United States
            Environmental Protection
            Agency
            Air and Radiation
            (6202 J)
EPA 430-R-93-006
July 1993
&EPA
Options for Reducing Methane
Emissions Internationally
Volume I: Technological Options
for Reducing Methane Emissions
            Report to Congress
                                 PROPERTY OF
                                  DIVISION
                                    OF
                                 MFTFQROLQj
                                   nor

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   Options for Reducing Methane
      Emissions Internationally
             Volume I:

Technological Options for Reducing
        Methane Emissions
        Report to Congress
         Editor: Kathleen B. Hogan
     U.S. Environmental Protection Agency
         Office of Air and Radiation
              July 1993

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                                Disclaimer

      This document has been reviewed in accordance with the U.S. Environmental
Protection Agency's and  the  Office of  Management  and  Budget's peer  and
administrative review policies and approved for publication. Mention of trade names
or commercial products does not constitute endorsement or recommendation.

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                             Table of Contents

VOLUME I

Foreword	  vii

Acknowledgements	   ix
EXECUTIVE SUMMARY  	   ES - 1
      ES.1  Introduction	   ES - 1
      ES.2  Volume I.  Assessments of Technological Options  	  ES - 2
      ES.3  References  	ES - 15

CHAPTER ONE
INTRODUCTION	  1-1
      1.1   Background: The Importance of Methane	  1-2
      1.2   Technological Options for Reducing Methane Emissions	  1-9
      1.3   Methane Reduction Options in Countries of Interest	  1-11
      1.4   Overview of Report  	   1-11
      1.5   References  	   1-13

CHAPTER Two
LANDFILLS	  2-1
      2.1   Background	  2-1
      2.2   Methane Recovery and Utilization  	  2-5
      2.3   Aerobic Landfill Management	   2-15
      2.4   Reduced Landfilling of Waste	   2-21
      2.5   References  	   2-29

CHAPTER THREE
OIL AND NATURAL GAS  	  3-1
      3.1   Background	  3-1
      3.2   Reduced Venting And Flaring During Production	  3-7
      3.3   Improved Compressor Operation  	   3-10
      3.4   Improved Leak Detection and  Pipeline Repair	   3-14
      3.5   Low Emission Technologies and Practices	   3-23
      3.6   References  	   3-29

CHAPTER FOUR
COAL MINING  	  4-1
      4.1   Background	  4-1
      4.2   Enhanced Gob Well Recovery  	  4-7
      4.3   Pre-Mining Degasification  	   4-19
      4.4   Ventilation Air Utilization	   4-26
      4.5   Integrated Recovery	   4-31
      4.6   References  	   4-35

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CHAPTER FIVE
FOSSIL FUEL COMBUSTION  	   5-1
      5.1   Background	   5-1
      5.2   Opportunities for Reducing Methane Emissions  	  5-3
            5.2.1  REDUCTION OF METHANE EMISSIONS FROM STATIONARY SOURCES .  .  5-3
            5.2.2  REDUCTION OF METHANE EMISSIONS FROM MOBILE SOURCES	  5-5
      5.3   References	   5-9

CHAPTER Six
RUMINANT LIVESTOCK	   6-1
      6.1   Background	   6-1
      6.2   Improved   Nutrition  Through   Mechanical  and  Chemical   Feed
            Processing	   6-10
            6.2.1  ALKALI/AMMONIA TREATMENT OF Low DIGESTIBILITY STRAWS ....   6-10
            6.2.2  CHOPPING OF Low DIGESTIBILITY STRAWS  	   6-12
            6.2.3  WRAPPING AND PRESERVING RICE STRAW	   6-14
      6.3   Improved Nutrition Through Strategic Supplementation	   6-14
            6.3.1  MOLASSES/UREA MULTINUTRIENT BLOCKS	   6-16
            6.3.2  MOLASSES/UREA MULTINUTRIENT BLOCKS WITH BYPASS PROTEIN . .   6-20
            6.3.3  DEFAUNATION  	  	   6-23
            6.3.4  TARGETED MINERAL/PROTEIN SUPPLEMENTS	   6-25
            6.3.5  BlOENGINEERING OF RUMEN  MICROBES	   6-27
      6.4   Production  Enhancing Agents  	   6-28
            6.4.1  BOVINE SOMATOTROPIN (eST)	   6-29
            6.4.2  ANABOLIC STEROIDS	   6-31
            6.4.3  OTHER AGENTS	   6-33
      6.5   Improved Genetic Characteristics	   6-33
            6.5.1  CROSSBREEDING IN DEVELOPING COUNTRIES	   6-34
            6.5.2  CONTINUED GENETIC  IMPROVEMENT IN DAIRY CATTLE   	   6-34
            6.5.3  TRANSGENIC MANIPULATION	   6-35
      6.6   Improved Reproduction	   6-35
            6.6.1  TWINNING	   6-36
            6.6.2  EMBRYO TRANSPLANTS	   6-36
            6.6.3  ARTIFICIAL INSEMINATION AND ESTRUS SYNCHRONIZATION  	   6-37
      6.7   Other Strategies	   6-37
      6.8   References  	   6-39

CHAPTER SEVEN
LIVESTOCK MANURE 	   7-1
      7.1   Background	   7-1
      7.2   Covered Lagoons	   7-6
      7.3   Small Scale Digesters	   7-11
      7.4   Larger  Scale Digesters  	   7-19
      7.5   References  	   7-28

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CHAPTER EIGHT
WASTEWATER MANAGEMENT	  8-1
      8.1   Background	  8-1
      8.2   Prevention of Methane Production During Wastewater Treatment  ...  8-6
      8.2.1  AEROBIC PRIMARY TREATMENT	  8-6
            8.2.2 AEROBIC SECONDARY WASTEWATER TREATMENT 	  8-10
            8.2.3 LAND TREATMENT	  8-14
      8.3   Recovery and Utilization/Flaring of Methane from Anaerobic Digestion
            of Wastewater and Sludge  	  8-16
            8.3.1 ANAEROBIC DIGESTION WITH METHANE UTILIZATION  	  8-16
            8.3.2 FLARING	  8-19
      8.4   Minimization of Methane Emissions During Treatment,  Utilization, and
            Disposal of Sludge  	  8-20
      8.5   References  	  8-25

CHAPTER NINE
BIOMASS BURNING 	  9-1
      9.1   Background	  9-1
      9.2   Opportunities for Reducing Methane Emissions  	  9-3
      9.3   References	  9-7

CHAPTER TEN
RICE CULTIVATION  	  10-1
      10.1  Background	  10-1
      10.2  International Research Plan 	  10-3
      10.3  References  	  10-6
                                       in

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                                   List of Exhibits
Exhibit #                                                                      Page

EXECUTIVE SUMMARY
Exhibit ES-1   Technological Options  for Reducing  Methane  Emissions  from Coal
             Mining, Oil and Natural Gas Systems, and Fossil Fuel Combustion .  .  ES - 4
Exhibit ES-2  Technological Options for Reducing Methane Emissions from Ruminant
             Livestock, Livestock Manure,  and Rice Cultivation	  ES - 5
Exhibit ES-3  Technological Options for Reducing Methane Reductions from Landfills,
             Wastewater, and Biomass Burning	  ES - 6
CHAPTER ONE
INTRODUCTION
Exhibit 1-1    Global Methane  Concentrations	  1-5
Exhibit 1-2    Global Contribution to Integrated Radiative Forcing by Gas for 1990  .  1-7
Exhibit 1-3    CO2 and Methane Reduction Comparison  	  1-8
Exhibit 1-4    Global Methane  Emissions from Major  Sources	  1-9

CHAPTER Two
LANDFILLS
Exhibit 2-1    Summary of the Technical Assessments for Landfills	  2-4
Exhibit 2-2    Landfill Gas Recovery Well 	  2-6
Exhibit 2-3    Co-generation with a Gas Turbine  	  2-10
Exhibit 2-4    Capital and Operations Costs  for Gas-to-Electricity Projects	  2-13
Exhibit 2-5    Semi-Aerobic  Landfill 	  2-16
Exhibit 2-6    Recirculatory Semi-Aerobic Landfill	  2-18
Exhibit 2-7    Aerobic Landfill  	  2-19

CHAPTER THREE
OIL AND NATURAL GAS
Exhibit 3-1    Natural Gas Systems 	  3-2
Exhibit 3-2    Summary of Options for  Reducing  Methane Emissions from Oil and
             Natural Gas Systems	  3-6
Exhibit 3-3    Joint Repair with Heat Shrink Sleeve	  3-17
Exhibit 3-4    Joint Repair with Urethane Resin Mold  	  3-18
Exhibit 3-5    Pipe Repair with Polyamide Elastomer Layer  	  3-19
Exhibit 3-6    Pipe Repair with Epoxy Resin	  3-19
Exhibit 3-7    In-Pipe Joint Sealing Equipment	  3-20
Exhibit 3-8    Pneumatic Device Bleed Rates	  3-23
Exhibit 3-9    Typical Fugitive  Emission  Rates, Component  Numbers, and  Facility
             Emissions  	  3-24
Exhibit 3-10  Volume of Gas in Various Size Lines at Different Pressures; Volume  of
             Gas Saved per Mile of Pipeline	  3-26

CHAPTER FOUR
COAL MINING
Exhibit 4-1    Coal  Rank and Methane Production  	  4-2
Exhibit 4-2    Coal  Mining and Methane  Recovery Techniques	  4-3
                                        IV

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Exhibit 4-3   Summary of  Options  for  Reducing Methane Emissions from  Coal
             Mining   	   4-6
Exhibit 4-4   Capital Costs for Gob Wells (per well costs)  	   4-12
Exhibit 4-5   Total Vertical Gob Project Costs in Various U.S. Coal Basins	   4-12
Exhibit 4-6   Total Cross-Measure Borehole Project  Costs in  Various  U.S.  Coal
             Basins	   4-13
Exhibit 4-7   Capital Costs for Power Generation  	   4-14
Exhibit 4-8   Capital Costs for Pipeline Injection All Equipment Needed Between the
             Wellhead and a Central Compressor	   4-15
Exhibit 4-9   Operating Costs for Pipeline  Injection All Equipment Needed Between the
             Wellhead and a Central Compressor	   4-16
Exhibit 4-10  Capital Costs for Pipeline Injection Gathering Lines to Main Commercial
             Pipeline	   4-16
Exhibit 4-11  Capital Costs for Vertical Wells (per  well costs)	   4-23
Exhibit 4-12  Break-Even Energy Costs for Mine Ventilation Air	   4-29
Exhibit 4-13  Integrated Recovery	   4-32

CHAPTER FIVE
FOSSIL FUEL COMBUSTION
Exhibit 5-1    Summary of Options for Reducing Methane Emissions from  Fossil Fuel
             Combustion	   5-2

CHAPTER Six
RUMINANT LIVESTOCK
Exhibit 6-1  a  Summary   of  Mechanical   and   Chemical   Feed   Processing
             Optionsrlmproved  Nutrition Through Mechanical  and Chemical  Feed
             Processing	   6-6
Exhibit 6-1  b  Summary of Strategic  Supplementation Options:lmproved  Nutrition
             Through Strategic  Supplementation and Other Options	  6-7
Exhibit 6-1  c  Summary 'of Production Enhancing  Agents:   Production  Enhancing
             Agents   	   6-8
Exhibit 6-1  d  Summary of Options for Improved Genetic Characteristics,  Improved
             Reproduction, and Other Strategies  	  6-9
Exhibit 6-2   Typical  Compositions of Molasses/Urea Multinutrient Blocks	   6-17

CHAPTER SEVEN
LIVESTOCK MANURE
Exhibit 7-1    Phases of Anaerobic Digestion	  7-2
Exhibit 7-2   Impact on Methane Potential by Manure Management System	  7-2
Exhibit 7-3   Summary of the Technical Assessments for Livestock Manure  	  7-5
Exhibit 7-4   Schematic of a Covered Lagoon Digester System	  7-7
Exhibit 7-5   Covered Lagoon Biogas  Recovery  System	   7-10
Exhibit 7-6   Components of an Anaerobic  Digester  	   7-12
Exhibit 7-7   Floating  Gas Holder System	   7-13
Exhibit 7-8   Fixed Dome Digester System	   7-14
Exhibit 7-9   Gas Requirements of End Use Technologies  	   7-16
Exhibit 7-10  Treatment and  Utilization of Digester Effluent  	   7-16

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Exhibit 7-11   Digester Construction Costs ($/cubic meter volume)   	   7-17
Exhibit 7-12  Schematic Diagrams  of Anaerobic Digesters  	   7-20
Exhibit 7-13  Plug Flow Digester	   7-21
Exhibit 7-14  Complete Mix Digester	   7-23
Exhibit 7-15  Estimates of Economically Feasible Projects  	   7-25
Exhibit 7-16  Digester Design/Manure System Compatibility	   7-26

CHAPTER EIGHT
WASTEWATER MANAGEMENT
Exhibit 8-1    Wastewater Treatment Systems and Methane Production	  8-2
Exhibit 8-2    Summary of Options for Reducing Methane Emissions from Wastewater
             and Sludge Management	   8-5
Exhibit 8-3    Conventional Activated Sludge Wastewater Treatment Process ....   8-10
Exhibit 8-4    Trickling Filters Wastewater Treatment Process	   8-11
Exhibit 8-5    Rotating Biological Contactors Wastewater Treatment Process ....   8-12

CHAPTER TEN
RICE CULTIVATION
Exhibit 10-1   Methane Production and Emission from Flooded Rice Fields	   10-2
                                        VI

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                                     Foreword

      I am pleased to transmit the attached report. Options for Reducing Methane Emissions
Internationally. Volume I: Technological Options for Reducing Methane Emissions, in partial
fulfillment of the Congressional mandate in  the Clean Air Act  Amendments  of 1990 for a
series of methane-related reports. This report describes an array of available technologies and
practices which may have been employed to some extent around the world.

      I  am pleased to ,be transmitting a  report that  represents  the results  of  a large
international effort.  The report was prepared in part for the Response Strategies Working
Group of the Intergovernmental Panel on Climate Change  (IPCC) by the U.S. /Japan Working
Group on Methane. As part of this process, much of the information and numerous comments
were submitted by IPCC participating countries.

      The report is the most detailed and comprehensive examination of technologies and
practices for reducing methane emissions that has been developed.  As such, it will assist
greatly in discussion of how methane emissions can be reduced as part of many countries'
efforts to stabilize their emissions of greenhouse gases.

      The report also  establishes a strong  foundation for the next volume  of this report,
Options for Reducing Methane Emissions Internationally. Volume II: International Opportunities
for Reducing Methane Emissions, which assesses the most appropriate technologies for use
in  different  settings and  the  types of programs  which may  be  the most effective  in
accelerating their adoption.
                                                   Paul M. Stolpman
                                                   Acting Directory
                                                   Office of Atmospheric Programs,
                                                   Office of Air and Radiation
                                        VII

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                                 Acknowledgements

      This report has been possible due to the efforts of a large number of people. The
report  began  as an  effort  by the  U.S./Japan  Working  Group  on  Methane  for  the
Intergovernmental Panel on Climate Change's Response Strategies Working Group (Working
Group  3), a  group tasked with  assessing  available options for  reducing  emissions  of
greenhouse gases. As part of this process international experts submitted materials describing
available technologies and circumstances in their countries and regions (as acknowledged at
the end of each chapter) and  provided technical reviews of the overall report.   These
contributions  are greatly  appreciated.  In particular, the efforts, by Japanese experts  as
coordinated by Dr.  Katsuya  Sato have made a large contribution to this report.

      Substantial work was performed to sysnthesize the available information into the final
chapters. This work includes efforts by Jeff Fiedler, Michael Gibbs, Katherine Stenberg, Eric
Taylor, Laura  Van Wie and Kwang Liew.

      Useful comments were provided by industry, university, and government experts in the
U.S. and other countries, and all comments are greatly appreciated.  Comments of particular
importance were provided by Ken Andrasko (USEPA), Lee  Baldwin (UC Davis), Bill Breed (US
DOE), Bob Dixon (USEPA), Charles Dixon (Jim Walter Resources Inc.), Gary Evans (USDA),
Jeff Hardy (US DOE), Andy Hashimoto (University of Oregon), Nelson Hay (American Gas
Association), Don Johnson (Colorado State), Ron Leng (Australia), Katsu Minami (Japan), Ron
Munkley (Consumers Gas of Ontario), Heinz-Ulrich  Neue (IRRI), Mac Safley (North Carolina
State University), Jeffrey Schwoebel (Resource Enterprises Inc.), Susan Thornelone (USEPA),
Henry Tyrell (USDA), Hilmar von Schoenfeldt (Island Creek Coal Co.), Ted Williams (US DOE),
and Fritz Wolf (Ruhrgas).
                                        IX

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VOLUME I
EXECUTIVE  SUMMARY
ES.1  Introduction

Methane currently accounts for over 1 5 percent of expected warming from climate change.
While methane's concentration in the earth's atmosphere is small, it has a sizable contribution
to potential future warming because it is a potent greenhouse gas and because methane's
concentration has been increasing dramatically.   Its  global  concentration  has more than
doubled over the last two centuries, after remaining fairly constant for the preceding 2,000
years and continues to rise. Atmospheric methane concentrations are expected to continue
to increase, although the  rate of increase appears to have slowed down  in  the last several
years.  The reason for this is not currently understood (WMO, 1990; Steele et al., 1992).

Methane's rising concentration is largely correlated with increasing populations, and currently
about 70 percent of global methane emissions are associated with human activities such as
energy production and use (coal mining, oil and natural gas systems, fossil fuel combustion);
waste management  (landfills and wastewater treatment); livestock management (ruminants
and wastes); biomass burning; and rice cultivation.

Reductions in methane emissions of 30 to 40 million metric tons per year, or about 10 percent
of annual anthropogenic (human related) emissions, would halt the annual rise in  methane
concentrations.  This report identifies technologies and practices which are  currently available
for reducing emissions from the major human-related sources of methane, which are profitable
in many cases,  and which are appropriate  for many  countries  around the world.  It also
examines the potential for reducing methane emissions from some  key  countries through
further adoption and use of these available technologies. This report has two volumes:

•  Volume I:  Technological Options for Reducing Methane  Emissions.  This  volume was
   prepared in part  for the Response Strategies  Working  Group of the Intergovernmental
   Panel on Climate Change (IPCC) by the U.S./Japan Working Group on  Methane.  The
   technology assessments were compiled  from  information and comments  submitted by
   IPCC participating countries and have been reviewed by government officials and  technical
   experts in these countries.

•  Volume II:  International Opportunities for Reducing Methane Emissions.   This volume
   investigates the potential for applying or expanding the use of available technologies in key
   countries around the world, for the major methane sources.  Key barriers  inhibiting the
   further use of these technologies and practices are identified, and possible solutions, such
   as technology transfer programs, are suggested.

The report has been prepared in response to a Congressional  request under  Section 603 of
the Clean Air Act Amendments of 1990:

      Preventing Increases in Methane Concentrations: Not later than two years after
      the enactment of this Act, the Administrator shall prepare and submit to the
      Congress a report  that analyzes the potential for preventing an increase  in

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ES - 2                                                              EXECUTIVE SUMMARY
       atmospheric concentrations of methane from activities and sources in other
       countries.  Such report shall identify and  evaluate the technical options for
       reducing methane emissions from each of the activities listed in subsection (b),
       as well as other activities or sources that are deemed by the Administrator in
       consultation  with other relevant Federal  agencies  and departments  to  be
       significant and shall include an evaluation of the costs. The report shall identify
       the emission reductions that would need to be achieved to prevent increasing
       atmospheric  concentrations  of  methane.   The  report shall  also identify
       technology transfer programs that could promote methane emission reductions
       in lesser developed countries.1

Another report, Options for Reducing Methane Emissions from  Anthropogenic Sources in the
United States, was requested by Congress and is being prepared to examine the applicability
of available options in the U.S.
ES.2 Volume I.  Assessments of Technological Options

In general, technological options for reducing methane emissions into the atmosphere are
available for each of the following major methane sources, which represent about 70 percent
of the current emissions from human-related activities:

   • Oil and Natural Gas Systems;

   • Coal Mining;

   • Landfills;

   • Ruminant Livestock;

   • Livestock Manure.
Options are also available, for reducing methane emissions from the treatment of wastewater,
although  less  is  known about this source.   Efforts are still  required  to  develop and
demonstrate options for reducing  methane emissions from  rice  cultivation  and biomass
burning.

Many of the technological options currently available may be cost-effective in many regions
of the world, and  have already been implemented to a  limited extent.  The available options
represent different levels of technical complexity and capital needs and therefore should be
adaptable to a wide variety of country situations. In many cases, furthermore, implementation
of these options provides a range of benefits  in addition to methane reductions, including
better air quality, better protection of surface and groundwater, enhanced animal productivity,
reduced risk of explosion and  fire, and  improved use of energy resources.
      Section 603(c)(2) of the Clean Air Act Amendments of 1990.

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EXECUTIVE SUMMARY                                                               ES - 3
A summary of the major options for reducing methane emissions into the atmosphere is
provided in Exhibits ES-1, ES-2, and ES-3. Discussions of the available technologies for each
of the major methane sources follow.

Oil and Natural Gas Systems

Methane is the primary constituent of natural gas, and significant quantities of methane can
be emitted to the atmosphere from components and operations throughout a country's natural
gas system.   This system generally includes  gas and  oil  wells, processing and storage
facilities, and  transmission and distribution systems. Emissions primarily result from  the
normal operations of many natural gas system components, such as venting and flaring at oil
and gas wells, compressor station operations, gas processing facilities, gas-operated control
devices, and unintentional leaks (fugitive emissions).  Methane emissions also occur  during
routine maintenance, with additional emissions from unplanned system upsets.  Estimates for
methane emissions  froVn  oil  and natural  gas  systems  worldwide  range  from 30  to  70
teragrams2 (Tg) per year.3

The technical nature of emissions from natural gas systems is well understood, and emissions
are largely amenable to technological solutions, through enhanced inspection and preventative
maintenance,  replacement of equipment with  newer designs, improved rehabilitation and
repair, and other changes in routine operations.  Reductions in emissions on the order of 20
to 80 percent are possible at particular sites, depending  on  site specific conditions.  These
reduction options can also result in improved safety, increased productivity through reduced
losses, and improved air quality.   Identified options include:

   Reduced Venting  and Flaring  During Production:  Venting during the production of both
   associated and non-associated gas is a controllable  release of natural  gas.  The most
   preferable strategy is to fully recover and process associated gas for use as a fuel. Where
   demand for gas and an adequate infrastructure do not currently exist, reinjecting  gas or
   installing inexpensive flares can almost completely eliminate methane  emissions while
   providing the important benefits of maintaining formation pressure (reinjection only) and
   enhancing  safety.  The use  of more efficient  flares can also reduce  emissions from
   unburned  gas.  Additionally,  changes  can be made  in operating practices to reduce
   extraction  losses and emissions from wells  under  development.

   Improved Compressor Operation:  Enhanced maintenance and monitoring the fuel  use of
   compressor prime movers can reduce fuel costs while also reducing methane emissions.
   Using gas turbines in place of reciprocating engines to power compressors can reduce
   methane emissions (per unit  of gas used)  by over an order  of magnitude, as well as
   reducing emissions of  other pollutants such as CO and NOX. Reductions can also be
   achieved by capturing  gas  that is currently vented during stops and starts, and using
   auxiliary power (i.e., hydraulic) for turbine starts (rather than gas pressure).
      One teragram is 10  grams, or one million metric tons.

   3   Of this total 25 to 42 Tg are estimated for natural gas systems, and 5 to 30 Tg are estimated for oil
      systems (IPCC,  199,2).

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EXECUTIVE SUMMARY                                                               ES - 7
Improved  Leak Detection and Pipeline Repair:  Gas pipelines are subject to corrosion  and
subsequently develop chronic leaks (i.e., small, continual leaks). Preventing and repairing
these leaks will reduce fugitive emissions. This can be achieved through a number of actions
including improved  leak detection  and pipeline inspection,  preventative maintenance  and
replacement programs, and the  increased use of corrosion resistant materials (e.g., coated
steels, PVC, PE).  In addition, gas releases resulting from line breakages can be reduced with
automatic shut-off valves.

   Low Emission Technologies and Practices: Emissions occur from routine operations and
   practices, including gas-operated control devices, fugitive emissions from  component
   joints,  and pipeline purging for maintenance purposes.  Low emission technologies include
   pipeline control devices with reduced or eliminated venting of  natural gas ("low-bleed" or
   "no-bleed" devices), directed inspection and maintenance programs, and the capturing of
   purged gas.
Coal Mining

Methane is produced during coalification (the process of coal formation) and remains trapped
under pressure in the coal seam and surrounding rock strata.  This trapped  methane  is
released during the mining process when the coal seam is fractured. Current annual emissions
of 30 to 50 Tg are expected to rise over the next decades with increases in global coal
production and a continuing trend to deeper mines.

Techniques for removing methane from  underground mine workings  have been developed
primarily for  safety reasons, because  methane  is highly  explosive  in  air concentrations
between 5 and 1 5 percent and is  the cause  of numerous  mining accidents.  These same
techniques can be adapted to recover methane so that the energy value of this fuel is not
wasted.  Methane emissions into the atmosphere can technically be reduced by up to 50 to
70 percent at gassy mines using available techniques. Emissions could potentially be reduced
by up to  90  percent at these same gassy mines, depending  upon the demonstration of
additional technologies.

Important factors when considering options for reducing methane emissions from coal mining
are: the geologic and reservoir characteristics  of the coal basin; mine conditions and mining
method;  current  mine gas  recovery systems; potential  gas  quality and use options;  and
technical and  economic capabilities. In particular, the recovery method largely determines the
quality and quantity of gas recovered,  which in turn  determines the  possible utilization
options.  Developing uses for recovered methane is required if emission reductions are to be
achieved. The sale and/or use of methane can offset the costs of  recovery in certain cases.
Furthermore,  improving  methane recovery techniques can,  result  in safer, more productive
mines, with lower ventilation costs. Available recovery and use options  are summarized as
follows:

   Enhanced Gob Well Recovery:  Methane can  be recovered from the gob area of a coal
   mine - the highly fractured area of coal and rock that is created by the caving of the mine
   roof after  the coal is removed.  Gob areas can release significant quantities of methane
   into  the mine,  and if  this gas  is  recovered before  entering  the  mine, ventilation
   requirements can bq reduced. Typically, gob gas is diluted by mine air during production

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ES - 8                                                              EXECUTIVE SUMMARY


   so a medium quality gas is obtained (300-800 Btu/cf; 11-29 MJ/m3)4, which can be used
   in a variety of applications, including on-site  power generation,  and residential and
   industrial heating.  Enhanced gob well recovery can involve in-mine and/or surface wells,
   using proven technology that is currently employed in many countries. In many cases, the
   capital requirements for these energy  development projects are low  compared to the
   amount of gas that may be produced. Methane emissions from a mine can be reduced by
   30 to 50 percent.

   Pre-Mining Degasification:  This strategy recovers methane before coal is mined.  Pre-
   mining degasification can be attractive where geologic conditions are appropriate because
   methane is removed before the air from the mine workings can  mix with it.  Pre-mining
   degasification  typically recovers a higher quality gas (900-1000 Btu/cf; 32-37 MJ/m3)
   which can be used as chemical feedstock in addition to being used for power generation
   and industrial or residential applications.  Pre-mining degasification can be an in-mine or
   surface operation.  When done inside the mine, boreholes can be drilled anywhere from
   six months to  several years in advance of mining.  Surface drilled vertical wells can be
   drilled anywhere  from  2 to  more than  10 years in advance  of  mining.  Pre-mining
   degasification requires more advanced technology and equipment than enhanced gob well
   recovery, and therefore has higher capital costs. These higher costs can be justified by
   the increased recovery of methane using surface drilling techniques.

   Ventilation Air Utilization: Most mine gas  is released to the atmosphere in the ventilation
   air used in the mine. Ventilation, necessary in underground coal mines for safety reasons,
   is achieved with large fans which blow air through the mine. The recovery technology is
   basic, but the operating costs of running the fans can be hiqh if the mine is gassy.  The
   methane content of the vented air must be below 5 percent for safety reasons,  and is
   frequently as low as 0.5 percent to comply with relevant regulations.  In spite of its low
   concentration,  it  appears that there  may be opportunities to use ventilation  air as
   combustion air in turbines or boilers. However, the technical and  economic feasibility has
   not yet been demonstrated.

   Integrated Recovery: The most significant methane emission reductions are likely to occur
   by employing a combination  of methane  recovery strategies.  Indeed, many U.S.  coal
   mines currently use a  combination  of in-mine and surface recovery methods both before
   mining and from gob areas. The technological and capital requirements of such integrated
   systems are likely to be moderately high, but it is possible that the additional opportunities
   for gas utilization,  as well as the enhanced mine safety,  could  justify the required
   investment.
Fossil Fuel Combustion

Methane emissions from fossil fuel combustion are a result of incomplete combustion.  Even
if methane (natural gas) is not a  component of the fuel, it  can be created during the
combustion process. Preliminary estimates indicate that 4 to 5 Tg of methane are released
from this source per year, with the majority of  the emissions  resulting from stationary
      British Thermal Units per cubic foot; million (mega-) joules per cubic meter.

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EXECUTIVE SUMMARY                                                              ES - 9
sources.   Total emissions are dependent upon  such factors as the total amount of fuel
combusted and the extent of incomplete combustion.  Several  methane reduction options
have been identified, although many of them require further study to estimate the magnitude
of possible reductions.  In general, options for reducing methane emissions from combustion
are consistent with efforts to improve energy efficiency and reduce emissions of air pollutants
from both stationary and  mobile sources.

   Improved Fuel Use Efficiency: The primary method for reducing fuel use is to improve
   energy efficiency. Continuing activities to increase fuel use efficiency in all sectors should
   contribute to decreases in methane emissions per unit of energy output.

   Exhaust  Controls:  Exhaust controls such as catalytic converters can also be used to
   remove methane and  other  air  pollutants (e.g., NOX) from  exhaust,  thereby reducing
   emissions of these gases.  The use of catalytic converters in automobiles has already
   reduced methane emissions from the transport sector in many countries.

   Improved Combustion Efficiency:  The amount of methane emitted per unit  of fuel used
   can be reduced by improving combustion efficiency, ensuring that a higher proportion of
   the hydrocarbons are  burned completely.

   Alternative Fuels:  In  the longer-term, increased use of alternative fuels,  such as solar
   power, can reduce fossil fuel  use. Reducing the current reliance on fossil fuels will also
   improve  the energy security  of countries which import a significant  proportion of the
   energy that they use.
Ruminant Livestock

Methane is produced as part of the normal digestion process of ruminant animals (cattle,
buffalo, sheep, goats, 3nd camels).  This methane,  which is exhaled or  eructated by the
animal, represents an inefficiency  -- feed energy converted to methane cannot be used by
the animal for maintenance, growth or production.  Emissions are estimated to be 65 to 100
Tg per year, with  cattle  accounting  for about 75 percent of the global annual methane
emissions from domestic livestock.

Many opportunities exist for reducing methane emissions from ruminant animals by improving
animal  productivity  and reducing  methane  emissions per unit of product (e.g., methane
emissions per kilogram (kg) of milk produced).  In general, a greater portion of the energy in
the animals' feed can be directed to useful product, instead of wasted in the form of methane.
This  leads to smaller size herds required  to produce the same amount of product.  With
adequate resources, current and potential future technologies and management practices can
technically reduce methane emissions per  unit product by 25 to 75 percent in many animal
management systems.

The conditions under which animals are managed vary greatly by country, especially between
developed and  developing countries. Reduction strategies must be tailored to country-specific
circumstances.  Despite the differences in animal management practices among  various
countries, one  common strategy  for  reducing methane emissions is to increase animal
productivity.   Virtually all efforts that improve  animal  productivity  will  reduce methane

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ES - 10                                                             EXECUTIVE SUMMARY


emissions per unit product produced. Options for reducing methane emissions from ruminant
livestock include:

   Improved Nutrition Through Mechanical & Chemical Feed Processing: Improved nutrition
   reduces methane emissions per unit product by enhancing animal performance, including
   weight gain, milk production, work production, and reproductive performance. Mechanical
   and chemical feed processing options include wrapping and preserving  rice straw to
   enhance digestibility, chopping straw to enhance animal intake, and alkali treatment of low
   digestible straws to  enhance digestibility.  These  options  are applicable  to accessible
   ruminant animals with limited or poor quality feed, and may decrease methane emissions
   per unit product on the order of 10 to 25 percent (assuming  feed digestibility is increased
   by 5 percent), depending on animal management practices.

   Improved Nutrition Through Strategic Supplementation:   Strategic  supplementation
   provides critical  nutrients such as  nitrogen and important minerals to animals  on  low
   quality feeds. Additionally, it may include providing microbial and/or bypass protein to the
   animal. Methane emissions per unit product may be reduced by 25 to 75 percent due to
   substantial increases in animal productivity, depending on animal management practices.
   In  particular, applying molasses  urea  blocks (MUBs) and bypass protein  techniques in
   tropical areas with phronic feed  constraints can produce emissions reductions per  unit
   product  near  the  high  end  of the  range.  The use  of  chemicals  (ionophores)  and
   defaunation are also possible options, though further efforts to develop better agents and
   to  demonstrate practical methods of defaunation are necessary.

   Production Enhancing Agents: Certain agents  can  act directly to improve  productivity.
   These agents are generally most applicable to large-scale commercial systems with well-
   developed markets. Emissions reductions per unit product of  5 to 1 5 percent have been
   demonstrated.   Additional reductions may be achieved by  shifts in  rumen  microbial
   patterns.  Options include the use of  bovine somatotropin (bST) and anabolic steroids.

   Improved Production  Through Improved Genetic Characteristics:  Genetic characteristics
   are limiting factors mainly in intensive production systems.  Continued  improvements in
   genetic potential  will increase productivity, and thereby reduce  methane emissions  per unit
   product.  Emissions reductions from these options remain to be quantified.

   Improved Production Efficiency Through Improved Reproduction:  Large portions of the
   herd of large ruminants are maintained for the purpose of producing offspring.  Methane
   emissions per unit product  can be significantly reduced  if  reproductive  efficiency is
   increased and fewer animals are required to provide the desired number  of offspring.
   Options  such as  artificial insemination, twinning, and embryo transplants  address
   reproduction directly.   The nutritional  options described  above can   also improve
   reproduction.

   Other Techniques:  Additional options include disease control  and the control of product
   markets and prices in countries with surplus dairy products.

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EXECUTIVE SUMMARY                                                              ES - 11
Livestock Manure

Methane is produced  during anaerobic decay of the  organic material in livestock manure.
Manure management  systems that store manure under anaerobic conditions are the major
contributors to methane emissions from this source. Global emissions are estimated to range
from 20 to 30 Tg per  year.

Methane emissions from anaerobic digestion constitute a wasted energy resource which can
be recovered by adapting manure management and treatment practices to facilitate methane
collection.  This methane can be used directly for on-farm energy, or to generate electricity
for on-farm use or for sale. The other products of anaerobic digestion, contained in the slurry
effluent, can be utilized  in a  number of ways,  depending  on local needs  and resources.
Successful applications include use  as animal feed and  aquaculture supplements, in fish
farming, and as a crop fertilizer.

Additionally, managed anaerobic decomposition is a very  effective method of reducing the
environmental and  human health  problems associated with manure management.   The
controlled bacterial decomposition of the volatile solids in manure reduces the potential for
contamination from runoff, significantly reduces pathogen  levels,  removes most noxious
odors,  and  retains the organic  nitrogen content of the manure.

The  selection of successful  methane emissions reduction options depends on  several
important regional factors, including the ambient temperature and climate; economic, technical
and material resources; existing manure management practices; regulatory requirements; and
the specific benefits of developing an energy resource (biogas) and a source of high quality
fertilizer. Choosing an appropriate strategy is vital to gaining the acceptance of livestock
farmers.  With successful implementation, current reduction options can technically reduce
methane emissions  by as much as 25 to 80 percent  at particular sites.  Identified options
include:

   Covered Lagoons:  The treatment of manure in lagoons is associated with relatively large
   scale intensive farm operations.  Manure solids are washed out of the livestock housing
   facilities with large quantities of water, and the resulting slurry flows into primary lagoons.
   The anaerobic conditions treat manure and usually result in significant methane emissions,
   provided temperatures remain high enough.  Placing an impermeable floating cover over
   the lagoon and applying negative pressure effectively recovers methane which can be
   cost-effectively utilized for electricity generation, farm heating, and refrigeration. Lagoons
   are most common  in North America, Europe, and regions of Asia and Australia.

   Small Scale Digesters: Digesters are designed to enhance the anaerobic decomposition
   of organic  material and to maximize  methane production and  recovery.   Small scale
   digesters typically require a small amount of manure and are relatively simple to build and
   operate. As such, they are an appropriate strategy for regions with technical, capital, and
   material resource constraints. Due to the rising cost of commercial fertilizers, the recovery
   of high  quality fertilizer from digesters can be an even more  important benefit than the
   energy supplied from biogas. A number of different digester designs have been developed.
   These designs are not heated, and while they can operate  in colder regions, they are more
   appropriate for temperate and tropical regions.

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ES - 12                                                              EXECUTIVE SUMMARY
   Large  Scale  Digesters:  The larger, often more technologically  advanced digesters
   described in this section are usually heated, have larger capacities, require greater capital
   investment, and in general  are more complex to build and operate.  However, advanced
   designs can greatly  improve the performance of livestock manure digesters,  and can
   operate in colder regions. This strategy integrates the operation of a digester with current
   manure management practices at large livestock operations, typically in more developed
   regions.  The two primary  digester designs are Complete Mix and Plug Flow digesters.
   Manure quantity  and the percent total solids  of the manure are important  criteria for
   determining the appropriate strategy.
Landfills

Methane is generated in landfills as a direct result of the natural decomposition of solid waste.
The organic component of landfilled waste is broken down by bacteria in a complex biological
process,  which produces  methane,  carbon  dioxide,  and  trace gases.   Because the
methanogenic (methane-producing) stage of this process is anaerobic, methane production is
favored in landfills capped with soil or clay that limits air infiltration.  However, anaerobic
conditions will exist to some extent in any landfill, whether it is covered or not. Landfills are
estimated to produce 20 to 70 Tg of methane per year. Several options have been identified
that can technically reduce methane emissions from landfills by up to 90 percent.  Additional
benefits that result from these strategies  include improved air and water quality, reduced risk
of fire and explosion, and the recovery of a clean and convenient fuel.

   Methane Recovery and Utilization:  Methane can be recovered from landfills, and its energy
   value may be put to a profitable use.  The recovery of methane from anaerobic landfills
   can be a low-cost and relatively low technology option. Recovery efficiencies are typically
   as high as 80 percent, with some projects achieving almost complete recovery. Utilization
   options for the recovered  gas include electricity generation,  direct use  in industry, and
   natural gas supply.

   Aerobic Landfill Management: Using a more complex technology, landfills can be designed
   to be aerobic so that less methane is  produced,  as has been  done in Japan.  Aerobic
   designs increase the rate of decomposition, reduce the emissions of harmful and odorous
   trace  gases, and improve  the quality of leachate.  These advantages are significant  in
   terms of pollution reduction and the  reclamation of landfill sites.  Semi-aerobic landfills
   equipped with single air conduction channels have been able to reduce methane emissions
   by more than 50 percent.  More advanced designs that are still being  developed have
   achieved reductions of over 80  percent in test applications.

   Reduced Landfilling of Waste: The reduced landfilling of waste is an additional  option that
   reduces the quantity of waste placed in landfills.  This can be achieved by recycling and
   reusing  material, incinerating solid  waste and composting organic material, and through
   additional technologies under development.

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EXECUTIVE SUMMARY                                                             ES - 13
Wastewater Management

Wastewater and its solid byproduct (sludge) can result in methane emissions if they are stored
or treated under anaerobic conditions, and if the methane is subsequently released instead of
being flared.  Although data is limited, current estimates for global emissions range from 20
to 25 Tg per year.

The  primary sources of methane emissions from wastewater are thought to be domestic
waste streams in  developing  countries and  wastewater from  food processing  facilities
throughout  the world  (e.g.,   fruit  and  vegetable  plants,  meat  packing  plants  and
slaughterhouses, distilleries, and creameries).  The anaerobic decomposition  of the high
organic components in these waste streams results in the production of methane by bacteria.

Wastewater treatment plants in developed countries are not a major source of methane, as
they rely primarily upon aerobic treatment, or anaerobic treatment in enclosed systems where
the methane is recovered and utilized. These treatment practices can be employed in other
regions where unmanaged waste streams and anaerobic storage and treatment practices are
thought to produce significant methane emissions.
Biomass Burning

Methane is produced by incomplete combustion during biomass burning. The most common
sources of anthropogenic biomass burning include agricultural and land management practices,
such as deforestation  due to population pressures,  swidden ("slash-and-burn", shifting)
agriculture, burning savannah and rangelands to improve  livestock forage,  and prescribed
burning of unwanted vegetation, logging debris, or agricultural residues. Firewood, charcoal,
agricultural residues and livestock manure are also commonly  burned as fuel. Although net
global  methane  emissions from biomass  burning  (including  deforestation) are not well
quantified due to the lack of data on the amount of biomass burned, fire frequency, and fire
characteristics, estimates range from 20 to 80 Tg annually.

Strategies to  reduce methane  emissions  focus on reducing the amount of forest and
agricultural biomass burned, thus reducing emissions of all greenhouse gases from this source
(i.e., direct greenhouse  gas emissions of carbon dioxide (CO2), methane (CH4), and nitrous
oxide (N2O); and tropospheric ozone  precursors such as CO  and NOX).  Such approaches
include sustainable forest management through fire management and deforestation reduction
and alternative agricultural practices  which minimize forest clearing and  burning of crop
residues. These approaches are largely subsumed under strategies currently being discussed
for maintaining species diversity and reducing rates of deforestation. Other strategies include
promoting efficient combustion devices for biomass fuels,  and modification of the types of
stoves and fuels  used for burning biomass as an energy source.

Opportunities exist to implement these types  of programs, especially in tropical and sub-
tropical regions.  These opportunities have not been well  characterized, however, and  no
estimates  of possible reductions have been made.

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ES - 14                                                              EXECUTIVE SUMMARY
Rice Cultivation

Methane is produced in the  soils  of flooded rice  fields,  largely from  the  anaerobic
decomposition of organic material by  methanogenic  bacteria.  The methane that is not
oxidized in the soil or the plant is transported into the atmosphere by plant-mediated transport,
diffusion through the floodwater, leaching, and ebullition. Although much research is needed
to better quantify global methane emissions from rice, it is estimated that rice fields annually
contribute 20 to 1 50 Tg  of methane to the atmosphere. These emissions are expected to
grow over the next  three decades.

Although the production and emission of methane from rice fields are not fully understood,
present knowledge  indicates  that various management practices could potentially achieve
significant  reductions.  Such alternative practices  include changes in  cultivar  selection,
nutrient applications,  water  management and  cultivation practices.   Recognizing  that
maintaining  or increasing rice productivity as well  as satisfying other social and  cultural
constraints are fundamental objectives, it is believed that 10 to 30 percent reductions from
current levels of methane emissions may be possible over the  long term.

Substantial research is necessary to identify, develop, and demonstrate management practices
which are applicable in different rice growing regions.  The formation of a research consortium
of the major rice-growing countries has been proposed to help  identify the most appropriate
and feasible mitigation opportunities  while increasing rice productivity.  Options developed
through such research would  be available by 2005 to 2010.

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EXECUTIVE SUMMARY                                                           ES - 15
ES.3 References

Steele, L.P., E.J. Dlugokencky, P.M. Lang, P.P. Tans, R.C. Martin, and K.A. Masarie (1992),
"Slowing Down of the Global Accumulation of Atmospheric Methane  During the 1980's,"
Nature, vol. 358, July 23, 1992, pp 313-316.

WMO (World Meteorological Organization) (1990), Scientific Assessment of Stratospheric
Ozone:  1989. World  Meteorological Organization Global Ozone Research and Monitoring
Project - Report No. 20. Geneva, Switzerland.

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CHAPTER ONE
INTRODUCTION
This report evaluates international options for reducing methane emissions from anthropogenic
(human related) sources through the use of technologies that are either currently in use or
under development. This report has been prepared in partial fulfillment of Section 603 of the
Clean Air Act Amendments of  1990,  which requires that the EPA prepare  and submit to
Congress a series of reports on domestic and international issues concerning methane.  As
one of this series of reports, EPA has been requested to evaluate opportunities to  reduce
methane emissions in countries other than the United  States:

   Preventing Increases in Methane Concentrations:  Not later than two years after  the
   enactment of this Act, the Administrator shall prepare and submit to the Congress a
   report that analyzes the potential for preventing  an  increase  in  atmospheric
   concentrations of methane from activities and sources in other countries.  Such report
   shall identify and evaluate the technical options for reducing methane emissions from
   each of the activities listed in subsection (b), as well as other activities or sources that
   are deemed by the Administrator in consultation with other relevant Federal agencies
   and departments to be significant and shall include an evaluation of the costs.  The
   report shall identify the emission reductions that would need to be achieved to prevent
   increasing  atmospheric  concentrations of  methane.  The report shall  also identify
   technology transfer programs that could promote methane emission reductions in
   lesser developed countries.5

This report  has two  volumes.   The  first presents technical  assessments  of  the  key
technological  options  for  reducing  methane emissions, and  the second focuses  on
opportunities to reduce emissions in some  of the key emitting countries.

The first volume, Technological Options for Reducing  Methane Emissions,  was prepared in
part for the Intergovernmental Panel on Climate Change (IPCC) Response Strategies Working
Group (RSWG), by the U.S./Japan Working Group on Methane. The technology assessments
were compiled from information and comments submitted by IPCC participating countries.
The findings presented in this report indicate that technological  options exist for  reducing
emissions from most of the major methane sources, including oil and natural gas systems,
coal mines, landfills, ruminant livestock, and livestock manure.

The second volume, International Opportunities for Reducing Methane Emissions, investigates
the potential  for applying or expanding the use  of available technologies in key emitting
countries around the world6, for the major methane sources. The key barriers in various
countries which are hampering the expansion of methane recovery projects are identified and
      Section 603(c)(2) of the Clean Air Act Amendments of 1990.

      These are countries other than the United States.  Options for reducing methane emissions in the U.S.
      are examined separately in USEPA (1993b), "Opportunities to Reduce Methane Emissions in the United
      States," Report to Congress (review draft).

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1 - 2                                                                       INTRODUCTION
types of technology transfer programs which may address these barriers and achieve emission
reductions are discussed.

1.1   Background:  The Importance  of Methane

Methane is an important greenhouse  gas and  a major environmental pollutant.  Methane is
also the primary component of natural gas and a valuable energy source. Methane emission
reduction strategies offer one of the most effective means of mitigatinq global warming in the
near term for the following reasons:

•   Methane is one of the principal  greenhouse gases, second only to carbon  dioxide (CO2)
    in  its contribution to potential global warming. In fact, methane is responsible for roughly
    18 percent of the total contribution in  1990 of all greenhouse gases to "radiative forcing,"
    the measure used to determine the extent to which the atmosphere is trapping heat due
    to emissions of greenhouse gases (IPCC, 1992a).7

•   Methane concentrations are rising rapidly.  The atmospheric concentration  of methane is
    increasing at a rate of about 0.6 percent per year (Steele et al.,  1992) (in contrast to CO2
    concentrations, which are increasing  by about 0.4 percent per year)8, and has more than
    doubled over the last two centuries (IPCC, 1992a).

•   Methane is  a potent contributor to global  warming.  On a kilogram for kilogram basis,
    methane is  a more  potent greenhouse  gas than C02 (about 60 times greater after 20
    years, 20 times greater after 100 years, and 9 times greater after 500 years).9

•   Reductions  in  methane  emissions will  produce substantial benefits in the  short run.
    Methane has a shorter atmospheric lifetime than other greenhouse  gases: methane lasts
    around 10 years in the atmosphere, whereas C02 lasts about 120 years (IPCC, 1992a).
    Due to methane's high potency and short lifespan, stabilization of methane emissions will
    have  a  rapid impact on mitigating  potential climate change.

•   Methane stabilization is nearly as effective as stabilizing C02 emissions at 1990 levels.
    In order to stabilize methane concentrations at current levels, total anthropogenic methane
    emissions would need to  be reduced  by about 10 percent.  This methane concentration
   7   Global contribution to radiative forcing by gas is estimated on a carbon dioxide equivalent basis using
       IPCC (1990al global warming potentials for a 100-year time horizon, including direct and indirect effects
       of methane.

   8   Based on measurements taken at Mauna Loa from 1970 to 1990 (Oak Ridge National Laboratory,  1992).

   9   Methane is reported to have a direct Global  Warming Potential (GWP) of 11 over a one hundred year
       timeframe, and to have indirect effects that could be equal in magnitude to its direct effect (IPCC,  1992).
       Over a fifty year timeframe, the direct GWP would be on the order of 25 to 30.  The GWP reflects the
       effect that releasing a kilogram of methane would have over a specified time horizon, relative to releasing
       a kilogram of carbon dioxide.  While the GWP of methane continues to be uncertain, efforts by the IPCC,
       EPA's Office of Research and Development, and others, should  begin to resolve these uncertainties over
       the next few years.

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INTRODUCTION                                                                      1 - 3
   stabilization would have roughly the same effect on actual warming as maintaining C02
   emissions at 1990 levels (Hogan et al., 1991).

•  In contrast to the numerous sources of other greenhouse gases, a few large and gassy
   facilities often account for  a large portion of methane emissions.  Therefore, applying
   emission reductions strategies to these  gassiest facilities would result in a substantial
   decrease in estimated current and future methane emissions levels.

•  Because methane is a source of energy as well as a greenhouse gas,  many  emissions
   control options have  additional economic benefits.  Methane emissions are usually  an
   indication of inefficiency in a system.  In many cases, methane that would otherwise be
   emitted to the atmosphere  can be recovered and utilized, or the quantity  of methane
   produced can  be  significantly reduced through  the  use of cost-effective management
   methods. Therefore, emissions reduction strategies have the potential to be low-cost, or
   even profitable. For example, methane recovered from coal mines, landfills, and livestock
   manure systems can be used as an energy  source, and  options for  reducing methane
   emissions from livestock can also improve the productivity of each animal.

•  Well-demonstrated technologies are commercially available for profitably reducing methane
   emissions.  For the major  sources  of anthropogenic  methane emissions  (except rice
   cultivation and biomass burning),  cost-effective  methane reduction technologies are
   already commercially available.  Additionally,  a number of other technologies  are under
   development. While offering substantial emission reductions and economic benefits, these
   technologies have not been  implemented on a wide scale in the U.S. or globally because
   of financial, informational, and institutional barriers.

The unique characteristics of methane emissions demonstrate the importance of promoting
strategies to reduce the amount of methane discharged into the atmosphere. Understanding
the sources of methane  emissions, and in particular the emissions from systems that are
partially controllable, is  the first  step  in  identifying cost-effective  options for  reducing
emissions.
What is Methane?

Methane (CH4)  is a  radiatively  and chemically active trace  greenhouse  gas.10  Being
radiatively active, methane traps infrared radiation (IR or heat) and helps warm the earth. It
is currently second only to carbon dioxide in contributing to potential future warming. Being
chemically active, methane enters into chemical reactions in the atmosphere that increase not
only the abundance  of  methane,  but  also  atmospheric concentrations of ozone11  and
stratospheric concentrations of water vapor,  which  are both greenhouse gases.
   10   A trace gas is a gas that is a minor constituent of the atmosphere. The most important trace gases
       contributing to the greenhouse effect include water vapor, carbon dioxide, ozone, methane, ammonia,
       nitrous oxide, and sulfur dioxide.

   11   While methane does not contribute significantly to the formation of urban smog, methane  is a major
       concern in the formation of ozone in the free troposphere.

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1 - 4                                                                    INTRODUCTION
Methane is emitted into the atmosphere largely by anthropogenic sources, which currently
account for approximately 70 percent of the estimated 500 teragrams (Tg) of annual global
methane emissions.12 Anthropogenic sources of methane emissions include: natural gas
and oil systems; coal mining;  landfills; domesticated ruminant livestock; liquid and solid
wastes; rice cultivation; and biomass burning.  Natural sources of methane, which currently
account for  the remaining  30 percent of global emissions, include  natural wetlands  (e.g.,
tundra, bogs, swamps), termites, wildfires, methane hydrates, oceans and freshwaters.

The concentration of methane in the atmosphere is determined by the balance of input rate,
which is increasing due to human activity, and the removal rate. The primary sink (removal
mechanism) for atmospheric methane is  its  reaction with  hydroxyl  (OH)  radicals in the
troposphere.  In this reaction, methane is converted into water vapor and carbon monoxide,
which is in turn converted into carbon dioxide (C02)-  The atmospheric concentration of OH
radicals is determined by  complex reactions  involving methane, carbon monoxide, non-
methane hydrocarbons (NMHC), nitrogen oxides, and tropospheric ozone.  The size of an OH
sink can vary and may actually  decrease in response to increasing levels of methane (IPCC,
1992a). A small amount of methane is also removed from the atmosphere through oxidation
in dry soils. Compared to removal by reaction with OH, this oxidation mechanism is believed
to be relatively small.  There are no significant anthropogenic activities that remove methane
from the atmosphere. Methane's atmospheric lifetime is presently estimated to  be about 10
years (IPCC, 1992a).
Atmospheric Levels of Methane Are Rising

The concentration of methane in the atmosphere has been steadily increasing.  The rise in
methane concentrations has been  well documented in recent studies and corroborated by
measurements from different locations and several monitoring groups. The principal methods
for estimating  methane concentrations over time have been  analysis of ice core data and
direct atmospheric  measurements.

Analyses of ice cores in Antarctica and Greenland have yielded estimates of atmospheric
methane concentrations of approximately 0.35 parts per million by volume (ppmv) to 0.65
ppmv for the period between 10,000 and 160,000 years ago. Similar analyses  of air in ice
cores have placed atmospheric methane concentrations at approximately 0.8 ppmv for the
period between 200 and 2,000 years ago. The level of methane rose to about 0.9 ppmv at
the beginning of this century (IPCC, 1990a).

Direct measurement of the global atmospheric methane concentration was begun in 1978.
At that time, the global atmospheric methane concentration was calculated to be 1.51 ppmv.
In 1990, the level  was approximately  1.72  ppmv -- nearly double the concentration level
estimated for the beginning  of this century (IPCC, 1990a). A summary of the ice core data
and direct measurement data showing the increase in atmospheric methane concentrations
is provided in Exhibit 1-1. In addition to ice core data and direct atmospheric measurements,
   12  The portion of total methane emissions from anthropogenic sources is based on IPCC (1992a).  Total
      annual methane emissions is based on Crutzen (1991).

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INTRODUCTION
1 -5
analysis of infrared solar spectra has shown that the atmospheric concentration of methane
increased by about 30 percent over the last 40 years (Rinsland et al., 1985).

At present, the atmospheric level of methane is approximately 4,900 Tg (IPCC, 1990a); this
amount is thought to be increasing by about 30 to 40 Tg  per year (Steele et  al., 1992).
Atmospheric methane concentrations are expected to continue to increase, although global
measurement programs indicate that the rate of increase appears to have slowed in the last
several years (WMO, 1990; Steele et al., 1992).  The reason for this is not currently well
understood.   Given a continuation of  the current  annual rate of increase of atmospheric
methane of about 0.0095 to 0.0133 ppmv, the atmospheric concentration of methane would
exceed  2.0 ppmv  by the year  2020.  Recent models of expected future emissions and
atmospheric processes indicate that without controls, atmospheric concentrations could range
from 3.0 ppmv to over 4.0 ppmv by the year 2100 (USEPA, 1989; IPCC, 1992a), although
these scenarios should be reinvestigated using the most recent information on methane
concentration trends.
                                    Exhibit 1-1
                           Global Methane Concentrations
                   1800-
                   1300-
                   800-
                   300-
                          • Stpte fcccoflB
                          • BynJ to core
                          • Dye teŤ core
                          ° ttatok kť core
                              10ť      10*     10ť      10*      101
                               Years Before Present (1990 A.D.)
                    OWri** tnm lot CMPH M4 thi NOAA/CMDL tek
  Source: Oak Ridge National Laboratory/Carbon Dioxide Information Analysis Center,
  August 1990.

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1 - 6                                                                        INTRODUCTION
Methane and Global Climate Change

Methane's increasing concentration in the atmosphere has important implications for global
climate change. Methane is very effective at absorbing infrared radiation (IR) reflected by the
earth's surface.   By absorbing IR  and inhibiting  its release into  space, methane  in the
atmosphere contributes to increased atmospheric and  surface temperatures. This process is
commonly referred to as the "greenhouse effect."

A gram of methane is about 35 times more effective at warming the surface of the earth than
a gram of C02 over a 20 year timeframe (IPCC, 1992a).  In addition to this direct radiative
forcing, methane's participation in chemical reactions in the atmosphere indirectly contributes
to global warming by influencing the amount of ozone in the troposphere and stratosphere,
the amount of hydroxyl  in  the  troposphere, and   the  amount of water  vapor   in the
stratsophere; these reactions are discussed in more detail below. Methane's indirect effect
on global warming resulting from these chemical reactions could be equal in magnitude to its
direct effect, although considerable uncertainty remains (IPCC, 1992a).13

When compared to C02, methane's greater direct and indirect impacts per gram of emissions
is mitigated somewhat by its shorter atmospheric lifetime of around 10 years, compared with
approximately 1 20 years for C02 (IPCC, 1992a). Considering methane's atmospheric lifetime
and its effect on tropospheric ozone, a gram ot methane has a global warming potential  (GWP)
21 times greater than a gram of C02 over a  100 year time period  (IPCC, 1 992a). It has been
estimated  that approximately 18  percent  of the  greenhouse effect is due  to increasing
atmostpheric  methane  concentrations.  The total contribution to radiative  forcing of all
greenhouse gases in 1990 is shown in Exhibit  1-2.

Models of  atmospheric  chemical  processes  have  indicated  that increasing  methane
concentrations result in net ozone production in the troposphere and lower stratosphere, and
net ozone destruction in the upper  stratosphere. It has  been calculated that methane's net
effect  in  these processes  is  to cause an  increase  in  ozone (Wuebbles  and Tamaresis,
1992).14

As the most abundant organic species in the atmosphere, methane also  plays an influential
role in determining  the oxidizing  capacity  of the troposphere.   Through reactions with
hydroxyl,  80 to 90 percent of methane destruction occurs in the troposphere (Cicerone and
   13   The  uncertainty in the GWPs for methane result largely from the indirect effects of methane in the
       atmosphere, which have not been fully characterized. Some of these uncertainties will be reduced over
       the next several years through the efforts of the Intergovernmental Panel on Climate Change as well as
       others, including EPA's Office of Research and Development.

   14   As described in IPCC (1990a;, "Ozone plays an important dual role in affecting climate.  While C02 and
       other greenhouse gases are relatively well-mixed in the atmosphere, the climatic effect of ozone depends
       on its distribution in the troposphere and stratosphere, as well as on its total amount in the atmosphere.
       Ozone is a primary absorber of solar radiation in the stratosphere, where it is directly responsible for the
       increase in temperature with altitude. Ozone is also an important absorber of infrared radiation. The
       balance between these radiative processes determines the  net effect of ozone on climate."

