                      445-463.
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                                                                                               AGRICULTURE
     4.4    Agricultural  Burning
              4.4.1  Introduction

              Where there is open burning associated with agricultural practices, a number of
              greenhouse gases (GHG) are emitted from combustion. All burning of biomass produces
              substantial CO2 emissions. However, in agricultural burning, the CO2 released is not
              considered to be net emission. The biomass burned is generally replaced by regrowth
              over the subsequent year. An equivalent amount of carbon is removed from the
              atmosphere during this regrowth, to offset the total carbon released from combustion.
              Therefore the long term net emissions of CO2 are considered to be zero. Agricultural
              burning releases other gases in addition to CO2 which are by-products of incomplete
              combustion: methane, carbon monoxide, nitrous oxide, and oxides of nitrogen, among
              others. These non-CO2 trace gas emissions from biomass burning are net transfers from
              the biosphere to the atmosphere. It is important to estimate the emissions in national
              inventories.

              There are two major types of agricultural burning addressed in this section — savanna
              burning and field burning of crop residues. The approach is essentially the same as that
              used for non-CO2 trace gases for all burning of unprocessed biomass, including traditional
              biomass fuels and open burning of cleared forests. For all these activities, there is a
              common approach in the proposed methodology, in that crude estimates of non-CO2
              trace gas emissions can be based on ratios to the total carbon released. The carbon trace
              gas releases (CH4 and CO) are treated as direct ratios to total carbon released. To handle
              nitrogen trace gases, nitrogen to carbon ratios are used to derive total nitrogen released
              and then emissions of N2O and NOX are estimated based on ratios of these gases to total
              nitrogen released. Tables B and C provide suggested default values for non-CO2 trace gas
              emission ratios. These are presented with ranges, which emphasize their uncertainty.
              However, the basic calculation methodology requires that users select a best estimate
              value.2

              The calculation of immediate trace gas emissions, based on the default emission ratios
              provided in Tables B and C, produces relatively crude estimates with substantial
              uncertainties.  Use of specific emission ratios which vary by 'type of burning, region, etc.
              may allow for more precise calculations. The calculations described here ignore the
              contemporary fluxes associated with past burning activities. These delayed releases are
              known to exist, but are poorly understood at present. This and other possible
              refinements are discussed at the end of this section.
              4.4.2  Prescribed  Burning: Savannas

              Background

              The term savanna refers to tropical and subtropical vegetation formations with a
              predominantly continuous grass cover, occasionally interrupted by trees and shrubs.4
              These formations exist in Africa, Latin America, Asia, and Australia. The growth of
              vegetation in savannas is controlled by alternating wet and dry seasons:  most of the
              growth occurs during the wet season; man-made and/or natural fires are frequent and
              generally occur during the dry season. The global area of sava.nnas is uncertain, in part due
              to lack of data and in part due to differing ecosystem classifications. Estimates of the areal
              extent of savannas range from 1300-1900 million hectares worldwide, about 60% of which
PART 2
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AGRICULTURE
                        are humid savannas (annual rainfall of 700 mm or more) and 40% are arid savannas (annual
                        rainfall of less than 700 mm).5 Large-scale burning takes place primarily in the humid
                        savannas because the arid savannas lack a sufficient grass cover to sustain fire. Humid
                        savannas are burned every one to four years on average with the highest frequency in the
                        humid savannas of Africa.
                        Savannas are intentionally burned during the dry season primarily for agricultural purposes
                        such as ridding the grassland of weeds and pests, promoting nutrient cycling, and
                        encouraging growth of new grasses for animal grazing. Savanna burning may be
                        distinguished from other biomass burning activities like open forest clearing because there
                        is little net change in the ecosystem biomass in the savanna after the vegetation regrows
                        during the wet season. Consequently, while savanna burning results in instantaneous gross
                        emissions of CO2, it is reasonable to assume that the net carbon dioxide released to the
                        atmosphere is essentially zero because the vegetation typically regrows between burning
                        cycles.  Savanna burning does release several other important trace gases: methane (CH4),
                        carbon monoxide (CO), nitrous oxide (N2O), and oxides of nitrogen (NOX, i.e., NO +
                        NO,).
                        Estimates of global emissions of these gases due to savanna burning have been based on
                        estimates of the annual instantaneous gross release of carbon from this activity and  ratios
                        of the other trace gases released from burning to total carbon released by burning.
                        Estimates of the annual instantaneous gross release of carbon from savanna burning are
                        highly uncertain because of lack of data on the aboveground biomass density of different
                        savannas, the savanna area burned annually, the fraction of aboveground biomass which
                        actually burns, and the fractions which oxidizes (i.e., combustion efficiency). The
                        methodology that is proposed in the next section although conceptually quite simple,
                        takes these factors  into account. The approach allows for estimation of non-CO2 trace
                        gases released by savanna burning based on default data sets and assumptions from  average
                         literature values for various regions and types of savannas. It also allows for more accurate
                         national estimates if data and assumptions can be developed to reflect national average
                         conditions accurately. Nonetheless, a wide variety of technical details and open scientific
                         issues remain important research topics.

                         Calculations
                         There are two basic components to the calculation. First, it is necessary to estimate the
                         total amount of carbon released to the atmosphere from savanna burning. These are not
                         considered net emissions, but are needed to derive non-CO2 trace gas emissions which
                         are net emissions. What is required is the annual area burned for the various types of
                         savannas, where type is based primarily upon above and below ground biomass, and
                         perhaps climatological conditions and nutrient status.  If data are not directly available,
                         estimates can be derived based on total savanna area8 and average percentages of savanna
                         burned annually, as shown in Table A. Based on the area and type of savanna burned, the
                         amount of carbon released can be calculated (a reflection of biomass densities, fractions
                         burned, carbon contents and combustion efficiencies). The second component of the
                         calculation is the same as for other biomass burning categories -- emission  ratios are
                         applied to estimate the amount of trace gas released based on the amount of carbon
                          released (Table B provides default emission ratios).
                         The approach formally recognizes that countries generally possess more than one savanna
                          type, each with different characteristics, such as vegetative cover, that would affect trace
                          gas emissions from burning. Also, the savanna area within a country may not be burned all
                          at once, but rather in stages over the course of the dry season. Since the amount and
                          nature (e.g., moisture content) of the vegetation changes during the year, factors such as
                          biomass exposed to burning and burning efficiency will vary among the savanna areas
  4.68

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                                                                                                AGRICULTURE
              burned at different times. The data requested by this methodology focus upon country-
              specific types of savannas and the country-specific rate of burning for each type.

              It is also recognized that national and regional estimates of the percent of savanna area
              burned annually are highly uncertain. An example selection of regional estimates is
              included in Table A. Though regional variability is great, the methodology, by focusing upon
              a simple classification of savanna type and the burning by type, can be implemented using
              data that are available to most countries. The methodology is intended to be flexible to
              allow users to define the savanna types and/or geographic subregions for calculations.
              National experts are encouraged to carry out the calculations at the finest levels of detail
              for which credible data can be obtained. Finally, by varying che rate and/or type of savannas
              burned, national experts can easily test to  the sensitivity of the  calculated emissions to
              the uncertainties in the data.

              Part I: Total Carbon Released From Savanna Burning

              In order to calculate the carbon released to the atmosphere from savanna burning, these
              data are required:
              •    Area of savanna;
              •    Fraction of savanna area burned annually;
              •    Average aboveground biomass density (tonnes dry matter/hectare) of savannas;

              •    Fraction of aboveground biomass which actually burns;
              •    Fraction of aboveground biomass that is living;
              •    Fraction of living and of dead aboveground biomass oxidized, (i.e., combustion
                   efficiency of living and dead biomass); and
              •    Fraction of carbon in living and dead biomass.
              Not all of these data must be provided by the user. Initially one  could pool the living and
              dead biomass if data are not available. More importantly, Table A provides much of the
              basic default data that only need to be refined for country-specific relevance. Given the
              data, the steps to calculate emissions are not overly difficult One simply calculates from
              the area burned the total carbon released based upon the factors listed above. In addition
              to the data in Table A, other recommended  default values are included in the step-by-step
              discussion below.
              The following equations summarize the calculations to estimate the total carbon released
              due to the burning of savannas:
                                                 EQUATION I
                                    Area of Savanna Burned Annually (ha)


                                Total Area of Savanna (ha) x Fraction Burned Annually
PART  2
                                                                                                                   4.69

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AGRICULTURE
                                                         EQUATION 2
                                                   Biomass Burned (t dm)


                               Area of Savanna Burned Annually (ha) x Aboveground Biomass Density (t
                                                dm/ha) x Fraction Actually Burned
                                                         EQUATION 3
                                             Carbon Released from Live Biomass (t C)
                                Biomass Burned (t dm) x Fraction that is Live x Combustion Efficiency x
                                            Carbon Content of Live Biomass (t C/t dm)
                                                          EQUATION 4
                                             Carbon Released from DeadBiomass (t C)
                               Biomass Burned (t dm) x Fraction that is Dead x Combustion Efficiency x
                                            Carbon Content of Dead Biomass (t C/t dm)
                                                          EQUATION 5
                                                   Total Carbon Released (t C)


                              C Released from Live Material (t C) + C Released from Dead Material (t C)
                        In the first equation, the savanna area in the country is multiplied by the percentage of the
                        savanna area that is burned annually, if statistics on area burned annually are not directly
                        available. If national experts have data on the area burned annually they should use this and
                        begin with equation 2. In the second, area burned is multiplied by aboveground dry
                        biomass per hectare (ha) on the savanna at the time of burning and the fraction of biomass
                        which actually burns. Regional estimates of rates of savanna burning and biomass densities
                        are presented in Table A. The fraction actually burned accounts for the fact that when
                        savannas are burned, not all of the biomass on each hectare is actually exposed to flame. If
                        detailed information is not available, a general default value in the range of 0.8-0.85 is
                        recommended.
                        The aboveground biomass density before burning is a function of the type of savanna being
                        burned and the time of year in which burning occurs.1  The values for West African
                        savannas provided in Table A correspond to mid-season fires, except for  those of the
                        Sahel where burning occurs early. If statistics on maximum biomass density and fraction of
                        maximum biomass density present at the time of burning are not available, countries can
                        use an average biomass density instead. According to this analysis, average savanna biomass
                        densities are lowest in tropical Asia, at about 5 tons per hectare (t/ha),1  average around
                        6.6 t/ha in tropical Africa and tropical America,14 and range between  2 and 6 t/ha in
                        Australia.15 These estimates have an uncertainty of ±30% based on field measurements.16
 4.70

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                                                                                              AGRICULTURE
            As mentioned, these regional average densities are presented in Table A and can be used
            as default values if average biomass density for a specific country or savanna type is not
            known.
            In the third and fourth equations, the living and the dead portions of aboveground biomass
            burned are multiplied by their respective combustion efficiencies and carbon contents.
            Estimates of the fraction of aboveground biomass that is living for West African savannas
            range from 20 to 55% (Table A). Data suggest that the live portion burns with a
            combustion efficiency that ranges between 65 and 95% and the dead portion with
            essentially 100% efficiency.17 If combustion efficiencies are not available, 80% and 100% for
            the living and dead portions, respectively, can be used. If country or ecosystem values are
            not available, then the values 0.45 t C/t dry biomass and 0.40 t C/t dry biomass can be
            used as default values for the carbon contents of the living and dead portions,
                   .  , 18
            respectively  .
            The total carbon released from savanna burning (Equation 5) is estimated by summing the
            carbon released from the living and the dead biomass fractions, calculated in Equations 3
            and 4.

            Part 2: Non-CO2 Trace Gas Emissions
            Once the carbon released from savanna burning has been estimated, the emissions of CH4,
            CO, N2O, and NOX can be calculated using emission ratios. (Default values are presented
            in Table B.)19 The amount of carbon released due to burning is multiplied by the emission
            ratios of CH4 and CO relative to total carbon released to yield emissions of CH4 and CO
            (each expressed in  units of C). The emissions of CH4 and CO are multiplied by 16/12 and
            28/12, respectively, to convert to full molecular weights.
            To calculate emissions of N2O and NOX, first the carbon  released is  multiplied by the
            estimated ratio of nitrogen to carbon (N/C ratio) in savanna biomass by weight (0.006 is a
            general default value for savanna biomass burning ). This yields the total amount of
             nitrogen (N) released from the biomass burned. The total N released is then multiplied by
             the ratios of emissions of N2O and  NOX relative to the N released to yield emissions of
             N2O and NOX (expressed in  units of N). To convert to full molecular weights, the
             emissions of N2O and NOX are multiplied by 44/28 and 30/14, respectively.
             The non-CO2 trace gas emissions calculations from burning are summarized as follows:

                  CH4 Emissions = (carbon released) x (emission ratio)  x 16/12
                  CO  Emissions = (carbon released) x (emission ratio)  x 28/12
                  N2O Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 44/28
                  NOX Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 30/14
PART 2
                                                                                                                  4.71

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AGRICULTURE
TABLE A
REGIONAL SAVANNA STATISTICS
Region
Tropical America
Tropical Asia
Tropical Africa
Sahel zone
North Sudan zone
South Sudan zone
Guinea zone
Australia
Fraction of
Area Burnt
Annually to
Total Savanna
0.50
0.50
0.75
0.05-0. 15a
0.25-0.50a
0.25-0.50a
0.60-0.80a
5-70
Aboveground
Biomass Density
(t dm/ha)
6.6 ±1.8
4.9
6.611.6
0.5-2.S3
2-4a
3-6a
4-8a
2.1-6
Fraction of
Biomass
Actually
Burned



0.95
0.85
0.85
0.9-1.0

Fraction of
Aboveground
Biomass that is
Living



0.20
0.45
0.45
0.55

                           Sources: Hao et al., 1990, except where noted. These figures are growing season average biomass values, considered
                           most appropriate for general default values

                           a Menaut et al. (1991) These figures are maximum biomass values. For these arid sub-regions, maximums are
                           considered the most appropriate default values.

                           Note: Biomass density is in tonnes of dry matter (dm) per hectare (ha).
                                                                   TABLE B
                                           EMISSION RATIOS FOR SAVANNA BURNING CALCULATIONS
Compound
ov
CO '
N203
NOX3

0.004
0.06
0.007
0.121
Ratios
(0.002 - 0.006)
(0.04 - 0.08)
(6.005 - 0.009)
(0.094-0.148)
                                           Sources: '  Delmas, 1993

                                           2 Lacaux, et al., 1993

                                           3 Crutzen and Andreae, 1990

                                           Note: Ratios for carbon compounds, i.e., CH4 and CO, are mass of
                                           carbon compound released (in units of C) relative to mass of total
                                           carbon released from burning (in units of C); those for the nitrogen
                                           compounds are expressed as the ratios of emission relative to total
                                           nitrogen released from the fuel.
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                                                                                            AGRICULTURE
            4.4.3  Prescribed  Burning:  Agricultural Crop
            Wastes

            Background
            Large quantities of agricultural wastes are produced, from farming systems worldwide, in
            the form of crop residue.22 Burning of crop residues, like the burning of savannas, is not
            thought to be a net source of carbon dioxide (COj) because the carbon released to the
            atmosphere during burning is reabsorbed during the next growing season. However, crop
            residue burning is a significant net source of CH4, CO, NOX, and N2O. This section
            accounts for emissions of these non-CO2 gases from field burning of agricultural crop
            residues (Burning of agricultural crop residues as an energy source is covered in the Energy
            chapter, in the section entitled Traditional Biomass Fuels).
            The amount of agricultural wastes produced varies by country, crop, and management ^
            system. Cereal crops  produce  between 0.6 and 2.5 tonnes of straw per tonne of grain.
            For example, wetland rice cultivated under a moderate level of management in the
            Philippines was found to produce between 0.6 and 0.9 tonnes of straw per tonne of
            grain.  Approximately 3.1 billion tonnes of crop residue are produced each year^with
            about 60%  originating in the developing world, and 40% in the developed world.
            Burning of agricultural wastes in the fields is a common practice in the developing world. It
            is used primarily to clear remaining straw and stubble after harvest and to prepare the
            field for the next cropping cycle. In Southeast Asia, burning is the major disposal method
            for rice straw,26 which accounts for about 31% of the agricultural waste in the developing
            world. Sugar cane residues, which make up about 11% of the world's agricultural waste.
            are primarily disposed of by burning.27 It has been estimated that as much as 40% of the
            residues produced in developing countries may be burned in fields, while the percentage is
            lower in developed countries.  Estimates suggest that approximately 425 Tg dry matter
            agricultural wastes (-200 Tg C) are burned in the fields in developing countries and that
            about one-tenth as much is burned in  developed countries.

            Calculations
            The methodology for estimating greenhouse gas emissions from burning of agricultural
            wastes is based, as in savanna  burning, on I) total carbon released, which is a function of
            the amount and efficiency of biomass burned, the carbon content of the biomass, and 2)
            the application of emission ratios of CH4 and CO to total carbon released, and Np and
             NOX to total nitrogen released from biomass fires which lire available from the scientific
             literature on biomass burning. Default values are provided in Table C.

             Part I: Total Carbon Released from Burning Agricultural Residues
             Data required, for each crop type, to  calculate the amount of carbon burned in agricultural
             wastes are listed  below:
             •    Amount of crops produced with residues that are commonly burned,

             •    Ratio of residue to crop product
             •    Fraction of residue burned
             •    Dry matter content of residue
             •   Fraction oxidized in burning (combustion efficiency

             •   Carbon content of the residue
PART 2
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 AGRICULTURE
                        There are standard default or literature values available for many of these data. Table D
                        provides a summary of available default data. The most important data for users to provide
                        are the actual amount of crops produced (by type) with residues that are commonly
                        burned. Annual crop production statistics by country for most of the crops from which
                        residues are burned may be found in the FAO Production Yearbooks.30 Crop-specific data
                        for each country on ratios of residue to crop, fraction of residue burned, dry matter
                        content of residue, and carbon content of residue can be incorporated at any time to
                        replace the default values. The essential data needed from the countries are the actual
                        amount of crops with residues that are commonly burned. A potentially very valuable data
                        source is the recent study the BUN/UNCED study by Professor D. Hall (and others) of
                        Kings College, London.

                        From production data one can estimate the actual material (in carbon units) that is
                        burned. One simple procedure is shown below:
                                                      Total carbon released =
                                   annual production data (tonnes of biomass per year) for each crop,
                                           x the ratio of residue to crop product (fraction),
                                   x the average dry matter fraction (tonnes of dry matter / tonnes of
                                                             biomass),
                                              x the fraction actually burned in the field,
                                                x the combustion efficiency (fraction),
                                     x the carbon fraction (tonnes of carbon / tonnes dry matter)
                        It is highly desirable to use country specific data for these values wherever possible.
                        Example estimates of residue/crop product ratios, average dry matter fraction and carbon
                        fraction for certain crops are presented in Table D.32  If no other data are available, the
                        following assumptions regarding the percentage of crop residue burned in the field can be
                        used as very crude default factors: for developing countries 0.25, and for developed
                        countries a much smaller share possibly 0.10 or less.33 A default value of 0.90 can be used
                        to account for the approximate 10% of the carbon that remains on the ground
                        (combustion efficiency).34

                        Part 2: Non-CO2 Trace Gas Emissions

                        Once the carbon released from field burning of agricultural resides has been estimated, the
                        emissions of CH4, CO, N2O, and NOX can be calculated based on  emission  ratios (default
                        values are provided in Table C).35 The amount of carbon released due to burning is
                        multiplied by the emission ratios of CH4 and CO relative to total carbon to yield
                        emissions of CH4 and CO (each expressed in units of C).  The emissions of CH4 and CO
                        are multiplied  by 16112 and 28/12, respectively, to convert to full molecular weights.

                        To calculate emissions of N2O and NOX, first the total carbon released is multiplied by the
                        estimated N/C ratio of the fuel by weight to yield the total amount of nitrogen (N)
                        released. Some crop specific values are given in Table D and 0.015  is a general default
                        value for crop residues.36 The total  N released is then multiplied by the ratios of
                        emissions of N2O and NOX relative to the N content of the fuel to yield emissions of N2O
                        and NOX (expressed in units of N). To convert to full molecular weights, the emissions of
                        N2O and NOX are multiplied by 44/28 and 30/14, respectively.37
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                                                                                                    AGRICULTURE
              The calculation for trace gas emissions from burning is summarized as follows:
                   CH4 Emissions = Carbon Released x (emission ratio) x 16/12
                   CO  Emissions = Carbon Released x (emission ratio) x 28/12
                   N2O Emissions = Carbon Released x (N/C ratio) x (emission ratio) x 44/28
                   NOX Emissions = Carbon Released x (N/C ratio) x (emission ratio) x 30/14
                                                     TABLE C
                                EMISSION RATIOS FOR AGRICULTURAL RESIDUE BURNING
                                                  CALCULATIONS
                                    Compound
                                                                       Ratios
                                      CH4'
                                      CO2
                                      NjO3
                                      NOX3
0.005 Range 0.003 - 0.007
 0.06 Range 0.04 - 0.08
0.007 IHange O.OOS - 0.009
0.121 Range 0.094-O.M8
                         Sources:
                         1 Delmas, 1993
                         2 Lacaux, et al.. 1993
                          Crutzen and Andreae. 1990
                         Note: Ratios for carbon compounds, i.e., CH4 and CO, are mass of carbon compound released
                         (in units of C) relative to mass of total carbon released from burning (in units of C); those for the
                         nitrogen compounds are expressed as the ratios of emission relative to total nitrogen released
                         from the fuel.
TABLE D
SELECTED CROP RESIDUE STATISTICS
Product
Residue/Crop Product
Dry Matter Content Carbon Content
(%) (%dm)
Nitrogen-Carbon
(N/C) Ratio

Wheat
Barley
Maize
Oats
Rye
Rice
Millet
Sorghum
1.3
1.2
1
1.3
1.6
1.4
1.4
1.4
78-88 48.53
78-88 45.67
30-50 47.09


78-88 41.44


0.012

0.02


0.014
0.0)6
0.02
Pulse
Pea
Bean
Soya
Potatoes
Feedbeet
Sugarbeet
Jerusalem artichoke
Peanut
1.5
2.1
2.1
0.4
0.3
0.2
0.8
1



30-60 42.26
10-20 ' 40.72'
10-20 ' 40.72'




0.05





Sources: Strehler and Stutzle, 1 987
Sugarbeet data from Ryan and Openshaw, 1991
Nitrogen content from Barnard and Kristoferson, 1 985
Note: ' These statistics are for beet leaves.
PART  2
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                        Possible refinements of the basic calculations

                        The basic calculations presented above address the immediate release of non-CO2 trace
                        gases when savannas or crops are burned. This is believed to be the most important effect
                        of biomass burning on GHG emissions and the best characterized at present. However,
                        there are other issues not treated in these calculations. The effect of past burning on
                        current emissions is one such issue. The longer-term release or uptake of these gases
                        following burning is an important research issue and may eventually be included in
                        refinements of the calculations. In particular, grassland fires (savanna burning) may perturb
                        the soils sufficiently to release additional N2O and NOX. Little is known about the
                        magnitude of this flux so these emissions may not be included in the first application of the
                        methodology. It is less likely that such delayed releases are significant after field burning of
                        agricultural residues, but this may also require further study.
                        Long term changes in soil carbon are certainly possible as a result of agricultural practices.
                        In the land use change and forestry chapter, there is A general default assumption that soil
                        carbon is gradually lost from agricultural lands over many years after forests are cleared. In
                        fact, depending on the specific agricultural and soil management practices (including
                        burning) which are used, there may be a variety of impacts on soil carbon. For example,
                        repeated burning of savannas and crop residues in fields may create a store of carbon as
                        charcoal which increases over time. This is an area which requires further research and
                        may lead to more detailed emissions  estimation methods in the future.

                        In addition, agricultural practices (e.g. overgrazing) which degrade the productivity of
                        grasslands or other agricultural lands reduce the amount of aboveground biomass which
                        regrows and could be considered a gradual emissions source for carbon dioxide. This
                        situation is not included in the basic calculations, but could be included in more refined
                        calculations. National experts should determine whether or not this is important for their
                        country, and whether or not they are able to provide input data.
                        4.4.4  References:  Agricultural  Burning

                        Andreae, M.O. 1990. Biomass burning in the tropics:  Impact on environmental quality and
                        global dimate. Paper presented at the Chapman Conference on Global Biomass Burning:
                        Atmospheric, Climatic, and Biospheric Implications, 19-23 March 1990, Williamsburg,
                        Virginia.
                        Barnard, G.W. 1990. Use of agricultural residues as fuel. In:  Pasztor, J., and LA.
                        Kristoferson (eds.). Bioenergy and the Environment. Westview Press, Boulder, Colorado, pp.
                        85-112.
                        Barnard, G.W., and LA. Kristoferson. 1985. Agricultural Residues as Fuel in the Third World.
                        Technical  Report No. 5. Earthscan, London.
                        Bolin, B., ET. Degens, P. Duvigneaud, and S. Kempe. 1979. The global biogeochemical
                        carbon cycle. In: Bolin, B., E.T. Degens, P. Duvigneaud, and S. Kempe (eds.). The Global
                        Carbon Cycle. SCOPE 13. Wiley,  Chichester. pp. 1-56.
                        Bouliere, F., and M. Hadley. 1970. The ecology of tropical savannas. Annual Review of
                        Ecology Systems 1:125-152.
                        Bucher, E.H. 1982. Chaco and Caatinga-South American arid savannas, woodlands and
                        thickets. In: Huntley, B.J., and Walker, B.H. (eds.). Ecology of Tropical Savannas. (Ecological
                        Studies 42). Springer-Verlag, Berlin, pp. 48-79.
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             Coutinho, LM. 1982. Ecological effects of fire in Brazilian cerrado. In: Huntley, B.J., and
             B.H. Walker (eds.). Ecology of Tropical Savannas. (Ecological Situdies 42). Springer-Verlag,
             Berlin, pp. 273-291.

             Crutzen, P.J., M.O. Andreae. 1990. Biomass burning in the Tropics: Impact on atmospheric
             chemistry and biogeochemical cycles. Science 250:1669-1678.

             Crutzen, P.j. 1983. Atmospheric interactions — Homogenous gas reactions of C, N, and S
             containing compounds. In: Bolin, B., and R.B. Cook (eds.). 7'he Major Biogeochemical Cycles
             and Their Interactions. SCOPE 21. John Wiley, New York. pp. 67-114.

             Delmas, R. 1993. An Overview of Present Knowledge on Methane Emission from Biomass
             Burning, in A.R, van Amstel (ed.). Proceedings of an International IPCC Workshop: Methane
             and Nitrous Oxides, Methods in National Emissions Inventories and Options for Control, 3-5
             February 1993, Amersfoort, NL RIVM Report no. 481507003, Bilthoven, NLJuly.

             Delmas, R.A. and D. Ahuja. 1993. Estimating National Methane Emissions from
             Anthropogenic Biomass Burning. Working Group Report: Methane Emissions from
             Biomass Burning, in A.R. van Amstel (ed.), Proceedings of an International IPCC Workshop:
             Methane and Nitrous Oxides, Methods in National Emissions Inventories and Options for Control,
             3-5 February 1993, Amersfoort, NL RIVM Report no. 481507003, Bilthoven, NU July.

             FAO/UNEP (Food and Agriculture Organization of the United Nations/United Nations
             Environment Programme). 1981. Tropical Forest Resources /Assessment Project. FAO, Rome.

             FAO. 1993. Forest Resources Assessment 1990 - Tropical Countries. FAO Forestry Paper
             No. 112, FAO, Rome.
             Galbally, I.E. 1985. The emission of nitrogen to the remote atmosphere: Background
             paper. In: Galloway, J.N., R.J. Charlson, M.O. Andreae, and H. Rpdhe (eds.). The
             Biogeochemico/ Cycling of Sulfur and Nitrogen in the Remote Atmosphere. D. Reidel, Dordrecht.
             pp. 27-53.
             Gonzalez-Jimenez, E. 1979. Primary and secondary productivity in flooded savannas. In:
             UNESCO/UNEP/FAO (ed.). Tropical grazing land ecosystems of Venezuela. Nat Resour.
             Res. 16:620-625.
             Haggar, R.J. 1970. Seasonal production of Andropogon gayanus,  I. Seasonal changes in field
             components and chemical composition. Journal of Agricultural Science 74:487-494.
             Hao, W.M., M.H. Liu, and P.J. Crutzen. 1990. Estimates of annual and regional releases of
             CO2 and other trace gases to the atmosphere from fires in the tropics, based on the FAO
             statistics for the period 1975-1980. In: Goldammer, J.G. (ed.). fire in the Tropical Biota,
             Ecosystem Processes and Global Challenges. Springer-Verlag, Berlin, pp. 440-462.
             Harris, D.R. 1980. Tropical savanna environments: Definition,  distribution, diversity, and
             development. In: Harris, D.R. (ed.). Human ecology in savanna environments. Academic Press,
             New York. pp. 3-27.
             Hopkins, B. 1965. Observations on savanna burning in the Olokemeji Forest Reserve,
             Nigeria. Journal of Applied Ecology 2:367-381.
             Howden, S.M., G.M. McKeon, J.C. Scanlan, J.O. Carter, and D.H. White. Methods for
             Exploring Options to reduce Greenhouse Gas Emissions from Tropical Grazing Systems.
             Climatic Change. In Press.
             Huntley, B.J. 1982. South African savannas. In:  Huntley, B.J., and B.H. Walker (eds.).
             Ecology of Tropical Savannas. (Ecological Studies 42). Springer-Verlag, Berlin, pp. 101-119.
PART 2
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                        Huntley B.J., andJ.W. Morris.  1982. Structure of Nylsvley savanna. In:  Huntley, B.J., and
                        B.H. Walker (eds.) Ecology of Tropical Savannas. (Ecological Studies 42). Springer-Verlag,
                        Berlin, pp. 433-455.
                        Johansson, T.B., H. Kelly, A.K.N. Reddy, and R.H. Williams. 1992. Renewable Energy: Sources
                        for Fuels and Electricity. Island Press. Washington, DC.
                        Lacaux.J.P., H. Cachierand R. Delmas. 1993. Biomass Burning in Africa: An Overview of
                        Its Impact on Atmospheric Chemistry, in P.J. Crutzen and J.G. Goldammer (eds.) Fire in the
                        Environment: The Ecological, Atmospheric and Climatic Importance of Vegetation Fires. J. Wiley &
                        Sons Ltd.
                        Lacey, C.J., J. Walker, and I.R.  Nolde. 1982. Fire in Australian  tropical savannas. In:
                        Huntley, B.J., and B.H. Walker (eds.). Ecology of Tropical Savannas. (Ecological Studies 42).
                        Springer-Verlag, Berlin, pp. 246-272.
                        Lanly.J.P.  1982. Tropical Forest Resources. Food and Agriculture Organization of the United
                        Nations (FAO) Paper 30.  FAO, Rome.
                        Lashof, D.A., and D.A. Tirpak  (eds.). 1990. Policy Options for Stabilizing Global Climate.
                        Report to Congress, U.S.  Environmental Protection Agency, Washington, D.C.
                        Levine, J.S. (ed.). 1990. Global Biomass Burning: Atmospheric, Climatic and Biospheric
                        Implications. The MIT Press. Cambridge, MA.
                        Lieth, H. 1978. Patterns of Primary Productivity in the Biosphere. Hutchinson Ross,
                        Stroudsberg.
                        Lobert, J.M., D.H. Scharffe, W.M. Hao, and P.J. Crutzen. 1990. Importance of biomass
                        burning in the atmospheric budgets of nitrogen-containing gases. Nature 346:552-554.
                        Menaut, J.C., L Abbadie, F. Lavenu, Ph. Loudjani, and A. Podaire. 1991. Biomass burning in
                        West African savannas. In: Levine, J. (ed.). Global Biomass Burning. MIT Press, Cambridge, in
                        press.
                        Menaut, J.C., and J. Cesar. 1982. The structure and dynamics  of a West African savanna. In:
                        Huntley, B.J., and B.H. Walker (eds.). Ecology of Tropical Savannas. (Ecological Studies 42).
                        Springer-Verlag, Berlin, pp. 8-100.
                        Menaut, J.C. 1990. B/omoss burning in West African savannas. Presentation given at the
                        Chapman  Conference on  Global Biomass Burning. Williamsburg, Virginia, March 19-23.
                        Proceedings forthcoming:  MIT Press, Cambridge, Massachusetts.
                        Ponnamperuma, F.N. 1984. Straw as a source of nutrients for wetland rice. In: Organic
                        Matter and Rice. International Rice Research Institute, Los Banos. pp. 117-135.
                        San Jose, J.J., and E. Medina. 1976. Organic matter production in the Trachypogon savannas
                        in Venezuela. Tropical Ecology  17:113-124.
                        Seiler, W., and P.J. Crutzen. 1980. Estimates of gross and net fluxes of carbon between the
                        biosphere and the atmosphere from biomass burning. Climatic Change 2:207-247.
                        Singh, K.P., and R. Misra.  1978. Structure and Functioning of Natural, Modified and Silvicultural
                        Ecosystems of Eastern Utter Pradesh. Technical Report MAB Research Project, Banaras
                        Hindu University, Varanasi.
                        Strehler, A., and W. Stiitzle. 1987. Biomass residues. In: Hall, D.O., and R.P. Overend
                        (eds.). Biomass: Regenerab/e Energy. John Wiley,  Chichester. pp. 75-102.
                        U.S. HEW (U.S. Department of Health, Education, and Welfare). 1970. Air Quality Criteria
                        for Carbon Monoxide. U.S.  HEW, Washington, D.C.
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             Whittaker, R.H., and G.E. Likens. 1975. The biosphere and Man. In: Lieth, H., and R.H.
             4.4.5   Endnotes

             I       It is important to note, as discussed in the introduction to this document, that
                     there is an intentional double counting of carbon emitted from combustion. First,
                     CO2 is calculated based on the assumption that all carbon in fuel is emitted as
                     CO2. Methods are provided to then estimate portions of total carbon which are
                     emitted as CH4 and CO. The reasons for this double counting are discussed in
                     the introduction. For biomass combustion, CO2 emissions are frequently not
                     considered net emissions, and this is the cases for agricultural burning. One could
                     argue, in such cases, that this burning could be considered a short term sink of
                     CO2. That is, a portion of carbon in biomass is being released as net emissions of
                     CH4 and CO, while regrowth is removing the full aimount of the original carbon
                     from the atmosphere in the next cycle. Each year plants take up a certain amount
                     of carbon from the atmosphere. When they are burned some of that carbon is
                     converted to CO, and CH4, so that some  amount less than the total CO2 taken
                     up by the plants is re-emitted as CO2. See Howden et al. (in press), for a more
                     detailed discussion of this proposal. Treating emissions of CO and CH4 to the
                     atmosphere, as a sink for atmospheric CO2, however, is inconsistent with the
                     proposed IPCC emissions methodology, for the same reasons that some of the
                     carbon emissions from fossil fuel are double counted. Most importantly, the
                     other carbon compounds emitted are converted back into CO2 in the
                     atmosphere over periods of days up to a decade or so. Thus, over the time
                     horizons of interest for CO2, (i.e. more than 100 years) there is no sink of CO2.
             2       Emissions inventory developers are encouraged to provide estimates of
                     uncertainty along with these best estimate values where possible or to provide
                     some expression of the level of confidence associated with various point
                     estimates provided in the inventory. Procedures  for reporting this uncertainty or
                     confidence information are discussed in Volume  I: Reporting Instructions.
             3       Emission ratios used in this section are derived from Crutzen and Andreae
                     (1990), Delmas (1993), Delmas and Ahuja (1993) and Lacaux, etal. (1993) as
                     presented in tables. They are based on measurements in a wide variety of fires,
                     including forest and savanna fires in the tropics and laboratory fires using grasses
                     and agricultural wastes as fuel. In many cases these ratios are general averages for
                     all biomass burning. Research will need to be conducted in the future to
                     determine if more specific emission ratios, e.g., speicific to the type of biomass and
                     burning conditions, can be obtained. Also, emission ratios vary significantly
                     between the flaming and smoldering phases of a fire. CO2, N2O, and NOX are
                     mainly emitted in the flaming stage, while CH4 and CO are mainly emitted during
                     the smoldering stage (Lobert et al., 1990). The relsitive importance of these two
                     stages will vary between fires in different ecosystems and under different climatic
                     conditions, and so the emission ratios will vary. As inventory methodologies are
                     refined, emission ratios should be chosen  to represent as closely as possible the
                     ecosystem type being burned, as well as the characteristics of the fire.