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INTRODUCTION
1  - 7
Oremland,  1988). Increasing methane levels could reduce hydroxyl, which would result in a
further increase in the methane concentration. A decrease in the oxidizing capacity of the
                                      Exhibit 1-2
           Global Contribution to Integrated Radiative Forcing by Gas for 19901
                                  CH4  18.0%
                                                           N20 5.0%

                                                                  CFCs  11.0%
                                    CO2 66.0%
  Note: Estimated on a carbon dioxide equivalent basis using IPCC (1990a) global warming potentials
  (GWPs) for a 100-year time horizon. Anthropogenic emissions only.

  1 This chart is used to present a general understanding of methane's contribution to future warming based
  on the GWPs presented in IPCC (1990a). However, these GWPs are constantly being revised due to a
  variety of scientific and methodological issues. It is likely that the contribution of CFCs presented will
  decrease and that the contribution of other gases will be about the same or greater upon further
  investigation.

  Source: IPCC 1990a
troposphere would increase not only the atmospheric lifetime of methane, but also the lifetime
of other important  greenhouse gases,  and would  permit transport of  pollutants  over long
distances, resulting in atmospheric changes even in remote regions (Wuebbles and Tamaresis,
1992).   For example, the atmospheric lifetimes of hydrogenated-CFCs  (HCFCs) may  be
increased, thereby reducing their desirability as substitutes for CFCs.

Finally,  concentrations of stratospheric water vapor (one of the most important greenhouse
gases) should increase as concentrations of methane increase; methane oxidation reactions
roughly produce two moles of water  vapor  for each mole of methane that is destroyed
(Wuebbles and Tamaresis, 1992).  In addition to the impact on global warming, increases in
stratospheric water vapor concentrations as  a result  of increased methane concentrations
could contribute to the  formation  of polar stratospheric clouds (PSCs), which have been

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1 -8
          INTRODUCTION
identified as one factor that enables the chlorine and bromine from chlorofluorocarbons (CFCs)
and  halon compounds  to cause  the severe seasonal  loss  of stratospheric ozone over
Antarctica (WMO, 1990).
Stabilization of Global Methane Levels and Further Reductions

Since atmospheric methane is currently increasing at a rate of about 30 to 40 Tg per year,
stabilizing  global methane concentrations  at  current  levels would require  reductions  in
methane emissions of approximately the same amount.  Such a reduction represents about
10 percent of current anthropogenic emissions. This percentage reduction is much less than
the percentage reduction necessary to stabilize the  other major greenhouse gases:  CO2
requires  a  greater than 60 percent reduction; nitrous oxide requires a 70  to 80 percent
reduction; and chlorof luorocarbons require a 70 to 85 percent reduction (IPCC,  1990b).

Because methane has a relatively short atmospheric lifetime as compared to the other major
greenhouse gases, reductions in methane emissions will help to ameliorate global warming
relatively quickly.   Therefore,  methane  reduction strategies offer  an  effective means  of
slowing  global warming in the near term.   Exhibit  1-3 compares the effects on  future
temperature increases of stabilizing methane concentrations versus maintaining CO2 emissions
at 1990 levels.  This exhibit illustrates that stabilizing atmospheric concentrations of methane
                                      Exhibit 1-3
                        CO2 and Methane Reduction Comparison
     Actual
     T*mpťratun
                     Roughly Identical oftocta on actual warming
                         - CO,amlaaiona etaNllzatlon
                         - CH. Concentration ataHllzation
IPCC-BAU


CH4 stabilization
CO2 capped at 1990

CH4andCO,
                  1988
                           2000
                                    2025
                                            2050
                                                     2075
                                                             2100
                                        Your
    Assumas 3° equilibrium warming
    HI IIII Constitutes uncertainty range due to NO.
    Benefits of Methane stabilization where methane emissions are capped at 540 Tg/yr as compared to
  capping CO2 emissions at 1990 levels (and concentrations grow to over 500 ppm by 2100)	
  Source: Hogan et al. 1991

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INTRODUCTION                                                                   1  - 9
will have a virtually identical effect on actual warming as capping C02 emissions at 1990
levels.  The recent evidence that the rate of annual increase in methane emissions is slowing
(Steele et al., 1992) may mean that reductions on the order of 30 to 40 Tg could reduce
concentrations to the extent that they fall below the level of stabilization. This result would
also have large benefits for the global atmosphere.

1.2  Technological Options for Reducing Methane Emissions

Because  methane released by anthropogenic  activities is  generally  a wasted  resource,
opportunities may exist for low cost, if not profitable, emission reductions. Depending on the
source, a  significant portion of the methane currently emitted to the atmosphere can  be
reduced through  the  use of  cost-effective technologies.    In this  volume, Volume  I:
Technological Options for Reducing Methane Emissions, the key options for reducing methane
emissions from the  major sources are identified and characterized.  An overview of the
emissions from  each major source is provided  below.  Estimates of global emissions  from
these sources are provided in Exhibit 1-4.
Exhibit 1-4
Global Methane Emissions from Major Sources
Source
Coal Mining, Natural Gas & Petroleum Industry
Ruminant Livestock
Livestock Manure
Landfills
Wastewater
Biomass Burning
Rice Cultivation
Estimated Emissions -
70-
65 -
10
20
20
20
20 -
Source: IPCC 1992a
a. Emissions from Livestock Manure reflect revised estimates. Emissions for all other
being updated by USEPA (1993a).
120
100
20a
- 70
- 25
-80
150
sources
1990(Tg)







are currently
Oil and Natural Gas Systems

Methane is the primary component of natural gas, and  significant methane emissions can
occur during  all the major  phases of  the natural gas  system  operations:  production,
processing, storage, transmission, and distribution. Emissions result from normal operations
(including  compressor exhaust emissions, emissions from pneumatic devices and fugitive
emissions); during routine maintenance (including equipment blowdown and venting, well
workovers and scraper operations); and during system upsets when methane is emitted due

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1-10                                                                    INTRODUCTION
to sudden, unplanned pressure changes or mishaps. Because natural gas is often found in
conjunction with oil, gas leakage during oil exploration and production is also a source of
emissions. Current global emissions from oil and gas systems are estimated to be 33 to 68
Tg  per  year.15   Reducing  these  emissions would  not  only  decrease atmospheric
concentrations of methane, but would improve safety, increase productivity through reduced
losses, and improve local and regional air quality.
Coal Mining

Methane and coal are formed together during coalification, a process in which vegetation is
converted into coal by biological and geological forces.  Methane is stored within coal seams
and surrounding rock strata and is released to the atmosphere during mining or through natural
erosion.   In  underground  mines, methane is  hazardous because  it is explosive in low
concentrations (5 to 15 percent) when mixed with air.  Therefore, underground mines use
ventilation and degasification systems to remove methane from mine workings; this methane
is usually vented to the atmosphere.  In surface mines, methane is emitted directly to the
atmosphere as the rock strata overlying the coal seam are removed. The amount of methane
released from a mine depends mainly upon the type of coal and the depth of the coal seam.
For example, deeper coal can  hold more methane.  This means that emissions from coal
mining are likely to increase in the future as shallower reserves are depleted, and deeper coal
is mined.   Current global coal  mine emissions are estimated  to be 23  to  47 Tg per year
(USEPA,  1993a). Recovering  and  utilizing low to high quality methane from gassy mines
would improve mine safety and productivity.
Landfills

Methane is generated in landfills as a direct result of the natural decomposition of solid waste,
primarily under anaerobic conditions (in the absence of oxygen).  The organic component of
landfilled waste is broken down by bacteria in a complex biological process that produces
methane, carbon dioxide, and other trace gases. Global emissions are estimated to be 20 to
70 Tg per year.  Emission reductions,  as well as improved water and air quality, would be
achieved through efforts to reduce methane emissions from this source.
Ruminant Livestock

Ruminant animals (cattle, sheep, buffalo, goats, and camels) produce significant quantities of
methane as part of their normal digestive processes.  Ruminant animals are characterized by
a large "fore-stomach" or rumen, in which microbial fermentation converts feed into products
that can be digested and utilized by the animal. The microbial fermentation enables ruminant
animals to utilize coarse forages that monogastric animals, including humans, cannot digest.
Methane is produced by rumen  methanogenic  bacteria  as a byproduct of normal rumen
fermentation, and then is exhaled or eructated by  the animal.   The amount of methane
   15
       Of this total, 22 to 52 Tg per year are estimated from natural gas systems worldwide, and 11 to 16 Tg
       per year are estimated from oil systems (including associated gas production).

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INTRODUCTION                                                                   1-11
produced is dependent upon both animal type and management practices. Global emissions
are estimated to be 65 to 100 Tg per year.  Options for reducing these emissions will also
increase animal productivity and animal nutrition.
Livestock Manure

Methane can be produced during the anaerobic decomposition of the organic material in
livestock manure. Many developed countries manage the wastes from large concentrations
of cattle, swine, and poultry, using liquid waste management systems that are conducive to
anaerobic  fermentation of the wastes and methane  production.   Global emissions from
livestock manure are estimated to be 20 to 30 Tg per year.  Recovering these emissions for
use as an energy source will also improve environmental and economic conditions at these
farms.
1.3   Methane  Reduction Options in Countries  of Interest

In many cases, a few countries account for most of the emissions from the major methane
sources.  For example, three countries contribute over 70 percent of emissions from global
coal mining activities. Four countries contribute over 80 percent of global emissions from the
production and transportation of natural gas. In some cases, however, such as with ruminant
livestock, methane emissions are fairly evenly distributed worldwide. No  individual country
is responsible for more than 10 to 15 percent of global emissions from this source.  In these
cases, countries discussed in Volume II were selected primarily according to the feasibility of
achieving reductions, or because these countries are representative of regions of interest.

While a variety of emission reduction technologies are available for each major anthropogenic
methane source --  oil and gas systems,  coal mining, landfills, domesticated  animals, and
livestock manure -- these technologies have not yet been fully implemented in many countries.
In many cases, existing  financial, political, and informational barriers  constrain  the wider
application  of these technologies.  Volume  II:  International  Opportunities  for Reducing
Methane Emissions focuses on the most important barriers constraining the development of
methane  reduction programs and outlines possible  actions that  could be undertaken  to
encourage greater methane recovery and utilization.
1.4  Overview of  Report

This report is organized as follows:

Volume  I: Technological  Options for Reducing Methane Emissions:  This volume presents
technical assessments of the principal methane recovery and utilization technologies available
for each of the major sources.  The report has separate chapters dealing with technologies to
reduce methane from the  following sources:

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1-12                                                                   INTRODUCTION


   •  Landfills;

   •  Oil and Natural Gas Systems;

   •  Coal Mining;

   •  Combustion: Mobile and Stationary Sources;

   •  Ruminant Livestock;

   •  Livestock Manure;

   •  Wastewater Management;

   •  Biomass Burning; and,

   •  Rice Cultivation.
For each methane source, the available technologies for reducing emissions are described,
including technical characteristics, costs, availability, applicability, barriers to implementation,
and additional benefits of implementation.  These categories were created  by the IPCC
Response Strategies Working Group,  and the information contained in  this volume is a
compilation of submissions by IPCC member countries. These technical assessments have
been reviewed by government officials and experts in these countries.

Volume II:  International Opportunities for Reducing Methane  Emissions:   This report
summarizes the particular conditions of key emitting countries, in terms of the most promising
options for reducing emissions, the possible emission reductions, and the types of technology
transfer programs which  may increase the implementation of the cost-effective  emissions
reduction technologies. The chapters in this report focus on:

   •   Landfills;

   •   Oil and  Natural Gas Systems;

   •   Coal Mining;

   •   Ruminant Livestock; and,

   •   Other Sources (including Livestock Manure, Wastewater Treatment,  Biornass Burning,
       Fossil Fuel Combustion,  and Rice Cultivation.

For each of these sources, the overall emission reduction potential is discussed and case
studies of the  key international sources are presented.

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INTRODUCTION                                                                  1-13
1.5  References

Cicerone,  R.J.  and R.S. Oremland  (1988),  "Biogeochemical  Aspects of Atmospheric
Methane," in Global Bioqeochemical Cycles, vol.  2, p. 299-327.

Crutzen, P.J. (1991), "Methane's Sinks and Sources" in Nature No. 350 April, 1991.

Hogan, K. B., J.S.  Hoffman, and A.M. Thompson (1991),  "Methane  on the Greenhouse
Agenda," in Nature No. 354 November 21, 1991 pp. 181-182.

IPCC (Intergovernmental  Panel on  Climate Change) (1990a),  Climate Change: The IPCC
Scientific Assessment. Report prepared for Intergovernmental Panel on Climate Change by
Working Group 1, eds. J.T. Houghton, G. J. Jenkins and J.J. Ephraums, Meteorological Office,
Bracknell, United Kingdom.

IPCC (1990b),  Methane Emissions  and Opportunities for Control, Workshop Results of the
Intergovernmental Panel  on  Climate Change (IPCC) Response Strategies Working  Group.
September, 1990.

IPCC (1992a), Climate Change  1992:  The Supplementary Report to the IPCC Scientific
Assessment, report prepared for  the Intergovernmental Panel on  Climate Change, eds. J.T.
Houghton, B.A. Callander and S.K.  Varney, Great Britain: Cambridge University Press.

IPPC (1992b). Technological Options for Reducing  Methane Emissions: Background Document
of the Response Strategies Working Group, prepared by the U.S./Japan Working Group on
Methane [Draft - January, 1992]

Lashof, D. (1989), "The Dynamic  greenhouse: Feedback processes that may influence future
concentrations of atmospheric trace gases and climate change,"  in Climate Change No. 14
pp. 213-242. As cited in IPCC, 1990.

Oak Ridge National  Laboratory/The Carbon Dioxide  Information Analysis Center  (1990),
Trends '90, U.S. Department of  Energy, Atmospheric and Climate Research Division.  Oak
Ridge, Tennessee.

Oak Ridge National  Laboratory/The Carbon Dioxide  Information Analysis Center  (1992),
Trends '91, U.S. Department of  Energy, Atmospheric and Climate Research Division.  Oak
Ridge, Tennessee.

Prinn, R., D. Cunnold, R. Rasmussen, P. Simmonds, F. Alyea, A. Crawford, P. Fraser, and R.
Rosen (1987),   "Atmospheric trends in methylchloroform and the global average  for the
hydroxyl radical,"  in Science No. 238 pp. 945-950. As cited in  IPCC, 1990a.

Rinsland, C.P.,  J.S. Levine, and T.  Miles (1985),   "Concentration of methane in  the
troposphere deduced from 1951 infrared solar spectra," in Nature No. 330 pp. 245-249. As
cited in IPCC, 1990a.

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1-14                                                                  INTRODUCTION
Steele, L.P., E.J. Dlugokencky, P.M. Lang, P.P. Tans, R.C. Martin, and K.A. Masarie (1992),
"Slowing Down of the Global Accumulation of Atmospheric Methane During the  1980's,"
Nature, vol. 358, July 23, 1992, pp 313-316.

USEPA  (United States Environmental  Protection Agency)  (1989),   Policy  Options  for
Stabilizing Global Climate. Report to Congress,  eds. Daniel A. Lashof and Dennis A. Tirpak,
Office of Policy, Planning, and Evaluation (OPPE). Washington, D.C.

USEPA (1993a),  Global Anthropogenic  Emissions of Methane, (in progress), USEPA/OPPE
(Office of Policy,  Planning and Evaluation),  Washington, D.C.

USEPA (1993b), Opportunities to Reduce Methane Emissions in the U.S., Report to Congress
(review draft), USEPA/OAR (Office of Air and Radiation), Washington, D.C.

Vaghjiani, G.L. and A.R. Ravishankara (1991),  "New Measurement of the Rate Coefficient
for the Reaction of OH with Methane" in Nature, April 4, 1991  pp. 406-409.

WMO (World Meteorological Organization)  (1990),  Scientific Assessment of Stratospheric
Ozone:  1989. World  Meteorological Organization Global  Ozone Research and Monitoring
Project - Report No. 20.  Geneva,  Switzerland.

Wuebbles, D.J. and J.S. Tamaresis (1992), "The Role of Methane in the Global Environment,"
paper prepared for submittal to the NATO Advanced Research Workshop, NATO-ASI Book:
Atmospheric Methane, Lawrence Livermore National Laboratory, March 19, 1992.

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CHAPTER Two
LANDFILLS
2.1   Background

Methane Generation and Emissions

Methane is generated in landfills as a direct result of the natural decomposition of solid waste.
The organic component of landfilled waste is broken down by bacteria in a complex biological
process, which produces mainly CH4 (methane), C02 (carbon dioxide), and trace gases such
as  hydrogen  sulfide.   The methanogenic (methane-producing)  stage of this  process  is
anaerobic (lacking free oxygen), and occurs where there is sufficient organic matter which is
isolated from air infiltration.

The quantity and rate of methane generation in landfills depend upon many factors, including
the following:

    •   Waste composition.  Methane is produced from the organic component of the waste;
       therefore a larger organic component increases the potential methane generation.

    •   Moisture content.  Moisture content is critical for anaerobic decomposition as water
       provides the medium for nutrient and bacteria distribution.

    •   Acidity.  Living systems are sensitive to pH (a measure of acidity); optimal ranges are
       from 6.8 to 7.2, but methane production can occur between 6.5 and 8.0 (Pacey and
       DeGier, 1986).

    •   Temperature.  Methanogenic bacteria, of which there are many different species, are
       affected by temperature; the rate of methane production is maximized between 50 and
       60 C (120-140  F), but can occur anywhere from 10 to 60 °C (50-140  FMPacey and
       DeGier, 1986).

In addition, the refuse density and consistency,  the landfill design, and other site specific
factors can affect the quantity and rate  of methane generation.

The majority of gas generated at landfills migrates vertically or laterally until an opening  is
reached and the gas can be released into the atmosphere. Through this migration, the landfill
gas presents an explosive hazard.   In  addition, landfill gas  contains hazardous  and/or
malodorous gases (e.g., volatile organic compounds  -  VOCs) that can contribute to air
quality problems in the vicinity of landfills. These problems can  be reduced if the landfill gas
is recovered or gas generation is limited.

Because the waste composition, moisture content, temperature, pH, and other characteristics
of landfills vary, the rate and  quantity of methane generation vary from landfill to landfill.
Measured landfill gas generation rates have ranged from 0.03 to 1.1 ft3/lb/yr in industrialized
countries (0.002-0.07 m3/kg/yr) (Maxwell, 1990). Gas  generation in developing countries
may be either higher or lower,  depending on the extent to which  air is limited from infiltrating

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2 - 2	LANDFILLS


the waste or what portion of the waste is organic, among other factors. Promising research
is underway to improve both measurement and control of methane production.


Methane Recovery. Utilization, and Reduction

There are several  options for  achieving methane emissions reductions.  One option is to
recover the landfill gas by drilling wells into the landfill and applying vacuum pressure to pull
gas from the landfill.  The recovered gas can then be used as a fuel.  Alternatively, landfills
can be designed to prevent (or reduce the extent of) anaerobic conditions by encouraging the
influx of air and reducing the activity of the methanogenic bacteria.  Methane emissions from
landfills may also be reduced by controlling the amount of organic waste entering the landfill,
through source reduction programs or waste incineration.

The  strategies presented here  to reduce methane emissions from  landfills include the
following:

   • Methane Recovery and Utilization
       - Electricity Generation and Co-Generation
       - Natural Gas Supply
       - Flaring
   • Aerobic Landfill Management
   • Reduced Landfilling of Waste

These strategies are briefly discussed  below.

   Methane Recovery and  Utilization:   Recovering gas from  landfills reduces methane
   emissions, while allowing the energy  value of the recovered methane to be put to a
   profitable use.  Recovery efficiencies (the portion of the gas recovered relative to the gas
   generated) typically range from 50 to 85 percent, with some projects achieving almost
   complete recovery. Technologies for the recovery of methane from landfills are relatively
   straightforward:  gas wells are  drilled  into sealed areas of the landfill and  the gas is
   collected under negative pressure through  a  series of collection  header pipes.  After
   recovery, the landfill gas  must be processed in a  manner  suitable for the intended
   utilization.   Experience in the U.S.  has indicated that gas utilization may be an attractive
   option at landfills with over one million tons of refuse in place (Maxwell, 1 990).  Options
   for utilizing the recovered landfill gas include the following:

   •   Electricity Generation and Co-Generation.  The recovered  methane can be used to
       power an electricity generator, and the electricity used  at nearby sites or sold to a local
       electricity supply system.  In some cases the recovered gas can be used as part of a
       co-generation system, where the waste heat from the prime mover (i.e.,  the engine)
       is used to meet local heating requirements, thereby increasing the overall efficiency of
       the system. Electricity generation requires relatively large amounts of landfill gas, and
       is therefore suitable for larger landfills.  Economic viability depends primarily on the
       price at which the electricity can be sold.  Historically, 50 percent of landfill energy
       projects worldwide have been for electricity generation (K.M. Richards, 1989).

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LANDFILLS                                                                         2 - 3
   •   Natural Gas Supply.  Recovered landfill gas can be used directly as a fuel in several
       ways. Medium quality gas (e.g., 30 to 70 percent CH4) can be used by local industries
       after minimal processing, or sold directly to a gas supply system that handles medium
       quality gas. Industrial uses include a variety of heating and  process needs, with the
       end use determining the degree of gas processing  required to remove impurities and
       corrosives from the landfill gas. Alternatively, if the gas is delivered to a natural gas
       utility it  usually must be processed extensively to yield high  or "pipeline quality" gas
       (> 95 percent methane, with minimal  impurities).

   •   Flaring.  Flaring is the simplest method of reducing methane emissions.  The recovered
       landfill gas, without treatment  or processing, is burned in a combustor.  Destruction
       efficiency (of all hydrocarbons in the gas) of over 98 percent can be achieved.  Initial
       capital requirements for flares are small relative to energy recovery strategies and the
       technology is simple, but the energy value of the methane is wasted and subsequent
       revenues are  forfeited.   Nevertheless, flaring may be an  appropriate method for
       controlling emissions  at  smaller  landfills  where gas  flows will  not support an
       economically viable project, or  as an interim strategy while end uses are developed.

   Aerobic Landfill Management: The design of landfills to encourage aerobic conditions has
   been an effective method of reducing  methane  emissions in  Japan and  other  Asian
   countries. Although this strategy does not recover methane for use as an energy source,
   aerobic designs increase the rate of decomposition, reduce the emissions of harmful and
   odorous gases, and improve the quality of leachate. These advantages are significant in
   terms of pollution reduction and the reclamation of landfill sites.  Emissions reductions of
   over 50 percent have been achieved with commercially available designs.  More advanced
   aerobic landfill designs that are still being  developed have  achieved methane reductions
   of over 80 percent in test applications (JEA, 1991).

   Reduced Landfilling of Waste: For given landfill designs and operating conditions, methane
   emissions are determined  by the quantity of organic material in the landfill. Methods for
   reducing the quantity of landfilled  organic waste, thereby  reducing methane emissions,
   include recycling, composting, and incineration.

Exhibit 2-1 summarizes these three strategies. The strategies are described below in detailed
technical assessments.  Each technical assessment consists of the  following sections:

   • Reduction/Utilization Technology Description
   • Costs
   • Availability
   • Applicability
   • Barriers; and
   • Benefits.

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LANDFILLS                                                                         2 - 5
2.2   Methane Recovery and Utilization

Landfills result in the anaerobic decomposition of the organic component of landfilled waste.
Recovery  and utilization of this generated methane can greatly reduce the overall methane
emissions associated with  landfills.   Furthermore, because a valuable energy source  is
recovered, this strategy can be profitable in many cases.  This section first discusses landfill
gas recovery and purification technologies, as well as possible means of increasing methane
recovery.  The  options for using the recovered gas are  then discussed separately below.
Recovery Technology Descriptions

Landfill gas recovery is essentially the "mining" of trapped methane: wells are drilled into the
landfill; the gas is withdrawn under negative pressure; and the recovered gas is gathered at
a central processing unit.   Landfill gas recovery systems share  many  basic features and
requirements.

Recovery wells are generally drilled once the landfill or individual landfill cell has been capped
by an impermeable layer.  Gas recovery is most successful at well-sealed landfills (or sealed
cells within a landfill) for two reasons: 1) gas cannot escape, thus recovery efficiencies are
increased;  and 2) oxygen will not infiltrate the landfill, where it would kill the methanogenic
bacteria. A thick layer of soil is sufficient to seal a landfill, although the exact thickness of
this layer depends on the soil type and climate. Landfills using sandy, dry soil, which is more
permeable  to gas, require a thicker layer.

The number of wells drilled in a particular landfill depends upon certain characteristics of the
landfill and its contents. Typically, 1 to 6 wells per hectare are installed.  If the landfill is deep
and well-sealed, the wells can be spaced further apart because  a greater vacuum can be
applied without causing the inflow  of air.  Denser, less permeable refuse will require  more
closely spaced wells (Mahin, 1988).

Recovery wells consist of a number  of components.  Well shafts, typically 1 to 3 feet (30-90
cm) in  diameter, are drilled from the surface to within a few feet of the bottom of the landfill.
A narrow,  perforated plastic pipe is then inserted into the well.  The shaft is backfilled with
gravel, or other permeable material; the top is sealed with concrete, or an impermeable block,
to prevent  the inflow of air; and finally the pipehead is connected to the collection system
(Mahin, 1988) (see  Exhibit 2-2).

Gas is collected from the wells  by the gas collection header.  The wells are connected by
horizontal  pipes  on or  just below  the  surface  of the landfill.   Compressors (simple
motor/blower units) create the  negative pressure necessary to gather the gas at a central
collection point. Most collection systems filter out  particulates, and  drain water and other
condensed liquids, to prevent clogging of the system.  Some  facilities also remove corrosive
impurities such as hydrogen sulfide.  (Purification systems required for particular uses of the
landfill gas are described in more detail in the following sections.)

Because  methane control systems are necessary at many sealed landfills, this technology is
currently widely available. The recovery efficiency will vary with the design and operation of

-------
2- 6
LANDFILLS
the system.  Well-designed systems in Europe and the U.S. have achieved almost complete
recovery in some cases, with recovery efficiencies often around 70 to 80 percent (Maxwell,
1990; USEPA,  1993a). The  methane content of recovered gases  ranges from 40 to 60
percent  (Maxwell, 1990; Thorneloe, 1992b).

It is also possible to recover methane from unsealed landfills. In any situation where large
quantities  of waste are dumped, it is likely that anaerobic conditions will exist within the
"landfill,"  and  that methane is  therefore  being generated.  While wells sunk into sealed
landfills  have  better  recovery  rates, less  technologically sophisticated  systems  have
successfully recovered and utilized gas generated from decomposing waste (USEPA, 1993b,
Volume  II; Monteiro, 1992).
                                     Exhibit 2-2
                             Landfill Gas Recovery Well
                                        VALVE
                  SPECIAL BACKFILL
               HEADER PIPE    CONCRETE PLUG
               TO PUMP     SOLID PLASTIC PIPE
                        COMPACTED FILL
                                                           VARIES
                    PERFORATED PLASTIC PIPE


                                   CAP


                         BOTTOM OF TRASH
  Source: Mahin, 1988

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LANDFILLS                                                                       2 - 7
Purification Technologies

Recovered gas is typically a 50:50 mixture of methane and carbon dioxide (a non-combustible
gas), and is therefore a medium quality gas (approximately 500 Btu/cf, 18 MJ/m3) suitable
for numerous energy applications. However, in addition to CH4 and CO2, landfill gas often
contains variable amounts of water, particulates, hydrocarbons, halogen compounds and other
impurities.  These impurities may interfere with  the  operation of recovery and  end  use
equipment. Therefore, after recovery and collection, the gas must be processed and purified
before it is used or sold. In particular, particulates, water and corrosive compounds must be
removed.

   •  Particulates.  Particulates must be removed because they can clog pumps or cause
      excess wear as they move through the gas piping system. Also, particulates can
      accumulate inside engines and reduce engine life.  Filters and water wash scrubbers
      are the two primary methods for removing solids. Filters are  simpler than water wash
      scrubbers,  but because they are a physical barrier they cause a larger pressure drop
      in the system than scrubbers (GRCDA, 1990).

   •  Water. Large quantities of drainage water can be removed with trap mechanisms at
      the well head. However, landfill gas also contains significant amounts of water vapor
      which  must be reduced before the gas is used in an engine or turbine.  Several vapor
      removal  methods are available, including  direct chilling,  glycol treatment, and dry
      desiccants (Thorneloe,  1992; GRCDA, 1990).  Direct chilling of the gas will cause
      water vapor (and often heavy hydrocarbons) to  condense out as a liquid.  Glycol and
      dry desiccants (e.g. silica gel and activated alumina) work because they have a greater
      affinity for  water than the gas; water is removed from the moist gas when a desiccant
      and a gas are placed in contact. However,  desiccants must either  be regenerated or
      replaced when they become saturated.  For example, glycol is frequently separated
      from water by distillation, and some dry desiccants can be regenerated by heating
      (evaporation).  Chilling can typically remove 80 to 95 percent of the water  and
      contaminants down to a dew point of  1 °C (34°F). Glycol and dry desiccants can
      almost completely remove any water; typical systems can achieve  a dew point of as
      low  as -14°C  (6°F) (GRCDA, 1990).  These techniques  can also  be combined,
      depending  upon the requirements for gas end use.

   •  Corrosive Compounds.  Trace gases can react chemically with engine parts, pipeline
      components, and desiccants, causing corrosion  and therefore increased maintenance
      and replacement costs.  In particular, sulfur compounds (e.g.  H2S) will result in the
      formation of sulfuric acid and sulfur oxides. Halogenated hydrocarbons can form acids
      (HCI, HF), and possibly dioxins. Sulphur compounds can be removed with impregnated
      (activated) carbon  filters,  or absorption onto iron  oxide.   Some hydrocarbons are
      removed in the chilling process used to remove water; others are  removed using
      carbon filters, or through  the use of selective  physical solvents (i.e., no chemical
      reaction is  involved in the removal of the contaminant) (GRCDA, 1990).  The degree
      of purification, and thus the cost of the purification system, must be balanced against
      the cost of any corrosive damage that may occur; at some point it becomes more cost-
      effective to increase the maintenance of end use equipment than to further purify the
      gas.

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2 - 8                                                                         LANDFILLS
Methane Generation Improvement Techniques

Increasing methane generation can improve the profitability of recovery projects. There are
technologies available that increase the quantity of gas generated and recovered. Although
more research is necessary to identify the factors that influence methane generation and to
understand their effect, the role of several key factors has been examined.  For example,
keeping the moisture content high increases decomposition as long as the field capacity (the
point at which water begins to drain through the landfill) is not exceeded (Pacey and DeGier,
1986).  Recirculating leachate liquid both maintains water content and acts to control the pH
of the landfill.  Shredding waste to create a smaller particle size increases the relative surface
area on which bacterial activity  may occur, thereby increasing the rate  of decomposition.
Techniques for initiating methanogenic bacterial activity have been developed, including the
application of previously digested solids or sewage sludge to provide bacteria for the landfill
and removal of oxygen from the landfill through nitrogen purges (Pacey and DeGier,  1986;
Kinman et al., 1987).
Utilization Technology Descriptions

There are three types of end use options for the medium quality gas typically recovered from
landfills.  First, recovered landfill gas can be used to generate electricity on-site or at a nearby
power plant, using internal combustion engines, gas turbines, or emerging technologies such
as fuel cells. Second, landfill gas can be used directly as a fuel source without conversion to
electricity.  Landfill gas can  be sold  with little or no processing as a medium quality gas for
local industrial, residential or commercial heating and energy needs.  Alternatively, landfill gas
can be processed into high quality gas and  sold to natural gas supply systems. Third, landfill
gas can be flared where there is insufficient gas to justify an energy project, or as an initial
step before implementing utilization options.

The following  utilization options are discussed  below:

   • Electricity Generation and  Co-Generation
   • Natural Gas Supply
   • Flaring
   Electricity  Generation  and Co-Generation  Technologies:   There are several available
   technologies for generating electricity from landfill gas. Internal combustion engines (ICs)
   and  gas turbines are the most commonly used prime  movers for landfill  gas energy
   recovery projects, with efficiencies of approximately 25 to 30 percent.  Cogeneration, the
   additional use  of waste heat for local uses, can result in overall efficiencies exceeding 80
   percent and improved economics (Williams and Larson, 1 990).  Other technologies such
   as fuel cells are being explored for use with landfill gas, and may be commercially available
   in the near term.  Fuel  cells achieve conversion efficiencies of around  40 to  60  percent,
   and close to 90 percent when combined  with heat recovery (Woo, 1990).

   The anticipated landfill gas flow rate is particularly important in choosing an appropriate
   prime mover to generate electricity. An approximate guideline is that 0.65 m3 of landfill
   gas per hour (23 ft3/hour) is required for  every kW of generating capacity, although this

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LANDFILLS                                                                         2 - 9


   figure  will vary with operating efficiency, rated  capacity, and  gas quality.16   Gas
   turbines are typically available in sizes from 500 kW to 10 MW, corresponding to 300 to
   7000 m3/h. Internal combustion engines are available in smaller sizes, e.g.  30 to 2000
   kW. It is more common to expand capacity with multiple units rated at several hundred
   kW to several MW than to install a single large turbine or 1C engine (because of the greater
   flexibility of modular expansion).

   •   Internal Combustion  Engines.  Internal combustion engines are stationary engines,
       similar to conventional automobile engines, that  can  use medium  quality gas to
       generate electricity. While they can range from 30 to 2000 kilowatts (kW), 1C engines
       associated with  landfills typically have capacities of several  hundred kW.  1C engines
       are a  proven and cost-effective technology.  Their flexibility,  especially for small
       generating capacities, makes them the only option  for smaller landfills.

       1C engines have  proven to be reliable and effective generating devices.  However, the
       use of landfill gas in 1C engines can  cause corrosion due to the impurities in landfill gas
       (Thorneloe, 1992). Impurities  may include  halogenated compounds  that  can react
       chemically under the  extreme heat and pressure of  an 1C  engine.  Experience has
       shown that adequate gas processing and regular engine maintenance can successfully
       overcome this problem (Thorneloe, 1 992; GRCDA, 1990). In addition, 1C engines are
       relatively inflexible with regard to the ainfuel ratio,  which fluctuates with landfill gas
       quality. Some 1C engines also  produce significant  NOX emissions, although designs
       exist to reduce NOX emissions.

   •   Gas Turbines.  Gas turbines can use medium  quality gas to generate power for sale to
       nearby users or electricity supply companies, or for on-site use. Gas turbines typically
       require higher gas flows  than 1C engines in order to be economically  attractive, and
       have therefore been used at larger landfills; they are available in sizes from 500 kW to
       10  MW, but are  most useful  for landfills when they  are 2 to 4 MW (Anderson, 1991).
       Where adequate gas volumes are available, gas turbines have several advantages over
       1C engines.  Gas turbines have a continuous combustion process and are therefore
       much better at coping with fluctuating heat values. Also, gas turbines are constructed
       from high-temperature alloys that are much more resistant to corrosion. Gas turbines
       also emit less NOX.

   •   Cogeneration/Combined Cycle.  Cogeneration and combined cycle systems can greatly
       increase efficiencies and improve the attractiveness of gas utilization. In cogeneration,
       waste heat from various stages of the  gas combustion system is recovered and used
       for on-site or other local heating  needs. Combined cycle systems use recovered waste
       heat from the prime mover to produce  steam, which is in turn used to power a steam
       turbine and generate electricity. Cogeneration can be carried out in a combined cycle
       system (see Exhibit 2-3). Without cogeneration, both turbines and 1C engines have
       efficiencies in the region  of 30 percent.  The remainder  of the energy  content of the
       fuel (i.e., landfill gas) is typically unutilized, and escapes as heat.  Cogeneration  and
       combined cycle  systems can raise overall process efficiency to above  80 percent
       (Williams and Larson, 1990), and are proven  and cost-effective utilization options for
   16  A gas flow rate of 0.65 m3/hr assumes medium quality gas (20 MJ/m3) and a system efficiency of 28%.

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2-10                                                                      LANDFILLS
      landfill gas (GAA, 1992). They have been used successfully in a number of countries
      around the world (Gendebien, 1992).
                                     Exhibit 2-3
                          Co-generation with a Gas Turbine
   •   Fuel Cells. Fuel cells are similar to batteries, in that they convert chemical energy into
       usable energy such as electricity and heat.  Most fuel cells have three subsystems: a
       fuel processor, in which gas reacts with steam to  produce  hydrogen and carbon
       monoxide; a power section, which electrochemically consumes the hydrogen from the
       gas and the oxygen  from the process air system,  producing  direct current (DC)
       electricity; and a power conditioner, which converts the unregulated DC output power
       into regulated AC power if DC cannot be utilized directly.

       Fuel cells have several advantages as electricity generators. Most fuel cells achieve
       fuel-to-electricity conversion efficiencies of 40 to  60 percent, and can approach
       efficiencies of 90 percent if waste heat is used in cogeneration schemes (Thorneloe
       and Spiegel,  1990).  In addition, their small labor requirements  and modular design
       make fuel cells a promising option for small landfills.  However, the use of fuel cells
       to date has been limited by their costs, which are estimated at $2500/kW for turn-key
       operations; prices should become competitive in the future with technological  and
       manufacturing advances.  Fuel cells have not been demonstrated with landfill gas,
       although such a demonstration should be completed over the next several years by the
       USEPA's  Office of Research and Development (Thorneloe, 1992b).  A recent study
       concluded that about 750 landfills in the U.S. have sufficient gas potential to utilize
       2 MW fuel cells,  with a total generating capacity of 6000 MW (EPRI, 1992).

   Natural Gas Supply:  As an alternative to electricity generation, medium quality landfill gas
   can be used directly for other energy applications. In addition, landfill gas can be enriched
   by removing  the carbon dioxide along with other impurities, and sold as high quality gas.
   Depending upon gas prices and purification costs, revenues from sales can make these
   projects feasible.

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LANDFILLS                                                                       2-11
   •  Medium Quality Gas Use. Landfill gas can be used to supplement existing fuel supplies
      for firing boilers, space heating, and a variety of other uses in industrial, commercial
      and residential applications. Landfill gas can also be co-fired with other fuels. Medium
      quality gas can often be economically transported via pipeline if the user is near the
      landfill (i.e., within several miles) (Thorneloe, 1992b). The degree of processing will
      depend on the requirements of the end user, with typical applications needing only a
      minimum of purification. In some cases, pipeline systems accept medium quality gas.

   •  High Quality Gas Use.  To use landfill gas for high quality gas uses it is necessary to
      remove most of the carbon dioxide and trace impurities.  This is a more difficult and
      hence more expensive process than removing  other contaminants.  Technologies
      include pressure swing adsorption with carbon molecular sieves, amine scrubbing, and
      membranes (USEPA, 1991).

   Flaring: Flaring landfill gas is a strategy that simply and effectively reduces emissions from
   landfills.  This strategy can reduce safety hazards and environmental problems using low
   cost technology. However, flaring landfill gas eliminates the potential to generate revenue,
   as the energy value of the methane is wasted.  Nevertheless, flaring may be the optimal
   control strategy for small landfills or those with minimal emissions.

   Flaring is simply the combustion  of the recovered landfill gas. The gas will readily form
   a combustible mixture with air, and requires only an ignition source to ensure combustion.
   Flares are usually designed for gas flows of around 8 to 20 m3 per minute (300-700 cubic
   feet per minute), and can handle as much as 100 m3 per minute or more. The flame can
   burn openly or can be enclosed.

   •  Open Flame Combustors. Open flame combustors (e.g., candle or pipe flares) are the
      simplest flaring technology. They consist of a pipe through which the gas is pumped,
      a  pilot light  to spark the gas, and some means of regulating the gas flow.  Possible
      complications include unstable flames  leading to inefficient combustion, aesthetic
      complaints, and the difficulty of testing emissions from open flames. Some open flame
      combustors are covered,  both hiding the flame from  view and allowing relatively
      accurate monitoring for low flow rates.  However, this does not increase control over
      the flame.

   •  Enclosed Combustors. Enclosed combustors successfully overcome all of the problems
      associated with open flame combustors.  Because the air flow can be adjusted, the
      combustion is more reliable  and more efficient. As a result, unburned hydrocarbon and
      hazardous material emissions are reduced.  Furthermore, because the combustor has
      an exhaust flue, emissions testing is  simpler  and more accurate.  The flame  is
      completely hidden from view.
Costs

Costs  of  using  landfill gas  are  highly dependent on  the specific technologies used.
Nevertheless, the  costs  for  all uses include three major  components:  recovery  costs;
purification costs; and costs for the electricity generation or gas supply equipment.

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2-12                                                                       LANDFILLS
   Recovery  Costs:  Installation costs for gas recovery systems are typically $5,000 to
   $10,000 per acre (Maxwell, 1990; Anderson, personal communication; USEPA, 1991).
   These capital costs include surveying, drilling wells, and  construction of the  surface
   collection  system.  Operating costs of the recovery system  will  vary greatly with the
   complexity and scope of the system. A hypothetical landfill, with capital costs of  roughly
   $1 million, is estimated to have annual operating costs of $83,000 to $94,000 (USEPA,
   1991).

   Gas Purification Costs: Purification costs for use in  an  1C engine or turbine will largely
   depend upon the required pressure of the gas.  Costs will be lowest for low-pressure 1C
   engines (5 psi), higher for high-pressure engines (45  psi), and greatest for gas turbines,
   which require around 160 psi.  For typical flow rates of several hundred  cubic feet per
   minute (e.g., 100-200 kW generating capacity), costs will range  from  $50,000 to
   $300,000 for a system removing liquids and particulates (GRCDA,  1 990).  Costs  will rise
   significantly if other impurities must be removed. As indicated above, these costs must
   be balanced against  the  associated  reduction in  engine  maintenance  costs.   Gas
   enrichment (carbon dioxide removal) processes range from $0.60 to $2.00 per MMcf
   (Soot, 1991b).

   Electricity Generation Equipment Costs: End use equipment for generating electricity from
   recovered landfill gas must include sufficient gas purification systems, a prime mover, a
   generator, and auxiliary equipment such as engine controls and gas  monitors.  Capital
   costs  for  these components vary widely depending on the  gas  flow, the generating
   capacity, the type of prime mover,  as well as other factors such as gas quality and system
   specific criteria.

   Prime mover capital costs are typically a large portion of total costs. 1C engines, exclusive
   of other cost components, are estimated to be $350 to $500 per kW (Anderson, personal
   communication; Soot,  1991 a).  Operation and maintenance costs are  estimated at up to
   20/kWh.  Capital costs for gas turbines, for a 6 MW system, are estimated to be $700/kW
   (Sturgill, 1991).  Operation  and maintenance costs are estimated at 0.60/kWh.

   Typical capital and operating costs for "turn-key"  gas-to-electricity engine-generator
   equipment operated in the  U.S. are summarized in  Exhibit 2-4.  These  costs  include
   necessary gas purification  and compression,  prime  mover, generator  equipment, site
   preparation and auxiliary equipment. Low-pressure 1C engine-generator packages range
   from $1,100 to $1,700  per kW.  A high-pressure 1C package, which requires gas
   compression, costs $2,000 per kW (Anderson,  personal communication).

   Gas Supply Costs:  The supply of landfill gas typically involves existing end-use facilities.
   Therefore, the significant costs for  this option are for the construction of a gas distribution
   pipeline, gas blower, and gas purification equipment.  Landfill gas supply  pipelines (and
   requisite gas blowers), which might typically be 10 to 1 5 inches in diameter, and  operate
   at 10 to 15  pounds per square inch of pressure, have construction costs ranging from
   $200,000 to $300,000 per mile  (Thorneloe, 1992a).  These costs depend on  several
   related factors, including the distance to the user, gas flow, pipeline diameter and material,
   blower capacity, and the terrain over which  the pipeline is laid.  Gas supply for these
   applications  is likely to be competitive  for users within several miles of the  facility
   (Thorneloe, 1992b).

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LANDFILLS
2 - 13
Exhibit 2-4
Capital and Operations Costs for Gas-to-Electricity Projects
Engine Type
1 1C Engine;
Low Pressure
2 1C Engines;
Low Pressure
2 1C Engines;
High Pressure
1 Turbine
Initial Capital
(xlOOO)
$1,300
$1,700
$3,600
$4,600
Gas
Consumption
(xlOOO scf/day)
450
900
900
2,000
Net kW
Capacity
770
1540
1460
2700
O & M
in C/kWh
2.1
1.5
1.7
1.1
Source: Anderson, personal communication.
   Flaring: The cost of flares depends on the design and the required gas flow rate.  For a
   typical flow rate of  8 to 20 m3 per minute (300-700 cubic feet per minute), costs  range
   from  $15,000 for  an  open-flame combustor  to  $90,000 for  enclosed combustors
   (Anderson, personal communication;  USEPA, 1991).

Availability

Most technologies  for landfill  gas  recovery  and use are  widely  available.   Emerging
technologies, such as fuel cells, are expected to become available or commercially feasible in
the near future.

   Recovery  and Purification Equipment:   The recovery of landfill gas  and subsequent
   processing for the supply of medium quality (non-enriched) gas involves technologies that
   are well developed and commercially available. These technologies have been successfully
   demonstrated  in  projects worldwide, under a  range  of  conditions (USEPA, 1993b).
   Enrichment of landfill gas to high  quality gas, however, depends  on processes that are
   commercially available but currently uneconomic or impractical for use in many landfill gas
   applications. Continuing progress  and experience is expected to improve the feasibility of
   gas enrichment technologies.

   Generating and Gas Supply Equipment: The technologies for using landfill gas to generate
   electricity are  generally well developed,  as are  other off-site uses such as in industrial
   boilers. In addition; gas supply equipment such  as pipe, blowers,  and meters are readily
   available.   The  use of fuel  cells and  other  emerging technologies  requires further
   development and demonstration  before  they become widely available. It is expected,
   however, that  these technologies will be  added to the list of available options by the end
   of the decade.

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2-14                                                                        LANDFILLS
   Flares: Flares are a simple, proven, and commercially available technology. The necessary
   equipment can be manufactured in most countries.
Applicability

The applicability of methane recovery and use depends on the quantity of gas that is being
generated by a landfill and the local demand for gas or generated electricity.  Applicability is
therefore discussed in terms of recovery, end-uses, and flaring.

   Gas Recovery:  Gas recovery has been commercially successful primarily in large sanitary
   landfills (which are covered with a thin layer of soil or clay), where 1) anaerobic conditions
   can be  easily maintained  and 2)  large amounts of methane are  generated.  However,
   anaerobic conditions are also likely to exist in any sufficiently dense or deep landfills, and
   methane recovery does not rely upon  technologically advanced landfill  management.
   Recovery systems are  available in a wide  range  of technical  complexity.   Therefore,
   methane can be recovered from landfill sites under a wide range of conditions, if a suitable
   utilization such as electricity generation or direct use of medium Btu  gas is feasible.

   Electricity Generation and  Gas Supply:  The applicability  of specific end-uses depends
   primarily on the local demand for and price of electricity or gas.  Low energy demand
   reduces project feasibility.  Where sufficient local demand exists, all or a  portion of the
   available landfill gas may  be  utilized; if necessary, the  remaining demand  for gas or
   generated electricity may be met  by other sources.

   The applicability of supplying high quality gas is somewhat different than for medium
   quality gas. Due to the high processing  cost, high quality landfill gas  is competitive only
   where the market price of natural gas supplies is quite  high.

   Flaring:  Recovering and  flaring  gas  is  feasible  for  most landfills, especially where
   emissions of methane and VOCs are a local  environmental or safety problem. Flares are
   relatively simple technologically and require low capital investment. Moreover, flaring can
   often be an initial step before implementing  other utilization options.
Barriers

The primary barrier to landfill gas recovery and use in developed and developing countries is
often artificially low regional energy prices (Thorneloe,  1992).  Conditions governing both
electricity and natural gas  prices, such as government  energy  policies, subsidies, and tax
incentives, can have an important effect on the viability of landfill gas projects. A second
problem, especially  for  developing  countries, is the availability of technical expertise,
equipment, and  other resources.  In particular, there is a need for monitoring equipment to
assess potential gas flow  rates and  qualities, in order to determine viable end  uses for
recovered gas.

Site-specific  barriers  include  the  proximity  to local industrial users, with  the  cost of
transporting the gas becoming prohibitively high as distance increases, and the high cost of
emerging technologies such as enrichment, fuel cells, and  some purification technologies.

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LANDFILLS                                                                       2-15
Flaring does not provide any revenue, and therefore may only be feasible when combined with
other utilization options, or where environmental or safety regulations require that landfill gas
emissions be controlled.
Benefits

In addition to reducing methane emissions into the atmosphere, the recovery and flaring of
landfill gas creates other benefits:

   •   Landfill safety will be improved. Methane poses a serious explosive hazard, especially
       if it migrates beyond the landfill boundaries.  Recovering the methane from a sealed
       landfill can significantly reduce this danger.

   •   Reduced emissions of hazardous materials. Landfill gas contains significant quantities
       of VOCs, in addition to methane. Both methane and VOCs are implicated in urban air
       pollution, and many VOCs are also toxic.  Recovery of landfill gas can reduce these
       emissions.

   •   Reduced odor problems.  Landfills frequently emit gases that cause odor problems.
       Recovery systems reduce these emissions.
                       Methane Recovery and Utilization

                       • methane recovery of 60-90%
                       • clean energy source
                       • improved safety
                       • improved air quality
                       • reduced odor problems
2.3  Aerobic  Landfill Management17

The Japanese have demonstrated that it is possible to suppress the generation of methane
by creating aerobic  or semi-aerobic  landfill  conditions.   Aerobic  landfills  enhance  the
biodegradation of waste in the landfill site, limit the generation of harmful and odorous gases
such as methane and hydrogen sulfide, and prevent groundwater pollution by improving the
quality of leachate from the landfill site. In addition, aerobic landfill sites can be reclaimed for
a variety of land uses more quickly than conventional landfills.
   17  This section is based on information supplied in Japan Environment Agency, 1991.

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2 - 16
                                                                 LANDFILLS
Technology Description

Aerobic options are classified into semi-aerobic, recirculatory semi-aerobic, and fully aerobic
landfill designs.   These designs are characterized  by reduced methane  generation  and
increased decomposition rates.  Studies have shown that total methane emissions from each
of the aerobic landfill designs over a ten year period  are lower than for anaerobic systems.
The semi-aerobic landfill system is commercially available; the re-circulatory system and fully
aerobic system are still in the research and development stage.

   Semi-Aerobic Landfill:  In this system,  air is supplied to the landfill through the leachate
   collection  pipes  and is  diffused through the  landfill layers to maintain semi-aerobic
   conditions.  As  shown in Exhibit 2-5,  the leachate collection pipes are installed at the
   bottom of the landfill site to collect leachate and transport it to the leachate collection pit.
   The  leachate can be drained by pump or natural  flow.  The water level in the pipes is
   monitored to ensure that the pipes are not blocked and that air is able to flow through the
   pipes into the landfill. The pipes have a larger diameter than conventional leachate pipes
   to ensure an adequate supply of air. The amount of methane generated by a semi-aerobic
   system has been shown to be roughly 50 percent less than that generated by an anaerobic
   landfill.
                                     Exhibit 2-5
                                 Semi-Aerobic Landfill
    Runoff Collection Duct
            Cover Soil
                   Solid Wast
                                                      Gate
\
                                                                           Pump Pit
         Impermeable Layer
                    Leachate Collection Pipes

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LANDFILLS
                           2 - 17
   Re-Circulatory Semi-Aerobic Landfill: The re-circulatory semi-aerobic landfill system is an
   improved version of the semi-aerobic system.  The rate of decomposition and purification
   of leachate are faster in this  system than in the semi-aerobic.  As shown in Exhibit 2-6,
   a recirculatory semi-aerobic landfill consists of a leachate recirculation system and the
   leachate collection system of the semi-aerobic process. The collected leachate is returned
   to the landfill site and recirculated to encourage bacterial growth through increased oxygen
   and nutrient  supply. This process enhances decomposition of solid waste in the landfill
   layers, improves leachate quality, stabilizes the landf illed wastes, and reduces the methane
   generation.  Based  on demonstration projects, the methane generated by a re-circulatory
   semi-aerobic system can be  as much as 80 percent less than that generated  by an
   anaerobic landfill.
                                      Exhibit 2-6
                           Recirculatory Semi-Aerobic Landfill
                                                            Cover Soil
                                                            Solid Waste
                 Leachate
                     Facility
Landfill Site
                                  - Leachate
   Aerobic Landfill:  The aerobic landfill system uses an air blower (see Exhibit 2-7) to force
   air into the landfill layers.  The air passes through  pipes which lie slightly  above the
   leachate collection pipes at the bottom of the landfill site.  The system is operated and
   controlled so that the conditions maintained in the landfill site are more aerobic than those
   of a semi-aerobic system. According to demonstration project evaluations, the methane
   generated by an aerobic system can be nearly 90 percent less than that generated by an
   anaerobic landfill.

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2 - 18
                                             LANDFILLS
                                      Exhibit 2-7
                                   Aerobic Landfill
    Runoff Collection Duct
            Cover Soil
                  Solid Waste
Air Supply Pipe
          Air Supply Pipes
                               Leachate Collection Pipes
Costs

Costs for aerobic landfill management vary substantially according to the composition of the
wastes, the size of the landfill site, the amount of precipitation, and the social conditions of
the country concerned. The following costs are typical for landfill sites operated in Japan,
where semi-aerobic landfill techniques are widely used.

Installation costs for semi-aerobic landfill systems are approximately $0.60/ton of landfilled
waste.  Estimated installations costs for an air blowing system for an aerobic landfill system
are approximately $0.50/ton  of landfill  waste and  operating costs are  approximately
$0.40/ton, assuming that the air blower is operational for  15 years.  In  regions with light
rainfall, maintenance and operating costs can be significantly controlled by adopting the semi-
aerobic landfill system with natural leachate drainage and natural aeration.
Availability

The semi-aerobic landfill technology is developed and proven.  It is commercially available and
in use in Japan  and East Asia.  The re-circulatory semi-aerobic and fully  aerobic landfill
systems are in the research and development stage and should be commercially available
around 1995.

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LANDFILLS                                                                        2-19
Applicability

The use of aerobic and semi-aerobic landfill technology may be most appropriate for small-
capacity landfill sites in which methane recovery is not economically feasible.  Aerobic landfill
management is best conducted at landfills designed for this strategy because aerobic systems
require air-feed pipes, or, at a minimum, leachate collection pipes, at the bottom of the landfill
site. It can be extremely difficult to retrofit existing landfills with these pipes. Semi-aerobic
conditions can be achieved in some sites in which leachate collection pipes have already been
installed,  especially  if these pipes are larger than required for  leachate collection, or if
additional measures are instituted to ensure adequate leachate water level control.
Barriers

Barriers to the implementation of these methane reduction strategies can be both economic
and technical.  In the semi-aerobic landfill system, it is necessary to have an  equally dense
arrangement of vertical air ventilation pipes as leachate collection pipes.  Moreover, in cases
where the  landfill is very  deep, maintaining a large  aerobic zone  will require additional
ventilation pipes. Monitoring the operation of these sites is an important component of the
overall system since there is always the potential for methane concentrations  to fall into the
explosive range.

Economic factors will be a  major consideration at large landfill sites, which likely require air
blowers to ensure aerobic conditions.  As the landfill size increases, so will the costs of the
air blower equipment and general operating and maintenance costs, including electric power
costs. Also, in such large-scale  landfill sites, it is difficult to achieve a uniform air supply at
the bottom of the landfill, requiring development of an  improved air-supply system.
Benefits

After making allowances for the cost aspects, the aerobic landfill systems can be classified
in the following order according to relative advantages they offer: the semi-aerobic as most
advantageous, followed by the re-circulatory landfill system, and then the aerobic system.
Aerobic and semi-aerobic landfill systems offer the following advantages as compared with
the anaerobic landfill systems which are currently in general use:

    •  Ability to reduce the pollution load of the leachate;

    •  Reduced formation and generation of hazardous gases such as hydrogen sulfide;

    •  Earlier stabilization of the landfill site;

    •  Prevention of groundwater pollution; and,

    •  Lower cost of leachate control than in anaerobic sites.

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2 - 20                                                                      LANDFILLS
                       Aerobic Landfill Management

                       • proven methane reductions of 50%
                       • improved pollution control
                       • earlier stabilization
                       • technology currently available
                        (semi-aerobic)
2.4  Reduced Landfiliing of Waste

Changes in human lifestyle resulting in rising per capita waste generation,  and continued
population growth, steadily increase the total amount of waste that is generated worldwide
each year. The proper disposal of this solid waste is an important environmental and human
health issue in both developed and developing countries.   The majority of solid waste is
disposed of in landfills (Carra and Cossu, 1990) where the organic component  (e.g., paper
products, food waste, and yard  waste) decomposes over  time and produces methane  if
decomposition occurs anaerobically.

Because only the organic component of solid waste decomposes to  produce methane, the
amount  of methane generated from landfills can be reduced by decreasing  the amount of
organic  material  placed  in landfills.  This can be achieved by: 1)  source  reduction  and
recycling; 2) composting; 3) incinerating the waste (with potential energy recovery); or 4)
using the waste in  other energy  production  technologies  (e.g.,  anaerobic digestion;
fermentation; pyrolysis).  These strategies can often be implemented  as part of a larger solid
waste management system.

Design and implementation of a solid waste management system requires that many regional
factors be taken into account. These factors include: characteristics of the waste, such as
volume, composition (e.g., organic component), and moisture  content; status of  current
collection equipment and management systems including landfill management; and the state
of markets for non-conventional  energy sources,  recycled materials, and other potential
products such as compost (organically  enriched soil amendments). Trends in these factors
must be anticipated so that regionally appropriate and adaptable systems are instituted.

Reducing the amount of waste that is  placed in  landfills  yields  significant benefits.  In
developed countries, short term savings can be realized from the avoided cost of  tipping fees
(i.e., landfill charges), and in  the longer term, the  demand for  new  landfill  capacity is
decreased or delayed.- In developing countries the costs of  managing landfills and other
sectors  of the waste  management system, which are typically borne by municipalities, can
also be  reduced.   In general, reduced landfilling  of waste decreases the magnitude of
environmental risk associated with landfills, such as surface- and groundwater pollution and

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LANDFILLS                                                                       2-21
air emissions.  In addition, many of the strategies presented here produce valuable products
such as energy and compost.
Reduction Technology Descriptions

The major strategies for reducing the landfilling of wastes and thereby avoiding  methane
emissions are described below.

   Source Reduction and Recycling:  The source reduction and recycling of organic material
   reduces methane emissions.  The most promising materials for this strategy are paper
   products. While other organic materials (e.g., food waste) can be composted, they do not
   readily lend themselves to recycling or reduced generation.  Paper products comprise a
   significant proportion of solid waste in developed countries (e.g., 40 percent in  the U.S.)
   and a growing  proportion of solid waste in some urban centers in developing  countries
   (typically 5  to 20 percent) (Mahin, 1988; Vogler, 1984).  Paper products can  be easily
   recycled by paper  mills into a variety  of products,  depending on the quality  of  the
   recovered material.   Markets are, in most cases, identical to those  for  virgin  paper
   products.

   Recycling can be accomplished through technologies and practices  of greatly varying
   technical complexity. In developing countries, where labor costs are low and equipment
   costs are relatively high, recycling  often occurs informally, uses relatively unsophisticated
   machinery, and involves intensive manual labor (e.g., for baling and sorting).  In  contrast,
   developed countries typically use  more complex labor saving machinery requiring higher
   operator skill  levels for collection, sorting,  and processing.   The differing  levels of
   complexity do not have a large effect on the overall capacity or effectiveness of these
   operations  (Vogler,  1984). In all cases, the quality of the recovered material is  the most
   important factor, and  is controlled to the degree necessary by  paper mills accepting
   recovered paper.

   Composting: Composting is the controlled biological decomposition of organic  material,
   usually under aerobic conditions, the end products of which are stabilized organic material
   and carbon dioxide. If aerobic conditions are maintained then no methane will be formed.
   The stabilized (oxidized) organic material is suitable for use as a soil amendment that can
   improve soil's physical, chemical, and biological properties (Kashmanian, 1991;  Biocycle,
   1991).  Composting can be easily integrated with other waste reduction practices such
   as recycling non-organics and incineration in a comprehensive waste management system.

   Composting operations vary considerably according to available space, technology, capital,
   capacity, and material to be accepted (Biocycle, 1991).  Composting can be carried  out
   either "in-vessel" (i.e., confined within a specially designed container), or more  simply in
   elongated piles referred to as windrows, which are laid out in large open spaces. Windrow
   composting is  sometimes carried out in covered  barn-like structures to  protect  the
   windrows from the wind and rain.  In-vessel composting  allows close  management of
   important variables, especially aeration, but is usually more complex to build and operate.
   Windrow composting uses bulldozers, front-end loaders, or specially designed mechanical
   turners to aerate the material.  Both processes may also use forced aeration, alone or in
   combination with turning.

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2 - 22                                                                       LANDFILLS
   The  composting  process  is affected by a number of physical,  chemical, and other
   environmental factors  which may,  with  varying degrees of effort, be monitored  and
   managed to control the composting process (Biocycle, 1991). Of primary importance are
   characteristics of the organic material (e.g., particle size and chemical structure of the
   organic compounds) which control the availability of nutrients to the microorganisms that
   decompose the waste.  For example, cellulose, hemicellulose, and lignin contained in wood
   and paper (high carbon content) are less digestible than meat and vegetable waste (high
   nitrogen content).  The nutrient balance of the organic material is typically measured by
   1) the ratio of carbon  to  nitrogen,  as  organisms require nitrogen to process  available
   carbon, and 2) the availability of  certain necessary macro- and  micro-minerals (e.g.,
   potassium, phosphorus). To control these factors, facilities carefully select and often pre-
   process waste before it is accepted.  Other factors that are monitored and controlled
   include process temperature, pH, aeration, and moisture.

   In order to produce a  clean and  valuable compost,  there are a  number  of important
   operational considerations in addition to the  factors listed  above.  For example, it is
   necessary to provide a clean substrate for the composting process; this is particularly true
   when composting municipal solid waste (MSW) because of the wide variety of non-organic
   components (e.g., glass,  metals,  and  large objects such  as  appliances).   Extensive
   separation equipment is required when handling mixed wastes, and the separation process
   can be designed to recover recyclables and/or produce a "refuse-derived-fuel" for use in
   an incinerator (see below). If a pre-separated waste such as yard  waste is composted,
   then significantly less equipment is needed to sort the waste.  Many  operations also shred
   the incoming waste to enhance the composting process, and screen the final product to
   remove any remaining non-organics  (Biocycle, 1991).

   Markets for compost include landscapers, nurseries, agriculture, land reclamation,  and
   landfill cover (Kashmanian, 1991).  Different markets have different specifications for
   compost properties such as acidity, particle size, and moisture content. The product must
   consistently meet these criteria to sell successfully. Potential markets should be identified
   early in the planning stage to ensure that the composting process can accommodate these
   requirements.

   Incineration:  Incineration of waste will  also  reduce methane emissions from waste
   management.  Other benefits  of incinerating waste are volume reduction (where land
   availability is an important consideration)  and potential energy recovery.  The extent of
   volume reduction will depend on the initial compactness and combustibility  of the waste,
   but as a rule of thumb incineration reduces the waste to 10 percent of its original volume
   (Mahin, 1988). The remaining ash must still be landfilled.

   Incineration has been used for many years, and a large number  of incineration plants (or
   municipal waste combustors) are currently operating successfully in developed countries.
   In the U.S., 14 percent of all solid waste was incinerated in 1988 (Kaldjian,  1990); Japan
   incinerates almost 70 percent of its solid waste because limited land availability increases
   the attractiveness of reducing  the volume of landfilled waste (Carra and Cossu,  1990).
   Reduced land availability and the potential for energy recovery are increasing interest in
   this technology in many countries, although stack emissions and ash disposal are still an
   issue.

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LANDFILLS                                                                       2 - 23
   Solid waste can be incinerated in either a "mass-burn" or "RDF"  process.  Mass-burn
   technology  burns  unsorted  or minimally sorted waste in  specially  designed boilers.
   Alternatively, waste can be sorted and shredded before incineration  to produce a "refuse-
   derived fuel," or RDF. A wide variety of processes have been developed to prepare RDF,
   and significant  research efforts are improving the quality and reducing the cost of RDF
   (Goodman and Walter, 1991).  RDF is a higher quality fuel than unsorted waste because
   it  contains  less inert  matter, has a smaller particle size, and can fire  or  co-fire  a
   conventional (or slightly modified) boiler.  For example, RDF may have an energy value of
   6,000 to 7,500 Btu/lb (3,300 to 4,200 kJ/kg), as compared to an average value of 4,500
   Btu/lb for unsorted waste in developed countries. Additionally, sorting removes metals
   and glass that may be recycled and sold to generate revenue.  Both mass-burn and RDF
   technologies have been implemented  in many countries.

   Most plants that recover energy use  the hot gases from waste combustion to produce
   steam, which in turn is used to power a steam turbine (which generates electricity) or to
   directly supply local heating needs.  Capacities typically range from  500 to 3,000 tons of
   waste per day,  with a generating capacity of 10 to 80 MW (Mahin, 1988).

   A number of factors have made incineration less technically feasible in developing regions.
   First, waste in these regions tends to  have a lower heat value (e.g., 1,500-3,000 Btu/lb;
   3,500-7,000 kJ/kg) than the drier and more combustible waste in developed countries
   (e.g.,4,500 Btu/lb; 10,500 kJ/kg). Second, the moisture content of wastes in developing
   countries is typically in excess  of 40 percent,  greatly increasing the capital cost of
   combustion systems and, in some cases, making  combustion impossible (Mahin, 1988).
   In  many cases, mass-burn and  RDF technologies designed for use in developed countries
   have encountered  difficulty when used  without  modification in developing countries.
   Some incineration projects in developing countries have attempted to overcome these
   problems by co-firing  wastes with fossil fuels or other biomass fuels, using rotary  kiln
   combustors with pre-heated combustion air to dry moist waste, and in some cases using
   separation and RDF equipment to improve fuel quality (Mahin, 1988).

   Alternative Processes:  Several emerging technologies are being developed which may
   reduce methane emissions from waste management.  The primary alternative waste
   management technologies are  1) controlled  anaerobic digestion (i.e., biogasification) to
   produce methane; 2) hydrolysis and fermentation to produce ethanol; and 3) pyrolysis (i.e.,
   thermal conversion) to  produce oil or  gas. These  are described below.

   •  Anaerobic Digestion. Organic waste maintained in a controlled anaerobic environment
      will undergo the same process of decomposition that occurs  naturally in  a  sealed
      landfill.   Carrying out the biochemical reactions in a digester vessel allows greater
      control over the process, reducing reaction times, improving efficiency, and facilitating
      gas collection. Solid waste digesters have been used in Europe, where several facilities
      have operated successfully for years (Platt et  al., 1988). As with  composting, only
      organic  material can  be  digested, requiring separation equipment to  remove non-
      organics from mixed wastestreams.

   •  Ethanol  Production. Converting solid waste to ethanol involves the following steps:
      separation  of the  organic material (if  necessary);  hydrolysis  to  form  sugars;
      fermentation of sugars to ethanol; and distillation to  purify the ethanol.  Ethanol is a

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2 - 24                                                                       LANDFILLS
       high octane liquid fuel that can be used independently or as a gasoline additive, and
       can also be sold as a chemical feedstock. Emerging technologies are making this type
       of conversion of solid waste increasingly feasible and economically attractive (Logsdon,
       1991).

   •   Pyrolvsis.  Pyrolysis is the thermal degradation of organic material  (usually  in the
       absence of oxygen), changing its chemical structure to produce combustible gases or
       a petroleum-like product called biocrude. Biocrude can be distilled to yield gasoline and
       similar energy products, which can be used in existing equipment without modification.
       Thermal yields from this process have exceeded  70 percent for  some  materials
       (Goodman, 1991).  Further research is needed to apply this technology to solid waste.

The ability of these technologies to reduce  methane emissions depends  directly  on the
quantity of organic material that is available (i.e., diverted from landfills) and the proportion
of this organic matter that  would  likely have decomposed anaerobically and  produced
methane.  Emission reductions associated with specific projects are highly variable but, in
theory, organic material can be completely removed, thereby achieving reductions of up to
100 percent.  The practical limitations discussed in more detail below constrain the  actual
reductions in methane emissions that are achieved in practice.
The capital and operating  costs for projects that reduce the landfilling of waste are highly
dependent on local factors.  The  costs are also dependent on the size of the  facility, the
planning of which must consider a  range of important factors such as the limits (and imposed
costs) of local infrastructure (e.g., transportation services, roads, technical skills) and markets.

   Composting:  Capital  costs for solid waste composting  facilities are highly variable,
   depending on many factors such as the level of technological complexity, characteristics
   of the waste source, local conditions, and the desired quality of the product. Capital costs
   per unit of capacity vary  by an order of magnitude.  For example, a survey of large U.S.
   facilities found a range from $1.5 million for a 300 ton/day plant, to $45 million for a more
   complex 550 ton/day plant  that also co-composts sewage sludge. Operating costs range
   from $9 to $85 per ton,  but are generally around  $20 to $40 per ton (Biocycle, 1991).
   These operating costs are competitive with average landfill tipping fees of $ 10 to  $65 per
   ton (NSWMA, 1990).

   Yard waste composting facilities, which are typically smaller, less complex, and do not
   require as sophisticated  sorting equipment as MSW composting facilities,  have lower
   capital costs.   In the U.S., these costs range from $80,000 to $2 million for plants
   handling from 2,000 to 60,000 tons per year of waste, and operating costs of  roughly
   $18 to $20/ton ($3-4/cubic yard) (Biocycle, 1991).

   Incineration:  Capital costs for boilers and  steam generators range from $60 to $300
   million for 10 to 80 MW facilities (Mahin, 1 988), or approximately $ 1 25,000 per  ton/day
   capacity for mass-burn or RDF  plants (Nollet, 1 989). RDF typically costs $2.50 to $2.90
   per MMBtu (Goodman  and  Walter, 1991)

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LANDFILLS                                                                       2 - 25
   Alternative Technologies: Biogasification has shown promise as a cost-effective option.
   Although the production  of ethanol from MSW has not achieved commercial application,
   this  technology is  projected to be  profitable in some applications in the near term
   (Logsdon,  1991).   Pyrolysis demonstration  projects have not  yet produced fuels  at
   competitive prices, and require further development and demonstration (Goodman and
   Walter, 1991).
Availability

Recycling,  composting, and incineration are technologies  that  have  been successfully
implemented under  a variety  of  operating  conditions, and  are commercially available
technologies. Continuing technological development and increasing operating experience will
improve the availability of these practices.  Of the alternative technologies described here,
only biogasification has proven technically feasible in full-scale application; other technologies
have  proven feasible in small-scale  demonstration  projects.   Further  developments are
expected  to increase the  availability, feasibility,  and economic attractiveness of these
alternative technologies.
Applicability

The applicability of these technologies and practices varies for the different regions of the
world. The majority  of these technologies has been developed for application in developed
countries.  Due to differences in waste composition  (and other physical factors); limitations
in financial, technical,  and infrastructure  resources; regulatory  incentives;  and  cultural
practices, the applicability of waste management technologies and practices presented here
must  be carefully considered in  the context of developing  nations.   In  general, waste
management alternatives that are  less technically complex, more labor intensive, and rely
primarily on indigenous  resources  will  be more successful in  developing nations.  Rapidly
increasing energy demand in these countries can also spur waste management technologies
that produce energy.

Many of the technologies discussed  in this  section are receiving  renewed  application and
research as the issue of  solid waste management is addressed  in  both  developed and
developing countries. The management of solid waste is a rapidly growing industry often
driven by government  legislation  and regulation.   The  approaches  discussed  here can
successfully accommodate highly variable site-specific criteria  and  regional needs to provide
a comprehensive waste management system.  Planners in Europe and North America are
increasingly relying on a regionally or  locally tailored mix of options to handle municipal solid
waste (Kaldjian, 1990; Platt, 1988).
Barriers

None of these technologies and practices is a panacea for the problem of waste management;
each option has drawbacks when applied in certain situations.  However, these drawbacks
are sometimes cited as barriers to implementation without proper comparison to the problems
of existing  or alternative waste management  practices.  With proper  planning  and

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2 - 26                                                                       LANDFILLS
management, cost-effective and environmentally beneficial solutions can be developed. With
this caveat in mind, the following are the most commonly identified problems with each
technology:

   Recycling:  Recycled paper products must be priced competitively with virgin products to
   be successful. Competitiveness largely depends on the regional cost of virgin wood pulp;
   countries  with  large, often  subsidized  supplies of wood pulp  have a disincentive for
   recycling. As with many products derived from solid waste, recycled paper products may
   also be perceived as being of inferior quality.

   Composting: Poorly managed  composting operations may be partly anaerobic, creating
   odor and plant pathogen problems; however, these problems are much less common as
   operating  experience develops (Biocycle,  1991).   Other anticipated problems include
   gaining and maintaining product acceptance; identifying and penetrating new markets; and
   in some cases, contamination with pesticides and heavy metals.

   Incineration: The main  limitation to this technology has been concern over air emissions,
   which  has  made  it difficult to  site incinerators near the urban centers where waste is
   generated.  The ash that remains after combustion may contain significant quantities of
   heavy  metals, potentially causing problems if disposed  of in a poorly designed landfill.
   Also, in developing countries,  the low energy and high  moisture of most waste makes
   combustion infeasible without  modified  technology.

   Alternative Technologies: These technologies are in various stages of development and
   acceptance. In all cases, further research and demonstration will increase efficiencies and
   acceptance, and decrease costs.
Benefits

In addition to reducing the potential for methane emissions from landfilled organic material,
the processes described above have the following benefits:

   •  Source Reduction/Recycling: Reducing the amount of waste that must be handled by
      other methods, such as landfilling or  incineration,  can remove the strain on waste
      management systems and effectively increase system capacity.  Moreover, recycling
      provides a valuable product that can generate revenue.

   •  Composting: The use of compost as a soil amendment can improve soil porosity and
      water retention,  erosion resistance,  and tilth.  By encouraging  plant growth (and
      uptake of nitrogen), nutrient runoff is reduced. Furthermore, some compost has been
      shown to suppress plant disease (Kashmanian, 1991).

   •  Incineration: Incineration can greatly reduce the volume of landfilled waste, thereby
      alleviating the pressure for new landfill construction while providing a valuable source
      of energy.

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LANDFILLS                                                                        2 - 27
      All of  the  technologies  that reduce  landfilled waste will  reduce the  potential
      environmental and health risks associated with landfills, such as air quality problems
      and surface- and groundwater contamination.
                       Reduced Landfilling of Waste

                       • methane  reductions  dependent  on
                         quantity  of  reduced  organics  up to
                         100%
                       • reduced need for landfill capacity
                       • flexible, appropriate practices
                       • technologies currently available

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2 - 28                                                                     LANDFILLS


2.5  References

Contributions were made by:


   Masataka Hanashima, Faculty of Engineering, Fukuoka University, Japan

   Yasushi Matsufuji, Faculty of Engineering, Fukuoka University, Japan

   Kurt Roos, USEPA, USA

   W. T. Morris, Department of Energy, Energy Technology Division, United Kingdom


Additional information may be found in the following:
Anderson, C. (1991), Waste Management  of North America,  personal communication,
October 8, 1991.

Biocycle (1991), The Art and Science of Composting. JG Press, Emmaus, Pennsylvania.

Carra, Joseph S. and Raffaello Cossu, eds. (1990), International Perspectives on Municipal
Solid Wastes and  Sanitary Landfillinq.  International  Solid Wastes and  Public  Cleansing
Association,  Academic Press, London, England.

Cointreau, Sandra J. (1982), Environmental Management of Urban Solid Wastes in Developing
Countries. World Bank, Washington, D.C.

EPRI (Electric Power Research Institute)  (1992), Summary of Landfill Gas Potential: 2 MW
Molten Carbonate  Fuel  Cells,  prepared by Resources  Management  International,  Inc.,
September 1992.  EPRI TR-1 01-068-Project 1677-21 (Interim Report).

Gendebien, A., M.  Pauwels, M. Constant, M.J. Ledrut-Damanet, E.J.  Nyns, H.C. Willumsen,
J.  Butson, R. Fabry, and G.L. Ferrero (1992), Landfill Gas: From  Environment  to Energy
(1 992) - Final Report, Commission of the European Communities.

Goodman, Barbara J. and Donald K. Walter (1991), "Opportunities for Energy from Municipal
Waste Technology," in Energy Sources, volume 1  3, pp.1 79-1 88.

Governmental Advisory Associates, Inc. (GAX\) (1992),  1991-2 Methane Recovery from
Landfill Yearbook,  prepared by Eileen Berenyi and  Robert Gould, GAA, NY.

Governmental Refuse Collection  and Disposal Association (1990), Proceedings of the  13th
Annual International Landfill Gas Symposium, Silver Spring,  Maryland, GLFG-0018.

Japan Environment Agency (JEA) (1991), personal communication, provided by Hanashima
and Matsufuji, Fukuoka University,  Japan.

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LANDFILLS                                                                      2 - 29
Kaldjian, Paul (1990), Characterization of Municipal Solid Waste in the United States: 1990
Update. U.S. Environmental Protection Agency, Washington, D.C., EPA/530-SW-90-042.

Kashmanian, R. M. (1991, draft), Markets for Compost. Office of Policy,  Planning,  and
Evaluation, U.S. Environmental Protection Agency, Washington, D.C.

Logsdon, Gene (1991), "Producing Ethanol from Solid Waste," in Biocvcle, July. 1991, pp.71-
72.

Mahin, D.B.  (1988), Prospects in Developing Countries for Energy from Urban Solid Wastes.
Office of Energy, U.S. Agency for International Development.

Maxwell, Greg (1990),  "Will Gas-to-Energy Work at  Your Landfill ?," in Solid Waste  and
Power, June 1990.

Monteiro,  Penido (1992), coordinator of landfill gas projects in Rio De Janeiro and  Manaus,
personal communication.

National Solid Wastes Management Association (NSWMA) (1990), 1990 Landfill Tipping Fee
Survey, prepared by S. Sheets and E. Repa, NSWMA, Washington, D.C.

Nollet, Anthony (1989), "Designing Shredding Plants That Don't Go Up in Smoke,"  in World
Wastes, June 1989.

Pacey, J.G.  and J.P. DeGier  (1986), "The Factors Influencing Landfill Gas Production,"
presented at Energy from Landfill Gas, sponsored by UK DOE/US DOE, 28-31 October, 1 986.

Platt, B. A.,  Neil  Seldman, Bernd Franke, and Bernd Mayer (1988), Garbage  in Europe:
Technologies. Economics, and Trends, Institute for Local Self-Reliance, Washington,  D.C.

Richards, K.M. (1 989), "Landfill Gas: Working with Gaia," in Biodeterioration Abstracts. Vol.
3, No. 4, December 1989.

Soot, P.M. (1991 a), "Power Generation Using Small Internal Combustion Engines," prepared
for the Global Change Division, USEPA,  1991.

Soot, P.M. (1991b), "Enrichment of Dilute Methane through Adsorption," prepared for the
Global Change Division, USEPA, 1991.

Sturgill, C. (1991), "Power Generation: On-Site Use and Sale to Utilities," prepared for ICF
Inc., April  1991.

Taylor, Alison C. and Richard M. Kashmanian (1988), Yard Waste Composting: A Study of
Eight Programs, U.S. Environmental Protection Agency, Washington, D.C., EPA/530-SW-89-
038.

Thorneloe, S.A., and R. Spiegel (1990) (draft), Global Climate Mitigation:  Use of Fuel  Cell
Power Modules to Recover Energy from  Landfill Gas, AEERL/ORD, USEPA,  May 1990.

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2 - 30                                                                     LANDFILLS
Thorneloe,  S.A., D. Augenstein, J.  Pacey (1992a),  Landfill Gas and  Energy Utilization:
Technology Options and Case Studies,  prepared by EMCON Associates for AEERL/ORD,
USEPA, Research Triangle Park, NC. EPA-600/R-92-11 6, June 1992.

Thornleloe, S.A., (1992b), "Landfill  Gas Recovery/Utilization:  Options and Economics,"
presented at the  16 Annual Conference by the Institute of  Gas Technology on Energy from
Biomass and Wastes, Orlando, Florida, March 5 ,1992.

USEPA (United States Environmental Protection Agency) (1 991), Air Emissions from Municipal
Solid Waste Landfills - Background  Information  for Proposed Standards and  Guidelines.
OAQPS, March 1991, EPA-450/3-90-011a.

USEPA (1993a), Anthropogenic Methane Emissions in the United States. Report to Congress,
USEPA/OAR (Office of Air and Radiation), Washington, DC.

USEPA  (1993b), Options  for Reducing Methane  Emission  Internationally  -  Volume  II:
International Opportunities for Reducing Methane Emissions,  Reportto Congress, USEPA/OAR,
Washington, DC.

Valenti, Michael (1992), "Tapping Landfills for Energy," in Mechanical Engineering, January
1992.

Vogler, Jon A. (1984), "Waste Recycling in Developed Countries," in  Holmes, John  R, ed.,
Managing Solid Wastes in Developing Countries. John Wiley and Sons, Chichester, England.

Williams, R.H. and E.D. Larson (1990), "Power Generation with Natural Gas Fired Turbines,"
in Natural Gas: Its Role and Potential  in Economic Development, eds. W Vergara, N.E. Hay,
and C.W. Hall, Westview Press, 1990.

Woo, M.Y.C.  (1990), "PAFC Fuel Cell -  A Unique Solution to Clean Air," presented at the
California Clean Air and New Technologies Conference, October 15-17,  1990.

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CHAPTER THREE
OIL AND  NATURAL  GAS
3.1  Background

Methane Emissions

Methane is the primary constituent of natural gas, and significant quantities of methane can
be emitted throughout a country's natural gas system.  This system generally includes gas
and oil wells, processing and  storage facilities, and transmission and distribution systems
(presented schematically with additional explanation in Exhibit 3-1). Emissions primarily result
from the normal operations of many natural gas system components, such as venting and
flaring at oil and gas wells, compressor  station operations, gas processing  facilities, gas-
operated control devices, and unintentional leaks (fugitive emissions). Methane  emissions also
occur during routine maintenance, with additional emissions from unplanned system upsets.
These sources are described in more detail below.

    •  Many oil production facilities also produce associated gas which is often flared or
      sometimes vented.  In addition, an undetermined quantity of natural gas  is released
      during the drilling of  oil and gas wells before wellhead gathering equipment is installed,
      and before the well  is plugged and suspended or abandoned.

    •  Gas processing  plants  typically  vent  methane while  reclaiming the dehydrator
      chemicals, often glycol. These gas plants contain a high density of control devices
      (valves, etc.), which also contribute to emissions through normal  operation.

    •  Reciprocating engine and turbine compressors are used throughout gas systems to
      pressurize the gas, and to generate electricity and provide motive power for various
      facilities. These engines typically use pipeline gas for fuel. Methane emissions result
      from incomplete  combustion and from venting during engine stops and starts.

    •  Pneumatic  or gas-operated  devices use  the pressure of pipeline  or process  gas to
      power their operating mechanisms.  Emissions occur when the gas used to run the
      devices is vented to the atmosphere. These devices include pressure regulators, valve
      positioners, and actuators.

    •  Fugitive emissions are leaks in pipelines or other components.  They typically occur at
      connections between components and in valves where seals or gaskets fail, through
      the corrosion of  pipelines,  and from end-use  equipment such  as residential  gas
      appliances  and industrial furnaces, and power generators.

Methane emissions also occur during routine  maintenance, when gas  from facilities or
equipment is purged to the  atmosphere.  These activities include the venting (blowdown) of
equipment and pipeline  sections for periodic  testing  and repair,  and the launching  and
receiving of scrapers and pigs. Also, releases occur during well workovers  - the routine
maintenance of production  wells.

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3 - 2
OIL AND NATURAL GAS
                                        Exhibit 3-1
                                   Natural Gas Systems
                        Production
                        Injection/Withdrawal
                             Storage
                   Residential         Commercial         Industrial
    Electric
     Utility

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OIL AND NATURAL GAS                                                               3 - 3
                                  Exhibit 3-1 (cont.)
                                 Natural Gas Systems
      Natural gas  production  is  generally categorized as  "associated"  or "non-
      associated" production, where associated gas is produced in association with oil,
      and non-associated gas is produced from dedicated gas fields.  Both associated
      and non-associated production facilities withdraw the gas from underground
      formations and collect it at a central location for processing before injection into
      the transmission system. Significant volumes of natural gas are often produced
      with the oil taken from petroleum reservoirs, and oil production facilities that do
      not utilize natural gas must either vent, flare, or re-inject the gas.

      Natural gas processing plants ensure that the characteristics of the gas are
      suitable for the transmission system and the intended end-use.  This involves
      removing  heavier  hydrocarbons (referred  to  as  condensate), moisture,  and
      impurities such as sulfur compounds, particulates, and carbon dioxide.

      Storage systems are  used to meet  seasonal  fluctuations in demand without
      similar fluctuations in production.  During periods of low demand, the excess
      production is injected into  depleted  oil and gas  fields, salt domes, and other
      suitable formations.   When  demand  rises,  the stored  gas is  withdrawn,
      processed, and injected into the transmission system.

      The transmission  system  is a network of high pressure pipelines used to
      transport the gas from the production, processing, and storage facilities to the
      distribution networks. In addition to the pipelines, transmission systems include
      metering stations, maintenance facilities (e.g., pig-launching),  and compressor
      stations. Compressors are used to maintain pressure throughout the natural gas
      system, and are located at regular intervals along the pipeline.  Compressors are
      usually driven by reciprocating or gas turbine engines which use the pipeline gas
      as fuel.

      The distribution system is an extensive network  of pipelines supplying  natural
      gas to end users.  The pipelines are generally of smaller  diameter and lower
      operating  pressures than transmission pipelines.  Gas enters the  distribution
      system at gate stations, or "city gates," where the gas pressure is first reduced.
      The gas pressure must be reduced from approximately 1000 pounds per square
      inch  (75  Bar) in  the  transmission  pipeline to about 0.5  psi (30 mBar) for
      residential applications.  Commercial, industrial, and public utility requirements
      for gas pressure vary by application,  and  are typically around 10-200 psi (1-15
      Bar). This pressure reduction usually occurs in steps through different sections
      of the distribution network.

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3-4                                                              OIL AND NATURAL GAS
Unplanned events such as pressure surges and line breakages contribute to the release of
natural gas. Pressure relief systems often vent gas directly to the atmosphere, rather than
flaring or returning relieved gas to the pipeline. Line breakages are usually caused by external
forces such as construction or land subsidence, but also as a result of corrosion.
Methane Emission Reduction Strategies

Emissions from normal operations account for the majority of releases worldwide, although
the emissions from each system will depend on the specifics of that system.  The technical
nature of emissions from natural gas systems is well understood, and emissions are largely
amenable to  technological solutions,  through enhanced  inspection  and  preventative
maintenance, replacement with newer designs, improved rehabilitation and repair, and other
changes in routine operations and maintenance.

The economic cost (i.e., lost revenues) of venting methane to the atmosphere may provide
an incentive for changed practices.  In some regions, air quality regulations controlling the
release  of hydrocarbons  apply to natural gas systems,  and changes are legally required.
Concerns over safety, and occasionally the noise of venting at gas facilities, can also motivate
efforts to reduce emissions.

Emissions reduction strategies presented in this assessment are:

   Reduced Venting and Flaring During Production:  Venting during the production of both
   associated and non-associated gas is a controllable release of natural gas.  The most
   preferable strategy is to fully recover and process associated gas for use as a fuel. Where
   demand for gas and an  adequate infrastructure do not currently exist, reinjecting  gas or
   installing inexpensive flares can almost completely eliminate methane emissions while
   providing the important benefits of maintaining formation pressure (reinjection only) and
   enhancing  safety.  The use of more efficient  flares  can also reduce emissions from
   unburned  gas.  Additionally, changes can be  made in  operating  practices to reduce
   extraction losses and  emissions from wells under development.

   Improved Compressor Operation:  Enhanced maintenance and monitoring the fuel  use of
   compressor prime movers can reduce fuel costs while also reducing methane emissions.
   Using gas turbines  in place of reciprocating engines to power compressors can reduce
   methane emissions (per unit of gas used) by over  an order  of magnitude,  as well as
   reducing emissions of other pollutants such as CO and NOX. Reductions can also be
   achieved by capturing gas that is currently vented  during stops and starts, and using
   auxiliary power (i.e., hydraulic) for turbine starts (rather than gas pressure).

   Improved Leak Detection and Pipeline Repair:  Gas pipelines are subject to corrosion and
   subsequently develop chronic leaks (i.e., small, continual leaks). Preventing and repairing
   these leaks will reduce  fugitive emissions.  This can be  achieved through a number of
   actions including  improved   leak  detection  and  pipeline  inspection,  preventative
   maintenance and replacement programs, and the increased use of corrosion resistant
   materials (e.g., coated  steels, PVC, PE).  In addition, gas releases resulting from line
   breakages can be reduced with automatic shut-off valves.

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OIL AND NATURAL GAS                                                               3 - 5
   Low Emission Technologies and Practices:  Emissions occur from routine operations and
   practices, including gas-operated control devices, fugitive emissions from component
   joints, and pipeline purging for maintenance purposes. Low emission technologies include
   pipeline control devices with reduced or eliminated venting of natural gas ("low-bleed" or
   "no-bleed" devices), directed inspection and maintenance programs, and the capturing of
   purged gas.

Exhibit 3-2 summarizes information on these four strategies, which are described in more
detail in the individual technological assessments.

The assessments consist of the following sections:

   • Reduction Technology Description;
   • Costs;
   • Availability;
   • Applicability;
   • Barriers; and
   • Benefits.

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OIL AND NATURAL GAS                                                              3 - 7
3.2   Reduced  Venting And Flaring During Production

The technologies and practices presented here reduce methane emissions from the production
of oil and natural gas. The largest reductions can occur from using associated gas production,
rather than venting or flaring this gas.  Additional small reductions can occur from general
improvements in operating practices. (Fugitive emissions and venting from pneumatic devices
in production and processing are addressed in section 3.5).
Reduction Technology Description

Both oil and natural gas fields produce natural gas.  In the case of dedicated natural gas
production (non-associated gas), the release of gas, intentional or accidental, is a clear loss
of a valuable resource. On the other hand, gas produced from oil fields (associated gas) is not
the primary product, and is sometimes viewed as an inconvenience rather than an energy
resource.  As a result, most studies agree that methane emissions from oil production are
higher than those from gas production (Barns and Edmonds, 1990).

   Oil Production:  The environmentally preferable strategy for reducing methane emissions
   from oil production is to fully recover and process the associated gas for local fuel use or
   for  sale to a pipeline.  This strategy not only eliminates the emissions but also takes
   advantage of the energy value of the gas.  However, this strategy requires a gas supply
   infrastructure and demand for natural gas as an energy source.
   Where demand for gas and an adequate infrastructure do not currently exist, gas produced
   from oil fields is flared, vented, or reinjected.  (Also, gas may be vented or flared if the
   wellhead pressure is too low to be brought up to adequate transmission pressure with
   existing compressor  equipment.)  In each case,  the gas is separated from the oil and
   directly released (venting), burned off (flaring), or reinjected into the field to help maintain
   formation pressure.  Reinjection prevents emissions  as long as the exhausted well is
   plugged properly so that it does not leak once  production ceases. Flaring is preferable to
   venting because even an inefficient flare will destroy the majority of the methane (usually
   more than 98 percent).  However, it  is important to install flares that will either burn
   continuously or be self-igniting so that venting  from flares is minimized. Effectively flaring
   or reinjecting gas that  is currently vented could significantly reduce methane emissions
   from production facilities.

   Estimates of the proportions of gas vented, flared and  reinjected are difficult to develop
   due to incomplete data. Flaring and venting has been estimated to  be around 5 percent
   of world natural gas production, with 20 percent of this being vented (Barns and Edmonds,
   1990).  However, this estimate is very uncertain.  A similar amount, 6 to 7 percent of
   world production, is thought to be reinjected (Barns and Edmonds, 1 990; US DOE, 1992).
   In general, flaring and venting of associated gas  is more prominent in young extraction
   industries that do not have a gas infrastructure  or demand. Encouraging the use of natural
   gas and the development of infrastructure can  help reduce emissions from oil production.
   Baudino and Volski (1991) estimate that a 50 percent reduction in emissions from venting
   and flaring is readily achievable.

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3-8                                                               OIL AND NATURAL GAS
   Gas Production: Emissions from gas production arise during exploration, extraction losses,
   and system upsets.   Reducing  emissions  from  these  sources  involves  marginal
   improvements in existing practices -- better housekeeping -- that will also reduce safety
   hazards from methane leaks and reduce lost product.  Extraction losses worldwide are
   thought to be approximately 5 percent of production (Barns and Edmonds, 1990), although
   there are large differences between sites. The reductions achieved at individual sites will
   depend on current emissions and the success of changes in operating  practices.
The costs for reducing methane emissions are highly dependent on regional and site specific
factors. As an example, India recently received a $450 million loan to build the infrastructure
necessary to reduce the annual venting and flaring of approximately 116 bcf of gas from the
Bombay High offshore oil field.  This gas will be used in onshore factories (Banerjee, 1991).
The fuel  cost savings are expected to cover the cost of the loans.  Existing  technology,
equipment, and practices will all affect the cost and feasibility of various reduction options.

Where the market for  gas exists, utilizing  natural gas as an energy source will generate
revenue  from gas sales,  and will  encourage infrastructure  development.  Alternatively,
reinjection can improve well production sufficiently to be a cost effective option where there
is adequate drilling technology to support the development of reinjection wells.  Where gas
is currently vented, the installation of rudimentary flares is relatively inexpensive.  However,
because  flaring does not  utilize the gas as fuel  and emits CO2 and CH4, it is the  least
environmentally beneficial option, but remains preferable to venting.
Availability

The technology  and expertise exist to develop uses and the  necessary infrastructure for
transporting the  associated gas.  Efficient flaring and reinjection are also common practices.
Beneficial changes in operating practices and/or equipment that reduce fugitive emissions and
extraction losses are also available technologies.
Applicability

Utilizing the gas as a fuel is applicable where the infrastructure and demand for gas exists,
and the quantity is sufficient to recoup the investment through fuel substitution (i.e. gas for
oil).   Encouraging  demand  and infrastructure  growth  will enhance  this development.
Reinjection is  economical where the reservoir structure  (geology) supports the enhanced
recovery of hydrocarbons through repressurization.  Without the proper structure, this option
is very costly.  Where associated gas is currently  vented, simple flares can achieve major
reductions of methane emissions at a low cost. Regions that do  not utilize, reinject or flare
the gas likely include the Middle East, Africa, Latin America, China, and certain areas of Asia
(Barns and Edmonds, 1990).  As an interim step, flaring should be encouraged over venting.
More general improvements in operating practices that reduce emissions from exploration and
other fugitive emissions, and improve the efficiency of flares, are  applicable in most regions.

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OIL AND NATURAL GAS                                                               3 - 9
Barriers

The primary barrier to reducing the release of methane into the atmosphere is generating
demand for associated gas, and the infrastructure to supply the market.  Historically, this
development has lagged behind oil production. Developing sufficient infrastructure requires
capital and the availability of appropriate technology. Additionally, institutional inertia can
delay changes in the energy supply.

Changes that reduce emissions can be driven by the  value of the recovered gas.  However,
many regions that vent and flare gas do not have convertible currencies or free market pricing
mechanisms for gas,  making investments difficult to pay off.  Compared to oil from these
regions, which is exported for hard currency, the gas  saved would produce little cash return.
The other benefits of  reducing methane emissions are less directly realized  (non-cash), and
are not typically analyzed when considering changes in current operating practices.
Benefits

Reducing  methane emissions  from oil and natural gas production will have  the following
benefits:

   •   Improved safety.  Reducing releases of methane, which is potentially explosive, will
       reduce the risk of accidents.

   •   Use of a clean and efficient fuel. Methane is a convenient and clean energy source,
       producing less CO2 per unit energy than other fossil fuels, and  also producing smaller
       amounts of local air pollutants such as particulates, nitrogen oxides, and sulfur oxides.

   •   Increased energy productivity.  Reducing the  venting and  flaring of  gas  by using
       associated gas, and also reducing extraction losses from both oil and gas production,
       will effectively increase the available energy supply.
                       Reduced Venting and Flaring

                       •   methane reductions of up to 50%
                       •   optimize energy supply
                       •   reduce risks
                       •   technology currently available
                       •   clean energy source

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3-10                                                            OIL AND NATURAL GAS
3.3   Improved Compressor Operation

This strategy reduces the methane emissions in the exhaust of gas-fired compressors, which
arise because a portion of the fuel remains unturned during the combustion process.  The
most widely applicable method will be to reduce  the amount of fuel  used by compressors
(thereby decreasing emissions even if the emissions factor remains constant). Importantly,
reducing fuel use can result in significant savings. A second option is to use gas turbines,
which  have much lower  methane emissions,  as compressor prime movers in place of
reciprocating engines  wherever economically,  operationally, and technically feasible.  In
addition, altering other practices such as engine starts and stops  can  reduce the amount of
natural gas that is vented to the atmosphere.
Reduction Technology Description

Most compressors are used in transmission pipelines to maintain the pressure in the pipelines.
Energy is lost due to friction as gas flows through transmission pipelines, resulting in a gradual
drop in pressure; a compressor compensates for these frictional losses. Energy must also be
expended to bring  gas up to  pipeline  pressure from gas fields and storage facilities, and
compressors also are used for this purpose.  The basic components of a compressor station
are a prime mover, a  gas compressor, and auxiliary equipment.

    Prime Mover: A prime mover is an engine which supplies power to the gas compressor.
    Reciprocating (internal combustion)  engines and gas turbines are most common, although
    electric engines and steam turbines have also been used.  Reciprocating engines and
    turbines usually use pipeline  gas as fuel.

    Gas Compressor:  Compressors use the energy supplied by the prime mover to increase
    the pressure of the gas.  This is done either by compressing an enclosed volume of gas
    (e.g.,  in a piston), or increasing the velocity of a continuous gas flow.

    Auxiliary Equipment:  This includes starter systems,  piping, filters, cooling systems,
    instrumentation, and buildings.

Methane  is released from a number of sources in compressor operations, although almost all
emissions are associated  with the prime mover.  The majority of methane emissions from
compressors result from  incomplete combustion  of  the natural gas  used for fuel.  Large
volumes  of methane  can  also be released if the pressurized pipeline  gas is  used in starter
motors or to start gas turbines  directly.  Starts and stops vent significant quantities of
unburned fuel for safety reasons. Emissions can be improved  by reducing fuel usage, using
gas turbines where feasible, by changing the method of starting engines, and by reducing the
number of engine stoppages.

    Reduced Fuel Use: Fuel use can be improved by better maintenance practices and through
    more efficiently engineered engines.  First, improving the analysis of gas-fired compressor
    engine efficiency  can reduce fuel  use by several percent,  thereby reducing methane
    emissions (for a given emissions factor).  One  such system, instituted  by  Northwest
    Pipeline, involved enhanced  monitoring  of  engine performance to track fuel use and

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OIL AND NATURAL GAS                                                             3-11
   compare it with predicted fuel use.  The continuous monitoring of fuel consumption
   enabled operators to identify performance inefficiencies and to correct problems quickly
   (Zebelean, 1991).  Improved  maintenance can improve thermal efficiencies, as well as
   reduce fuel use.

   Second,  exhaust emission levels  can also be reduced with the use of more efficiently
   engineered engines.  For  example,  lean burn  engine  technology enables an  internal
   combustion engine to run on a more dilute air-fuel mixture, reducing fuel use and also
   reducing emissions of particulates and carbon monoxide.  Similarly, rich burn engines can
   be modified with improved air-fuel ratio controllers.

   Combustion Efficiency -  Prime Mover Choice:  The two most, common types of prime
   mover engine are gas turbines and gas-fired internal combustion (reciprocating)  engines.
   As a rough approximation, methane emissions in the exhaust are an order of magnitude
   lower for gas turbines than for similarly rated reciprocating engines, largely due to the
   greater air flow into the combustion chambers of gas turbines. Thus, potentially the most
   effective reduction option is to install gas turbines, as  opposed to internal combustion
   engines,  where technically and operationally  feasible. For example, recent estimates for
   emissions from reciprocating engines, weighted by actual fuel use, are approximately 500
   kg of methane per  MMcf of fuel used, whereas turbines emit 6 to 12 kg of methane per
   MMcf used (USEPA,  1 993a).  Designing new  pipeline systems to maximize the use of gas
   turbines or replacing reciprocating engines with turbines can therefore reduce emissions
   at a given location by upwards of 90 percent. The decision to install one or other type of
   engine, or to swap out an existing engine, will depend on the economics and site specific
   operational requirements.

   Engine Starts:  Starting an engine can require  up to 10 percent of its rated power, and this
   power is often supplied  by utilizing  the  pressure of pipeline  gas in gas driven starter
   motors for both reciprocating  engines and gas turbines (AGA, "Compressors").  The gas
   that is used in these motors is usually vented  to the atmosphere. These emissions can be
   reduced  if the gas  is  captured,  or  if alternative power  sources  such as  electricity,
   compressed air, or hydraulic pressure are considered.

   When engines are started and shut down there are periods when fuel passes through the
   engine without being burned.   Reducing the number of stoppages, and improving engine
   starts (e.g., by increasing starting motor capacity) can reduce the quantity of gas that is
   vented.
Costs for these technologies and practices vary considerably, being highly dependent on site
specific factors.  Under a wide range of conditions, however, some of these options provide
a return on investment through fuel savings.

   Reduced Fuel Use: The fuel use monitoring program instituted by Northwest Pipeline has
   proven cost-effective, potentially reducing fuel costs by $1 28,000 per year and methane
   emissions by approximately 30 metric tons per year, in a 7,000 mile pipeline system with
   a mainline capacity of 2 bcf per day (Zebelean, 1991).

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3-12                                                             OIL AMD NATURAL GAS
   Prime Mover Choice:  Gas turbines are becoming increasingly economically competitive
   for large transmission compressor stations. Capital costs for a  6 MW gas turbine prime
   mover are estimated to be about  $700/kW.   Operation and  maintenance costs are
   0.60/kWh.   A larger system  of 17.5 MW would  have a  capital cost  of  $600/kW,
   demonstrating  some  economies of scale, with operation  and maintenance costs of
   0.70/kWh  (Sturgill, 1991).  In comparison, capital costs for internal combustion (1C)
   engines are estimated to be $400 to $800/kW, with operation and maintenance costs of
   2C/kWh  (Soot, 1991).  Gas turbines become more cost competitive for larger systems.
   (These figures are for engines alone, and do not include the cost of the compressors and
   auxiliary equipment, which may not  have to be  switched.) Total installed costs will vary
   considerably by location and specific application.

   Other:  Alternative strategies include the use of lean burn 1C engines and air-fuel ratio
   controllers, non-gas powered starters, and capturing vented gas.  These technologies and
   practices have typically  been installed only where there are regulatory incentives, as the
   efficiency gains usually  are only marginally economic.  Any alteration in practices that
   does not require significant new equipment, such as capturing  vented gas or improving
   compressor seals, is more likely to be economically justified; often the most important
   factor is the cost of the  lost gas (or  alternative energy supplies).
Availability

Compressor station technology is well developed, and  continuous  developments  in high
efficiency and low emissions engines are being made.  In particular, these developments will
increase the availability of appropriate and economically viable gas turbine technology.
Applicability

The operating characteristics of gas pipeline systems will vary greatly by design, and the
applicability of the technologies described here must  be  evaluated  individually for  each
system. However, closer monitoring of fuel use and improved maintenance and efficiency is
a widely applicable technique. While it is likely that some  improvements can be made virtually
everywhere  through  enhanced fuel  use inspection   programs,  the  most   significant
improvements are expected in countries with older and less technologically sophisticated
systems, as these systems typically will be  using more inefficient prime movers (with shorter
lifetimes).

Currently, the economics and operating characteristics of turbines make them an attractive
choice as prime mover for larger transmission stations (e.g., above 8-10,000 hp;  10-13 MW)
(Ervin, personnel communication).

In general, new technologies must be economically attractive and able to perform at least as
effectively  as existing equipment.  In some cases, external incentives such as air quality
regulations may drive the installation of new equipment.   Because of the high capital cost of
installation, advanced equipment will not immediately replace existing equipment, but will
gradually be installed in new pipeline construction and during  the scheduled replacement of
compressors.

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OIL AND NATURAL GAS                                                             3-13
Barriers

Installing new equipment, such as prime movers and other equipment for emissions control,
monitoring  fuel use, and alternative starting practices, may involve a relatively high initial
capital investment.  In these cases, the availability of funds can be a barrier to  installing
equipment  that will be more economic in the long  term.  Also,  the long lifetimes of well-
maintained equipment can limit the speed with which new technology is introduced.

Many technologies and operating practices do not require significant investment in equipment,
and are therefore more likely to be introduced quickly.  However, a lack of information or
technical experience may hinder adoption of certain practices.
Benefits

In addition to reducing methane emissions from compressor stations, this strategy has the
following benefits:

   •   Reduced  natural  gas losses:   Some systems  are  estimated to use a significant
       proportion of total throughput for compressors. Installing more efficient compressors
       can increase actual energy supply by reducing the fuel used by compressor stations.

   •   Improved pipeline performance:   The installation of more advanced  and reliable
       technologies will  improve the overall performance of the natural gas system.

   •   Improved air quality:  Reducing gas losses reduces the effect that such emissions have
       on local air quality.  In addition, improving compressor operations lowers the emission
       of other pollutants such as NOX.
                       Compressor Operation

                       •  methane reductions of up to 90%
                       •  reduced transmission losses
                       •  cost-competitive practices
                       •  technology currently available
                       •  improved air quality and safety

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3-14                                                             OIL AMD NATURAL GAS
3.4   Improved  Leak Detection and Pipeline Repair

This assessment describes technologies and practices to improve leak detection, to prevent
corrosion of pipelines, to repair pipelines when they do fail, and to replace those sections of
pipeline that cannot be cost-effectively maintained.  Techniques for both transmission and
distribution pipelines are discussed.
Reduction Technology Description

Natural  gas pipeline systems are  divided into transmission  and distribution  networks.
Transmission networks  are  high pressure (typically  1000 psi;  75 Bar) pipelines used to
transport gas from production, processing, and storage facilities to the distribution networks.
Distribution  pipelines carry gas from the transmission pipeline to the end user.   The gas
pressure is reduced in steps through different sections of the distribution network, from 1000
psi at the connection to the  transmission system down to less than 0.5 psi for typical end
uses. Common pipe materials include cast iron, steel, and plastic (PVC, PE).

Leaks occur from pipelines as a  result of  corrosion, pipe joint  failures, and fractures.
Corrosion of the pipe material can occur internally or externally, causing  pinhole leaks, or
weakening the pipe and eventually causing  structural failure.  Transmission  pipelines are
constructed by welding pipe sections together, while in distribution pipelines the  pipe sections
are usually joined using mechanical joints. Mechanical joints are susceptible to failure through
deterioration of the sealant material and/or movement of the pipe sections.  Fractures are
breaks in the pipe resulting from externally applied forces, such as construction, heavy road
traffic, and subsidence.

Leaks from these pipeline systems may be reduced by improving  existing leak  minimization
practices  and  introducing additional  technologies and  methods that have  been proven
successful elsewhere  under similar  operating conditions.  Methods for reducing methane
emissions from leaking pipelines include improved leak detection, preventative methods such
as corrosion control and appropriate material  selection, pipeline repair and replacement, and
the use  of automatic shutoff valves.

   Leak Detection:  Methods to detect gas leaks include techniques that attempt to directly
   detect the presence of abnormally high gas concentrations, techniques to identify material
   defects in the pipeline or pipeline coating, system pressure monitoring, arid analysis of
   historical records of leaks in a given system to identify problem  areas.

   The most common detection method for both transmission and distribution systems makes
   use  of  Combustible   Gas Indicators and Hydrogen Flame Ionizers which can  detect
   concentrations (by volume in air) of approximately 5000 ppm and 1 ppm, respectively
   (Weynand, personal communication). These two pieces of equipment are used to conduct
   regular ground surveys above pipelines.  Mare recently developed  techniques include laser
   and thermal detection of leaks from remote and largely inaccessible transmission pipelines
   using helicopter-mounted equipment (Weynand, personal communication).

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OIL AND NATURAL GAS                                                             3-15
   A number of techniques exist to detect flaws in the pipe and coating material.  These
   techniques typically involve the insertion of magnetic or acoustic sensors into the pipeline
   (e.g., using specially designed pigs) and have been principally applied to large-diameter
   transmission  pipelines (AGA, n.d.).  However, similar methods have been developed to
   detect the external corrosion of small and medium diameter pipe (2-12 inches; 50-300
   mm). Magnetic and acoustic sensors have been used to detect areas of corrosion as small
   as 10 mm in  diameter (JGA,  1991).

   When  the integrity of  pipe  coating begins to fail, the amount of cathodic protection
   required to maintain minimum levels of protection must be increased. Measuring the level
   of cathodic protection is one  indication of the pipeline's level of resistance to corrosion,
   and  regulations in many nations require such periodic surveys (Hall, 1991).  Cathodic
   protection is commonly measured as the pipe-to-soil potential using a reference cell placed
   on the soil surface above the pipeline. This potential difference should be maintained at
   between -0.85 v  and -1.5 v (Stevens, 1991).  An alternative method to detect coating
   failures uses  a 220 Hz  transmitted signal between the pipeline and a magnesium  anode
   placed in the soil (Japan Gas Association, 1991).  The signal  will  flow through the
   surrounding soil from the anode to any area of the pipeline with a coating defect, up to
   2 km away.  This flow in the  vicinity of defects can be detected by a travelling receiving
   unit  on the surface.  Defects as small  as 0.1 cm2  can be detected on some coatings.

   In  addition to  gas leak and  coating defect detection methods,  many operators of
   transmission and distribution systems use historical records of leak location and frequency,
   "unaccounted-for-gas"  estimates, and pressure data to identify high risk areas of their
   pipeline networks (Miller, 1991).   Monitoring programs  range from simple statistical
   surveys to the use of sophisticated computer-based leak prediction systems. For example,
   CIMOS (Cast-Iron Maintenance Optimization System), developed under a GRI grant, uses
   data on past  leaks, details of the present system,  and economic information to prioritize
   maintenance  and replacement programs (Ahrens, 1991).  Significant  savings can be
   realized using such advanced tools to  guide system protection efforts.

   Continuous monitoring of gas systems  is often performed using automated pressure trend
   analyses. This practice monitors the temperature-corrected pressure at points throughout
   the  system, and compares this to the anticipated performance of the system based on
   past trends.  This practice can detect pressure fluctuations in the system  which may
   indicate the presence of undetected leaks.

   Preventative  Methods:   Preventing  leaks from  natural  gas systems requires selecting
   appropriate materials, and protecting the pipe materials from the effects of corrosion and
   mechanical or third party damage.  Steel is the favored material for transmission pipelines,
   being sufficiently strong to handle high pressures and more  resistant to corrosion than
   iron, although steel requires extensive protection.  Distribution pipelines, especially the
   lower pressure sections, are increasingly constructed from plastics such as PVC and PE
   which are inexpensive, easy to work with, and extremely resistant to corrosion. PVC and
   PE pipe sections can be joined by heat-fusion, reducing the number of mechanical joints
   and subsequently the number of joint failures.  Despite the trend toward using plastics in
   distribution systems, many older systems which were built with cast iron or uncoated
   steel are still  in use today.

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3-16                                                              OIL AND NATURAL GAS
   Steel and iron pipelines can be protected from the effects of corrosion with external and
   internal  coatings, and cathodic protection.   External  corrosion  is  usually  galvanic
   (electrochemical)  --  for example, rusting in ferrous  metals -  and is exacerbated by
   certain   environmental  conditions   (e.g.,  soil  types,  moisture,  external  currents),
   construction,  and material flaws.   Internal  corrosion occurs  through the action of
   contaminants in the pipeline gas, such as sulfur, hydrogen sulfide, and carbon dioxide,
   especially if water or moisture is present to act as a reaction medium. Corrosion can also
   occur  through erosion from  particulates and  liquid molecules in  the  gas stream.
   Preventative methods include the following (AGA, undated).

   •   External Coatings.  Coatings can be an extremely effective protection method.  The
       primary role of the coating is to provide a barrier to the electric currents that are set
       up between the piping and the soil and which  cause electrochemical corrosion.
       Coatings should also have good adhesion and be resistant to soil chemicals and water.
       Coating materials include coal tars, asphalt enamels, epoxy resins, plastic tapes, and
       mastics.

   •   Internal Coatings and Inhibitors.  The potential for internal corrosion increases if the
       gas  stream contains significant  concentrations of impurities  (e.g.,  S, H2S, CO2).
       Reducing the concentration of these impurities and drying  the gas is the most effective
       protection strategy. Internal coatings have been used in some situations, although
       they are more difficult to apply than external coatings. Internal coatings are also more
       likely to be eroded by contaminants and particles in the gas stream.  Inhibitors have
       been used; they  are chemicals injected into  the gas stream to reduce the corrosive
       reactivity of gas impurities.

   •   Cathodic  Protection.    Galvanic  corrosion  is the  loss   of  metal  through  an
       electrochemical process,  whereby  metal  ions are formed at an anodic area on the
       surface of the pipe and pass into solution in the surrounding soil.  Metal loss will occur
       at any point where current leaves the pipe. Corrosion can occur when two dissimilar
       metals are placed in contact, when dissimilar soil conditions exist along the pipeline,
       or when  stray currents flow through the pipeline  (e.g., from electric  rail systems,
       induced current from high voltage lines). There are two types of cathodic  protection.
       Impressed protection uses external power to force a DC current onto the pipeline
       structure  to  balance  any corrosive current flowing from  the material;  Galvanic
       protection attaches a more electrochemically active  metal (sacrificial anode)  to the
       pipeline structure.

   Pipeline Repair: Although high quality construction and protection will greatly reduce the
   rate of corrosion  of new pipelines, effective repair is a necessary aspect of reducing gas
   leaks. Repair techniques include external sleeves, clamps, and seals, and internal inserts.
   Some success has also been achieved by reconditioning pipe joint seals with  gas stream
   additives.

   High pressure transmission leaks are typically repaired  by  welding or  bolting on steel
   sleeves, which can either partially or  completely encircle the leaking pipe section (Corder,
   1991).  Large areas of corroded pipe  may be repaired by completely cutting out a section
   of pipe; smaller areas of corrosion can be repaired by grinding the affected area smooth.
   When coatings become too deteriorated to  resist corrosion the pipe must be dug up,

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OIL AND NATURAL GAS
3 - 17
   cleaned, and recoated.  Repairing leaks is often faster, less disruptive, and less expensive
   than replacing sections of pipeline.

   Low pressure distribution systems also utilize similar methods of external repair  using
   clamps and  sleeves on corroded pipe sections.  Joint leaks  in these systems can be
   repaired using a heat shrinking polyethylene tube or encasing the joint in a urethane resin
   mould  (See  Exhibits 3-3 and  3-4).  These and similar techniques  have  been  used
   successfully for many years.
                                      Exhibit 3-3
                          Joint Repair with Heat Shrink Sleeve
                                 Bell-and-spigot joint
                                                       W type repair tube
               Mastic bar
                                                      G type repair tube
                                Gas type joint
                                                                    Socket

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3 - 18
OIL AND NATURAL GAS
                                     Exhibit 3-4
                        Joint Repair with Urethane Resin Mold
                            Sealer
                Polycover
   In addition to external repairs on distribution systems, a number of new processes have
   been developed that attach an internal, impermeable  layer to the inside of the pipeline
   (JGA, 1991).  These systems greatly reduce the amount of excavation required to fix the
   leak and allow entire sections of pipeline to be rehabilitated during one repair (as opposed
   to single joints or corroded areas).  The concept of the repair is to insert flexible material,
   coated with adhesive, into the pipeline from a single excavation point and  inflate it with
   pressurized gas. This creates a smooth layer of impermeable material within the pipeline.
   (Exhibits 3-5 and 3-6).  Pipe diameters ranging from 20 to 750 mm (approximately 1-35
   inches) have been treated using this practice.  An alternative method that has been used
   successfully involves inserting PE pipe inside existing metal pipelines that have corroded
   (Pipeline Industry, 1991; P&GJ, 1990).  Diameters of 2 to 20 inches (approximately 4-45
   cm) have been repaired in this manner.  Reconditioning the sealant material in joints has
   been accomplished by adding chemicals to the gas stream (Mitchell & Sweet, 1990), and
   by using an in-pipe sensor that can apply sealant directly to the joint  (Exhibit 3-7)  (JGA,
   1991). Both methods allow full operation of the pipeline while the repair is made.

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OIL AND NATURAL GAS
                                                              3 - 19
                                             Exhibit 3-5
                           Pipe Repair with Polyamide Elastomer Layer
                            Adhesive
                        >Ť.. Layer
                         Polyamide
                         Elastomer
                           Layer
                                                               Winch
                                                        Adhesive
                                                        Layer
                         Polyamide
                         Elastomer
                           Layer
                                             Exhibit 3-6
                                   Pipe Repair with Epoxy Resin
                   Basin - Injector Tank
                                    Generator
Suction Machine       Resin Injector  Blower    compressor

                                      Winch
                                    Lining Pig     Unlng Pig \  Removing Pig
                                                    Carrying Pig

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3-20
OIL AND NATURAL GAS
                                    Exhibit 3-7
                           In-Pipe Joint Sealing Equipment
                  CompcMioc Unrt
                            ConMIPml
   Pipeline Replacement: In some cases, age, materials, and hostile environmental conditions
   make it cost effective to replace existing pipe with  more corrosion resistant materials
   rather than continue  repairs.