             4       Bouliere and Hadley, 1970
             5       Bolin etal. (1979), Whittaker and Likens  (1975), Lanly (1982), Laceyetal.
                     (1982), and Hao etal. (1990).
             6       Harris, 1980; Bucher, 1982; Huntley, 1982; all as cited in Hao et al., 1990
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                         10
                         II.
                         12
If grazing pressure coupled with burning too often reduces biornass (i.e., degrades
the quality of savannas), then this needs to be considered as a carbon dioxide
source. This is not assumed in the basic calculations but could be included as a
refinement if considered important.
Most countries with significant savanna area should have national statistics on the
total area, but FAO publications (e.g. FAO, 1993) also provide country specific
estimates.
If the area of savanna is not readily available, then the area of "open, broadleaved
forests," including open, broadleaved, fallow areas, as defined by the U.N. Food
and Agriculture Organization in FAO (1993) can be used as an estimate. This land
area, corresponds to "mixed broadleaved forest-grassland tree formations with a
continuous dense grass layer in which the [woody vegetation covers] more than
10% [of the area]" (Lanly,  1982). FAO (1993) provides 1990 estimates of this
area, by country, for tropical America, Asia, and Africa. Hao et al. (1990) provide
an estimate of the humid savanna area in Australia, based on work by Lacey et al.
(1982).
It is  hoped that individual  countries have this information since it is needed to
execute the proposed methodology. Regional estimates of these statistics are
provided by Menaut (1990) and Hao et al. (1990) and reproduced in a table. More
country-specific research  is clearly needed on this issue before accurate
inventories can be developed. This research should include data on savanna area
burned  annually, savanna biomass densities, live fractions of biomass, burning
efficiencies, and carbon contents of savanna biomass. In the meantime, default
values can be used.
Delmas and Ahuja, 1993.
Menaut et al. (1991) calculate this number by multiplying the maximum biomass
density of the savanna (which generally is reached at the end of the growing
season) by a coefficient that declines as the burning occurs later in the dry
                         13      Singh and Misra, 1978.
                         14  .   San Jose and Medina, 1976; Gonzalez-Jimenez, 1979; Coutinho, 1982; Hopkins,
                                 1965; Haggar,  1970; Menaut and Cesar, 1982; and Huntley and Morris, 1982.

                         IS      Lacey etal., 1982.

                         16      Hao etal., 1990.
                         17      Menaut etal.,  1991.
                         18      Menaut etal.,  1991.
                         19      This approach is adapted from Crutzen and Andreae, 1990, with some values
                                 updated based on more recent studies by Delmas (1993), Delmas and Ahuja
                                 (1993)  and Lacaux et al. (1993).

                         20      from Crutzen and Andreae, 1990.
                         21      There is an inconsistency in the methodology in the treatment of the full
                                 molecular weight of NOX. In fossil energy and industry discussions NOX  is
                                 expressed as though all of the N were in the form of NO2. In biomass burning
                                 literature, (e.g., Crutzen and Andreae,'l990) NOX is often discussed as though
                                 most of the emissions were in the form of NO. Therefore, the biomass  burning
                                 discussions in these Guidelines convert NOX-N to full weight using the
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                                                                                                AGRICULTURE
                      conversion factor (30/14) for NO. All other references to NOX are based on the
                      full weight of NO2 (i.e., the conversion factor from NOX-N would be 46/14).

              22      Barnard (1990) outlines several broad categories of crop residue:  woody crop
                      residues (coconut shells, jute sticks, etc.), cereal residues (rice and wheat straw,
                      maize stalks, etc.), green crop residues (groundnut straw, soybean tops, etc.), and
                      crop processing residues (bagasse, rice husks, etc.).

              23      Barnard, 1990; Ponnamperuma, 1984.

              24      Ponnamperuma,  1984

              25      Strehler and Stutzle,  1987

              26      Ponnamperuma,  1984

              27      Crutzenand Andreae, 1990

              28      Barnard and Kristoferson, 1985.

              29      I Tg dm = 10 Grams of Dry Matter, estimates are from Crutzen and Andreae
                      (1990)

              30      See also  United Nations World Trade Yearbooks.

              31      In this context, one should also note the book Renewable Energy: Sources for Fuels
                      and Electricity edited by Johansson et al. (1992).

              32      Dry matter (dm), or dry biomass, refers to biomass in a dehydrated state.
                      According to Elgin (1991), the moisture content of crop residue varies depending
                      on the type of crop residue, climatic conditions (i.e., in a humid  environment the
                      residue will retain more moisture than in an arid einvironment),  and the length of
                      time between harvesting and burning of the residue. From a simple perspective,
                      one can use the dry matter content values in Table D to convert from total crop
                      residue to dry matter. For example, if 200 tonnes of crop residue with a moisture
                      content of 10%, would have a dry matter content of 90%, equal  to 180 tonnes of
                      dry matter. To convert from dry matter to carbon content, an average value of
                      0.45 t C/t dm can be  used in the cases where cropi specific data  are not available.
                      The terms dry matter and dry biomass are used interchangeably in this text.

              33      Crutzen and Andreae, 1990. The estimates are very speculative  and should be
                      used with caution. The  actual percentage burned varies substantially by country
                      and crop type. This is an area where locally developed, country  specific data are
                      highly desirable. As this issue is studied  further, it may be possible to incorporate
                      more accurate, country-and crop-specific percentages into future editions of the
                      Guidelines.

              34      To account for charcoal formation and other aspects of incomplete combustion.
                      See Seller and Crutzen  (1980) and Crutzen and Andreae (1990).

              35      This approach is adapted from Crutzen and Andreae, 1990, with some values
                      updated based on more recent studies by Delmas (1993), and Delmas and Ahuja
                      (1993).

              36      Crop specific values are generally in the range of 0.01 -0.02, from Crutzen and
                      Andreae,  1990, so that  0.015 can be used as a generally representative value if no
                      other information is available.

              37      There is an inconsistency in the methodology in the treatment of the full
                      molecular weight of NOX. In fossil energy and industry discussions NOX is
                      expressed as  though all of the N were in the form of NO2. In biomass burning
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                             literature, (e.g., Crutzen and Andreae, 1990) NOX is often discussed as though
                             the emissions were in the form of NO. Therefore, the biomass burning
                             discussions in these Guidelines convert NOX-N to full weight using the
                             conversion factor (30/14) for NO. All other references to NOX are based on the
                             full weight of NO2 (i.e., the conversion factor from NOX-N would be 46/14).
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              4.5    Nitrous  Oxide  Emissions from
              Agricultural  Soils


              4.5.1  Introduction

              This chapter covers emissions of nitrous oxide (N20) from agricultural soils. Estimates of
              N2O emissions from the biosphere into the atmosphere are: highly uncertain, but it is
              believed that about 70% originate from soils (Bouwman, 1990; Houghton et al., 1992). It
              seems reasonable then, to assume that changes in N cycling in soil systems have influenced
              the increases in atmospheric N2O during the past century and will help dictate future
              changes in atmospheric N2O. A direct effect, that can be quantified, is the increase in N
              input into the soil systems. This increase in N input is derived from atmospheric
              deposition, which ranges from about 0.5 g N m"2 y'1 in the central U.S. to 6 g N m"2 y"1 in
              western Europe (Andreae and Schimel, 1989), N fertilization with mineral N sources or
              animal manures and biological N fixation. Nitrogen fertilizer use and biological N-fixation
              are projected to continue to increase during the next 100 years (Hammond, 1990).
              To determine N2O emissions from agricultural soils for various parts of the earth, we
              must predict how much N2O is produced from each unit of fixed N (chemically or
              biologically) that is added to the soil. To make this prediction we first must understand
              how and where N2O is produced in the biosphere, what sinks exist for the gas, and how
              the gas moves from where it is produced into the atmosphere. Research during the past
              several decades provides an understanding of how N2O is produced, factors that control
              it's production, source/sink relationships, and gas movement: processes. However, even
              with this large amount of knowledge, we are not yet able to reliably predict the fate of a
              unit of N that is applied or deposited on a specific agricultural field. Studies of emissions of
              N2O from presumably "similar" agricultural systems show highly variable results in both
              time and space. It is the complex interaction of the physical and biological processes
              involved that must be understood before appropriate predictive capability can be
              developed.

              It is surprising that during the last few years, with the renewed interest in climate change
              and the role of radiatively active trace gases, little new information concerning emissions
              of N2O from agricultural fields has been published. Many recent review papers and
              inventory assessments  have all relied on published gas flux measurements from studies
              conducted, primarily, during the late 1970's and early 1980's. The number of flux
              measurements and the variety of soil conditions examined are limited. Therefore, the data
              from which these reviews and inventories have been drawn are also limited and because of
              the limitations, inappropriate conclusions may have been drawn.

              As noted in the OECD/OCDE (1991) report, we know that N2O is produced primarily
              from the microbial processes, nitrification and denitrification  in the soil. In well aerated
              conditions, where soil moisture content is low enough not to limit aeration, N2O
              emissions from nitrification of ammonium based fertilizers can be substantial (Bremner and
              Blackmer, 1978; Duxbury and McConnaughey, 1986). Other work suggests that N2O
              release is a byproduct of nitrification (Yoshida and Alexander, 1970) and may occur by
              denitrification of nitrite by nitrifying organisms under oxygen stress (Poth and Focht,
              1985). Recent evidence indicates that in well aerated, porous soils, little N2O may evolve
              but much larger amounts of NO may be emitted  during  nitrification (Williams et al., 1993).
              In wet soils where aeration is  restricted, denitrification is generally the source of N2O
              (Smith, 1990). Under these conditions both the rate of denitrification and the N2O/(N2 +
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                        N2O) ratio must be known to evaluate N2O emissions through denitrification. According
                        to Smith (1990), soil structure and water content, affecting the balance between diffusive
                        escape of N2O and its further reduction to N2 are important among the factors
                        determining the proportions of the two gases.
                        Research has also shown us that a number of individual factors are controllers of
                        nitrification and denitrification. Such factors as soil water content, which regulates oxygen
                        supply; temperature, most organisms have a temperature range over which reaction rates
                        are optimal; nitrate or ammonium concentration, substrates may individually regulate
                        reaction rates and in the case of denitrification regulate the N2O/N2 ratio; available organic
                        carbon, denitrifiers require a usable organic carbon source and microbial respiration of
                        organic carbon may also regulate oxygen supply; and pH, is a controller of both
                        nitrification and denitrification and the N2O/N2 ratio in denitrification.
                        Increases in the amount of N added to the soil generally increases N2O emissions from
                        the soil (Bouwman,  1990). The temporal pattern of N2O emissions following fertilization is
                        generally that of a large efflux of N2O occurring for a short time (about six weeks). After
                        this time, emission rates are reduced to fluctuate around a low base-line level independent
                        of the amount of fertilizer applied (Hosier et al., 1983). Some studies indicate that N2O
                        emission rates are higher for ammonium-based fertilizers than for nitrate (Eichner, 1990).
                        For example, Bremner etal. (1981) found a much higher proportion of N2O released from
                        anhydrous ammonia than from urea or ammonium sulfate. Bouwman's (1990) review,
                        however, suggested no particular trend in N2O emissions related to fertilizer type. Byrnes
                        etal. (1990) suggest that N2O emissions from the nitrification of fertilizers may be more
                        closely related to soil properties than to the N source that is supplied. Mineral N
                        applications along with  organic matter amendments generally increase total denitrification
                        and N2O production.
                        As discussed in more detail by Hosier (1989), N2O emissions from the soil can vary by
                         orders of magnitude from a location both spatially and temporally. These heterogeneities
                         in both space and time in measured gas fluxes and in the microbial activity which produces
                         the gases make predictions highly uncertain.
                         External factors also perturb "normal" soil N cycling and thus increase N2O  emissions.
                         Land use conversion has been a primary factor in the past (Houghton and Scole, 1990),
                         and conversion of forests and grasslands to croplands accelerated C and N cycling and
                         increased N2O emissions from the soil. Globally, land use conversion is important now
                         only in tropical areas. Most of the conversions of forests and grasslands in the northern
                         hemisphere occurred 50 to 200 years ago (Hammond,  1990). Global changes may impart
                         changes in soil temperature and moisture which will directly influence N cycling.


                         4.5.2  1991   OECD  NjO  Emission  Methodology

                         The first OECD/OCDE (1991) methodology for calculating N2O emissions from nitrogen
                         fertilizers was based on the amount of each type of commercial fertilizer nitrogen
                          consumed (in mass units of N), an emission coefficient for the fraction of applied N that is
                          released as N2O-N for each fertilizer type, and a factor used to convert the emission from
                          N2O-N to N2O. Emissions of N2O-N are estimated from each fertilizer type, summed
                          over all types, and then converted to units of N2O:

                          (I)      N2O-N Emissions (tonnes N2O-N) = £(F,x Ef)

                          where:
                          F = Fertilizer Consumption (tonnes N)
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              E = Emission Coefficient (Tonnes N2O-N released/tonne N applied)

              f = Fertilizer type

              N2O Emissions (tonnes N2O) = N2O-N Emissions (tonnes N2O-N) x 44/28.

              The Working Group suggested dropping the attempt to calculate N2O emissions based on
              the type of commercial fertilizer N applied. Considering the number of agricultural
              systems that exist world wide and the number of sources of N available for use, the data
              set available for these analyses are quite small. As a result, single studies at single locations
              can dominate, and possibly skew the analysis. Another point is that since most of the data
              cited were from  studies conducted only during the cropping season, or part of the
              cropping season, little is known about N emissions following crop harvest and before
              planting in the  spring. Recent research (Sommerfeld et al., 1993) indicates that appreciable
              N2O emissions can occur from snow covered soils and Goodroad and Keeney (1984)
              noted large fluxes of N2O during winter thaw periods. The Expert Group concluded that
              there is no justification for including fertilizer type in the equation, as existing data shows
              wide, overlapping ranges of emission factors for each commercial fertilizer type. Many
              studies show that field variables such  as the interaction of soil  type, soil water content, and
              substrate availability regulate N2O emissions rather than N source.

              The second OECD/OCDE (1991) methodology includes the fertilizer source variable
              discussed in section A and also includes the crop type to which the fertilizer is applied.
              The approach is the same as section A except that emissions of N2O-N are summed over
              all fertilizer and crop types, instead of just over all fertilizer types.
              (2)
N2O-N Emissions (tonnes N2O-N) =Z (Ffc x E fc)
              where          F = Fertilizer Consumption (tonnes N)
                             E = Emission Coefficient (tonnes N2O-N released/tonne N applied)
                             f = Fertilizer Type
                             c = Crop Type
              N2O Emissions (tonnes N2O) = N2O-N Emissions (tonnes iN2O-N) x 44/28
              Including crop type in the calculation seems reasonable since the type of crop tends to
              regulate soil water content, the timing of mineral N  uptake, and the release of
              mineralizable carbon into the soil. All of these factors are regulators of N2O-forming
              processes. But as noted in OECD/OCDE (1991) there is not enough information to
              calculate the necessary coefficients for each crop type. This calculation  is therefore no
              longer recommended.
              4.5.3  Suggested N2O  emission  calculation
              method

              As the data available from which to calculate N2O emission coefficients from either N
              fertilizer source or crop type are not adequate to make such calculations, and it is unlikely
              that within the next few years sufficient studies will be conducted to make adequate
              coefficient calculations, the following, simplified calculation is recommended for estimating
              N2O emission from agricultural soils:

              (3)      N2O-N Emission (tonnes N2O-N) =2  F x 0.01
              where          F = Fertilizer Consumption (tonnes N)
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                       where          F = Fertilizer Consumption (tonnes N)

                       N2O Emissions (tonnes N2O) = N2O-N Emission (tonnes N2O-N) x 44/28

                       Because of the limitations of the data available and the scope of the data, a value of
                        1%/year of fertilizer (both mineral and organic) N direct emission from agricultural fields
                       does not seem unreasonable. The literature on field N2O flux are adequate to provide the
                       order of magnitude of the multiplication coefficient, greater than 0.001 and less than O.I'
                       (CAST, 1992).
                       There is certainly room for arguing the validity of this suggestion. For example in a flooded
                       rice field, when fertilizer N is added immediately before flooding, little N2O is emitted
                       (Freney et al., 1981). We do not know, however, how much N2O evolves from the field
                       when the water is drained for harvest or during the intercrop dry period. Some evidence
                       indicates that appreciable N2O is evolved from a rice field during the first few days after
                       the field is flooded (Byrnes et al., 1993). A simple equation relating soil mineral N content
                       and soil % water-filled pore space to N2O emissions integrated through the entire year
                       may represent N2O emissions reasonably well. There is, unfortunately, no possibility to
                        link this to national inventory calculations.
                       The second major point discussed by the Expert Group was that the OECD (1991)
                        method only addressed direct N2O emissions from cultivated agricultural soils that had
                        been fertilized with commercial fertilizer N. The consensus of the group was that this
                        narrow concept is not appropriate since N from (I) atmospheric deposition, (2)
                        commercial fertilizer, (3) animal manures and plant residues, (4) biological N  fixation, and
                        (5) soil organic matter mineralization should all be  considered in the equation. World-
                        wide, the amount of N input into agricultural systems from animal manures and biological
                        N fixation is roughly the same as the input from commercial fertilizer N (about 80 Tg in
                        1990). Nitrogen input from atmospheric deposition varies globally from about  I to 50 kg
                        N ha"1 y"1 while N from mineralization of soil organic matter may vary from  10 to 200 kg
                        N ha  y , both are site dependent.
                        Based upon information that is considered to be available in most countries, the following
                        N2O emission calculation method is suggested:

                        a) Low Estimate
N20 Emission = 2 (Fmn + Fon + Fbnf) * C0,

b. High Estimate

N20 Emission = £ (F^ + Fon + Fbnf) * C0,

c. Median Estimate
                                                           •0.0005
                                                            1.039
                        N20 Emission = 2 (Fmn + Fon + Fbnf) * COM3t
                        Where Fmn = amount of mineral N applied

                        FO,, = amount of organic N applied (animal manure or crop residue)

                        F^ = amount of biological N fixation

                        CD 0005  = low end of emission coefficient range

                        C0039  = high end  of emission coefficient range

                        C0,oo3«  = median emission coefficient
                        Units are in Tg of N for input and Tg N2O-N x 44/28 for total N2O emission. The
                        emission coefficients are those used by OECD (1991) on page 5-51  based on total
                        commercial fertilizer N consumed and N2O emission based on these low, high, and median
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             emission factors. These numbers should span the range of most measured N2O emissions.
             It was felt that because the range of measured N2O emissions from different agricultural
             systems is so large, the whole range must be considered to convey the uncertainty in using
             these estimates.
             Most of the information to calculate N2O emissions are avsiilable for many countries, but
             part may not be readily available for others:

             a) N from commercial fertilizer. Total N  consumption as v/ell as mean N-application level
             (in kg/ha of arable land) is available for all countries in the FAO Fertilizer Yearbooks  (e.g.
             FAO, I990a).
             b) N from animal manure. Animal population data is available from the FAO Production
             Yearbooks (e.g. FAO,  1990b). The amount of N in the excreta and the volatilization  of
             ammonia are well known for most parts of the world. Whesre such data are not available,
             estimates can be made based on animal diet. Further data required are: the portion of the
             year that animals are grazed and confined, and the portion of the manure collected in the
             stables and the portion applied  to the soil.
             The working group on NH3 of the Global Emission Inventories Activity (GEIA), a core
             project of the  International Global Atmospheric Chemistry Program (IGAC) will develop a
             methodology to estimate the above parameters. For countries having difficulties to obtain
             the data, these GEIA-estimates  could be used as default values.

             c) N from biological N-fixation. Data on the areas cropped to leguminous crops, such
             alfalfa, pulses, soy beans, are readily available from FAO Production Yearbooks (e.g. FAO,
              I990b). Commonly, leguminous crops are not fertilized with commercial N, or are
             fertilized only a small amount of starter N. It is difficult to estimate the amount of N  fixed
             by the crop if we do not know  the amount of soil N before sowing and after harvest, as
             well as the yield and % N in the crop.
             4.5.4  For  the Future

             The OECD Expert Group made the following suggestions for improving the methodology
             for estimating N2O emissions from agricultural soils:
             I    The assumption that N2O emissions directly from fertilizers are relatively small
                  should be reviewed. A critical look at the reviews of Eichner (1990), Bouwman
                  (1990) and CAST (1992) indicate that a conservative estimate of direct emission of
                  N2O from mineral fertilizer over a full year are in the range of I % of the N applied,
                  currently about I  Tg, or about 10% of current global emissions. This estimate does
                  not include either organic N fertilizer from human and farm animal excreta or N
                  fixed by biological N fixation. Limited data suggest that N2O emissions from these N
                  sources are generally greater than from mineral N application (Bouwman, 1990).
                  Assuming that N emissions from all sources are equal, the direct emissions from all
                  three N sources could total 3 Tg annually.
             2    Although the individual factors that regulate N2O production are known, we cannot
                  predict how these factors interact under field conditions to produce measured fluxes
                  (OECD/OCDE, 1991). Both nitrification and denitrification and the regulators of
                  N2O/N2 ratios from denitrification have their own set: of optimum conditions. As a
                  result, one process may be the primary N2O producer in one set of field conditions,
                  but as soil conditions change, another process may predominate. The complexity of
                  the interactive factors important to the different processes obviously make a simple
                  description of N2O production difficult (Hosier et al., 1983). Complex models such
                  as that described by Li et al. (1992) may be the only way that N2O fluxes may be
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                             predicted. Simpler, mechanistic models such as that described by Parton et al. (1988)
                             may, however, play a role in simplifying estimation of N2O emission. To accurately
                             inventory N2O emissions from agricultural soils we must be able to predict N2O
                             emissions based  on N application, soil, crop and management.

                             It is also likely that N2O production resulting from fertilizer and increased use of
                             biological nitrogen fixation is underestimated because the effect of a nitrogen input is
                             usually only partially traced through the environment. In an example taken from
                             Duxbury et al. (1993), 50 of the  100 kg ha'1 of N  applied  as fertilizer on a typical
                             dairy farm are harvested in the crop, and 50 are lost by the combination  of leaching
                             (25), surface run-off (5), and volatilization (20, primarily denitrification). If N2O
                             comprises 10% of the volatilized  N, 2 kg N2O-N would be generated  in the primary
                             cycle. Assessments of fertilizer effects on N2O emissions usually stop at this point
                             even though only 20 of the 100 kg N have been returned to the atmosphere and  it
                             can be reasonably assumed that almost all would  be returned within a few years.

                             Secondary flows include feeding of the 50 kg of harvested N to animals, which
                             generate 45  kg of manure N. The manure is returned to  cropland to  fertilize a
                             second crop, however about half of this N is volatilized as NH3 prior to or during
                             manure application. Volatilized NH3 is aerially dispersed and subsequently returned
                             to and cycled through both natural ecosystems and cropland. Ammonia volatilization
                             from agricultural systems is globally important (Isermann, 1992) but its impact on
                             N2O emissions  have not been explicitly addressed. To provide some  perspective, it
                             should be noted that the quantities of fertilizer N used and animal manure N
                             generated by USA agriculture  are equal (Bouldin  et al., 1984). On a global basis, about
                             30 of the 80 Tg fertilizer N used each year are volatilized as NH3.
                             Similarly, the amount of N2O arising from leached nitrate, which may average 20-25%
                             of applied N (Meisinger and Randall, 1991), is not known but much may be denitrified
                             in riparian zones or cycled through wetland or aquatic vegetation. A  complete
                             accounting of fertilizer N, biologically fixed N, and N mineralized from soil organic
                             matter is-difficultto achieve, but needed if we are to accurately assess the impact of
                             increased use of N in agricultural ecosystems on terrestrial N2O emissions (Duxbury
                             etal., 1993).
                             The Working Group felt that considering only N2O emissions from cultivated
                             agricultural soils was too narrow a view. The whole picture of anthropogenic effects
                             of N2O emissions should include the indirect fertilization of grasslands, forests and
                             wetlands from agricultural and industrial sources. Since cultivated lands represent
                             only about 13% of the global land surface it does not seem appropriate to consider
                             only those areas when  estimating global N2O emissions.
                             Calculations of N additions and  N cycling within  all of these ecosystems must include
                             N from atmospheric deposition and N from soil organic matter mineralization. The
                             entire calendar year should be considered, not just the cropping season.

                             Improving methodology for estimating N2O emissions may evolve in a series of steps,
                             beginning with  the above equations and ending with development of process based
                             models which are used to develop regional and larger scale emission models. With
                             these models, if a relatively simple set of input information can be developed, then
                             detailed emission calculations may be made. Because of  the inherent spatial and
                             temporal variability associated with N2O production and emissions from soils, it
                             appears that very simple approaches will not provide realistic emission estimates.

                             To support the development of the steps for improved  methodology for calculating
                              country-wide N2O emissions, a number of unknowns were identified. Better
                              understanding of these issues should improve methodologies.
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                 a    Research needs specifically for agricultural systems include:
                      i    Improve management strategies to optimize N use efficiency and match
                          plant N input needs.

                      ii   Facilitate integration of animal and crop production systems within the
                          agricultural industry.

                      iii   Develop mitigation strategies at the farm level.

                      iv   Perform measurements in important tropical agricultural systems.
                      v   Develop strategy to provide farmers with options and knowledge about N
                          use to limit N leakage.

                 b    General recommendations:

                      i    Estimate anthropogenic N input into "natural systems" and amount
                          processed into N2O.

                      ii   Develop process level models, based on field research measurements,
                          refine and test the models and use these models as basis for developing
                          regional and  larger scale emission models.
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                       4.5.5  References

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                       Terrestrial Ecosystems and the Atmosphere. John Wiley & Sons. 346 p.
                       Bouldin, D.R., S.D. Klausneer and W.S. Reid. 1984. Use of nitrogen from manure. In R.D.
                       Hauck (ed.). Nitrogen in Crop Production. Amer. Soc. Agron. Madison, Wl. pp. 221-245.
                       Bouwman, A.F. 1990. Exchange of greenhouse gases between terrestrial ecosystems and
                       the atmosphere. In A.F. Bouwman (ed.). Soils and the Greenhouse Effect. John Wiley &
                       Sons. New York. pp. 61-127.
                       Bremner, J.M. and A.M. Blackmer. 1978. Nitrous oxide:  emissions from soil during
                       nitrification of fertilizer nitrogen. Science.  199:295-296.
                       Bremner, J.M., G.A. Breitenbeck and A.M.  Blackmer. 1981. Effect of nitrapyrin on emission
                       of nitrous oxide from soil fertilized with anhydrous ammonia. Geophys. Res. Lett. 8:353-
                       356.
                       Byrnes, B.H., L S. Holt and E.R. Austin. 1993. The emission of nitrous oxide upon wetting
                       a rice soil following a dry season fallow. J. Geophys. Res. (In Press).
                       Byrnes, B.H., C.B. Christiansen, LS.  Holt and E.R. Austin. 1990. Nitrous oxide emissions
                       from the nitrification of nitrogen fertilizers. In A.F. Bouwman(ed.). Soils and the
                       Greenhouse Effect. ChichestenWiley. pp.  484-495.
                       CAST. 1992. Preparing U.S. Agriculture for Global Climate Change. Task Force Report
                       No. 119. P.E Waggoner, Chair. Council for Agricultural Science and Technology. Ames,
                       IA. 96 pp.
                       Duxbury, J.M.  and P.K. McConnaughey. 1986. Effect of fertilizer source on denitrification
                       and nitrous  oxide emission in a maize field. Soil Sci. Soc. Am. J. 50:644-648.
                       Duxbury, J.M., LA. Harper and A.R. Mosier. 1993. Contributions of agroecosystems to
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                       data.J. Env. Qual. 19:272-280.
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                        Freney, J.R., O.T. Denmead, I. Watanabe and E.T. Craswell. 1981. Ammonia and nitrous
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                        32:37-44.
                        Goodroad,  LL and D.R. Keeney. 1984. Nitrous oxide emissions from soils during thawing.
                        Can. J. Soil Sci. 64:187-194.
                        Hammond,  A.L 1990. World Resources 1990-91. A report by The World Resources
                        Institute, Oxford University Press. Oxford, UK. 383 pp.
                        Houghton, R.A. and D.L Skole. 1990. Changes in the global carbon cycle between 1700
                        and  1985. in B.L Turner (ed.). The  Earth  Transformed by Human Action.  Cambridge
                        University Press.
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             Houghton, J.T., B.A. Cailander and S.K. Varney (eds.). 1992. Climate Change 1992. The
             Supplementary Report to the IPCC Scientific Assessment. Intergovernmental Panel on
             Climate Change. Cambridge University Press. 200 pp.