   Minimizing gas leakages requires a comprehensive system of monitoring pipeline conditions
   and  leak  detection,  repair, and replacement with suitable materials.  Application of
   appropriate techniques such as those described in this assessment can greatly reduce the
   leakages from some  pipeline networks.  For example, recent estimates of leakage from
   pipeline systems giye a world average of between 1  and  2  percent of  production.
   However, the wide range of regional estimates, from 0.5 percent to as high as 1 2 percent
   of production, indicates that large reductions are possible using  existing technology and
   practices  (Rabchuk,  1991; Baudino & Volski, 1991).  Feasible reductions may  be 60
   percent worldwide with some systems able to reduce up to 80 percent of emissions from
   pipeline leaks (USEPA, 1993c).

   Automatic Shutoff Valves:  Automatic shutoff valves can reduce emissions from system
   mishaps.  These valves are simple piston-spring or ball valves which close when there is
   a surge in the gas flow through the valve, and are often known as excess flow  valves
   (EFV).   In distribution systems, automatic shutoff valves are most commonly used on
   residential service lines where the risk of third party damage from excavation is greatest
   (LaShoto, 1989). EFVs have  proven effective at reducing leakage and improving  safety
   in instances of catastrophic line failure. Most designs reset themselves when the gas flow
   returns to normal.   Due  to  operating characteristics,  these devices have been less
   commonly used on lines with  pressures below several psi (Bernhardt, 1992). Automatic
   shutoff valves are also widely used in transmissions systems, at citygate and compressor
   stations, and offtake lines.

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OIL AND NATURAL GAS                                                             3-21
Pipeline networks are expensive to build and maintain.  In the U.S., a transmission pipeline can
cost up to $1 million per mile (roughly $0.6 million per km), and with proper maintenance can
stay in service 40 to 50 years. The maintenance costs for existing transmissions systems are
generally less than the cost of new pipeline.  Furthermore, much of the emphasis on system
maintenance is driven by additional important concerns such as  minimizing risk to nearby
populations.

Distribution systems are also extremely expensive to install, primarily because of the difficulty
of underground construction in urban areas.  As a result, operating companies have found it
cost-effective to emphasize extensive maintenance in order to avoid wholesale replacement.
For example, Washington Gas, a  typical U.S. distribution company, has a system protection
group of 40 people and  a budget of $5.5  million to maintain their  20,000 mile  (12,000 km)
pipeline system  (gas throughput  of 3.67  bcm).   Adequate  protection and  effective
maintenance can therefore  improve profitability by reducing repair costs and extending the
useful  lifetime of distribution pipelines.
Availability

The  techniques and  materials  discussed  here are  commercially available.   Continual
improvements are expected through research, development efforts and demonstration.
Applicability

Each  of the  approaches described in this assessment  --   leak  detection, preventative
measures, pipeline repair or replacement, and automatic shutoff valves  — have the common
goal of cost-effectively reducing gas leakage. Individual technologies  within these approaches
are applicable under  certain conditions, and  for  particular stages of  gas systems.   In
combination, these technologies provide an integrated strategy for  controlling methane
emissions applicable across a range of conditions.

Leakages in a given region are related to the length, condition, and type of pipeline system.
The largest impact on methane emissions will be the application of  improved leak detection
and repair techniques to large, high-pressure pipeline systems in relatively poor condition.
However, gas leaks are a safety hazard and a lost resource throughout all the stages of a gas
system, and continued improvements can be made in monitoring and effective repair.

These technologies are applicable in both developed and developing countries.  Developing
countries with gas infrastructures typically have smaller systems in relatively poor condition.
Here, the transfer of available technology,  and the financing to adopt it, can significantly
reduce methane emissions. Although developed countries typically have high integrity pipeline
systems,  considerable  variation  between  regions,  and  even  within  networks,   makes
improvements possible.

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3 - 22                                                             OIL AND NATURAL GAS
Barriers

Implementation of these techniques requires the availability of technology,  financing,  and
proper incentives to reduce leakages. The lack of proper economic incentives and capital are
often the cause of existing poor quality pipeline networks.
Benefits

In addition to reducing methane emissions into the atmosphere, these strategies will:

   •  Improve safety.  Methane leaks can cause fires and explosions. Reducing gas leaks
      from  pipelines, especially transmission and distribution networks,  will improve the
      safety of these systems.

   •  Reduce energy losses.  Gas leaks are lost energy, which can be recovered through
      improved construction and repair.

   •  Increase pipeline longevity.  Improved repair can increase the useful lifetime of gas
      pipelines, reducing the effective cost of such systems.
                       Improved  Leak  Detection  and  Pipeline
                       Repair

                       • methane reductions of up to 80% from
                         some pipeline  networks
                       • reduced losses
                       • reduced risks
                       • technology currently available
                       • cost-effective  technology

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OIL AND NATURAL GAS
                                                                              3 - 23
3.5  Low Emission Technologies and Practices

A number of routine operations and practices result in the release of natural gas from all
stages of the gas system.  The primary sources of these methane releases are gas-operated
pneumatic regulators and controlling devices, flanges and seals at various component joints,
and pipeline operating and maintenance procedures which vent  gas.  The techniques and
types of equipment presented here are intended to reduce these releases cost-effectively while
contributing to efficient operation.

Reduction Technology Description

Low emission technologies  and practices  which may cost effectively reduce methane
emissions include low- and  no-bleed pneumatic devices, directed inspection and maintenance
programs  at  above-ground  facilities,  and methods  for  capturing  purged  gas during
maintenance.

   Pneumatic Devices: These devices are used throughout the natural gas system to control
   the flow of gas.  They include regulators, valve operators (actuators), valve controllers,
   valve  positioners, and pressure transmitters.  Because these devices are used to control
   gas pressure and flow, engineering simplicity has led to designs which operate directly off
   of gas pressure, allowing devices to derive both their power needs and their informational
   input from the same source - gas pressure. The devices take gas directly from the pipe
   to drive their operating  mechanisms.  Numerous designs exist, many  of which allow for
   (or require) gas to be vented from the operating mechanisms once it has performed its role
   of activating the  device. The gas is typically released to the atmosphere.  However, it is
   possible to design devices which either bleed significantly less gas or  do not vent gas at
   all. Some designs reinject the used  gas back into the pipeline downstream of the device;
   others use compressed air or electric power, which must be  supplied from  an  auxiliary
   source.  Exhibit 3-8 shows representative examples of bleed rates from  high and low-Weed
   devices.
Exhibit 3-8
Pneumatic Device Bleed Rates
Device
Valve Positioner
Valve Actuator
Regulator
Bleed Rates (ft3/min)
Low-Bleed1
0.0283
0.0113
0.0064
High-Bleed2
0.628
0.085
0.268
Difference
0.5997 (95%)
0.0737 (87%)
0.2616 (98%)
1 PSI, 1990
2 PG&E, 1990

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3 - 24
OIL AND NATURAL GAS
   An initial estimate derived from extensive surveys by two U.S. gas companies indicates
   that pneumatic devices may result in annual releases of approximately 38,000 cubic feet
   per mile of pipeline (PG&E, 1990; SOCAL, 1992).  The potential for reducing emissions
   depends upon the number and design of devices in a  particular system.  In general,
   determining this will require system-specific surveys; the two U.S. company surveys
   estimated that there is roughly one high-bleed pneumatic device every 2 miles. As shown
   in Exhibit 3-8,  replacing individual devices can result in emission reductions of 80 percent
   and  higher.   Releases  from pneumatic devices  also  occur in  wellhead, gathering,
   processing,  storage,  and  distribution systems, and these areas  will  also  offer the
   opportunity for emissions reductions.

   Directed Inspection and Maintenance Programs: In addition to pneumatic devices, above-
   ground gas system facilities also contain a number of components which potentially leak
   gas.   These include flanged joints, other mechanical joints  and  connections, valves,
   pressure relief valves, and seals in pumps and compressors.

   Flanged joints rely on a gasket tightened between two flanges to maintain a gas-tight seal.
   The joint  will  leak when the gasket  is damaged or  deformed, which primarily occurs
   through poor installation, corrosion (typically from the  gas stream), or thermal  stress
   (USEPA, 1983).

   Similarly, relief valves form a  seal between the valve head and a seat, with the necessary
   pressure usually provided by a spring.  Corrosion of the head or seat, or misalignment, can
   result in leaks.

   Process valves, compressors, and  pumps all have moving  parts  -  the valve stem or
   compressor shaft - which must pass through the casing of the device. Thus, in each
   case, a seal which separates the  process fluid and the atmosphere must be formed
   between the stationary casing and a moving shaft. These seals are inherently more prone
   to wear, corrosion, and ultimately failure than simple flange gaskets or relief valve seals.
   As shown in Exhibit 3-9, although the leakage from individual components is relatively
Exhibit 3-9
Typical Fugitive Emission Rates, Component Numbers, and Facility Emissions
Component
Valves
Relief Valves
Seals
Flanges & Connections
Emission Rate
(kg/day)
0.384
3.6
5.12
0.021
Typical Number of
Components
750
12
12
3,000
Plant Emissions
(kg /day)
288
43
30
62
Source: EPA, 1983

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OIL AND NATURAL GAS	3 - 25


   small, the large number of components in a typical plant may make total plant emissions
   significant.

   Directed inspection and maintenance programs are designed to identify the source of these
   leaks, and prioritize and plan their repair in a timely fashion. Therefore, any plan to reduce
   emissions from  an  individual facility  will be comprised of a number of components,
   including a method (or methods) of leak detection, a definition of what constitutes a leak
   (e.g., a particular meter reading), set schedules and targeted devices for leak surveys, and
   allowable repair time.  These components  must be defined to institute a reliable and
   effective inspection and  maintenance program. The details of a program will depend on
   site-specific factors, and can be tailored to fit the needs and limitations  of the site.

   For example, such a program may require quarterly, monthly, or  even weekly monitoring;
   may monitor any or all  of the components (e.g., valves, relief valves, connections,
   compressor seals, and  pump seals);  may  use  portable or fixed instruments  such as
   hydrogen flame ionizers  or OVAs, visual inspection, or applied soap solutions; and may
   provide  a flexible response to leaks depending upon their magnitude and location within
   the facility.

   Analyses of typical programs have determined that cost-effective emission reductions on
   the order of 70 percent or more  are feasible (Radian,  1992;  USEPA, 1983).  These
   programs could  result in net savings.   However, diminishing  returns (i.e., decreasing
   marginal emission reductions for additional program cost) indicate that properly designed
   programs are necessary  to maximize benefits and overall cost-effectiveness.

   Capturing of Purged Gas:  Routine maintenance work on transmission pipelines  requires
   a large  reduction in gas  pressure in the  pipeline section to be repaired to ensure safe
   welding conditions.  Typically, a pipeline section undergoing repairs is isolated and vented
   to reduce pressure, resulting in the release of the gas to the atmosphere. However, it is
   technically feasible and may be cost-effective to use a portable compressor unit to transfer
   this gas to another section of the  system.

   A Canadian gas pipeline operating company with  over 8,000 miles  of  pipeline has
   successfully used two truck-mounted  turbine-gas compressor units to capture gas that
   would otherwise have been vented during maintenance (NOVA, 1985).  Each unit consists
   of a natural  gas fired turbine (rated at  between 3 and  4 MW), a gas compressor (with a
   compression ratio of 5:1), necessary auxiliary equipment such as air intake and  exhaust
   filters and silencers, fuel gas filters, electric power units, control stations, all mounted on
   a standard "lowboy" trailer. A support truck carries the necessary pipe and fittings to tie-
   in the compressor unit to the pipeline.  A total crew of 3 or 4 is needed to transport, set-
   up, and operate the unit. The result  is a fully-mobile, self-contained compressor  unit
   which can reach any point in the system within 2 to 10 hours, and  set-up in 4 hours.

   In operation, the portable unit can evacuate a 20 mile section of 30 inch pipeline from a
   pressure of 800  psi  down to 160  psi in approximately 10 hours. The compression ratio
   of 5:1  means that  the  pipeline cannot be  completely evacuated;  the  remaining gas,
   approximately  1/5 of the total volume, is then vented.  However, emissions are reduced
   by roughly 80 percent. Exhibit 3-10 shows the amount of gas saved per mile for different
   size pipelines.

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3 - 26
OIL AND NATURAL GAS
Exhibit 3-10
Volume of Gas in Various Size Lines at Different Pressures; Volume of Gas Saved per
Mile of Pipeline
Pipe Size
(inches)
10
12
16
20
24
30
36
42
MSCF of Gas/Mile
at 800 psi and
60°F
186.22
267.41
431.72
687.53
1003.27
1587.70
2305.53
3157.37
MSCF of Gas/Mile
at 1 60 psi and
60°F
35.90
51.55
83.24
132.55
193.43
306.11
444.50
608.74
MSCF of Gas
Saved per Mile
150.32
215.86
348.48
554.98
809.84
1281.59
1861.03
2548.63
Source: NOVA, 1985 ,
Costs

These practices and technologies all generate cost savings through capturing gas or otherwise
reducing gas leakage, thereby offsetting program costs.  In some cases, depending on site
specific factors, these cost savings can recoup capital and operating costs (USEPA, 1 993b).

   Low-bleed  Pneumatic Devices:  The cost-effectiveness  of replacing  existing  devices
   depends on several factors, including the avoided cost of lost gas, and the incremental
   cost of low/no-bleed devices above that of high-bleed equipment. In some cases, lower-
   bleed  devices are less expensive than other designs.  Some success has already been
   achieved in replacing  devices where expected avoided costs from preventing gas leaks is
   larger than incremental costs. For example, a U.S. gas company installed low- or no-bleed
   gas control station equipment at five locations, and expects to save over 800,000 mcf of
   gas over a ten year period, with direct benefits of over $4 million  (Cowgill, 1991).
   Cumulative incremental investments were in fact negative, indicating reduced replacement
   costs  over high-bleed devices for these applications.

   Directed Inspection &  Maintenance Programs:  Experience  in the US  indicates that
   programs  can achieve  per component monitoring costs of $0.30 to $1.00; these costs
   are based on monitoring rates of 200 to 800  components per  man-day (USEPA, 1983).

   Capturing Purged Gas:  The best available information on the costs  of capturing natural
   gas vented during pipeline repair is from the Canadian experience. The two Canadian units

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OIL AND NATURAL GAS                                                            3 - 27
   were deployed in 1979 and 1 983, at a cost of 2.3 million Canadian dollars and 4.5 million
   Canadian  dollars respectively.  From 1979 to 1984, 490 to 760 mmcf of gas were
   captured annually, for net savings of 750,000 to 1,560,000 Canadian dollars.  Annual
   operating costs ranged from 102,000 to 285,000  Canadian dollars (NOVA, 1985). These
   costs and savings are highly dependent upon the  average volume of gas released during
   pipeline blowdowns  and the number of blowdowns that are actually planned,  thereby
   allowing for deployment of the units.
Availability

Designs for pneumatic devices which bleed less gas have been developed  and installed in
numerous applications. In many cases these designs are not marketed explicitly as low-bleed
designs, and choosing these designs requires a certain level of awareness on the part of those
planning maintenance. However, the availability of low-bleed devices is not seen as a barrier
to implementation.

The technical equipment for directed inspection and maintenance, such as portable or fixed
monitoring devices, is readily available.  Furthermore, there is a growing body  of experience
in implementing these programs.

Trailer-mounted turbine-compressor units  are  not commonly available as integral units.
However, the individual components  are  widely  available in  a variety of  configurations,
requiring  custom work 6nly for the trailer mounting.  (The Canadian gas company worked
closely with the compressor manufacturer to install the components satisfactorily  on  the
trailer.)
Applicability

In general, the options presented here are suitable for most natural gas systems.

   •   Low-bleed pneumatic devices are applicable in almost all situations where high-bleed
       devices are currently installed. Since their average lifetime is about seven years before
       being  replaced,  significant methane reductions  could  be expected over the next
       decade.  However, there are some applications of pneumatic devices where the high-
       bleed feature is necessary for system performance.

   •   Directed  inspection and  maintenance  programs  are  applicable for  any  surface
       installation, especially processing and gathering facilities, compressor stations, and gas
       transfer  points.   These facilities contain  numerous  connections, seals,  and other
       components which emit gas. Regular planned inspection and timely repair can reduce
       these emissions.

   •   Capturing  otherwise  vented  gas is  most likely to be applicable on  transmission
       pipelines, which have large internal volumes and high pressures.  However,  there is
       potential for similar (scaled down) equipment to hot-tap into distribution or service lines
       and capture otherwise vented gas.

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3 - 28                                                              OIL AND NATURAL GAS
Barriers

These  technologies have proven  successful and  cost-effective in a variety of situations.
Barriers to wider implementation include the availability of information, the existence of
necessary incentives to save gas, and inertia in accepting new practices.

Operators often  do not realize the magnitude of emissions that may be occurring at their
facilities, and the overall economic cost of these losses.  In other cases the cost of lost or
unaccounted for  gas is not fully born by the facility operator, weakening the incentive to alter
operating  procedures.  In general, there is resistance to change and  new equipment and
procedures only  slowly gain acceptance.
Benefits

In addition to reducing methane emissions into the atmosphere, these strategies will:

   •  Improve safety:  Methane leaks cause fires and explosions.  Reducing gas leaks will
      improve the safety of these facilities.

   •  Reduce energy losses:  The installation  and use of more advanced technologies will
      reduce the energy otherwise lost through gas leaks.

   •  Improve air quality: Reducing gas losses reduces the effect that such emissions have
      on local  air quality.
                       Low Emission Technologies and Practices

                       • methane reductions of up to 80% in
                         typical facilities and applications
                       • reduced losses
                       • cost-competitive practices
                       • technology currently available
                       • improved air quality and safety

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OIL AND NATURAL GAS                                                          3 - 29


3.6   References


Contributions were made by:

   Ed Caldwell, Environment Canada, Canada

   Bruce Craig, Oil and Natural Gas Systems, USEPA, USA

   Charles Ervin, Southwest Research Institute, USA

   Katsuya Sato, Global Environment Department, Japan Environment Agency, Japan

   Gordon Weynand, Oil and Natural Gas Systems, USEPA, USA


Additional information may be found in the following:

Ahrens, Frank (1991),  "Getting a Fix on Repairs," in American Gas. July 1 991.

AGA (American Gas Association), Gas Engineering and Operating Practices Series, Arlington,
Virginia.

Banerjee, N.  (1991), "Compressor Scheme Will Reduce Gas Flaring in India's Oil Fields,"  in
Oil and Gas Journal.  April 22 1991.

Barns,  David W. and J.A. Edmonds (1990), An Evaluation of the Relationship Between the
Production and Use  of Energy and Atmospheric  Methane  Emissions, U.S. Department  of
Energy, Washington, D.C.,  DOE/NBB-0088P.

Baudino, Mario and Edward Volski (1991), Abating Methane Emissions by Reducing Natural
Gas Leakages, presented at the International Symposium on Environmentally Sound Energy
Technologies and their Transfer  to  Developing  Countries  and  European Economies  in
Transition, Milan, Italy, 21-25 October, 1991.

Bernhardt, Todd (1992), "Examining EFVs," in American Gas, May 1992.

Corder, Ian (1991), "On-Line Repair Using Epoxy-Filled Shells," in Pipeline Industry, July 1991.

Cowgill, R.M. (1991), Pacific Gas and Electric Company, personal communication, September
26, 1991.

Hall, Charles (1991), "Computerized  System for Corrosion Control," in Pipeline and Gas
Journal, October 1991.

Japan  Gas Association (JGA)  (1991), "Catalogue of Technological  Options for Methane
Emissions of Natural Gas Systems in Japan," submitted by JGA October 18, 1991.

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3 - 30                                                          OIL ANO NATURAL GAS
LaShoto, Paul (1989), "Automatic Shut-Off Valves," in Pipeline and Gas Journal. November
1989.

Miller, Robert J.  (1991), "Maintaining a Cast Iron System," in  Pipeline and Gas Journal.
September 1991.

Mitchell,  Catherine and Jim Sweet (1990), A Study of Leakage from the U.K. Natural Gas
Supply System with Reference to Global Warming, prepared for  Greenpeace U.K. by Earth
Resources Research, London, England.

NOVA (1985). Portable Pipeline Evacuation Compressor, prepared by John Matemisi, Alberta,
Canada, 1985.

PG&E (1990), Unaccounted for Gas Project •• Summary  Volume. Pacific Gas and Electric,
Research and Development, San Ramon, CA, 1990. GRI-90/0067.1.

Pipeline and Gas Journal (Staff) (1990), "Renovating the  Paris Gas System'" in Pipeline and
Gas Journal, November 1990.

Pipeline Industry (Staff) (1991), "PE Pipe Insertion Through Cast-Iron Main Saves Money," in
Pipeline Industry, July 1991.

Rabchuk, V.  I., N. I. Ilkevich,  & Y. D. Kononov (1991), A Study of Methane Leakage in the
Soviet Natural Gas Supply System, prepared for US DOE/EPA, November 1 991; Washington,
DC.

Radian (1992), US Natural Gas  Industry Methane Emissions  Mitigation and Cost-Benefit
Analysis. Austin,  TX.

SOCAL (Southern California Gas Company) (1 992), Unaccounted  for Gas Project - Summary
Volume, in preparation, Southern California Gas, Los Angeles, CA, 1992.

Soot, P.M. (1991), "Power Generation Using Small Internal Combustion Engines," prepared
for ICF Inc.,  1991.

Stevens,  Ralph W. (1 991), "Cathodic Protection Vs. Recoating," in Pipeline and Gas Journal.
March 1991.

Sturgill, C. (1991), "Power Generation: On-Site Use and  Sale to Utilities," prepared for ICF
Inc., April 1991.

US DOE (US Department of Energy) (1992), International Energy Annual - 1990. DOE/EIA-
0219(90), Washington, DC.

USEPA (United States Environmental Protection Agency) (1983),  Equipment Leaks of VOC
(Volatile Organic Compounds) in Natural Gas Production  Industry - Background Information
for Proposed Standards, US Environmental Protection Agency, Research Triangle Park, NC,
December 1983,  PB84-155126.

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OIL AND NATURAL GAS                                                          3-31
USEPA (1993a), Anthropogenic Methane Emissions in the United States. Report to Congress,
USEPA/OAR (Office of Air and Radiation), Washington, DC.

USEPA (1993b), Opportunities to Reduce Methane Emissions in the United States. Report to
Congress (review draft), USEPA/OAR, Washington, DC.

USEPA (1993c), Options for Reducing  Methane Emissions  Internationally -  Volume  II:
International Opportunities for Reducing Methane Emissions. ReporttoCongress, USEPA/OAR,
Washington, DC.

Webb,  Mike (1992), personal communication, May 8, 1992.

Zebelean, D.C. (1991), "Compressor-Fuel Engine Analysis Locates Inefficiencies," in Oil and
Gas Journal. August 12,  1991.

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CHAPTER FOUR
COAL MINING
4.1   Background

Methane Production. Storage, and Emissions

Methane is produced during coalification (the process of coal formation) and remains trapped
under pressure in the coal seam  and  surrounding rock strata.  This trapped methane is
released during the mining process when the coal seam is fractured.  Methane released in this
fashion will escape into the mine works, and will eventually be emitted into the atmosphere.

The production of methane during coalification may exceed the adsorptive capacity of the
coal.  For example, although the highest gas content measurements for U.S. anthracite coal
are only 21.6 cubic  meters per metric ton,  180 cubic meters of methane may be produced
during coalification (Diamond et al., 1986). As a result, significant quantities of methane seep
into and are stored in the rock surrounding the coal seam. This methane seeps back into the
mine working as the coal  is mined. Mine air containing methane is removed from the mine
workings, and is generally vented directly into the atmosphere.

The quantity of methane emitted per tonne of mined coal depends upon several characteristics
of the coal, the most important  of which  are:  1) gas content,  2) permeability  and gas
diffusion rates, and 3) method of mining.  The gas content of coal depends upon its rank and
geological history.   Coal  rank  is  a measure of the degree of coalification;   as coal rank
increases, the amount of  methane produced also increases (see Exhibit 4-1).  Furthermore,
higher ranks of coal have greater adsorptive capacities and will tend to contain more gas.
Because pressure increases with depth, deeper coal seams generally contain more methane
than shallow coal seams of similar rank. Thus, deeper mines with coal of a higher rank will
typically contain larger quantities  of methane.

Permeability and diffusion rates are also important because they determine how quickly gas
can migrate through the coal and  into  the mine workings. After coal is mined, the strata
overlying the mined  coal are allowed to cave in, causing the formation of a rubbleized area,
termed a "gob."  This fracturing increases the permeability of the methane-containing strata
and facilitates the release of methane.  Because more coal is removed during longwall mining
and fewer pillars remain,  the  caving  associated  with longwall mining is generally  more
extensive, and thus methane  released per  tonne of coal is generally higher with longwall
mining than with room and pillar mining.
Methane Recovery and Utilization Strategies

Techniques for removing methane from underground mine workings have been developed
primarily for safety reasons,  because methane  is highly  explosive in  air concentrations
between 5 and 15 percent.  These same techniques can be adapted to recover methane so
that the energy value of this fuel is not wasted. Where methane utilization is combined with
recovery, methane emissions into the atmosphere are reduced.

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4- 2
                                                                         COAL MINING
Important factors when considering options for reducing methane emissions from coal mining
are: the geologic and reservoir characteristics of the coal basin; mine conditions and mining
method;  current mine gas recovery systems;  potential gas quality and  use options; and
technical and economic capabilities. In particular, the recovery method largely determines the
quality and  quantity of gas recovered,  which in  turn  determines the possible  utilization
options.  Developing uses for recovered methane is required if emission reductions are to be
achieved. The sale and/or use of methane can offset the costs of recovery in certain cases.
Furthermore, improving methane recovery techniques can result in  safer, more productive
mines, with  lower ventilation costs (Dixon, 1987).
                                    Exhibit 4-1
                          Coal Rank and Methane Production
                1600
Yield cf/ton
  3200
                                                           Coal Rank
4800
5400
                                                          High
                                                          Volatile
                                                          Bituminous
                                                          Med-volatile
                                                          Bituminous
                             91           136
                             Yield m3/ton
                                                   z
                                                   o
                                                   n
                                                   m
                                                   o
                                                   o
                                                                             33

                                                                             Z
                                                                             *
  Source: USEPA, 1990.

-------
COAL MINING
                                4 -3
                                      Exhibit 4-2
                    Coal Mining and Methane Recovery Techniques
                             Longwalt Mining
                              / Machine
                                                    Train
                                                   haulage
            (a) Longwall Mining
(b) Room-and-pillar Mining
            (c) Vertical Gob Well
(d) Vertical Degasification Well
            (e) Cross Measure and
                Horizontal Boreholes
(f) Surface Equipment

-------
4 - 4                                                                      COAL MINING
Because the quality of gas that is recovered determines the possible gas utilization options,
each of the four techniques presented  here  is a complete  project  based on  a  particular
recovery method and its associated  utilization options.  Additionally, these  strategies are
structured according to technological and economic criteria and overall applicability. The four
strategies presented are:

   •   Enhanced Gob Well Recovery;
   •   Pre-Mining Degasification;
   •   Ventilation Air Utilization; and
   •   Integrated Recovery.
   Enhanced Gob Well Recovery: This strategy recovers methane from the gob area of a coal
   mine -- the highly fractured area of coal and rock that is created by the caving of the mine
   roof after the coal is removed.  Gob areas can release significant quantities of methane
   into the mine,  and if  this gas is  recovered before entering  the mine,  ventilation
   requirements can  be reduced  (see Exhibit  4-2,  Coal Mining  and  Methane Recovery
   Techniques). Typically, gob gas is diluted  by mine air during production so a medium
   quality gas is obtained (300-800 Btu/cf;  11-29 MJ/m3). This type of gas can be used in
   a variety of applications, including on-site power generation, gas distribution systems, and
   industrial heating.  Enhanced gob well recovery can involve in-mine and/or surface wells
   using existing technology  that is currently employed in many countries. In many cases,
   the capital requirements for methane recovery are low compared to the amount of gas that
   may be produced.  The capital cost associated with gas utilization can vary significantly,
   being quite high for electricity generation, particularly where gas turbines  are used.

   Pre-Mining Degasification:  This strategy recovers methane before coal is mined.  Pre-
   mining degasification can be attractive where geologic conditions are appropriate because
   the methane is removed before the air from the mine workings can mix with it.  Pre-mining
   degasification typically recovers a  higher quality gas (900-1000  Btu/cf; 32-37  MJ/m3)
   which can be used as a chemical feedstock in addition to being used for power generation
   and industrial or residential applications.  Pre-mining degasification can be an in-mine or
   surface operation.  When  done  inside  the mine, boreholes can be drilled anywhere  from
   six months to several years in advance of mining. Surface drilled vertical wells can  be
   drilled anywhere from  2  to  more than  10 years in  advance of mining.   Pre-mining
   degasification requires more advanced technology and equipment than enhanced gob well
   recovery, and therefore has higher  capital costs.

   Ventilation Air Utilization:  Most mine gas is released to the atmosphere in the ventilation
   air used in the mine. Ventilation, necessary in underground coal mines for safety reasons,
   is achieved with large fans which blow air through the  mine.  The recovery technology is
   basic, but the operating costs of running the fans can  be high if the  mine is gassy.  The
   methane content of the vented air must be  below 5 percent for safety reasons, and is
   frequently as low as 0.5 percent to comply with relevant regulations. In spite of its low
   concentration,  it appears that  there may be  opportunities to use ventilation air  as
   combustion air in turbines  or boilers (Granatstein etal.,  1991; ESA, 1991).  However, the
   technical and economic feasibility has not yet been demonstrated.

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COAL MINING                                                                      4 - 5
   Integrated Recovery: The most significant methane emission reductions are likely to occur
   by employing a combination of methane recovery options. Indeed, many US coal  mines
   currently use a combination of in-mine and surface recovery methods both before mining
   and from  gob areas (Soot, 1990).  The technological and capital requirements of such
   integrated systems are likely to be moderately high, but it is possible that the additional
   opportunities for gas utilization,  as well as the enhanced mine safety, could justify the
   required investment.

Exhibit 4-3 summarizes information  on these four coalbed methane recovery and utilization
strategies.  The four strategies are  described in more detail in the individual technological
assessments.

The assessments consist of the following sections:

   • Recovery Technology Descriptions;
   • Utilization Technology Descriptions;
   • Costs;
   • Availability;
   • Applicability;
   • Barriers; and
   • Benefits.

-------
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-------
COAL MINING                                                                     4 - 7
4.2   Enhanced Gob Well Recovery

Enhanced Gob Well Recovery is an approach that seeks to improve and augment methane
recovery techniques that are already in place at a mine so that recovery is more efficient. This
strategy builds on local experience and methods of operation.

Gob areas consist of fractured rock and coal that have collapsed into mined-out areas.  Since
these areas are considerably more permeable than intact coal and rock, methane stored above
and below the coal seam is released during and after the creation of this gob area.  The
proximity of the gob  area  to the lower pressure  of  the mine can result in  the  flow  of
significant quantities of methane into the mine workings. This released methane is typically
emitted into the atmosphere, rather than being utilized.

In many deep coal mines, methane concentrations in the mine air cannot be maintained at safe
levels through ventilation alone without reducing coal production.  Coal mine operators seek
to maximize the amount of coal they can safely produce by employing additional methane
removal  techniques to supplement  ventilation.  These systems are quite common; for
example, 100 state-owned underground mines in China, 18 Polish mines, at least 145 Russian
and Ukrainian mines, and about 35 U.S. mines use some type of advanced methane recovery
technique (JP International,  1990; Pilcher et al.,  1991; Zabourdyaev, 1992;USEPA,  1993a).
Mines  in many other countries — including Czechoslovakia, Germany, Canada, the United
Kingdom, Japan, Australia,  South Africa and India - also use these techniques.

The most common of these techniques are performed during mining operations (as opposed
to pre-mining degasification), and include vertical  gob wells  drilled from the surface and
boreholes drilled from  in-mine workings into gob areas.  Enhanced  Gob Well Recovery will
improve the efficiency of existing recovery systems and expand the use of these techniques.
Based on reported emissions data from a variety of countries, it appears that anywhere from
10 to 50 percent of the total methane emissions may be recovered with these technologies,
depending upon the site-specific  geologic conditions,  and the design of the degasification
program.
Recovery Technology Description

The two techniques described here are cross-measure boreholes and vertical gob wells. These
techniques are carried out in conjunction with active mining operations, and, as shown in
Figure 2, they recover gas from the caved-in or "gob" area. Removing methane from the gob
area can be technically complex and must be integrated with mining operations. Because the
gob area is located within the mine and is surrounded by ventilated mine workings, medium-
quality gas is typically produced using these techniques.

   In-Mine Boreholes:  Boreholes have been  used in coal mining since the 1800's. This
   technology consists of drilling boreholes from the mine workings into unmined areas of the
   coal seam and surrounding rock. Cross-measure boreholes, angled into the rock and coal
   strata above and below the mine workings, are used to recover methane from the gob
   areas.  These boreholes are typically tens to hundreds of meters in length. The boreholes

-------
4 - 8                                                                     COAL MINING
   are connected to an in-mine vacuum piping system, through which recovered methane is
   transported out of the mine (USEPA, 1990).

   To maximize  gas production the boreholes are operated under negative pressure, and in
   the process mine air is drawn into the gob area and ultimately into the gas stream.  The
   quality of gas recovered will vary greatly depending on such factors as local geology, coal
   rank, and the efficiency  of the recovery system.  Previous experience indicates that
   medium quality gas (300-800 Btu/cf; 11-30  MJ/m3) will be recovered.  Total methane
   production will vary according to local factors and the length of the borehole.   Various
   experiments in the U.S. have yielded production rates of 800 m3/day to 2,800 m3/day for
   boreholes of 100 to 200 meters in length (Garcia and Cervik, 1985;  Baker et al., 1986).
   Typically, 20 to 50 percent of the methane contained in the  gob area may be recovered
   through the use of in-mine boreholes (USEPA, 1990).

   Japan and other countries practice a variant of this method of gob well recovery (Higuchi,
   personal communication).  When a longwall panel (typically 150-250 m wide and several
   hundred meters long; 500-825 ft by 3000 ft) is completed,  the  resulting collapsed gob
   area is sealed to reduce methane leakage into the mine workings.  A steel pipe is inserted
   into this sealed area and connected to an in-mine piping system enabling large quantities
   of methane to be recovered.

   Vertical Gob Wells: A second method of  removing the methane  from the gob area is to
   drill vertical wells into the gob  from the surface. Prior to mining, wells are drilled to a point
   2 to  15 vertical meters above the coal seam (USEPA, 1990).  As the working face passes
   under the well, the methane-charged coal and rock strata collapse to form the gob.  The
   methane can be  recovered under  vacuum,  rather than  being  released  into  the mine
   workings.  The main  advantage of this  technique is that it avoids the difficulties of
   working in the mine, and possibly interfering with the mine operations.  However, the use
   of vertical gob wells requires relatively advanced drilling techniques and may be  difficult
   to integrate with multiple seam coal extraction.

   Typically, the gas  quality is similar to that of the in-mine systems,  although it  may be
   easier to  produce high  quality  methane using vertical  gob wells.   As with  in-mine
   boreholes,  surface gob wells can be operated under negative pressure, drawing mine air
   into the gob and diluting the recovered methane. Through careful monitoring of  the gas
   quality, and adjustment of the vacuum pressure, it is possible to maintain a higher and
   more consistent gas quality (one  company's mines in Alabama, U.S.,  produce gas with
   over 95 percent methane from the gob wells) (Dixon, 1989). Over time, the quality will
   decline as air from the mine workings seeps into the gob  area.  Vertical gob wells alone
   may recover 30 to 40 percent of the methane contained in the gob area (USEPA, 1990).
   Typical production figures are 2,800 m3 per day (100,000 cf), but are highly dependent
   on site-specific factors (Baker at al., 1988;  USEPA,  1990). One mining operation in
   Alabama, U.S., recovers 849,000 m3 per day from 80 surface gob wells (Dixon, 1987).

The choice between  in-mine and surface recovery techniques  depends upon site-specific
factors that affect how cost-effective and  appropriate these  two techniques are for a
particular mine. These factors include mine depth, mining method, drilling costs, availability
of technology, surface activities,  and terrain.

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COAL MINING                                                                      4 - 9
Where the techniques described above are already in place, it is often possible to increase the
recovery efficiency and improve gas quality through improved drilling  techniques, improved
pumping and in-mine piping systems, and the use of more advanced monitoring and control
systems.

    Drilling Techniques: Inappropriate drilling technology can slow the drilling of gob wells and
    boreholes to the  point where  it is no longer  feasible to implement these technologies.
    However, adequate technology currently exists, and is in use in many countries. Where
    improvements would be useful, those countries with oil and gas industries may be able to
    adapt existing drilling capabilities;  otherwise  this technology must be imported, raising
    project costs.  Drilling improvements may include the  use of diamond  bits  for rock, and
    the capacity to drill bore holes with larger diameters and longer lengths.

    In-Mine Piping:  In some mines, the overall quality of  the in-mine  piping system can be
    improved to reduce leakage. One important improvement is to ensure the integrity of the
    piping by installing safety devices to shut down the system  in the event of mining
    accidents. In some cases, increasing the capacity of the piping system will increase the
    quantity of methane that can feasibly be recovered.

    Pumping: Gas pumps with higher pressures and greater capacities increase the efficiency
    of methane  recovery.   In general  any improvements in  reliability and lifetime will be
    beneficial.

    Monitoring:  The  placement and spacing  of  boreholes and vertical wells  is extremely
    important for the effectiveness of a recovery  program. Monitoring the recovery system
    in operation  can  also improve the efficiency of the system.   Both  of these important
    factors involve  relatively low-technology solutions. For example,  each borehole can be
    equipped with  a  shutoff device that activates when the gas quality drops below 25
    percent CH4. Many monitoring techniques are currently available  and in use.
Utilization Technology Description

There are four main options for utilizing medium quality gas:  on-site power generation with
turbines, on-site power generation with internal combustion engines, sale to a distribution
system, and industrial use in boilers. In each case, the sale or direct use of energy can often
justify the initial investment in generating equipment.  The anticipated gas flow rate and gas
quality (e.g., impurity levels and methane concentration) are particularly important in selecting
the appropriate utilization option.

    On-site Gas Turbines:  Gas turbine systems can use medium quality gas to generate power
    for on-site use or for sale to nearby electricity users or supply companies.  Selection can
    be made from among several gas turbine system configurations, depending  on factors
    such as energy needs, technical capabilities, and capital  availability.

    Simple cycle gas turbine systems can operate with efficiencies ranging from 1 5 to 40
    percent, increasing in efficiency as size increases (Williams and Larson, 1990).  Combined
    cycle turbine systems  use  the exhaust heat from a gas turbine to produce steam  in a
    boiler, which is then used to power a steam turbine. Alternatively, or in addition, waste

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4-10                                                                    COAL MINING
   heat can be used for various local heating needs (i.e., co-generation).  When combined
   with a  heat recovery  system, energy efficiencies can exceed 80  percent.  Energy
   efficiencies  in the region of 50  percent  can  be achieved in combined cycle systems
   without heat recovery.

   Gas turbine  systems have certain properties which make them a particularly attractive
   utilization option for coal mines:  1) turbines come in a range of sizes, depending on the
   required  generating capacity; 2)  the turbine combustion process is continuous, which
   results in a high combustion efficiency and greater tolerance to deviations in fuel quality;
   and 3) waste heat from the turbines can be used for industrial purposes, such as coal
   drying  at the mine.  Gas  turbines usually require higher gas flows  in  order to  be
   economical, and typical applications at coal mines  would use one or more 1 to 5 MW
   turbines  (Sturgill,  1991).   Gas turbines  are  running on  medium  quality mine gas in
   Australia, China, Germany, and Japan.

   On-site  Internal  Combustion  Engines:   Internal combustion  (1C)  engines provide  an
   alternative method for  burning  medium  quality mine  gas for  power  generation.  A
   stationary engine can turn a generator  which produces electric energy, with operating
   efficiencies ranging from 25 percent to 35 percent. With a heat recovery system, energy
   efficiencies can reach as high as 80 percent (Williams and Larson, 1990). 1C engines are
   widely used  to generate power from medium quality gas, and they tend to be better suited
   than turbines to low gas  flows or irregular use.  Although  variations in  methane
   concentration previously caused some problems with the use of mine gas in 1C engines,
   modern integrated control systems allow fluctuations in gas quality to be accommodated
   in the operation in the engine (Pilcher et  al., 1991). 1C engines are available in sizes from
   around 30 kW up to several MW, but are  typically rated at several  hundred kW.

   Gas Distribution System:  In developing countries, as well as some other regions, medium
   quality mine gas can be distributed in residential and commercial gas supply networks and
   used for cooking and heating.  Many mines in China, for example, currently transport
   medium quality methane short distances  to residential consumers (JP International, 1990).
   The system  can  be very simple,  consisting  of pipes and rudimentary stoves which can
   burn natural gas.  High efficiency gas burners  will use fuel more efficiently and will also
   reduce the emissions of uncombusted methane. Care should be taken in the construction
   of new pipelines so that leakage is minimized.

   In some countries, such as Poland, it may  also be possible to distribute coalbed methane
   in low-methane  natural gas (LMNG) or  coke-oven gas pipeline systems (Pilcher et al.,
   1991). These medium quality gas pipelines are extremely attractive because they can be
   used to transport gas that would not otherwise be  considered  "pipeline quality,"  (e.g.,
   pipeline quality gas must be 95 percent  methane in  the U.S.)  In general, these types of
   systems transport gas that is 50  to 70 percent methane.

   Industrial Use: Medium quality gas may also be  used as a combustion fuel for industrial
   boilers.   The gas can  be supplied to  nearby industries and  used on its own  or in
   conjunction  with other fuels in a boiler.  Medium quality methane from coal  mines is used
   by local industries in several countries,  including Czechoslovakia, Poland, and Ukraine.
   The  use of medium quality  gas may  require  minimal  conversion of existing  boiler
   equipment, but in many cases requires no significant changes.

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COAL MINING                                                                     4-11
Costs

Preliminary figures for the costs of recovery and utilization options are presented below. The
prices are U.S. figures and do not reflect the added cost of importing technology, lower labor
costs in developing countries, or other local factors. All  costs are in U.S. dollars.

   Recovery Costs:  Recovery  costs will vary depending on the recovery technique being
   used and various site-specific factors such as mining depth and coal permeability.  Per well
   recovery costs are presented below for vertical gob recovery projects.  The full costs
   associated with hypothetical U.S. vertical gob well and cross-measure borehole  projects
   are also summarized. The costs are based on U.S. conditions and U.S. state-of-the-art
   technology. Simpler technologies may require less capital investment, but may also incur
   larger operating costs.  Furthermore, improvements  in existing  technology  may be
   significantly less expensive than indicated by the costs below.

   •   Vertical Gob Wells.  Exhibit  4-4 summarizes the potential range of capital costs on  a
       per well basis for vertical gob wells in various U.S. coal basins.  The number  of wells
       drilled by a given mine will depend on site specific conditions. In addition, the capital
       costs for vertical gob wells vary between and within coal  basins due to differences in
       well depths (drilling costs), equipment costs, and  costs for surface rights (which can
       vary significantly on a site-specific basis depending on terrain and land use in the area).

       Vertical gob wells are assumed to have fixed annual operating costs associated with
       recovering -- but not utilizing -  methane.  Recovery costs include all manpower,
       materials, and  power costs for the operations, maintenance, and administration of
       producing wells. The likely  range of operating costs for vertical gob wells is  $4,000
       to $8,000 per well (ICF,  1992).

       Project costs for hypothetical  methane recovery projects using  vertical gob  wells in
       different U.S.  coal basins have been estimated by the U.S. Bureau of Mines (Baker,
       1988). These costs are for complete methane recovery projects associated with five
       years of coal mining.  Specific characteristics of the projects, such  as the depth of the
       wells, the number of  wells per longwall panel, the rate of mining, and the productive
       life of the wells, were assumed to vary by coal basin. Estimated project costs include
       all planning, site development, equipment, drilling and subsequent operating costs, and
       general overhead for  each project.  These costs include only the recovery portion of
       the project. Exhibit 4-5 summarizes the total costs of these hypothetical projects in
       the selected coal basins (Baker, 1988).  No gas production values are provided, so the
       USBM study cannot be used to determine production  costs on a $/mcf basis.

       Based on potential capital and operating costs, however, and with  some assumptions
       about gas production over the life of the wells, it is possible to make rough estimates
       of methane recovery costs in terms of $/mcf.  In general, the costs for vertical gob
       well recovery could range from a low of $0.50/mcf to levels of $3.00/mcf  or higher.
       Some  U.S. vertical gob well projects have reported costs on the order of $0.75/mcf
       to $1.00/mcf, not including  the value of cost savings in the mining operations.

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4 - 12
COAL MINING
Exhibit 4-4
Capital Costs for Gob Wells (per well costs)
Basin
Central
Appalachian
Northern
Appalachian
Illinois
Warrior
Western
Low
$80,000
$60,000
$50,000
$90,000
$100,000
Medium
$130,000
$110,000
$100,000
$140,00
$150,000
High
$190,000
$170,000
$160,000
$200,000
$210,000
Note: Capital costs for gob wells include all costs for surface drilling rights, site development and
preparation, and costs for drilling, completing and equipping the wells.
Sources used to develop ranges: 1) USEPA 1990; 2) ICF Resources, 1990b; 3) Baker, Garcia, and Cervik
Cost Comparison of Gob Hole and Cross-Measure Borehole Systems to Control Methane in Gobs (USBM
Report of Investigations, 1988).
Exhibit 4-5
Total Vertical Gob Project Costs in Various U.S. Coal Basins
Location
Central Pennsylvania
Northern West Virginia
Southern Virginia
Northern Alabama
Capital Cost
($ millions)
1.0
1.1
6.1
3.8
Operating Cost
($ millions)
0.3
0.3
0.2
0.5
Project Cost
{$ millions)
1.3
1.4
7.2
4.2
Note: Costs are undiscounted and represent the sum of all costs incurred over the life of the project,
which was assumed to be five years and one year of development.
Source: Baker, 1988.
      Cross-Measure Boreholes.  In general, cross-measure borehole recovery projects will
      have lower capital costs but higher operating costs than vertical gob recovery, as a
      result of the greater complexity of drilling within the mine. Cross-measure boreholes
      are not a common degasification technique in the United States, although they are
      widely used in other countries.

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COAL MINING
                                                                               4 - 13
       No costs from actual U.S. cross-measure boreholes projects have been published. In
       general, costs  for  in-mine piping systems  will be similar to those for horizontal
       boreholes, or about $5/foot of pipe (ICF Resources,  1990a).  Drilling costs may be
       lower than for horizontal boreholes, however, because the holes are shorter and less
       powerful drilling equipment can be used.  On the other hand, the shorter cross-measure
       boreholes require proportionately more setup time and, because they are drilled through
       hard strata rather than coal, could have slower penetration and higher  drill bit wear
       rates.

       The U.S.  Bureau of Mines has investigated the costs of hypothetical cross-measure
       boreholes systems in four U.S. locations: central Pennsylvania, northern West Virginia,
       southern  Virginia, and northern  Alabama (Baker,  1988).  Costs for each area were
       specific to anticipated local methane production rates and to local labor and material
       costs.  The USBM  benefitted from some information  provided to them by mining
       operators in  these  regions.  However, this study only estimated  investment and
       operating costs over a five-year period for a system with fixed methane capacity.  No
       estimate of actual production from the boreholes over time was provided.  Therefore,
       it is not possible to  evaluate the economic viability of  such a system using the  USBM
       costs alone.  The results of the USBM analysis are summarized in Exhibit 4-6.
Exhibit 4-6
Total Cross-Measure Borehole Project Costs in Various U.S. Coal Basins
Location
Central Pennsylvania
Northern West Virginia
Southern Virginia
Northern Alabama
Capital Cost
($ millions)
0.3
0.4
1.8
1.2
Operating Cost
($ millions)
1.2
1.2
3.6
1.5
Project Cost
($ million)
1.5
1.6
5.4
2.8
Note: Costs are undiscounted and represent the sum of all costs incurred over the life of the
project, which was assumed to be five years and one year of development.
Source: Baker, 1988.
   Utilization Costs: Utilization costs are presented for four options: power generation using
   gas turbines; power generation using 1C engines; pipeline injection; and  use in industrial
   boilers.  The costs are presented in U.S. dollars, based  on U.S. applications  and
   technology.  Costs in other countries could vary significantly depending on specific
   conditions.

   •  Power Generation in Turbines. The cost of using methane from coal  mines  in gas
      turbines could range from $0.04/kwh to $0.07/kwh or higher.  Key variables are the
      size of the turbine, its efficiency, and the market for waste heat.  The cost of fuel

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4 - 14
COAL MINING
       supplied to the turbine can also be an important cost item; where coal mine methane
       is used, however, it is assumed that the  only fuel costs are those associated with
       transporting and preparing the methane for use.

       The equipment required for on-site power generation includes a turbine generator and
       the gathering lines between the wellhead and the generator.  For off-site sale of power
       to a utility, transmission line upgrades or an interconnection facility may be needed to
       feed power generated  at the mine into the main transmission line.  A range of capital
       costs for power generation are shown in Exhibit 4-7.
                                       Exhibit 4-7
                           Capital Costs for Power Generation
Equipment
Gathering lines between
wellhead and generator
Gas Turbine1
Off-site Transmission2
Low
$10,000 per well
$800 per kw installed
$100,000 per project
Medium
$25,000 per well
$1,000 per kw installed
$300,000 per project
High
$40,000 per well
$1,200 per kw installed
$500,000 per project
  1 Both 1C engines and gas turbines were examined in the analysis. However, for sizes above 4 MW, it was
  assumed that a mine would prefer a gas turbine.  Since projects less than 4 MW were not shown to be
  profitable, 1C engine costs are not included here.
  2 Off-site transmission costs are for costs of an interconnection facility and/or  line up-grades.  The low
  costs assume  that an interconnection  facility would  not be needed and that  line up-grades would  be
  minimal.
  Sources  used  to develop ranges: 1) Carl  Sturgill Power Generation: On-site  Use  and Sale to Utilities
  (Prepared for USEPA April, 1991); 2) "Opportunities for Power Generation from Methane Recovered During
  Coal Mining" (Draft Report Prepared for USEPA by ICF Resources, 1990a); 3) Bill Wolfe and Greg Maxwell,
  "Commercial Landfill Gas Recovery Operation: Technology and Economics" in Klass,  Energy from Biomass
  and Wastes XII (Institute of Gas Technology, 1990); 4) Personal Communication with Allison Gas Turbines.
   •   Power Generation in 1C Engines.  The cost of generating power using 1C engines is
       likely to be slightly lower than for turbines.  In general, the capital costs of 1C engines
       are  lower, with estimates ranging from $350 to $500  per  kilowatt  (Soot,  1991;
       Anderson, 1991).  Operation and maintenance costs are generally higher than  for
       turbines, however, typically around $0.02/kwh.

       1C engines are best  suited to smaller power generation projects, with typical sizes
       ranging from a few hundred kilowatts to 2 or 3 MW.  Project financial analyses in the
       U.S. have indicated that the most economic coal mine generation projects would range
       in size from 4 MW to 20 MW.  For  projects of greater than 4 MW it appears that mines
       would prefer gas turbines.

   •   Pipeline Distribution.  The costs associated with pipeline distribution will include:  (1)
       the    gas   gathering   system,   between  the   wellheads   and   the   central
       compression/processing location;  (2) compression; (3) processing;  (4) enrichment, if
       necessary; and  (5) the transportation system from  the compression point to the

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COAL MINING
4 - 15
      commercial pipeline.  Capital and operating costs for each of these components are
      discussed below, based on U.S. experience.

      The capital costs for gathering lines, compression, and processing and treatment of the
      recovered gas are summarized in Exhibit 4-8.  As the table shows, for certain system
      components capital costs are presented in terms of the gas production ($/mcf) because
      gas production will determine the size of these components.
Exhibit 4-8
Capital Costs for Pipeline Injection All Equipment Needed Between the Wellhead and a
Central Compressor
Equipment
Gathering lines
between wellhead and
Central Compressor
Compressor(s)
Processing/Treatment
Low
$10,000 per well
$1 80 per mcf/day
$10 per mcf/day
Medium
$45,000 per well
$190 per mcf/day
$20 per mcf/day
High
$100,000 per well
$200 per mcf/day
$30 per mcf/day
Note: Capital costs for compressor and processing/treatment are based on maximum gas production per
day. Equipment costs for enrichment of gob gas are included in the total $/mcf operating costs.
Sources used to develop ranges: 1 ) USEPA 1 990; 2) A Technical and Economic Assessment of Methane
Recovery from Coal Seams (Prepared for USEPA by ICF Resources Inc., 1990b); 3) The Potential Recovery
of Methane from Coal Mining for Use in the U.S. Natural Gas System (Prepared by ICF Resources, Inc. for
USEPA, 1990); 4) W.W. Sykes "Gathering Systems Concepts-Planning, Design and Construction"
Proceedings of the 1 989 Coalbed Methane Symposium (The University of Alabama at Tuscaloosa); Warren
R. True "Pipeline Economics" Oil & Gas Journal Special (November 26, 1990).
      In addition  to  capital costs,  there  will  also  be operating  costs associated  with
      compression and processing,  as shown in Exhibit 4-9.  These operating costs are
      based on annual gas production.

      The capital costs for the gas pipelines that transport gas from the point of compression
      to the commercial pipeline are presented in terms of their  cost per mile.  Costs will
      vary  between  or within coal  basins depending primarily on terrain  and land use
      patterns.  Exhibit 4-10 presents a range of costs, which reflects pipeline construction
      experience in several  U.S. coal basins.

      Finally,  in some countries or at some mines it may be necessary to enrich  gob gas
      before it can be injected  into  pipelines.  This will be the  case in situations where
      medium quality pipelines do not exist and where the mine cannot maintain pipeline
      quality  gas through  monitoring and management of the  gob recovery  system.
      Enrichment costs are  quite uncertain and there has been limited experience with the

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4 - 16
COAL MINING
Exhibit 4-9
Operating Costs for Pipeline Injection
All Equipment Needed Between the Wellhead and a Central Compressor
Equipment
Compressor(s)
Processing/Treatment
Low
$.06 per mcf
$.02 per mcf
Medium
$.07 per mcf
$.03 per mcf
High
$.08 per mcf
$.04 per mcf
Sources used to develop ranges: 1) ICF Resources 1990a; 2) Warren R. True "Pipeline Economics" Oil &
Gas Journal Spec/a/ (November 26, 1990).
Exhibit 4-10
Capital Costs for Pipeline Injection
Gathering Lines to Main Commercial Pipeline
Basin
Central Appalachian
Northern Appalachian
Illinois
Warrior
Western
Dollars per Mile
Low
$650,000
$450,000
$200,000
$500,000
$650,000
Medium
$750,000
$550,000
$300,000
$600,000
$800,000
High
$850,000
$650,000
$400,000
$700,000
$950,000
Sources used to develop ranges: 1) ICF Resources 1990; 2) Warren R. True "Pipeline Economics" OH &
Gas Journal Special (November 26, 1990).
      enrichment of mine gas. Current estimates for these costs range from $1.00/mcf to
      $2.00/mcf for various enrichment approaches.  Some  new technologies are under
      development that could have lower costs of $0.50/mcf, but these have not been
      demonstrated.

      Industrial Boilers. The cost of adding capacity for gas combustion at industrial facilities
      will depend on the site and the retrofit requirements. Retrofits for full boiler conversion
      (to 100 percent capacity with gas) can range from $ 1,500/kJ to $3,000/kJ, with sizes
      ranging from 40 kJ to 250 kJ (Glickert, 1992). It would thus cost about $200,000
      to convert an average sized  boiler rated at 120  kJ to gas.  Additional costs would

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COAL MINING                                                                     4-17
       include the gathering of the gas,  any necessary compression and processing, and
       transportation from the point of compression to the boiler site.
Availability

All of the above technologies are commercially available and are in use in various countries.
In countries where the equipment is not locally manufactured it may be possible to import
used equipment or modify existing equipment.
Applicability

Enhanced gob well recovery, when  combined  with suitable  utilization  options,  is an
appropriate strategy for mines where more advanced techniques are not already in use or are
found to be impractical.  In many cases, recovery and utilization  techniques will build upon
existing practices.

Medium quality gas can be used in many countries for a wide range of  utilization options.
Some countries,  especially developed countries, may have gas quality standards which
prohibit the distribution of a medium quality gas for residential fuel use and therefore reduce
the overall marketability of non-pipeline quality gas.  In these countries, power generation or
on-site industrial uses (e.g., coal-drying) may be the most feasible options. In countries with
fewer restrictions on medium quality gas use, the full range of  options may be applicable.
Barriers

Barriers to the development of these recovery and use options will depend on the country and
the technology used, but frequently include: investment capital shortages, lack of resources,
difficulties  in maintaining  gas quality,  and regulatory or institutional  barriers related to  a
country's coal mining or energy sector. To address the technical difficulties, methane content
can be carefully monitored and  methods to compensate for heat value variations can be
implemented.  Overcoming regulatory, legal or institutional  barriers may require changing
legislative or legal frameworks.   To the extent that  particular policies have reduced the
economic attractiveness of projects, moreover, it may be necessary to remove energy
subsidies, rationalize prices, and/or provide incentives  to encourage methane utilization.
Benefits

In addition to the reduction of methane emissions into the atmosphere, other benefits will be
seen from the recovery and use of coalbed methane:

   •   Mine safety will be improved.   Because methane drainage is  improved with the
       enhanced gob well  recovery  strategy, the methane concentration  in the  mine  is
       reduced, which may result in fewer methane-related accidents at mines.

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4-18                                                                    COAL MINING
   •  Ventilation costs will decrease.  One mining company in Alabama, U.S. has been able
      to increase coal production white decreasing  ventilation costs by using improved
      methane recovery techniques. This mine has estimated that capital expenditures of
      $15 million would  have been  required for  additional ventilation shafts and  fans
      necessary to ventilate the same amount of methane which is now being recovered at
      a profit (Dixon, 1989).

   •  A more efficient energy source will be used. Methane can be a more efficient fuel than
      coal, particularly in residential cooking  and heating end-uses.  Many countries,
      including China, use coal extensively for residential purposes (JP International, 1990).
      Coal combustion cannot respond efficiently to low load operation, nor is it easy to start
      and  stop operation as the heating  load swings.  In  comparison, gas can  respond
      instantaneously to  heat demand and can be used for low  load operation, thereby
      providing a more efficient fuel source.

   •  Less S02, NOX, and particulate emissions will  be produced by the displacement of coal
      with gas.  Natural gas combustion produces virtually no SO2 emissions, no particulate
      emissions,  and lower NOX emissions. A 10 percent increase in gas use in a retrofitted
      coal-fired burner will result in a 10 percent decrease in S02 and particulate emissions.
      In many countries, expanded natural gas use is being aggressively pursued in response
      to serious local air pollution problems (Pilcher et al., 1991; Bibler et al., 1992).
                       Enhanced Gob Well Recovery and
                       Utilization

                       •  up to 50% methane reduction
                       •  improved mine safety
                       •  improved mine productivity
                       •  competitive with alternative gas
                          sources
                       •  augments existing  practices
                       •  technology currently available
                       •  clean energy source

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COAL MINING                                                                    4-19
4.3   Pre-Mining Degasification

Pre-Mining Degasification is a strategy that produces methane from targeted coal seams prior
to active mining. Unmined coal of high rank, such as bituminous coal, may contain as much
as 10 to 20 cubic meters of methane per metric ton of coal (Kim, 1977). Additionally, larger
quantities of methane are stored in the surrounding rock strata.  During mining operations, this
methane can also flow into the mine workings  where it may create a severe safety hazard.
Conventional methods for removing mine gas dilute the gas and vent it into the atmosphere.
Pre-mining degasification recovers this otherwise wasted resource before mining begins,
thereby increasing  utilization options and reducing the methane emissions associated with
future mining activities.
Recovery Technology Description

The two primary recovery technologies are in-mine horizontal boreholes and vertical wells
drilled from the surface.  Both techniques can be implemented anywhere from six months to
several years prior to the commencement of active mining operations, depending upon the
amount of degasification required and various geologic factors such as the methane content
and permeability (USEPA, 1 990). Drilling horizontal boreholes is an in-mine technique; vertical
wells are drilled from the surface.  Both techniques remove methane from areas of the coal
seam that are not yet exposed to ventilated mine workings, and as a result typically produce
higher quality gas than the "Enhanced Gob Well Recovery" approach. Furthermore, unlike gob
gas recovery,  pre-mining degasification does  not  depend on active mining operation to
stimulate methane emissions.  As a result, gas production can be more reliable  over longer
periods of time.

   Horizontal  Boreholes:  Horizontal boreholes have been used  extensively for methane
   drainage, especially in the United States and some European countries. These boreholes
   are drilled into the unmined coal seam itself, in contrast to cross-measure boreholes which
   are angled  up into coal and rock strata at the boundary of the gob area (see "Enhanced
   Gob Well  Recovery").   The boreholes  are  typically a few  hundred meters long.  All
   horizontal  boreholes are drilled and produce methane prior to mining.

   In general,  horizontal boreholes are longer than cross-measure boreholes and therefore
   require more powerful drilling equipment. They can be drilled in two ways: 1) into the
   longwall panel, or 2) into mine development areas prior to the preparation of panels for
   mining. In the first case, horizontal boreholes are drilled across the width of a developed
   longwall panel and typically produce gas for a period of several months until they are
   mined through. These boreholes are generally a few meters shorter than the width of the
   longwall panel. In the second  case, much longer boreholes can be drilled into the coal
   reserves from development headings and drain gas for several years in advance of mining.

   As with cross-measure boreholes, horizontal boreholes are connected to an in-mine piping
   system often operated under negative pressure to remove the gas.  However, the gas
   quality is higher, typically over 95  percent methane. Production volumes vary with local
   geology and borehole length, and  have  ranged from 700 to 5,000 m3/day (Trevits and
   Finfinger, 1986; Baker et al., 1986; Kline et al., 1987).  Useful production lifetimes are

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4 - 20                                                                     COAL MINING
   reported to be from six months to several years. The production lifetime is limited by how
   far in advance the mine is developed or the longwall panels are defined and laid out.

   Horizontal boreholes are not as effective for degasification when coal seams are steeply
   inclined or have  very low permeability,  as  is the case in many of the world's coal
   producing  countries  such  as  Japan  and  China.    In  these countries,  pre-mining
   degasification is carried out using cross-measure boreholes drilled from a gallery under the
   coal  seam (Higuchi,  personal communication). Boring stations are typically located every
   50 to 100 m (1 60 to 330 ft) along the gallery, and a number of boreholes are drilled from
   each station.  Borehole spacing depends on coal and geologic characteristics, and they are
   usually spaced  10 to 25 m (30 to 80 ft) apart.

   Vertical Wells:  Degasification using vertical wells drilled  from the surface  is a more
   recently developed technology that has been  commercially demonstrated in independent
   gas  production  and  coal mining operations.  Vertical degasification wells are similar to
   conventional oil and gas wells and are drilled  into the coal seam several years in advance
   of active mining.  This technology is more advanced than the use of in-mine boreholes
   because of the greater depth of drilling, the need to drill through rock rather than coal, and
   the need  to stimulate the reservoir in order  to produce gas.  Despite  this, suitable
   technologies have been developed and  are widely available.  The advantages of drilling
   from the surface include avoiding working in the mine, and the ability to degasify the coal
   seam many years prior to mining.

   Because of the vertical orientation of the well, only a few meters of the coal seam will be
   exposed (i.e., the  height of the coal seam), in  contrast to the hundreds of meters exposed
   to an in-mine borehole. Depending on the  permeability of the coal seam this may limit the
   desorption rate of the methane into the well, thereby limiting overall recovery potential.
   In order to overcome this, fractures can be induced in the seam by hydraulic fracturing  (or
   stimulation), a process in  which a sand and water mixture is pumped under pressure into
   the wellbore.  This fracturing process increases the permeability of  the seam by creating
   pathways through which  the gas can flow.

   Care must be exercised in the design and execution of hydraulic fracturing to ensure that
   the future mineability of the coal is not jeopardized. Many coal miners are concerned that
   uncontrolled fracturing could weaken roof rocks and reduce mine safety when the area is
   mined through.  Experiments in U.S. mining regions have shown that hydraulic fractures
   can  be controlled and should not adversely affect future mining (Deul, 1986).  In fact,
   several coal mines in the U.S. are using vertical degasification and hydraulic fracturing to
   recover methane  in  advance of mining  (Consolidation Coal Company, 1992;  Oxy USA,
   1992).  When these technologies are used in  other basins, however, care must be taken
   to protect the integrity of the coal.

   After fracturing, water must be removed from the coal formation in  order to produce gas.
   Removing water (which is naturally occurring  and also added during  hydraulic stimulation)
   decreases the hydrostatic pressure on the coal seams, thereby allowing gas to desorb from
   the coal.  Coalbed methane wells usually  produce substantial quantities of water during
   the first year  of production, after which water production decreases and stabilizes over
   a long period of time.  Methane production peaks after the initial dewatering, and declines
   slowly (10-20 percent/yr) over the lifetime of  the well (USEPA, 1990). Recovered water

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COAL MINING                                                                     4 - 21
   must be disposed of by direct land application, discharge into streams or rivers, deep well
   injection, or in evaporation pits.

   The quality of produced water varies depending on geologic characteristics; in some cases
   the water is potable, while in other cases it has high concentrations of dissolved salts and
   other solids.  The quantity and quality of the produced water, as well as applicable
   regulations, will determine what disposal or treatment method is required.  Where large
   quantities of water, poor quality, or local regulations necessitate advanced treatment (such
   as deep well injection or desalination) the disposal costs can be  substantial.

   Pre-mining  degasification using vertical  wells may be a very effective method of reducing
   the methane content of coal seams and could consequently  reduce the emissions from
   mining operations. Recovery rates of up to 70 percent over a 10 year  period have been
   documented using this technique (USEPA, 1990). Gas quality is high  (over 90 percent
   methane) because the methane is not diluted with ventilation air. Production  rates depend
   on  reservoir and geological factors, the success of hydraulic  stimulation, coal rank, and
   well spacing.

Where the techniques described above are already in place, it is often possible to increase
recovery efficiency through improved drilling techniques, improved pumping and in-mine piping
systems,  and  the use  of more  advanced monitoring and  control systems.    These
improvements have been discussed above  (see "Enhanced Gob Well Recovery").
Utilization Technology Description

Pre-mining degasification typically yields high quality gas, with a heat value greater than 32
MJ/m3 (950 Btu/cf).  The recovered gas can be used in any of the applications described
above  for medium  quality gas (in  "Enhanced Gob Well Recovery"),  including electricity
generation, gas  distribution systems, and industrial  heating.  High quality gas will be a
preferred fuel because it does not cause some of the technical problems associated with
burning fuel with a lower heat value. In addition to the previously described uses, gas that
consistently contains 95 percent methane is "pipeline quality," and can be sold in high quality
pipeline systems (e.g., in the U.S.). This high quality gas may be transported long distances
or used as a chemical feedstock, in addition to its other uses.

   Pipeline Distribution:   Conventional natural gas is generally processed, gathered, and
   compressed on its way from the wellhead to the pipeline.  As with conventional gas
   production, methane recovered from coal mines will also require these steps, although the
   specifics of these activities may  differ slightly.

   Processing involves the removal  of impurities. For most coalbed methane,  the principal
   contaminants are water and sand, which can be easily removed.  Some coal seams may
   also contain significant concentrations of C02, which must also be removed  from the gas
   prior to pipeline injection.   In cases where rare trace gases (e.g.,  helium) are found,
   separation techniques can be used to remove the gases and these by-products can then
   be sold. Water and sand are removed at the wellhead; trace gases and  C02 are usually
   separated at a central processing location after the gas is gathered.  Gathering lines are
   laid between  the wellhead and the processing plant of pipeline.

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4 - 22                                                                     COAL MINING
   The gas is compressed and propelled through the gathering lines to the pipeline.  The
   required compression is a function of the compressor's inlet pressure, outlet pressure, and
   rated capacity. Pressures typically range from 200 to 800 psi (ICF Resources, 1990c).

   Chemical Feedstock:  Methane is a  feedstock (i.e., a raw material) in several important
   chemical processes, such as the synthesis of ammonia, methanol, and acetic acid. In very
   gassy areas, pre-mining degasification can recover the large quantities of consistently high
   quality methane required to supply chemical plants. The smallest plants typically require
   about 5 to  10 million standard cubic  feet  per  day (280,000 cubic  metersMXytel
   Technologies, 1992), although smaller plants may be feasible.  Alternatively, coalbed
   methane from several mines could be collected at a central location in order to meet this
   required volume.
Total project costs will include both the costs associated with methane recovery and the costs
associated with gas utilization.  A range of costs associated the two pre-mining recovery
technologies -  vertical wells and in-mine boreholes -- are summarized below.  Many of the
utilization costs have already  been presented in the discussion of gob well costs, but those
costs associated with unique utilization options,  such as chemical  feedstock, are also
presented in this section.

   Recovery Costs:  The costs associated  with recovering methane in advance of mining
   using vertical wells and in-mine horizontal boreholes are  summarized below. These costs
   are based on U.S. experiences and technology and they are presented in U.S. dollars.

   •   VerticaLWells. The costs associated with recovering methane in advance of mining
       using  vertical  wells are higher than for gob  wells, because  these wells  require
       additional completion and hydraulic stimulation and because it is necessary to dispose
       of the produced water. As with vertical gob wells, the capital costs will vary between
       and within basins depending on the depth of the wells and site specific conditions,
       which can influence the completion method used, the type of stimulation, the amount
       of water produced, and the method of water disposal required.

       Exhibit 4-11  summarizes the capital costs associated  with vertical  well  drilling,
       completion and stimulation in the United States.  The costs of surface rights and site
       development are also included in these figures. The costs associated with coal basins
       in the eastern United States tend to be lower as compared to western basins because
       the eastern basins are usually shallow.

       The operating costs of vertical wells will depend on  the number of wells in operation
       and on annual gas and water production.  The per well recovery costs are associated
       with the operation,  maintenance and administration of the producing  wells.  They
       should be quite similar to those for vertical gob wells and are assumed to remain fixed
       over the lifetime of the well regardless of the amount of methane  recovered. The
       operating costs could range from $4,000 per well to $8,000 per well, depending on
       site specific conditions (ICF,  1992).

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COAL MINING
4 - 23
Exhibit 4-1 1
Capital Costs for Vertical Wells (per well costs)
Basin
Central Appalachian
Northern Appalachian
Illinois
Warrior
Western
Low
$60,000
$50,000
$45,000
$90,000
$320,000
Medium
$140,000
$125,000
$115,000
$190,000
$450,000
High
$225,000
$205,000
$195,000
$290,000
$580,000
Note: Capital costs for vertical wells include all costs for surface drilling rights, site development and
preparation, drilling, completing and equipping the wells and hydraulic fracture treatment.
Sources used to develop ranges: 1 ) USEPA 1 990; 2) A Technical and Economic Assessment of Methane
Recovery from Coal Seams (Prepared by ICF Resources, Inc. for USEPA, 1990); 3) The Coalbed Methane
Resource and the Mechanisms of Gas Production (Gas Research Institute, 1989); 4) Economics and
Financing of Coalbed Methane Ventures (Ammonite Resources, 1991); 5) Hunt and Steele Coalbed
Methane Technology Development in the Appalachian Basin (prepared for Gas Research Institute, 1991);
Market Study of Future Coalbed Methane Activity (Spears and Associates, 1991).
      Vertical wells typically produce significant quantities of water during the first months
      of operation, which must be disposed of in an environmentally safe manner.  Water
      disposal  costs  will vary  for individual mines depending on geologic conditions and
      applicable environmental regulations.

      The capital costs for water disposal systems can range from $0.30/barrel of water to
      $3.30/barrel of water. The low end of this range is associated with stream discharge
      with little treatment, a practice that is sometimes practiced in the Warrior basin.
      Medium  costs of $0.90/barrel of water would be associated with  stream discharge
      with treatment, or land application with treatment, as is practiced in  the Warrior basin.
      The high end of this range is associated with the cost of disposal wells or evaporation
      pits, which are often  necessary, as is the  case in the Western U.S.

      The operating costs for water disposal can vary significantly depending on the disposal
      method used. Generally, the stream or river discharge disposal method has the lowest
      operating costs.  Evaporation pits, surface application, and stream  or river discharge
      with treatment, deep well injection and  commercial off-site disposal  have higher
      operating costs.  Operating costs for water disposal can range from  $0.40/barrel of
      water to $1.00/barrel.

      The methane production costs (in  $/mcf)  will  vary  significantly depending upon
      numerous site-specific factors, such as depth of drilling, completion and stimulation
      methods used, water  disposal requirements, and gas production.  Low costs could be

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4 - 24                                                                     COAL MINING
       in the range of $1.00/mcf,  and high costs could  reach $3.50/mcf or  more.  As
       production costs increase, project economics become less attractive.

   •   In-Mine Boreholes. The costs for in-mine horizontal boreholes have been estimated by
       the U.S. Bureau of Mines and others (Baker,  1986; ICF Resources, 1990a). The total
       system costs associated with several U.S. projects -- including the boreholes, methane
       collection  system,  gas transmission  system,  and methane sensing  system --are
       reported to range from $25/foot of borehole to $35/foot of borehole.  These  costs
       include both amortized investment and system operating costs. Capital and operating
       costs for drilling alone are reported to range from $10 to $15 per foot of borehole.
       The cost of in-mine piping systems may be about $5/foot of pipe.

       The costs of in-mine systems will of course be highly site-specific. Conditions within
       the mine will determine the number of  boreholes drilled and their gas production rates.
       Likely gas production costs could range from $1.00/mcf to $4.00/mcf  or higher.

   Utilization Costs:  The utilization costs for several options ~  including power generation
   with turbines and  1C engines, pipeline distribution, and use  in industrial boilers - were
   summarized in the section on gob well recovery.  One additional utilization option may be
   attractive where high-quality methane is  recovered:  the use of methane as  a chemical
   feedstock. The costs for this option will  include the costs associated with the process,
   as well  as costs related to collecting and transmitting the methane to the point of use.
   These costs will be highly variable depending upon the feedstock process selected and the
   amount of gas to be processed.
Availability

All of the above technologies are commercially available, but may not be feasible in certain
regions for technical or economic reasons.  In countries where the equipment is not locally
manufactured, it may be possible to import used equipment or modify existing equipment.
Factors affecting applicability and barriers to implementation are discussed in the following
sections.
Applicability

Pre-Mining Degasification is  an appropriate strategy for  very gassy mines where more
advanced techniques are already in use, or may be easily introduced.  In many cases, recovery
and utilization techniques will build upon existing practices.

High quality  gas  is a valuable  energy source  or raw material that can be  used in  many
countries. Developed countries, in particular, are likely to have pipeline infrastructures which
would allow the distribution of high quality gas for commercial sale and/or residential fuel use.
The price for natural gas varies considerably from region to region, however, and can have
a large effect on the applicability of commercial sale as an option (including use as a chemical
feedstock).  Using high quality gas as a chemical feedstock would be attractive for gassy
mines in countries with substantial domestic petrochemical markets (e.g., China and India are
both increasing their domestic demand for ammonium fertilizers).

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COAL MINING                                                                     4 - 25
Barriers

Barriers to the development of these recovery and use options will depend on the country and
the technology used.  Frequently encountered barriers include investment capital shortages,
lack of local resources, lack of technical experience, low gas prices, and legal or regulatory
constraints.  Some of the barriers can be overcome through technology demonstration,
training,  and technical assistance in regulatory development.  In  other cases, it may be
necessary to restructure energy sectors, rationalize energy prices, and provide assistance in
the development of viable gas markets.  Additionally, because the use of recovered methane
as a feedstock requires transport to the point of sale, feasible proximity to commercial users
must be considered.
Benefits

In addition to reducing methane emissions into the atmosphere, pre-mining degasification will
result in several other benefits:

   •   Mine safety will be improved. Because methane drainage is greatly improved through
       pre-mining degasification, the methane concentration in the mine is reduced, which
       may result in fewer methane-related accidents.

   •   Ventilation costs will decrease.  One mining company in Alabama, U.S. has been able
       to increase coal production  while  decreasing ventilation  costs by using  improved
       methane recovery techniques.  This mine has estimated that capital expenditures of
       $15  million would  have  been  required for additional ventilation shafts  and fans
       necessary to ventilate the same amount of methane which is now being recovered at
       a profit (Dixon, 1989).

   •   A more efficient energy source will be used.  Methane can be a more efficient fuel than
       coal, particularly in residential  cooking  and  heating  end-uses.   Many countries,
       including China, use coal extensively for residential purposes (JP International, 1990).
       Coal combustion cannot respond efficiently to low load operation, nor is it easy to start
       and  stop  operation as the heating load swings.   In  comparison,  gas can respond
       instantaneously to  heat demand and can be used for low load operation, thereby
       providing a more efficient fuel source.

   •   Less S02, NOX, and particulate emissions will be produced by the displacement of coal
       with gas.  Natural gas combustion produces virtually no SO2 emissions, no particulate
       emissions, and lower NOX emissions. A 10 percent increase in gas use in a retrofitted
       coal-fired burner will result in  a 10 percent decrease in  S02 and particulate emissions.
       In many countries, expanded natural gas use is being aggressively pursued in response
       to serious local air pollution problems (Pilcher et al., 1991; Bibler et al., 1992).

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4 - 26                                                                    COAL MINING
                       Pre-Mining Degasification

                       •  up to 70% methane reduction
                       •  high quality gas
                       •  long production lifetime
                       •  improved mine safety
                       •  improved  mine  productivity (up  to
                          25% at gassy mines)
                       •  competitive with other gas sources
                       •  technology currently available
                       •  clean energy  source
4.4  Ventilation Air Utilization

Ventilation air utilization presents an opportunity to use the considerable volume of mine gas
that is currently vented into the atmosphere in low  concentrations from all underground
mines. Developing uses for ventilation air can significantly reduce methane emissions to the
atmosphere from coal mining.

The release of methane into the mine workings presents a safety hazard for all deep coal
mines, because methane is explosive  at concentrations  of 5 percent to 1 5 percent in air.
Most countries have regulations which require that methane concentrations be kept below 1
percent.  The most common method of achieving this safety level is to  dilute the methane
through the ventilation of the mine with  large fans. Although additional techniques can be
used, ventilation is a necessity in all underground mines.  As a result, large quantities of air
are removed  which  contain methane at an average concentration  of  about 0.5 percent
methane.  At gassy U.S. mines, between 5 and 23 tons  of air may be ventilated per ton of
coal mined (Skow et al., 1980). Total methane emissions in ventilation air range from 0.5 to
1 5.0 million cubic feet a day of methane for gassy U.S. mines (Trevits et al., 1991).  Recent
estimates for the U.S. indicate that the venting of mine gas accounts for 50 to 75 percent of
all methane releases from coal mining,  and 75 percent of emissions from  underground mines
(USEPA, 1993a).

Although  the methane in ventilation air is  dilute, its energy value may still be profitably
recovered. Efforts to reduce methane  emissions from this source must focus on developing
uses for air that contains low concentrations of methane. The utilization techniques described
here involve using  ventilation air as a  supplemental or secondary fuel for the generation of
electricity in steam boilers and gas turbines. Depending on its concentration and the generator
technology, ventilation air could supply between 7 percent and 1 5 percent of a generator's
energy (or higher if methane concentrations are in excess of 0.5 percent), thereby reducing
primary fuel requirements and contributing  to the electricity need of the mining operation
(ESA, 1991).

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COAL MINING                                                                      4 - 27
Recovery Technology Descriptions

Recovery of the methane is not a factor in this strategy. As noted above, ventilation of the
mine will occur as a matter of course in any underground mine, and utilizing the ventilation
air should have no negative economic or practical effect on mining operations.  Since this
utilization option  has not yet been demonstrated, however, it is important to design the
system in a manner that does not jeopardize the ability of the mine to dilute and remove the
methane from the mine workings.  In addition, this option must be implemented in a manner
consistent with mine safety regulations.
Utilization Technology Description

The utilization option discussed  in this section involves substituting  low concentrations of
methane in air for combustion air in coal-fired boilers or gas turbines. In either case the basic
concept is the same: generators  obtain energy by burning  a fuel/air  mixture, with the  fuel
being coal or gas. Because ventilation air from coal mines  contains methane, it has a heat
energy value which could reduce the amount of fuel required to create an explosive fuel/air
mix of combustion in a boiler or turbine.

For both coal-fired  boilers  and gas turbines, the ventilation air must be ducted  from the
ventilation shaft to the generating facility.  Preliminary technical analyses indicate that the air
supply system can be readily constructed from galvanized steel ducts, typically 7 to 1 2  feet
(2 to 4 m) in diameter (ESA, 1991).  Fans and motors will likely be necessary if the supply
distance is over 1000 feet  (300 m).  The energy needs of the fan motors must be balanced
against the energy value of the mine gas - at some point, depending on duct length, capacity,
and pressure, more energy will be required to transport the gas to the generating facility than
can be recovered  during combustion.  It appears that this distance is on the  order of 3 miles
(5 km).

   Coal-Fired  Boilers:  Coal-fired  boilers burn pulverized coal mixed with large  amounts of
   combustion air to produce steam, which in turn is used to generate electricity. Typically,
   13 pounds of  air are needed for  every pound of coal that is burned (i.e., a 13:1 mass
   ratio).  This translates to approximately 140 standard cubic feet (4 m3) of combustion air
   per hour for each kilowatt (SCFH/kW) of generating capacity, but the ratio will vary with
   coal type, boiler efficiency, and the amount of excess air used in combustion (ESA, 1 991).

   Preliminary technical feasibility studies indicate that ventilation air can  be  transported
   through the air ducts of most types of boilers without compromising safety or otherwise
   affecting standard operation.  The methane should therefore be easily introduced into the
   boiler, where it will burn and produce heat. 140 standard cubic feet of ventilation air (i.e.,
   the approximate amount needed to produce 1 kWh of electricity), containing 0.5 percent
   methane, has  a heat value of 700 Btu (740 kJ).  Ventilation air containing 0.5 percent
   methane could provide  7 percent of the  boiler's energy (ESA, 1991).  Replacing  the
   primary fuel, coal, with methane could also improve boiler economics through reduced  fuel
   purchasing, handling, and preparation costs, less furnace slagging and ash production,  and
   lower emissions of particulates, sulfur dioxide and nitrogen oxides.

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4 - 28                                                                     COAL MINING
   Gas Turbines: A gas turbine uses heat obtained from the combustion of a fuel/air mixture
   to raise the temperature of compressed air.  The hot compressed gas powers a turbine
   which generates electricity. Gas turbines use large quantities of combustion air in the
   fuel/air mixture, typically  350 SCFH  per kW of generating  capacity for  turbines with
   capacities  between 1 and 100 MW.   Based on ventilation  air containing 0.5 percent
   methane, 350  SCFH  would provide 1750  Btu/kWh, or about 15  percent of a typical
   turbine's energy requirements (ESA, 1991).

   Because turbines use larger quantities of combustion air than coal-fired boilers, and thus
   gain a higher energy contribution from ventilation air they are an  attractive option  for
   ventilation  air use.  Additionally,  the simpler technology, lower capital and maintenance
   costs, shorter  construction lead times, and the  large range in  available  generating
   capacities make turbines extremely  suitable for use at coal mines.

The applicability of these techniques must be determined by an analysis  of many site-specific
factors, including the compatibility  of  the  volume of ventilation air with combustion  air
requirements, the mine operation power requirements and/or local energy markets, and the
proximity  and  design  of  the  generating  plant.   A discussion of relative  energy  costs is
presented in the following section.
The underlying factor in choosing to use ventilation air as combustion air is the relative energy
cost of supplying ventilation air. If low concentration methane is to replace some percentage
of the primary fuel requirements for electricity generation, the ventilation air must be supplied
at a lower cost per unit of energy than the primary fuel.

In terms of fuel costs, supplying low quality methane is attractive if the combustion devices
are located in close proximity to the mine.  In this situation, the capital costs of the ducting
should be low and the operating costs associated with running fan motors minimized.  For a
range of air flows from 2 MMSCFH to 80 MMSCFH (compatible with turbine sizes of 5 MW
to 230  MW  respectively), costs are  estimated  to be  $0.08 to over $1.60  per  MMBtu,
depending on the distance and methane concentration (ESA, 1991).  To the extent that new
ventilation shafts are opened as mining proceeds, it may be necessary to move the  fans and
ducting every few years, which could increase costs. In  comparison to current U.S. costs of
$1.50 to $4.00/MMBtu for conventional turbine fuels (e.g., natural  gas and #2 fuel oil) the
economics  of supplying ventilation air to mine-site gas  turbines appear attractive  in many
cases (ESA, 1991).

Energy costs rise when the ventilation air is transported some distance from the mine site.
In this situation, higher methane concentrations and flow rates will increase the overall
attractiveness of the project.  For example, supplying  air containing  0.5 percent methane at
a flow rate of 40  MMSCFH  (compatible with  a  285  MW coal-fired boiler)  would  cost
approximately $1.25 MMBtu at a distance of 3 miles (ESA, 1991).  In comparison, delivered
coal costs are approximately $1.50/MMBtu in the U.S., rising to $1.75- $2.00/MMBtu if costs
for preparation, pollution control and ash disposal are included. Exhibit 4-12 shows estimated
break-even energy costs for ventilation air use based on duct length, methane content, and
air flow.

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COAL MINING
4- 29
Exhibit 4-12
Break-Even Energy Costs for Mine Ventilation Air
Distance
(miles)
Concentration
(% CH4)


< 0.5
1.0
3.0
< 0.5
1.0
< 0.5
1.0
3.0
Gas Flow (mmscfh)
Turbine Capacity (MW)
Boiler Capacity (MW)
2
6
14
20
57
143
40
114
286
80
229
572
|| || Break-Even Energy Cost ($/mmbtu)
0.5
0.5
0.5
0.25
0.25
1.0
1.0
1.0








0.8
> 1.6
> 1.6
n/a
n/a
n/a
n/a
n/a
0.25
0.55
> 1.6
n/a
n/a
n/a
n/a
n/a
0.18
0.35
1.25
0.5
0.8
0.08
0.18
0.5
0.13
0.28
1.25
n/a
n/a
0.08
0.13
0.42
Source: ESA, 1991.
Availability

The  recovery,  transportation,  and  combustion  of ventilation air  uses  equipment  and
technology that is commercially available and accessible.  However, this concept has not yet
been demonstrated and pilot projects should be undertaken to determine if this strategy is
feasible.
Applicability

Large quantities of ventilation air are vented by every operating underground mine.  These
emissions constitute  an untapped energy resource  that can potentially be  utilized.  If a
technical demonstration is successful, the utilization  of ventilation air should  be considered
for every mine.  However, there are economic and practical requirements that will limit the
number of feasible project locations.  The crucial factors are whether the methane in the
ventilation air can be  reliably supplied to the combustion device in sufficient  quantity at an
energy cost lower than the primary fuel, and whether the project can be implemented in a
technically feasible manner that does not adversely affect mine safety  or  the  safety of
powerplant operation.
Ventilation air use may be economically attractive in certain locations if it is proven technically
feasible. Additionally, where primary fuel is available and  electricity demand is expected to

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4 - 30                                                                      COAL MINING
grow, meeting this demand by installing gas turbines in the vicinity of underground coal mines
may be a feasible strategy that more efficiently utilizes local resources.

Barriers

Despite the potential for utilizing this resource, there are several barriers to implementation.
Most importantly, the technical viability of this utilization option has yet to be demonstrated.
Institutional interest and awareness of the potential  is often lacking, as are  incentives to
consider ventilation air as an energy source.  In addition, the massive volume of low quality
gas that is  produced is itself a barrier. Generally, utilizing all the ventilation air produced by
a mine would necessitate a larger generator than is required for mine operations alone. As
a result, full  utilization of mine ventilation air requires external electricity markets and a
transmission infrastructure; this reliance on specific conditions in other sectors of the  local
energy market may present a barrier to project implementation.
Benefits

In addition to the reduction of methane emissions into the atmosphere, other benefits will be
seen from the utilization of ventilation air:

   •   Reduced use of primary energy sources and/or increased generating capacity.  The use
       of ventilation air in  electricity generation can reduce primary energy source use by up
       to 30 percent. This is a more efficient use of energy resources, and can reduce
       reliance on foreign  energy sources.

   •   Less SO2, NOX, and paniculate emissions will be produced by the displacement of coal
       with gas. Natural gas combustion produces virtually no S02 emissions, no particulate
       emissions, and lower NOX emissions. A 10 percent increase in gas use in a retrofitted
       coal-fired burner will result in a 10 percent decrease in S02 and particulate emissions.
       In many countries, expanded natural gas use is being aggressively pursued in response
       to serious local air  pollution problems (Pilcher et al., 1991; Bibler et al.,  1992).
                        Ventilation Air Utilization

                        •   10-90% methane reductions
                        •   efficient use of energy resources
                        •   competitive energy costs
                        •   augments existing practices
                        •   technology currently available
                        •   demonstration projects necessary
                        •   clean energy source

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COAL MINING                                                                     4 - 31
4.5   Integrated Recovery

An integrated system of methane recovery and utilization can take full advantage of all the
available strategies for reducing methane emissions from coal mining.  In many mines, using
two or more methane recovery approaches (e.g., pre-mining degasification with horizontal
boreholes and  vertical gob wells) can:   1)  optimize  mine degasification, achieving the
maximum improvements in mine safety and productivity; and  2) realize economies of scale
as fixed costs are shared (Exhibit 4-13).
Recovery Technology Description

Developing the capability to implement a variety of methane recovery techniques enables an
optimal  response  to site-specific  field conditions.   The  available  methane  recovery
technologies have each been described in the technical assessments above. Each technology
can  effectively reduce  methane concentrations in  mines.  Nevertheless,  due to certain
geological  or  technological  factors it  may  be desirable to  implement a combination of
strategies.  For example, if methane reductions of 50 percent are required to maintain coal
production  most economically while ensuring mine safety, an  optimal strategy may be to
combine gob well recovery with pre-mining drainage.  This has been the experience of at least
one mining operation in the  United States (Dixon, 1987), and many mines in the U.S. and
throughout the world use a variety of degasification techniques to optimize methane recovery.
In addition to technical advantages, economies of scale may be realized in integrated projects.


Utilization Technology Description

As  with recovery technologies, the  utilization technologies  that  have been previously
described may be combined to optimize gas use. The compatible  combination of end uses can
improve technical and economic feasibility.
Costs

Integrated recovery projects will typically be larger than projects employing single strategies;
capital costs are expected to be correspondingly larger. However, unit costs may be lower
due to economies arising from  the implementation of mutually beneficial technologies.

   Economies of Scale:  Several of the techniques use similar technology, equipment, or
   drilling practices, and require similar technical capabilities.  In-mine piping and surface
   gathering  and  processing  equipment  are  often  compatible  with  different  projects.
   Therefore,  certain fixed costs associated with  capital expenditures, support  facilities,
   training, and maintenance may be spread over several types of methane recovery.  Even
   where this is not the case, common costs of project planning and overhead can be shared
   for integrated strategies.

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 4- 32
                                                                            COAL MINING
     Economies of Scope:  The most promising potential for integrated systems lies in the
     mutual benefits of coordinating utilization strategies. For example, one of the significant
     barriers to utilizing ventilation air as a supplementary combustion  fuel is the supply of
     competitively priced primary fuel  for gas  turbines (see "Ventilation Air Utilization").
     Conventional supplies of gas turbine fuel, natural gas or #2 fuel oil, can cost between
     $1.50 and $4.00 per MMBtu, which is often enough to make the installation of a turbine
     uneconomical.  However, coordination of a degasification or gob well recovery project
     with the combustion of ventilation air can  provide a significantly less costly supply of
     primary fuel; medium quality gas (as low as 30 percent methane) is sufficient  to power
     a gas turbine. The integrated recovery and use of both low and medium/high quality gas
     provides a direct demand for the medium quality gas, and removes a barrier to utilizing
     ventilation air; independent of one another, these projects may not be feasible.
                                      Exhibit 4-13
                                   Integrated Recovery
                                                    Gas use
                                                    To Power
                                                 Generation (tor use i
                                                   combustion air)
                                                                              Gas use
Note: not drawn to scale

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COAL MINING                                                                     4 - 33
Mutual advantages may also exist for issues of technical feasibility. Active gob gas recovery
will reduce the volume of ventilation air necessary to maintain mine safety.  As a result, a
smaller and less costly turbine can be used, or a more significant proportion of the ventilation
air can be consumed.  Coordinating the production from  both projects can optimize  total
project economics and  feasibility.
Availability

Technologies for reducing methane emissions are available.  However, certain countries may
need technical  assistance in assessing the trade-offs between approaches for developing
optimal integrated systems.
Applicability

There are significant benefits associated with developing integrated methane recovery and
utilization projects. However, it is important to realize that these benefits are attained through
the implementation of larger and more technically advanced projects. This fact has a direct
impact on the suitability of integrated recovery projects.  It is likely that integrated projects
will only be suitable for large mining operations working in relatively gassy coal seams. The
current  trend in  coal  mining is towards  deeper,  and  thus gassier mines, making the
implementation of integrated  projects increasingly likely.
Barriers

The barriers for integrated recovery will be similar to those facing any methane recovery
project, though larger because of the additional scope, cost, and complexity.  As a direct
result of the size and technical sophistication of these larger projects, capital expenditures and
operating costs will be correspondingly higher even though the long-term economics may be
more  favorable.  Similarly, equipment and training needs will be  more advanced,  as will
technical and planning expertise. Integrated projects will likely only be implemented by mining
operations that have significant previous experience, or with technology transfer assistance.
Benefits

In addition to the reduction of methane emissions into the atmosphere, other benefits will be
seen from the integrated recovery and use of coalbed methane:

   •   Mine safety will be improved.   Because methane drainage  is improved  with  the
       enhanced gob well recovery strategy, the methane concentration in  the mine is
       reduced, which may result in fewer methane-related accidents at mines.

   •   Ventilation costs will decrease. One mining company in Alabama, U.S. has been able
       to increase coal production  while decreasing ventilation costs by using improved
       methane recovery techniques.  This mine has estimated that capital expenditures of
       $15 million  would have  been required  for additional  ventilation  shafts and  fans

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4 - 34                                                                    COAL MINING
      necessary to ventilate the same amount of methane which is now being recovered at
      a profit (Dixon, 1989).

   •  A more efficient energy source will be used. Methane can be a more efficient fuel than
      coal, particularly in residential cooking  and heating end-uses.  Many countries,
      including China, use coal extensively for residential purposes (JP International, 1990).
      Coal combustion cannot respond efficiently to low load operation, nor is it easy to start
      and  stop operation as the heating  load swings.  In comparison, gas can  respond
      instantaneously to heat demand and can be used for  low  load operation, thereby
      providing a more efficient fuel source.

   •  Less S02, NOX, and particulate emissions will be produced by the displacement of coal
      with gas. Natural gas combustion produces virtually no S02 emissions, no particulate
      emissions, and lower NOX emissions. A 10 percent increase in gas use in a retrofitted
      coal-fired burner will result in a 10 percent decrease in SO2 and particulate emissions.
      In many countries, expanded natural gas use is being aggressively pursued in response
      to serious local air pollution problems (Pilcher et al.,  1991; Bibler et al., 1992).

   •  Degasification will be optimized. The integrated use of suitable recovery technologies
      can result in up to 90 percent methane reduction.  Greater reductions can be achieved
      while improving project economics.
                       Integrated Systems

                       •  up to 90% methane reduction
                       •  optimization of degasification
                       •  economies of scale
                       •  economies of scope
                       •  augments existing practices
                       •  technology currently available
                       •  clean energy source

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COAL MINING      	   4 - 35


4.6  References

Contributions were made by:


   E. Dowdeswell, Environment Canada, Canada

   Roger Glickert, Senior Engineer, Energy Systems Associates, USA

   Kiyoshi Higuchi, Hokkaido University, Japan

   Robert Kane, Global Climate Program Manager, U.S. Department of Energy, USA

   Dina Kruger, Project Manager for Coalbed Methane, USEPA, USA

   Carl Sturgill, Independent Consultant, USA


Additional information may be found in the following:
Ammonite Resources (1990),  "Economics  and  Financing of Coalbed Methane Ventures,"
presented by G.W.  Hobbs and  R.O Winkler,  at The  Eastern Coalbed Methane Forum.
Tuscaloosa, AL, January 16, 1990.

Anderson, C. (1991), Waste  Management of  North America,  personal communication,
October 8, 1991.

Baker, E.G., R.H. Grau III, G.L. Finfinger (1986),  Economic Evaluation of Horizontal Borehole
Drilling for Methane Drainage from Coalbeds, 1986, 1C 9080.

Baker, E.G., F. Garcia, J. Cervik (1988), Cost Comparison of Gob Hole and Cross-Measure
Borehole Systems to Control Methane in Gobs, U.S. Bureau of Mines, 1988, Rl 9151.

Bibler, C.J., J.S. Marshall, and R.C. Pilcher (1992), Assessment of the Potential for Economic
Development and Utilization of Coalbed Methane  in Czechoslovakia, prepared by Raven Ridge
Resources, Inc., Grand Junction,  CO, for USEPA, in press.

Consolidation Coal Company (1992), update on Consol/Conoco project in Buchanon County,
VA, delivered at the Fall 1992 Pittsburgh Coalbed Methane Forum Meeting,  October 14,
1992, Morgantown, WV.

Deul, M., A.G. Kim (1986), Methane Control Research: Summary of Results,  1964-80, U.S.
Bureau of Mines, 1986,  B-687.

Diamond, W.P., J.C. Lascola, and  D.M.  Hyman (1986), Results  of the Direct Method
Determination of the Gas Content of U.S. Coalbeds. U.S. Bureau of Mines, 1C 8515, 36 pp.

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4 - 36                                                                  COAL MINING
Dixon, C.A. (1987), "Coalbed Methane -- A Miner's Viewpoint," in Proceedings of the 1987
Coalbed Methane Symposium, Tuscaloosa, Alabama.

Dixon, C.A. (1989), Maintaining Pipeline Quality Methane from Gob Wells. Pittsburgh Coalbed
Methane Forum, April 4,  1989, 7 pp.
ESA (Energy Systems Associates)(1991), "Opportunities for the Utilization of Mine Ventilation
Air," prepared for Global Change Division, USEPA, Washington, D.C. January, 1991.

Garcia, F., and J. Cervik (1988), Review of Membrane Technology for Methane Recovery from
Mining Operations, U.S. Bureau of Mines Information Circular/1988, 1C 9174, 6 pp.

Glickert, R.  (1991), Energy Systems Associates, personal communication, August, 1991.

GRI (Gas Research Institute) (1989), "The Coalbed Methane Resource and the Mechanisms
of Gas Production" Topical Report prepared by ICF Resources, Inc. for Gas Research Institute,
Contract Number 5984-214-1066, November,  1989.

Granatstein, D.L., A.L. Crandlemire, J.C. Campbell, P.P. Preto, B.C. King (1991), "Utilization
of Coal Mine Methane at Lingan Generating Station," presented at the 19th Stack Gas/Energy
Technologies Meeting, Battelle Laboratories, Columbus, Ohio, September, 1991.

Higuchi, Kiyoshi, Hokkaido University,  Japan, personal communication, 1992.

Hunt, A.M. and D.J..Steele (1991),  Coalbed Methane Technology Development  in the
Appalachian Basin. Topical Report prepared by Dames and Moore for Gas Research Institute,
Contract Number 5089-214-1783, January, 1991.

ICF, Inc. (1992), Options for Reducing  Methane Emissions from Coal Mining. Draft Report,
prepared for USEPA  by ICF, Inc.  (in preparation), 1992.

ICF Resources (1990a), Opportunities for Power Generation from Methane Recovered  During
Coal Mining.   Revised Draft Report,  prepared for  USEPA  by ICF Resources,  Inc. with
contributions from ICF Kaiser Engineers,  September 30, 1990.

ICF Resources  (1990b), A Technical and Economic Assessment of Methane Recovery from
Coal Seams, prepared for USEPA/OAR  (Office of Air and Radiation).

ICF Resources  (1990c). The Potential Recovery of Methane from Coal Mining for Use in the
U.S. Natural Gas System,  prepared for the USEPA/OAR.

IPCC  (1990),  Methane Emissions and Opportunities for Control: Workshop Results of
Intergovernmental Panel  on Climate  Change,  U.S. Environmental  Protection  Agency,
Washington, D.C., EPA/400/9-90/007.

JP International (1990), Opportunities for Coalbed Methane Recovery and Utilization in China.
prepared for the U.S. Environmental Protection Agency, September, 1990.

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COAL MINING                                                                  4 - 37
Kim, A.G. (1977). Estimating Methane Content of Bituminous Coalbeds from Adsorption Data,
U.S. Bureau of Mines, Rl 8245, 22 pp.

Kline, R.J., L.P. Mokwa, and P.W. Blankenship (1987), "Island Creek Corporation's Experience
with Methane  Degasification," in Proceedings of the  1987 Coalbed Methane Symposium,
Tuscaloosa, AL, pp. 279-284.

Moerman, A. (1982), "Internal Report on Gas Storage in Peronnes-Lez-Binche, Belgium, S.A.
Distrigaz," 19 pp.

Oxy USA (1992), Update on Oxy USA project in Buchanon County, VA, delivered at the Fall
1992 Pittsburgh Coalbed Methane Forum Meeting, October 14, 1992, Morgantown, WV.

Pilcher, R.C., C.J. Bibler, R. Glickert, L. Machesky, J.M. Williams (1991), Assessment of the
Potential for Economic Development and Utilization of Coalbed Methane in Poland. Prepared
for the U.S. Environmental Protection Agency, Washington, D.C., August, 1991, EPA/400/1 -
91/032.

Skow, M.L., A.G. Kim, and M. Deul (1980), Creating a Safer Environment in U.S. Coal Mines.
U.S. Bureau of Mines, Impact Report, 50 pp.

Soot, P. (1990), Survey of U.S. Coal Mine Degasification Processes, prepared by Northwest
Fuel Development Inc., Portland, OR. Prepared for the USEPA.

Soot, P.M. (1991), "Power Generation Using Small Internal Combustion Engines," prepared
for ICF, Inc., 1991.

Spears &  Associates, Inc.  (1991), Market Study of Future  Coalbed  Methane  Activity.
Summary to Producers, prepared by Spears and Associates, Inc. Tulsa, OK 74135. January
10, 1991.

Sturgill, C. (1991),  "Power Generation:  On-Site Use and Sale to Utilities,"  prepared for ICF,
Inc., April, 1991.

Sykes, W.W. (1989), "Gathering Systems Concepts-Planning, Design and Construction"  in
Proceedings of the  1989 Coalbed Methane Symposium.  The University of  Alabama  at
Tuscaloosa.  April 17-20, 1989.

Trevits,  M.A.  and G.L.  Finfinger  (1986), "Results Given  of Studies  Concerning  Methane
Extraction from Coalbeds," Mining Engineering. August, 1986, pp. 805-808.

Trevits, M., G.  Finfinger and J. Lascola (1991), "Evaluation of U.S. Coal Mine Emissions,"  in
Proceedings of the Fifth U.S. Mine Ventilation Symposium. Society for Mining, Metallurgy and
Exploration, Inc., Littleton, CO.

True, W.R. (1990), "Pipeline Economics," in Oil and Gas Journal Special. November 26, 1990.

USEPA (United States Environmental Protection Agency) (1990), Methane Emissions from
Coal Mining:  Issues and  Opportunities for Reduction.  USEPA/OAR (Office  of Air and

-------
4 - 38                                                                  COAL MINING
Radiation), Washington, DC. Prepared by ICF Resources, Inc., September 1990, EPA/400/9-
90/008.

USEPA (1993a), Anthropogenic Methane Emissions in the United States. Report to Congress,
USEPA/OAR, Washington, DC.

USEPA (1993b), Opportunities to Reduce Methane Emissions in the U.S.. Report to Congress
(review draft), USEPA/OAR, Washington, D.C.

Williams, R.H. and E.D. Larson (1990), "Power Generation with Natural Gas Fired Turbines,"
in Natural Gas: Its Role and Potential in Economic Development, eds. W. Vergara, N.E. Hay,
and C.W. Hall, Westview Press, 1990.

Wolfe, B. and G. Maxwell (1990), "Commercial Landfill Gas Recovery Operations: Technology
and Economics" in Energy from Biomass and Wastes XIII. Edited by Donald L. Klass. Institute
of Gas Technology.  Chicago, Illinois.

Xytel  Technologies  (1992),  "Acetic Acid  from Methane Gas,"    Prepared  by Xytel
Technologies, Mt. Prospect, IL, July, 1992.

Zabourdyaev, V.  (1992), data tables received by Raven Ridge Resources during April 1992
visit to Moscow,  Russia.

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CHAPTER FIVE
FOSSIL  FUEL  COMBUSTION
5.1   Background

Methane Emissions

Fossil fuel combustion releases methane in addition to other greenhouse gases.  Fossil fuels,
which include coal, oil, natural gas, shale oil, and bitumen, provide almost 90 percent of the
energy used by stationary combustion sources (power plants, industrial boilers, residential
heating and cooling) and mobile combustion sources (automobiles, trucks, airplanes and ships)
in industrial nations.

When fossil fuels are burned, carbon is released in the form of carbon dioxide (CO2), carbon
monoxide (CO), methane (CH4) and  other  hydrocarbons (HC), and other trace substances.
The  amount  of  methane in  these emissions  is determined to a  large extent  by the
completeness of the combustion process. As methane is slower to react in  combustion than
most  other hydrocarbons (HC), the release of  methane is  proportionally greatest during
incomplete combustion.

The magnitude and composition of combustion related methane emissions vary according to
the following factors:

   •  Amount and type of fuel combusted;
   •  Methane content of the  fuel;
   •  Completeness of the combustion process (i.e.,  amount of HC passing  through the
      engine unburnt);
   •  Type and condition of engine; and
   •  Use of exhaust control technologies.

Methane emissions from combustion can be reduced by altering the combustion processes
to reduce the amount of gases  produced or by using exhaust control technologies, such as
catalytic converters, to reduce  emissions of some gases after the combustion  process has
taken place. Unless such exhaust control technologies are employed, the gases produced
during combustion of fossil fuels are emitted to the atmosphere.  Estimates of global methane
emissions from this source, although very uncertain, range from 4 to 5 teragrams per year
(USEPA, 1993).
Methane Emissions Reduction Strategies

A number of options exist to reduce methane emissions from stationary and mobile fossil fuel
combustion sources. The feasibility of some of these options has not yet been demonstrated
and, in many  cases, the potential  for reducing  methane emissions has not been  well
quantified. Nevertheless, many of these technologies are being implemented or are likely to
be implemented because of other beneficial effects, such as increased energy efficiency and
reduced emissions of air pollutants and other greenhouse gases.

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FOSSIL FUEL COMBUSTION                                                           5 - 3
As  these various  options  are assessed  further,  efforts will  be  needed  to provide  a
comprehensive accounting of the greenhouse gas balance, and to identify technologies which
are appropriate and economically feasible in different regions.  Exhibit 5-1 summarizes the
options described in the technical assessments which follow.
5.2   Opportunities for Reducing Methane Emissions

Strategies for reducing methane emissions from fossil fuel combustion are described below.
Stationary and mobile combustion sources are discussed separately, as the factors which
influence methane emissions and appropriate emission reduction technologies differ for these
two types of categories.
5.2.1  REDUCTION OF METHANE EMISSIONS FROM STATIONARY SOURCES

Stationary sources of fossil  fuel combustion include industrial  boilers and facilities which
generate electricity to supply energy for industry and for commercial and residential lighting,
heating and cooling processes. These sources represent the majority of methane emissions
from fossil fuel combustion.   Methane emissions from stationary sources vary  widely
according  to the nature and  scale of the process and the fuel used.  Emissions have been
estimated to range from 0.03 grams per gigajoule (g/GJ) energy output for distillate oil boilers
to 6 g/GJ for gas turbines (OECD, 1991;  Radian Corporation, 1990; USEPA, 1985). Possible
emission reduction  options, including  increasing  energy  efficiency,  optimizing   engine
performance, using exhaust controls, and using alternative fuels, are discussed below.
Increase Energy Efficiency

Increasing the efficiency of industrial combustion, electricity generation, and energy use can
significantly reduce the amount of energy input required for  global energy needs, thus
reducing emissions from fossil fuel combustion.  The following technologies for improving
combustion efficiency and enhancing energy use efficiency are appropriate for new buildings
and homes, as well as for retrofitting in older structures.

   Residential and Commercial Sectors:  More efficient building  insulation, appliances,
   lighting, and heating and cooling equipment are commercially available. The use of these
   technologies  is being advanced by EPA programs such as Green Lights, which has
   achieved lighting energy cost reductions of 50 percent in existing commercial buildings,
   and Energy  Star  Computers, which will introduce  computers  using 90 percent less
   electricity. It is technically feasible with available technologies to reduce energy use in
   new homes by 50 percent, and  in new commercial buildings by 75 percent (Lashof and
   Tirpak, 1990). These buildings  may require advanced ventilation systems, however, to
   prevent increases in  indoor air pollution.  Strategies such as using shade trees to cool
   residential buildings can also save energy.

   Industrial Sector and Electricity Generation: Large potential exists for recycling waste heat
   and improving combustion efficiency in power  plants.   Some examples of available

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5 - 4                                                            FOSSIL FUEL COMBUSTION
   technology include cogeneration (i.e., using waste  heat from electricity generation to
   produce steam for other uses); advanced combined  cycle (ACC) turbines, during which
   steam produced from waste heat  is fed to a turbine  to produce  additional electricity;
   variable-speed drives to reduce motor electricity use; and efficiency measures similar to
   those discussed for residential lighting and space conditioning. Another important option
   is the widespread recycling of inorganic waste materials (e.g., bottles and aluminum cans),
   which can conserve substantial amounts of energy  in the industrial sector if recovered
   materials  are used to  produce steel, aluminum  and glass  products.  Some  emerging
   technologies  include the  use of fuel cells  in power  plants, and various clean coal
   technologies.  Estimates of total feasible industrial energy savings  from these strategies
   range from 20 percent  to 50 percent (Lashof and Tirpak, 1990).
Optimize Engines

Because methane emissions, along with other HC and CO emissions, are often highest from
old or poorly tuned engines, these emissions can be reduced by requiring regular maintenance
and timely engine replacement.  Engine use can be optimized by tuning engines to ensure an
efficient air-fuel ratio, and replacing them at optimal times to prevent declines in efficiency due
to age and wear.  In addition, maximizing engine use during operating hours by reducing the
number of start-ups and the times of idle operation can reduce emissions of methane and
other gases.
Implement Exhaust Control Technologies

Emissions of methane, other HC,  NOX, and CO from stationary internal combustion (1C)
engines can be reduced using catalytic converters. These devices, which are placed in engine
exhaust pipes, promote chemical reactions to complete the oxidation of unburned methane,
other HC, and CO into C02 and water and, in some cases, the reduction of NOX into nitrogen
and ammonia.  Non-selective catalytic reduction (NSCR) technologies, used for rich-burn (low
oxygen)  applications, substantially reduce these emissions; oxidation/selective catalytic
reduction (SCR) technologies, more appropriate for lean-burn operations, may almost eliminate
methane and other HC emissions.  As methane is the most difficult  hydrocarbon to oxidize,
significant reductions in methane emissions are achieved only when the exhaust gas reaches
temperatures exceeding 900°F (temperatures should not exceed  1400°F).   These higher
temperatures can be encouraged by placing the converter closer to the engine and insulating
the exhaust piping.  Catalytic converters can be used with engines which run on a range of
fuels, including gasoline, natural gas, landfill gas and diesel fuel.
Increase Use of Alternative Fuels

Enhanced use of alternative fuels in stationary combustion can reduce emissions of methane
and other exhaust gases by minimizing fossil fuel use. Alternative fuel technologies suitable
for stationary applications include solar thermal, wind energy, and photovoltaic (PV) cells.
These technologies are available, and further developments are expected to extend their range
of practical applications. Hydroelectric, geothermal, and nuclear energy are also options, but
their application  is limited to appropriate sites.  The widespread use of nuclear fission could

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FOSSIL FUEL COMBUSTION                                                            5 - 5
contribute to reduced greenhouse gas emissions if concerns about safety, nuclear proliferation
and waste disposal were satisfied, and if costs were reduced. The environmental and social
impacts of developing each of these options must be considered.

In addition to switching to alternative fuels, shifting to fossil-derived fuels (e.g., methanol and
ethanol converted from coal, oil shale and natural gas) can result in lower direct emissions of
methane and other exhaust gases; their production, however, requires energy consumption
and may thus result in large net greenhouse gas emissions. The use of diesel fuel produces
very low emissions of hydrocarbons, but can result in high NOX and particulate emissions.
5.2.2 REDUCTION OF METHANE EMISSIONS FROM MOBILE SOURCES

Although emissions of methane from mobile sources are significantly lower than stationary
source emissions, mobile source emissions still provide abundant opportunities to reduce total
emissions.    Over  25   percent  of  global  energy consumption  each year  is  used for
transportation; most of this energy is provided by oil.  Road transport (i.e., cars and trucks),
which accounts for  over 80 percent of this mobile fuel consumption in many countries,
presents the largest potential for methane emission reductions.  Most road vehicles, which
generally use spark-ignited, gasoline-fueled engines, emit exhaust gases which contain large
amounts of hydrocarbons, of which  about 14 percent is methane (approximately 0.2 grams
of methane are emitted per kilometer travelledXOECD,  1 990).  Total methane emissions from
non-road mobile sources (e.g., farm and construction equipment, railway locomotives, ships
and jets) are much lower than emissions from road sources, primarily because of the smaller
number of vehicles. Many non-road sources also use more efficient diesel-fueled compression
engines, which emit about one-tenth as much methane as spark-ignition engines.

Near term opportunities  exist to cost-effectively reduce methane emissions by improving the
efficiency of mobile fuel  consumption and controlling exhaust gas emissions. Over the longer
term, additional reductions in energy consumption  may be possible  by shifting to alternative
modes of transportation. These options are discussed below.
Increase Fuel Efficiency

Increasing the fuel efficiency of mobile sources (i.e., the distance traveled per unit volume of
fuel) reduces fuel use and, other factors being constant, reduces emissions of all exhaust
gases in proportion to the exhaust composition. Several currently available technologies have
the potential to significantly increase the fuel efficiency of new light-duty  vehicles (e.g.,
passenger cars), which account for over 60 percent of current transportation energy use. Fuel
efficiencies for gasoline engines currently range from about 1 5 to 55 miles per gallon (mpg)
on the road, and studies indicate that these values can be increased by up to 35 percent by
the year 2005 (Plotkin, 1991).

Finally, efficiency  improvements can be achieved by reducing vehicle weight,  although there
is concern that this  strategy may compromise vehicle safety, comfort and/or performance.
Fuel efficiency can be enhanced through technologies such as low friction tires, five-speed
automatic transmissions,  and  improved aerodynamic designs.   Continuously variable

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5 - 6                                                            FOSSIL FUEL COMBUSTION
transmissions  (CVT) can reduce energy losses during  shifting by  allowing the engine to
operate closer to full load at varying speeds.  Using diesel engines, which are more fuel-
efficient, can also reduce methane emissions, although this benefit may be offset by increased
emissions of particulates.

Opportunities for efficiency improvements are also available for freight transport (i.e., diesel
trucks, which  use  14 percent of oil consumed from transportation in OECD countries) and
non-road vehicles.  Adiabatic diesel truck engines,  for example, may  achieve 50 percent
efficiency increases by retaining heat in the combustion chamber and harnessing high pressure
exhaust gases. New technologies for ships have shown 30-40 percent efficiency increases,
and studies show possible aircraft fuel use reductions of 50 percent per passenger mile by the
year 2010 (Lashof and Tirpak, 1990).
Improve Combustion Efficiency

Improving the efficiency with which an engine burns fuel increases the completeness of
combustion, thereby reducing emissions of methane, CO and  other gases which are highest
during incomplete combustion. Combustion efficiency (CE) depends both on the air-fuel ratio
during combustion and on the type of engine. Methane emissions are generally highest when
air-fuel mixtures  are "rich"  (i.e., less  oxygen is  available than is  required for complete
combustion).  Tuning an engine to create a "leaner" (high-oxygen) air-fuel mixture ensures
that a higher proportion of the HC is completely burned, thus reducing the amount of methane
emitted per unit of fuel  burned.  Using  reformulated gas, in which additives (e.g., ethanol,
methanol) increase the oxygen content of the gasoline, can also ensure lean fuel mixtures.
The  possible negative  effects of  raising  air-fuel  ratios (e.g., increasing  nitrogen oxides
emissions) can be prevented using exhaust control technologies, such as catalytic converters,
or electronic engine management systems which minimize emissions by precisely controlling
air-fuel mixtures.

Combustion efficiency can also  be improved through the development and  use of more
efficient engines.   Compression ignition engines using diesel fuel generally burn  fuel more
efficiently than gasoline engines,  although they emit  greater quantities of NOX  and/or
particulates.  One highly-efficient gasoline  engine under development is the Stirling engine,
an external combustion engine designed to achieve extremely low HC, NOX and CO exhaust
emissions by preheating combustion air in a continuous combustion process. Stirling engines
should  soon be available for  commercial applications (Bennethum et al., 1991).
Optimize Engines

As with stationary combustion sources, engine optimization and  proper maintenance can
reduce emissions of methane and other exhaust  gases from mobile combustion  sources.
Tuning engines regularly also helps to maintain an optimal air-fuel (stoichiometric) ratio for
high  combustion efficiency.  Programs to encourage driving at  more efficient speeds (e.g.,
strict enforcement, sequenced traffic lights, improved roads) can  also enhance the optimal use
of vehicle engines.

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FOSSIL FUEL COMBUSTION                                                            5 - 7
Implement Post-Combustion Exhaust Control Technologies

Emissions of methane and other exhaust gases can be reduced or eliminated by using post-
combustion  exhaust control  technologies such as  catalytic converters and  air injection.
Automobile catalytic converters are similar to those used in stationary applications, and have
been shown to reduce HC emissions from a range of gasoline vehicles by as much as 70 to
95 percent.  As in stationary engines, the most significant reductions in methane emissions
are achieved at temperatures between 900° and 1400°F.  These higher temperatures can be
encouraged through such methods as placing the converter close to the engine and insulating
the exhaust  piping.