             Hynes, R.K. and R. Knowles. 1978. Inhibition of acetylene of ammonia oxidation by
             Nitrosomas europea. FEMS Microbiol. Lett. 4:319-321.

             Iserman, K. 1992. Territorial, Continental and Global Aspects of C, N, P and S Emissions
             from Agricultural Ecosystems. In NATO Advanced Research Workshop (ARW) on
             Interactions of C, N, P and S Biochemical Cycles. Springer-Verlag, Heidelberg (In Press).
             Li, C., S. Frolking and T.A. Frolking. 1992. A model of nitrous oxide evolution from soil
             driven by rainfall events:  I. Model Structure and Sensistivity. j. Geophys. Res. (In Press).
             Meisinger, J.J. and G.W. Randall. 1991. Estimating nitrogen budgets for soil-crop systems. In
             Managing Nitrogen for Ground Water Quality and Perm Profitability. R.F. Follett, D.R.
             Keeney and R.M. Cruse (eds.). Soil Sci. Soc. Am. Inc. Madison, Wl. pp.  85-124.
             Mosier, A.R. 1989. Chamber and isotope techniques. In M.O. Andreae and D.S. Schimel
             (eds.). Exchange of Trace Gaes between Terrestrial Ecosystems and the Atmosphere.
             Chichester:Wiley. pp. 175-187.
             Mosier, A.R., W.J. Parton and G.L Hutchinson. 1983. Modelling nitrous oxide evolution
             from cropped and native  soils. R. Hallberg (ed.). Ecol. Bull (Stockholm). 35:229-241.
             OECD/OCDE. 1991. Estimation of Greenhouse Gas Emissions and Sinks. Final report
             from the OECD Experts  Meeting, 18-21 February, 1991. Prepared for Intergovernmental
             Panel on Climate Change. Revised August, 1991.
             Parton, W.J., A.R. Mosier and D.S. Schimel. 1988. Rates and pathways of nitrous oxide
             production in a shortgrass steppe. Biogeochemistry. 6:45-58.
             Poth, M. and D.D. Focht. 1985. I5N kinetic analysis of N2O production by Nitrosomas
             europea:  an examination  of nitrifier denitrification. Applied. Env. Microbiol. 49:1 134-1 141.
             Smith,  K.A. 1990. Greenhouse gas fluxes between land surfaces and the atmosphere.
             Progress in Physical Geography. 14:349-372.
             Sommerfeld, R.A., A.R. Mosier and R.C. Musselman. 1993. CO2> CH.,, and N2O flux
             through a Wyoming snowpack and implication for global budgets. Nature. 361:140-142.
            _ Williams, E.J., G.L. Hutchinson and F.C. Fehsenfeld. 1993. NOX and N2O emissions from
             soil. Global Biogeochem.  Cycles. (In Press).
             Yoshida,  R. and M. Alexander. 1970. Nitrous oxide formation by Nitrosomas europea and
             heterotrophic microorganisms. Soil Sci. Soc. Am. Proc. 34:880-882.
PART 2
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AGRICULTURE
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                      CHAPTER 5
               LAND USE CHANGE
                    & FORESTRY
PART 2
5.1

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LAND USE CHANGE & FORESTRY
 5.2

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                                                              LAND USE CHANGE  &  FORESTRY
                      EMISSIONS  FROM  LAND  USE CHANGE
                      AND  FORESTRY
     5.1    Overview

             This chapter summarizes methods for calculating greenhouse gas (GHG) emissions from
             human activities which:

             I    change the wayland is used (e.g., clearing of forests for agricultural use, including
                  open burning of cleared biomass), or

             2    affect the amount of biomass in existing forests (e.g., logging, fuelwood harvesting).

             The biosphere is a strong determinant of the chemical composition of the atmosphere.
             This has been true since the existence of the biosphere, and hence well before the
             presence of humans. A rich variety of carbon, nitrogen, and sulfur gases are emitted and
             absorbed by the biosphere. There is, however, strong evidence, that the expanding human
             use and alteration of the biosphere for essential food, fuel and fiber is contributing to the
             increasing concentrations of greenhouse gases. The dominant gas of concern in this source
             category is carbon dioxide  (CO2), and much of the methodology discussion in this chapter
             is specific to CO2. Other important direct greenhouse gase:;', including methane (CH4)
             and nitrous oxide (N2O), and indirect greenhouse gases,  including carbon monoxide (CO),
             and oxides of nitrogen (NOX, i.e., NO + NOj) are also produced from  land use change
             and forest management activities, particularly where burning is involved.

             Estimates of greenhouse gas emissions due to land use change vary considerably. Estimates
             of emissions resulting from changes in the use of forests and of forest area vary due to
             uncertainties in annual forest clearing rates, the fate of the land that is cleared, the
             amounts of biomass (and hence carbon) contained in different ecosystems, the fate of the
             biomass removed, and the amounts of CH4, CO, N2O, and NOX released when biomass is
             burned and soils are disturbed. The 1990 IPCC Scientific Assessment estimated the flux in
             1980 to be 0.6-2.5 Pg CO2-C, and estimated the average  annual  emissions for the decade
             1980-1989 to be I.6±I.O Pg CO2-C.2  Subsequently, the IPCC (1992) reviewed more
             recent but still inconclusive information, and could find no basis for changing the earlier
             estimate.  Carbon  sequestration by tropical tree plantations 'was  not explicitly included in
             these estimates but is thought to be relatively small:  in 1980 these plantations were
             estimated to absorb only 0.03-0.11 Pg CO2-C.3  At the time of the IPCC 1990
             Assessment estimates in the literature indicated the net release or uptake of CO2 due to
             land use change in the temperate and boreal regions in the 1980s to be small with CO2
             emissions from deforestation in these regions almost balanced by CO2  uptake from the
             regrowth of forests.  More recently, several  analyses have suggested that growth of
             existing forests in temperate and boreal regions may be a significant carbon sink,
             potentially as much as  1.0 Pg-C annually. Analysts have suggested a number of
             complementary factors which could be causing these sinks, including regrowth of
             historically cleared forests,  CO2 fertilization, and nitrogen fertilization due to atmospheric
             deposition.5 The precise mix of causes and magnitude of these sinks is  still a subject of
             research and debate.

             Gross emissions of non-CO2 trace gases (CH4, CO, N2O, and NOJ due to biomass
             burning are also net emissions and are generally produced immediately, while gross
             emissions of CO2 due to reductions in forest area may or may not be balanced by uptake
             of CO2 and may occur over immediate or delayed time frames.6 Similarly, increases in
             forest area or in the biomass density of existing forests will result in CO2 uptake at varying
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LAND USE  CHANGE &  FORESTRY
                        rates and over delayed time frames. Only about 50-60% of the carbon estimated to have
                        been released in 1980 was a result of deforestation in that year. The remainder was a
                        release due to oxidation of biomass cleared in previous years.  Other land use changes,
                        such as land flooding, result in continuous greenhouse gas emissions for as long as the land
                        remains in its altered state.
                        5.1.1   Background  -  biomass stocks  and carbon
                        fluxes
                        Vegetation withdraws carbon dioxide from the atmosphere  through the process of
                        photosynthesis. Carbon dioxide is returned to the atmosphere by the (autotrophic)
                        respiration of the vegetation and the decay (heterotrophic respiration) of organic matter
                        in soils and litter. The gross fluxes are large; roughly a seventh of the total atmospheric
                        carbon dioxide passes into vegetation each year (on the order of 100 Pg COrC per year),
                        and in the absence of significant human disturbance, this large flux of CO2 from the
                        atmosphere to the terrestrial biosphere is balanced by the return respiration fluxes. This
                        remarkable balance is clearly expressed by the relative constancy, which can be inferred
                        from the ice core records, of the concentration of atmospheric CO2 between 10  and
                         18* century.
                        Land use change and the use of forests •directly alters these fluxes (and their balance) and
                        consequently the amount of carbon stored in living vegetation, litter, and soils. For
                        example, forest clearing for agriculture by burning greatly increases the return
                         (respiration) flux of CO2 and decreases for a while the photosynthetic flux. Burning is,
                        after all, simply a rapid form of oxidation or decay. Subsequently, the balance on the
                         cleared area will return: the photosynthesis associated with the agricultural production
                         being balanced by the respiration of the vegetation, the decay of on-site organic material,
                         and the oxidation of the agricultural product when it is consumed, perhaps off site.
                         However, the total amount of carbon stored in the terrestrial system will have been
                         reduced because a forest contains more carbon than does a corn field, and the removed
                         carbon (i.e., the forest) was not put into long term storage pools. An obvious
                         consequence is that the activity resulted in a net flux of CO2 from the biosphere to the
                         atmosphere. A natural first order assumption is that the net reduction in carbon stocks is
                         equal to the net CO2 flux from the cleared area.
                         Forest harvest does not necessarily result in a net flux to the atmosphere. It can produce
                         a complex pattern of net fluxes that change direction over time. For instance, suppose
                         that a forest is harvested producing wood products and leaving some slash and debris.
                         Initially, the CO2 flux from the wood products that decay rapidly plus the increased
                         respiration flux of CO2 associated with the oxidation of the slash (in effect the litter pool
                         has been increased and hence so has the respiration flux associated with this pool) could
                         be greater than the flux from the atmosphere due to the photosynthesis and the resulting
                         carbon storage in the regrowing forest. Consequently, there is a net flux of CO2 from the
                         biosphere to the atmosphere. This would also be reflected in a  carbon accounting: the
                         amount of carbon in the original living vegetation, the litter, and the soils would be greater
                         than the amount of carbon in the young regrowing forests, litter, soils and forest products
                          pool. However, if some of the forest products are very long-lived, and if the forest
                          regrows to its original level, then the integrated  net flux must have been from the
                          atmosphere to the terrestrial biosphere since the resulting total terrestrial carbon stocks
                          (vegetation, litter, soils, and wood products) would be greater than before the forest
                          harvest.
   5.4


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                                                                 LAND  USE  CHANGE  &  FORESTRY
                                                   Box I
                              ILLUSTRATIVE CALCULATIONS OF CAREION FLUXES

                    Consider the example of forest clearing for agriculture which results in a net
                    flux to the atmosphere. For descriptive purposes we consider the following
                    assumptions: I) a 20 year time frame (e.g., 1970 to 1990), 2) one hectare is
                    cleared each year (so that over the 20 year period, 20 hectares are cleared),
                    3) cleared land is used as pasture, which is established the year following the
                    clearing, 4) after three years cleared land is abandoned and it regrows
                    linearly to 75% its original biomass in 15 years but no further, 5) all of the
                    vegetation is completely burned at the time of clearing and there are
                    essentially no soil or litter pools, 6) there are 200 tonnes of carbon per
                    hectare in the forest biomass and 5 tonnes carbon per hectare in the
                    pasture.

                    In the first year, there is a 200 tonne net flux of carbon as CO2 to the
                    atmosphere. In the second there is a 195 tonne net flux; the clearing of the
                    second hectare is partially balanced by the establishment of the first pasture.
                    In the third, there is a net flux again of 195; the clearing of the third hectare
                    is again partially balanced by the establishment of the second pasture;
                    however, the first pasture is now again in a steady state (as a pasture). The
                    fourth year the pattern is again the same, but in the fifth year the net annual
                    flux drops to 185 as the first pasture is now abandoned and begins to
                    recover to a secondary forest In the sixth year,  the flux drops to 175 as
                    two hectares are recovering to a secondary forest. In this example, in 1989
                    one hectare would be converted to pasture (200 tonne flux of carbon to the
                    atmosphere), one hectare would have become a pasture (5  tonne flux to the
                    terrestrial biosphere), two hectares would be in steady state as pasture, and
                    15 hectares would be recovering to secondary forest with one hectare in its
                    final year of recovery (150 tonne flux to the terrestrial biosphere). The  1989
                    gross flux of carbon from land clearing in 1989 would still be 200 tonnes to
                    the atmosphere, but the net flux to the atmosphere in  1989 associated with
                    land clearing would be 45 tonnes of carbon as CO2- The 1990 flux would be
                    the same since now the original one hectare of pasture would have reached
                    a new steady state as a secondary forest
                    Many variations on this example can be devised: e.g., conversion of some
                    vegetation to charcoal, varying deforestation and  regrowth rates. For
                    instance, if the  land clearing rates declined  over the time period, the 1990
                    net flux could easily be from the atmosphere to the biosphere even though
                    the net integral flux over the time period was to the atmosphere.
                    There are other complexities such as the variety of land-use practices,
                    varying assumptions about biomass densities, recovery rates, the dynamics of
                    the associated litter and soil pools, and so forth. However, the net flux to or
                    from a particular site will always be reflected in the change of carbon stocks
                    on site and/or in the products pools associated with the site. Thus, a
                    methodology that determines  carbon stock changes, also provides estimates
                    of the net fluxes of CO2-
PART 2
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LAND  USE CHANGE  &  FORESTRY
                        This characteristic that changes in land use activity today affects both present and future
                        CO2 fluxes associated with that specific land use activity is one feature of CO2 emissions
                        analysis that distinguishes land use from fossil fuel consumption. Consequently, when one
                        considers the issue of CO2 flux associated with land use today or in a ba'se year, one must
                        consider past land use activities and their effects upon current fluxes of CO2. Box I
                        provides some illustrative numerical examples of carbon fluxes associated with land use
                        change over a series of years.


                        5.1.2  The  Proposed  Approach

                        The fundamental basis for the methodology rests upon  two linked themes: i) the flux of
                        CO2 to or from the atmosphere are assumed to be equal to changes in carbon stocks  in
                        existing biomass and soils, and ii) changes in carbon stocks can be estimated by first
                        establishing rates of change in land use and then applying simple assumptions about the
                        biological response to a given land use. As noted above, there are large uncertainties in all
                        current methods for estimating fluxes of CO2 from forestry and land use change. Direct
                        measurements of changes in carbon stocks are extremely difficult since one must confront
                        the difficulty of determining small differences in large numbers as well as the inherent
                         heterogeneity of terrestrial systems. A more practical first order approach in many
                         countries is to make simple assumptions about the effects of land use change on carbon
                         stocks and the biological response and to use these assumptions to calculate carbon stock
                         changes and hence the CO2 flux. This observation is at the heart of the proposed g
                         approach. It is also central to more complex terrestrial carbon accounting models.
                         Rates of change of land use are also difficult to establish. However, on a practical basis it is
                         possible since there are a variety of data on which to base land use change estimates. The
                         Technical Appendix to this chapter reviews sources of data on rates of tropical
                         deforestation, the land use change which currently makes the largest contribution to CO2
                         flux. Finally, the assumptions regarding the response of vegetation and soils to different
                         land uses and land  use change can be expressed in uncomplicated terms which can be
                         altered for particular differences for different countries.
                         The methodology is designed to allow calculations based on such assumptions.which cover
                         each of the main categories, and which are feasible for all participating countries. It can be
                         implemented at several different levels of complexity and geographic scale, depending  on
                         the needs and capabilities of national experts in different countries.
                          I     A simple, first order approach can be based on very aggregate default data and
                               assumptions, derived from the technical literature, and provided throughout the
                               text. Methods are presented in the context of national level aggregate calculations
                               for a limited set of subcategories which can be supported by these default values.

                         2    A more accurate level can be achieved simply by substituting country-specific valued
                               for general defaults provided in the methodlogy. If appropriate and possible, locally
                               available data can be used to carry out calculations at a more detailed geographic
                               and/or sub-category level. Alternative levels of detail are discussed more fully in the
                                next section. National experts are strongly encouraged to substitute more
                               appropriate (i.e., country or region-specific) and more detailed input data wherever
                               this is available.
                          3     Forest inventory data can also be used with this methodlogy. It is important to note
                                that some countries with highly developed  forestry industries do in fact keep track
                                of existing commercial forests through periodic detailed surveys. In these countries
                                it is generally the ongoing management of existing forests rather than land use
                                changes which has the greatest impact on GHG emissions or removals. National
  5.6

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                                                               LAND  USE CHANGE  &  FORESTRY
                  experts who have very detailed, inventory based data, can reformat this data to
                  create equivalent average responses (e.g., annual biomass growth rates by ecosystem
                  type) which can be aggregated up to categories matching the simple approach
                  outlined here. This procedure is discussed in more detail in the managed forests
                  section below.

             The intent is to provide a calculation and reporting framework which can accommodate
             users with vastly different levels of data available, yet allow them all to place the results on
             a comparable basis.
             5.1.3  Priority  Categories

             In estimating the effects of land use and land use changes on the concentration of
             greenhouse gases, it is reasonable to stage the calculation methods so that the most
             important components can be addressed first, and complexities and subtleties of the
             relationship of forestry and land use change to fluxes of CO2 and other gases can be
             incorporated in a consistent manner into subsequent calculations as knowledge advances
             and data improve. The methodology presented in this chapter focuses initially on a simple,
             practical, and fair procedure for determining the carbon dioxide flux directly attributed to
             forest management and land use change activities. This procedure must account for the
             influence of past land use changes upon the contemporary flux.  The method also
             accounts for trace gas emissions from biomass burning where this occurs in conjunction
             with land use change.
             On a global scale, the most important land use changes thai: result in CO2 emissions and
             removals are:
             •   forest clearing - the conversion of forests to non-forests (e.g., to pasture or
                 cropland)10
             •   grassland conversion - the conversion of natural grasslands to cultivated (tilled) or
                 pasture lands
             •   abandonment of managed lands which regrow into grasslands or forests
             •   managed forests - the most important effects of human interactions with existing
                 forests are considered in a single broad category , which includes logging for forest
                 products, the harvest of fuel wood, and establihment and operation of forest
                  plantations.
             The method also addresses the immediate release of non-CO2 trace gases (CH4, CO,
             N2O and NOx) from the open burning of biomass from forest clearing. The approach is
             essentially the same as that used for non-CO2 trace gases from all burning of unprocessed
             biomass, such as burning of traditional biomass fuels (Chapter  I: Energy), and burning of
             agricultural residues and savanna burning (Chapter 4: Agriculture). These calculations are
             similar to fossil fuel emission calculations, in that they do not include time lags and all
             emissions are net emissions.
             5.1.4  Relationships  Among Categories

             It is important to recognize some key linkages and interactions among components of the
             land use change and forestry methods and with other calculations discussed in other
             chapters. Figure I  illustrates a number of complicated relationships among these
             categories and also with biomass fuel combustion which is covered in the energy source
             category. Key linkages which should be understood are:
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LAND  USE CHANGE &  FORESTRY
                       I    To estimate CO2 emissions from burning or cleared forests, it is only necessary to
                           know the total amount of biomass which is burned in the inventor/ year.

                       2   However, it is necessary to divide this burning into on-site and off-site (fuelwood)
                           portions for other reasons:
                           First, the type of burning affects the emissions of non-CO2 trace gases such as
                           methane so that different emission  factors may be applied to open burning on-site
                           and to fuelwood use off-site.
                           Secondly, the amount of fuelwood  removed from cleared forests must be deducted
                           from total fuelwood consumed for the nation or region to determine the residual
                           amount of fuelwood which must have been harvested from managed forests (as
                           broadly defined in this chapter). This  is only an issue for those countries which must
                           infer some or all of forest harvest from wood consumption surveys. If some of the
                           fuelwood consumed has already been accounted for once in  calculations of forest
                           clearing, this amount must be take  out of the amount attributed to managed forests.

                       3    Fuelwood Consumption Information. Countries which have accurate and  complete
                            statistics on direct harvesting of all types of wood from managed forests, and all uses
                            of biomass for fuel, should use locally available data.  Many countries,  however, have
                            significant amounts of wood removed from forests, primarily for domestic fuel use,
                            which is not accounted for in commercial harvest statistics. For these countries, an
                            optional Fuelwood Consumption Accounting approach is provided. This approach  is
                            based on household and other fuel consumption surveys, scaled to population to
                            estimate total annual demand for fuelwood and other fuels. This information can then
                            be used instead of, or in combination with, commercial harvest and sales statistics.

                            Fuelwood consumption  information is used in two ways:
                            —   for estimating trace gas emissions from  biomass fuel combustion (in the Energy
                                section of the methodology); and
                            —   total wood consumption, corrected to deduct any wood which has come from
                                forest clearing (for which CO2 is already accounted) is also a key input to the
                                 calculations of net  CO2 emissions or removals by managed forests.
 5.8


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                                                                   LAND  USE  CHANGE  &  FORESTRY
              FIGURE I: Relationships Among Categories
   L
   A
   N
   D

   U
   S
   E

   C
   H
   A
   N
   G
   E
   F
   O
   R
   E
   S
   T
   R
   Y
   E
   N
   E
   R
   G
   Y
Forest Clearing
immediate Release from Burning
Delayed Release from Decay (10 yrs)
Delayed Release from Soils (25 yrs)
Total

 C
                                          On-site burning
                                         Off-site (field)
                                                             Trace Gas Emissions
                                                             from Open Burning
                                           7
 Abandoned Land Regrowing
            Grassland Conversion
                         Total
                       Fuelwood
                       Demand
     Fuelwood Consumption
     Accounting (Optional)
                                                                                  ^, CO2 N2O and NO* Emissions
                                                                                CO  Emissions
                                                                                     Removals
                                               Quantity of
                                                                                       ->-CO2 Emissions
                                    Minus Quantity from
                                      Cleared Forests
                                              Net CC>2 Emissions or Removals
       Trace Gas Emissions from
       Biomass Fuel Combustion
Emissions
              5.1.5  Chapter  Organization

              The remainder of this chapter presents methods for calcubting greenhouse gases from •
              land use change and forestry in two stages. The next section, Bask Calculations, presents
              initial simple calculations for each of the four key land uses and changes in land use
              identified above. These categories also correspond directly to the subsections of the Land
              Use Change and Forestry Module of Volume 2: Workbook.

              The second stage, Refinements in Calculations, discusses a range of complexities and
              refinements which ideally could be included in such calculations, as data and understanding
              permit, in order to improve accuracy and completeness. These possible refinements
              include more detailed treatment of some aspects of the basic categories of land uses and
              land use changes, as well as additional  categories, which cam affect carbon stocks and are
              potentially important for other greenhouse gases. Issues discussed include the delayed
              releases (or uptake) of non-CO2 trace gases after burning of forests (either as a
              prescribed forest management tool or as a means of land-clearing), forest degradation,
              traditional shifting cultivation, and conversion of wetlands to other land uses or the
              reverse. These activities and other refinements can be incorporated in more detailed
              versions of the calculations.

              A Technical Appendix, as mentioned, is also provided, which deals with sources of
              information on rates of land use change, a critical activity data input for calculating GHG
              emissions.
PART  2
                                                                                                               5.9

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LAND USE  CHANGE  &  FORESTRY
              5.2    Basic Calculations
                       5.2.1   Introduction

                       The basic calculations focus primarily on the flux of CO2 and the land use changes and land
                       use activities that result in the largest, potential flux of CO2 to the atmosphere or have
                       the largest potential for sequestering carbon.

                       Three categories of land use change are considered:

                       •    forest clearing
                       •    conversion of grasslands to agricultural lands
                       •    abandonment of managed lands
                       In contrast to other aspects of the greenhouse gas emissions methodology, the estimation
                       of CO2 from land use change requires the consideration of historic time horizons. When
                       forests are cleared or agricultural lands abandoned, the biological responses result in
                       "commitments" of fluxes of carbon to or from the atmosphere for many years after the
                       land use change. This methodology is designed to produce an emissions estimate that is
                       comparable to other elements of the inventory, fossil fuel emissions, for example. That is,
                       it attempts to quantify the flux to or from the atmosphere in the inventory year. To do this,
                       it is necessary to obtain estimates of land use change activities for many years prior to the
                       inventory year, and estimate the effects of these activities on the current year fluxes. The
                       three selected categories are considered to be the most important land use changes
                       affecting CO2 fluxes, but are not a comprehensive set. Many relevant land use changes are
                       excluded from the basic calculations. These are discussed in the last section of this
                       chapter.
                        Relevant forestry (ongoing land use) activity is combined in one very broad category,
                        managed forests, which is defined here to include potentially a wide variety of land use
                        practices. Key examples are establishing and harvesting plantations, commercial forest
                        management and harvesting, and fuelwood gathering. Conceptually, this category is
                        intended to account for all significant human interactions with forests which affect CO2
                        fluxes to and from the atmosphere. It is intended to account, at least on a crude level, for
                        all existing forests, with two exceptions.
                        I     Natural, undisturbed forests, are not considered to be either an anthropogenic
                             source or sink, and  are excluded from the calculations entirely.
                        2    Forests regrowing naturally on abandoned lands are a net carbon sink attributable to
                             past human activities and are accounted for separately. "Abandoned" lands are by
                             definition assumed not to be subject to ongoing human intervention (of significance
                             to  carbon stocks) after abandonment
                        Several simplifying assumptions are made in the basic calculation methodology. A number
                        of refinements and removals of simplifying assumptions are possible to improve on the
                        basic calculation. One important option is to implement the basic calculations at a more
                        detailed level of subcategories or spatial detail. National experts are strongly  encouraged
                        to do so if data are available. Box 2 discusses possibilities for adapting the methodology to
                        various  levels of detail, depending on the capabilities and data available to the user, and the
                        relative importance of various components to the individual country.
                        Other possibilities for improving the accuracy and completeness of the basic  calculations
                        are possible. For example, the fate and amount of belowground biomass (roots, etc.) is
                        currently ignored in the  calculation. The section titled: Refinements to Calculations, later
                        in this chapter, reviews a number of possible additions and refinements.
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                                                                 LAND  USE  CHANGE  &  FORESTRY
                                                   Box 2
                                      ALTERNATIVE LEVELS OF DETAIL

                   For simplicity and clarity, this chapter discusses calculation of emissions from
                   at a national level and for a relatively few sub-categories within each
                   category of land use changes and forestry. The level of detail in the sub-
                   categories is designed to match the available sources of default input data,
                   carbon contents and other assumptions. It is important, however, for users
                   of these emissions methodology guidelines to understand that they are not
                   only permitted but encouraged to carry out the GHG emissions inventory
                   calculations at a finer level of detail, if possible. Many countries have more
                   detailed information available about land use change, forests and agriculture,
                   than was used in constructing default values here. It may be important in
                   such countries to carry out emissions calculations at finer levels in two ways:

                    I    Geographic detail finer than the nation as a whole
                        If data are available, experts may find that GHG! estimation for various
                        regions within a country are necessary to capture important geographic
                        variations in ecosystem types, biomass densities, agricultural practices,
                        rates of burning, etc.
                    2   Finer detail by sub-category
                        If data are available, experts may subdivide the recommended activity
                        categories and sub-categories to reflect  important differences in
                        ecology or species, land  use or agricultural practices, bioenergy
                        consumption patterns, etc.
                    In all cases, working at finer levels of disaggregation, does not change the
                    basic nature of the calculations, although, additional data and assumptions
                    will generally be required beyond the defaults provided in the chapter. Once
                    GHG  emissions have been calculated at whatever is determined by the
                    national experts to be the most appropriate level of detail, results should
                    also be aggregated up to the national level and the standard categories
                    requested in the IPCC proposed methodology.  This will allow for
                    comparability of results  among all participating countries. Generally, the data
                    and assumptions used for finer levels of detail should also be reported to the
                    IPCC  to ensure transparency and replicability of methods. Volume I:
                    Reporting Instructions discusses these issues in  more detail.
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                       5.2.2 Forest  Clearing:  CO2  Release
                       Background

                       The calculation of carbon fluxes due to forest clearing is in many ways the most complex
                       of the emissions inventory components. Because of the delayed responses of biological
                       systems, it is necessary to consider forest clearing activity over three different historic
                       time horizons and to sum the results to estimate the total flux in the current year. Also, as
                       with all categories of forest management and land use change activity, it is necessary to
                       determine net C02 flux.
                       Forests can be cleared to convert land to a wide variety of other uses, including
                       agriculture, highways, urban development, etc.  In all cases there is a net carbon release
                       to the atmosphere which should be accounted for in this calculation. The predominant
                       current cause of forest clearing is conversion to pasture and cropland in the tropics. This
                       is accomplished by an initial cutting of undergrowth and felling of trees. The biomass may
                       then be combusted in a series of on-site burns or taken off site to be burned as fuel, or
                       perhaps used for forest products. A portion of the biomass remaining on site as slash is
                       not actually combusted and remains on the ground where it decays slowly.   Some of the
                       decay of remaining carbon left on the ground is  probably accomplished by termites, which
                       produce both CO2 and CH4.14  However, the methane release from cleared, unburned
                       biomass is very difficult to quantify and ignored for purposes of the basic calculation,
                       where all of the carbon in biomass which decays is assumed to be released as CO2. Of the
                       portion burned on site, a small fraction of the carbon remains as charcoal,   which  resists
                       decay for well over  100 years or more; the remainder is released  instantaneously to the
                       atmosphere.16 For biomass removed for fuelwood, the fate is very similar. A small  fraction
                       of the carbon remains in ash which effectively provides long term  storage, while the
                       majority of the carbon is released to the atmosphere.
                        Forest conversion also results in CO2 emissions through soil  disturbance, particularly
                       when the conversion is to cultivated or tilled lands. When forests are converted to
                        croplands, a fraction17 of the  soil carbon may be released as CO2, primarily through
                        oxidation of organic matter. This can be a long term process  which continues for many
                       years after the land  use change occurs. The basic calculations allow for estimation  of loss
                        in soil carbon due to forest clearing. Because of the uncertainty in current understanding
                        of this component, and the difficult historic data requirements, the users are encouraged
                        to exercise their own judgement as to whether or not to include this  calculation in the
                        basic estimates.

                        Calculations
                        Emissions of CO2 due to forest clearing are calculated through a sequence of easy  steps
                        treating:
                        •    the net change in aboveground biomass carbon

                        •    the portion of this change that is burned in the first year versus the amount left to
                             decay over a longer time period
                        •    for the burned portion, loss to the atmosphere versus long term storage in ash

                        •    current emissions from decay of biomass cleared over the previous decade

                        •    if estimated, current releases of carbon from soils due to clearing over the previous
                             25 years
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                                                                 LAND  USE  CHANGE  &  FORESTRY
                                                                                      18 .
Net change in aboveground biomass
First, the amount of biomass affected by clearing in the emissions inventory year"' is
calculated by multiplying the annual forest area converted to pasture or cropland or other
land uses by the net change in aboveground biomass. This calculation is carried out for
each relevant forest type and, if appropriate, by region within a country.   The net change
is the difference between the density (t dm/ha) of aboveground biomass on that forest
land prior to conversion, and the density of aboveground living biomass (t dm/ha)
remaining as living vegetation, after clearing. The after clearing value includes the biomass
that regrows on the land in the year after clearing and any original biomass which was not
completely cleared.
Tables I and 2 provide a range of values for aboveground biomass in forests prior to
clearing, which can be used as default data if more appropriate and accurate data are not
available in a given country.  For aboveground biomass after clearing, it is necessary to
account for any vegetation (i.e., crops or pasture) that replaces the vegetation that was
cleared. A reasonable figure for crops or grasslands is 10 tonnes of dry biomass per
hectare.21 The recommended default assumption is that all of the original aboveground
biomass is destroyed during clearing. If locally available data indicate that some fraction of
the original biomass is left living after clearing, this should be added to the after clearing
value.
To arrive at net change, one reduces the gross release from land clearing in a given base
year by 10 tonnes dry biomass (or some other value if more  accurate information is
available) for each hectare  cleared. The total affected  biomsiss for a given  year can be
calculated from the total area cleared (by region and type) and multiplied by the  net
change in living on site biomass (including regrowth). This provides an estimate of the total
affected biomass for the time period in question.