Automotive  converters generally use one or more of the following two catalysts: oxidation
catalysts, which  reduce only CO  and HC emissions; and three-way catalysts, which also
reduce NOX emissions.   A variety  of  precious metals including  platinum, palladium and
rhodium are  used  to provide sites for the reactions, and base metals can be added to improve
stability.   Regular engine maintenance  and  the use of lead-free fuel are essential to avoid
exposing the catalysts to contaminants or excessively high temperatures.

Air injection, a non-catalyst method of controlling HC and CO exhaust emissions from mobile
sources,  involves injecting air into the exhaust manifold to  enhance the oxidation of these
gases.
Increase Use of Alternative Fuels

Increasing the use of alternative fuels can significantly reduce emissions of methane and other
exhaust gases, while improving the energy security of countries which rely on imported fuels,
by minimizing fossil  fuel use.   Non-fossil automotive  fuel technologies such as solar and
hydrogen fuels have been successfully demonstrated, and may be cost-effective for light-duty
vehicles in the long term. Several fuel cell technologies are also being researched and tested.
Electric cars and trains are another feasible option, although the generation of electricity for
their use results  in some greenhouse  gas  emissions.   Vehicles which use alcohol fuels
(methanol or ethanol) converted from biomass (e.g., agricultural wastes, wood products) are
also available.

The practice of converting solid energy resources (e.g., coal, oil shale) into gaseous and liquid
fuels (e.g., methanol ethanol) is also growing.  The use of these fossil-derived fuels can result
in lower direct emissions of methane and other exhaust gases  if vehicles  are optimized for
their use.  Greenhouse gas emissions can be high, however, during the production of such
synthetic fuels.
Reduce Scale of Emission Source

Another option for reducing methane emissions is to reduce the scale of mobile emission
sources by optimizing transportation systems to minimize total vehicle miles travelled (VMT).
Strategies include improving public mass transit facilities and encouraging reductions in the
use of personal vehicles through the promotion of carpooling and the introduction  of high
occupancy vehicle (HOV) lane highway restrictions. The continued development and use of

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5 - 8                                                            FOSSIL FUEL COMBUSTION
advanced telecommunications systems (e.g., teleconferencing, electronic  mail, electronic
banking) may decrease the need for transportation in the future, thereby reducing fossil fuel
combustion from mobile sources (Lashof and Tirpak, 1990).  The implementation of these
strategies may be justified solely on the basis of traffic congestion and/or air quality problems.

Although total methane emissions from stationary and mobile sources are  significant on a
global scale, methane is a comparatively small component of fossil fuel combustion exhaust
gas. Other gases released during  combustion, such as NOX, CO and other HC's, contribute
to problems such as global warming, smog, tropospheric ozone production,  and acid  rain on
a  much  greater  scale.   Currently,  many nations are developing  and  enforcing  stricter
regulations governing exhaust emission levels of these gases. As a result, technologies aimed
at reducing emissions of these gases and increasing energy efficiency will have the ancillary
benefit of reducing methane.

Many strategies discussed above are cost-effective because they significantly reduce fuel use.
In addition, many technologies are currently  available (e.g., catalytic converters, alternate-
fueled vehicles and advanced engines), although substantial improvements are possible with
ongoing research and development.  A number of technologies are still in the development
stage (e.g., Stirling engines, hydrogen-fueled vehicles), and will require further work before
they will be economically feasible and commercially available.  A combination of these fuel
use reduction strategies, fuel switching,  and emissions reduction technologies will most
successfully achieve reductions of  methane and  other  gases resulting from fossil fuel
combustion.
                       Reducing Methane Emissions from Fossil
                       Fuel Combustion

                       •  some technologies available;  others
                          under development
                       •  many cost-effective strategies
                       •  implementation  likely  in  order  to
                          comply with emissions limits on NOX,
                          CO and other HCs
                       •  methane  reductions  of  80%-98%
                          possible with some technologies

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FOSSIL FUEL COMBUSTION                                                          5 - 9
5.3  References
Contributions were made by:

   Robert Bruetsch, Technology  Development Group, USEPA/Office of Mobile  Sources,
   U.S.A.

   Robert Heavenrich, Technology Development Group, USEPA/Office of Mobile  Sources,
   U.S.A.

   Leonard Johansson, Stirling Thermal Motors, Inc., U.S.A.

   James McDonald, Johnson Matthey Inc., U.S.A

   Steve Plotkin, Office of Technology Assessments, U.S.A.

   Susan Stefanek, Regulation Development and Support Division, USEPA/Office of Mobile
   Sources, U.S.A.


Additional information may be found in the following:

Bennethum, James E., Thomas D.  Laymac, Lennart E. Johansson, and Ted M.   Godett
(1991),  "Commercial Stirling  Engine Development and Applications," SAE Technical Paper
Series 911649 for Future Transportation Technology Conference and Exposition, Portland,
Oregon August 5-7,  1991.

Clement, Raymond and Ron Kagel,  eds.  (1990), Emissions  from Combustion Processes:
Origin, Measurement, Control, Boca  Raton: Lewis Publishers.

Drehmei, Dennis C.  and Charles B. Sedman (1989), Recent Developments of Emission
Control Technology in the United States for Fossil Fuel Combustion Sources, Air and Energy
Engineering Research Laboratory.

IPCC (Intergovernmental  Panel  on Climate Change) (1990), Climate Change: The IPCC
Response Strategies, prepared by  the Response Strategies Working Group, with WMO and
UNEP.  Geneva, June 9, 1990.

Lashof, Daniel A.  and Dennis A. Tirpak, eds.  (1990), Policy Options for Stabilizing Global
Climate: Report to Congress. U.S. EPA/OPPE, December 1 990.

OECD (Organization  for Economic Co-operation and Development)  (1991), Estimation of
Greenhouse Gas Emissions and Sinks: Final Report from the OECD Experts  Meeting, 18-21
February 1991, Prepared for IPCC, August  1991.

OECD (1990), "Greenhouse Gas Emissions:  The Energy Diversion," Joint IEA/OECD Project.
Paris, drafted February 2, 1990, Working Document.

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5-10                                                         FOSSIL FUEL COMBUSTION
Plotkin, Steve (1991), OTA, personal communication.

Radian Corporation (1990),  Emissions  and  Cost  Estimates  for  Globally  Significant
Anthropogenic Combustion Sources of NOx, N20. CH^, CO. and C02. prepared by Air and
Engineering Research Laboratory for EPA/OPPE (Office of Policy, Planning and Evaluation),
May 1990.

USEPA (United States Environmental Protection Agency) (1 985), Compilation of Air Pollution
Emission Factors, AP-42, Fourth Edition. September, 1985.

USEPA (1993). Global Anthropogenic Emissions of Methane, Report to Congress (in progress),
USEPA/OPPE.

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CHAPTER Six
RUMINANT  LIVESTOCK
6.1   Background

Methane Production and Emissions

Methane is produced  as part of the normal digestion process of ruminant animals. These
animals are characterized by a large "fore-stomach" or rumen, in which microbial fermentation
converts feed into products that can be  further  digested  and  utilized by  the  animal.
Approximately 200 species and strains of microorganisms are present in this anaerobic rumen
environment,  although a much smaller  number are  dominant.  The microbial fermentation
performed by the rumen microorganisms enables ruminant animals to utilize coarse  forages
which monogastric animals,  including humans, cannot utilize.

Methane is produced  by rumen methanogenic bacteria as a byproduct of the normal rumen
fermentation process. This methane, which is exhaled or eructated by the animal, represents
a sink for a portion of the feed energy consumed by the animal. Typically from 4 to 9  percent
of gross energy intake is lost through methane production.   This methane loss, therefore,
represents an inefficiency -- feed energy converted to methane cannot be used by the animal
for maintenance, growth or production.

The level of methane production in ruminant animals is influenced by the quality and quantity
of feed consumed. On the one hand, higher levels of feed intake and higher quality feeds are
associated with increased rumen fermentation, and hence higher absolute levels of methane
production (e.g., kg of methane per head per year). Alternatively, higher levels of feed intake
and higher quality feeds are also associated with lower relative levels of methane emissions
per amount of  energy consumed (e.g., percentage of gross energy intake converted to
methane).

These two examples demonstrate that methane production in ruminants can be expressed in
a variety of ways.  For the purposes of  evaluating options for reducing methane emissions,
these emissions should be expressed per unit of product (e.g., methane production per kg of
milk produced).  When viewed in this manner, options can be assessed in terms of their ability
to reduce methane emissions per unit of product produced.
Methane Reduction Strategies

The conditions  under  which livestock are  managed  vary  greatly  by country, especially
between developed  and  developing countries.  Reduction  strategies must be tailored to
country-specific circumstances.  Despite the differences in animal  management practices
among various countries, one common strategy for reducing methane emissions is to increase
animal productivity (e.g., milk production in cows, reproductive efficiency of brood cows).
Virtually all efforts that improve animal productivity will reduce methane emissions per unit
of product produced.

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6 - 2                                                              RUMINANT LIVESTOCK
The ability to reduce methane emissions per unit product produced has been demonstrated
in various countries with intensive animal production systems. High quality feed, selective
breeding,  and  associated  intensive  management  techniques  have greatly increased
productivity.  Coupled with saturated demand market conditions, these developments have
resulted in  decreases  in methane emissions per unit product, and, therefore, in absolute
methane emission  reductions.  Strategies for further reductions from  intensively managed
livestock may involve more advanced productivity enhancers.

To date, similar productivity  improvements have  not  been achieved in  most developing
countries.  Over the past 40  years, increased demand for animal products has been met
primarily by  increases in  the number of animals, as  opposed to  increases in  animal
productivity.  Given the variety of cultural and economic factors that shape animal production
practices in the developing  countries, strategies for  reducing  methane emissions  from
ruminant animals in developing countries must:  1) increase production; 2) be cost effective
under current economic conditions; and 3) be consistent with local traditions and systems of
production.

The following strategies for reducing methane emissions from ruminant livestock are described
in these technical assessments, and  are summarized  in Exhibit 6-1.

   Improved Nutrition Through Mechanical and Chemical Feed Processing: Improved nutrition
   reduces  methane  emissions  per amount of product produced by enhancing animal
   performance, including weight gain, milk production, work production, and reproductive
   performance. Methane emissions per amount of digestible energy consumed by the animal
   may also be reduced. This  option  is applicable to accessible ruminant animals with limited
   feed resources. Assuming that  feed digestibility is increased by 5  percent, methane
   emissions per unit product produced  may decrease on the order of 10 to  25  percent,
   depending on animal management practices.

   •  Alkali/Ammonia Treatment of Low Digestibility Straws. This is a proven technique that
      improves feed  digestibility  and  consequently  animal  performance   (Owen  and
      Jayasuriya,  1989).   Many field trials have  demonstrated its  effectiveness.  This
      process  has been only partially implemented however, since it can be difficult to
      implement  at  the village  level because  it  requires handling caustic materials.
      Additionally, adequate nitrogen in the animal's diet is required to take advantage of the
      increased digestibility.

   •  Chopping of Low Digestibility Straws. Chopping of straws can increase feed intake
      and consequently animal performance in some cases.  This practice is limited in some
      areas  due  to  lack of  chopping  equipment,  which  requires  a   moderate capital
      investment.

   •  Treat and Wrap Rice Straw. A small-scale mechanized procedure for cutting, treating
      and wrapping rice straw is being developed. Essentially an ensiling  process that uses
      urea  as a  nitrogen source,  the  process improves rice straw  digestibility and
      consequently animal performance.  Losses due to spoilage may also be reduced. The
      small-scale  mechanized process may enable larger numbers of small scale farmers to
      improve their  feed resources.  The process  is not yet commercial, and testing is
      ongoing.  Recycling options for wrapping materials need to be investigated.

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RUMINANT LIVESTOCK                                                               6 - 3
   Improved  Nutrition Through Strategic Supplementation:  Improved rumen function will
   reduce methane emissions per amount of feed consumed. Also, by providing additional
   microbial and/or by-pass protein to the animal, emissions per amount of product produced
   will be reduced by enhancing animal performance, including weight gain, milk production,
   work production, and reproductive performance.  Improved rumen function may reduce
   methane emissions by about 5 to 10 percent. In addition, emissions per unit product may
   be reduced by 25 to 75 percent due to substantial increases in animal productivity that
   are anticipated under specific conditions (Leng, 1991 a).

   •   Molasses/Urea  Muitinutrient  Blocks. Balancing rumen function  by supplying key
       supplements in a molasses-urea block (MUB) is a well described technique that may
       be targeted to  animals on  diets that lead  to  deficient  rumen ammonia levels.
       Numerous field trials have been performed.  Improved microbial growth improves the
       protein energy  ratio for the  animal  and reduces  methane  production directly  while
       improving animal performance. Currently, implementation is limited by infrastructure,
       manufacturing, and farmer education levels.

   •   Molasses/Urea  Blocks with  Bypass Protein.  By-pass protein feeds (BPF) may be
       combined with the MUBs. BPFs improve the protein energy ratio for the animal and
       improves animal performance. The  BPF source must be available locally, and ideally
       should come from by-products of existing activities, such as distillery wastes or fish
       processing wastes.  Currently, implementation is limited by a lack of evaluations of
       potential BPF sources as well as infrastructure, manufacturing, and farmer education
       levels.

   •   Defaunation. Defaunation is  the  removal of rumen protozoa that  consume rumen
       microbes. Primarily applicable to grazing animals, defaunation improves the microbial
       protein supply to the animal.  Defaunation agents are not yet available commercially.
       Defaunation is not suitable for animals  on high energy, high grain diets.

   •   Targeted Mineral/Protein Supplements.  Mineral/protein supplements may be targeted
       to specific circumstances to correct deficiencies in the diet.  This technique has been
       applied primarily to grazing  animals in the U.S., and has  successfully enhanced
       reproductive efficiency in beef cows. A lack of understanding of critical deficiencies
       combined with current market and pricing arrangements have limited implementation.

   •   Bioenqineering of Rumen Microbes.  Bioengineering may be  possible  in the long  term.
       Microbes that can utilize feed more efficiently  may be developed.  Additionally,
       techniques for suppressing methanogenesis may  be feasible.
   Production Enhancing Agents:  Certain agents can act directly to improve productivity.
   As a result, methane emissions per unit product will be reduced.

   •   bST. Bovine Somatotropin (bST) is a naturally occurring growth hormone produced by
       the cow's pituitary gland. Recombinant DNA techniques developed over the last 10
       years now allow large quantities of bST to be synthesized. Development tests indicate
       that bST can improve milk productivity by 10 to 20 percent per lactation (Blayney and
       Fallert, 1990).  It is also effective in  promoting feed  efficiency and  repartitioning

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6 - 4                                                               RUMINANT LIVESTOCK
      growth to lean tissues.  The commercial use of bST has been approved in several
      countries and is under consideration in many others.

   •  Anabolic Steroid Implants. Implants are a proven and  commercialized technique for
      improving feed efficiency and repartitioning growth in beef production (USDA, 1987;
      Ensminger, 1983).  However, these agents were recently banned in the EC.

   •  Other Agents. Other agents are being developed, and may be available in the short to
      long term.
   Improved Production Through Improved Genetic Characteristics:  Genetic characteristics
   are limiting factors mainly in intensive production systems.  Continued improvements in
   genetic potential will increase productivity, and thereby reduce methane emissions per unit
   product.

   •   Crossbreeding in Developing Countries. The overall effectiveness of this technique is
       still a matter of dispute. Some claim that native breeds perform better under existing
       environments, and that genetic characteristics are not a limiting factor in production.
       As nutrition is improved genetic factors may increase in  importance.

   •   Continued Genetic Improvement in Dairy  Cattle.  The genetic characteristics of dairy
       cattle are expected to continue to improve  in the future. The major dairy countries
       have significant breeding programs in  place. Detailed recording systems are used to
       perform quantitative assessments of the genetic potential of cows and bulls.  Embryo
       cloning and transplanting techniques,  expected to be applied in the mid-term future,
       have the potential to accelerate improvements in the genetic potential of dairy herds.

   •   Transgenic Manipulation. Over the long term  it will be possible to transfer desirable
       genetic traits among species.  This technique holds great promise for improving the
       efficiency of production in large ruminants.
   Improved Production Efficiency Through  Improved Reproduction:  Large numbers of
   ruminants are maintained for the purpose of producing offspring. Methane emissions per
   unit product can be significantly reduced if reproductive efficiency is increased. The
   nutritional options described above can improve reproduction. Additionally, the following
   options address reproduction  directly.

   •   Twinning. Techniques are being developed to produce healthy twins from cattle (e.g.,
       inhibin vaccine). When combined with adequate nutrition for the mother and offspring,
       twinning can substantially reduce the total number of mother cows required  to produce
       calves.

   •   Embryo Transplants. Embryos produced by superovulated, genetically superior cows
       can be transferred to foster cows of lesser genetic merit. This frees the superior cow
       from the long term pregnancy, redirecting energy towards increased ovulations. This
       technique has the potential to improve overall  reproductive efficiency.

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RUMINANT LIVESTOCK                                                                6 - 5
   •  Artificial Insemination and Estrus Synchronization. These are well known techniques
      that improve reproductive  efficiency.  Their implementation  is limited to intensive
      systems where frequent contact with the cows is possible.
   Other Strategies:

   •  Milk Marketing in Surplus-Producing  Countries. Eliminating surplus production will
      reduce methane  emissions.  Additionally,  changing the pricing systems to reduce
      incentives for surplus fat production would potentially lead to modifications in feeding
      practices that would, as a side benefit, reduce methane emissions per amount of milk
      produced.

   •  Disease Control. Disease control will enhance productivity by reducing mortality rates
      and improving growth  rates and reproductive efficiency.

   •  Beef Marketing: U.S..  Re-orienting the beef marketing system to reduce the amount
      of trimmable fat produced will reduce methane emissions per unit product. Efforts are
      underway to emphasize "value-based marketing" which will have this effect.

Overall, the assessments indicate that there are many opportunities for reducing  methane
emissions at  relatively low cost.  Exhibits  6-1 (a-d) summarize these  assessments.  Each
technical assessment contains the following sections:

   • Reduction Technology Description;
   • Costs;
   • Availability;
   • Applicability;
   • Barriers; and
   • Benefits.

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6-10                                                            RUMINANT LIVESTOCK


6.2  Improved Nutrition Through Mechanical and Chemical Feed
      Processing

Mechanical and chemical processes have been developed that improve the nutritive value of
low quality crop byproducts, principally rice straw. Large quantities of rice straw and other
crop byproducts are produced throughout the world.  In many tropical countries with limited
feed resources, these crop byproducts are the main source of feed for ruminant livestock.

The nutritive value of most crop byproducts, and straws in particular, is limited by their
relatively low level of digestibility. These byproducts possess both physical and chemical
characteristics that impart resistance to biological degradation in the rumen. The primary
factor that has been correlated with low levels of digestibility is lignin content.

While lignin has come to mean somewhat different things to  various disciplines (Van Soest,
1987, p. 120), lignin can be considered to be a  group of substances that exhibit  inhibitory
effects on digestion, either by interfering with  animal metabolisms or by interfering with
rumen microbes.  True lignin,  the major component  of this class of compounds,  limits the
availability of cell wall carbohydrates to rumen microbes.

Chemical and physical treatment methods have been  developed that either remove the lignin
or neutralize  its effects.  These treatments result in  improved digestion  of  the crop
byproducts, and hence improved animal performance.  By improving digestion and animal
performance, methane emissions per unit product are reduced.

Two well  established techniques for improving  the  nutritive value of crop byproducts are
discussed below:  chemical treatment with alkali and  ammonia; and chopping. Additionally,
a new process under development for  wrapping  and  preserving  rice straw is discussed.


6.2.1 ALKALI/AMMONIA TREATMENT OF Low DIGESTIBILITY STRAWS

Chemical treatment of low quality roughages such as straw and other crop byproducts to
improve their digestibility and intake by ruminant animals has been intensively researched
since the  mid-1960s  (Owen and Jayasuriya, 1989).   During  the 1980s there  has been
enormous interest in applying these techniques in the developing countries of the tropics and
subtropics which produce large amounts of crop byproducts.

While a variety of chemicals have been investigated, including various alkalis, acids, salts, and
oxidizing agents, sodium hydroxide and ammonium  hydroxide treatments have dominated
research and development efforts. To date, these two treatments have been found to be the
most beneficial and cost effective methods available. Nevertheless, the implementation of
these methods has been somewhat limited.

Research  is continuing to improve chemical treatments for upgrading the nutritive value of
crop byproducts and to promote their  use more  effectively.  As improved methods become
available,  they may displace the sodium hydroxide and ammonium hydroxide treatments that
are currently preferred.  However, for purposes  of this assessment, the discussion focuses
on these two treatment methods.

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RUMINANT LIVESTOCK                                                             6-11
Reduction Technology Description

Chemical treatments to improve the nutritive value of crop byproducts generally involve
mixing given quantities of the chemical and the byproduct, and allowing them to remain in
contact for a specified period of time. The sodium hydroxide "dip method" is the simplest
approach and includes the following:

   •   a mixture of 14-15 grams of sodium hydroxide (NaOH) per liter of water and 10 grams
       of urea per liter of water is prepared;

   •   the straw is placed into the mixture for 30 minutes; and

   •   the straw is removed from the mixture and stored for 5 days.

Using this process, the digestibility of the straw may increase from about 50 percent to as
much as 75 percent, and the nitrogen content may increase from about 3 gN/kg dry matter
(DM) to as much as 15 gN/kg DM.  Other NaOH processes have been investigated, including
spraying the solution on chopped straw, soaking the straw under pressure, and soaking the
straw under pressure and heat (Owen and Jayasuriya,  1989).

Ammonium hydroxide treatments are similar, and also involve urea.  In the tropics, treatment
with ammonia generated from the hydrolysis  of urea during a 10-25 day ensiling  period is
most favored  (Owen and Jayasuriya, 1989).  The extent to which  improved digestibility  of
the forage versus additional rumen ammonia leads to improved animal performance has not
been  established.   In general, however, these  chemical  treatment  methods  may be
implemented  in a fashion that  is  complementary to  the  application  of  strategic
supplementation techniques discussed below.
The primary cost of chemical treatment of straws and other byproducts is the cost of the
chemicals themselves.  Because NaOH and urea are relatively low cost, the NaOH-urea
treatment methods are preferred.  When animal products are  marketed, the value of the
increased  production of animal  products due to improved  feeding will generally exceed the
cost of the chemical treatment.
Availability

Chemical  treatment  techniques  have  been  verified  and  promoted  in  many  regions.
Consequently, the  information and resources necessary to implement the treatments are
considered to be generally available. There are, however, several barriers that have limited
the adoption of these techniques (see below).

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6-12                                                             RUMINANT LIVESTOCK
Applicability

Chemical treatment to upgrade the nutritive value of crop byproducts is applicable in virtually
all situations where  large quantities of crop byproducts are produced.  Although generally
discussed as a method of improving feed resources in tropical and subtropical developing
countries, NaOH treatment is also practiced in Europe, for example.
Barriers

To date, the use of chemical treatment has been promoted in developing countries at the farm
level. With this approach, individual farmers would treat their own crop byproducts.  Farm
level acceptance has reportedly been slow, however, for several reasons.  The need for large
quantities of water often creates an unrealistic water collection burden, and a reluctance to
handle caustic and poisonous chemicals has discouraged widespread acceptance of these
techniques.  Options that require less water and chemical treatment are being investigated.
However, widespread adoption of these chemical treatment techniques in many countries may
require a more centralized implementation approach, such as involving the feed milling sector.
Under such a centralized implementation approach, transportation cost issues would have to
be addressed.
Benefits

The principal benefit of upgrading the nutritive value of crop byproducts is the improvement
in animal nutrition and performance using the same feed base.  Methane  emissions per unit
product are reduced due to increased productivity.
                  Chemical Feed Processing

                  • methane reduced 10 % or more per unit product
                  • technology currently available
                  • low costs
                  • improves animal productivity
6.2.2 CHOPPING OF Low DIGESTIBILITY STRAWS

Physical modification of straws and other byproducts, such as by chopping and milling, can
improve feed intake and animal performance.  Chopping and grinding are the cheapest and
most cost effective approaches that can be applied at the farm level.  Heat treating and
steaming are also options, but are not cost effective in most developing countries.

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RUMINANT LIVESTOCK                                                               6-13
Chopping and grinding improve the intake of digestible energy by mechanically isolating the
carbohydrate in the feed from the lignin.  Although digestibility of the feed may in fact be
reduced as a result of grinding, increased feed intake more than compensates so that total
digestible energy intake improves. When straw is the principal feed, digestible energy intake
reportedly increases on the order of 30 percent as the result of grinding (Nour, 1986).
Reduction Technology Description

Chopping  and grinding  is accomplished  using specialized grinding  equipment such  as a
hammer  mill or other implement.   The straw  or  other  byproduct is generally  ground
immediately prior to its use.
The primary cost of chopping and grinding is the grinding equipment and the labor necessary
to operate it.  When animal products are marketed, the value of the increased production of
animal products due to improved feeding will generally exceed the cost of the grinding.
Availability

Chopping and grinding are simple techniques that have been implemented in many areas. The
up-front costs of the necessary equipment often prevent this option from being implemented.
Applicability

As in the case of chemical treatment, chopping and grinding to upgrade the nutritive value of
crop byproducts  is applicable  in virtually all situations where large  quantities of  crop
byproducts are produced.  Although generally discussed as a method of improving  feed
resources in tropical and subtropical  developing countries, chopping, grinding and other feed
processing  methods are commonly practiced in Europe, North America, and elsewhere.
Barriers

To date, the principal barrier to the implementation of this strategy has been the up-front cost
of the chopping and grinding equipment.  The development of lower-cost equipment suitable
for individual farm usage may assist in implementation of this option.
Benefits

The principal benefit of upgrading the nutritive value of crop byproducts is the improvement
in animal nutrition and performance using the same feed base.  Methane emissions per unit
product are reduced due to increased productivity.

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6-14                                                             RUMINANT LIVESTOCK
                  Chopping and Grinding
                  • methane reduced 10% or more per unit product
                  • technology currently available
                   improves animal productivity
6.2.3 WRAPPING AND PRESERVING RICE STRAW

As discussed in the previous two sections, significant improvements in the nutritive value of
straw can be achieved through chemical and physical treatments. A new device for wrapping
and preserving rice straw is being developed that may enable these benefits to be realized by
many farmers.

Devices operated by hand and animal power are currently being tested that will cut rice straw,
mix it with urea, and wrap it into small "bales."  At the time of harvest, green straw has a
digestibility of 50-60 percent, which is reduced to 40-45  percent after it is dried.   By
wrapping freshly cut and treated straw, its nutritive value is retained and spoilage is prevented
(Leng, personal comm., 1992). The process may be useful for improving the nutritive value
of rice straw because large amounts of water or caustic chemicals are not required, and it is
expected to be more effective than simple chopping and grinding.

Because development is ongoing,  it  \s premature to  assess the costs and benefits of this
option.  If developed  successfully, the principal value of this device may be its ability to be
more widely accepted and implemented than has been the case with other existing treatment
techniques.
6.3   Improved Nutrition Through Strategic Supplementation

Improving the basic nutrition of animal feeds through strategic supplementation will improve
animal productivity and reduce methane emissions per unit product.  Many of the world's
ruminant livestock survive primarily on low digestibility feeds. While the low energy content
of these feeds can limit animal productivity, the problem is exacerbated for many ruminant
livestock by deficiencies in key nutrients which make the animal unable to utilize as fully as
possible the energy that is potentially available in the feed.  Supplementation to correct the
deficiencies can improve the  digestibility of the feed and the productivity of the animal.
Additionally, in some areas, ruminant livestock suffer from specific mineral deficiencies that
reduce production levels.  These mineral deficiencies can also  be addressed  through
supplementation. In  all cases, supplementation must be designed to address local needs.

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RUMINANT LIVESTOCK                                                              6-15
Microbial Growth in the Rumen

The rumen is a complex living environment that supports microorganisms which digest plant
matter (cellulose).  A deficiency of nutrients needed by these microorganisms will reduce the
microbial mass, thereby reducing both the rumen's ability to digest cellulose and the protein
available to the animal from microbial outflow (from  the rumen).  An important priority for
feeding ruminant animals is to ensure the availability  of  essential  nutrients  for microbial
growth in the rumen.

The efficiency of microbial cell growth (typically measured as microbial  growth per unit of
digestible carbohydrate entering the  rumen) is  limited primarily  by the concentration of
ammonia in the rumen, and by the availability of sulfur,  phosphorus,  and  certain other trace
minerals.   However,  the  absence  of any  nutrient  required  in the  growth  of  rumen
microorganisms will result in low cell growth.

Deficiencies of ammonia and other essential nutrients in the  rumen of animals fed poor quality
forage can be  corrected by supplying molasses/urea  multinutrient blocks.  This strategy is
described in more detail below.
A second factor affecting animal nutrition is the supply of protein (in the form of amino acids)
to the digestive tract of the host  animal.  Amino acids are vital for growth and productive
functions such as milk and wool production, as well as a large number of important biological
processes within the animal.

The principal source of protein for grazed and forage-fed animals is microbial outflow from the
rumen.  In addition to increasing microbial outflow (as above), the available protein can be
increased through protein feed  supplements.  To derive  the maximum benefit from protein
feed supplements, the protein should be in a form that prevents its degradation in the rumen.
Protein that is insoluble or that has a high component of disulfide bonds tends to bypass the
rumen undigested (bypass protein), and  is  therefore available for use by the animal.

The availability of useful  protein is measured as a  ratio of protein to energy (i.e., P/E ratio).
The higher the P/E ratio in the nutrients absorbed,  the more efficient the animal becomes in
utilizing the available energy for growth  and productive functions.  For diets that are low in
protein but have an adequate energy content, supplementation with  bypass protein stimulates
the efficiency of feed utilization.
Protozoa in the Rumen

The role of protozoa in the rumen is still somewhat controversial. For animals consuming high
grain diets, protozoa rapidly assimilate sugars and starches, thereby acting as a valuable pH
buffer for the rumen. In these circumstances defaunation (i.e., removal of these protozoa) is
not recommended.  However, in animals on forage diets, protozoa appear to interfere with
rumen efficiency by ingesting bacteria and  reducing microbial protein flow  out of the rumen,
and hence the P/E ratio. Also, protozoa are thought to increase the degradation of protein in

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6-16                                                              RUMINANT LIVESTOCK
the rumen.  Defaunation will improve the efficiency of feed utilization and will therefore reduce
methane emissions per unit product.   The  possibilities for successful  defaunation  are
discussed later in this section.

The following strategies for improving animal nutrition through strategic supplementation are
presented in this section:

   •  Molasses/Urea Multinutrient Blocks (MUB)  provide  ammonia and  other  essential
      nutrients to rumen microorganisms, increasing rumen efficiency;

   •  MUB with Bypass Protein both increases rumen efficiency and provides protein for the
      improved  utilization of energy;

   •  Defaunation increases microbial growth and reduces protein degradation;

   •  Targeted  Mineral/Protein Supplements improve  animal  performance by correcting
      specific performance-limiting deficiencies; and

   •  Bioengineering of Rumen Microbes enhances the efficiency of feed utilization.
6.3.1 MOLASSES/UREA MULTINUTRIENT BLOCKS

The efficiency of digestion in the rumen requires a diet that contains essential nutrients for
the fermentative microorganisms. When the available feed lacks these nutrients digestion will
be less  efficient, lowering  productivity and raising methane emissions per unit product.
Strategic supplementation of missing nutrients can greatly improve the efficiency of digestion
without requiring a change in the basic diet. The use of molasses/urea blocks is a proven and
cost effective diet supplementation strategy.
Reduction Technology Description

For grazing  animals  and those fed low quality  diets,  the  primary  limitation on efficient
digestion is  the  concentration of ammonia in the rumen.   It has been accepted that the
optimum level of ammonia in the rumen was 50-60 mg/l.  However, more recent studies have
shown that digestibility is maximized above 80 mg/l, and feed intake increases at levels up
to 200 mg/l (Perdok et al., 1 988). Supplying ammonia can therefore greatly increase digestive
efficiency and utilization of available energy.

Ammonia can be supplied by urea, chicken manure, or soluble protein that degrades in the
rumen.  Urea is broken down in the rumen to form ammonia, and adding urea to the diet has
been the most effective method of boosting  rumen ammonia levels  demonstrated to date.
Chicken manure, which has a high uric acid content, has been used in some regions, where
available. While  protein in the feed can provide rumen ammonia, sources of protein are often
scarce, and  where  possible should be  processed and  used  as a bypass  protein (see
"Molasses/Urea  Multinutrient Blocks with Bypass Protein").

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RUMINANT LIVESTOCK
6- 17
In addition to ammonia, there  are numerous nutrients that must be present in the diet to
support the  microbe population in the  rumen.  The most common  nutrients  required are
sulphur and  phosphorus, although this will vary greatly by region.

Urea and other supplemental  nutrients are mixed with molasses to make it  palatable to
livestock.  In addition, molasses provides the energy needed in order to realize the improved
microbial growth that can result from enhanced ammonia levels. Demonstration projects have
added the molasses/urea mixture directly into the feed or have supplied the supplement as a
pre-mixed lick block. The molasses/urea block (MUB) is easy to use and can be produced in
large quantities and transported easily.

The exact composition of the blocks will depend on local needs and available materials.
Important factors are: 1) the level of urea,  which must be effective but not toxic; 2) the
quantity of molasses, which must cover the bitter taste of the urea and provide adequate
energy; and  3) the hardness of  the block, which must deter chewing, and yet be soft enough
to allow easy intake.  In addition to molasses, urea, and supplemental nutrients,  blocks
contain a binding agent to ensure correct consistency, and often contain a locally available
source of soluble protein such  as wheat or rice bran.  A typical MUB composition is shown
in Exhibit 6-2:
Exhibit 6-2
Typical Compositions of Molasses/Urea Multinutrient Blocks
Ingredient
Molasses
Urea
Lime
Mineral/Vitamins
Wheat/Rice Bran
Amount {%)
40-60
4-15
8-10
1-15
20-30
Function
Palatability and Energy
Ammonia Source
Binding Agent
Nutrient Supplements
Soluble Protein
Sources: Leng, 1991a; Saadullah, 1991.
The application of MUBs has been extremely successful in improving productivity, such as
milk yields, growth rates, and reproduction (International Atomic Energy Agency, International
Symposium on Nuclear and Related Techniques in Animal Production and Health,  1991).

MUBs have been used as the sole supplement in many countries including India,  Pakistan,
Indonesia, and Bangladesh.  Typical  results have been:

   • Milk yields increased by 20-30 percent
   • Growth rates increased by 80-200 percent
   • Increased reproductive efficiency.

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6-18                                                               RUMINANT LIVESTOCK
Based on these results, methane emissions per unit product are expected to be reduced by
up to 40 percent.
The use of MUBs has consistently proven to be a successful and cost effective investment.
The application of molasses/urea blocks and the associated increase in feed intake per animal
does increase the cost of feed for managed livestock; case studies typically report increased
costs of 30 percent. However, this investment results in higher productivity; in one study the
cost per  kilogram  of  liveweight gained  decreased by  60  percent.   Overall, the  cost
effectiveness of this technology has attracted considerable interest in many areas of the
world.
Availability

The technology of strategic supplementation with molasses/urea blocks is well understood,
and its effectiveness has been demonstrated both in research and applied case studies. The
results of regional case studies  are  also  increasing awareness and acceptance of this
technique.  Additional research is needed to design applicable projects and  overcome local
barriers to implementation, such as quality  control of the MUB production process and the
structure of agricultural  extension services.
Applicability

Strategic supplementation with molasses/urea multinutrient blocks will be most effective in
regions where constraints on feed  resources decrease animal productivity below genetic
potential.  Because molasses/urea blocks primarily act to increase the ammonia levels in the
rumen, they are most applicable in regions where the base diet results in deficient ammonia
concentrations.  In general, molasses/urea blocks will be most appropriate where  the base
feed is:

   • Low digestibility crop residues, cut/carry grass and agro-industrial  byproducts;  or
   • Grazed forage:
       ~ in monsoonal climate, especially during the dry season;
       - on tropical grasslands on infertile soils (e.g.. South America);
       -- on semi-arid pastures (e.g., Southern U.S., Northern Australia).

To be  cost-effective,  the use of molasses/urea  blocks should be implemented in situations
where farmers can realize the value of the increased productivity  caused by the  blocks.
Therefore, the blocks are most applicable to situations where adequate cash flow is generated
through the sale of animal products such as meat, milk, wool, calves, or draft power.

Barriers

Acceptance of new animal management techniques will always face institutional and cultural
barriers. These can be overcome  through successful demonstration  projects and grassroots

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RUMINANT LIVESTOCK                                                               6-19
level education.  Where investment in new techniques or more expensive feed may not pay
off for several years, or are subject to risk from animal losses, favorable finance and insurance
schemes can  overcome  initial  resistance.   Also,  local ingredients  must be available to
manufacture a suitable block.

The simplicity of the block formulation and manufacture enables the block to be used virtually
anywhere.  Complex technology and capital costs  are not anticipated to be barriers to the
applicability of this technique.
Benefits

In addition to the reduction of methane emissions, strategic supplementation  can provide
several other benefits:

   •  Animal productivity is increased.  In  countries where  feed resources  are limited,
      improving the productivity per unit feed can improve a  country's ability to meet its
      demand  for animal products.

   •  Reduced payment of foreign exchange  for animal product imports.  A secondary
      benefit of increased productivity and better supply of animal products is the reduction
      of food imports.

   •  Increased draft power.   Improved  health, reproductive  efficiency, and  increased
      liveweight all act  to increase available draft power.  Increased draft power can be
      expected to lead to more efficient cropping.

   •  Increased equity for small farmers.   Small farmers are typically limited to grazing on
      public lands where forage is poorer  than on private land.  More efficient  utilization of
      poor quality forage allows poor farmers to better maintain their herds.  The generally
      improved health and efficiency of livestock also reduces susceptibility to famine during
      drought  conditions.
                      Molasses/Urea Multinutrient Blocks

                      • methane reduced 40% per unit product
                      • milk production increases up to 30%
                      • technology currently available
                      • low costs; high returns
                      • significant additional benefits

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6 - 20                                                              RUMINANT LIVESTOCK
6.3.2 MOLASSES/UREA MULTINUTRIENT BLOCKS WITH BYPASS PROTEIN

Proteins provided by rumen microorganisms are generally adequate to support tissue growth
and low levels of lactation in low to moderately producing animals.  Animals capable of higher
yields and faster growth rates, however, need a greater supply of amino  acids than the
microorganisms can provide.  Valuable amino acids contained in many feeds are wasted when
unprotected protein is metabolized in  the rumen.  Bypass  proteins,  also  called  "escape
proteins," escape degradation in the rumen and are digested in the  lower gut.  These proteins
must pass through the rumen very  quickly or have physical or chemical characteristics that
inhibit  microbes  from  metabolizing  them,   Providing  supplements  of  molasses/urea
multinutrient blocks with bypass proteins can greatly increase milk yields and liveweight gains
of animals on straw/forage based diets.
Reduction Technology Description

The combined use of molasses/urea blocks with bypass protein addresses the two critical
aspects of  ruminant  nutrition:  microbial  growth and the  protein/energy ratio.   Both
supplements are manufactured from locally available resources, are tailored to local conditions
and practices, and have proven to be effective in boosting productivity.

   Molasses/Urea Multinutrient Blocks:  These are hard lick-blocks containing  urea, which
   boosts rumen  ammonia levels and therefore increases digestive efficiency.  The typical
   ingredients and their effects are described in more detail in the previous section.

   Bypass Protein:  Protein that is insoluble or high in disulfide bonds will be most resistant
   to degradation in the rumen, and will therefore be available for digestion in the intestine
   of the host animal.  Here, protein is digested in a similar manner to monogastric animals.
   Protein is broken down into constituent arnino acids, which are necessary for growth and
   other important biological  processes.

Protein meals from oilseed production are the most promising sources of high quality bypass
protein.  For example, cottonseed and linseed meal contain 50-75 percent bypass protein.
Also, fishmeal has been used with some success.  High quality cereal crops are one source
of bypass protein; however, these crops are not typically available for animal feed.  Other
sources of protein contain varying amounts of bypass protein, but can  be treated to protect
the available protein from  digestive  action in the  rumen.  These protein  sources include
sunflower and safflower seeds, guar, groundnut, soybeans, lupins, peas, and beans. Where
treatment is necessary to protect the protein, three potential treatment processes exist:  1)
formaldehyde; 2)  heat; and 3) xylose/glucose and heat.

Where suitable sources are available they may be incorporated into the  MUBs directly,
provided separately as a "cake," or mixed into the feed.  The appropriate  level of supplemental
protein varies considerably with animal type, base diet, and protein source.

Case studies using this strategy have found that productivity is increased beyond the effects
of molasses/urea  blocks alone.  In the Kaira district of India a cottonseed meal (30 percent
bypass protein) replaced a conventional  "concentrate" supplement and was supplied with a

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RUMINANT LIVESTOCK                                                               6-21
molasses/urea multinutrient block. The recommended feeding level of the bypass protein
supplement  was  only 50 percent of the previously recommended feeding level  for the
concentrate supplement.  The result of the change was a  30 percent increase in milk
production for the local dairy area.  It was estimated that methane production decreased 60
percent per unit product.

The potential long term benefits of this project should also be noted. The age taken to reach
maturity was reduced from 4 to 1.5 years, and the inter-calving interval from 2 years to 12
to 15 months. Increasing the reproductive rate in this manner, to approximately one calf per
year, can nearly double milk production.  One researcher has calculated that demand for milk
in India can  be  met by  27  million animals (assuming that demonstrated cross-breeding
practices are applied), which could also produce the 13 million draft animals required each
year (Leng, 1991 a). These increases in animal productivity would greatly reduce the number
of animals needed to satisfy consumer demand, thereby reducing the costs of milk and meat
production.
The experience in the Kaira district in India indicates that, although the price of the bypass
feed supplement was about 30  percent  higher than the  previously-used concentrate
supplement, the reduction in the recommended feeding level led to an overall reduction in the
cost of feed.   A cost-benefit analysis prepared for  the Kaira project by Fleming (1991)
estimates an  overall internal rate of return of over 100  percent,  using  conservative
assumptions.  A qualitative assessment of costs in this same study indicates that although
research costs were high, the cost of production inputs and extension services were moderate
to low.
Availability

The importance of protein meals for productivity and growth has been demonstrated through
research and field applications, such as the Kaira project. The successes of MUBs and bypass
protein are increasing the awareness and acceptance of this technique.  Currently, bypass
protein feeds are becoming increasingly available. However, significant efforts are needed to
identify and evaluate suitable sources of bypass protein in many areas.
Applicability

As with MUBs, supplementation with bypass protein and MUBs in combination will be most
effective in regions where constraints on feed resources decrease animal productivity below
genetic potential. In general, this technique will be most appropriate where the base feed is:

   • Low digestibility crop residues, cut/carry grass and agro-industrial byproducts; or
   • Grazed forage:
       - in monsoonal climate, especially during the dry season;
       -- on tropical grasslands on infertile soils (e.g., South America);
       - on semi-arid pastures (e.g., Southern U.S., Northern Australia).

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6 - 22                                                               RUMINANT LIVESTOCK
In  comparison to supplying MUBs  on their own, the capital investments necessary  for
supplying, processing, and distributing bypass protein feed supplements may be large, and
may only  be economically justifiable when adequate physical and financial infrastructure
enables the value of the increased production to be realized.  The total investment required
will depend largely on the size and flexibility of the existing infrastructure for milling and feed
processing.
Barriers

The use of MUBs in combination with bypass protein will face barriers similar to the barriers
applicable to the use of MUBs alone. Farmers will accept this combined technique where they
realize the value of rapid increases in production.   Consequently,  adequately developed
markets for the animal products must exist. Even where benefits are clearly demonstrated,
demonstration projects and extension services may be necessary to overcome institutional and
cultural barriers.

An additional barrier to this strategy is the development of  an  economic supply of bypass
protein. This supply depends upon:  1) identifying a local protein source; 2) possessing the
means to  process bypass protein; and 3) distributing the feed supplements to farmers.  In
many regions, such as those  already processing  animal feed, it may already be possible  to
satisfy these requirements; the extent to which  they constitute barriers will depend upon
regional circumstances.
Benefits

In addition to the reduction of methane emissions, strategic supplementation can result in
several other benefits:

   •  Animal productivity is increased.  In countries where  feed  resources are  limited,
      improving the productivity per unit feed can improve a  country's ability to meet its
      demand for animal  products.

   •  Reduced payment  of foreign exchange for animal product imports.   A secondary
      benefit of increased productivity and better supply of animal products is the reduction
      of expensive food imports.

   •  Increased draft power.   Improved health,  reproductive efficiency, and  increased
      liveweight all act to increase available draft power.  Increased draft  power can be
      expected to lead to more efficient cropping.

   •  Increased equity for small farmers. Small farmers are typically limited to grazing on
      public lands where  forage is poorer than on private land.  More efficient utilization of
      poor quality forage  allows poor farmers to better maintain their herds.  The improved
      health and  efficiency of livestock also  reduces  animal mortality during drought
      conditions.

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RUMINANT LIVESTOCK                                                              6 - 23
                      MUBs with Bypass Protein

                      • methane reduced 60% per unit product
                      • milk production increases up to 50%
                      • technology currently available
                      • low costs; high returns
                      * significant additional benefits
6.3.3 DEFALCATION

For animals grazing on forage or fed similar poor quality diets, protozoa in the rumen are
thought to decrease the efficiency of digestion. The strategy described here uses targeted
dietary supplements to remove protozoa, increasing digestion efficiency and productivity and
reducing methane emissions per unit product. Some supplements are currently being tested
and, along with further expected developments, may be available for application in the mid-
term future.
Reduction Technology Description

The  rumen  is populated by  many  different  species of microorganisms.   In a  symbiotic
relationship, bacteria ferment carbohydrates to gather energy for their own maintenance and
growth, and then provide the host animal with a source of  protein when they flow from the
rumen into  the intestine.    This process  allows  ruminant animals to  utilize  otherwise
undigestible feed.

Protozoa, a type of microorganism in the rumen, derive a portion of their energy by ingesting
bacteria  and, in doing so,  reduce the outflow  of  microbial protein.  Because intensively
managed animals on grain-based diets typically receive large quantities of protein in their feed,
they rely to a  lesser extent upon  microbial  outflow from the rumen to provide protein.
Therefore, protozoa do not significantly interfere with the nutrition of the animal, and are
thought to have the beneficial effect of buffering the pH in the rumen.

Alternatively, microbial growth and  subsequent microbial protein outflow from the rumen is
the primary source of protein for many animals raised on poorer quality feed. In this case, the
ingestion of bacteria by protozoa reduces microbial growth with the dual effect of decreasing
rumen efficiency and reducing the protein to energy ratio. Furthermore, protozoa are thought
to promote the degradation of protein in the rumen.  Defaunation -  the removal of protozoa
and maintenance of the defaunated  state  -- is expected to improve productive efficiency in
these animals.

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6 - 24                                                               RUMINANT LIVESTOCK
Anti-protozoal properties  have been discovered  in at least one type of  natural forage.
Preliminary trials indicate that small amounts of this forage can successfully defaunate the
rumen (Leng, 1991 a).  Pharmaceutical companies are also actively screening chemicals for
this purpose.

Defaunation may increase microbial cell outflow from the rumen by 25-50 percent among
animals on poor-quality forage-based diets. Such an increase may reduce methane emissions
per unit of carbohydrate fermented by approximately 25 percent. Additionally, defaunation
will improve  the  protein to energy ratio in nutrients available to the  animal and increase
productive efficiency.
Costs

Defaunation agents are not commercially available.  Consequently costs are not estimated at
this time.
Availability

Trials are underway to test practical methods of applying this technique, which will lead to
full-scale demonstrations.  If successful, this strategy may be commercially available within
several years.
Applicability

Protozoa are thought to have the largest negative impact on animals whose primary source
of protein is microbial outflow, as opposed to protein contained in  the  feed.  Therefore,
animals fed low-protein crop residues and agro-industrial byproducts, and animals grazing on
relatively dry or infertile pastures are the principal candidates.
Barriers

The primary barrier is currently the need to identify and demonstrate an effective defaunation
agent that can be delivered in a cost effective manner. Once appropriate defaunation agents
and delivery methods are demonstrated, generating adequate supply of the supplements in
targeted regions and gaining farmer acceptance will be important objectives.
Benefits

In addition to the reduction of methane emissions per unit product, it is anticipated that
defaunation will result in several other benefits:

    •   Animal productivity will increase. Defaunation will improve the digestive efficiency of
       grazing  ruminants and increase productive efficiency.  These improvements  can
       improve a country's ability to meet the demand for animal products.

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RUMINANT LIVESTOCK                                                              6 - 25


   •  Reduced payment for animal product imports. Increased productivity and better supply
      of locally produced animal products can reduce expensive food imports.

   •  Improved resistance to drought conditions.  The improved health and efficiency of
      livestock also reduces animal mortality during drought conditions.
                  Defaunation

                  • methane reduced up to 25% per unit product
                  • expected productivity increases
                  • trials underway
                  * significant other benefits
6.3.4 TARGETED MINERAL/PROTEIN SUPPLEMENTS

Many regions  of the world have extensive ranching operations for beef production.  The
reproductive efficiency of beef cows and, in some cases, the efficiency of weight gain of
calves and steers on grazing systems, are adversely affected by specific dietary deficiencies.
In many areas protein is  deficient seasonally.  Additionally, specific minerals are deficient
throughout the year or seasonally.  Supplements targeted to these deficiencies can improve
productivity and reduce methane emissions per unit product.
Reduction Technology Description

The expanded use of both protein and minerals supplements is being investigated.

   Protein Supplements:  Seasonal deficiencies in protein availability are often encountered
   in extensive grazing operations.  For example, in the U.S. mature warm season grasses
   and crop residues used in the winter may be lower in protein than is recommended for
   reproductive performance and adequate milk yield.  Protein supplementation (e.g., with
   cottonseed cakes or meals) can keep grazing beef cows in good condition and promote
   reproductive efficiency and the production of healthier and heavier calves.

   Mineral Supplements:  Mineral elements have been shown to be essential for maintaining
   animal productivity.  Macrominerals (those required in greater quantities and  present in
   animal tissues at higher levels) include calcium, phosphorus, sodium, chlorine, potassium,
   magnesium, and sulfur. Trace minerals (those required in smaller amounts) include cobalt,
   copper, iodine, iron, manganese, molybdenum, selenium, and zinc.

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6 - 26                                                              RUMINANT LIVESTOCK
   Mineral deficiencies in ruminant diets are known to occur to various degrees throughout
   the world.  For example, copper deficiencies have been identified in many areas, due in
   some cases to the interference of excess levels of molybdenum with the ability of the
   animal to absorb copper. Similarly, although toxic in large quantities, selenium deficiencies
   are known  to occur in many areas, including the United States. Mineral deficiencies can
   reduce animal productivity, including reproductive performance among beef cows.  Mineral
   supplements can remove these deficiencies and improve animal performance.
When mineral deficiencies are identified, it is usually cost effective to provide mineral
supplements to eliminate the deficiency. Supplements are available commercially, although
they may not always provide the best mix of supplements required for a given producer's
situation.  Custom formulation of supplements can further improve animal performance and
avoid the purchase of ingredients that are not required.  However, custom mixing is often not
cost effective for small producers.

Mineral deficiencies are not always easy to identify.  Seasonal evaluations of forage quality
and intake levels can be used to assess whether supplementation is needed to correct mineral
and protein deficiencies.  Information about mineral concentrations in the soil can also be
useful information. The cost of these assessments is generally small for commercial ranching
operations.
Availability

Various combinations of mineral and protein supplements are currently available commercially
in  regions with significant commercial ranching operations. However, assessments of the
seasonal deficiencies remain  to be performed  in many cases.  Additionally, commercially
available supplementation packages often do  not  precisely  match the supplementation
requirements.
Applicability

Mineral and/or protein supplementation is applicable when mineral and/or protein deficiencies
are limiting production.  Animals with otherwise adequate feed resources (i.e., diets with
adequate amounts of feed energy) and adequate disease control are the principal candidates.

These  supplementation  strategies  are also applicable  only to situations in  which animal
productivity is important. Therefore, its application is limited to situations in which the sale
of animal products (e.g., calves) is  the primary purpose for keeping the animals.

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RUMINANT LIVESTOCK	6 - 27


Barriers

The primary barriers to increased use of protein and mineral supplements include:

1) insufficient data describing the existence and  severity of  deficiencies in many areas;
2) supplementation products tailored to specific regional and local deficiencies are needed.

In some areas (e.g., in parts of the U.S.), the structure of the beef production industry also
limits the use of productivity enhancing agents such as mineral  and protein supplements. In
some cases, contractual arrangements between pasture/rangeland owners and cattle owners
must be modified to provide incentives for the adoption of productivity enhancing techniques.


Benefits

In addition to the  reduction of methane emissions per unit  product, it is anticipated that the
use of targeted supplements will result in other benefits:

   •  Animal productivity will be increased. Supplements will  provide improvements in the
      productive efficiency of animals already raised in  relatively efficient operations.
                  Targeted Protein/Mineral Supplements

                  •   methane reductions remain to be quantified, but
                      may be on the order of 5-10% per unit product
                  •   expected productivity increases
                  •   technology currently available
                  •   cost effective
6.3.5 BlOENGINEERING OF RUMEN MICROBES

The  efficiency  of feed utilization and hence methane production in ruminant animals is
principally controlled by the microbes in the rumen.  Over the long term, it may be possible
to select or bioengineer specific microbes that improve feed  utilization (thereby reducing
methane production indirectly) or suppress methanogenesis directly.

Some microbial feed additives that improve rumen fermentation are becoming commercially
available.   These products currently contain naturally-occurring microbes.  In the  future,
specially engineered microbes may further enhance efficiency.

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6 - 28                                                             RUMINANT LIVESTOCK
Present knowledge  of  the  rumen  environment  indicates  that  the level  of  rumen
methanogenesis can be altered.  Significant research remains to be done in order to develop
microbes that will enhance feed  efficiency  and reduce methane production  directly  or
indirectly.   For example, areas of research needed to reduce methane production directly
include:

   •   Determination of the key methanogenic species in animals on different diets;

   •   Correlation of methanogenic species and other rumen environmental factors with levels
       of methane production; and

   •   Identification of techniques to inhibit specifically-targeted methanogens without
       adversely  affecting  animal  performance.   A variety of  pathways  for  inhibiting
       methanogens could be examined, including developing hydrogen-using microbes that
       can  out-compete the methanogens or developing microbes that produce an antibiotic
       that selectively inhibits the growth of methanogens.

Given that genetic research on rumen microbes has only recently begun, there is considerable
potential for  successful development of  useful products.   At this  time, however, it is
premature to assess the costs and emissions reduction potential of this strategy.
6.4   Production Enhancing Agents

There  are a variety  of agents that enhance  production in ruminant animals directly  by
regulating various body functions.  Animal growth is a complex physiological process that is
regulated by hormones produced by the endocrine system (Leung, 1988). To enhance growth
and improve feed efficiency, scientists have identified both naturally-occurring hormones and
synthetic compounds with similar chemical compositions that achieve production-enhancing
effects.

Growth hormone is generally considered to be the most important hormone affecting growth
and development.  Through the use of recombinant DMA techniques, growth hormone can
now be produced  in sufficient quantities to make its use in animal production possible. The
administration of other hormones has also been found to have commercially valuable effects
on growth and quality of beef animals.

By improving animal productivity and/or feed efficiency, these production enhancing agents
reduce methane emissions per unit product  produced.  This section reviews the  major
production enhancing agents that are in use  or near final  development, including bovine
somatotropin (the bovine growth hormone),  and anabolic steroid agents.   This section
concludes with a summary  of research that  is continuing on  other  agents  that may  be
available in the future.

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RUMINANT LIVESTOCK                                                             6 - 29
6.4.1 BOVINE SOMATOTROPIN (BST)

Bovine somatotropin (bST) is a growth hormone that occurs naturally in cows, and plays a
major role in the initiation and maintenance of lactation.  This hormone can be synthesized
using recombinant DNA techniques; bST produced in this manner is often referred to as rbST.
Injecting  rbST in dairy cows has been shown to increase milk production per lactation by
about 10 to 20 percent or more (Blayney & Fallert, 1990).  The use of rbST reduces the feed
input per unit product (despite an increase in feed input per cow), and therefore reduces the
methane emissions per unit product.  rbST is also expected to be effective in promoting feed
efficiency and lean tissue production  in growing  beef animals.  Less research has been
performed in this area, so the following discussion focuses solely on rbST use in lactating
cows.
Reduction Technology Description

Growth hormones are proteins, secreted  by the  pituitary gland  in all vertebrate animals.
Growth hormones are naturally occurring compounds  that are vital  for the regulation  of
growth in young animals, and for lactation in mature animals. These hormones are species-
specific, and the hormone occurring in cows is known as "bovine growth hormone" (BGH) or
"bovine somatotropin" (bST).

The secretion of bST stimulates a secondary hormone (also known  as a  "mediator"),  an
insulin-like growth factor-l (IGF-I), which helps coordinate the growth process of young cows.
The hormone bST itself is extremely effective at maintaining lactation in dairy cows.  Milk
from untreated cows always contains certain levels of both bST and IGF-I.

Commercial application of recombinant DNA techniques has made  possible the large scale
synthesis of bovine growth hormone.  In extensive field testing, rbST  has been found to  be
effective in increasing milk production.  The synthetic hormone,  rbST, while sometimes
different from bST (that is produced naturally in cows)  in overall structure  by one or more
amino acids, always contains the same biologically active structure, and stimulates the same
growth and lactation processes.

Concern over the use of a synthetic drug that alters growth patterns  has prompted extensive
study and review of the potential health effects for both humans  and  cows. Currently, the
scientific consensus  overwhelmingly supports the safety and effectiveness of rbST (NIH,
1990).  Both bST and IGF-I are digested like any protein when taken orally by humans, and
are biologically inactive in humans even when injected.  The nutritional content of milk and
meat are unaffected by rbST treatments.

In the United States, the Food and Drug Administration  (FDA) has already found the use of
rbST to be safe for humans; the FDA is currently considering the health and safety of animals
and of the environment, and is expected to reach a final decision  within the next year. The
hormone rbST has currently been approved for use in 8  countries: Brazil, Mexico, Namibia,
Zimbabwe, South Africa, Bulgaria,  Czechoslovakia, and the former Soviet Union (DeGraff,
personal  communication, 1991).

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Productivity studies have demonstrated an average increase in milk production of 10 percent
or more. The increase for a particular herd will vary depending on environmental and farm
management conditions.  The productivity increase is also correlated to dose size, although
there is an upper limit beyond which there is no further growth  effect.  This hormone is
administered by daily injection (because it is  digested if taken orally), although sustained-
release formulas have been developed that allow fewer injections.  Typical dose sizes range
from 12.5 to 50 mg of rbST per day, with the optimum dose size around 40 mg (Fallert et al.,
1987).  Feed intake rises when rbST is used because cows require more energy to produce
more milk, and  feed supplies must be increased to maintain milk production  levels.
The  commercial price of  bST  has not yet been  determined.   The U.S.  Department  of
Agriculture (USDA) has estimated that rbST will cost $0.24 per cow per day, which will give
an expected $2 return on every $1 invested (Blayney & Fallert,  1990; Fallert et al., 1987).
Because most countries actively  support their  dairy industries, the expected  return on
investment of rbST treatment depends to a large  extent on the level of dairy price supports.
Milk production increases within several days of treatment, resulting in a short payback period
(Blayney & Fallert, 1990; Fallert et al., 1987).
Availability

The synthesis of rbST is well developed, and several U.S. companies are prepared to begin
its manufacture if FDA approves commercial application. Field trials in the U.S. have also
provided experience in the application of this drug to production animals.  Where application
is approved, rbST is expected to be available in the near-term (before 1995).
Applicability

This strategy is likely to be cost effective for herds that are currently intensively managed,
that receive high quality feed, and that have a high genetic potential  (i.e., where  other
strategies are already in use) (OTA, 1991).  In particular, effective use of rbST requires that
animal diets are controlled to provide  the  necessary additional energy  for increased milk
production.  In many regions of the world the necessary feed resources and management
techniques are not available.
Barriers

Government health and safety regulations currently control the application of rbST. There are
concerns that must  be investigated before  commercial application begins.   However, as
indicated above, the  preponderance of information currently available indicates that rbST is
effective and safe, and is therefore likely to be approved by additional countries.

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RUMINANT LIVESTOCK                                                               6-31
Benefits

In  addition to reducing  methane  emissions  (OTA, 1991), the use  of rbST improves the
productivity in lactating  cows by over 10 percent.
               Bovine Somatotropin

               •   methane reduced by up to 10% or more per unit
                   product
               •   increase productivity by 10% or more
               •   technology currently available
               •   cost effective
               *   suitable for intensive operations
6.4.2 ANABOLIC STEROIDS

Anabolic steroids have been demonstrated to be effective in increasing the rate of weight gain
and improving feed conversion efficiency among beef cattle.  These effects are achieved by
redirecting the energy used to deposit fat in the animal to the deposition of protein.  As a
consequence, the animal adds protein more quickly and efficiently.  Additionally, the use of
anabolic steroids also results in a leaner  beef product at slaughter.
Reduction Technology Description

Several hormones have been approved for use in food producing cattle including the following:

   •   progesterone, used in steers and intact males grown for beef;
   •   testosterone, used in heifers and in some cases steers;
   •   zeranol, used in heifers and steers;
   •   trenbolone, used  in heifers and steers; and
   •   estradiol benzoate, used in combination with testosterone or progesterone in heifers
       and steers.

The  preferred method  for introducing  the hormones into the animal is by placing or
"implanting" a small pellet under the skin of the animal's ear.  The pellet releases a defined
dose of hormone into the animal's bloodstream. Via the bloodstream, the hormone reaches
its appropriate and effective sites throughout the body. Implanting is preferred to previously
used injection methods  of  delivery because the dose can be controlled carefully, thereby

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preventing  concentrations of the  hormone  from building up in tissues used  for human
consumption.

The hormones will typically increase daily rates of gain by 5 to 15 percent and improve feed
efficiency by  5 to 10 percent (USDA, 1987; Ensminger, 1983).  Hormone implants are not
used in milk producing animals, replacement heifers, or beef cows.

Costs

Hormone implants are extremely cost effective.  The value of the increased rate of weight
gain and the feed efficiency exceeds the cost of the implant and the cost of administering it
to the animal.
Availability

Hormones are widely available and can be obtained commercially for use in producing beef
animals.  However, hormones have been banned recently from human food production in the
European Community (EC).  Additionally, food cannot be imported that was produced with
hormone implants.
Applicability

Hormone implants are applicable to commercial beef production. The principal limitation on
the use of hormones is inaccessibility to the cattle being raised.  Because the pellets must be
implanted in each animal, implants may not be applicable to extensive ranch conditions where
contact with the animals is infrequent.
Barriers

Currently, the principal  barrier  to  wider  implementation  of  implants is regulatory.   As
mentioned above, the EC has recently banned the use of implants due to consumer concerns
regarding safety.  Consequently, the use of hormones is officially restricted in farm animals
in the EC, and effectively eliminated from farm animals in other countries whose products are
intended for import to the EC. Despite consumer safety concerns, all safety reviews of the
above mentioned hormones,  including the  review conducted by the EC, have indicated that
the implants pose no risk to animals, humans, or the environment.
Benefits

The benefits of the hormone implants are improved rate of weight gain and improved feed
efficiency.  Additionally, by redirecting energy away from fat deposition in favor of protein
accretion, a leaner beef  product is produced.  Methane emissions  are  reduced  via two
mechanisms:  1) improving feed efficiency to directly reduce methane emissions  per unit
product,  and 2) promoting faster weight gain,  thus reducing the time to slaughter and
reducing  total methane emissions.

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RUMINANT LIVESTOCK                                                              6 - 33
                 Anabolic Steroid Implants

                 • methane reduced 5-10% or more per unit product
                 • technology currently available
                 * cost effective
                 • improves animal productivity
6.4.3 OTHER AGENTS

Additional production enhancing agents are being developed that are expected to have
commercially-valuable effects on  growth,  feed efficiency,  and  carcass  characteristics.
Examples of compounds under investigation include isoproterenol, clenbuterol, and cimaterol
(Muir, 1988).  To date,  these and similar compounds have been demonstrated to improve
growth rates and feed efficiency by up to 20 percent.  Additionally, carcass characteristics
are improved, including increases in protein and decreases in fat.

Other mechanisms are also being investigated to improve animal productivity. For example,
it has been  determined  that somatostatin (SS) inhibits somatotropin (ST)  release.  If  the
inhibitory effects of SS could be prevented, additional growth could be achieved using  the
animal's  own supply of ST. One mechanism being explored is the development of a vaccine
that would cause antibody binding to SS, thereby reducing its inhibitory effect on ST release.
Considerable research remains to be done in this area.

Efforts are  currently  under  way to review the safety characteristics  of  the candidate
compounds and strategies for improving productivity. Additionally, potential impacts on beef
palatability are being examined.
6.5   Improved Genetic Characteristics

Methods for improving the genetic characteristics of large ruminant animals through breeding
are well established. Genetic potential is an important characteristic in virtually all animal
production systems.  In the tropics and subtropics, certain strains of cattle and buffalo have
increased resistance to parasites and heat stress.  In all environments, genetic potential in
terms of milk production, growth rates, and ease of reproduction are important.

Significant  strides  have  been  made  throughout  the  world  to  improve the  genetic
characteristics of cattle. Record keeping and evaluation systems are in place in the many of

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the major dairy countries (in both developing and developed countries) to provide scientifically-
based data on animal potentials. Additionally, genetic material from high-producing cows has
been systematically introduced in many developing countries.

When management conditions are adequate, improved genetic  characteristics have the
potential to improve production levels and decrease methane emissions per unit product. For
example, improved management and feeding must accompany improved genetics in order for
benefits to be realized. Insufficient feed, inadequate disease control, and  other environmental
stresses (e.g., heat, drought)  will prevent genetically improved animals from realizing their
potentials.

Examples  of improved genetic potential are described in this section. However, opportunities
for accelerating genetic improvement so that methane emissions are reduced have not yet
been fully evaluated.
6.5.1 CROSSBREEDING IN DEVELOPING COUNTRIES

Crossbreeding to improve genetic characteristics has  been systematically  performed in
selected dairy herds in developing countries.  For example, India has imported thousands of
Holstein, Friesian, and Jersey bulls and cows for its crossbreeding program.  Similarly, China
is  importing  Holstein,  Friesian,  and Simmental  animals for its  emerging milk industry
(Jasiorowski, 1988; Sollod, 1992).

Imported cows, bulls, and frozen semen have  all been used  in crossbreeding programs to
produce animals  with the increased production  qualities  of the  exotic parents and  the
environmental fitness of the indigenous parents. Numerous evaluations of the performance
of crossbreeds have been conducted and have produced mixed results.  Some village-based
studies have shown  that poor farmers often fail at raising crossbreeds  because they are
unable to provide the animals with adequate nutrition, while wealthier farmers with better feed
resources are more successful. Therefore, although crossbreeding  programs are successful
in  certain situations,  improving the conditions under which animals are managed in general
will increase the applicability of this strategy. Additionally, with crossbred animals raised in
harsh environments,  it appears to be important to retain a  larger portion  of the indigenous
genes, because indigenous  animals are better  adapted to  withstand  extreme  climatic
conditions, variations in  feed quality and availability, and disease and parasites.

While improving  genetic  potential  in  developing  countries through  crossbreeding may
contribute to methane emissions reductions, the  full potential of this strategy will only be
realized when the strategies for improving the nutrition of the animals are also implemented.
Although it is not as effective as crossbreeding,  selective breeding among indigenous animals
is  simple and inexpensive, but it has been largely  neglected.
6.5.2 CONTINUED GENETIC IMPROVEMENT IN DAIRY CATTLE

The major dairy countries have well established breeding programs that will lead to continued
genetic improvement in dairy cattle.  This has primarily occurred in developed countries, but

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RUMINANT LIVESTOCK                                                              6 - 35
can be adapted to  developing countries and expanded in these  regions.   The breeding
programs generally  lead to the selection of  sires and cows  with  economically important
heritable traits, such as: milk composition (depending on milk pricing and marketing in the
individual countries); milk production; stature; udder support;  legs and feet; milking speed;
birth weight; temperament; and fertility (Ensminger, 1980).

For example, artificial insemination (Al) techniques have enabled improved genetic material
from proven sires to be spread quickly throughout dairy herds. However, the availability of
semen from the best bulls  is limited, which effectively restricts the rate of improvement of
genetic potential.  In  the future, embryo cloning and transplanting techniques may enable the
genetic material from  superior producing  cows  to also be made available  more widely.
Currently, embryo cloning and transplanting are not used commercially.  Similarly, research
is underway to develop methods of significantly increasing the semen that can be obtained
from bulls (Senger, 1992). These  methods, once  developed, could help to increase the rate
of improvement of genetic potential, and consequently reduce methane emissions.

Continued genetic improvement will reduce methane emissions per unit product. The extent
of these reductions has not been estimated at this time. The rate of improvement (and hence
emissions reductions) will be influenced, in part, by dairy pricing and production policies.
6.5.3 TRANSGENIC MANIPULATION

In the long term, transgenic manipulation, the transfer of genetic material from one species
to another, holds promise as a method for dramatically improving the productivity of domestic
livestock,  including large  ruminant animals.  Transgenesis research is largely aimed at
developing new  genomes through the manipulation of genetic material using recombinant
DNA, embryo manipulation, and embryo transfer techniques (Leng, 1991b).

To date, emphasis has been placed on developing techniques for introducing DNA that will
promote the  expression of growth hormone.   Growth has  already  been accelerated in
transgenic  mice carrying genes  that lead to the production  of  growth hormone or the
expression of growth hormone releasing factor (Allen, 1988). These characteristics have been
shown to be transmittable to subsequent  generations.  Considerable  research  remains,
however, before transgenic manipulation is used commercially in food  producing animals.
6.6   Improved Reproduction

Many ruminant animals are maintained for purposes of producing offspring. For example, in
the United States and Australia, tens  of millions of cows are maintained for the production
of calves for beef production.  Similarly, in India, millions of cows and she-buffalo  are
maintained for producing bullocks for  use as draft animals.

By  improving the reproductive  efficiency of the relevant  populations of cows, methane
emissions per unit product can be substantially reduced.  In many cases, there is substantial
opportunity for improving reproductive efficiency. Three strategies are being  pursued  for
improving reproduction directly and  are  described in this  section:   twinning; embryo

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transplant; and artificial insemination and  estrus synchronization.  In many cases, the full
costs and emissions reduction benefits of  these strategies have  not been assessed at this
time.

Additionally,  several strategies discussed  previously will improve reproduction  as a side
benefit.  For  example, improved animal nutrition  due to feed processing and/or strategic
supplementation can reduce age at first calving and inter-calving intervals substantially (Leng,
1991 a).  Similarly, targeted supplementation to eliminate key mineral deficiencies has been
demonstrated to improve reproductive efficiencies in the U.S.
6.6.1 TWINNING

Twinning holds tremendous promise of reducing the number of cows required to produce a
given number of calves.  Because cows account for a significant portion of total emissions
in some regions, emissions reductions can be sizable as a result of twinning.

To date, selection for natural twinning has not held much promise because the heritability of
twinning is low (Ensminger,  1987).   Additionally,  under current management conditions
twinning has not been a desired characteristic among brood cows because:

   • heifers born twin with a bull are often sterile;
   • twin calves are generally lighter than single-birth calves;  and
   • cows that produce twins are more difficult to re-breed the following season.

Strategies for improving the productivity of twin births are being developed.  Techniques to
inhibit the hormones that suppress twinning have been developed,  enabling twinning to be
promoted or prevented as appropriate.  For example, in years with excellent pasture conditions
twinning may be promoted because adequate nutrition is available.  In years of poor pasture
conditions, single births would be desirable.

Options for improving the nutrition of cows carrying twins and of the twin calves are also
being developed to reduce the rate of stillbirths associated with twinning and to help ensure
that the calves grow and mature quickly.

At  this  time,  twinning  is  not  practical  for  commercial  operations.    Cost-effective
commercialized techniques for twinning are likely to be available in the mid-term (after 1995).
The techniques will likely be  applicable to commercial beef production situations  in which
there is reasonably good contact with the animals and for which conditions are not too harsh.
6.6.2 EMBRYO TRANSPLANTS

There is great opportunity for increasing the efficiency of production through technological
advances in reproductive physiology. If successfully applied, recently developed techniques
for super-ovulation  and the transfer of embryos can produce offspring that are uniform in
productive capacity, growth characteristics and quality. As artificial insemination has provided
the means  to multiply  the value of genetically superior males, embryo transfer will do the

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RUMINANT LIVESTOCK                                                              6 - 37
same for females.  Advantages are that calves  with  outstanding  genetic merit can be
produced by foster cows of lesser quality, and superior cows are relieved of the burden of
long pregnancies.  Because of it's  technological  complexity, the applicability of embryo
transfers at this time is mainly limited to highly managed dairy and beef operations in
developed countries.
6.6.3 ARTIFICIAL INSEMINATION AND ESTRUS SYNCHRONIZATION

Artificial insemination (Al) and estrus synchronization (ES) are well-known and established
techniques used in many regions to improve the reproductive performance of cows.  Al has
been widely adopted in dairying in the major dairy countries.  The advantages of Al include
(Ensminger, 1987):

   •   Al eliminates the need to maintain many sires, thereby reducing costs;
   •   Al enables the superior genetic potential  of a single sire to be spread among many
       progeny;
   •   Al eliminates loss of reproduction efficiency due to sterile sires; and
   •   Al helps reduce the spread of diseases associated with mating activities.

Estrus Synchronization has also become widely used. The benefits of ES include:

   •   ES enables embryo transplants to be performed;
   •   ES improves the cost-effectiveness  and simplifies Al administration; and
   •   ES facilitates pregnancy testing, thereby reducing the maintenance of cows that have
       been unable to become pregnant.

A range of products are currently available for promoting ES reliably. The effectiveness of the
products  has  been  demonstrated,  although  results  will depend on individual  herd
characteristics, such as nutrition and disease control. Expanded use of Al and ES can reduce
methane emissions. However, the extent of the emissions reduction has not been evaluated
to date.
6.7   Other Strategies

A  variety of  other strategies have  been identified for reducing  methane emissions from
ruminant animals. Further analysis is required to quantify their potential costs and emissions
reduction benefits. Several are summarized below.
Milk Marketing in Surplus-Producing Countries

Several regions routinely produce more milk than is sold, including the EC, U.S., New Zealand
and Australia. Excess quantities are generally stored, in some cases for long periods of time.
These dairy surpluses are largely a consequence  of the  farm policies implemented  in these
regions. Considerable discussion has been and is taking place to identify options for reducing
this over-supply.

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6 - 38                                                              RUMINANT LIVESTOCK
Reductions in the production of dairy products in these regions can reduce methane emissions
from dairy animals.  If productivity per cow is maintained while total regional production is
reduced, total methane emissions will decline by an amount equal to the reduction in
production.   If, however, total reductions  in production are accomplished principally by
reducing production per cow, methane emissions may only decline slightly.

One strategy for reducing the dairy surplus is to decrease the priority given to the production
of milk fat, and increase the  importance of non-fat milk solids. The basis for this approach
is that in the U.S., for example, the existing surplus is principally in milk fat production. By
changing the milk pricing system to de-emphasize fat production, farmers will take steps to
produce milk with less fat and more non-fat solids.

Such a milk pricing policy change is compatible with reducing methane emissions because the
animal diets  that promote fat production  are  also relatively high in  roughage.   Reduced
roughage  diets will decrease fat production,  and  are also  expected to  reduce methane
emissions.  Consequently, a  policy change that is desirable for purposes of reducing the fat
surplus may also help to reduce methane emissions.
Disease Control

Morbidity is an important limiting factor in many animal production systems.  In many areas,
veterinary  care  is  not available,  and  animal production  and  profitability  suffer  as  a
consequence.  Improved disease control through the development of vaccines will  help to
reduce morbidity and improve animal production.

Various programs are in place to improve animal disease control in most regions of the world.
These programs will reduce methane emissions per unit of product as a side benefit.
Beef Marketing: U.S.A.

The  U.S. beef industry is re-orienting its marketing toward a system called  "Value Based
Marketing." The current beef marketing system has been accused of harboring inefficiencies
due to the historical working relationships that exist among livestock producers, meat packers,
and retailers. As a consequence, the industry does not produce meat as efficiently as possible
given consumer tastes. For example, the industry appears to produce more fat than is desired
by consumers.

In promoting Value Based Marketing, the industry plans to tie the production system closer
to the consumer. Improved communication among retailers,  packers, and producers is one
goal.  Additionally, objective meat grading  instruments are under development.

Value Based Marketing should help to make the U.S. beef industry more efficient. It has been
estimated,  for instance, that about 2 billion pounds of excess trimmable fat are produced
annually, and that the industry can save at least $2 billion annually through its elimination
(NCA et al., 1990).  With the proper Value Based incentives  in place, this fat will be
eliminated, and methane emissions will be reduced. Additional efficiency improvements are
expected that will also reduce  emissions.

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RUMINANT LIVESTOCK                                                              6 - 39


6.8  References

Contributions were made by:

   R. Bowman, AT International, U.S.A.

   P.M. Byers, Professor, College of Agriculture and Life Sciences, Texas A & M University,
   U.S.A.

   Gary Evans, USDA Global Change Program, U.S.A.

   Michael Gibbs, Livestock Expert, ICF Consulting Associates, Inc., U.S.A.

   R.A. Leng, Director, Institute of Biotechnology, University of New England, Australia


Additional information may be found in the following:

Allen, Ronald (1988), "Muscle Cell Growth and Development," in Designing Foods, National
Research Council, National Academy Press, Washington, D.C., pp.  142-162.

Blayney, D.P. and R.F. Fallert (1990), Biotechnology and Agriculture: Emergence of Bovine
Somatotropin (bST), U.S. Dept. of Agriculture, Washington, D.C., Staff Report AGES 9037.

DeGraff D.L. (1991), Monsanto Agricultural  Company, personal communication, October
1991.

Ensminger, M.E.  (1980), Dairy Cattle Science. The Interstate Printers & Publishers, Danville,
Illinois.

Ensminger, M.E. (1983), The  Stockman's Handbook.  The Interstate Printers &  Publishers,
Danville, Illinois.

Ensminger, M.E.  (1987), Beef Cattle Science. The Interstate Printers & Publishers, Danville,
Illinois.

Fallert, R.F.,T. McGuckin, C. Betts, G. Bruner (1987). bST and the Dairy Industry:  A National.
Regional, and Farm-level Analysis.  Economic  Research Service, U.S.  Dept. of Agriculture,
Washington, D.C., AER #579.

Fleming,  Euan (1991),  Improving  the  Feed  Value of Straw Fed to Cattle  and Buffalo,
Australian Center for International Agricultural Research, Canberra, Australia.

Habib, G., S. Basit Ali Shah, Wahidullah, G.Jabbar, Ghufranullah (1991), Importance of Urea
Molasses  Blocks on  Animal Production (Pakistan), International  Atomic Energy Agency,
International Symposium on Nuclear and Related Techniques in Animal Production and Health,
Vienna, Austria,  15-19 April 1991.

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6 - 40                                                             RUMINANT LIVESTOCK
Hendratno, C., J.V. Nolan and R.A. Leng (1991), Importance of Urea Molasses Multinutrient
Blocks for Ruminant Production in  Indonesia,  International  Atomic  Energy Agency,
International Symposium on Nuclear and Related Techniques in Animal Production and Health,
Vienna, Austria, 15-19 April 1991,

Jasiorowski, H.A., M. Stolzman, and Z. Reklewski (1988), The International Friesian Strain
Comparison Trial: A World Perspective, Food and Agriculture Organization of the United
Nations, Rome, Italy.

Leng, R.A. (1991 a).  Improving Ruminant Production and Reducing Methane Emissions from
Ruminants by Strategic Supplementation. U.S. Environmental Protection Agency, Washington,
D.C., EPA/400/1-91/004.

Leng, R.A. (1991b), Application of  biotechnology to nutrition  of animals  in developing
countries. FAO Animal Production and Health Paper 90, Food  and Agriculture Organization of
the United Nations, Rome, Italy.

Leung, F.C. (1988), "Hormonal Regulation of Growth,"  in Designing Foods, National Research
Council, National Academy Press, Washington, D.C.,  pp. 135-141.

Muir, Larry A. (1988),  "Effects  of Beta-Adrenergic Agonists  on Growth and  Carcass
Characteristics of Animals," in Designing Foods, National Research Council, National Academy
Press, Washington, D.C.,  pp. 184-193.

NCA et al. (National Cattlemen's Association, Beef Industry Council, and Beef Promotion and
Research Board) (1990), "The War on Fat!" A Report  from the Value Based Marketing Task
Force, August.

National Institutes of Health (NIH) (1990), Bovine Somatotropin: Technology Assessment
Conference Statement, December 5-7, 1990.

Nour, A.M. (1987), "Rice  Straw and Rice Hulls in Feeding Ruminants in Egypt," in Utilization
of Agricultural  Bv-Products as Livestock Feeds in Africa. International Livestock Center for
Africa, Addis Ababa, Ethiopia, pp. 53-61.

Office of Technology Assessment (1991), U.S. Dairy Industry at a Crossroad: Biotechnology
and Policy Choices - Special Report, Washington, D.C., OTA-F-470.

Owen E., and M.C.N Jayasuriya (1989),  "Recent Developments on Chemical Treatment of
Roughages and their Relevance to Animal Production in Developing Countries," in Feeding
Strategies for Improving Productivity of Ruminant  Livestock  in  Developing  Countries,
International Atomic Energy Agency, Vienna, Austria, pp.  205-230.

Perdok, H.B.  et  al.  (1988),  "Improving livestock production  from straw-based diets," in
Increasing Small Ruminant Productivity in Semi-arid Areas. E.F. Thomson and F.S. Thomson,
eds., ICARDA, pp. 81-91.

M. Saadullah (1991), Importance of Urea Molasses Block Lick and Bypass Protein on Animal
Production (Bangladesh),  International Atomic Energy Agency, International Symposium on

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RUMINANT LIVESTOCK                                                            6 - 41
Nuclear and Related Techniques in Animal Production and Health, Vienna, Austria, 15-19 April
1991.

Senger, Phil (1992), "Sperm production doubled in rats - are bulls next?," Hoard's Dairyman,
Vol. 137, No. 1, January 10,  1992.

USDA (U.S. Department of Agriculture) (1987), Economic Impacts of the European Economic
Community's Ban on Anabolic  Implants. Appendices A-D, Food Safety and Inspection Service,
October 1987.

USEPA (United States Environmental Protection Agency) (1989). Reducing Methane Emissions
from Livestock: Opportunities  and Issues. EPA/OAR, Washington, D.C., EPA/400/1-89/002.

Van Soest, Peter  J., (1987), Nutritional  Ecology of the Ruminant. Comstock Publishing
Associates, Ithaca, New York.

-------
CHAPTER SEVEN
LIVESTOCK MANURE
7.1   Background

Methane Production and Emissions

Methane is produced during anaerobic decay of the organic material in livestock manure. The
organic component of livestock manure contains carbohydrates, proteins, and lipids that can
supply the energy needs of microorganisms. An empirical measure of the organic component
is the volatile solids (VS) content.  Methane may be produced when bacterial decomposition
of volatile solids is allowed to occur in an oxygen-free (anaerobic) environment (see Exhibit
7-1).  The end products of the complete anaerobic process are methane gas (CH4), carbon
dioxide gas (CO2), other trace gases, and a slurry containing bacterial mass and undigested
solids.

The quantity of methane generated depends on certain physical, chemical and environmental
factors.  Physical and chemical factors which directly affect potential methane production
include  the  quantity of  manure, the  proportion  of the manure  that  is  available  for
decomposition (i.e., %VS), and the biodegradability of the manure.  These factors will vary
by animal species and diet. For example, cattle fed a high energy grain diet produce a highly
biodegradable manure with a high %VS, whereas cattle fed a roughage diet will produce a
less biodegradable manure containing more complex organics such as cellulose, hemicellulose,
and lignin. Under similar conditions, the manure of cattle fed the high energy corn-based diet
will produce about twice as much methane as the manure of the cattle fed a roughage diet
(USEPA, 1992). Also, manure produced by ruminants (e.g., cattle) will, in general, have a
lower methane producing capacity than the manure produced by monogastrics (e.g., swine).

Manure  management practices and climatic variables are  environmental factors  which
influence methane  production in  two  important ways.   First, the management system
determines  whether anaerobic conditions will exist.  For example, long  term pit storage
promotes anaerobic conditions, whereas uncollected manure from grazing livestock will likely
decompose in the presence of oxygen,  and thus without significant methane production.
Second, management systems determine the water content of the manure.  Moisture content
is critical because  water provides a reaction medium  and  is required for the  biological
decomposition of the volatile solids.  Liquid/slurry systems handle manure with less than 20
percent total solids, and have the highest methane potentials. Solid systems handle manure
with total solids above 20 percent. The percent total solids (%TS) of current management
practices is an important factor in  choosing an appropriate methane recovery strategy. The
effects of manure management systems on potential methane emissions are summarized in
Exhibit 7-2.

The most important climatic variables are temperature and moisture.   Bacteria are greatly
affected by temperature, and this is particularly true of methanogenic bacteria.   Methane
production is maximized between 40 and 60 °C, but can occur between 4 and 75 °C (Safley,
1990).  Moisture is important to the degree that it affects the water content of the manure
and the  percent TS (described above).

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7 -2
    LIVESTOCK MANURE
                                      Exhibit 7-1

                             Phases of Anaerobic Digestion
                     .  STAGE 1  .
                      Fermentative
                  Fat-decomposing


                  organisms
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                  Protein-decomposing


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              Fats +  Cellulose + Protein =  VS
__ STAGE 2
   Acetogenic
  STAGE 3_
Methanogenic
Exhibit 7-2
Impact on Methane Potential by Manure
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-------
LIVESTOCK MANURE                                                                 7 - 3
In addition to producing  methane, livestock manure can be  harmful to humans and  the
environment. Manure run-off from confined livestock operations degrades both ground and
surface water quality, contaminating drinking water and leading to eutrophication of rivers and
lakes.  Noxious odors associated with livestock manure impair air quality.  Furthermore,
livestock manure  can be  a  breeding ground  for  human pathogens and disease vectors.
Improving the management of livestock manure can greatly reduce these problems.
Methane Recovery Strategies

Methane emissions constitute a wasted energy resource which can be recovered by adapting
manure management and treatment practices to facilitate methane collection. This methane
can be used directly for on-farm energy, or to generate electricity for on-farm use or for sale.
The other products of anaerobic digestion, contained in the slurry effluent, can also be utilized
in a number of ways, depending on local needs and resources. Successful applications include
use as animal feed and aquaculture supplements, in fish farming, and as a crop fertilizer.

Additionally,  managed anaerobic decomposition is a very effective method of  reducing the
environmental and  human health problems associated  with manure  management.  The
controlled bacterial decomposition of the volatile solids in manure reduces the  potential for
contamination and eutrophication due to runoff (Safley, 1991). The organic nitrogen content
of the manure is largely converted to ammonia, which is readily utilized by plants and is the
primary constituent of commercial fertilizers (Loehr,  1988). Anaerobic decomposition also
significantly reduces pathogens (Edgar and Hashimoto, 1991), and methanogenesis eliminates
most noxious odors. Thus, there are significant  incentives for  improving livestock manure
management practices.

Successful  methane recovery  strategies have  been demonstrated under  a variety  of
conditions.  In each case, methane recovery strategies improving anaerobic decomposition
were tailored to recognize important  regional factors. For example, the ambient temperature
and climate  --  e.g., tropical, temperate  --  will greatly affect the  performance of certain
designs.  Additional important factors include economic, technical and material resources;
existing manure management practices; regulatory requirements; and the specific benefits of
developing an energy resource (biogas) and a source of high quality fertilizer.   Choosing an
appropriate  strategy is vital to meeting the varied  needs  and gaining the acceptance of
livestock farmers.

The following strategies are described in this report:

   Covered Lagoons: The treatment of manure in lagoons is associated with relatively large
   scale intensive farm operations.  Manure solids are  washed out of the livestock housing
   facilities with large quantities of water, and the resulting slurry, containing a low percent
   total solids, flows into lagoons. The anaerobic conditions treat manure and usually result
   in significant methane emissions, provided temperatures remain high enough.  Placing an
   impermeable floating  cover over the  lagoon and  applying negative  pressure effectively
   recovers methane which can be utilized for electricity generation, farm heating, and
   refrigeration. Lagoons are most common rural North America, Europe, and less populated
   regions of Asia and  Australia.

-------
7 - 4                                                                 LIVESTOCK MANURE
   Small Scale Digesters:  Digesters are designed to enhance the anaerobic decomposition
   of organic  material and to maximize methane production and recovery.   Small  scale
   digesters typically require a small amount of manure and are relatively simple to build and
   operate.  As such, they are an appropriate strategy for regions with technical, capital, and
   material resource constraints.  Due to the rising cost of commercial fertilizers, the recovery
   of high quality fertilizer from digesters can be an even more important benefit than the
   energy supplied from biogas.  A number of different digester designs have been developed.
   These designs are not heated, and while they can operate in colder regions, they are more
   appropriate for temperate and tropical regions.

   Larger Scale Digesters:   The larger, often more  technologically  advanced digesters
   described in this section are usually heated, have larger capacities, require greater capital
   investment, and in general are more complex to build and operate.  However, advanced
   designs can greatly  improve  the  performance of livestock manure digesters, and can
   operate in colder regions. This strategy integrates the operation  of a digester with current
   manure management practices at large animal farms, typically in more developed regions.
   The two primary digester  designs are Complete Mix and Plug  Flow digesters.   Manure
   quantity and the percent total solids of the manure are important criteria  for determining
   the appropriate technology.
Exhibit 7-3 summarizes these strategies for reducing  methane emissions from livestock
manure, which are described in more detail  in the individual assessments.  Each technical
assessment contains the following sections:

   • Recovery Technology Description;
   • Costs;
   • Availability;
   • Applicability;
   • Barriers; and
   • Benefits.

-------
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-------
7 - 6                                                                LIVESTOCK MANURE
7.2  Covered Lagoons

A common method of removing manure from confined livestock facilities involves flushing the
floors with large quantities of water. The resulting liquid manure is stored in a large lagoon
where anaerobic conditions  promote decomposition of the volatile solids.   Although this
method effectively treats the manure, it also produces large quantities of biogas (methane and
carbon dioxide) which is usually released into the atmosphere.  The strategy presented here
recovers this potentially useful gas by placing an impermeable cover over the manure lagoon.
Successful applications of this strategy have yielded sufficient methane to satisfy the energy
needs of a farm without disrupting existing manure management procedures.  Methane
recovery efficiencies exceeding 80 percent have been achieved.
Recovery Technology Description

Flush water manure management systems are common on animal farms where large numbers
of livestock are confined, and spend significant periods of time inside (e.g., dairy feedstalls
and milking parlors, and intensive swine operations). In these systems, animal  manure is
removed from the building by periodic flushing with large quantities of water (as opposed to
scrape systems).  The advantages of flush  systems over alternative techniques  are better
cleanliness, less wear on barn equipment, and lower labor requirements. However, the use
of large volumes  of water significantly increases the total volume of slurry that must be
handled and reduces the percent total solids in the resulting waste stream.

Percent total solids from flush systems are typically less than 1  percent, which is too low for
effective use in  a conventional digester.  Instead, these liquid wastes are often stored in large
lagoons which provide a simple and cost-effective treatment system.  Under the anaerobic
conditions that  often occur in the lagoons, bacteria reduce the biologically active component
(volatile solids)  of the manure;  the remaining liquid  can be drawn off for application as a
fertilizer.  However, because the decomposition in  the lagoons is anaerobic, methane and
carbon dioxide  (biogas) are released.  This gas can be a  valuable energy resource.

   Methane Recovery:  The biogas is captured by placing a floating, impermeable cover over
   the lagoon,  or the portion of the lagoon with the highest methane flux.  This cover must
   not only be impermeable, but must also be sealed at the edges to prevent any influx of air
   and subsequent dilution  of  the biogas  (Safley and  Westerman, 1990).  The cover is
   constructed of a rubber-like material (e.g., hypalon) which rests directly on solid floats laid
   on the surface of the lagoon (see Exhibit 7-4).  The cover is anchored along the edge of
   the lagoon with a concrete footing, and  is held in position with ropes.  Where the cover
   attaches to  the edge of the lagoon, an air tight seal is constructed  by placing  a sheet of
   the impermeable cover material over the  lagoon bank and several meters into the lagoon,
   and clamping the cover (with the footing) onto the sealed bank. Seals are formed on the
   remaining edges using a two meter deep "curtain" of  material hanging vertically from  the
   edge of the  cover into the lagoon.

   Selective sizing and  placement of the cover can greatly improve cost  effectiveness  by
   reducing capital costs without reducing  recovery efficiency. In most cases, the manure
   solids  will  be concentrated nearest the flush-water inflow  and  will not  be evenly

-------
LIVESTOCK MANURE
7 -7
   distributed across the entire lagoon.  Methane  production per unit area of the lagoon
   surface area will  be higher where the solids are concentrated, and often a significant
   proportion of the total methane emissions can be recovered with a relatively small cover
   area. The design  of the cover naturally lends itself to easy modular expansion.  Mapping
   the sludge depth along the lagoon bottom or floating small (several m2) biogas test units
   can help in determining the optimal cover size and location.
                                     Exhibit 7-4
                   Schematic of a Covered Lagoon Digester System
  Source: Chandler et al., 1983.
   When the cover is in place, biogas produced in the covered area of the lagoon is trapped.
   A collection device, such as a long perforated pipe, is placed under the cover along the
   sealed edge of the lagoon, and the gas is removed by connecting a suction blower to the
   end of the pipe. The blower draws the collected gas out of the cover and delivers it to the
   engine generator  (or other utilization  option).  The blower and collection pipes are sized
   according to the quantity of gas and  the distance from the  lagoon to the engine.

   Utilization Options:  The recovered gas is typically 60 to 80 percent  methane, with a
   heating value of approximately 600 to 800 Btu/cf (22 to 29,000 kJ/m3)  (DOE, 1988).
   The gas can be used in an internal combustion engine generator, a boiler or space heater,
   in refrigeration equipment, or directly combusted as a cooking and lighting fuel.  The gas
   usually must be cleaned to some degree, depending upon the specifications of the end use

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7 - 8                                                                LIVESTOCK MANURE
   equipment.  This processing typically involves the removal of water and moisture in a
   water trap, and the removal of particulates with a filter.  Processing may also be used to
   remove CO2 and any trace corrosive chemicals.

   Significant quantities of medium quality gas can be recovered from livestock  manure
   lagoons.  Techniques and materials for recovering the gas have been developed and
   successfully implemented. Recovered gas can be used in a variety of options to satisfy
   the energy requirements of the farm operation.

   •   Internal Combustion Engines. Electricity generation with an internal combustion engine
       is the most convenient option for large, industrialized farms.  These engines are readily
       available in a variety of sizes, are reliable, and can easily be connected to an electricity
       generator.  Electricity generated in this manner can replace energy purchased from the
       local grid, or can be sold  directly to  the local electricity  supply system.  In addition,
       waste heat from these engines can provide heating or warm water for farm use (DOE,
       1988).

       For example, a 75 kW generator was powered by 700 to 1000 m3/day (25 to 36,000
       cf/day) of biogas, with an actual electricity output of 40 to 70 kW  (Chandler et al.,
       1983). This quantity of gas was produced from a one acre lagoon, 6 meters (20 feet)
       deep at a 1000 head swine farm; the  lagoon was 1 /3 covered. Typical energy demand
       at a 1000 head swine farm ranges from  50 to 110 kW.

   •   Boilers. Boilers and space heaters fired with biogas produce heat for use in the farm
       operations.  Although this may be an efficient use  of the gas, it is  generally not as
       convenient an energy source as electricity. Nevertheless, in some situations it may be
       a viable option (DOE,  1988).

   •   Chilling/Refrigeration.  Dairy farms use considerable amounts of energy for refrigerating
       milk.   Gas-fired  chillers  are  commercially  available and can  be used  for  milk
       refrigeration (DOE, 1988). For some farms in the U.S. this may be the most profitable
       option for methane utilization (Roos, 1992).
Overall project economics will depend on a number of site specific factors, such as the details
of the manure management system, farm energy needs,  energy costs,  and regulatory
requirements.  In particular, the potential amount and quality of recoverable methane will vary
greatly and will have a large effect on the revenue (or savings) realized.  Recognizing these
variable factors, this section presents ranges for component costs, and some representative
economic analyses.

    Lagoon Covers:  Installation costs for the impermeable lagoon covers range from  US $15
    to 30/m2 (approx. $1.3 to 2.7/ft2).  Once installed the maintenance costs are  minimal
    (Chandler et al., 1983).

    Biogas Handling Equipment:  Capital  costs for suction blowers,  plastic piping, and
    purification equipment are approximately $0.1 6 to $0.33  per kW of capacity (or $4-8 per

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LIVESTOCK MANURE                                                                 7 - 9
   kWh of electricity generated daily). However, this figure should be taken as a rough guide,
   as actual cost will depend upon many factors including the distance the gas is transported,
   and specifications of the purification system.

   Utilization Options:  Capital costs for internal combustion engine generators are typically
   $400 to 800/kW (e.g., $40-50,000 for a 75 KW engine) (Chandler et al., 1983; Anderson,
   personal communication; Moser, personal communication).  Operation and maintenance
   costs are estimated at 1.5 to 20 per kWh.

   Boiler costs can be estimated for a given boiler capacity as follows: (BTU's available per
   hour)*(boiler efficiency)*(cost per BTU).  For example, a typical 150,000 BTU/hr boiler
   with an efficiency  of 80 percent, and a cost per BTU of $0.01, would cost $1,200 to
   install (Woodbury,  personal communication).

   Chillers will cost from $700 to $1,100 per ton of cooling capacity, depending upon the
   efficiency of the system.  A typical cooling requirement would be 0.0165 ton/hour/milking
   cow (Woodbury J, personal  communication).

Costs and savings for complete projects have been developed by USEPA and the Tarleton
Research Institute for biogas recovery at Texas dairy farms. At these farms, the manure from
milking parlors is collected using flush systems and the liquid wastes are stored in anaerobic
lagoons.   Even though this  manure accounts for only  10-20  percent of the total manure
produced, the recovery of biogas is economically attractive for  larger dairies (e.g., with over
500  cows) when used to fire absorption chillers to refrigerate milk.  Using manure  from
parlors as well as feed  lanes to generate electricity increases profitability for larger herd sizes.
Typical payback periods for these dairies are two to five years, with  initial investments of
approximately $75 to  $90 per head (Roos, 1992).

Cost-effectiveness of biogas recovery has also been demonstrated for swine facilities. For
example, a case study of a successful project  at a California  swine farm  with  1000 sows
farrow to finish produced the figures shown in Exhibit 7-5.  Initial capital costs (in 1981) for
the entire system were $89,000 (Chandler et al., 1983).
Availability

The technology for recovering methane (biogas) from covered lagoons uses materials and
equipment that are commercially available.  Similarly, utilization options use equipment that
is readily available.
Applicability

The storage of livestock manure in lagoons is most common at large farms with confined
rearing practices, and this strategy is designed to be appropriate for these farms. The volume
of methane generated in the lagoon must satisfy a large enough portion of the farm's energy
needs to make the  project attractive when offsetting electricity  or other energy costs, or
replacing other fuels.

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7- 10
LIVESTOCK MANURE
Additional factors that encourage the adoption of this strategy include:

   •   Increasing prices for commercial fertilizers.  The liquid fertilizer byproduct of lagoon
       storage is cheap, convenient, and high quality.

   •   Environmental regulations controlling livestock manure runoff may result in increased
       anaerobic storage and larger regulatory compliance costs at large farm operations (e.g.,
       in the U.S.).

Currently, anaerobic lagoons are most common in rural North America, Europe, and to some
extent in Asia and Australia (USEPA, 1992). However, this strategy will become increasingly
applicable as the degree of industrialization and the use of confined rearing practices increases
in other regions  of the world.
Exhibit 7-5
Covered Lagoon Biogas Recovery System
Capital Investment
Lagoon Cover
1C Engine and Generator
Biogas Handling
Utility Interconnect
Building

Total Revenue (1st Year)
Total Operation and Maintenance Costs (1st Year)

Expected Payback Period
Internal Rate of Return
$89,000
$37,380
$40,940
$7,120
$1,780
$1,780

$36,530
$8,623

2.9 Years
34%
Source: Chandler et al., 1983.
Barriers

Any change in current manure management practices must be accepted by farmers if it is to
be  successful; natural  resistance  to  adopting  new techniques  is a  significant  barrier.
Therefore, this strategy must prove  that it is compatible with existing practices and levels of
labor intensity, that it is economically sound, and technically reliable. The continued success

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LIVESTOCK MANURE                                                               7-11
of technically sustainable demonstration projects will be important in overcoming the barrier
of acceptance.
Benefits

In addition to reducing methane emissions, the recovery of biogas from covered lagoons can
result in the following benefits:

   •  Effective treatment of livestock manure.  The treatment of manure in anaerobic
      lagoons reduces runoff problems, and reduces pathogen levels (Loehr, 1984).

   •  High quality fertilizer production.  Anaerobic  treatment of manure produces a liquid
      fertilizer with a high inorganic nitrogen (NH3 ammonia) content (UNEP, 1984).

   •  Improved energy use.  Biogas is a cleaner burning fuel than most of the fossil fuels it
      replaces  (i.e., coal and oil).  This reduces the emissions of  particulates, nitrogen
      oxides, and sulfur oxides.  Furthermore, biogas is a renewable and a less carbon
      intensive than coal or oil, reducing net carbon dioxide (a  greenhouse gas) emissions
      into the atmosphere.

   •  Improved aesthetic quality. Covering lagoons improves control over flies and odors.
                       Covered Lagoons

                       • methane reductions of up to 80 percent
                       • medium quality gas (60-80%)
                       • moderate capital investment
                       • reduced energy costs
                       • technology currently available
                       * minimum maintenance requirements
                       • clean energy source
7.3  Small Scale Digesters

Appropriately designed anaerobic  digesters can provide significant benefits for developing
countries. The anaerobic digestion of livestock manure reduces human and environmental
health problems associated with pathogens and disease vectors, produces cheap fertilizer and
other valuable products (e.g., animal and fish feed), and creates a renewable and convenient
energy source (biogas) (U.N. Guidebook, 1984). Small scale digesters are typically up to 100

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7- 12
                                          LIVESTOCK MANURE
m3 (3,600 cubic feet) in total capacity, or a daily capacity of 3.5 m3 (130 cubic feet) capable
of handling about 1,800 kg of manure per day. Digesters can be successfully integrated with
existing agricultural practices, while improving sustainability by returning  nitrogen and trace
minerals to  the land, improving soil quality, and  reducing erosion (Pimental, 1975).  This
assessment describes the variety of existing designs, and how design and implementation can
best be tailored to important local factors such as climate and resource availability. These
systems are usually not heated and have the best success in the tropics.
Recovery Technology Descriptions

Anaerobic digesters utilize  the  ability of certain  bacteria to digest the biologically active
component of livestock manure. Therefore, digesters must maintain suitable conditions for
the bacteria if they are to be effective.  Exhibit 7-6 illustrates the basic components of a
digester, including a mixing pit, the digester, a gas holder (typically integral to the reactor),
and effluent handling. The design of these components must strike a balance between using
regionally appropriate materials and technical skills and maximizing the performance of the
digester, since it is not beneficial to build  an inexpensive and  simple digester if it is not
technically reliable over time, or to "over-design" a system that is not practical to build and
operate with local resources.   Several designs  are  available to fit local  variables while
maintaining digestion efficiency (Gunnerson & Stuckey, 1986).
                                      Exhibit 7-6
                         Components of an Anaerobic Digester
                                                          Manure Handling
                   Manure
                  Collection
Mixing
 Pit
Displacerrjent
   Tank
                                       Gas Holder
                                                                Fish
  Note: In most designs, the gas holder is a part of the digester vessel.
This section classifies the types of digester systems available, outlines important operational
factors and their effect on efficiency, and describes the utilization of the digestion products.
The digesters described here are similar in  concept to those described in the next section.

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LIVESTOCK MANURE                                                                7-13
"Larger Scale Digesters,"  although the designs are typically simpler to build and operate.
Digesters can be classified by the arrangement of their components,  with the distinguishing
characteristic being the method of storing  the  biogas  produced in the  reactor chamber
(digester):

   Floating Gas Holders:  These systems collect biogas by building a steel, fiberglass, or
   ferrocement "floating" holder to form the roof of the digester chamber. This cover is able
   to move vertically along internal or external guides. As gas is produced the holder rises
   to accommodate the increased volume ("floating"  on the pressurized gas); when gas is
   drawn off, the holder falls, maintaining a constant gas pressure. An air tight water or
   manure seal is formed around the bottom of the holder (see Exhibit 7-7). These systems
   are commonly  known as Mexican, Brazilian,  Indian or KVIC, and Taiwan designs (UN,
   1984).

   Floating gas  holder systems have  been installed in several  countries, especially India.
   Experience indicates that corrosion often reduces the effective lifetime of steel floating
   covers.  Furthermore,  the construction of the steel holder and guides is a relatively
   complicated and expensive process (compared to other systems described below), and will
   at best only be feasible in regions with manufacturing capability.
                                     Exhibit 7-7
                             Floating Gas Holder System
                Mixing Pit
                                                 Displacement Pit
                                                              Storage
   Flexible Bag Holders:  These systems are perhaps the simplest to construct and operate.
   A large rubber bag both contains the decomposing manure and collects the biogas.  As
   biogas is produced and consumed, the flexible bag expands and contracts according to the
   volume of gas it contains. (The basic design is similar to Plug Flow systems described in
   "Larger Scale Digesters.")

   The rubber bags, typically made from a residual manure of the bauxite industry known as
   "red mud plastic,"  originated in Taiwan and  have potential for application  in certain

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7 - 14
LIVESTOCK MANURE
   conditions by virtue of their low cost, ease of production, transport, and having virtually
   no on-site  construction requirements.   Some  projects have reported that the  rubber
   degrades when exposed to sunlight for long periods, and in general is more likely to be
   damaged through normal wear and tear, although this may be true only in some cases.

   Fixed Dome:  Fixed dome systems combine the digester and gas storage components in
   a single, fixed unit.  This allows the  entire unit to be constructed from masonry (e.g.,
   brick, cement hollow blocks, ferrocement) and with no moving parts.  This greatly reduces
   the complexity and cost of the system. A reliable, gas tight dome can be achieved with
   a paraffin wax application,  making this system extremely reliable overall (Roos,  1988).
   As  gas is  produced  it exerts a  pressure of  up  to one  meter  water column (0-2
   pounds/square inch) on the digester contents; this pressure forces some slurry into the
   displacement pit, eventually balancing the gas pressure (see Exhibit  7-8).  The simplicity
   of construction and operation make this system extremely promising. The main drawback
   of this system is the variable gas pressure.
                                     Exhibit 7-8
                            Fixed Dome Digester System
                 Mixing Pit
                                                Displacement Pit
                                                             Storage
   These types of digesters can be built in a variety of sizes; the capacity can be tailored to
   fit the application. Typical sizes range from a 4 to 5 m3 design, suitable for a single family
   running a small farm, up to 75 to 100 m3 and larger (Roos, 1988). Basic digester systems
   will produce about 0.5 to 1  m3 of biogas  per m3 of digester volume.  (Although larger
   capacities are feasible, in practice the initial investment is only justified if more advanced
   design features are included;  see "Larger Scale Digesters").

   For example, a small  family farm might be expected to own 4 to 6 pigs, and may use one
   hectare for  crop production.   The  biogas  produced  in a 4.5 m3  digester, run on the
   livestock manure,  would  provide sufficient biogas  for domestic  cooking, lighting, or
   refrigeration, in addition to fertilizer and animal feed supplements from the slurry effluent
   (Roos, 1988).

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LIVESTOCK MANURE                                                                7-15
   Although the exact details of operation will depend upon the system size and design, the
   common goal of each system is to manage the natural anaerobic digestion to promote
   efficient decomposition  of  the  livestock manure.  The important factors  controlling
   digestion efficiency, and the ability of these systems to affect them, are discussed below.

   •   Manure Handling and Composition.  The water content of the manure entering the
       digester must be controlled to maintain 7 to 9 percent total solids, ideal for ease of
       handling and for digestion efficiency (gas production).  In practice, this requires a 1:1
       dilution of the  raw manure with water.  This dilution can be done in the  mixing pit,
       from which the manure  is transferred to the digester.  The logistics of handling the
       manure must also be considered. Gathering manure in extensive operations  (e.g.,
       pasture grazing) may be impractical; intensive operations where livestock are confined
       in smaller areas facilitate manure handling (Roos, 1992).

   •   Temperature. The systems described here work in the mesophilic range (i.e., 30 to 35
       °C; 60 to 90 °F). Thus, the temperature in the digester should not drop below 30 °C,
       or methanogenesis will decrease markedly. The designs here usually do not involve
       any active heating of the  digester vessel (to the thermophilic range), so maintaining the
       temperature depends upon the ambient temperature and the insulating properties of
       the system; fixed dome systems, with mortar construction, are better insulators than
       other designs.   Additionally, tropical regions are  more suited for simple unheated
       anaerobic  digesters.   (Thermophilic  designs are  more complicated, and are  more
       sensitive to small temperature fluctuations) (Chen and Hashimoto, 1978).

   Utilization of Biogas and Other Products:  Anaerobic digestion yields biogas and a  slurry
   effluent.  With minimal  treatment, these two products are both valuable resources for
   developing countries.  Furthermore, they can be utilized to maximum effect for local
   residential or agricultural purposes.  This allows the operator (e.g., the participating farmer)
   to directly benefit  from the digester, without relying on the sale of products in a cash
   market.

   Biogas is typically  60 to 80  percent methane, with a heating value of 600 to  800 Btu/cf
   (22,000 to 29,000  kj/m3).  The  gas can be used directly for domestic cooking and
   lighting, or can be used in  stationary engines to drive machinery (e.g., water pumps,
   threshers)  or  generate  electricity.  These end uses require  specialized or  modified
   equipment, but many practical designs currently exist. Typical gas requirements for some
   end uses are given below in Exhibit 7-9.  These values can be compared to the following
   approximations: per capita gas consumption is 0.34 to 0.41 m3 per day; a typical family
   of six will use 2.9  m3 per day (Roos, 1988).

   Digester effluent is typically a 2 to 12 percent total solids slurry.  The daily volume of
   effluent is  roughly equal to  twice the daily manure production, because the manure is
   usually diluted with water.  The  effluent contains valuable nitrogen,  minerals, and other
   organic material that improves soil conditions. The slurry can  be treated in a variety of
   ways -- separation into solids and liquids, drying, unseparated. The exact treatment and
   use can be designed to meet particular local needs (see Exhibit 7-10).

   Unseparated effluent can be used directly as a fertilizer, replacing expensive commercial
   fertilizers.  Additionally, separated solids (dried or undried) can be used. If the effluent is

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7 - 16
LIVESTOCK MANURE
   separated, the liquid portion can be used for irrigation.  Alternatively, dried solids have
   been used as a feed supplement for livestock.  The nitrogen contained in the solids is a
   crude protein source, improving digestion efficiency (microbial growth) in cattle, and the
   process enhances vitamin B12 as well (Maramba, 1983). The nutrient content of slurry,
   or the liquid portion, can be used to promote algae growth in fish ponds (Maramba, 1983).
Exhibit 7-9
Gas Requirements of End Use Technologies
Cooking:
small burner
medium burner
large burner
Domestic:
mantle lamp (60W)
refrigerator
Engines:
motive power
electric power

8 ft3/hr
1 0 ft3/hr
1 5 ft3/hr

4-5.5 ft3/hr
.6-1.2 ft3/ft3 volume

16-19 ft3/bhp
21-25 ft3/kWh

.22 m3/hr
.28 m3/hr
.42 m3/hr
,
.11-.15 m3/hr
.6-1.2 m3/m3

.45-.54 m3/bhp
.6-.7 m3/kWh
Source: Maramba, 1983.
Exhibit 7-10
Treatment and Utilization of Digester Effluent

Fertilizer
Irrigation
Feed Supplement
Fish Ponds
Unseparated Effluent
X


X
Solids
X

X

Liquid
X
X

X
Source: Maramba, 1983

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LIVESTOCK MANURE
7- 17
   As a  rough approximation, anaerobic digesters will reduce the potential for methane
   production by two thirds or more, leaving the remaining one third of the compounds that
   can decompose anaerobically in the effluent.  If the effluent is handled under anaerobic
   conditions, such as in a treatment lagoon or tank, then methane may be generated from
   the effluent.  Therefore, where livestock manure is currently managed anaerobically and
   generates methane, efficient digesters with gas recovery systems  may reduce methane
   emissions by up to 70 percent, with larger reductions achievable at longer retention times.
Costs

The initial costs and economic viability of digester systems will vary greatly with the size,
design, and the local availability of resources. As an example  of the economies of scale and
relative differences between various designs and construction techniques, Exhibit 7-11 shows
initial costs for projects carried out in Jamaica.
Exhibit 7-1 1
Digester Construction Costs ($/cubic meter volume)
Digester Type
Fixed Dome - Ferrocement
Fixed Dome - Poured Concrete
Floating Cover
Digester Volume (m3)
4.5
154
178
240
7
110
132
210
20
60
82
130
50
34
68
104
Source: Roos, 1988.
Availability

The digester systems described in this assessment have been used extensively, and the basic
components of each design are well understood.  The information necessary to construct and
operate digesters exists, and can be made available through a combination of government and
private sector technology transfer.
Applicability

The basic anaerobic digester systems described in this assessment are designed for regions
where resource constraints  limit the application of more  advanced technologies.  These
resource constraints include technical and material resources necessary for construction and
long term operation, and also economic resources. Thus, these systems are most appropriate
for rural, agricultural regions in tropical developing countries.

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7-18                                                                LIVESTOCK MANURE
More  specifically,  these systems  are appropriate for  agricultural  areas where  there  are
economic and socio-economic benefits to be gained from the improved treatment of livestock
manure and from the products of anaerobic digestion.  A necessary condition for applicability
is  the availability  of manure  from agricultural  activity.   Integrated livestock  and crop
production are ideal systems, especially where livestock are kept penned near the farm.

Whether considered at a regional or individual level, an important factor is the benefit derived
from the products of digestion.  Biogas provides a renewable and convenient energy source,
making digesters suitable for countries that are net importers of fossil fuels, or where energy
costs are rising significantly. In many regions the value of fertilizer supplies is an even more
significant incentive for implementation.  The price of commercial fertilizers has been rising,
and is projected to rise further in the future. This has strained the ability of small and medium
size farmers  to maintain viable production levels, and also hampers national  economic
performance.  Anaerobic digesters  can help to make these farmers more self-sufficient,, and
reduce the cost of importing fertilizers. Similarly, alternative uses of digester effluent such
as cattle feed and in fish ponds improve these conditions further.

In addition to the tangible benefits of energy and fertilizer supplies, the improved soil condition
and reduced health and environmental problems (e.g., pathogens, air and water quality) should
be accounted for when considering regional and  national plans for implementation.  This is
important because many bacteria  have  become  resistant to anti-biotic treatments (WHO,
1980).
Barriers

Technical reliability and effective system management is essential for successful programs.
Historically, some implementation programs have not ensured that designs are appropriate,
construction is of sufficient quality, or that technical support is available. As a result, projects
have not been successful over time, and have therefore failed to gain acceptance. However,
the experience gained through these projects combined with successful dissemination of this
experience will  enable future  projects to avoid these barriers to successful implementation.

Initial costs can often pose a significant barrier, since the cash resources of small and medium
farmers in many regions is often limited.  As construction methods have been refined,, and
made more appropriate for local resources, construction costs have fallen significantly (e.g.,
the use of ferrocement fixed dome construction). However, financing arrangements may be
necessary to promote these systems.

An additional barrier may be government policies that act to reduce the perceived benefits of
livestock manure digesters. For example, fossil fuel energy and fertilizer import subsidies will
have the effect of reducing the replacement value of biogas and digester effluent.  Such
policies may need to be examined when implementing national policies, particularly in lesser
developed countries.

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LIVESTOCK MANURE                                                               7-19
Benefits

In addition to reducing methane emissions from livestock manure, basic anaerobic digesters
have the following benefits:

   •  Reduced fossil fuel use. Biogas is a renewable and convenient fuel that can replace
      conventional fossil fuels in many applications.  This replacement will result in reduced
      fuel costs and/or imports.

   •  Reduced demand for commercial fertilizers. By returning nutrients and minerals to the
      land,  the need  for expensive commercial fertilizers can be reduced,  saving scarce
      foreign exchange.

   •  Improved environmental and human health.   Anaerobic digestion effectively treats
      livestock manure, reducing the danger from human pathogens and manure runoff into
      surface and groundwater. Additionally, using effluent as fertilizer improves soil quality,
      reducing soil erosion (and improving agricultural productivity).

   •  Increased self sufficiency of farms.  By reducing expenditures and energy demands,
      increasing productivity, small and medium size farms can be made more self sufficient.