Immediate emissions from burning

The biomass that is cleared has one of three immediate fates:
 I    a portion may be burned on site;
2   a portion may be removed from the cleared site and used as fuelwood, or for
     products;
3   a portion is converted to slash  and decays on site to carbon dioxide over a decade or
     so. Some estimates in the literature suggest that a global average of about 50% of the
     cleared forests are burned in the first year with  the remaining 50% left to decay.
     This value could be used as a default for first order calculations if the user does not
     have access to more  appropriate local information. It is important to recognize that
     this average is dominated by practices in Latin America  which has the largest current
     rates of deforestation. There are certainly wide variations in burning practices in
     different regions. To  calculate the gross amount of carbon released in the current
     year to the atmosphere it is necessary to consider the: burned portions and the
     decaying portion over different time horizons.
To estimate the CO2 released by the burning of cleared aboveground vegetation, estimate
a) the fraction of the affected biomass that is subjected to burning (on and  off site - the
 remaining, disturbed biomass is slash) and b) the fraction of the burned biomass that is
 oxidized. The fraction of burned biomass which does not oxidize remains as charcoal.
The amount of biomass oxidized is converted to carbon units to estimate the carbon
 dioxide flux from burning.24 A reasonable average for converting from dry biomass to
 carbon content is to multiply dry biomass by 0.45.    Of the portion  of cleared biomass
 which is burned, some of this may be burned in the field to- facilitate clearing, and some
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LAND USE CHANGE &  FORESTRY
                        may be removed and used as fuel. The portion which is burned in the field is used
                        subsequently for calculating the trace gas emissions from open burning of cleared forests,
                        in the next section. The amount removed for fuel is important for calculations of fuel
                        wood extracted from managed forests in the last component of these basic calculations.

                        Emissions from decay
                        The aboveground biomass which remained on site but was not burned will oxidize in
                        roughly a decade, and this historical release associated with land clearing must be
                        considered. The 10 year period is a recommended default value, as a reasonable historical
                        horizon in light of the twin realities of data availability and  biological dynamics.   This can
                        be varied if the user has data or a strong rationale to suggest that a longer or shorter
                        average decay time is more representative of local conditions. The  "committed" flux
                        calculation simply accounts for the current oxidizing of material left unburned during the
                        specified historic decay period.
                        The decay phenomenon can be simply characterized for emissions  estimation purposes.
                        Each year, some portion of the cleared aboveground biomass is left as slash, and we
                        assume that 10% of this decomposes each year. Therefore, the total carbon being released
                        to the atmosphere in the inventory year is a function of the land clearing rate for each of
                        the past 10 years, and the portion of the aboveground carbon remaining on site but not
                        combusted each year. The current year emissions from  decay of biomass cleared in a
                        historic year would be 10% of the total  decay. The total current emissions from decay of
                        historically cleared biomass would then be the sum of the current estimated emissions
                        from biomass cleared in each of the ten historic years.

                        For practical purposes, the methodology recommends working with decadal average
                        values for the land clearing and portion  left to decay which can then simplify the
                        calculation. Working with average values, one would in theory divide the total emissions
                        from decay by 10 to get the contribution of one "average" historic year's clearing to
                        current emissions, then multiply by  10 to account for ten  historic years' clearing which
                        could be expected to affect current emissions. Obviously  the division by 10 and
                        multiplication by 10 cancel each other and can be ignored. Therefore, the flux in the
                        inventory year from historic land clearing of the aboveground vegetation is simply is
                        expressed in Equation 5.1.
                                                          EQUATION 5.1
                                             average annual land clearing over the period
                                 x the average quantity of aboveground biomass per hectare remaining on
                                  site as slash but not burned (either oxidized or converted to charcoal)
                                                  x carbon content of dry biomass
                                 flux in the inventory year from historic land clearing of the aboveground
                                                            vegetation
                         Soil carbon release
                         For calculating the annual CO2 flux associated with the loss of soil carbon following forest
                         clearing, the methodology is essentially the same as the approach for treating the historic
                         flux from slash. The time horizon suggested is twenty five years. The historic release from
                         soils is simply the average annual land clearing times the change in carbon stock in soil
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                                                                 LAND  USE  CHANGE  &  FORESTRY
             between the original forest and a twenty five year old pasture or crop land. For simplicity,
             it is assumed that the soil carbon release is linear over the 2ij year period.

             The annual rate of soil carbon loss would be total change in soil carbon from before
             clearing levels to the final level divided by 25. Some evidence exists that roughly 50% of
             soil carbon is lost over twenty-five years after temperate and boreal forest are converted
             to cultivated soil.28 This value, although highly uncertain, could be used as a default for
             initial calculations, if more accurate information or measurements are not available to
             users. This would imply that the annual rate of soil carbon los would be 2% (50%/25
             years).
             The contemporary flux associated with past land use could be calculated by multiplying the
             number of hectares of land converted in each of the previous 25 years by the annual per
             hectare loss  in soil  carbon and summing. Alternatively, the average annual historic
             conversion rate over a twenty-five year period could be multiplied by the annual loss rate
             times twenty-five. The average rate of conversion is simply the total hectares converted
             over the period divided by 25 years.
             It is an open question if the conversion of tropical forests to pasture results in loss of soil
             carbon as  CO2.29  Pending resolution of the scientific debate on this issue, it is left to the
             judgement of users whether or not to include this component in the calculations, and
             what values to use for the portion of carbon lost. Tables 3 and 4 provide average values
             for soil carbon in undisturbed tropical, temperate, and boreal systems.
             As with emissions from decay of aboveground biomass, the recommendation is to use
             average values for the rate of land clearing, soil  carbon content and portion of soil carbon
             lost over time. Again, for the same reason, the theoretical requirement to multiply and
             divide by 25 cancel. The calculation of current emissions (from soils in forest cleared over
             25 years) is expressed in Equation 5.2.
                                                EQUATION 5.2

                              the average annual clearing rate over the last 25 years

                     x change in soil carbon between a forest system and a 25 year old pasture
                                                or crop land.


                           current emissions (from soils in forest cleared over 25 years)
              The estimate of the total carbon released in the inventory year from current and historic
              clearing is calculated by summing the current year release of carbon due to burning - on
              site or as fuelwood, the average long-term annual release of carbon from decay of biomass
              cleared over the base decade, and, if estimated, the current year release of soil carbon due
              to land clearing over the previous 25 years.

              Burning of Cleared Forests: Non-CO2 Trace gases

              Where there is open burning associated with forest clearing;, it is important to estimate
              the emissions of methane (CH4), carbon monoxide (CO), nitrous oxide (N2O), and oxides
              of nitrogen (NOX, i.e., NO + NO2). The approach is essentially the same as that used for
              non-CO2 trace gases for all burning of unprocessed biomass, including traditional biomass
              fuels, savanna burning and field burning of crop residues. For all these activities there is a
              common approach in the proposed methodology in that crude estimates of trace gas
              emissions can be based on ratios to the total carbon released by burning. The carbon
              trace gas releases (CH4 and CO) are treated as direct ratio;; to total carbon released. To
              handle nitrogen trace gases, ratios of nitrogen to carbon in biomass are used to derive
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LAND USE  CHANGE & FORESTRY
                        total nitrogen released from burning, and then emissions of N2O and NOX are based on
                        ratios to total nitrogen release. Table 7 provides suggested default values for trace gas
                        emission ratios.30  These are presented with ranges which emphasize their uncertainty.
                        However, the basic calculation methodology requires that users select a best estimate
                        value.31
                        In sum, clearing by burning releases other gases in addition to CO2 which are by-products
                        of incomplete combustion: methane, carbon monoxide, nitrous oxide, and oxides of
                        nitrogen, among others. Unlike CO2 emissions from land clearing, which may or may not
                        imply a net release of CO2 to the atmosphere (depending on whether or not the
                        vegetation is allowed to regrow), emissions of these other gases from biomass burning are
                        net transfers from the biosphere to the atmosphere. The calculations described here
                        ignore the contemporary releases associated with past burning events. These delayed
                        releases are known to exist, but are sufficiently uncertain that they should be ignored at
                        present. This and  other possible refinements to the calculations are discussed in the last
                        section.
                        All of the crude biomass burning calculations have two components: I) estimating total
                        carbon released, and 2) applying emission ratios to estimate emissions of the non-CO2
                        trace gases. In the case of burning of cleared forests, part I has been carried out in the
                        previous section which included the estimation of carbon emissions from the portion of
                        cleared forests which is burned on site in inventory year. The total carbon release from
                        this on site burning (not including any carbon released from decay or soils) provides the
                        basis for the inventory year release of non-CO2 trace gases. To complete the calculations,
                        it is necessary only to add part 2 of the calculation — the release of non-CO2 trace gases
                        from current burning.
                        Once the total carbon released from on site burning of cleared forests has been
                        estimated, the emissions of CH4, CO, N2O, and NOX can be calculated.32 The total carbon
                        released due to burning is multiplied by the emission ratios of CH4 and CO relative to
                        emissions of total carbon to yield total emissions of CH, and CO (each expressed  in units
                        of C). The emissions of CH4 and CO are multiplied by 16112 and 28/12, respectively, to
                        convert to full  molecular weights.
                        To calculate emissions of N2O and NOX, first the total carbon released is multiplied by the
                         estimated N/C ratio of the fuel by weight (0.01 is a general default value for this category
                         of fuel33) to yield the total amount of nitrogen (N) released. The total N released is then
                         multiplied by the ratios of emissions of N2O and NOX relative to the total N released of
                         the fuel  to yield emissions of N2O and NOX (expressed in units of N). To convert to full
                         molecular weights, the emissions of N2O and NOX are multiplied by 44/28 and 30/14,
                         respectively.
                         The trace gas emissions from burning calculation are summarized as follows:

                         •    CH, Emissions = (carbon released) x (emission ratio) x 16/12

                         •    CO Emissions = (carbon released) x (emission ratio) x 28/12

                         •    N2O Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 44/28

                         •    NOX Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 30/14

                         Conversion of Grasslands to Cultivated or Pasture Lands
                         Conversion of a  grassland to cultivated land could result in net CO2 emissions to die
                         atmosphere due to soil disturbance and resultant oxidation of soil carbon even if there is
                         no net reduction in standing biomass. The carbon density in the aboveground vegetation in
                         grasslands is approximately the same as the annual average aboveground biomass in crops
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                                                                  LAND  USE  CHANGE &  FORESTRY
              or pasture, and therefore any change in this aboveground pool due to the land use change
              is generally small in comparison to other changes in carbon stocks in terrestrial systems.
              Consequently, changes in aboveground biomass are ignored in the basic calculation. Thus,
              this calculation focuses on the change of carbon in soils. The currently available
              information relates primarily to the temperate zone, where there is evidence that perhaps
              50% of the soil carbon in the active layer (roughly the top one meter) has been lost over
              roughly a SO year period, with most of this loss occurring in the first 25 years. The loss
              tends to be exponential. In some agricultural systems, there has been an accumulation of
              carbon rather than a loss.   The actual rate of soil carbon loss in a specific area of
              agricultural land, is a function of the specific agricultural use and management practices as
              discussed in the refinements section of this chapter. There  is evidence that, in some cases,
              the conversion of grasslands to  cultivated lands has actually increased carbon stocks in
              certain systems. However, data and scientific understanding are not sufficient to include a
              simple methodology for characterizing these relationships in the current basic calculations.
              Data on changes in soil carbon in  tropical systems are sparse. Therefore, no default
              assumptions can be provided for this region. In the initial application of basic calculations,
              grassland conversion can be ignored for tropical countries unless the user has access to
              data on the rate of soil carbon loss (or accumulation) after this land use change. This is an
              important research issue, as discussed in the refinements section of this chapter.  As a
              result, in the initial application of the basic calculations  to the land use change of
              converting grasslands to cultivated lands, default values are  recommended only for changes
              in the soil carbon pool in temperate grassland systems. The simple  calculation structure
              would be the same for tropical  systems but the use of  available default assumptions and
              values (based on temperate systems) is not recommended.
              For calculating the carbon flux from this land use change, a twenty-five year time  horizon
              is suggested. The annual rate of soil carbon loss would be total change in soil carbon from
              before conversion levels to the final level  divided by 25. Soil carbon contents of natural
              grasslands are highly variable and should be evaluated based on locally available data if
              possible. Very crude general default values are 60 tonnes/ha for tropical systems  and 70
              tonnes/ha for temperate systems.   As noted above, there is some evidence that 50% of
              soil carbon is lost over twenty-five years after temperate grasslands are converted to
              cultivated  soil.   This value could be used as a default for initial calculations, if more
              accurate information or measurements are not available to users. This would imply that
              the annual rate of soil carbon loss would be 2% (50%/25 yeairs).
              As with soil carbon emissions from forest clearing above, the recommendation is to use
              average values for the rate of land conversion, soil carbon content  and portion of soil
              carbon lost over time. Again, for the same reason, the theoretical requirement to multiply
              and divide by 25 cancel. Therefore the calculation is expressed in Equation 5.3.
                                                 EQUATION 5.3
                             average annual land conversion rate over the last 25 years
                        x change in soil carbon between a grassland system and a 25 year old
                                              pasture or crop land.


                       carbon flux from conversion of grasslands to cultivated or pasture Lands
              For emissions from grasslands used for pasture one needs before and after estimates of
              biomass and soil carbon applied in the above methodology. This category may prove to be
              important in certain grasslands that are being grazed heavily or burned often.
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LAND USE  CHANGE  &  FORESTRY
                       Abandonment of Managed Lands
                       If managed lands, e.g., croplands and pastures, are abandoned, carbon may re-accumulate
                       on the land and in the soil. The response of these converted systems to abandonment
                       depends upon a complex suite of issues including soil type, length of time in pasture or
                       cultivation, and the type of original ecosystem. It may be that some of the abandoned
                       agricultural lands are too infertile, saline, or eroded for regrowth to occur. In this case,
                       either the land remains in its current state or it may further degrade and  lose additional
                       organic material (i.e., carbon in the biomass and  the soils). Therefore, to calculate changes
                       in carbon flux from this activity, the area abandoned should first be split into parts: lands
                       that re-accumulate carbon naturally, and those that do not or perhaps even continue to
                       degrade.
                       In the basic calculation, only those that begin to  return to an approximation of their
                       previous natural state are considered. Those that remain constant with respect to carbon
                       "ox can be ignored. Likewise, the CO2 flux to the atmosphere for those  lands that
                       continue to degrade is likely to be small and hence can also be ignored in the initial
                       application of basic calculations. In any event, the issue could be considered in a more
                        refined calculation.
                       Abandoned lands must be evaluated in the context of the various natural ecosystems
                        originally occupying them. In addition, the effect of previous patterns of abandonment
                        should be considered while recognizing the desire for simplicity and practicality. The
                        process of recovery of aboveground biomass generally is slower than the human-induced
                        oxidation of biomass. With this in mind and in consideration of possible data sources it is
                        recommended that abandoned lands be evaluated in two time horizons. A twenty year
                        historical time horizon is suggested to capture the more rapid growth expected after
                        abandonment. A second time period - 20 years after abandonment up to roughly 100
                        years — may be considered if data are available.
                        The calculation, by original ecosystem (e.g., closed broadleaf forest, open forest, grassland)
                        is straightforward.
                        The total area abandoned (total over the previous 20 years including the inventory year) is
                        multiplied by
                         I    the average annual uptake of carbon in the aboveground biomass, and

                        2    the average annual uptake of carbon in the soils.
                        Results of these two calculations are summed to yield the current uptake of carbon due to
                        abandonment over the previous 20 years of managed lands that are naturally regenerating
                        to forests or grasslands.
                        If land use data are available to support calculations over a longer time horizon, national
                        experts may want to consider adding a pool of forests and grasslands that are regrowing
                        from abandonment that occurred more than 20 years ago. The growth rates of
                        aboveground biomass in these forests would be slower than that of forests  regrowing
                        from abandonment that occurred less than 20 years ago. The same calculations can be
                         repeated for lands abandoned more for than 20 years and  up to about 100 years prior to
                         the inventory year.
                         Table 5 presents estimates of average annual aboveground biomass accumulation in
                         vegetation in various regrowing forest ecosystems following abandonment of cultivated
                         land or pasture.38 These general growth rates, averaged over large regions and many
                         specific ecosystem types, should be considered crude approximations as applied to the
                         particular lands regrowing in a given region or  country. If more accurate data on these
                         growth rates are locally available, they should be used. Accumulation of aboveground dry
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                                                                  LAND USE  CHANGE &  FORESTRY
              biomass can be converted to carbon using a general default conversion value for live
              biomass — 0.45 t-C/t dm.

              If lands are regenerating to grassland, then only the soil pool needs to be considered.
              Default rates of soil carbon uptake for both forests and grasslands can be derived from the
              expected sbil carbon values for fully restored natural systems and some simple
              assumptions. In temperate and boreal systems it can be assumed that soil carbon
              accumulates linearly from  some base value (e.g., 50-75% of original stocks) Table 4
              provides default soil carbon values for temperate systems. Values for tropical systems are
              provided in Table 3, and crude defaults for grasslands were provided in the previous
              section (60 t-C/ha tropical, 70 t-C/has temperate). Soil carbon changes in tropical systems
              are poorly understood and can be included or ignored in basic calculations at the
              discretion of national experts.

              The base value at the start of the reaccumulation process in soils would depend on the
              average amount of time that cleared lands had been used for agricultural purposes (and
              the management practices utilized during the agricultural period) before abandonment.
              Based on the simple default assumptions for soil carbon losses from forest clearing one
              could calculate the level to which soil carbon would have fa.llen during the agricultural use
              period. The default assumption was that after 25 years, soil carbon would have fallen to
              50% of the pre-clearing value (i.e., 2% per year linear average change). For example, if the
              average agricultural use period was 10 years before abandonment, it could be assumed
              that the base value in soils would be 80% of original values. It could be assumed that soil
              carbon is restored at roughly the same rate at which it is lost under cultivation. Available
              evidence is that the recovery is not this fast in reality. In this forest clearing calculations the
              default assumption is that  soil carbon might be lost at an average rate of 2 percent of the
              original carbon content per year. If no detailed information is available, a default
              assumption could be that the soil accumulation occurs linearly  roughly one-half this rate
              after abandonment. This procedure was  used to derive the values  presented in the
              Workbook. The values given are 1.3 tonnes C/year for temperate evergreen and deciduous
              forest soils and 2.0 tonnes C/year for boreal forests. These are one percent  of the values
              from table 4 for soil carbon in primary forests. This is an important area for further
              research.
              Managed Forests

              The category managed forests as used in these basic calculations is very broad, potentially
              including a wide variety of land use practices. A basic organizing concept in this chapter is
              that all existing forests can be allocated into one of three categories.

              I     Natural, undisturbed forests, where they still exist are in balance and should not be
                   considered either an anthropogenic source or sink. They are therefore excluded
                   form national inventory calculations.

              2    Forests regrowing naturally on abandoned lands are a net carbon sink attributable to
                   past human activities and are accounted for as discussed in the previous section.
                   While the  current regrowth is considered a response to past anthropogenic activity,
                   "abandoned" lands are by definition assumed not to be subject to ongoing human
                   intervention  (of significance to carbon stocks) after abandonment.

              3    Managed Forests are considered to include all other types of forest That is any forest
                   which experiences periodic or on-going human  interventions that affect carbon
                   stocks would ideally be included here. In the basic calculations, the chapter focuses
                   primarily on  a few types of human interactions with forests which are believed to
                   result in the  most significant fluxes of carbon. National experts are encouraged,
                   however, to  estimate emissions for any activity  related to managed forests which is
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LAND  USE CHANGE  &  FORESTRY
                             considered to result in significant carbon emissions or removals, and for which
                             necessary data are available. Any such activities falling within our broad definition of
                             managed forests should be included in this category and reported to the IPCC as
                             discussed in Volume I: Reporting Instructions.

                        Some of the activities in the managed forests category which can potentially produce
                        significant carbon fluxes are:
                        •    management of commercial forests - including logging, restocking, selective thinning,
                             etc., as practiced by commercial forest products industries

                        •    establishment and management of commercial plantations

                        •    other afforestation, and reforestation programmes

                        •    informal fuelwood gathering
                        Based on comments from the land use and forestry experts, the managed forests category
                        has been broadened to include sub-categories of trees which may not traditionally  have
                        been considered "forests". It can include village and farm trees if these are important for
                        biomass and biofuel accounting in some developing countries. It could also  include  urban
                        trees, trees planted along highways, aircraft runways, etc., if these are considered
                         significant for a particular country's biomass calculations. These dispersed trees do not
                         contribute greatly to carbon fluxes to or from biomass on a global scale. However, in
                         some countries, they may be important in accounting for the total amount of wood used
                         for fuel. Also, they may be of interest to some countries because of their potential use in
                         response strategies. For these reasons, they have been included in the basic calculation
                         methods so that national experts who feel they are important, and have necessary locally
                         available data, can include them.
                         As illustrated in the above list, the managed forests category also includes some tree
                         planting activities which, strictly speaking, are land use changes. Plantation establishment
                         and other afforestation/reforestation programmes are examples.  It is recognized that this
                         is conceptually inconsistent as the category is intended to account for ongoing interactions
                         with existing forest. However, from a pragmatic perspective, including these activities
                         within the category can simplify the calculations. These sub-categories are land-use
                         changes which create new managed forests. As soon as the land use change occurs (i.e.,
                         the tree planting), new land use becomes  part of the managed forests category which is
                         accounted for on an annual incremental basis. Although it would  be possible, it is not
                         necessary to estimate the lagged effects of this  change as is done with other land use
                         changes.   While including such a range of tree-related activities in one category may
                         introduce some confusion, the calculation procedure is basically the same for all sub-
                         categories, and this allows the simplest possible set of emissions  calculations.

                         As discussed in the Overview, the methodology is designed to accommodate users  at
                         several levels of detail. This is especially important in the managed forests category.
                          Possible levels include:
                          I    A simple first order approach, covering the main sub-categories, with calculations
                               based on simple default assumptions and default data provided.
                          2    Calculations at the same level of detail  but substituting more appropriate data and
                               assumptions from local sources.
                          3    Calculations following the same structure, but broken down to finer levels of detail
                               to improve accuracy and utility of estimates, where locally available data can support
                               this.
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                                                                 LAND  USE  CHANGE  &  FORESTRY
             4   Estimates derived from much more detailed and precise inventory-based forest
                  accounting methods. These results can be reformatted and presented in the form of
                  calculations comparable to those used by the other national experts operating with
                  less detailed data.

             It is highly desirable that the methodology be relevant for countries which have access to
             much more detailed data on managed forests. Some countries with highly developed
             forestry industries, do in fact keep track of existing commercial forests through periodic
             detailed surveys. For such countries, it is possible to derive from survey results aggregate
             values comparable to the data and assumptions used  in the simple approach, and present
             them in this common format. This will assist all interested  parties in evaluating various
             national estimates on a comparable basis,  and will thus be necessary to comply with
             requirements of Volume  I:  Reporting Instructions. Box 3 provides some further
             discussion of these procedures.
                                                   Box 3
                        ADAPTING DETAILED FOREST INVENTORY DATA To THE IPCC FORMAT
                    A number of countries with highly developed commercial forestry industries
                    routinely collect forest biomass data at a detailed inventory level which
                    allows for relatively precise and direct assessment of the changes in biomass
                    stocks, and equivalent carbon fluxes. National experts working with data of
                    this kind, should be able to derive from it values equivalent to those used in
                    calculating emissions with the IPCC methodology.
                    Regardless of how detailed the data base used, the results will be ultimately
                    presented in units (e.g. Gg) of carbon and CO2 emitted or removed in a
                    given  average responses (e.g., annual biomass growth rates by ecosystem
                    type) which year. Similarly, the number of hectares of forest in various types
                    can be aggregated up to categories matching the simple approach outlined
                    here. The amount of biomass removed as commercial harvest or for other
                    reasons, should also be relatively well established in such inventories. With
                    these data, it should be
                    possible to, in effect, work backwards to the derive the  necessary input
                    assumptions and aggregate values. For example, national experts might start
                    with a change in total biomass for specified  forest types  (and/or regions)
                    over a specified time period. Then they could add the amounts of biomass
                    removed through commercial harvest or for other reasons (e.g., thinning),
                    to get the total growth of biomass over the period. This could then be
                    divided by the number of kilo-hectares in the category (and the number of
                    years, if a multi-year period)  to get average  annual growth rates by category.
                    This would then provide all the values needed to reconstruct the
                    calculations in a comparable form to those from countries with  minimal data.
                    The national emission/removal estimates presented in this form would then
                    be easily  understood and compared by all other parties involved in the
                    international climate change discussions. The intent is to provide a
                    calculation and reporting framework which  can accommodate users with
                    vastly different levels of data available, yet allow them to place the results on
                    a comparable basis.
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LAND USE  CHANGE  &  FORESTRY

                        Managed forests (which are harvested for forest products including fuel wood) may be
                        either a source or a sink for carbon dioxide. The simplest way to determine which is by
                        comparing the annual regrowth versus annual harvest, including the decay of forest
                        products and slash left during harvest. Decay of biomass damaged or killed during logging
                        results in short-term release of CO2. For the purposes of the basic calculations, the
                        recommended default assumption is that all carbon removed in wood and other biomass
                        from forests is oxidized in the year of removal. This is clearly not strictly accurate in the
                        case of some forest products, but is considered a legitimate, conservative assumption  for
                        initial calculations. Box 4 provides some further discussion of this issue.
                                                              Box 4
                                                  THE FATE OF HARVESTED WOOD

                              Harvested wood releases its carbon at rates dependent upon its end-use:
                              waste wood is usually burned immediately or within a couple of years, paper
                              usually decays in up to 5 years (although landfilling of paper can result in
                              longer-term storage of the carbon and eventual release as methane or CO),
                              and lumber decays in up to 100 or more years. Because of this latter fact,
                              forest harvest (with other forms of forest management) could result in a net
                              uptake of carbon if the wood that is harvested is used for long-term
                              products such as building lumber, and the regrowth is relatively rapid. This
                              may in fact become a response strategy.
                              For the initial calculations of CO2 emissions from managed forests, however,
                              the recommended default assumption is that all carbon in biomass harvested
                              is oxidized in the removal year. This is based on the perception that stocks
                              of forest products in most countries are not increasing significantly on an
                              annual basis. It is the net change in stocks of forest products which should
                              be the best indicator of a net removal of carbon from the atmosphere,
                              rather than the gross amount of forest products produced in a given year.
                              New products with long lifetimes from current harvests frequently replace
                              existing product stocks, which are in turn discarded and oxidized. The
                              proposed method recommends that storage of carbon in forest products be
                              included in a national inventory only in the case where a country can
                              document that existing stocks of long term forest products are in fact
                              increasing.
                               If data permits, one could add a pool to Equation 5.4 (I) in the managed
                              forests calculation to account for increases in the pool of forest products.
                              This information would, of course, require careful documentation, including
                               accounting for imports and exports of forest products during the inventory
                               period.
                         The net regrowth of the forest (and re-accumulation of carbon) depends on the type of
                         forest logged and the intensity of logging or other harvesting. Well managed commercial
                         forests, replacing natural forests, would over the long term be expected to be close to
                         zero net emissions. In many cases, where historically cleared areas are regrowing under
                         commercial management, with limited logging, the forest areas are currently a net sink. If
                         forests (or parts of forests) are logged or harvested at a rate which exceeds regrowth,
                         then there is a net loss of carbon.
                         Establishment of plantations and other tree planting activities result in absorption of CO2
                         from the atmosphere and storage of this carbon until the vegetation is burned or decays.
                         Restocking of managed forests, planting of urban, village and farm trees, and establishing
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                                                                   LAND  USE CHANGE  &  FORESTRY
               plantations on unforested lands, therefore, result in an uptake of carbon from the
               atmosphere, at least until the biomass is harvested and enters a decay pool, or the system
               reaches maturity. The effect of plantation establishment can be to create a net sink for
               carbon even if the plantation is harvested for products that are rapidly oxidized (e.g.,
               fuelwood). If the plantations are harvested so that there is no net loss of biomass over
               time (i.e., harvested in a sustainable fashion), then the rate of carbon accumulation on land
               is positive (or at least non-negative) and tied directly to changes in the area of plantations
               and their average biomass.

               The conversion of natural forests to plantations may result in an initial loss of biomass
               carbon due to an initial reduction in standing biomass. If plantations are established by first
               clearing existing forests, the initial loss should appear under forest clearing above.
               Reaccumulation of biomass in these plantations in subsequent years would be accounted
               for here under managed forests. The approach accounts for all plantations in operation in
               a given year, including both previously planted and newly established plantations.

               The method for calculating the affected forest harvest, afforestation, and reforestation on
               carbon stocks is shown in Equation 5.4.
                                                 EQUATION 5.4

                                                       I
                             Hectares of land in a particular category (e.g., plantations)
                                  x Average annual growth per hectare in biomass


                                         Gross annual growth increment.
                              Total biomass increment is the sum of all relevant categories.
                                                       2
                                           Total Harvest by category
                                         x Expansion factor to treat slash


                                           Gross annual biomass loss.
                     Total harvest and other biomass loss is the sum of all relevant categories of harvest
                                                       3
                                      Total gross annual growth increment -
                                         Total gross annual biomass loss


                                 Net annual biomass change (positive or negative).
              The recommended unit of calculation is dry biomass, and it is necessary to convert to
              carbon for emissions estimation. A general default value of 0.45 tonnes-C/tonne dry
              biomass is recommended for all biomass calculations. If more accurate conversion values
              are available for the particular system, these should of course be used.

              Growth Increments

              Estimates of average annual accumulation of dry matter as biomass per hectare are
              presented for in forests naturally regrowing by broad category in Table 5. These values
              can be used as default values for growth rates in similar managed forest categories if no
              other information is available. Fore forests which are more intensely managed (e.g., with
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LAND USE  CHANGE  &  FORESTRY
                       periodic thinning, restocking, etc.) annual growth increments could be somewhat different
                       In countries where such practices result in significantly different average growth rates,
                       locally available data should be used instead of Table 5 values. Values for some typical
                       plantation species are presented in Table 6, can be used as default values.

                       Biomass Loss
                       Two approaches can be used to estimate biomass harvest and other losses from managed
                       forests.
                       Commercial Harvest Statistics  The first, and obvious, approach is to use statistics on
                       amounts of biomass actually removed from forests. In countries where commercial
                       harvests of various kinds make up a large majority of total biomass losses, and statistics are
                       well maintained, this may be the only approach needed. Country specific  estimates of
                        commercial harvest statistics are provided in annual FAO Forests Products Yearbooks
                        (I993b). and periodic Assessments (e.g., FAO, I993a), and are also generally available from
                        national governments.
                        In using commercial harvest statistics, users must pay careful attention to the units
                        involved. Commercial harvest statistics are often provided for the commercial portion of
                        biomass only, in cubic meters (m3) of roundwood. If this is the case, values will need to be
                        converted to tons of dry biomass. and total biomass removed including slash. Some
                        general default values for converting volume data to tons are 0.65 t dm/m3 for deciduous
                        and 0.45 t dm/m3 for conifers. To account for the biomass lost beyond the commercial
                        wood portion expansion factors can be applied. Some general default values from the
                        literature are 1.75 for undisturbed forests and 1.90 for logged forests.   There is
                        considerable variability in these conversion values and expansion factors, so use of more
                        specific locally available data is highly desirable. Also, some commercial harvest data may
                        be  reported as equivalent total biomass (i.e., expansion factors already applied). It is
                        important to check carefully the information in the original harvest data to ensure that
                        expansion factors are used  only where appropriate.
                        Fuelwood Consumption Accounting In many countries, however, commercial statistics will
                        give only a partial account of wood removals and may need to be supplemented with an
                        alternative approach. Significant amounts of biomass may removed from forests on an
                        informal basis (i.e., they are never accounted for in commercial statistics). This is generally
                        true where "traditional" biomass fuels make up a major share of total fuel used in
                         residences and small commercial enterprises.
                        The alternative approach, Fuelwood Consumption Accounting, first estimates fuelwood
                         consumed based on per capita consumption data and population statistics. This accounting
                         should also consider charcoal consumption, and "back out" an estimate of the wood which
                         must have been consumed in traditional charcoal manufacture. The Fuelwood
                         Consumption Accounting approach is discussed in more detail in the Energy chapter, in
                         the section on emissions from traditional biomass fuels. Results from this type of
                         accounting can be used in managed forest calculations to account for removals of carbon.

                         Any wood which was extracted from cleared forests and used for fuel,  will already have
                         been accounted for in the forest clearing calculations above. This amount should be
                         subtracted from total wood consumed, directly for fuel and for traditional charcoal
                         making, to determine the amount which must have come from remaining managed forests.
                         The result of this calculation can then be combined with any commercial harvest amounts
                         to produce a total amount of biomass lost from managed forests.
                         There is an implicit assumption that slash is not accumulating. The instantaneous release of
                          CO2 from the current year's slash that is explicit in Equation 5.4 (2) is  a simple
                          mathematical device to treat slash oxidation from previous years under the assumption
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                                                               LAND  USE  CHANGE &  FORESTRY
             that the slash pool is not changing. The expansion factor for slash in Equation 5.4 (2) could
             be modified to address the destruction of below ground biomass left after harvest

             Finally, although plantation establishment usually results in an accumulation of soil carbon,
             conversion of natural forests to plantations could cause a net loss of carbon from the
             soil.   Because of the uncertainty about the magnitude and direction of the soil carbon
             change in plantation systems, this is ignored in the basic calculations. This issue is discussed
             in the Refinements section.
    5.3    Refinements  In  Calculations
             5.3.1  Issues  and  Possible  Methodologies

             There are a number of areas in which the basic calculations, could be improved at least
             theoretically. Simplifying assumptions have been made in many places in order to produce
             methods consistent with data likely to be available in many countries. The basic
             calculations focus only on the most important categories for emissions of CO2 within a
             much larger set of land use and forest management activities having some impact on GHG
             emission fluxes. Some activities are known to result in GHG fluxes, but cannot be
             quantified based on the available  scientific research results. Many of these issues are
             summarized below to assist users in considering which, if any, of these possible
             refinements could be included in national inventories, currently, or in the future as
             scientific understanding improves.
             The first section deals with the subcategories already discussed in the basic calculations,
             but highlights a number of ways in which these calculations could be augmented. The
             second section discusses additional categories of land use change or forest management
             which could be added to the categories in the basic calculations.
             5.3.2 Possible  Refinements or Additions to  Basic
             Categories

             Cleared Forests
             Forest clearing is a very complex and diverse set of activities which can have many
             interactions with biospheric fluxes of greenhouse gases over long periods of time. The
             components of this set of interactions which are included in the previous section are
             those on which there is general agreement among experts of their importance and simple
             estimation procedures. A number of other possible elements have been discussed in the
             scientific literature, but are controversial or difficult to calculate at present.
             •    Emissions from Burning of Cleared Forests
                  A number of aspects of emissions due to burning could be treated in more detail.
                  a   Subsequent burns in years after clearing. In some cises, where forests are cleared
                      for agricultural purposes, the land may be partially burned in the year of
                      clearing, but may also be burned again in later years. Fearnside (I990b) indicates
                      that pastures in the Brazilian Amazon are typically burned two or three times
                      over about a ten year period. This would cause a larger fraction of carbon in
                      cleared biomass to be released to the atmosphere sooner than the approach
                      now included in the basic calculations, and would certainly increase emissions of
                      non-CO2 trace gases from biomass burning.
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LAND  USE  CHANGE & FORESTRY

                            b   Non-CO2 trace gases re/eased after burning. Basic calculations address the main
                                issues in trace gas production by burning, however, they do not treat all issues.
                                For instance, the effect of past burning, particularly of forests, on trace gas
                                exchanges must eventually be considered. Specifically, the  instantaneous release
                                of non-CO2 trace gases when forests are burned is included in Land Clearing
                                calculations. However, the longer-term release or uptake  of these gases
                                following forest burning is an important research issue and should eventually be
                                included in refinements of calculations. The issue of the contemporary release
                                of non-CO2 trace gases associated with past burning is complex. For example,
                                clearing by burning may stimulate soil nutrient loss. Measurements in temperate
                                ecosystems44 indicate that surface biomass burning enhances emissions of N2O
                                and NOX from the soils for up to 6 months following the burn; however, in
                                other studies measurements of N2O emissions at a cleared and burned tropical
                                forest site in Brazil, begun five months after the burn and continuing for a year,
                                were not significantly different, however, from those taken from a nearby intact
                                forest site.   The "historic" issue is obviously complex and further research is
                                needed before an adequate methodology for emissions calculations can be
                                proposed.
                       •    Delayed release of non-CO2 trace gases after land disturbance.

                            Even when no burning is involved there may still be a release of trace gases. An
                            experiment in a temperate forest in the northeast United States found that
                            clearcutting resulted in enhanced N2O flux to the atmosphere via dissolution of N2O
                            in the soil water, transport to surface waters, and degassing from solution.   An
                            experiment in Brazil found that N2O emissions from newly clearcut tropical forests
                            were about three times greater than those from adjacent undisturbed forests.
                            Conversion of tropical forests to pasture also has been found to result in elevated
                            N2O emissions relative to the intact forest soils.48 Another example  involves the
                            loss of a sink for methane which, in effect, adds to the atmospheric burden of CH4.
                            Specifically, the loss of forest area (tropical or temperate) may  also result in
                            increased net CH4 emissions to the atmosphere. Soils are a natural sink of CH4 (i.e.,
                            soils absorb  atmospheric CH4), and various experiments indicate that conversion of
                            forests to agricultural lands diminishes this absorptive capacity of soils.

                       •    Methane from termites attributable to biomass left to decay
                            When forests are cleared, a portion of the cleared biomass may be left to decay on
                            the ground.  Frequently some of the biomass  decay is accomplished by termites which
                            emit both methane and carbon dioxide during this process. Fearnside (I990b)
                            estimates that 75% of the unburned carbon is decomposed by termites, and of this
                            75%, 99.8% is released as  CO2 and 0.2% is released as CH4.  Fearnside suggests that
                            forest clearing results in increased termite populations and thereby enhances natural
                            termite CH4 emissions. However, as discussed by Collins and Wood  (1984), data
                            from Malaysia, Nigeria, and Japan indicate that clearing and cultivation in some forests
                            reduces termite populations. The only incidence of termite abundance increase
                            following clearing cited by Collins and Wood was entirely due  to a fungus-growing
                            termite, a type of termite which is unlikely to produce methane. Because of the
                            uncertainty of the effect of clearing on termite populations and associated CH4
                            release, no guidance on calculation of this component is included in the methodology.
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                                                               LAND  USE CHANGE  &  FORESTRY
            •   Soil carbon loss in tropical systems
                The basic calculations allow but do not encourage estimation of soil carbon loss after
                clearing of tropical forests. There are research results which indicate that conversion
                of tropical forests to pasture may or may not result in loss of soil carbon.   Because
                of the uncertainty no recommendation is made in the basic method concerning
                whether .and how to estimate this component. Further research appears needed to
                resolve this issue.

            •   Fate of roots in cleared forests
                The basic calculation ignores the fate of living belowground woody biomass (roots,
                etc.) after forest clearing. The amount of belowground biomass affected, and its fate,
                need to be considered as work continues beyond the basic calculations. This
                belowground biomass could be treated as slash but with perhaps a longer decay time.
                The issue merits research.
            •   Aboveground biomass after conversion

                 In the basic calculation, a single default value (10 tonnes dm/ha) is recommended for
                 aboveground biomass which regrows after forests are cleared for conversion to
                 crops or pastures. This may be somewhat variable depending on the type of crop or
                 other vegetation which regrows. National experts carrying out more detailed
                 assessments may wish to account more precisely for this variability.

             Conversion of Grasslands to Cultivated Lands:
             Non-CO2 Trace Gases
             Conversion of natural grasslands to managed grasslands and to cultivated lands may affect
             not only the net emission of CO2 but CH4, N2O, and CO emissions as well. For instance,
             the conversion of natural grasslands to cultivated lands has been found in the semi-arid
             temperate zone to also decrease CH4 uptake by the soils.  It is not clear what the effect
             on N2O would be, unless of course nitrogen fertilization occurs. The effect of conversion
             of natural grasslands to managed grasslands on trace gas emissions has not been evaluated
             in the field, except for the effect of associated nitrogen fertilization on N2O emissions.
             Nitrogen fertilization on managed fields may increase carbon accumulation on land, relative
             to the unfertilized system,  and grazing by domestic animals may also affect trace gas fluxes.
             CO fluxes may be affected due to changes in soil temperature and moisture. These effects
             on trace gas fluxes, however, are highly speculative and remain a research issue.

             Abandoned Lands
             The basic calculations account only for the portion of abandoned lands which regrow
             toward a natural state. There may be additional  releases of carbon from abandoned lands
             which continue to degrade. Where data are available, analysts doing detailed assessments
             may wish to account for this phenomenon.

             Managed Forests

             Prescribed Burning of Forests: Non-C02 Trace Gases
             The issue of prescribed forest burning is complex because of two issues. First, there is the
             question of the rate of change that humans have induced and  second, there is the question
             of releases of trace gas several years after the burning. Prescribed burning is a method of
             forest management by which forests are intentionally set; on fire in  order to reduce the
             accumulation of combustible plant debris and thereby prevent forest fires, which could
             possibly be even more destructive. This activity is primarily limited  to North America and
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LAND  USE CHANGE &  FORESTRY

                       Australia.   Because carbon is allowed to re-accumulate on the land after burning no net
                       COj emissions occur over time,'
                       from the biomass combustion.
                                                   S3
although emissions of CH4, CO, N2O, and NOX result
                       Some of the issues associated with prescribed forest burning, particularly in the temperate
                       world, remain important research topics. Some have suggested that prescribed forest
                       burning may be increasing carbon stocks in forests and hence serving as a CO2 sink, but at
                       the same time adding other radiatively important non-CO2 trace gases  to the
                       atmosphere. An important issue is the change in burning rate because of human activity. Is
                       prescribed burning, and its consequent emissions, just a man-made replacement for what
                       would have occurred naturally?  What is the rate change?  If we assume that this question,
                       the rate of change, can be answered, then the issue of trace gas release for prescribed
                       burning is similar to trace gas emissions following forest clearing deforestation.

                       The second complicating issue which should be considered is the release of non-CO2
                       trace gases in years after burning. This is also discussed under "Cleared Forests" above.
                       The same uncertainties apply here, although this may be a less important area for
                       prescribed burning, because the forests will be regrowing quickly, and possibly overcoming
                       the conditions which could  cause longer term trace gas emissions.

                       Soil carbon and establishment of plantations
                       In the basic calculations, no soil carbon accumulation is assumed plantations are
                       establishing (or other tree planting activities occur) on previously non-forest lands. If
                       plantations are established where natural or managed forests previously existed, then the
                       carbon content of soils may not change significantly. However, it is possible that the
                       establishment of plantations on previously non-forest lands could  result in accumulation of
                       soil carbon over time. Further investigation may be useful to determine whether this is a
                       significant enough effect to warrant addition to the calculations.
                       5.3.3  Other Possible  Categories  of Activity

                       Several other land use activities affect the flux of carbon dioxide and other trace gases
                       between the terrestrial biosphere and the atmosphere. Shifting cultivation may now be
                       reducing the storage of carbon in forests, because of shorter fallow periods, and thereby
                       becoming a net source of CO2 to the atmosphere. The changing areas and distribution of
                       wetlands may be adding to or reducing the methane burden of the atmosphere. These
                       issues are complex; often the sign of the flux is not even known, and simple models may
                       not give reasonable results. In this section, some of the issues and possible methodological
                       approaches are recorded; however, an agreed-upon methodology is not yet at hand.

                       Shifting Cultivation

                       Shifting cultivation, or slash-and-burn agriculture, is a common agricultural practice in the
                       tropics in which short periods of cultivation (usually about 3 to 5 years) alternate with
                       longer periods of fallow (about 10 to  50 years). Clearing occurs by initial cutting and
                       felling, followed by a series of burns. When practiced in the traditional manner, shifting
                       cultivation produces essentially no net CO2 emissions because the forest is allowed to
                       return to its original biomass density during the fallow period.5 However, increasing
                       population pressure has reduced the lengths of fallow periods so that currently much of
                       the fallow land is not allowed to recover and net CO2 emissions are believed to result.55
                       Loss of soil carbon also may occur during shifting cultivation, although the loss is certainly
                       far less than for permanent cultivation.
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                                                                LAND USE  CHANGE  & FORESTRY
             Calculation of net emissions due to shifting cultivation requires calculation of average
             annual emissions due to clearing of forests for cultivation and calculation of average annual
             uptake due to abandonment of cultivated lands in the fallow period of the shifting
             cultivation cycle. This involves a rather complex pattern of land cohorts and probably
             requires a model to do the book keeping.
             The basic concepts are not difficult. The carbon calculations would proceed almost exactly
             like the deforestation and abandonment terms in the basic: methodology; however, the
             difficulty is that the abandonment period may be shorter, and this may only be apparent by
             using a cohort-based model and a finite stock of forest. In other words the increasing rate
             of shifting cultivation (the likely data) will force a shorter fallow period and hence less
             regrowth, and this dynamic may only become apparent when one models the shifting
             cultivation cycle within a specific area of available forest
             One intermediate simple approach is to split the calculation into the two logical
             components. The deforestation component which would be treated similarly to the basic
             calculations; namely, convert the above ground dry biomass  to carbon (multiply by 0.45)
             and assume 90% of this material is released as CO2 less the amount taken upon by the
             replacing crops (default value of 5 tonnes of carbon per hectare). In this intermediate step
             one ignores soil carbon and history since the abandonment period follows so quickly upon
             deforestation. To calculate the uptake  of carbon by the regrowing forest during the fallow
             cycle, simply estimate the amount of land in abandonment, (but not yet in steady-state) and
             the average rate of carbon  accumulation per unit area in these fallow lands. The difference
             would be the net flux of CO2 associated with shifting cultivation.

             Flooding and Wetland Drainage

             Land Flooding
             Flooding of lands due to construction of hydroelectric dams, or other activities, results in
             emissions of CH4 due to anaerobic decomposition of the vegetation and soil carbon that
             was present when the land was flooded, as well as of organic material that grows in the
             floodwater, dies, and accumulates on the bottom. The methane emissions from this source
             are highly variable and are dependent on the ecosystem "icype", and the status of the
             ecosystem, that is flooded (i.e., above- and below-ground carbon, plant types, whether any
             pre-flooding clearing occurred, etc.) and on the depth and length of flooding (some regions
             may only be flooded for part of a year). Rates of methane emissions from freshwater
             wetlands are also strongly dependent on temperature, and therefore vary seasonally, as
             well as daily. Net emissions of N2O and CO also may be affected by this activity, although
             these fluxes are not well determined.
             A straight-forward methane flux calculation can be based on the area of land flooded, due
             to hydroelectric production or other manmade causes, an average daily CH4 emission
             coefficient, and the number of days in  the year that the area is flooded. Since
             measurements of CH4 emissions from freshwater wetlands are so variable, both spatially
             and temporally, the area should be divided into groups based on characteristics such as
             length of flooding, vegetation type, and latitude. Then appropriate emission coefficients can
             be chosen for each group, rather than choosing one emission coefficient for the entire
             area of flooding. Table 8 presents average daily CH4 emission rates for natural wetlands,
             derived from measured emission rates in field experiments, and average CH4 production
             periods based on data on monthly mean temperatures and  inundation lengths. These  rates
             and production periods can be used if countries do not have more appropriate estimates.
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                       Wetland Drainage
                       Freshwater wetlands are a natural source of CH4, estimated to release 100-200 Tg CH4
                       (75-150 Tg CH4-C) per year due to anaerobic decomposition of organic material in the
                       wetland soils (Note: Tg = teragrams, I Tg = IO12 grams =  I06 tonnes).57 Destruction of
                       freshwater wetlands, through drainage or filling, would result in a reduction of CH4
                       emissions, and an increase in CO2 emissions due to increased oxidation of soil organic
                       material.58 The magnitude of these effects is largely a function of soil temperature and the
                       extent of drainage (i.e., the water content of the soil). Also, since dryland soils are a sink
                       of CH4, drainage and drying of a wetland could eventually result in the wetland area
                       changing from a source to a sink of CH4.
                       Loss of wetland area could also affect net N2O and CO fluxes, although both the direction
                       and magnitude of the effect is highly uncertain.  Natural dryland soils are a source of N2O,
                       believed to emit 9-28 Tg N2O (3-9 Tg N2O-N) annually as a result of nitrification and
                       denitrification processes.60 This  emission estimate is highly uncertain, however, as
                       emission measurements vary both temporally and spatially by up to an order of magnitude.
                       Moreover, the measurements are not consistently correlated with what are believed to be
                       controlling variables such as soil temperature, moisture, and composition, and vegetation
                       type. Dryland soils both produce and consume CO. Carbon monoxide production,
                       estimated at 2-32 Tg CO (1-14 Tg CO-C) per year, is an abiotic process due to chemical
                       oxidation of humus material.61 It is strongly dependent on soil temperature, moisture, and
                       pH. Destruction of CO is a biological process believed to be due to microorganisms
                       present in the soil. Carbon monoxide destruction (250-530 Tg CO/yr, or 107-227 Tg CO-
                       C/yr) increases with increasing temperature, although it is independent of soil surface
                       temperature (indicating that the process is more active in  deeper soil layers) and requires
                       a minimum soil moisture.62 Desert soils have always been found to be a net source of CO,
                       as have savanna soils, at least during the hottest parts of the day. CO destruction
                       outweighs production in humid temperate soils; humid tropical  soils are believed to also
                       be a net sink of CO because of their higher soil moisture and lower soil temperature than
                       deserts and savannas.
                       To calculate the reduction of CH4 emissions due to wetland drainage, the area drained  is
                       multiplied by the difference in the average daily CH4 emission rate before and after
                       draining, and is multiplied by the number of days in a year that the wetland was emitting
                       CH4 prior to drainage. The number of days of CH4 emissions prior to drainage can be
                       approximated by using the number of days in the year that the wetland was flooded. To
                       calculate the increase in CO2 emissions due to this activity, the area drained  is multiplied
                       by the difference in the average annual CO2 emission rate before and after draining. This
                       assumes that the elevation in CO2 emissions due to drainage continue throughout the
                       year. However, the length of time over which the elevated CO2 emissions continue is
                       uncertain  — it could be less than a yean it could be greater than a year. The net release
                       would also depend on the degree to which there was regrowing vegetation, a CO2 sink.

                       In summary, the difference in CH4 and CO2 emissions before and after drainage will vary
                       depending on factors such as soil temperature, extent of drainage, and wetland type. Very
                       little data are available on this subject. A laboratory experiment with materials
                       representing a fen, a bog, and a  swamp found that the reduction in CH4 emissions
                       increased with increasing drainage, although the magnitude of the  reduction varied
                       between the three types of materials. CH4 emissions from the fen decreased from about
                       21 mg CH4-C/m2/day (with the water level about 10 cm above the surface) to about 0.8
                       CH4-C/m2/day (with the water table about 70 cm below the surface); CH4 emissions from
                       the swamp decreased from about 9 to about 0.6 CH4-C/m2/day; and CH4 emissions from
                       the bog decreased only slightly, from about 0.7 to about 0.6 mg CH4-C/m /day. CO2
                       emissions from all three materials were about  0.08 mg CO2-C/m  /day (with the water
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                                                             LAND USE CHANGE & FORESTRY
             level about 10 cm above the surface), and increased to about 2 mg CO2-C/m /day (with
             the water table about 70 cm below the surface.

             The direction and magnitude of the effects on these gases are highly uncertain and
             significant advances in our understanding of the biological processes as well as
             determination of the areal extent of the activities will be required before these
             calculations can be adequately accomplished. It may be possible to include methane
             calculations associated with land flooding in early refinements of the calculations, but the
             N2O and CO calculations are more difficult and as yet of uncertain importance.
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                5.4     Tables
                                                                    TABLE 5-1
                                          DRY MATTER IN ABOVEGROUND BIOMASS IN TROPICAL FORESTS
                                                                 (tons dm/hectare)
                                                          Closed Forests
                                                                                                                Open Forests
                                        Broadleaf
                                                                                Conifer
                          Undisturbed    Logged    Unproductive     Undisturbed    Logged    Unproductive    Productive    Unproductive
                America
                              230
                                          190
                                                       ISO
                                                                      ISO
                                                                                  60
                                                                                               60
                                                                                                             60
Africa
Asia
300
300
240
ISO
185
230
130
160
60
135
no
130
36
61
16
20
               Volume-based estimates derived from a variety of sources. Recent revised estimates for aboveground biomass in undisturbed closed
               broadleaf forests were taken from Brown and Lugo (1992) for Tropical America, Brown et al. (in press) for Asia and Brown (1993) for
               Africa.  Corresponding values for logged and unproductive forests were derived on the basis of the ratios of these biomass densities to the
                rfomass density for undisturbed forests as reported in Brown et al. (1989).  For closed conifer forests, stemwood biomass/hectare was taken
                rom Brown and Lugo (1984) and multiplied by more recent expansion factors for undisturbed, logged and unproductive categories (1.75,
                1.90. and 2.0 respectively) from Brown et al. (1989). Values for open forests were taken from Brown and Lugo (1984) and multiplied by
                ).77 to obtain the aboveground portion only.
                iNOlC.
                Estimates based on destructive sampling involve direct measurements (weighing) of biomass harvested from an experimental site. Volume-
                iased estimates are generally somewhat lower than those based on destructive sampling, and are derived from FAO data on commercial
               wood volumes that are converted to mass units based on average wood densities and ratios of aboveground biomass to commercial biomass
                [i.e., expansion factors). There is considerable uncertainty in all regional estimates of biomass densities of tropical forests.  Researchers
               agree that there Is a great deal of variability from stand to stand and among subreglons within large regions. For example, Brown and Lugo
               (1992) report biomass estimates ranging from 166 to 3321 dm/ha for dense Amazonian forests.

               There are also some differences in the way different experts interpret the available data to produce averages.  Fearnside (1993) has
                produced somewhat higher average estimates of aboveground biomass for the Brazilian Amazon than those of Brown and Lugo (1992)  His
                estimates are for:
                                                             Average for Brazilian
                                                                  Amazon

                                                                  (t dm/ha)
Forests Actually Cleared in
 1990 in Brazilian Amazon

       (t dm/ha)
                              Undisturbed forests
                                                                    308
                                                                                             291
                              Logged forests
                                                                                             271
                Fearnside (1992) and Brown and Lugo (1992) discuss in detail a number possible explanations for the differences in results.
TABLE 5-2
DRY MATTER IN ABOVEGROUND BIOMASS IN TEMPERATE AND BOREAL FORESTS
(tons dm/hectare)

Primary
Secondary
Temperate Forests
Evergreen
295
220
Deciduous
250
175
Boreal Forests

165
120
  5.32

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                                                                  LAND USE CHANGE  &  FORESTRY
              Source
              Primary forest estimates from Whittaker and Likens (1973); secondary forest estimates from Houghton et al.
              (1983). Total biomass estimates were converted to aboyeground biomass by multiplying by 0.83 (Leith and
              Whittaker, 1975). Alternate estimates of aboveground biomass per hectare, by country, for coniferous
              species and non-coniferous species, can be derived using statistics provided in ECE/FAO (1985). Data are
              provided for 22 countries.
TABLE 5-3
CARBON IN SOILS IN TROPICAL FORESTS
(tons carbon/hectare)

America
Africa
Asia
Moist
115
115
115
Seasonal
100
100
100
Source:
Post, W.M., et al., 1982.
Note:
The forest categories presented here are different from those presented in Tables
the values for moist and seasonal forests presented above can be used for both clo
(broadleaved and coniferous); the values for dry forests presented above can be us
Dry
60
60
60
and 2. The average of
set) forest types
ed for open forests.
TABLE 5-4
CARBON IN SOILS IN TEMPERATE AND BOREAL FORESTS
(tons carbon/hectare)

Primary
Secondary
Temperate Forests
.Evergreen
134
120
Deciduous
134
120
Boreal Forests

206
185
Source: Schlesinger, 1977, as cited in Houghton etal., 1983; and Houghton et al., 1987.
Note: Alternate values for soil carbon in tropical, temperate, and borjial forests, by continent, are available
in Zinke et al. (1984). However, care must be taken when choosing appropriate soil carbon values in Zinke
et al. (1984). Ecosystem types in this reference may not match the ecosystem types for which clearing data
and biomass estimates are available.
PART 2
5.33

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LAND USE CHANGE & FORESTRY
TABLE 5-5
ANNUAL AVERAGE ABOVEGROUND BIOMASS UPTAKE BY NATURAL REGENERATION
c dm/ha
Region

Tropical

Temperate

Boreal
America
Africa
Asia

Evergreen
Deciduous

Forest Types
Closed Forests
0-20 Years
8.0
II
II
0-20 Years
7.5
S.S
4.0
20- 100 Years
0.9
1.0
1.0

1.8
1.4
I.I
Open Forests

4.0
4.0
4.0
{?<&:;*'&?$"?' l'WC^-'.;--',

£•$&&• '"«!;¥&
'•;<•, W.'-ft*??*.1 'fe-ifjV'"
20- 100 Years
0.25
0.25
0.25




Note Growth rates are derived by assuming that tropical forests regrow to 70% of undisturbed forest biomass ana temperate ana
boreal forests regrow to S0% of undisturbed forest biomass in the first twenty years. All forests are assumed to regrow to 100% of
undisturbed forest biomass in 100 years. Undisturbed forest biomass values are from Tables 1 and 2. For tropical forests, assumptions
on the rates of growth in different time periods are derived from Brown and Lugo, 1990. Assumptions for temperate and boreal
forests are based on Houghton et al.. 1983. and Houghton et al., 1987.
 5.34

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                                                                        LAND  USE CHANGE  &  FORESTRY
                                                      TABLE 5-6
                                 AVERAGE ANNUAL ACCUMULATION OF DRY MATTER AS
                                               BIOMASS IN PLANTATIONS
                                        Forest Type
 Annual Increment in Biomass
    (tons dm/hectare/year)
                             Tropical
                                 Acacia spp.
                                 Eucalyptus spp.
                                 Tectono grandis
                                 Pinus spp.
                                 Pinus caribaea
                                 Mixed Hardwoods
                                 Mixed Fast-Growing Hardwoods
                                 Mixed Softwoods
           15.0
           14.5
           8.0
           11.5
           10.0
           6.8
           12.5
           14.5
                             Temperate
                                 Douglas fir
                                 Loblolly pine
           6.0
           4.0
                              Sources: Derived from Brown et al., 1986.
                              Farnum etal., 1983
                              Note:
                              These are average accumulation rates over expected plantation lifetimes:
                              actual rates will vary depending on the age of the plantation. The data for
                              the temperate species are based on measurements in the U.S. Data on
                              other species, and from other regions, should be supplied by individual
                              countries (as available).  Additional temperate estimates by species and by
                              country can  be derived from data in ECE/FAO (1985), assuming that
                              country averages of net annual increment for managed and unmanaged
                              stands are reasonable approximations for plantations.
                                                      TABLE S-7
                                   EMISSION RATIOS FOR OPEN BURNING OF CLEARED
                                                       FORESTS
                                        Compound
       Ratios
                                          CH4
                                           CO
                                          N20
                                          NOX
0.012 (0X109-0.015) '
0.06   (0.04-0.08) 2
0.007  (0.005 - 0.009) •
0.121  (0.094-0.148)'
                               Sources:    '  Delmas, 1993
                                          2Lacaux, 1993
                                          3 Crutzen and Andreae, 1990
                               Note:
                               Ratios for carbon compounds, i.e., CH4 and CO, are mass of carbon
                               compound released (in units of C) relative to mass of total carbon
                               released from burning. Those for the nitrogen compounds are
                               expressed as the ratios of emission (in units of N) relative to total
                               nitrogen released from the fuel.
PART  2
                                                                                                                           5.35

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LAND  USE CHANGE &  FORESTRY
TABLE 5-8
AVERAGE METHANE EMISSIONS AND PODUCTION PERIODS OF NATURAL WETLANDS
Wetland Categories
Bogs
Fens
Swamps
Marshes
Floodplains
Lakes
Emission Rate
(mg CH^C/rnVday)
II
(1-38)
60
(21-162)
63
(43-84)
189
(103-299)
75
(37-150)
32
(13-67)
Production Period
(days)
178
169
274
249
122
365
Source: Aselmann and Crutzen, 1989.
Noter Average daily emission rates are derived from measured emission rates in field experiments
(the range in measured emission rates is in parentheses after the average), and average production
periods are based on monthly mean temperature data and lengths of inundation.
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              atmospheric concentration of CO and CH, in the northern part of the Guayana Shield,
              Venezuela. Journal of Geophysical Research 95:22,475-22,480.

              Schlesinger, W.H. 1977. Carbon balance in terrestrial detritus. Annual Review of Ecology and
              Systemotics8:5l-8l.

              Schlesinger, W.H. 1982. The Role of Terrestrial Vegetation  in the Global Carbon Cycle: Methods
              for Appraising Changes. Wiley,  New York.

              Schlesinger, W.H. 1984. The world carbon pool in soil organic matter: A source of
              atmospheric CO2. In: Woodwell, G.M. (ed.). The Role of Vegetation in the Global Carbon
              Cycle: Measurement by Remote Sensing. Scope 23. John Wiley and Sons, New York. pp.  III-
              127.

              Seiler, W., and P.J. Crutzen. 1980. Estimates of gross and net fluxes of carbon between the
              biosphere and the atmosphere from biomass burning. Climatic Change 2:207-247.

              Seiler, W., and R. Conrad. 1987. Contribution of tropical ecosystems to the global budgets
              of trace gases, especially CH.,, H2, CO, and N2O. In: Dickinson, R.E. (ed.). The Geophysiology
              of Amazonia. John Wiley, New York. pp. 133-160.
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                       Singh, K.P., and R. Misra. 1978. Structure and Functioning of Natural, Modified and SiMcultural
                       Ecosystems of Eastern Uttar Pradesh. Technical Report MAB Research Project, Banaras
                       Hindu University, Varanasi.
                       Tans P.P., I.Y. Fung, and P.H. Daum. 1990. Observational Constraints on the Global
                       Atmosphere Carbon Dioxide Budget. Science 247:1431-1438.
                       U.S. HEW (U.S. Department of Health, Education, and Welfare).  1970. Air Quality Criteria
                       for Carbon Monoxide. U.S. HEW, Washington, D.C.
                       Whittaker, R.H., and G.E. Likens. 1973. Carbon in the biota. In: Woodwell, G.M., and E.V.
                       Pecan (eds.). Carbon and the Biosphere. U.S. Atomic Energy Commission, Symposium Series
                       30. National Technical Information Service, Springfield, VA, USA. pp. 281-302.
                       Whittaker, R.H., and G.E. Likens. 1975. The biosphere and Man. In: Lieth, H., and R.H.
                       Whittaker (eds.). Primary Productivity of the Biosphere. Springer-Verlag, New York. pp. 305-
                       328.
                       Whittaker, R.H. 1975. Communities and Ecosystems. Macmillan, New York.
                       Zinke, P.J., A.G. Stangenberger, W.M. Post, W.R. Emanuel, and J.S. Olson. 1984. Worldwide
                       Organic Soil Carbon and Nitrogen Data. ORNUTM-8857. Oak Ridge National Laboratory,
                       Oak Ridge, Tennessee.
               5.6     Endnotes
                        I. "Indirect" greenhouse gases here refers to gases which contribute to the chemical
                        formation or destruction of ozone (O3) in the atmosphere. As O3 is an important
                        greenhouse gas, the gases which create or destroy it affect the radiative forcing of the
                        atmosphere indirectly.
                        2. IPCC (1990). Note fluxes of CO2 are generally expressed in scientific literature as mass
                        of carbon per year. The mass is in I015 grams carbon as CO2 (pg COrC).

                        3. Brown et al., 1986
                        4. Houghton etal, 1987; Melillo etal., 1988
                        5. See, for example, Tans et al., 1990, IPCC, 1992 and Kauppi et al., 1992.
                        6. Delayed releases of non-CO2 trace gases are an important research  issue. These
                        releases may be important, but are currently too uncertain to be included in calculations.

                        7. Houghton, 1991
                        8. For example, see Moore etal., 1981, Houghton etal.. 1983, Houghton etal., 1986,
                        Mellilo et al., 1988, and Emanuel et al., in press.
                        9. Similarly, current land-use will affect future fluxes of carbon dioxide.
                         10. This is what the term "deforestation" should mean and it is frequently accompanied by
                        burning.
                         11. Abandonned lands which are regrowing naturally  may be cleared again. In this case,
                        they should shift again to cleared lands, probably with a lower value for preclearing
                        biomass density.
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             12. Conversion of tropical forests to pasture and cropland accounts for the largest share
             of global forest clearing and resulting CO2 emissions, the discussion and default
             information focus on this case, as it is most important that national inventories account for
             the largest contributions to emissions first. Forest clearing for other purposes (e.g., urban
             development) should also be accounted for to the extent possible, as less default
             information is provided for these cases, this will require national experts to provide input
             data.
             13. For instance, see Houghton, 1991; Crutzen and  Andreae, 1990. The decay rates
             generally depend on several factors including humidity, temperature, and litter quality.

             14. This issue is discussed in the section on possible refinements to the methodology.

             15. The portion of burned carbon that remains on the ground as charcoal is highly
             uncertain. Measurements following burning of a forest for conversion to pasture indicate
             that 2.6% of the pre-burn aboveground carbon, or 8.5% of the burned carbon, is
             converted to charcoal (Fearnside et al., I990a). according to Fearnside (I990b), pastures
             are typically burned two to three times over about  a  10-year period. Under such a
             scenario, the latter burns probably result in combustion of some of the charcoal formed
             during the first burn and formation of additional charcoal. Fearnside (I990b) estimates that
             about 4.6% of the pre-burn aboveground carbon, or 10.1% of the burned carbon,  is
             converted to charcoal under this scenario. Based on results of observations in the
             Brazilian Amazon (Fearnside, I990a) and in a Florida pine forest (Comery,  1981), Crutzen
             and Andreae (1990) adopt charcoal values of 5% of the pre-burn aboveground carbon and
             10% of the burned carbon for clearing in the tropics.
             16. It is important to note, as discussed in the introduction to this document, that there is
             an intentional double counting of carbon emitted from combustion. CO2 is calculated
             based on the assumption that all carbon in fuel is emitted as  CO2. however, methods are
             also provided to estimate portions of total carbon which are emitted as CH4 and CO. the
             reasons for this double counting are discussed in the introduction.
             17. On average about-25-50% of the soil carbon, as discussed in Houghton etal., 1983.
             18. For simplicity of explanation, the discussion refers to the inventory year as though data
             for a single year were the desired input. However, as noted  in the overview, for land use
             and forestry emissions estimates, it is recommended that data averaged over three years
             be used in place of annual data.
             19. Defining regions will require balancing data availability, biological and land-use
             heterogeneity, and practical considerations such as  the available time and effort.
             furthermore, developing adequate land-use and land-use change data is a central issue. In
             the case of land-clearing, this data would likely be obtained from a combination of
             departments of land management, agriculture, and forestry, this data will come at a variety
             of scales in time and space, and producing consistent records will be a challenging task to
             all countries, in time, new internationally-based remote sensing programs could greatly
             facilitate this task; this is discussed in the technical appendix.
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                       20. As in the case of land-use data, developing appropriate biomass data is a challenging
                       task, in theory, it can be obtained directly by destructive sampling but this is unrealistic for
                       adequate coverage for even small countries, an alternative approach is to use inventory or
                       production data where one exploits volumetric data on marketable timber and uses a
                       sequence of expansion factors to convert this to total stemwood, total above ground
                       biomass volume, and total biomass volume, see the references to Tables  I and 2.

                       21. Houghton et al., 1987.
                       22. For instance, see Houghton, 1991; Crutzen and Andreae, 1990.

                       23. Note also that the smoldering that produces charcoal and ash also forms other
                       important greenhouse gases such as CH4 and N2O. for instance, see  Fearnside et al.,
                       I990a and Crutzen and Andreae, 1990.
                       24. We are also ignoring the carbon flux associated with CO formation during combustion
                       which accounts for about 8% of the burned carbon.
                       25. The range most cited is (0.43 - 0.58) hence some suggest that 0.5 as a more
                       appropriate default assumption.
                       26. See Houghton 1991;  Crutzen and Andreae  1990 for discussion of this issue.
                       27. In temperate systems, in fact, most of the soil carbon is released  in the first 5 years
                       after clearing; the rest is  released over the next 20 years, see Houghton, 1991.

                       28. See Houghton et al.,  1983.
                       29. The issue of soil carbon  change following land-clearing in the tropics is an important
                       research topic, there is evidence that there is a rapid soil carbon loss follow by soil carbon
                       accumulation depending  upon the type of grasses that are used in pasture, (e.g., Fearnside,
                        I960, 1986; Buschbacher, 1984; Cerri etal., 1988; and Lugo etal., 1986); and clear cutting
                       of tropical forests does not appear to release soil carbon (Keller et al., !986).The current
                       status of the science, however, may not provide an adequate basis for recommending
                       values for inclusion of this aspect of the  carbon cycle in emissions calculations at this time.
                       further research needs to be done.
                       30. The emission ratios used in this section are derived from Crutzen and Andreae (1990),
                       and  Delmas, 1993, as presented in the table, they are based on measurements in a wide
                       variety of fires, including forest and savanna fires in the tropics and laboratory fires using
                       grasses and agricultural wastes as fuel. Research will need to be conducted in the future to
                       determine if more specific emission ratios, e.g., specific to forest fires, can be obtained.
                       also, emission ratios vary significantly between the flaming and smoldering phases of a fire.
                       coj, n2o, and nox are mainly emitted in the flaming stage, while CH4 and CO are mainly
                       emitted during the smoldering stage (lobert et al., 1990). The relative importance of these
                       two stages will vary between fires in different ecosystems and under different climatic
                       conditions, and so the emission ratios will vary. As inventory methodologies are refined,
                        emission ratios should be chosen to represent as closely as possible the  ecosystem type
                        being burned, as well as  the characteristics of the fire.
                        31. Emissions inventory  developers are encouraged to provide estimates of uncertainty
                       along with these best estimate values where possible, or to provide some expression of
                        the  level of confidence associated with various point estimates provided in the inventory.
                        procedures for reporting this uncertainty or confidence information are discussed in
                        Volume 1: Reporting Instructions.

                        32. Crutzen and Andreae, 1990.
                        33. From Crutzen and Andreae, 1990.
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            34. There is an inconsistency in the methodology in the treatment of the full molecular
            weight of NOX. In fossil energy and industry discussions NOX is expressed as though all of
            the N were in the form of NO2. In biomass burning literature, (e.g., Crutzen and Andreae,
            1990) NOX is often discussed as though the emissions were in the form of NO. Therefore,
            the biomass burning discussions in these guidelines convert NOX-N to full weight using the
            conversion factor (30/14) for no. all other references to NOX are based on the full weight
            of NO2 (i.e., the conversion factor from NOX-N would be 46/14).

            35. See Houghton et al.,  1983.
            36. Post, etal., 1982.

            37. See Houghton et al.,  1983.
            38. Values given in Table 5 assume linear regrowth of aboveground biomass in each of the
            two time periods (0-20 years and 21-100 years). In reality, as shown  in Brown and Lugo
             1990, the regrowth is closer to an exponential function, the calculation could be improved
            by breaking the 20  year period into finer segments, assuming availability of data, to
            determine a weighted average.
            39. The re-accumulation of carbon in soils  is not linear. Generally accumulation occurs
            quickly in initial stages of regrowth and slows as regrowth slows.
            40. Plantations are  forest stands that have  been established artificially, to produce a forest
            product "crop". They are either on lands that previously have not supported forests for
            more than SO years (afforestation), or on lands that have supported  forests within the last
             50 years and where the original crop has been replaced with a different one
             (reforestation) (Brown et al., 1986).
            41. There is one omission in this accounting which may be important for some countries.
             If plantations are established  on previously non-forest lands, there may be a long term
             accumulation of carbon in the soil as a result of the land use change, this would not
             normally be picked up in the simple managed forest calculations. It could be added if
             national experts have-detailed data on the  pre-plantation land uses, The soil carbon
             contents and rates of accumulation, etc.
             42. In addition, logging provides access to  previously unaccessible forests, thereby
             facilitating degradation of forests by activities such as fuelwood collection, habitation,  and
             agricultural activity.
             43. Volume to mass conversions and expansion factors are taken from Brown et al.,  1989
             which reports on tropical forests, however, The values are in the range of those reported
             by ECE/FAO,  1985, for temperate forests.
             43. Holt and Spain, 1986
             44. e.g. Anderson  et al., 1988 and Levine et al., 1988
             45. Luizao etal., 1989

             46. Bowden and Bormann, 1986

             47. Keller et al., 1986
             48. Luizao etal., 1989and Matson etal., 1990
             49. Keller et al., 1990; Scharffe et al., 1990.
             50. See, for example, Fearnside,  1980, 1986; Bushbacher, 1984; Cerri et al., 1988; and
             Lugo et al., 1986. Keller et al. (1986) indicate that clearcucting of tropical forests does not
             appear to release  soil carbon.
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                       S[. Hosier etal. 1991

                       52. Seller and CrutzenK 1980

                       53. In fact, prescribed burning may actually result in a net accumulation of carbon when
                       the natural ffre that would have occurred (had prescribed burning not taken place) is
                       included in the accounting of emissions.

                       54. Actually, following the first clearing (Le., clearing of primary forests), the forest hiomass
                       may not recover fully to its original density during the fallow period, but instead reaches a
                       slTgjhtly reduced leve), referred to as a secondary forest, after this point, however,  clearing
                       (of a secondary forest) is balanced by recovery (to a secondary forest), and netCOj
                       emissions over time are zero.

                       55, See Myers (1989) and Houghton {1991)

                       56, Generally, shifting cultivation is practiced in fallow forests, since the  least dense and
                       most accessible forest areas are most susceptible co this form of clearing. Abaveground
                       biomass density estimates for fallow forests are highly uncertain, and vary significantly both
                       within and among countries because of varying ecosystem types as well as varying intervals
                       between clearings. As a rough estimate* 50% the biomass estimates fjor unproductive
                       forests can be used (see Table 6-1 for regional estimates In. units of carjbptvper hectare),
                       Biomass carbon densities for other forest types, e^j., undisturbed forests, should of course
                       be used if more appropriate in specific cases.

                       57. Cicerone and Greenland, 1988                           .,'.'.'.'

                       58. Moore and Knowles, 1989                              ~   '.'",'
                       59, For example, see Harriss et a!., 1982

                       SO. Seiler and Conrad, 1987                                   ~'  \_ _
                       6L Seller and Conrad, 1987           "       ;   '         =   =-

                       62, Seifer and Conrad, 1987                                       '
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             T5    TECHNICAL APPENDIX:

                     DEFORESTATION DATA

             Data on rates of deforestation1 are essential for calculating the fluxes of carbon dioxide
             and other trace gases between terrestrial systems and the atmosphere. When arranged on
             a country-by-country basis, these data provide the forcing function for computation of
             country-specific emissions from forest clearing. Recogni::ing that such data sets are not yet
             available for many countries with the accuracy needed for these computations, this
             technical appendix provides suggestions for utilizing the available global and national
             sources of data, while bringing new or better sources of information into the calculations
             when and where they are available.


    T5.I  Food and  Agriculture  Organization  (FAO)
             Published  Data

             Currently, the most comprehensive international source1 of data on rates of deforestation
             broken down to the country level is maintained by the FAO in the following forms:

             I    Source data, preferably in the form of a time series, collected in cooperation with
                 member countries (i.e., without standardization) including data on: forest cover,
                 ecofloristic zone and sub-national boundaries, biomass, plantations and conservation,
                 collected and compiled in the form of a geographic information system.
             2   Standardized estimates of forest cover, rate of deforestation, afforestation, and
                 biomass/ha at the country level. Standardization is done by FAO because of variations
                 from country to country in:
                 •   -the definitions of "forest", "deforestation" and "afforestation"; and
                 •   -the reference years for forest cover and deforestation measurements.
                 The standardization is intended to bring country data to common definitions of
                 forest cover and reference data, and to make the country information useful for
                 regional and global studies. The basis for standardization is adjustment functions by
                 ecological zones based on time-series data on forest cover of countries.
             3   Data from a global sample survey of forest cover slate and change during 1980 and
                  1990 based on a limited  sample of high resolution satellite images using common
                 definitions and measurement techniques. The main aim of this survey is to calibrate
                 regional and global estimates and provide comprehensive information on various
                 types of on-going forest cover changes, in the form of change matrices (1980 and
                  1990). It should be noted that the sample survey is not intended to check or replace
                 country estimates, but only to provide reliable estimates (i.e., with standard error) of
                 forests cover and rate of change at regional/global fevels. This is being done taking
                 into account the inherent limitations of aggregating heterogeneous country data at
                 regional/global levels.
                    This appendix is limited to discussion of current and future international sources
             of data on rates of deforestation at the national level. It is understood, however, that
             other types of input data are also key sources of uncertainty in calculation and are also the
             subject of a great deal of ongoing activity. This includes other types of land use change and
             land cover data as well as more  detailed information on growth  rates and biomass
             densities for different types of forests and other ecosystems.
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                      The results of these data collection and analysis efforts are provided in a series of
                      publications produced by the FAO. These data can be used to construct national input
                      data for calculating COj from deforestation. This should be useful to many countries at
                      least as a point of comparison with locally available data sources, and may be used to
                      provide a first order estimate of national emissions if desired by national experts.

                      The FAO Forest Assessment produced in the early 1980s (FAO/UNEP 1981, Lanly r982)
                      provides a first-order estimate of deforestation rates worldwide.  These data produced on
                      a country basts can be used as a baseline land use rate. An interim assessment (FAO  1988)
                      provided deforestation rates by country for the period 1981-85. A 1990 assessment has
                       been recently published (FAO I993)» which provides estimates of deforestation rates by
                       country for the period 1981-1990. Thus, some estimates of current and historic rates of
                       deforestation on a country basis can be obtained from these published reports. More
                       detailed information, including sub-national data, can be obtained by contacting the FAO
                       dtrecdy,
                       It should be noted, however, that there have been controversies and disagreements
                       regarding FAO estimates of national deforestation rates at times. In some cases where
                       national experts  have developed significantly more detailed approaches for their own
                       countries, results have been found to be significantly different than  die published FAO
                       estimates. (See, for example, Fearnside, et al, f990b for Brazil). Any internationally
                       provided data should be reviewed carefully by national experts if they are used as a basis
                       for emissions Inventory estimates.
                       Some countries have well-developed estimates of deforestation, based on very good
                       measurements, which provide more detail than is available from the FAO assessments
                       (eg,, Arbhabhirama et al. 1987,1NPE 1992). Where detailed national studies exist for die
                       earty 1990s they may be a preferred data source for experts preparing national
                       Inventories. FAO data may nonetheless be useful for comparison purposes. The choice of
                       input data Is always ultimately a decision of the national experts.
                       Lack of consistent time-series data at national level is considered by FAO staff to be die
                       most critical problem in estimating die deforestation rate. Variation in definitions and
                       measurement techniques from country to country is another problem in making regional
                       and global estimates. FAO has initiated a comprehensive programme for capacity building
                       to forest resources assessment by mobilizing technical and economic cooperation among
                       member countries and among concerned regional and global agencies as follow-up to
                       recommendations of UNCED Agenda 21: Programme Area D.
              T5.2 Ongoing  Data  Efforts
                       The lack of a comprehensive data set on deforestation rates is a critical problem. The
                       development of such data sets remains one of the priorities for the 1PCC process in the
                       coming years (IPCC 1992). Methods using high resolution remote sensing rn conjunction
                       wldt geographic information systems appear most promising. The  International
                       Geosphere-Biosphere Programme's Data Information System 0GBP-DIS) is serving as a
                       central focal point to collect and disseminate information about the various ongoing
                       activities and data sets dealing with land use and changes in land cover. The IGBP-DIS is
                       located in Paris, France (Tel: 33-1-4427-6168, Fax: 33-1-4427-6171).
                       Experts from around the world have begun to build the scientific, technical, and
                       procedural underpinnings of such a system. The World Forest Watch Meeting held in Sao
                       Jose dos Campos, Brazil (June 1992) provided a high-level international forum for the
                       assessment of current approaches  to satellite-based forest monitoring. This meeting also
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             served as a basis for forwarding recommendations from the technical and scientific
             communities to the policy makers and government leaden; at UNCED*

             A variety of international participants were represented at the World Forest Watch
             Conference. The conference concluded that significant technical and methodological
             advancements have been made in recent years, and they are now sufficient for proceeding
             with an observation system which could satisfy both scientific and national-level forest
             management requirements. A priority action now is to establish a fully functional,
             permanent monitoring system. The system would support national forest management,
             global change science, and international policy information needs, such as those of the
             IPCC.

             The current research and development being carried out in laboratories and research
             centers around the world has shown that it is now feasible; to acquire repetitive satellite
             data sets over very large areas, and that the information derived from such data sets can
             form the core of a global forest monitoring program. The International Space Year World
             Forest Watch Conference has recently provided illustrations that space observation
             technology and the community of users are ready for regional and global applications.

             Progress made on two forest monitoring projects is worth noting in this respect.
              I    The National Institute for Space Research (INPE)  of i:he Secretariat of Science and
                  Technology of the Presidency of the Republic of Bra2:il has made surveys of the entire
                  Legal Amazon (about 5 million square kilometers) using LandSat images. This survey
                  was first conducted in 1978 (with 1977 and 1979 being used to cover areas covered
                  by clouds in the 1978 imagery. The studies were repeated in 1988, 1989, 1990 and
                  1991. These space-based surveys mapped the extent of gross deforestation (i.e.,
                  without accounting for forest regeneration or the establishment of plantations) in the
                  portion of the Legal Amazon  covered by forest. The ecosystems ranged from dense
                  tropical forest to thick savannas (cerradao) with a total surface area between 3.9 and
                  4 million square kilometers. The 1978 survey used 232 Land Sat MSS black and white
                  images based on channels 5 and 7 at a scale of 1:250,000. The more recent studies
                  used 229 LandSat TM images  annually in a color composite of channels 3,4 and 5 at a
                  scale of 1:250,000.
             2   In 1990 NASA, in conjunction with the United States Environmental Protection
                  Agency and the U.S. Geological Survey, began a prototype procedure for using large
                  amounts of high resolution satellite imagery to map the rate of tropical deforestation.
                  This activity, the LandSat Pathfinder Project, builds on experience gained during a
                  proof-of-concept exercise as  part of NASA's contribution to the International Space
                  Year/World Forest Watch  Project. It focused initially on the Brazilian Amazon, and
                  has now been expanded as part of NASA's Earth Observing System activities to
                  cover other regions of the humid tropical forests.
                  This project has succeeded in demonstrating how to develop wall-to-wall maps of
                  forest conversion and re-growth. The project is now in the process of extending its
                  initial  proof-of-concept to a large-area experiment across Central Africa, Southeast
                  Asia and the entire Amazon Basin. The project is acquiring several thousand LandSat
                  scenes at three points in time — mid 1970s, mid 1980s, and mid 1990s — to compile a
                  comprehensive inventory of deforestation and secondary growth (regrowth of
                  forests on land cleared and subsequently abandoned) to support global carbon cycle
                  models. Methodology and procedures have been identified. Although this exercise is
                  being implemented for most of the tropics, it is not an operational global program. In
                  principle it  will provide an initial large-scale prototype of an operation program.
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                            The use of geographic information system technology is crucial to die project, as it
                            provides the overall framework upon which the raw satellite data can be synthesized
                            with other cartographic, numerical, and geographical data for scientific research and
                            national forestry management As its name implies, this project is exploratory, but it
                            could readily be expanded to form the nucleus of a global scale operational program.

                        These two projects demonstrate the feasibility of developing a global tropical forest
                        information system to support an operational tropical forest monitoring program. High
                        resolution satellite data from LandSat or Spot satellites are being used to provide digital
                        maps of deforestation.
                        High resolution data from the LandSat series of earth observation satellites can be
                        employed to make regular measurements of deforestation. Urge amounts of these data
                        exist in national and foreign archives, dating back approximately 20 years. This satellite
                        data system has been perfected over years of development (5 satellites have been
                        launched) and it is expected to be an operational system into the next century (LandSat 6
                        is ready for launch, 7 and 8 are being designed). This system is complemented by the
                        French SPOT satellites. Thus, a continuous and  consistent source of data is available upon
                        which a high resolution, fine-scale (1:250,000 scale mapping) information system could be
                        developed.
                        An operational forest monitoring using high resolution data such as that provided by
                        LandSat and SPOT could provide wall-to-wall mapping for the entire tropical zone. The
                        approach would be as follows:
                        •    An initial mapping effort would define where and how much deforestation exists in
                             die tropical forests (a baseline assessment). The stratification of forest types and
                             critical regions could be enhanced by the use of coarse resolution information from
                             AVHRR.
                        •    Acquisition of LandSat and/or SPOT imagery can  be coordinated regularly ever/ 3-5
                             years to obtain cloud-free coverage systematically throughout the tropics. The best
                             way to achieve tfiis is to rely heavily on the foreign ground stations. For example,
                             from die LandSat routine and complete coverage for die Amazon Basin and
                             Southeast Asia is possible from several foreign ground receiving stations in  these
                             regions. As a rule diese stations regularly  collect data from every orbital pass within
                             the line-of-sight radius of their antenna. For regions, such as central Africa where no
                             ground station exits, programmed acquisitions from die satellite are possible.

                        »    The imagery are analyzed for deforestation using a methodology analogous to that
                             developed by die LandSat Pathfinder Project, where a simple delineation of the
                             boundary between intact forest and cleared areas is recorded into a geographic
                             information system. Areas of secondary growth would also be delineated. Subsequent
                             years are compared  to die baseline and die increment of new deforestation and
                             secondary growth is recorded. The resulting data set provides a 1:250,000 to
                              1:500,000 scale map of deforestation at a regular repeat interval, and from  diis a rate
                             of deforestation is derived.
                        •    These geographically-referenced measurements can directly support the
                              implementation of die (PCC national inventory methodology, which requires a time
                              series of historic forest clearing data, and would require updating at periodic
                              intervals. The proposed accurate and precise deforestation data set would be an
                              important asset to national experts working to implement the IPCC methodology for
                              national  emissions and removals from land use change.
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                    An accuracy assessment effort will need to be put into place to define and track the
                    measurement variance and error. This component will need to determine accuracy
                    with respect to: (a) variance due to positional accuracy (i.e., the mapping precision)
                    and (b) the variance associated with image interpretation.

                    An effort focused on establishing in-country cooperation will be necessary. Such
                    cooperation fulfills several ancillary but vital objectives: (a) it builds a process of
                    national acceptance of the methods and  results through active involvement, (b) it
                    provides a mechanism for technology transfer and training for eventual
                    implementation of remotely sensed-based national inventories, (c) it facilitates
                    logistical coordination of the field component, (d) it provides direct cooperation at
                    various foreign ground stations, and (e) it enables cooperation with national and
                    regional experts in the interpretation of imagery.
     T5.3  Summary

               Tropical deforestation and carbon emissions are important: components of both science
               and policy. Yet, in spite of the growing need for precise estimates of deforestation to
               support both international policy and basic research, an operational program of
               measurement, monitoring and mapping has yet to be developed. Comprehensive and
               systematic information on the extent of forest and forest loss is not available on a global
               basis. The latest IPCC Assessment Report, for example, considers the rate of tropical
               deforestation to be one of the key unknowns in global climate change assessment. Any
               lasting and effective implementation of a global system of national  emission inventories to
               support the IPCC and other international processes will require a new, concerted effort
               to measure and map tropical deforestation, and develop the database necessary for other
               important components of the  calculations. These measurements of deforestation from
               high resolution satellite remote sensing can also support the UN/FAO Forest Assessment
               by providing quantitative and spatially comprehensive  measures of changes in forest cover
               for the tropics.

               This Technical Appendix summarizes the most comprehensive current data source for
               tropical deforestation information, and discusses ongoing efforts to improve on this data
               via analysis of remote sensing images. Ideally, each country would  like to have data on their
               land use changes and associated trace gas emissions and uptake over the past 40 to 50
               years so that their estimates of current annual net emissions would include delayed and
               continuous emissions and uptake  due to activities that occurred in prior years. Since this is
               not the case for many countries, the methodology described has made simplifying
               assumptions in order to treat the effects of past land use activities on current emissions.
               This appendix provides some perspective on the available international sources for dealing
               with one key data gap — data on rates of forest clearing over time.

               In future editions of the Guidelines, it may be possible to include more information on data
               available to assist national experts as a result of some  of the ongoing efforts described in
               this version. It may also be possible and desirable to provide similar discussion of a range
               of other international data collection efforts which may assist national experts in refining
               other key data driven uncertainties in the national estimate:; of emissions and removals
               from land use change and forestry.

               In the meantime, it is recommended that countries continue efforts to collect historical
               records of land use change and develop systems of tracking land use through time so that
               as the methodology is further refined, the land use change time series needed to account
               better for emissions and uptake of carbon dioxide and other trace gases are available.
PART 2
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                         CHAPTER 6
                 METHANE EMISSIONS
                       FROM WASTE
PART 2
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             6        METHANE EMISSIONS  FROM WASTE

             Disposal and treatment of industrial and municipal wastes can produce emissions of most
             of the important greenhouse gases (GHG). Solid wastes ca,n be disposed of through
             landfilling, recycling, incineration, or waste to energy. GHG emissions from waste to
             energy, where waste material is used directly as fuel or converted into a fuel, should be
             calculated and reported under Energy - Chapter 2. Liquid wastes can be dealt with
             through various forms of wastewater treatment. In addition, sludge from wastewater can
             be incinerated. This chapter will deal with emissions resulting from landfilling of solid
             waste, treatment of liquid wastes, and waste incineration.

             The most important gas produced in this source category is methane. Significant amounts
             of the annual global methane produced and released into the atmosphere are a by-product
             of the anaerobic decomposition of man-made waste. Two major sources of this type of
             methane production are landfills and wastewater treatment. In each case, the
             methanogenic bacteria break down organic matter in the waste to produce methane.
             These sources are treated in detail in later sections of this chapter.

             Landfilling of solid waste represents the major form of solid waste disposal in the
             industrialized world. (OECD, 1993)  In addition to CH4, landfills also can produce
             substantial amounts of CO2 and non-methane volatile organic compounds (NMVOCs).
             CO2 is primarily from decomposition of organic material derived from biomass sources
             (e.g. crops, forests) which are regrown on an annual basis. Hence, these are not treated as
             net emissions from waste in the IPCC methodology. If biomass  raw materials are being
             unsustainably produced, the net CO2 release should be calculated and reported under the
             Agriculture or Land Use Change and Forestry sections.

             The process of wastewater treatment produces NMVOCs as well as CH4. (Bouscaren,
              1992) Wastewater treatment is also now being studied as a source of N2O. Norway
             (IPCC, 1993) and Japan (Kyosai and Mizuochi, 1993) have documented N2O production
             from their sewage treatment processes.  Future evaluation of ongoing research will give an
             indication of the importance of this source.

             Waste incineration, like all combustion, can produce CO2, CH4, CO, NOX, N2O and
             NMVOCs. No detailed methodologies are provided for this source category. Instead, the
             section on waste incineration later in this chapter provide:; references to other major
             methods documents already available for some gases. For CH4 and N2O it is only possible
             to report preliminary estimates and research results at this time. Further studies are
             needed to give more information about GHG emissions from this source category.

             The sections in this chapter dealing with landfills and wastewater treatment give
             background information on the source, a description of the methodology to estimate
             methane production only, and uncertainties associated with estimating emissions. This is
             consistent with the initial priorities under the IPCC methodology programme. National
             experts are encouraged to report any other relevant emissions for which data are
             available, along with documentation of methods used. This will greatly assist in the
             development of more complete methods for future editions of IPCC guidelines. For
             information on estimation procedures and emissions factors for other GHGs which are
             currently not provided in this chapter, experts should consult extensive existing literature
             developed by other emissions inventory programmes. Some key examples are:

             •    CORINAIR Default Emissions Handbook  (Bouscaren,  1992);

             •    U.S.  EPA's Compilation of Air Pollutant Emissions Factors (AP-42) (US EPA, 1985)
                  and Supplement F (AP-42) (US EPA, I993a);
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                            Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions inventory
                            (Stockton and Steiiing, 1985);
                            Air Emissions from Municipal Solid Waste Landfills - Background Information for
                            Proposed Standards and Guidelines (US EPA, 1991 a).
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             6.1    METHANE  EMISSIONS  FROM
                      LANDFILLS
    6.1.1 Introduction

             Since the early 1980s, it has been recognized that the methane component of landfill gas
             can be a local environmental hazard if precautions are not taken to prevent uncontrolled
             emissions or migration into surrounding land. Gas can migrate from the landfill either
             laterally or by venting to atmosphere, and this can cause vegetation damage and unpleasant
             odours at low concentrations, while at higher concentrations the gas may form explosive
             mixtures.
             More recently, increasing attention has focused on the role of methane in global
             atmospheric change. Methane from landfills contributes a significant proportion of annual
             global methane emissions, although the estimation is subject to a great deal of uncertainty.
             Estimates of global methane emissions from landfills range from 20 to 70 Tg/yr, global
             anthropogenic sources emit about 360 Tg/yr, which suggests that landfills may account for
             6 to 20% of the total. (IPCC,  1992)
             This section will describe the processes that result in landfill gas generation and the factors
             which affect the amount of methane produced within landfills. It will then describe
             methodologies for estimating methane emissions from landfills. One of these methods is
             proposed as a default base method with which all countries can comply. Other methods
             are also described as well  as some examples  from various countries that have applied
             them. The section also discusses sources of uncertainty associated with any estimates of
             methane emissions from landfills, in particular the availability and quality of data required.
    6.1.2 Landfill  gas  generation

             Organic waste within landfills is broken down by bacterial action in a series of stages that
             result in the formation of methane, carbon dioxide and further bacterial biomass. In the
             initial phase of degradation, organic matter is broken down to small soluble molecules
             including a variety of sugars. These are then broken down further to hydrogen, carbon
             dioxide, and a range of acids. These acids are then converted to acetic acid which,
             together with hydrogen and carbon dioxide, forms the substrate for growth of
             methanogenic bacteria.
             Landfills are by nature heterogeneous, and all microbiological investigations into landfill
             characteristics have shown that there are considerable differences between different
             landfills and even different regions within the same landfill (Westlake, 1990). This makes it
             very difficult to extrapolate from observations on single landfills to predictions of global
             methane emissions. Nevertheless, there are a number of significant factors which influence
             the generation of methane and its emission from landfills. A better understanding of these
             factors can reduce the uncertainty associated with emissions estimates.
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              6.1.3 Factors  influencing methane  production  in

                       landfills

                       The factors which influence methane production within landfills have been reviewed
                       comprehensively elsewhere (eg. Peer el a!., 1993; US EPA, 1992; US EPA, 1991 b; US EPA,
                       1991 c; Lawson and Alston, 1990; Augenstein and Pacey, 1991), therefore this section will
                       only provide a brief summary of the most significant factors relating to methane emissions.


                       Waste  management  practices

                       The two main types of waste management practices of concern for CH4 emissions are
                       open dumping, which is generally practiced in developing regions, and sanitary landfilling,
                       generally practiced in developed countries and urban areas of developing countries. Both
                       of these types of waste management can result in- methane production if the waste
                       contains organic matter.
                       In open dumping, wastes are disposed of in shallow, open piles, generally only loosely
                       compacted, and with no provision for control of any pollutants generated, either gas or
                       leachate. Scavenging by animals and humans can remove much of the biodegradable wastes
                       therefore reducing substrate availability.
                       Wastes in open dumps generally decompose aerobically, producing carbon dioxide.
                       However, there is anecdotal evidence that some methane production can occur
                       (Thorneloe et al., 1991), but this has not been quantified. Methane from open dumping is
                       therefore not included in any methodology considerations for global inventories. Bhide et
                       al  (1990) reported biogas recovery from two uncontrolled landfills in Nagpur, India. The
                       CH4 content of the biogas from one site was 3Q to 40%. This suggests that open dumps
                       are a source of CH4.
                       Thorneloe et al. use the  same methodology to calculate CH, emissions from open
                        dumping in non-industrialized countries as from sanitary landfills in industrialized regions.
                        However, total CH4 emissions are reduced by 50% to account for the differences between
                        CH, production potential from open dumping and sanitary landfilling. The choice of 50% is
                        arbitrary and should be updated when additional data are available. This procedure can be
                        used by national experts at their discretion. Uncertainty due to this source is discussed
                        later.
                        Sanitary landfills are designed specifically to receive wastes. Landfill design and
                        management is becoming increasingly sophisticated in many countries, as the serious
                        environmental consequences of uncontrolled landfilling are becoming understood. New
                        landfill design standards in many countries are ensuring that landfills are lined before
                        receiving waste, and also that there are adequate provisions for the safe control, and
                        removal where appropriate, of gas and leachate generated. Good waste management
                        practices ensure that the waste is compacted to minimise use of void space, also that it is
                        covered both with intermediate daily cover and with an effective cap when final
                        restoration takes place. The costs associated with these management practices are
                        encouraging the development of larger landfills to economise on scale, taking in greater
                        quantities of waste. All of these factors can  encourage the rapid development and
                        maintenance of anaerobic conditions within the landfill, and hence ensure continued
                        methane production.
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             Waste  composition

             The composition of waste is one of the main factors influencing both the amount and the
             extent of methane production within landfills. Municipal solid waste (MSW) contains
             significant quantities of degradable organic matter. This can decompose to form acetate
             and carbon dioxide as intermediate decomposition  products, which are the main
             substrates for methanogenic bacteria. Different countries and regions are known to have
             MSW with widely differing compositions: wastes from developing countries generally have
             a high putrescible content, whereas developed countries, especially in North America,
             have very high paper and card content in their MSW. Thus landfills in developing countries
             will tend to stabilise within  10-15 years because putrescible material decomposes rapidly,
             whereas landfills with a high paper and card content will tend to produce methane for 20
             years, or more at a lower rate.
              Physical factors

              The moisture content of the landfill environment is one of the principal physical factors
              influencing landfill gas production. Moisture is essential for cell growth and metabolism,
              also for transport of nutrients and bacteria within the landfill. The moisture content of a
              landfill will depend on the initial moisture content of the waste, the extent of infiltration
              from surface and groundwater sources, and on the amount of water produced during the
              decomposition processes.

              Temperature will affect the growth rate of the bacteria. Under anaerobic conditions,
              landfill temperatures are generally between 25-40°C. These temperatures can be
              maintained within the core  of the landfill independent of the external temperatures.
              Outside of these temperatures, methane production is reduced or can cease altogether.

              Optimal pH for methane production is between 6.8 and 7,2. Nutrients that are important
              for efficient bacterial growth include sulphur, phosphorous, sodium and calcium. CH4
              production rates decrease sharply with pH values "Below-about 6.5 (Zehnder, 1982). When
              refuse is buried in landfills, there is often a rapid accumulation of carboxyte acids^thjs
              results in  a pH decrease and a long time lapse between refuse burial and the onset of CH4
              production ranging from months to years.

              "The lapsed time preceding the onset of CH4 production in landfills is an important aspect
              when considering the management of individual landfills for biogas recovery or emissions
              mitigation. The age at which landfills and uncontrolled dumps begin to produce CH4 is of
              lesser importance when evaluating global CH4 emissions from MSW management systems.
              For estimating global emissions, it is the total CH4 production potential that is more
              critical." (Thorneloe, 1993a)

              The importance of these physical factors to methane generation can be demonstrated
              within controlled laboratory conditions, but the heterogeneity of landfills makes definitive
              research very hard under field conditions, and there are limited data available. Therefore
              until better global data become available, none of these factors can be taken into
              consideration when estimating national or global methane emissions.
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              6.1.4Methodologies  to  estimate  methane

                       emissions from  landfills

                       A number of methods have been used to estimate methane emissions from landfills. These
                       methods vary widely, not only in the assumptions that they make, but also in their
                       complexity, and in the amount of data they require for the determinations.

                       This chapter will deal only with those methods that can be applied to whole regions or
                       countries. There are some very complex models that are concerned with movement of
                       methane and other gases through individual landfills; however these models cannot be
                       applied to landfill populations and therefore will not be considered further here.


                       Mass  balance  and theoretical  gas yields
                       methodologies

                       This is the simplest method for calculating methane emissions from landfills. It is based on
                       a mass balance approach, and does not incorporate any time factors into the methodology.
                       The calculation assumes that an instantaneous release of methane takes place from refuse
                       during the same year that the refuse is landfilled.

                       Using empirical formulae
                       At its simplest level, an empirical formula for refuse can be used as the starting  point for
                       estimating yields from waste. If a complete breakdown to carbon, hydrogen and oxygen is
                       considered, this gives very high and unrealistic levels of methane generation, therefore
                       some adjustments  are necessary because complete breakdown is known not to take place.
                       EMCON Associates (1981) modified this by using an extended Buswell equation, which
                       takes other elements into account, and estimated that 53% of the carbon content of
                       refuse is converted to methane. If microbial biomass as an end product is also taken into
                       account, then this further reduces the methane generation potential. Polytechnic of East
                       London (1992) have predicted that this results in the production of 234 m3 of methane
                       per tonne of wet MSW.

                       Default methodology: using degradable organic carbon content
                       A more useful approach is to consider the degradable organic carbon (DOC) content of
                       MSW, i.e. the organic carbon that is accessible to biochemical decomposition, and to use
                       this value to calculate the amount of methane released from the MSW. This is the
                       approach taken by Bingemer and Crutzen (1987), who segregated the world into four
                       economic regions, and applied different values of DOC to the waste generated within each
                       of these regions. As a simple and robust method, this is  currently the most widely
                       accessible default methodology for calculating country-specific emissions of methane from
                       landfills, since it requires the least amount of data to perform the calculations, and it can
                       be modified and refined as the amount of data available for each country increases.

                       The four regions derived by Bingemer and  Crutzen (1987) were: US, Canada and
                       Australia; other OECD; USSR and Eastern  Europe; and developing countries. In their
                       assessment, they determined how much MSW was produced for each region, and how
                       much of that MSW was degradable organic carbon.

                       The percent degradable organic content (DOC) is based on the composition of waste.
                       The percent of DOC can be calculated from a weighted average of the carbon content of
                       various components of the waste stream. Bingemer and Crutzen (1987) collected data for
                       the various global regions considered in the study. No data were available for the USSR or
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                                                                                                           WASTE
              Eastern Europe or for some developing countries, so these values had to be
              approximated. These data were updated by OECD (1991) using more recent data from
              OECD (1989) where available. The data presented to OECD (1991) are summarized in
              Table 6-1. It is highly recommended, however, for countries where the composition of the
              fractions in the waste stream are known, that these be combined with a knowledge of the
              carbon content of these various fractions to produce a country-specific value for DOC.

              The determination of annual methane emissions for each country or region can then be
              calculated from Equation 6.1
                                                EQUATION 6.1
                     Total MSW generated (Gg/yr) x Fraction MSW landfilled x Fraction DOC in
                        MSW x Fraction Dissimilated DOC x 0.5 g C as CH4/g C as biogas x
                                Conversion factor (16/12) - Recovered CH4 (Gg/yr)


                                               Methane emission
              Total MSW generated can be calculated from Population (thousand persons) x Annual MSW
              generation rate (Gg/thousand persons/yr).

              In developing countries only urban populations are considered, since the rural populations
              are assumed to dispose of their waste in very small open clumps, where significant
              methane generation is assumed not to occur.

              Fraction dissimilated carbon: This is the portion of carbon in substrates that is converted to
              landfill gas. The assimilated fraction is the remainder of carbon that is used to produce
              new microbial cell material. To date, estimates of how much carbon may be dissimilated
              have relied on a theoretical model that varies only with the  temperature in the anaerobic
              zone of a landfill: 0.014T + 0.28, where T = temperature (Tabasaran, 1981). The
              temperature in the anaerobic zone of a landfill is thought to remain constant at about
              35°C, regardless of ambient temperature (Bingemer and Crutzen, 1987). Therefore
              applications of the Bingemer and Crutzen (1987) method use a figure of 0.77 dissimilated
              DOC.

              No allowance was made for any reduction in methane emissions from methane oxidation,
              also it was assumed that all waste decomposed anaerobically within the landfill rather than
              aerobically.   •

              Using the data that they had collected, Bingemer and Crutzen (1987) estimated that global
              emissions of methane from landfills ranged between 30 - 70 Mt per year.

              As an example, an estimate for the US can be derived as follows (based on values provided
              by the US  EPA):
                      Assumptions:
                      Waste generated:

                      % waste landfilled:
                      % DOC:

                      % DOC dissimilated:
                      Recovered methane:
about 235 Tg/yr to landfills

up to 80
21
77

I-5 Tg/yr
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                        These assumptions yield an estimate of:
                                ((235 Tg/yr x 0.80 x 0.21 DOC x 0.77 Dissimilated DOC x 0.5 kg C as
                                CH.,/kg C as biogas x 16/12) - 1.5 Tg/yr) =  19 Tg/yr
                        OECD (1991) also cites a study by Piccot et al. {1990) who surveyed 31 countries through
                        literature review and personal communication, resulting in country-specific factors of
                        MSW generation rates per capita, waste composition and percentages of waste landfilled.
                        These values are given in Table 4.2 of OECD (1991); however they have been subject to
                        criticism from some countries and some OECD Workshop participants who were
                        concerned that the data may not be very representative of their countries or regions.

                        It is proposed that the methodology of Bingemer and Crutzen (1987) remains as the
                        methodology that can be used by all countries to calculate methane emissions estimates
                        from their landfills. The Workbook provides a detailed step-by-step version of this
                        methodology as well as default values (as discussed above) for factors to be used where
                        they are not already available from within each country.

                        Limitations to this methodology
                        However, there are limitations to this methodology which  have resulted in criticism from
                        researchers who have tried to apply it in their own countries. Some of these factors have
                        already been highlighted above. The principal factors which cause these concerns are:

                        •   there is no time factor involved  in the calculations; also
                        •   there is a high level of carbon converted to methane because there are no
                             considerations of methane oxidation.
                        In addition, die assumption that a constant fraction (0.77) of the DOC is dissimilated,
                        under any ambient conditions, is open to discussion. Ranges of values for dissimilated
                        DOC may therefore be more appropriate where local information is available.

                        Two further factors should be incorporated into the methodology of Bingemer and
                        Crutzen (1987) to account for concerns relating to time factors and to methane oxidation.
                         Both of these factors and suggested modifications to account for them are now discussed
                        further. They may be incorporated into the Workbook calculations in future versions.
                        Accounting for delayed release of methane: There is a lag time between placement
                         of the waste and the beginning of methanogenesis, after which generation increases until it
                         reaches a plateau. In the later stages  of methanogenesis, gas production trails off and
                         eventually ceases. The actual timing of the various stages of methane generation depend
                         on the type of waste and the conditions prevalent in the landfill.

                         If waste of roughly the same composition were deposited  at the same frequency for the
                         number of years that it takes for the majority of carbon in that waste to decay, the
                         assumptions of instantaneous release would  not lead to an overestimation of emissions -
                         current emissions from all the waste deposited during those years should equal the
                         eventual emissions from the waste deposited in the current year, as calculated by
                         Bingemer and  Crutzen's equation. If however the rate of disposal has increased over time,
                         the uncorrected Bingemer and Crutzen method will overstate the current year's
                          emissions. (US EPA,  1991 a)
                          In most cases, the amount of waste disposed of to landfills is increasing, it should be
                          possible to develop correction factors based on the average annual growth  rate of landfill
                          waste disposal, and the average amount of time the waste produces methane. Some initial
                          research in this area has been done  recently. (ICF,  1993)  Results of this work and other
                          related research will be reviewed and considered for possible updating of the
                          methodology  in the future.
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             Accounting for oxidation: Methane migrating through aerobic soil or waste can be
             oxidised by microorganisms, whilst sulphate-reducing bacteria may oxidise methane in
             anaerobic soil or waste. However, very little is known about the extent of methane
             oxidation that takes place within landfills, or of the factors which influence methane
             oxidation (Bogner and Spokas, 1993), and there is no widely accepted estimate for the
             rate at which methane is oxidised after it has been generated within landfills. Factors
             affecting methane oxidation are known to be' related to the microbiological conditions
             within the site, as well as the depth of the si|e, its permeability, etc. In addition, site
             management is likely to be important, including the characteristics of the site cap and any
             venting or control measures that are installed.
             More sophisticated models of methane emissions include a factor related to methane
             oxidation. However, the factors chosen  differ widely: Orlich (1990) chooses 40 - 50%; UK
             Department of the Environment (1993)  uses range between 0 - 40%; van Amstel et al
             (1993) assume 20%; US EPA (1993) use a factor of 10%. A better understanding of
             methane oxidation is needed to provide a more reliable factor for inclusion in future
             models.
             Based on these models, it is suggested that the estimate of methane emissions from
             landfills derived using the Bingemer and  Crutzen methodology be reduced by 10% to
             account for oxidation. Some consideration of the variation associated with this value may
             also be appropriate.
             Thus by incorporating these two modifying factors, the underlying Bingemer and Crutzen
             approach can be adjusted to reflect more accurately landfill conditions and country-specific
             data. It has the added advantage that the Bingemer and Crutzen approach is very simple
             and easy to use, and with these additional modifications, it can provide the best model for
             estimating emissions in many countries.

             Other approaches used
             For countries where more comprehensive data are available, different and more
             sophisticated methods may be applied to arrive at estimates of methane emissions from
             landfills. There have been various refinements made to Bingemer and Crutzen's approach;
             these are described in the next section.
             Ahuja (1990) used the same approach as Bingemer and Crutzen (1987), but included a
             further factor in the equation, namely the percentage of MSW that is dry refuse. Methane
             emissions were calculated according to  Equation 6.2.
                                               EQUATION 6.2
                    Total MSW generated (Gg/yr) x Fraction MSW landfilled x Fraction DOC in
                    MSW x Fraction Dry refuse x Fraction Dissimilatecl DOC x 0.5 g C as CH4/g
                         C as biogas x Conversion factor (16/12) - Recovered CH4 (Gg/yr)


                                               Methane emission
              Again however, this approach requires application of regional factors which are subject to
              much uncertainty, also the value for the Fraction Dry refuse can be open to much dispute
              even within a single country, let alone worldwide.
              Another empirical approach'was taken by Orlich (1990), who applied factors for waste
              generation rates per capita and for methane generation rates per tonne of waste for both
              developed and developing countries. These two factors were 1.0 kg or 0.5 kg per capita
              per day, and 180 m3 or 60 m3 methane per tonne for developed and  developing countries
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                        respectively. Orlich ((990) also excluded any waste disposal outside of urban areas in
                        developing countries. This method of calculation gave a global estimate of 32.9 M tonnes
                        of methane emissions from landfills in developed and developing countries in 1990. UN
                        population statistics were also used to  estimate future emissions up to 2030.

                        Richards (1989) used gross domestic product (GDP) as an indicator of waste generation
                        rates, which in turn were used to estimate methane emissions from landfills as an energy
                        resource. Using figures of world GDP,  he estimated a world waste generation value of 490
                        million tonnes per annum, of which about 80% would be landfilled, yielding about 100 m3
                        of landfill gas per tonne of refuse over about 10 years. This analysis yielded a value of
                        global methane emissions from landfills of 9.8-18.3 Mt/yr.
                        Theoretical first  order  kinetics  methodologies

                        More complex methods for estimating methane emissions from landfills acknowledge the
                        fact that methane is emitted over a long period of time rather than instantaneously as in
                        the former methodologies. A kinetic approach therefore needs to take into account the
                        various factors which influence the rate and extent of methane generation and release
                        from landfills. This approach has generally been used to calculate emissions from individual
                        landfills, for example in the estimation of the potential of a site to generate economic
                        quantities of landfill gas,:but it can also be applied in a more general way to entire regions
                        or countries.
                        Early attempts  to calculate emissions using a kinetic approach were discussed by EMCON
                        Associates (1981), the most well known and used of which is referred to as the Scholl
                        Canyon Model. This  approach modelled the "average" landfill within the region or country,
                        and then scaled the results to take into account the total waste landfilled within the whole
                        region or country.
                        A number of factors need to be taken into  account in any kinetic modelling of landfill
                        methane generation. The main factors to consider are those of waste generation  and
                        composition, environmental variables such as moisture content, pH, temperature and
                        available nutrients, as well as information on the age,  type and time since closure  of the
                        landfill (Thorneloe and Peer, 1990).
                        The model equation  and variables included  in the Scholl Canyon model are given as
                        follows:
                                                  Q CH4 s LO R (expfkc) - exp(-kt)}
                        where:

                        QCH«

                        LS
                        R

                        k

                        c

                        t
methane generation rate at year t (rrrVyr)

DOC available for methane generation (nrrVt of refuse)

quantity of waste landfilled (t)

methane generation rate constant (yr'1)

time since landfill closure (yr)

time since initial refuse placement (yr)
                        Practical applications of kinetic models

                        A number of countries have applied this or similar modelling approaches to their own
                        situation;
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                A recent study in the United Kingdom (Department of the Environment,  1993) has used
                the same modelling rationale but with two different approaches to the problem of scaling
                the modelling to include all wastes within the UK:

                (i)   UK landfilled waste was treated as if it were disposed of to a single site. Model
                    parameters were selected to represent nationally weighted average values, and an
                    estimate of methane production from a unit of waste was made. The results were
                    then extrapolated to arisings for the whole of the UK..

                (ii)  Data were collated for sites where information was available, the yield of methane
                    was calculated for these sites, and the results were then extrapolated to waste
                    arisings for the whole of the UK. Average parameteb values were used as above. It
                    was necessary to assume that the sites covered contained waste types in proportions
                    representative of all UK sites to ensure that the  extrapolation was valid.

               This study drew on  extensive data available on the typical composition of waste arisings
               from different sources (domestic, civic amenity,  commercial, industrial and inert), and used
               this information to divide the degradable carbon pool into three categories, each with a
               different decomposition rate constant, representing material that decomposes at different
               rates. This is a similar approach to that taken by Pacey and Augenstein (1990) and Manley
               etal (1990). Further modifications to the model predictions included a one year time lag
               before the start of methane generation, as well  as modifications for aerobic
               decomposition,  microbial biomass, leachate generation and methane oxidation. Each of the
               factors was included in the model as a percentage decrease in methane emissions.
               The results from this study provided estimates of the range of methane production per
               tonne of waste over all time. These were then either compiled with waste  arisings
               statistics, or were incorporated into sites with known data and then extrapolated to
               national levels, to provide estimates of methane  production from MSW in the UK. The
               results  showed a wide range of values for the amount of methane produced from MSW,
               between 0.6 and 5.3 Mt per year,  as well as a best estimate of about 2 Mt per year. These
               figures  have already taken reductions from gas flaring or use into account. The study
               emphasised that the uncertainty associated with  the estimate  reflected the  lack of
               confidence in the modelling parameters.

               The Netherlands have carried out a national estimate of methane emissions using a first
               order kinetic model  applied to the whole country (Van Amstel et al.,  1993). The estimate
               used detailed information on landfilling that has been collected for the country since 1945,
               a degradation rate coefficient of 0.1 per year (based on measurements of actual methane
               emissions at three landfills), and a  degradable organic fraction  of 18% before 1986, and
               17% between  1986 and 1995. After 1995 this fraction is predicted to decrease because of
               recycling and separation initiatives that are aimed at reducing the organic content of waste
               to landfills. The calculation also assumed an oxidation percentage in the soil cover of 20%
               and a methane concentration of 50% of the landfill gas. This approach has provided an
               estimate of methane emissions from landfills in the Netherlands of 377 kt methane per
               year (range  178-576), with 25% recovery.

               In Canada, emissions from landfills have also been calculated using the Scholl Canyon
               model (Environment Canada, 1992). The approach used population statistics and waste
               generation rates per capita, as well as collecting as much information as possible on major
               landfills  such as the date opened and closed, waste quantities landfilled, and gas collected.
               The default value for methane generation used was 232 mVt, whilst the rate constant k
               was determined for specific  landfill sites. Using these factors, a value of 1405 kt methane
               was obtained for methane emissions from Canadian landfills in 1990 (excluding any
               methane reductions from flaring or use). Environment Canada (1992) estimate that this
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                        value is about 22% lower than one derived using the Bingemer and Crutzen (1987)
                        methodology.
                        In the United States, emission from landfills have been calculated using an adaptation of
                        the Scholl Canyon model (US EPA, 1991 b) by EPA's Office of Air Quality Planning and
                        Standards of the Office of Air and Radiation. Data was collected from a stratified sample of
                        630 US  landfills (US EPA,  1988) indicating that 334 teragrams per year of waste are
                        tandfilled annually. This data was used to develop inputs for the first-order decomposition
                        model and estimates were generated to consider potential regulations for MSW landfill atr
                        emissions. The baseline estimate for the U.S. for active municipal solid waste landfills is 18
                        teragrams in 2000 and 20 teragrams in 2010. This estimate does not include methane
                        emissions from industrial landfills. Extensive modelling of potential emissions for different
                        regulatory strategies has been conducted. This has been published in a background
                        information document. (U.S. EPA, 1991 a)


                         Other methodologies used
                         In the United States, EPA's Air and Energy Engineering Research Laboratory (AEERL) of
                         die Office of Research and Development has taken a different approach to calculating
                         methane emissions from US landfills. (EPA,  1991 b; EPA, 1992; EPA, I993b) Due to the
                         concern with the inaccuracy of predicting degradable organic content and the occurrence
                         of over-prediction of gas quantities using first-order decomposition rate equations, AEERL
                         gathered data from  112 landfills including landfill gas recovery rates and welled waste (i.e.,
                         quantity of waste from which landfill gas is extracted through the recovery wells). The data
                         went through extensive quality assurance including site visits to over 30 facilities and
                         scrutiny by industry and academia exports.
                         An empirical model was developed relating flow rates to welled waste through statistical
                         and regression analyses. (EPA,  I99(band 1992; Thorneloe,  1992.)  The objective was to
                         Set statistical criteria dictate the shape and position of the regression  curve. A regression
                         model with three different linear segments was the result where each segment applies to a
                         distinct landfill size class. The emission factors that were developed from this approach are
                         believed to represent the actual gas recovery rates as opposed to model  predictions based
                         on assumed values for degradable organic content. The results of this research are being
                          published in two EPA reports.
                          .    Estimate of Global Methane Emissions from Landfills and Open  Dumps, to be
                               published 1/94.
                          •    Estimate of Methane Emissions from U.S. Landfills, to be published 119.4.
                          The findings from this modelling approach indicate that U.S. methane: emissions account
                          for 11  to 23 tg/yr (with an average of 17) and that global emissions account for 27 to 58
                          ts/yr (with an average of 43) in 1992. The amount of methane being utilised or flared was
                          excluded from this estimate. Using Bingemer and Crutzen's (1987) approach and similar
                          inputs for these different approaches, an average for U.S. emission was 25 tg/yr and the
                          average for global emissions was 61. This suggests that Bingemer and Crutzen's approach
                           results in an  estimate approximately 30% greater than the estimates obtained by AEERL.
                           (Thorneloe,  1993a)
                           The Global Change Division (GCD) of the Office of Air and Radiation has adopted a
                           similar statistical modelling approach. Data were collected from 85 landfills that were
                           considered to be representative of those US landfills that contain the majority of the
                           waste in place in the US. A statistical model was then developed from the verified database
                           that established the relationship between the quantity of waste in place and the methane
    6.14

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               production from the landfill. Their estimate for the US suggests that landfills contribute 8.1
               to 12 tg/yr for 1990, with a central estimate of 9.9 tg/yr. The major reason for the
               difference between the AEERL and GCD model results is believed to be the difference in
               the waste quantity used. It is recognised that there is uncertainty with estimates available
               for the quantity of waste being landfilled. In fact, this is considered one of the largest
               uncertainties with estimating methane emissions from landfills.

               A regression approach such as those used by AEERL and GCD may be appropriate to use
               in other countries outside of the US. However, regression coefficients may vary
               considerably between different countries because of the many factors that differ between
               landfills in the US and in other countries. In particular, the landfills included in the US
               analyses were generally some of the largest landfills in the world. Few other countries have
               as many landfills as large as this. Other factors which will influence the value of the
               regression  coefficient include the waste composition, site management techniques, and the
               climate. Other countries are conducting studies to see if similar results are found. The
               United Kingdom's Department of the Environment is obtaining gas extraction data from
               landfills and will explore a similar modelling approach.
     6. I .5 Sources  of  uncertainty

               Several sources of uncertainty in estimating emissions of CH4 from landfills exist, these
               include:

               •    The quantity of CH4 that is actually produced from the waste in the landfill;

               •    The quantity and composition of landfilled waste;

               •    The quantity of CH4 that is actually emitted to the atmosphere.


               Emissions  of methane from open  dumps and
               from older small  sites

               Most methods of estimating methane-emissions from landfills exclude both these
               categories, on the grounds that emissions from these sources are very insignificant.
               However, as discussed above, there is anecdotal evidence to indicate that "open" landfills
               may generate significant quantities of methane, even though they are not managed
               according to high standards of landfilling techniques. The waste contains high levels of
               readily degradable organic material, and therefore degrades very rapidly and completely
               over a period of up to 10 years. National experts may use their own discretion as to
               whether or not to include these estimates. Obviously this increases the overall range of
               uncertainty in national estimates.

               For old or small landfill sites,  US EPA's (I993b) calculations have excluded any
               consideration of these sites contributing to methane emissions.  However, there are
               thought to be about 30,000 older closed landfills in the US (Thorneloe,  1992), and field
               measurements of urban methane concentrations indicate that older closed landfills are
               often significant sources of emissions in the urban environment  (Kolb et al. 1992).
               Omission of older closed landfills from this analysis therefore biases the estimates of
               methane emissions downwards, contributing to the overall uncertainty in the estimate.
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                        Waste quantities and  composition

                        The most significant factor that determines the accuracy of estimates of methane
                        production from landfills is an accurate knowledge of the quantity and composition of
                        wastes disposed of to landfill. This includes the quantity of waste already in place, plus data
                        relating to annual waste disposal to landfills.
                        Many developed countries now have effective means for statistical collection of the
                        quantity of waste being disposed of to landfills, and are also improving their understanding
                        of die composition of various waste categories.
                         Historical  knowledge of waste disposal is often less accurate: waste statistics for the UK,
                         for example, are of very limited quality before 1974 - prior to that date, responsibility for
                         waste disposal was at a local level, and was not nationally co-ordinated (Department of the
                         Environment, 1993).
                         Similarly, many countries have poor records on numbers of landfills, especially of older
                         closed sites. US EPA (I993b) estimates that in the US, approximately 3,000 small landfills
                         closed during the 1980s, additionally that there may be tens of thousands of landfills that
                         closed prior to this. In many countries, the existence of older closed sites may be  known
                         but no records of waste types or quantities are available.

                         For most countries, limitations on funds available will prevent extensive investigations of
                         these older closed sites, except for those that are still causing local environmental
                         concern. It is therefore more cost-effective to concentrate efforts into improving the
                         quality of data being collected on existing landfilling operations, including on the total
                         waste to landfill plus more detailed site-specific landfill data. Detailed site investigations, for
                         example in connection with a gas exploitation scheme, may give additional support to
                         emissions predictions, or can be used to support predictive methodologies as with the US
                         EPA's (1993) method.
                         Composition of waste is very important in determining the amount of methane generated.
                         The degradable organic content (DOC) of waste is an essential component in all
                         calculations of methane emissions, and small variations in the assumed values for DOC can
                          result in large variations in the overall estimate of methane emissions. As further
                          information becomes available about the composition of a country's waste, so it can be
                          categorised into fractions with varying decomposition half lives, for incorporation into
                          kinetic models.
                          Different countries have widely differing MSW compositions: developing countries have
                          solid waste that is of a higher putrescible fraction compared with developed countries,
                          where waste has a much higher paper and card content. These factors influence both the
                          rate and  the extent of degradation of the various waste fractions, and need to be taken
                          into account where data are available. Future changes in waste management practices will
                          change the composition of waste to landfill considerably, resulting in different methane
                          emissions levels.
                          The amount of municipal waste landfilled in the U.S. is estimated at approximately 334 Tg
                           (U.S. EPA, Office of Solid Waste [OSW], 1988). This figure represents one of the largest
                           uncertainties in the current estimates. Paper was the largest single component of the
                           degradable organic carbon (DOC) fraction in both the U.S.and Canada.Per capita  MSW
                           generation was in the range of 1.7 to 1.8 kg/person/day for both the U.S. and Canada (U.S.
                           EPA, 1990; El Rayes and Edwards, 1991). The average MSW generation rate in other
                           OECD countries is 1.1 kg/person/day. MSW in these countries has a DOC content of
                           approximately 15.3% (Davis et al.,  1992). The value used for the U.S. is for MSW only; an
                           additional 15 Tg/yr of biodegradable industrial solid waste is also landfilled, (U.S.  EPA,
   6.16

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                                                                                                           WASTE
               1987). This industrial solid waste is unaccounted for in the initial estimates of landfill
              methane.

              In most cases, country-specific information does not state specifically whether industrial
              waste is co-disposed with MSW.

              Information on the amount of MSW generated and landfilled in the European countries
              that are not OECD members and the former Soviet Union is limited. Average MSW
              generation for Greece, the former Soviet Union, and Eastern Europe is approximately 0.6
              kg/person/day (Frantzis, 1988; Papachristou, 1988; Peterson and Perlmutter, 1989 and
              Bingemer and Crutzen, 1987), and the available data indicate that putrescibles make up a
              large portion of the MSW (estimates range from 32 to 60%). This MSW contains
              approximately 15% DOC  (Frantzis, 1988; Papachristou, 1988; Peterson and Perlmutter,
               1989; Bingemer and Crutzen, 1987; Zsuzsa, 1990).

              For most Asian countries, estimates of MSW generation were identified for one or two
              major cities, but not for the  entire country. National per capita MSW generation estimates
              were identified for Indonesia, Sri Lanka, the Philippines, Singapore, Taiwan, and Pakistan.
              These estimates range from  0.4 kg/person/day for the Philippines to  1.0 kg/person/day for
              Singapore. The average per capita MSW generation for these countries is estimated to be
              0.6 kg/person/day (Davis et al., 1992).                 t,
                                                                 If
              Few data are available on MSW production and management in Central America, South
              America, the Caribbean Islands, and  Mexico. Most of the available information is only for
              the larger cities. The average per capita MSW generation rate in Costa Rica, and Mexico
              and six South American countries (Brazil, Colombia, Chile, Paraguay, Peru, and Venezuela)
              is estimated to be 0.8 kg/person/day. The components are mainly vegetable and
              putrescible waste paper and  cardboard. The average DOC for the mentioned countries is
               !7%(Davisetal.,  1992).

              Information on MSW generation and disposal for African and Middle Eastern countries is
              very limited. In Africa, it-appears that toxic and hazardous industrial and commercial
              wastes are purposely or inadvertently disposed of with the MSW stream. Some
              information pertaining to generation rates for African countries was  located; but
              information for only two Middle Eastern countries, Israel and Yemen, was obtained. Based
              on the very limited information for these two continents, it: is estimated that per capita
              generation rates range from  0.3 to I. I kg/person/day, and the DOC content ranges from 3
              to 20%.  (Thorneloe, I993a)

              Landfill and waste management practices also have significant effects on methane
              generation, for example the degree and type of landfill cover, the method of landfilling, the
              water management practices etc.
              Flaring  and  gas recovery  schemes

              Both of these factors will reduce the amount of uncontrolled methane emissions from
              landfills. Utilisation and/or flaring of landfill gas as an energy source is one of the most
              successful methods for reducing uncontrolled methane emissions from landfills (see
              "Options for controlling methane emissions from landfill sites" for further details).

              Gas flaring generally occurs where it is necessary to ensure local site safety, but it is now
              recognized as a valuable method for reducing the extent of methane emissions to
              atmosphere.

              Any national inventory of methane emissions from  landfills therefore needs to take into
              account the reductions achieved by these two factors. For gas use, numbers of schemes
PART 2
                                                                                                                 6.17

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                       are generally well known and documented, therefore an accurate estimate can be made of
                       the amount of methane being used in the schemes. Information on landfill gas schemes
                       around the world is available from a variety of sources, eg. Governmental Advisory
                       Associates (1991) for the US; Landfill Gas TRENDS (1993) for the UK; Gendebien et al.
                       (1992) for the European Community; Lawson (1991) for countries participating in the
                       International Energy Agency's Bioenergy Agreement;  Richards (1989) for world statistics,
                       etc. Most of these sources update their information regularly as more schemes are
                       commissioned.
                       Estimates of the extent of flaring are more difficult to achieve with accuracy, and generally
                       have to be estimated from a knowledge of the state of landfill management within  the
                       country. For many countries, new legislation will ensure that most future landfills will be
                       obliged to have gas control equipment installed; therefore in the future this will result in
                        reductions in uncontrolled emissions as well as better quality data on this factor.
               6.l.6Availability  and  quality of data


                        Waste  management data

                        The quality of methane emissions estimates are directly related to the quality of the waste
                        management data used to derive these estimates, i.e. data on MSW generation rates, and
                        on quantities of MSW disposed of to landfill. Most developed countries have these data
                        available, and they should be used wherever possible. These data are often lacking
                        however for developing countries and for the former Communist bloc countries.

                        Some global compilations of data have been made that can be used where local data are
                        not available:
                        •    Thorneloe et al. (In Press) has compiled data on waste management activities;

                        •    World Resources Institute (1990) summarised waste generation rates for some
                             countries, including Eastern European countries;

                        •    Piccot et al, (1990) collected waste generation data;

                        •    Bingemer and Crutzen (1987) compiled regional data;

                        •    Carra and Cossu (1990) compiled data from 15 countries;

                        •    OECD (1989) compiled country-specific data;
                        •    U.S. EPA (forthcoming) compiled data on global waste management activities;

                        •    U.S. EPA (forthcoming 4/94) compiled  data on waste management activities;

                        •    U.S. EPA in the forthcoming Report to Congress on Global Anthropogenic Emissions
                             of Methane have compiled a list of over 50 references on global waste generation
                             data.
                         Historical data on the amount of MSW disposed of to landfill are usually of limited value or
                        quality. Extrapolation to future waste management scenarios is  usually easier, especially
                         since many countries are modifying their waste management policies, in particular to
                         promote waste reduction and recycling, and so are required to review and monitor total
                         MSW generation rates and disposal routes to provide current and future waste disposal
                         scenarios (eg. Van Amstel et al. (1993) for the Netherlands, US EPA (1993) for the US).
  6.18

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             Waste  composition  data

             The composition of waste directly determines its DOC value. Default factors provided by
             Bingemer and Crutzen (1987) should be used where no country-specific factors are
             known.

             As with 6.1 above, many countries are improving the quality of data held on waste
             composition, because of changes to waste management policies that are encouraging
             reduction and recycling.
             Gas  flaring and  use

             Accurate statistics are available in most of the countries where landfill gas use is practiced.
             However, the extent of gas flaring is often less well documented. Improvements to waste
             management practices should see an improvement in the collection of regular statistics
             which monitor the numbers of sites where gas is flared or used.
    6.1.7 Conclusion

             A methodology is presented here that allows simple calculation of methane emissions
             from landfills globally, and can be used by all countries. Some of the assumptions used in
             the method are open to criticism however, therefore countries are encouraged to
             progress to using a more sophisticated method with more country-specific data when
             more data become available.
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TABLE 6,1
REGIONAL WASTE DISPOSAL, COMPOSITION, AND WASTE GENERATION DATA
Region
USJCanada/AustraKa
US.
Canada
Australia
Other OECD
Japan
New Zealand
Austria
Belgium
Denmark
Finland
France
Germany
Greece
Ireland
Italy
Luxembourg
Netherlands
Norway
Portugal
Spain
Sweden
Switzerland
UK
USSR/E.Europe
Developing Countries
% MSW Landfilled
91
62
93
98
71
28
95
57
50
63
87
47
69
100
100
35
27
55
78
24
76
42
18
NA
85
80
% DOC of MSW
22
NA
NA
NA
19
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
17.5
15
Waste Generation
(kg/cap/day)
1.8
2.0
1.7
1.9
0.8
0.9
1.8
0.6
0.9
1.2
I.I
0.7
0.9
0.7
0.9
0.7
1.0
1.2
1.3
0.6
0.8
0.9
1.0
1.0
0.6
0.5
Sources: Bingemer and Crutzen (1987) for regional data and OECD (1989) for individual countries.
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             6.2    METHANE EMISSIONS  FROM
                      WASTEWATER TREATMENT
    6.2.1 introduction

             Methane (CH4) production from wastewater treatment (WWT) under anaerobic
             conditions is estimated to range from 30 to 40 teragrams, per year (Tg/yr). This represents
             8 to 11 percent of the total global anthropogenic methane emissions, estimated at 360
             Tg/yr (IPCC, 1992). Industrial WWT sources are estimated to be the major contributor
             to WWT emissions, accounting for 26 to 40 Tg/yr. Municipal WWT is estimated to emit
             approximately 2 Tg/yr, with Asia accounting for 65 percent. Uncertainty in these estimates
             result from a lack of data characterizing wastewater management practices, the quantities
             of wastewater that are anaerobically treated, data on the extent that CH4 produced is
             flared or otherwise utilized, and field data on the CH4 potential of wastewater treatment
             lagoons. (Thorneloe,  1993b)

             Wastewater can produce methane if it is treated anaerobically and if the methane
             produced is released to  the atmosphere. Anaerobic methods are used to treat wastewater
             from municipal sewage and from food processing and other industrial facilities, particularly
             in developing countries.  In contrast, developed countries typically use aerobic processes
             for municipal wastewater treatment or anaerobic processes in enclosed systems where
             methane is recovered and utilized.

             This section provides an explanation of the default methodology for estimating CH4
             emissions from WWT. A discussion of the uncertainty involved with these calculations is
             included.
    6.2.2 Background

             Highly organic waste streams including municipal wastewater and wastewater from
             industries such as food processing and pulp and paper plants have a high potential for CH4
             emissions. These waste streams quickly deplete available oxygen as their organic matter
             decomposes. The organic content or "loading" of wastewater is expressed in terms of
             biochemical oxygen demand (BOD), which is the principal factor determining methane
             generation potential of wastewater. BOD represents the amount of oxygen consumed by
             the organic material in the wastewater during decomposition (expressed in milligrams per
             liter - mg/l). A standardized measurement of BOD is the "5-day test" denoted as BODS.
             The maximum, or ultimate BOD is denoted as BODU. Untreated municipal waste streams
             typically have a BOD5 ranging from 110 to 400 mg/l. Food processing facilities, such as
             fruit, sugar and meat processing plants, creameries, and breweries can produce untreated
             wastewater with a BOD5 as high as 10.000 to 100.000 mg/l. (Thorneloe, I993b) Most
             other industrial wastewater has a low BOD content.
             Under the same conditions, wastewater with higher BOD concentrations will yield more
             CH4 than wastewater with relatively lower BOD concentrations. Because of its influence
             in CH4, BOD is a commonly measured parameter and data is available on BOD loading
             rates. Table 6.2 shows BOD values for municipal wastewater by region, while Table 6.5
             includes BOD values for the wastewater of key industries.

             Five-day BOD can range from 0.023 - 0.091 kg/capita/day for municipal wastewater. Per
             capita municipal wastewater BODS has been reported from 0.023 - 0.045 kg/day in
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                       developing countries and from 0.024 - 0.059 kg/day in developed countries; (the lower
                       value was reported for rural France) (Mara,  1976). The BOb increases when substantial
                       amounts of kitchen wastes are discharged to sewers, for instance as the result of using
                       sink disposals. (Thorneloe, I993b)
                       Treatment of wastewater and its residual solids byproduct (sludge) under anaerobic
                       conditions results in CH4 emissions. Wastewater treatment in developed countries
                       typically occurs aerobically using aerated impoundments. Digesters are also often used and
                       the gas is either flared or utilized. Wastewater in these countries is not expected to be a
                       major source of CH4. However, facultative and anaerobic  lagoons are often used for
                       storage and treatment. EPA estimated to 1987 that there are approximately 5.500
                       municipal waste stabilization lagoons in the United States which treat 5.2 x 10  m /day of
                       wastewater from 8 percent of die population served by municipal treatment systems
                       (Office of Municipal Pollution Control, 1987). The CH4 potential from these lagoons is not
                       well understood and little field data are available. Industrial and commercial wastewater
                       processes also use lagoons for treatment and storage.
                       Methane production varies depending upon  temperature,  retention time, BOD loading,
                       and lagoon maintenance. Facultative lagoons, the most common type, treat wastewater by
                       both anaerobic fermentation and aerobic processes. At the bottom of the lagoon, where
                       an anaerobic environment exists, organic matter is digested  to CH4 and CO2. As these
                       gases bubble to the  surface, much of the CO2 is adsorbed by algae and is used, along with
                       nutrients liberated during digestion, to produce algal biornass (University of California,
                       1984). Aerobic conditions, supported by algae growth, are maintained near the surface.
                       Between 20 and 30  percent of the BOD loading to a facultative pond is anaerobicaliy
                       metabolized. As BOD loading increases and natural surface aeration diminishes, facultative
                       lagoons proceed to a more anaerobic state. This results in higher CH4 production, provi-
                       ding that the temperature is higher than 15°C. Under these conditions, a facultative lagoon
                       may act more as an anaerobic pond, with possibly 95 percent of the lagoon volume
                       functioning anaerobicaliy. Fermentation and thus CH4 production, is negligible at
                       temperatures below about I5°C, at which point the lagoon  serves principally as a
                       sedimentation tank  (Gloyna,  1971).
                       The depth of the lagoon is also an important factor in CH4 production. Shallow lagoons,
                       one meter or less in depth, are not expected to produce  large quantities of CH4 because
                       the intake of oxygen from the surface, as well as the production of oxygen due to
                       photosynthesis, prevent the formation of a significant anaerobic zone. Facultative lagoons
                       are typically 1.2 to 2.5 meters in depth; lagoons greater than 2.5 meters in depth are
                       typically referred to as anaerobic lagoons. The last important factor influencing the
                       production of CH4 is the retention time. (Thorneloe, I993b)
              6.2.3 Methodology  for  Estimating  Emissions
                        from Wastewater  Treatment
                        Methane emissions from wastewater treatment should be calculated for two different
                        wastewater types:
                        I    Municipal wastewater
                        2    Industrial wastewater
                        For each category, a simple methodology for calculating methane emissions from
                        wastewater treatment is based on BOD loading and relies on available country-specific
                        data. In each category a more detailed approach is also discussed. The more detailed
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                                                                                                        WASTE
              approaches would produce more accurate results if input data are available. These data are
              not readily available now for many countries, but they may be in the future as research
              continues.
              Estimate  methane  emissions  from  municipal
              wastewater  treatment

              Steps for Method A (simplified approach)1

              Data needed are:

              I    Kg BODS per capita-day (default values are shown in Table 6.2 for different regions.)

              2    Country Population (developing countries may choose to estimate
                  wastewatertreatment emissions based only on the urban population of the country if
                  wastes produced in rural areas decompose in an aerobic environment - see Table
                  6.3 for list of anaerobic and aerobic treatment methods).

              3    Estimate fraction of total wastewater that is treated anaerobically. Wastewater
                  treatment methods that may result in anaerobic decomposition of waste are listed in
                  Table 6.3. Because published data on the fraction of wastewater that is anaerobically
                  treated in different countries are scarce, countries are encouraged to provide their
                  own estimate based on their available data. Table 6.4, however, contains default
                  values for the fraction of total wastewater that is treated anaerobically in certain
                  regions — these values may be used in the absence of country-specific  estimates.

              4    Subtract the amount of methane, if any, that is recovered and thus not emitted to the
                  atmosphere. This would include any methane recovered and either flared or used for
                  energy as part of wastewater treatment. If no national data are readily available, the
                  default assumption is that this amount is zero.

              Equation 6.3 summarizes the methane emissions calculation.
                                              EQUATION 6.3
                             [Population] x [kg BODs/capita-day] x [365 days/year] x
                            [0.22 kg CtVkg BOD5] x [Fraction Treated Anaerobically]
                                            - Methane Recovered


                                                kg CrVyear
             Steps for Method B (detailed approach)

             A more precise estimate of methane emissions from wastewater treatment for a given
             country is possible if the following additional data are available: I) The different treatment
             methods that are used in each country and the total portion of wastewater that is treated
             using each of these methods; and, 2) the methane conversion factor (MCF) for each of
             these treatment methods (the MCF represents the extent to which the maximum
             methane producing capacity of the wastewater is realized for a given wastewater
             treatment system).
                   1 This method is based on the approach developed for the Wastewater Treatment
                Chapter of EPA (forthcoming) and is described in Thonneloe (I993b).
PART 2
                                                                                                              6.23

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WASTE
                       Unfortunately, many countries are not likely to have data on the portion of wastewater
                       treated using different methods. This is likely to be the case for many developing
                       countries, which are of particular importance because of their reliance on anaerobic
                       treatment methods. Additionally, at this time, complete information on MCFs for different
                       wastewater treatment systems is not available.  Countries which have more detailed
                       Information on specific treatment methods and their MCFs are encouraged to use this
                       information in preparing national emissions estimates and to report these results to the
                       IPCC. Through review of such estimates and results of ongoing research, a more
                       comprehensive database of MCFs for specific treatment methods may be developed in the
                       future.
                       Where these data are available, the following approach would be used to estimate
                       methane emissions from wastewater treatment:

                       Data Needed are:
                       I    Country Population
                       2    Kg BOD5 per capita-day
                       3    Fraction  of total wastewater treated using different treatment methods. Some
                            common methods are listed in Table 6.3.
                       4    The MCF (methane conversion factor) of each wastewater treatment method.

                       Equation 6.4 summarizes the calculation of methane emissions from each wastewater
                       treatment system using the more detailed approach. Total emissions are die sum of
                       emissions from all systems.
                                                        EQUATION 6.4
                                      [Population] x [kg BODsfcapita-day] x [365 days/year] x
                                [0.22 kg CH^/kg BODS] x [Fraction Wastewater Treated using Method,]
                                         x Methane Conversion Factor (MCF) for Methodj
                                                     - Methane Recovered

                                                          kg QVyear
                        Estimate  methane  emissions from  industrial
                        wastewater  treatment
                        Methane emissions from wastewater produced in a few key industries are estimated to
                        account for a very large portion of total methane emissions from wastewater treatment.
                        (Thorneloe I993b) Table 6.5 lists industries which are believed to be responsible for
                        most of the emissions. National experts should estimate emissions for these industries,  if
                        applicable, and any others which can be estimated to have significant emissions, based on
                        locally available data.
  6.24

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                                                                                                            WASTE
               Steps for Method A (Simplified Approach)

                I    Determine the relevant industries for a given country. The methane emissions from
                    industrial wastewater treatment are based on wastewater outflow by industry. Table
                    6.5 lists industries which produce wastewater containing concentrations of organic
                    material likely to produce significant CH4 emissions.

               2    Wastewater outflow by industry must be estimated. If these data are not directly
                    available, they may be estimated based on production by industry, and waste
                    consumed per unit of product. Typical water consumption rates for some key
                    industries are  presented in Table 6.6.

               3    Then, the BOD content of the wastewater for each product must be estimated.
                    Default SOD values are provided in Table 6.5.

               4    Estimate the fraction of wastewater from each industry that is treated anaerobically.
                    Unfortunately, default values are not available by industry. If no information is locally
                    available, the default values shown in Table 6.4 could be  used as an initial
                    approximation.

               5    If anaerobic treatment with methane recovery is employed, the amount of methane
                    that is recovered should be subtracted from total emissions.

               Equation 6.5  summarizes the emissions calculation for industrial wastewater treatment
               Emissions should be estimated for each industry; total emissions from industrial
               wastewater treatment are the sum of emissions from each industry.
                                                EQUATION 6.5
                                      Wastewater outflow by industry (kl) x
                       [kg BODS/I] x [0.22 kg CHH/kg BODS] x  [Fraction Wastewater Treated
                                                 Anaerobically]
                                               - CH, Recovered


                                                 kg CH4/year
              Method B (detailed approach)

              As with estimating methane emissions from municipal wastewater treatment, more precise
              estimates of methane emissions from industrial wastewater treatment can be made if
              specific methods used to treat wastewater from each industry are known and the MCFs
              for each method have been estimated.

              If this information is available. Equation 6.6 can be used to calculate emissions from
              industrial wastewater treatment. Total emissions for each industry are the sum of
              emissions from each wastewater treatment system. Total emissions from industrial
              wastewater treatment are the sum of emissions from each industry.
PART 2
                                                                                                                6.25

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WASTE
                                                      EQUATION 6.6
                                            Wastewater outflow by industry (kl) x
                              [kg BODj/l] x [0.22 kg CH
-------
                                                                                                       WASTE
             Wastewater Treatment  Facility  Efficiency  and
             Output

             Wastewater supposedly treated aerobically by treatment plants may still be subject to
             anaerobic conditions, due to poorly functioning facilities. In addition, adjustments should
             be made for (I) the amount of CH4 that is controlled through utilization or flaring and (2)
             the amount of CH4 that is oxidized prior to atmospheric release. However, the specific
             data needed are often not available.

             Research in Japan has produced data on high levels of methane production resulting from a
             wastewater treatment process that includes aeration and is essentially operated under
             aerobic conditions. (Kyosai and Mizuochi, 1993) This is result represents an area that
             should be studied in more detail in the future.

             Current estimates from wastewater treatment lagoons are relatively uncertain due to the
             limited available data. The US EPA's Office of Research and Development's Global Climate
             Change Engineering Research Program is conducting field measurements of wastewater
             treatment lagoons, both anaerobic and facultative, to develop emission factors from these
             sources.
             Physical  and  Chemical  Data

             Data on physicochemical wastewater characteristics are limited, especially for country-
             specific wastewater volumes. For industrial wastewater emission estimates, the BOD
             values reported for the source categories are averages of BOD values given for several
             process wastewater streams. The estimate could be improved if data were obtained on
             the chemical characteristics and volumes of process wastewater streams and the fraction
             of these wastewater streams anaerobically degraded. Furthermore, the emission
             methodology does not account for factors, such as temperature, pH and retention time,
             that influence the rate and extent of anaerobic decomposition, and consequently, the
             potential for CH4 production.
    6.2.7 Conclusion

             The methodology presented in this section gives a simple calculation of methane emissions
             from wastewater globally, and can be used by all countries. Some of the assumptions used
             in the method are open to criticism. Therefore countries are encouraged to progress to
             using a more sophisticated method with more country-specific data, when more data
             become available.
TABLE 6.2
ESTIMATED BOD5 VALUES IN MUNICIPAL WASTEWATER BY
REGION (KG/CAPITA/DAY)
Region
Africa:
Asia, Middle East, Latin America:
N. America, Europe, Former USSR, Oceania:
BOD5 Value
0.037
0.04
0.05
Source: EPA (forthcoming)
PART 2
6.27

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                                                              TABLE 6.3
                                                 ANAEROBIC AND AEROBIC METHODS OF
                                                       WASTEWATER TREATMENT
                                         Treatment Method
                                         Aerobic (low MCF) methods:
                                         Developing Countries
                                         •    Open Pits/Latrines
                                         •    Aerobic (shallow) ponds
                                         •    Ocean Dumping
                                         •    River Dumping
                                         Developed Countries
                                         •        Sewer systems with aerobic treatment
                                          Anaerobic (high MCF) methods:
                                          Developing Countries
                                          •    Anaerobic (deep) ponds
                                          •    Sewer systems with aerobic treatment.
                                          Developed and Developing Countries
                                          •    Septic Tanks
                                          Anaerobic Methods with Methane Recovery
                                          Primarily Developed Countries
                                                               TABLE 6.4
                                           ESTIMATED TOTAL (URBAN) WASTEWATER FRACTION
                                                        ANAEROBICALLY TREATED
                                                  Country/Region
                                                                                Fraction Treated
                                       Africa
                                                                                     N/A
                                       Asia and Oceania
                                                                                     15%
                                       Latin America
                                                                                  7% to 10%
                                       North America and Europe
                                                                                     15%
                                       Latin America
                                                                                     10%
                                        Source: EPA (forthcoming)
                                        Note: For many developing countries, industrial wastewater is often
                                        discharged with domestic wastewater.
  6.28

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                                                                WASTE
TABLE 6.5
BIOCHEMICAL OXYGEN DEMAND (BOD) ESTIMATES FOR VARIOUS INDUSTRIAL
WASTEWATERS
Industry* "
->> *"*$> «. •*&
Iron and Steel
Non-ferrous
metals
Fertilizer
Food & Beverages
Fruits/vegetables
Cereals
Meats
Butter
Cheese
Cane Sugar
Beet Sugar
Wine
Beer
Other Beverages
Pulp and Paper
Petroleum Refining
(Petrochemical)
Textiles
Rubber
Miscellaneous11
BOD5*
0^0
0.00 lb
0.00 lb
0.00 lb
0.035
0.003
0.00 lc
0.02°
0.003C
0.003°
0.002b
0.0 lb
0.135°
0.085°
0.083°
0.004b
0.004°
0.00 lb
0.00 lb
0.002
References and Notes -^ <• ^ , ^
. f " >- i f- t
J, " i - * T" *,/«•.
No references for BOD were obtained. Used the value for BOD in textile
wastewaters, p.67, Carmichael and Strzepek (1987) since it was the lowest
value obtained for industrial sources.
No references for BOD were obtained. Used the value for BOD in textile
wastewaters, p.67, Carmichael and Strzepek (1987) since it was the lowest
value obtained for industrial sources.
No references for BOD were obtained. Used the value for BOD in textile
wastewaters, p.67, Carmichael and Strzepek (1987) since it was the lowest
value obtained for industrial sources.
This value is an average of the following categories of the fruit & beverage
Industry.
Barnes etal. (1984), p. 213
EPA(l974a), p. 39,40
EPA (1975), p. 58, 60; EPA (I974c), p. 39, 41
EPA (I974b), p. 59; Barnes et al. (1984). p. 316
EPA (I974b), p. 59; barnes et al. (1984), p. 316
Barnes etal. (1984), p. 20
Barnes et al. (1984), p. 12; EPA (I974d)
Barnes etal. (1984), p. 73
Barnes etal. (1984), p. 73
Barnes etal. (1984), p. 73
Carmichael and Strzepek (1987), p. 4? and Hall et al. (1988) as cited in
Torpy(l988), p. 20
Average of values reported in Carmichael and Strzepek ( 1 987), pp. 33, 36
Carmichael and Strzepek (1987), p. 67
No references for BOD were obtained. Used the value for BOD in textile
wastewaters, p.67, Carmichael and Strzepek (1987) since it was the lowest
value obtained for industrial sources.
No BOD values obtained. Used BOD reported for the pharmaceutical
Industry in Carmichael and Strzepek (1987), p. 85
' Industries presented here are taken from table 47, pp 116, 117 in Carmichael and Strzepek ( 1 987).
b Reported as BOD. This is assumed to be ultimate BOD.
° Reported as BODs.
d Industries in this group were undefined.
Source: Thorneloe, I993b.
PART 2
6.29

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WASTE
TABLE 6.6
WATER CONSUMPTION PER UNIT OF PRODUCT FOR PAPER AND FOOD PROCESSING
FACILITIES
Process
Canneries
- Green beans
- Peaches and pears
- Other fruits and vegetables
:ood and Beverage Industry
-Beer
- Wine
- Meat packing
- Dairy products
- Sugar
3ulp and Paper
-Pulp
- Paper
Textiles
- Bleaching
- Dyeing
Water Consumption
(liters/metric ton)
80,000
22,000
8,000-40,000
60,000
20,000 liters/ton live weight
16,00-20,000

344,000-966,000
200,000 liters
300,000-400,000 liters/ton cotton
40,000-80,000 liters/ton cotton
Sources:
aMetcalfandEddy(l972).
b EPA (forthcoming).
* These were reported as BOD and are assumed to be ultimate BOD, as opposed to 6005. These
values, however, should still be used as the default assumptions, as other data are not available.
These water consumption factors are approximate, and in some cases, the water used in the process
may not all become wastewater.
 6.30

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                                                                                                                    WASTE
                                                      TABLE 6.7
                                ESTIMATE OF GLOBAL AND COUNTRY-SPECIFIC METHANE
                                    EMISSIONS FROM THE TREATMENT OF DOMESTIC
                                                   WASTEWATER -
                                    	I990(TG/YR)	
                                              Country
                                                                  Emissions
                                Africa3
                                             Egypt
                                                                  0.02
                                             Kenya
                                                                  0.01
                                             Morocco
                                                                  0.01
                                             Nigeria
                                                                  0.04
                                             South Africa
                                                                  0.01
                                             Sudan
                                                                  0.01
                                             Tanzania
                                                                  0.01
                                             Uganda
                                                                  0.01
                                             Other Africa
                                                                  0.09
                                Total Africa
                                                                  0.21
                                Asia0
                                             China
                                                                  0.54
                                             Korea, N.
                                                                  0.01
                                             Vietnam
                                                                  0.03
                                             Other Asia
                                                                  0.92
                                Total Asia
                                                                  1.50
                                South America3
                                             Argentina
                                                                  0.01
                                              Brazil
                                                                  0.05
                                              Colombia
                                                                  0.01
                                              Mexico
                                                                  0.03
                                             Venezuela
                                                                  0.01
                                              Other So. America
                                                                  0.02
                                Total South America
                                                                  0.13
                                ^iorth America
                                              Canada
                                                                  0.02
                                              United States
                                                                  0.15
                                              Other No. America
                                                                  0.04
                                Total North America
                                                                  0.21
                                Europe
                                              France
                                                                  0.01
                                              German Democratic    0.01
                                              Republic
                                              Italy
                                                                  0.01
                                              United Kingdom
                                                                  0.01
                                Total Europe
                                                                  0.04
                                Former
                                USSRb
                                                                  O.I (I
                                Oceania0
                                              Australia
                                                                  0.01
                                Total Oceania
                                                                  0.01
                                World Total
                                                                  2.30
                                a. Ten percent of BODS is assumed to be anaerobically degraded.
                                b. Fifteen percent of BODS is assumed to be ariaerobically
                                degraded.
PART  2
6.31

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WASTE
TABLE 6.8
ESTIMATE OF GLOBAL METHANE EMISSIONS FROM INDUSTRIAL
WASTE WATER TREATMENT 1990
(TG/YR)

Industry


con & Steel
^on-Ferrous
Meals
^ertiliier
foodSt
Beverages
Pulp* Paper
Petroleum
Refming
Textile
Rubber
MisceJ-
laneous*
TOTAL
Developed Countries
Endu stria!
Waste-
water
Outflow*
(Millions
m'/vr)


168,000
26.400 '
H.300
7,700
33,300
54.700
34.600
6.800
9.50G
3S5.500
BODS
W)


0.001
0.001
0.001
0.035
0.004
0.004
0.001
0.001
0.002

Percent of
BOD,
Anaerobicallv
Degraded
10%
15%
Emissions
4
1
0
6
3
5
1
0
0
20
6
1
I
9
4
7
1
0
1
30
Developing Countries
Industrial
Waste-
water
Outflow*
(Millions
mV)


56.000
8.850
4.SOO
2.600
11.100
(8.200
11,450
2.300
3.200
1 18.200
BOD'S
W>


0.00 1
0.001
0.001
0.035
0.004
0.004
0.001
0.001
0.002

Percent of
BODs
Anaeroblcallx
Degraded
10%
15%
Emissions
I
0
0
2
1
2
0
0
0
6
2
0
0
3
2
2
1
0
0
10
Worldwide
Industrial
Wastewate
r Outflow*
(Millions
mVyr)


224.300
35,000
19.000
10.300
44.400
73.200
46.100
9.100
12.700
474.100
BOD's
(M)


o.ooi
0.001
0.00)
0.035
0,004
0.004
0.001
O.OOI
0.002


10%

15%
Emissions
5
1
0
8
4
6
1
0
1
26
7
1
I
12
6
10
2
0
1
40
a. This group was undefined in Carmichael & Strzepec ( 1987).
b, Carmichjel & Strzepec (1987).
c. Sources of BOD values are given In Table 6.5.
 6.32

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                                                                                                    WASTE
            6.3    EMISSIONS  FROM  WASTE
                       INCINERATION
   6.3.1 Introduction
            Waste incineration like other types of combustion, is a source of many GHGs. Very few
            data have been compiled on the global emissions from waste incineration. Preliminary
            indicators are that this source represents a small percentage of the total GHG output
            from the waste source category.
    6.3.2 Emissions

            Certainly waste incineration produces CO2, but it is difficult to identify the portion which
            should be considered net emissions. A large fraction of the carbon in waste combusted
            (e.g. paper, food waste) is derived from biomass raw materials which are replaced by
            regrowth on an annual basis. These emissions should not be considered net CO2 in the
            IPCC methodology. If the agricultural or forestry sources are not being sustainably
            managed, net CO2 emissions (equivalent to reductions in biomass stocks) should be
            accounted for in those source categories. On the other hand, some carbon in waste is in
            the form of plastics or other fossil fuel based products. Combustion of these materials,
            like fossil fuel combustion, releases net CO2 emissions.
            Other relevant gases released from combustion are net GHG emissions. Methane
            emissions from waste incineration are highly uncertain. An expert working group
            recognised waste incineration as a source of methane production, but was not able to give
            global estimates  or default emissions factors. Although this source is considered to be
            relatively small compared to the other CH4 sources in waste, it was recognised as an area
            for further research in the future. (Berdowski et al., 1993)
            Recent studies have also shown that N2O may be an important GHG produced from
            incineration. Table 6-8 provides data from studies of several incineration plants and the
            N2O produced from the waste incineration, (de Soete, 1993) Studies in Belgium (IPCC,
             1993), Japan (Tanaka et al., 1992) and Norway (Rosland, 1993) have estimated N2O
            production from their waste incineration processes. It has also been found that the
            emission level depends on the nature of the waste burned. Research in Japan has noted
            that while all types of incineration produce N2O, sludge incinerators produce the highest
            emissions rates.  (Tanaka et al., 1992)
            Traditional  air pollutants from combustion - NOX,  CO, NMVOC - are characterized in
            existing emissions inventory systems. The IPCC does not provide a new methodology for
            these gases, but recommends that national experts use existing published methods. Some
            key examples of the current literature providing methods are: CORINAIR Default
            Emissions Handbook (Bouscaren, 1992), as well as the U.S. EPA's Compilation of Air
             Pollutant Emissions Factors (AP-42) (US EPA,  1985) and Criteria Pollutant Emission
             Factors for the  1985 NAPAP Emissions Inventory (Stockton and Stelling, 1985).
PART 2
                                                                                                           6.33

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WASTE
TABLE 6.9
NITROUS OXIDE EMISSIONS FROM WASTE INCINERATION

Nature of Waste
reference)
(65) Municipal
refuse
(£6) Municipal
refuse

[67) Municipal solid
waste



[65) Sewage- sludge

(66) Sludge




Facility
10 furnaces
{65-300 tons/day)
Stepgrate
Stepgrate
Ftuid.bed
5 stokers
20-400 t/d
3 fluid.bed
rotktln
120 t/d
4 incin.
150-300 t/d
Rotary grate
Fiuid.bed
"
••
"
T°C

780-880
780-980
830-850






750
770-812
838-854
834-844
853-887
mm.
1.2
0.8
4
6.7
3
5.6
10.2


57


270
135
100
45
>pmv
aver-
age
8


7
9.8
II. 1


87

50.7




NjO emission
max
18
4.9
24
10.5
12
17.1
12.1


125


600
292
320
145
at
02(%)

10
8-14
13-15












gN70
ton waste

11-43
40-220
14-123
26*270
97-293
135-165




227
580-1528
684-1508
275-886
101-307
Source; deSoete, 1993.
 6.34

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                                                                                                          WASTE
               6.4    REFERENCES

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               Berdowski, J.J.M., LBeck, S. Piccot, J.G.J. Oliver, C. Veldt. 1993, Working Group Report:
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               Bhide, A.D., Gaikwad, S.A., and Alone, B.Z.  1990. CH4 from Land Disposal Sites in India.
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               Bingemer H.G. and Crutzen P.J.  (1987). The production of methane from solid wastes.
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               Bogner J and Spokas K. (1993). Landfill methane: rates, fates, and role in global carbon
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              Carmichael, J.B., and K.M. Strzepek. 1987. Industrial Water Use and Treatment Practices.
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                                                                     i
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PART 2
                                                                                                               6.35

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WASTE
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