   •  Improved indoor air quality.  Using gas as a domestic fuel, in place of  relatively dirty
      fuels  such as coal or wood, can  greatly improve the quality of indoor air (Hamburg,
      1987).
                       Small Scale Digester Systems
                         methane reductions of up to 70 percent
                         appropriate technology
                         reduced energy costs
                         reduced fertilizer costs
                         technology currently available
                         minimum maintenance requirements
7.4   Larger Scale Digesters

Large and medium scale biogas digesters promote the anaerobic digestion of livestock manure
and collect the methane (biogas) that is produced.  The recovered biogas can be used to
power a variety of end uses which provide electricity, heat or cooling to the farm. In addition
to effectively treating livestock manure and providing a low-cost and clean energy source, this

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7 - 20
         LIVESTOCK MANURE
strategy can yield high quality fertilizer as a byproduct of the digestion process. The systems
described here are plug flow digesters  and complete  mix digesters  (see  Exhibit  7-12).
Because of the size, materials, and relative complexity of these technologies, they are most
appropriate for more industrialized regions.
Recovery Technology Descriptions

Because manure management systems vary among farms, the percent total solids (TS) of the
manure also differs  widely.  Correspondingly, the two technologies discussed here are
appropriate for a range of manure compositions. Complete mix digesters typically use manure
with 2-10 percent total solids; plug flow digesters use manure with 8-15 percent total solids.
Both systems range in size and are capable of handling the manure output of operations with
a few hundred to several thousand head or more, or roughly 0.5 million poultry.  Both designs
are compatible with existing management practices.
                                     Exhibit 7-12
                      Schematic Diagrams of Anaerobic Digesters
                   SLURRY .
                     IN
                                                           EFFLUENT
                                                             OUT
                 PLUG-FLOW DIGESTER
                  SLURRY
                     IN 	
EFFLUENT
  OUT
  Source: Koelsch et al., 1989.
    Plug Flow Digesters:  Plug flow digesters use manure that is undiluted, or has had only
    small quantities bf water added. This type of digester has been implemented successfully
    at many farms with scraper manure systems, or at farms that  use front-end loaders to
    remove manure. The basic digester design is a long trough, often built below ground level,
    with an air tight but expandable cover (see Exhibit 7-13).  The manure is collected daily

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LIVESTOCK MANURE
              7 -21
   and added at one end of the trough. Each day, a new "plug" of manure is added, slowly
   pushing the manure down the trough.  The size of the system is determined by the size
   of the daily "plug" and the retention time -- the total time that manure spends inside the
   digester as it flows from one end to the other, as indicated in the following equation:
     Working Digester Volume — Daily Waste Volume  X  Retention Time (in days)
   The overall dimensions of the digester are designed to allow a retention time of 20 to 30
   days at 30 to 35 "C; lower temperatures will slow the rate of digestion and necessitate
   a longer retention time.   (At a given temperature, longer retention times allow more
   complete digestion, but will increase construction costs.)  The depth of the trough is
   usually 2 to 5 meters (8 to 16 feet); the length and width are designed in a 5:1 ratio.  For
   example, a 25 feet wide trough would be 125 feet long (7.5 by 40 meters), with a total
   volume of 40,000 to 45,000 cubic feet (1100 to 1300 m3). With a retention time of 20
   days, this system could handle 2,100 ft3 (60 m3) of manure per day -- sufficient for
   several hundred cows.  The cover would have a maximum capacity of approximately
   30,000 cubic  feet (800 m3).  These calculations are based on a rectangular trough;
   however, the designs are often U- or V-shaped, which increases the structural strength
   but decreases total volume by  up  to 50 percent (Koelsch,  1989; Treleven, 1989).
                                    Exhibit 7-13
                                 Plug Flow Digester
           Bypass
          Manure Entrance

J Om LJA***
, Chamber

5

; Digester
> (
Gas Bag Collection
Cover
C-"V
Exit v
Control
Chamber f


f I
* r

                                                       Manure Exit
 Lagoon Storage
     for
Agricultural Fertilizer
   The air tight cover prevents gas leaks and helps maintain anaerobic conditions inside the
   trough.   As the manure moves through the digester it decomposes, producing  biogas
   which is trapped in the expandable cover. The gas is collected through a perforated pipe
   supported above the surface of the manure, and is transported to the end use (e.g., the
   engine generator).

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7 - 22                                                                LIVESTOCK MANURE
   There are several components  of the system in addition  to the digester vessel itself.
   These  include the manure delivery  system, mixing pit equipment (holding/pre-heating
   tank), a removal and collection system for the effluent, and other design features that
   improve the ease of operation and overall performance. Where possible, digester systems
   use a gravity-feed design. The pre-heating tank, the digester, and the collection system
   are built on a gentle slope to facilitate transfer and movement of the manure. Otherwise,
   pumps must  be installed  to move the manure from  one area to the next.

   •   Mixing Pit. Many systems use a mixing pit with a volume roughly equal to one day's
       manure output to store manure before it is added to the digester. This is a convenient
       method for easily adjusting  the  percent total solids of  the manure (by dilution with
       water), and for adding the  manure to the digester (Koelsch, 1989).  The tank is
       connected to the digester by a pipe (usually underground) that is below the surface
       level  of the manure,  which  effectively prevents air from flowing into the  digester.
       There must also be a  digester bypass route for maintenance  periods and undesirable
       batches of manure.

       Mixing pits facilitate pre-heating  the manure -  raising the temperature of the manure
       to promote decomposition  and  methanogenesis.  A  second  important method  of
       promoting methanogenesis is to warm the contents of the digester itself.  Maintaining
       a temperature of above 30 °C is crucial to achieve high rates of digestion. The energy
       for pre-heating and digester heating is often derived from waste heat from the cooling
       system of an internal combustion engine generator.  In both cases, hot  water pipes
       from  the  engine coolant system  run through the containers,  transferring heat to the
       manure.

   •   Effluent Collection. As the digested manure reaches the end  of the digester trough it
       must be removed and stored before use (e.g., as fertilizer).  In gravity-feed systems
       the material is simply displaced as new manure is added.   Removing  the manure
       without allowing air to enter the system is usually achieved  with a trap mechanism.
       Manure can be applied  directly,  or can be further processed (e.g., separated with a
       centrifuge into liquid  and solid components to ease handling).

       In order to protect the flexible cover, and to maintain optimal temperatures, some
       digesters are enclosed in simple structures. Also, the digester vessel can be built with
       an insulating layer to  retain heat, and the cover can also be insulated with fiberglass.

   Complete Mix Digesters:  Complete mix digesters typically handle manure with a lower
   percent total solids than  plug flow digesters  (i.e., dilute liquid/slurry), and in general they
   handle larger volumes of manure. The significant difference between the plug  flow and
   complete mix technologies is the design of the digester vessel, and thus the processing
   of the manure.  However,  the basic system components are  similar  (i.e., mixing pit,
   reactor (digester), removal  and  storage,  heating).

   As with plug flow digesters, the manure is collected in a mixing pit where the dilution can
   be adjusted and the manure can be pre-heated, and from here it is pumped (or flows) into
   the digester  vessel.   (Clarifiers can be  used if the manure is too dilute, or to reduce
   volume). The digester vessel is simply a large, vertical, poured concrete or steel container
   (similar to a liquid/slurry storage container). The vessels are typically circular, this design

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LIVESTOCK MANURE
                         7 - 23
   being the strongest and most economical (see Exhibit 7-14). Both the digester and holding
   tank are heated (with engine cooling system waste heat).

   When manure is  added to a  complete mix digester it is deliberately mixed within the
   digester vessel. This creates a homogeneous substrate, preventing stratification and the
   formation of a surface crust, and keeping solids in suspension.  However, it also means
   that manure  is not processed  sequentially (i.e., there  is not a fixed  retention time).
   Therefore, although the average retention time can be controlled, the actual retention time
   of a particular batch of solids will vary considerably; volatile solids may spend too short
   or too  long a period  of time  in the digester.  This potential inefficiency  is generally
   balanced  by  the improved digestion efficiency due to mixing,  heating,  and  other
   management techniques.  (This is in contrast to plug flow digesters, where the elongated
   design prevents mixing of manure; however, maintaining  a homogeneous substrate is not
   a problem with the more solid manure used in plug flow  designs.)

   Digester volumes range considerably, from around 100  m3 (3,500 ft3; 25,000 gal.) to
   several  thousand  m3 (e.g., 5000 m3; 180,000 ft3; 1.3  M gal.)  Improved efficiency of
   digestion, due to heating and mixing, often result in an average retention time from 10 to
   20 days. Thus, these capacities represent daily capacities of approximately 1,500 gallons
   to 100,000 gallons per digester (210 to  14,000ft3) (Waybright, 1991). Larger volumes
   are usually handled in multiple digester systems.  (These figures indicate the  flexibility of
   digesters; they do not represent definite size limits.)  For  example, flush  systems at dairy
   operations produce upwards of 20 to 30 gal/day/cow.
                                     Exhibit 7-14
                                Complete Mix Digester
                            Bypass
          Racirculasng
          Pump
  Lagoon Storage
tor Agricultural Fertlizst
   A fixed expandable cover maintains anaerobic conditions and traps the methane that is
   produced.  The methane is removed from the digester with a suction blower, processed.

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7 - 24                                                               LIVESTOCK MANURE
   and transported to the end-use site.  Adequate space must be maintained between the
   surface of the manure and the cover for gas to collect.

   In this process, manure pumped from the holding tank displaces a portion of the contents
   of the digester vessel. The displaced material can be further treated for use as a fertilizer,
   or used directly.  Alternatively, in some systems it is pumped into the next of a series of
   digesters, thereby increasing the extent of anaerobic decomposition and the quantity of
   methane produced.

   Utilization Options:  The utilization options for the recovered biogas have been described
   above in "Covered Lagoons." The options include  electricity generation with gas fired
   engine generator; gas fired boilers and space heaters; and chilling equipment. A well
   maintained digester will produce as much as 0.25 to 0.6 m3 of biogas (50 to 65% CH4)
   per kg of VS, operating at 30 to 35 °C,  and more at higher  temperatures  (Safley &
   Westerman, 1988).

As  a rough approximation, anaerobic digesters  will  reduce the  potential  for  methane
production by two thirds or more, leaving the remaining  one third of the compounds that can
decompose anaerobically in the effluent. If the effluent is handled under anaerobic conditions,
such as in a treatment lagoon or tank, then methane may be generated from the effluent.
Therefore, where livestock manure is currently managed anaerobically and generates methane,
efficient  digesters with gas recovery systems may reduce methane emissions by up  to 70
percent,  with larger reductions achievable at longer retention times.

Choosing between the available options  involves an assessment of  the size  and type of
current manure management practices (i.e., volume and %TS), the technical and economic
resources available, and the demand for energy and fertilizer products.
Costs

The initial capital costs and subsequent  operating costs of  anaerobic digesters  will vary
considerably with size, and also with the particular design of the various system components.
Using conservative assumptions (e.g., only considering revenue from energy sales or cost
savings from use, and not from other products of digestion), one study for the U.S. estimated
that installed costs for  economically viable projects may range as high as $3,000/kW; this
assumes that the payback period will be 5 years or less  (Quok & Chandler, 1984).  These
results are summarized in Exhibit 7-15.

These figures provide a valuable first estimate for project costs. However, actual installed
costs and overall economic viability will vary with site specific factors.  For example, specific
projects include:

    •   A 400 head dairy farm  which installed a $124,000  plug flow digester (to handle
       manure from an existing scraper system). The digester  had a total volume of 150,000
       gallons.  Operating costs were $2,000/yr.  The 45 kW generator saves $22,000/yr in
       electricity costs. Additional savings from waste heat and fertilizer use are estimated
       to be $10,000/yr (Ferchak,  1988).

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LIVESTOCK MANURE
7 - 25
      A 500 head dairy installed a $200,000 plug flow system, with a maximum generating
      capacity of 85 kW. The average output of 40 kW creates savings of approximately
      $4,000/month in electricity and heating fuel (Treleven, 1989).

      A 2,700 head dairy farm installed 3 complete  mix digesters, with a daily capacity of
      30,000 gallons, at a cost of $250,000 (in 1991 dollars). Estimated net annual income
      has been $90,000. In 1990, over 1 million kWh  of electricity was produced for on-
      farm use and sale to a local utility company (Waybright, 1991).
Availability

Considerable experience exists in the planning, de~ ^n, and operation of biogas digesters.
Anaerobic digesters are a viable technology that can  .^iprove existing  manure treatment
practices while providing energy and other valuable by-prouucts.
Exhibit 7-1 5
Estimates of Economically Feasible Projects
•cw\n
13UUU
1 10000-
I
5000—
COST OF BIOGAS SYSTEMS
FOR SCRAPE AND FLUSH SYSTEMS
CURRENTLY AVAILABLE SYSTEMS
i
\ .ŤŤ••Ť. Complete mix, flush system
ť 	 Complete mix, scrape system
\\ — — — Plug flow, scrape system
V
V XX
\ N **—^
\S:"-"~-::: — ..._
Economically Feasible
1 1 1 1 1 1 1 1 1 1 1 1 1 1
20 40 60 80 100 120 140
Capacity (Kilowatts)

Source: Quok and Chandler, 1 984
Applicability

The technologies described in this assessment are applicable for a wide variety of manure
management systems.  However, it is important to  identify the most appropriate digester

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7 - 26
LIVESTOCK MANURE
design for  existing  management  practices, available resources, and to ensure economic
viability.

Plug flow digesters do not mix the manure as it is being decomposed, and therefore are more
suited to homogeneous manure (e.g., from dairy and beef operations).  Furthermore, the
manure must be relatively concentrated. Complete mix digesters, on the other hand, are also
capable of operating with more dilute and  less homogeneous manure.  These considerations
are summarized in Exhibit 7-16.

A second factor is the availability of labor and technical support to  maintain the digester.
Anaerobic digesters usually require minimal maintenance.  However, it is important that the
time, personnel, and expertise are available when operating problems occur. This is especially
true of complete mix digesters, which are typically larger and contain more  mechanical
components (Koelsch, 1989).
Exhibit 7-16
Digester Design/Manure System Compatibility


Plug Flow
Complete
Mix
Scrape System
Dairy
X
X
Beef
X
X
Layer
(X)1
X
Swine
(X)2
X
Flush System (dilute)
Dairy

X
Beef

X
Layer

X
Swine

X
1 Poultry manure must be very dilute because of high ammonia levels Source: Quok and Chandler, 1984.
2 Less common; pig farms typically use flush systems.
In addition to these technical and  operational considerations,  it is  important to analyze
potential economic scenarios. Revenues flow primarily from energy sales (or the savings that
result from reducing the amount of energy purchased by the farm). Therefore, the potential
gas volume and local energy rates must be favorable. As with covered lagoons, larger farms
are more likely to produce significant quantities of biogas. Revenue can also be obtained from
fertilizer sales (or improved fertilizer quality). Installing an anaerobic digester can also reduce
pollution, odor, and other less quantifiable problems.

Currently, the type and size of manure systems that are compatible with these designs, and
the material,  economic, and  technical resources necessary to build and operate them, make
this strategy  applicable to relatively industrialized countries, or large, highly-managed farms.

Barriers

As with  any  change in farm operations,  anaerobic digesters must gain the acceptance of
animal farmers by demonstrating  compatibility, economic viability, and technical reliability.

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LIVESTOCK MANURE                                                    ,           7-27
In the past, many expensive and unreliable demonstration projects have hindered acceptance.
Technical reliability is  a  particularly important factor because of the  relatively complex
technologies (compared to covered lagoons and small scale digesters). Digester systems can
require  high  initial  costs.   Farmers  may  lack sufficient capital  to  undertake projects
independently.
Benefits

In addition to reducing methane emissions from livestock manure, anaerobic digesters can
result in the following benefits:

   •   Effective  treatment  of livestock  manure.  The treatment  of manure in anaerobic
       digesters  reduces runoff problems, and reduces pathogen levels.  Improved treatment
       may better comply with applicable regulations.

   •   High quality fertilizer production. Anaerobic treatment of manure produces a fertilizer
       with a high ammonia content.

   •   Improved  energy use. Biogas is a cleaner burning fuel than most of the fossil fuels it
       replaces.   This reduces the emissions of particulates, nitrogen  oxides, and sulfur
       oxides. Furthermore, biogas is a renewable and a less carbon intensive than coal or
       oil, reducing net carbon dioxide (a greenhouse gas) emissions into the atmosphere.

   •   Improved  aesthetic  quality.   Processing  manure  in (anaerobic)  sealed containers
       improves  control over dust,  flies, and odors.  Furthermore, manure effluent from
       digesters  will have less odor than untreated manure.
                       Larger Scale Digesters

                       ť  methane reductions of up to 70 percent
                       Ť  medium quality gas (60-80% CH4)
                       •  moderate capital investment
                       •  reduced energy costs
                       •  technology currently available
                       •  compatible  with  a range  of  waste
                          management systems
                       •  clean energy source
                       ť  regulatory compliance

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7 - 28                                                             LIVESTOCK MANURE
7.5  References
Contributions were made by:

   Andrew G. Hashimoto, Head, Department of  Bioresource Engineering,  Oregon State
   University, USA

   Mark Moser, President, RCM Digesters, USA

   Kurt F. Roos, USEPA, USA

   L.M. Safley, Department of Biological and Agricultural Engineering, North  Carolina State
   University, USA

   John M. Sweeten, Associate Department Head, Texas A&M University, USA

   Jonathan Woodbury, ICF,  USA


Additional information may be found in the following:

Anderson, C., Waste Management of North America, personal communication, 10/91.

Chandler, J.A.,  S.J. Hermes, and K.D.  Smith (1983), A Low Cost 75 KW Lagoon Biogas
System, presented at "Energy from Biomass and Wastes VII," Lake Buena  Vista, Florida,
January 25,  1983.

Chen Y.R. and A.G. Hashimoto (1987), "Kinetics of Methane Fermentation," in Biotechnology
and Bioengineering Symposium No.8, pp.269-282.

Edgar, T.G. and A.G. Hashimoto (1991). Feasibility Study for a Tillamook County Dairy Waste
Treatment and Methane Generation Facility. Department of Bioresource Engineering, Oregon
State University.

Ferchak, J. (1988), "Biogas Installation at the Oregon Dairy Farm," University of Pennsylvania,
Energy Management and Policy, PA, June/July 1988.

Hamburg, R.A. (1987), "Household Biomass, Biogas and Coal Combustion in Henan Province,
People's Republic of China: A Preliminary View of the Resultant Indoor Air Pollution," prepared
by Omega-Alpha Recycling  Systems, Orma, West Virginia.

Gunnerson C.G. and D.C. Stuckey (1986), Anaerobic Digestion: Principles and Practices for
Biogas Systems, World Bank, Washington, D.C.

IPCC (Intergovernmental Panel on Climate Change) (1990), Greenhouse Gas Emissions from
Agricultural  Systems,  U.S.  Environmental  Protection   Agency,  Washington,  D.C.,
EPA/20P/2005.

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LIVESTOCK MANURE                                                              7 - 29
IPCC (1990), Methane Emissions and Opportunities for Control:  Workshop Results of the
Intergovernmental  Panel  on  Climate  Change,  U.S.  Environmental  Protection  Agency,
Washington, D.C.,  EPA/400/9-90/007.

Koelsch, R.K., E.E. Fabian, R.W. Guest, J.K. Campbell (1989), "Anaerobic Digesters for Dairy
Farms," in Agricultural and Biological Engineering, Department of Agricultural and Biological
Engineering, New York State  College of Agriculture and Life Sciences, Ithaca, New York,
Extension Bulletin 458.

Loehr, R.C., Pollution Control for Agriculture, Academic Press, 1984.

Maramba, F.D., A. Judan, E. Obias, "Fuel,  Feed, and  Fertilizer from  Farm Wastes - The
Philippine Experience," in Third International Symposium on Anaerobic Digestion. Boston,
1983.

Moser, Mark, and  Kurt Roos, (draft in preparation), Opportunities for Profitably Reducing
Methane  Emissions from Livestock Waste:   A Texas  Dairy Industry Case  Study.  U.S.
Environmental Protection Agency, Washington, D.C.

Pimental D. (1975), "World Food, Energy, Man and Environment," in Energy, Agriculture and
Waste  Management, ed.  Jewell, W.J., Ann Arbor Science Publishers, Inc., Ann Arbor,
Michigan.

Quok, L. and J.A.  Chandler (1984), Potential of Biogas Systems for California Farms with
Confined Animals,  presented at "Energy from Biomass and Wastes VIII," Lake Buena Vista,
Florida, January 31, 1984.

Roos, K.F. (1988), Issues in Anaerobic Digestion: Economics. Technology, and Transfer, M.S.
Thesis in  Energy Management and Policy, University of Pennsylvania, Pennsylvania.

Roos, K.F.  (1992), "Profitable Alternatives for Regulatory Impacts  on Livestock Waste
Management,"  in  National  Livestock. Poultry,  and Aguacuiture  Waste Management.
proceedings of the American Society of Agricultural Engineers national workshop, 29-31 July
1991.

Safley, L.M., P.W. Westerman (1990), "Psychrophilic Anaerobic Digestion of Dairy Cattle
Manure," in Agriculture and Food  Processing Waste. ASAE 1990.

Safley, L.M. & P.W. Westerman (1988), "Biogas Production from Anaerobic Lagoons,"  in
Biological Wastes,  No.23, pp.181-193, 1988.

Treleven, Mike (1989), "Black Gold," in California Farmer, June 3, 1989.

UN (United  Nations), Updated United Nations Guidebook on Biogas Development. New York,
1984.

UNEP (United Nations Environmental Program), Biogas Fertilizer System. Nairobi, 1984.

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7 - 30                                                             LIVESTOCK MANURE
US DOE (U.S. Department of Energy) (1988), Handbook of Bioqas Utilization, 1988.

USEPA (United States Environmental Protection Agency) (1992), Global Methane Emissions
from Livestock and Poultry Manure. GCD/OAR, U.S. Environmental  Protection  Agency,
Washington, D.C., EPA/400/1-91/048.

Waybright, Richard C. (1991), On-Farm Utilization of Animal Wastes, Philadelphia Society for
Promoting Agriculture, April 4, 1991.

World  Health  Organization (WHO)  (1980),  A  Challenge to Developing Countries:  The
International Drinkinq-Water Supply and Sanitation Decade. 1981-1990. WHO  Chronicle
no.34, pp. 327-331, 1980.

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CHAPTER EIGHT
WASTEWATER  MANAGEMENT
8.1   Background

Methane Production and Emissions

Wastewater and its residual solids byproduct (sludge) have the potential to produce globally
significant methane emissions. Wastewater, often referred to as sewage, includes residential,
commercial and industrial liquid and water-carried wastes. Methane emissions result if the
wastewater and sludge are stored or treated under anaerobic conditions (in the absence of
oxygen), and if the gases produced are allowed to reach the atmosphere. Although data are
very limited, global emissions from this source are estimated to be 20 to 25 teragrams per
year (USEPA,  1990).

Highly organic waste streams, such as domestic wastes and effluent (discharge) from food
processing facilities, likely contribute most of the methane from this source.  These waste
streams are characterized  by high biochemical oxygen demand (BOD) and quickly deplete
available oxygen as their organic matter decomposes. Untreated domestic waste  streams,
for example, typically range from 100 to 400 milligrams of BOD per liter.  Food processing
plants, which  include fruit and sugar processing plants, meat packing plants, creameries, and
breweries, can produce untreated wastewater with BOD as high as 100,000 milligrams per
liter.

Wastewater in most developed countries usually undergoes treatment to reduce or eliminate
harmful constituents in  facilities run  by municipalities or by industrial production plants.
Although there are some  methane  emissions from this source, wastewater in developed
countries is not considered a major source  of emissions. This is because treatment often
takes place under aerobic conditions and, when anaerobic processes are used (e.g., in some
wastewater treatment and  most sludge treatment facilities),  the generated methane is
collected  and  utilized  or burned  off.  Wastewater treatment systems and their  methane
production potential are  described in more detail in Exhibit 8-1.

The largest potential for  methane emissions  from wastewater exists in developing countries,
where waste streams are often unmanaged or maintained under anaerobic conditions without
control of the  methane.  For example, less than 40 percent of municipal wastewater in most
developing countries is collected in sewage systems, and only  a fraction of this collected
waste undergoes treatment (Bartone, 1992). The untreated waste is often flushed along with
its sludge into waste lagoons, rivers or the ocean, or is buried.  Releasing the waste into rivers
can cause anoxic conditions with potential for methane emissions, while also creating health
risks associated with the spread of pathogens, heavy metals, and toxic compounds.
Methane Emission Reduction Strategies

A number of strategies exist for reducing methane emissions from wastewater and sludge.
Wastewater management techniques  can  greatly  reduce the production of methane, or
alternately,  generated methane can be  captured and used as a fuel or flared. Such

-------
8-2
WASTEWATER MANAGEMENT
Exhibit 8-1
Wastewater Treatment Systems and Methane Production

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-------
WASTEWATER MANAGEMENT                                                         8 - 3
                                 Exhibit 8-1 (cont.)
               Wastewater Treatment Systems and Methane Production

   The extent to which wastewater is treated depends on its degree of contamination and
   the requirements placed on its intended destination (e.g. discharge to surface or ground-
   water, use in industrial processes, irrigation), and on available infrastructure, technology
   and funding.

   In most developed countries and other  regions where  the technology  is available,
   industrial waste streams which are to be discharged into  municipal treatment systems
   often undergo bacterial pretreatment or chemical disinfection to reduce contaminants
   to acceptable levels.  After  pretreatment, if it is necessary, the possible levels  of
   wastewater treatment consist of: primary treatment, which refers to the removal  of
   suspended solids by sedimentation or flotation; secondary treatment, usually involving
   aerobic biological stabilization; and advanced mechanical or chemical treatment. Natural
   systems such as land  treatment are also used in providing secondary and advanced
   treatment.

   Each stage of wastewater treatment results in the production of sludge, a byproduct
   which generally contains high concentrations of organic matter and thus has potential
   to produce significant methane emissions.  After sludge is thickened by gravity  or
   mechanical means to concentrations of 5-10 percent solids, one or a combination of the
   following types of treatment is used  to prevent  its putrescence and/or reduce its
   volume; land treatment; aerobic or anaerobic digestion; chemical treatment; and
   incineration.  Stabilized sludge can be safely reused or  disposed  of by  composting,
   incineration or landfilling. The ash, compost, and slag endproducts are suitable for use
   as organic fertilizers and soil amendments in agriculture, forestry and land reclamation,
   and sometimes in the production of construction materials.

                                 Sources: Escritt, 1984; Hammer, 1986; and Loehr, 1984
technologies and practices are common in many developed countries, and can be adapted for
use in other regions where wastewater and sludge may currently produce significant methane
emissions.   Application of these  strategies  would also greatly  improve human  health
conditions and other environmental problems.  These practices include:
   Prevention of methane production during wastewater treatment:
       • Aerobic Primary Wastewater Treatment;
       • Aerobic Secondary Wastewater Treatment;
       • Land Treatment;

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8 - 4                                                          WASTEWATER MANAGEMENT
   Recovery and utilization/flaring of methane from anaerobic digestion of wastewater or
   sludge:
       • Utilization;
       • Flaring;

   Minimization of methane emissions during sludge treatment and disposal:
       • Aerobic Digestion;
       • Land Application;
       • Chemical Stabilization;
       • Incineration;
       • Landfilling with Methane Recovery;
       • Aerobic Composting; and
       • Experimental Uses for Sludge.

Assessments include descriptions of the following:

   • Reduction/Utilization Technologies;
   • Costs;
   • Availability;
   • Applicability;
   • Barriers; and
   • Benefits.

In general,  the implementation of these strategies will  be as a result of a country's goals to
reduce the  quantities of unmanaged wastes and to reduce related risks to human health and
the local environment.  In many cases, these strategies represent large  capital investments
which are justifiable only to the extent that these local  benefits are achieved.  Therefore, the
available strategies are generally described here as options which will increasingly be used in
developing  regions of the world, and not as options that can be promoted based on their sole
ability to limit methane emissions. The strategies are described in the technical assessments
which follow, and are summarized in Exhibit 3-2.

-------
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-------
8 - 6                                                         WASTEWATER MANAGEMENT
8.2  Prevention of Methane Production During Wastewater Treatment

One  method of reducing wastewater-related methane emissions is  to  prevent methane
production by maintaining the wastes under aerobic conditions (generally 0.2 to 0.6 mg or
greater levels of oxygen per liter of wastewater) (Loehr, 1984). The maintenance of aerobic
conditions ensures the complete metabolization of the organic matter in the wastewater either
by aerobic bacteria or by facultative organisms which can be aerobic or anaerobic depending
on the level of available oxygen.  Managing wastewater aerobically also prevents the release
of odorous gases  (e.g. hydrogen  sulfide, mercaptans,  disulfides),  which accompanies
anaerobic decomposition.   Aerobic conditions can be  maintained  through a variety of
wastewater management techniques during both primary and secondary treatment.

   Aerobic Primary Wastewater Treatment:  This strategy involves  maintaining sufficient
   oxygen levels during the primary phase of wastewater treatment. The level of oxygen can
   be sustained by using  proper organic loading techniques (controlling  waste levels and
   organic concentrations) or by providing oxygen to the wastes through mechanical aeration.

   Aerobic Secondary Wastewater Treatment: A variety of aerobic secondary wastewater
   treatment strategies exist which  can be used after primary treatment, including activated
   sludge processes, trickling filters, and rotating biological contactors (RBCs). In each case,
   stabilization is accomplished through the prolonged exposure of wastewater to aero Die
   microorganisms which are either floating (due to mechanical aeration) or attached to fixed
   or rotating media.

   Land Treatment:  Applying raw or partially stabilized wastewater to soil  is another method
   of breaking down the organic constituents in the wastewater while preventing methane
   production.  During land  application, wastewater is either added to the  soil surface or
   mixed with the upper layer of soil, which acts as a natural filter for the wastes.  This
   treatment method  is not  appropriate for wastes containing heavy metals, which pose
   health risks.
8.2.1 AEROBIC PRIMARY TREATMENT

Primary treatment refers  to  the  sedimentation  and separation  of  large  particles from
wastewater, along with partial decomposition of the  organic matter.  These processes can
occur naturally or as a result of human effort  wherever raw wastewater is collected.
Wastewater ponds can be aerobic, anaerobic,  or facultative (anaerobic only in the lower
layers), depending on their depths, loading rates, and  levels of sludge build-up.  A variety of
health and environmental objectives can be met by maintaining sufficient oxygen  to minimize
methane production.

Primary wastewater treatment can occur aerobically in aerobic oxidation ponds and primary
treatment ponds (i.e., first pond in a  multiple pond system) if sufficient oxygen levels eire
sustained in the waste stream. The term  "oxidation ponds" generally describes those ponds
in which raw wastewater undergoes primary treatment without the aid of mechanical aeration,
and  often receives no further treatment; this  is frequently the case in countries where
wastewater is not intensively managed.  Primary treatment ponds are used in the first of

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WASTEWATER MANAGEMENT                                                         8 - 7
several treatment phases which wastewater receives in municipal or industrial treatment
plants. These ponds in many areas become anaerobic due to overloading, and little effort is
made to control the methane which is produced (Maber, pers. comm.). This section describes
management methods that can  help to maintain aerobic or facultative conditions in ponds
which may otherwise be at least partly anaerobic.
Reduction Technology Description

Primary wastewater treatment ponds can be maintained under aerobic conditions if loaded
with the proper types and volumes of wastes, or if oxygen is provided to the wastes through
aeration practices.

   Proper loading: this strategy is possible in all primary treatment ponds and is especially
   suitable for oxidation  ponds.  Proper loading involves limiting the depths and the BOD
   loading rates  of the  ponds and  allowing adequate detention times for the wastes.
   Constructing additional ponds and promptly removing sludge  may also be necessary for
   maintaining proper waste loads.  These techniques can be used for both aerobic and
   facultative ponds.

   Aerobic ponds, also called high-rate aerobic ponds, maintain dissolved oxygen throughout
   their entire depth. They are usually 30 to 45 cm deep, allowing light to penetrate the full
   depth.  Oxygen is provided by surface aeration and photosynthesis (mixing helps to
   expose all algae to sunlight), and aerobic bacteria stabilize the waste.  High-rate  aerobic
   ponds are most successful when allowed a 3 to 5  day waste detention time, and  may
   require paving the bottom to prevent weed growth. They can achieve a high degree of
   BOD removal in areas where land is limited, but are only feasible in warm, sunny climates.

   Facultative ponds operate anaerobically in the lower depths and aerobically in the upper
   layers, with oxygen provided by photosynthetic algae and surface reaeration. These types
   of ponds are more common and easier to operate and maintain than aerobic ponds, and
   are often used to treat raw municipal wastewater, and primary and secondary effluent.
   Facultative ponds can operate with negligible methane emissions if their depths do not
   exceed 2 meters and if the bottom layers are  maintained at relatively cool temperatures.
   Under these conditions, the amount of methane generated should be small enough to be
   naturally absorbed or oxidized as it  moves toward the  surface through aerobic levels.
   Facultative ponds can require large areas of land and detention times of up to 30  days to
   stabilize wastes (Loehr, 1984; USEPA,  1983).

   Aeration: This strategy involves aerating primary wastewater treatment ponds to ensure
   continuous oxygen transfer and encourage the growth and  activity of the  aerobic
   microorganisms that decompose waste. This can be accomplished by pushing air into the
   wastewater with rapidly-moving mechanical impellers or injecting air or pure oxygen below
   the surface and using mixers to entrain the air in the wastewater.  Aerated ponds are
   significantly more efficient than non-aerated oxidation ponds, requiring an average of only
   1 to 10 days retention time (Loehr, 1984).

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8 - 8                                                         WASTEWATER MANAGEMENT
Costs

In areas where wastewater is currently unmanaged, there  will  be start-up costs for the
construction and maintenance of diversion, collection and treatment facilities; the magnitude
of these costs will depend on the level of technology required for each treatment option.

   Proper loading: Oxidation ponds are the least costly wastewater treatment option, because
   operating costs are extremely low.

   Aeration: The equipment needed for this strategy and the energy required to operate the
   aerators can be costly.  Depending on the volume of wastewater flow into the pond, well-
   constructed aerated oxidation ponds are estimated to cost from $150,000 to $3 million
   for construction, assuming a range  of 0.05 to 10 million gallons of wastewater flow per
   day (Mgal/d). Annual operation and maintenance costs are estimated to range from
   $20,000 to  $500,000, based on the  same volume assumptions  (USEPA,  1950).
   However, these costs may be offset to some extent by the improved  performance and
   capacity of aerated primary ponds;  one aerated pond may stabilize as much wastewater
   as several non-aerated oxidation ponds.
Availability

Primary treatment ponds and aeration technologies are available in most countries. Building
facilities in areas without  existing wastewater management infrastructures, and properly
maintaining them in all countries, may necessitate some management training.
Applicability

The applicability of each aerobic primary treatment method depends on the amount of waste
to be treated and its concentration of organic matter. Wastes with fairly low organic content
or waste streams that have been diluted with storm water are suitable for treatment in aerobic
or facultative ponds; large volumes of waste and highly organic wastes, such as effluent from
food processing plants or strong domestic sewage, generally require aeration to ensure a
sufficient oxygen supply.

Several other factors limit the applicability of this technique.  Aerobic  ponds are not suitable
where cold climates discourage bacterial activity. Both aerobic and facultative ponds, which
can produce odors, may not be acceptable in densely-populated areas. Finally, wastewater
which receives primary treatment in aerobic and facultative ponds is only partially stabilized
and not suitable for all uses. For example, effluent from aerobic ponds may contain high
coliform levels, effluent from facultative ponds can contain significant  amounts of algae, and
both types of ponds can produce effluent with high levels of suspended  solids (USEPA, 1983).
Barriers

The additional labor required for the proper construction and maintenance of primary treatment
ponds may create a barrier in areas where wastes are currently unmanaged.

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WASTEWATER MANAGEMENT                                                         8 - 9
   Proper loading: Due to the amount of wastes  which pass through primary ponds in
   treatment plants, relying on proper loading techniques to maintain aerobic conditions in
   these ponds may not be  feasible.  This is especially true because the constant sludge
   removal  which  is necessary for maintaining  aerobic  conditions interferes with the
   thickening of the sludge required for further processing.  In such cases, aeration may be
   more suitable.

   Aeration: The initial equipment costs and the operating costs can pose barriers to the use
   of aeration in wastewater management.
Benefits

In addition to preventing the production and  emission of methane from wastewater, the
containment and control of wastewater by the means described above can result in several
other benefits:

   •  The containment and control of wastewater by these means reduces health risks such
      as the spread of diseases often carried in wastewater. Common waterborne diseases
      include viruses (hepatitis), protozoa  (giardiasis), and bacteria (cholera).

   •  These methods can also prevent concentrations of phosphorous and/or nitrogen from
      increasing in lakes and rivers.  These nutrients can be carried by waste streams into
      receiving waters in large amounts, and can cause eutrophication, or deterioration in
      water quality.

   •  The maintenance of aerobic conditions  in primary  ponds can reduce or eliminate the
      odors which result from anaerobic processes. In the case of aerated ponds, odors can
      be  reduced to an even  greater  extent by covering the  ponds and  funneling  any
      generated gases back into their aeration systems (Lagnese,  1992).

   •  Aerating primary ponds enhances their efficiency: the BOD in aerated ponds is reduced
      by  50 to 90 percent compared  to about 35 percent in non-aerated  ponds  (Loehr,
      1984). Because the efficiency of the pond is improved, larger volumes of wastewater
      can be stabilized each day.
                       Aerobic Primary Treatment

                       •  technologies widely available
                       •  low-cost strategies
                       •  reduced health risks and odors
                       •  methane reductions of up to 100% if
                          aerobic conditions are maintained

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8- 10
WASTEWATER MANAGEMENT
8.2.2 AEROBIC SECONDARY WASTEWATER TREATMENT

Wastewater treatment in some regions consists only of primary treatment, after which most
waste streams still contain high concentrations of organic matter and nutrients.  Improper
management of these partially stabilized waste streams can create large methane emissions
as well as other environmental problems and health hazards. Further stabilization is possible,
however, through secondary  wastewater  treatment, which usually  consists of  a closely
managed aerobic biological procedure resulting in the removal of up to 95 percent of the
organic matter in the waste (Loehr, 1984).
Reduction Technology Description

Three common methods of aerobic secondary wastewater treatment  are activated sludge
wastewater treatment, trickling filters, and rotating biological contactors (Exhibits 8-3 through
8-5).  These strategies are discussed  below.

   Activated sludge wastewater treatment: This is a suspended growth process, utilizing
   aerators (bubble diffusers or impellers) to suspend aerobic microorganisms in liquid wastes
   and supply them with oxygen until the organic matter is metabolized and stabilized.  The
   sludge is  then separated  in sedimentation tanks, and  part of the sludge that  is still
   biologically active is returned to the aeration tank to treat incoming water. The remainder
   of the sludge is  washed for sludge treatment and disposal.  This stabilization process
   requires relatively little space, and  the waste detention times range from several hours to
   several days.
                                     Exhibit 8-3
             Conventional Activated Sludge Wastewater Treatment Process
                                                        Scum scraper
       Influent
                                                                       Effluent
                                                        Clarifier
                                   Recycle sludge

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WASTEWATER MANAGEMENT
8- 11
   Trickling filters: This method is similar to the activated sludge technique, except that the
   microorganisms working to stabilize the organic material are attached to a fixed bed.
   Rotary nozzles apply the wastewater to the surface of the beds, and the organic matter
   in the liquid is stabilized as it trickles down over beds filled with stone or plastic media.
   Microorganisms attached to the media stabilize the  wastewater.  Trickling filters are
   generally preceded  by primary  treatment  to reduce  suspended  solids,  as  high
   concentrations of solids can result in clogging or reduced  equipment efficiency.  Most
   trickling  filters can be operated by hydraulic head and require no electrical energy.
                                      Exhibit 8-4
                     Trickling Filters Wastewater Treatment Process
                Incoming
                Effluent
                                                Distributor

                                                       Sprinklers
                      Slope 1°/a
                          Effluent
                         collecting
                          trough
                              Effluent discharge
                                                 1 1/2" to 2 1/2" Stones
    Rotating Biological Contactors (RBCs): This process operates under the same principle as
    the other secondary treatment processes. Large diameter plastic disks are rotated slowly
    (2 to 5 rotations per minute) in a wastewater tank; as the wastewater trickles over the
    surface, the attached microorganisms metabolize the organic matter in the liquid.  RBCs
    have relatively  low power costs because  the  energy required  to  rotate the disks  is
    minimized  by the buoyancy of the disks.

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8- 12
WASTEWATER MANAGEMENT
                                   Exhibit 8-5
             Rotating Biological Contactors Wastewater Treatment Process
                            Rotation
                                           Radial passages
                                                        Air cups
Costs

The costs of these types of secondary wastewater treatment can be moderately high because
of the equipment and energy requirements, and depend to a great extent on the daily volume
of wastewater flowing into the facility. Activated sludge wastewater treatment systems are
estimated to cost from $70,000 to $10 million for construction, assuming a flow of 0.1 to
80 Mgal/d.  Annual operation and maintenance costs are estimated to range from $4,000 to
$600,000,  assuming 0.1 to 100 Mgal/d (USEPA, 1980).

High rate trickling filters are estimated to cost from $250,000 to $ 10 million for construction,
and from $3000 to $45,000 per year for operation and maintenance, assuming flows of 1 to
100 Mgal/d.  Costs for trickling filters with plastic media  are estimated to be in the same
range, but with assumed flows of 0.1 to 100 Mgal/day (USEPA, 1980).  These costs may be
lower when trickling filters are operated by hydraulic head, as these systems have no energy
demand.

RBCs are estimated to cost from $100,000 to $5.5 million for construction, assuming a flow
of 0.15 to 100 Mgal/d. Annual operation and maintenance costs are estimated to range from
$9,000 to  $100,000, assuming 0.1 to 100 Mgal/d  (USEPA,  1980).

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WASTEWATER MANAGEMENT                                                       8-13
Availability

Aerobic secondary wastewater treatment technologies are common in Europe, the U.S., and
Japan, but may not be widely available in other regions.  Technology transfer and funding
programs may be necessary to stimulate the adoption of these techniques worldwide.

Applicability

Secondary wastewater treatment is applicable for most wastes, and is considered in many
countries to be the minimum treatment level necessary for any waste stream destined for
release into receiving waters or for eventual human use (e.g. irrigation, groundwater). Each
of the strategies described above  applies to different types of waste loads:  the activated
sludge process is suitable for large amounts of highly organic wastes; trickling filters are
better suited for smaller volumes of waste or wastes with moderate organic concentrations;
and the RBC can be used to treat almost any waste stream.
Barriers

The high energy requirements of many types of suspended growth secondary wastewater
treatment, especially the activated sludge process, may pose a significant barrier to the spread
of this treatment method.
Benefits

In addition to preventing methane production, aerobic secondary wastewater treatment has
several other possible benefits:

   •  These secondary treatment processes remove 75 to 95 percent of the organic matter
      which remains in wastewater after primary treatment (Loehr,  1984).

   •  The stabilization  of wastewater through  aerobic secondary treatment reduces the
      health risks associated with the improper management and disposal of  insufficiently-
      treated wastewater.
                       Aerobic Secondary Treatment

                       • moderate capital investment
                       • technology available in many regions
                       • health benefits
                       • prevention of odors
                       ť methane emissions can be eliminated if
                         aerobic conditions are maintained

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8-14                                                        WASTEWATER MANAGEMENT
8.2.3 LAND TREATMENT

An  alternative method  of stabilizing wastevvater while preventing methane  production is
applying the wastewater to soil, which acts as a "living filter" for the wastes (Loehr, 1984).
Reduction Technology Description

Wastewater can be land treated by applying it to the soil surface or mixing it with the upper
layer of soil, which results in the biological degradation of the organic constituents ol the
waste and the eventual immobilization of the inorganics.  Properly-managed land treatment
operations produce no methane, as aerobic conditions are necessary for optimal performance.
Aerobic conditions can be maintained  by allowing  sufficient time between wastewater
applications and through proper loading  of organic matter.

Depending on the concentration of pollutants in the water and the stabilizing ability of the soil,
wastewater may require  preliminary treatment  before land application.  The rate of
wastewater application will also be determined by the characteristics of the wastes and the
land application site.  A slow rate of wastewater application to vegetated soil surfaces such
as cropland or forests results  in the most successful  removal of  pollutants.  Other land
treatment strategies  involve  applying wastewater to highly  permeable soils, whereby the
wastewater is filtered and recharges groundwater (rapid infiltration systems), or to relatively
impermeable soils (overland flow systems). This last technique involves applying wastewater
to gently sloped, vegetated sites where it is stabilized as it filters through the surface soil and
plant litter, and is retrieved in collection ditches for surface recharge (Loehr, 1984).
Costs

Land treatment is generally a low-cost option, compared to other treatment options, as it
requires limited equipment and energy use.  Final costs can be highly variable,  however,
depending  on the volume of wastewater flow  and  on  external factors such  as the
transportation distance to the treatment site and the cost of purchasing or renting the land
used for treatment.

Slow rate land treatment is estimated to have from $100,000 to $30 million capital costs,
assuming  a flow of  0.1 to 100  Mgal/d.  Annual operation and  maintenance  costs are
estimated to range from $4,000 to $1 million, assuming 0.1  to 80 Mgal/d (USEPA,  1980).

Rapid infiltration systems are estimated to have from $30,000 to $3 million capital  costs and
$3000 to $200,000 annual operation and maintenance costs, assuming a wastewater flow
of about 0.1 to 25 Mgal/d  (USEPA, 1980).

Overland flow systems are estimated to have from  $80,000 to $10 million capital  costs and
$5000 to $200,000 annual operation and maintenance costs, assuming a wastewater flow
of about 0.1 to 30 Mgal/d  (USEPA, 1980).

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WASTEWATER MANAGEMENT                                                         8-15
Availability

The application of waste water to land is used as a treatment practice in many countries, and
is widely available as it requires a minimum of technology.  The spread of information may
need to be facilitated, however, to ensure that proper techniques are used to prevent the
production of methane and to avoid contaminating vegetation or groundwater.
Applicability

Land  treatment  is a suitable method for stabilizing both untreated and partially  treated
wastewater with any amount of organic content, and is most often used to treat wastes from
food processing plants. Because of its low cost, there is growing interest in using this method
to stabilize municipal wastewater (Loehr, 1984).
Barriers

Possible  barriers to the land treatment of wastewater include land  cost  and availability,
ownership, and the difficulties of transporting wastewater over long distances. In addition,
misapplication of raw or partially treated wastewater to crops and other areas could result in
health hazards and risks to nearby habitats.
Benefits

Some benefits of land treatment, in addition to the prevention of methane emissions, are listed
below.

    •   Land treatment prevents odors.

    •   Land treated water can serve several useful purposes during and after its treatment
       (e.g. recharging ground water, irrigation).
                       Land Treatment

                       *  no advanced technology required
                       *  generally low-cost strategy
                       •  reduced odors
                       *  suitable for a  wide range  of  waste
                          streams
                       •  useful purposes for land-treated water
                       *  methane emissions can be eliminated if
                          aerobic conditions are maintained

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8-16                                                       WASTEWATER MANAGEMENT


8.3  Recovery  and  Utilization/Flaring   of  Methane  from  Anaerobic
      Digestion of Wastewater and Sludge

An alternative to preventing methane production in wastewater and sludge is to encourage
anaerobic conditions in the wastes through anaerobic treatment (digestion).  The resulting
emissions of methane and other gases can be recovered and utilized as an energy source or
flared (burned) off.

   Utilization:  Methane generated during anaerobic digestion can be  captured and used as
   a source of fuel to heat the treatment facilities or sludge digestion tank, produce power
   for other parts of the plant, or for sale to nearby homes, industrial plants or utilities.

   Flaring:  Flaring involves the recovery and diversion of the generated methane to a burner,
   where its combustion prevents its release to the atmosphere.  Flaring can be used to
   dispose  of all of the methane or excess methane which cannot be utilized.


8.3.1 ANAEROBIC DIGESTION WITH METHANE UTILIZATION

Anaerobic digestion involves placing wastes in an enclosed tank (digester) at temperatures of
around 35°C (95°F) for an average of  10 to 60 days.  During this time, organic  matter is
degraded in the absence of oxygen by microorganisms such as fermentative bacteria and
methanogenic bacteria, and converted to biogas (about 60 to 70 percent methane and 30 to
40 percent carbon dioxide, with traces of hydrogen sulfide, hydrogen and carbon monoxide).
The necessary microorganisms grow naturally, but can be encouraged by recycling portions
of the bacteria-laden sludge back into the digester vessel.  For especially highly-concentrated
organic wastes, additional bacteria may be needed and can be purchased or grown on-site in
side-stream bioreactors  (Strauss,  1992).

Several processes exist for digesting wastewater from municipal systems or industrial plants
before the sludge is removed.  One such method is the  Upflow Anaerobic Sludge Blanket
(UASB): wastes enter through the bottom of the digester, travel through  an anaerobic  layer
of sludge, and exit from the top (Loehr, 1984; De Santo, pers. comm.). Another example is
the one-step wastewater treatment process used in Brazil  (Bartone, pers. comim.).   More
commonly,  however, anaerobic digestion is used to treat only the sludge which is removed
from liquid  wastes during primary, secondary, and/or advanced wastewater treatment (see
Exhibit 8-1). This is the most common method of stabilizing sludge in many countries (e.g.,
60 percent of the sludge produced in the U.S. and Europe; almost half of the sludge in Japan)
(Murakami, 1988).
Utilization Technology Description

The "biogas" generated during the digestion  of either wastewater or sludge is composed
mostly of methane, and can be captured and  utilized as a fuel source.  Methane generated
from municipal and industrial treatment plants can be used to heat the  buildings at the
wastewater treatment plant or the sludge digestion tank. In some cases, the methane is used
to produce power for use in other parts of the plant, and the cooling water from the engine-

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WASTEWATER MANAGEMENT                                                        8-17
driven generators is used to heat the digestion tank. Methane or the energy which it creates
can also be sold to nearby industrial plants, utilities, or homes.
Costs

Anaerobic  digestion systems are  estimated to cost from  $100,000 to  $3 million for
construction, and about  $10,000  to $100,000 per year for operation and maintenance,
assuming a wastewater flow  of about 0.1 to 100 Mgal/d (USEPA, 1980).

Although the costs of digestion and methane utilization facilities are high, the energy value
of methane often makes its recovery and use cost-effective.  This is especially true at sites
with high strength organic waste streams and where primary (undigested) sludge is used. In
food processing plants, for example, it is estimated that replacing oil with the generated gas
as fuel for the plant could show a capital return in about five years (IPCC, 1991). Treatment
plants in Japan have found electricity generation from sludge-generated methane to be cost-
effective at large plants. With the addition of heat recovery technologies, these plants have
recorded over 80 percent thermal  efficiencies for gas engine systems, and have achieved
energy production levels  of 2 kilowatt  hours (kWh) for every cubic  meter of  digester gas
(Sato,  1984).
Availability

Anaerobic digestion technologies are widely available and used in most of Europe and in the
U.S. and Japan, and less commonly in some developing countries.  These techniques are
feasible in most areas where an adequate amount of raw sludge is consistently available.
Other factors, however,  may affect the suitability of this option  for certain areas; these
factors are discussed in the following sections.
Applicability

Anaerobic treatment systems with methane recovery and  utilization are suitable in large
operations that have both high strength organic wastes and  large energy demands, such as
food processing plants.  Although methane production rates  from waste streams  vary
significantly, estimates indicate that waste from food processing plants can produce up to 0.9
cubic meters of methane per kilogram of volatile solids destroyed (Loehr, 1984).  Methane
utilization may not be as cost-effective at small municipal treatment plants due to the small
amounts of sludge generated.

Levels of methane  production from digestion are not always suitable for the energy needs of
each plant, which  may differ based on climate and fluctuations  in waste loads.  When the
methane produced is not sufficient to supply fuel for all of the plant's needs, auxiliary power
sources such as natural gas and fuel oil are often needed as supplements.

Methane utilization technologies can also be applied to small operations and domestic waste
streams.  In  parts of India, methane generated from simple digestion tanks attached to
communal latrines provides heat and light for local communities  (Escritt, 1984).

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8-18                                                         WASTEWATER MANAGEMENT
Barriers

The advanced technologies and high capital costs of these technologies can pose barriers to
their spread and use.  Anaerobic digesters and methane  utilization facilities also require
continuous and careful operation.

Another potential barrier is the impurity of the generated methane: digester methane contains
corrosive elements such as hydrogen sulfide (H2S) and mercaptans.  Plants which utilize the
methane can either use it directly in engines designed to burn low quality gas as a fuel, or can
install equipment to scrub the H2S to acceptable levels for use as a higher grade gas fuel
source. The costs of the specialized machinery or scrubbing equipment, or the maintenance
costs for machinery using unscrubbed gas, can lower the possible profit margin from methane
utilization.  The generated methane also has a low energy value compared with conventional
fuels (600 BTU per cubic foot compared to 900 BTU per cubic foot for natural gas). These
two factors, coupled with low conventional fuel prices (such as the currently low natural gas
prices in the U.S.), may make flaring a more cost-effective  option.
Benefits

Anaerobic digestion of sludge has many benefits:

   •   This stabilization process requires less space than aerobic processes and can reduce
       sludge volume more quickly, depending on the type of sludge.

   •   Anaerobic digestion removes  up to 95 percent of the  organics in the sludge  and
       effectively inactivates pathogens (Loehr,  1984).

   •   This treatment method produces valuable methane.

The utilization of methane from anaerobic digestion not only prevents the release of methane
to the atmosphere, but can also provide enough  energy to make the digestion process cost-
efficient or profitable.
                       Anaerobic  Digestion  with   Methane
                       Utilization

                       *  technologies available
                       *  methane emission prevented
                       Ť  valuable fuel source produced
                       Ť  cost-effective when methane utilized

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WASTEWATER MANAGEMENT                                                        8-19


8.3.2 FLARING

Reduction Technology Description

Where utilization technologies are not available or are not economically feasible, flaring is an
effective method of disposing of methane generated from wastes.  Flaring  involves the
recovery of methane from the digester tank and  its diversion to a flame, where it is burned.
Efficient flaring  operations, such  as most operations  in the  United  States, can  reach
efficiencies of 98 to 100 percent (Farrell, 1992), thus preventing the release of methane to
the atmosphere.
Costs

Anaerobic  digestion systems are estimated to cost from $100,000 to  $3 million for
construction, and about $10,000 to  $100,000 per year for operation and maintenance,
assuming a wastewater flow of about 0.1  to 100 Mgal/d (USEPA, 1980).

The  costs  of flaring  equipment  and operation are low, relative to methane utilization
equipment  costs. Flaring methane, however, prevents its utilization and thus cannot offset
the costs of the digester construction  and  operation.
Availability

Flaring technologies are widely available.  Flaring methane should be feasible in any region
where anaerobic sludge digestion is practiced, due to its minimal technological requirements
and low operational costs.
Applicability

Flaring is the primary means of methane control in plants that do not recover and utilize
generated gas, and is a common method of eliminating excess gas in plants which do use
recovery techniques.

Flaring is also a suitable way to eliminate methane emissions from anaerobic water treatment
ponds, which are used increasingly in Brazil and other regions for treating wastewater and
sludge in a one-step process; rates of methane release from such systems may be too low to
merit utilization.
Barriers

Because methane which is flared cannot be utilized for other purposes (e.g., heating digesters
in the treatment plant), the cost of powering the treatment plant may prove prohibitive in
flaring operations.

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8 - 20                                                        WASTEWATER MANAGEMENT
Benefits

Anaerobic digestion has many advantages (see Utilization section). Flaring the generated
methane also provides the following benefits:

   •  Flaring prevents methane emissions.

   •  Flaring helps to eliminate odors which result from anaerobic processes, and avoids the
      hazards associated with free-floating combustible gases.
                       Anaerobic Digestion with Raring

                       * technology available
                       * reduce risks of free-floating gases
                       ť reduce odors
                       * prevent methane emissions
                       Ť suitablewhengas-scrubbing equipment
                         not available
8.4   Minimization of Methane Emissions During Treatment. Utilization.
       and Disposal of Sludge

Just as methane emissions can be avoided during wastewater treatment, methane production
can be minimized  during sludge stabilization.   Stabilization  processes are important  for
reducing potential environmental and  health problems which  may  be caused  by high
concentrations of organic matter and pathogens in raw sludge. Various means also exist to
safely utilize or dispose of stabilized sludge. These stabilization and disposal options include
aerobic digestion, land application, chemical stabilization, incineration, landfilling, aerobic
composting, and some experimental uses for sludge.
Aerobic Digestion

Aerobic digestion of sludge is similar to anaerobic digestion,  but no methane is generated
because the process takes place in the presence of oxygen.  Pretreated or raw sludge is
placed in a tank, and mechanical aerators or diffusers provide oxygen to the waste in order
to stimulate aerobic bacteria to break down the volatile organic matter in the sludge.  Because
these results can also be achieved under facultative conditions, it is sometimes possible to
aerate only the top several feet of a tank, leaving gases from the bottom portions of the tank
to be absorbed or metabolized as they rise.

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WASTEWATER MANAGEMENT                                                         8-21
The technology for this type of sludge digestion is relatively simple and requires only enough
energy to operate the aerators, as the aerobic microorganisms in the tanks create their own
heat. These systems are estimated to cost from $30,000 to $3 million for construction, and
about $2,000 to $500,000 per year for operation and maintenance,  assuming a wastewater
flow of about 0.1 to 100 Mgal/d  (USEPA, 1980).  Because it is relatively inexpensive and
produces few odors, aerobic digestion is suitable for small operations and densely populated
areas.
Land Application

Land application of sludge is similar to land treatment of wastewater, and does not result in
methane production if sufficient time is allowed between sludge applications.  After sludge
has been properly stabilized, it can be applied to the soil surface or mixed with the upper layer
of soil in liquid, dewatered, or dried form.  Liquid sludge can also be injected below the soil
surface.  The rate of application will depend on the quality  of the sludge and crop nutrient
requirements.

The application of sludge to agricultural areas and forests both stabilizes the sludge solids and
utilizes the available moisture, organic matter, and nutrients. Land application of sludge also
helps improve soil structure, water holding capacity, and organic matter content.  Care must
be taken, however, to avoid potential health problems that could result from the application
of unstabilized sludge to crop production or animal  grazing areas.

Land application costs are generally low, but can vary greatly depending on the volume of the
wastewater flow and on the distances necessary to transport the sludge to application sites.
These systems are estimated to cost from $10,000 to $700,000 for land preparation, and
about $1000 to $100,000 per year for materials and labor,  assuming a wastewater flow of
about 0.1 to 100 Mgal/d (USEPA,  1980).
Chemical Stabilization

The use of chemicals can be a relatively inexpensive and simple method of stabilizing sludge.
Because the chemicals that are added prevent fermentation, no methane is produced during
this process.  Adding chemicals can be used as the sole method of stabilizing sludge or in
combination with other methods. The most common chemicals used for stabilization are lime
and other alkaline chemicals, such as cement kiln dust and fly ash, which raise the pH of
sludge.  Other chemicals that have been used to effectively stabilize sludge include chlorine
and ozone.

Chemically treated sludge can be safely land applied or landfilled, and in some cases it can be
incinerated.  Sludge treated with lime or other alkaline materials can be used directly to
condition and correct the acidity of soil, or as a daily or final landfill cover  material.  Various
other uses have been found for chemically treated sludge after subsequent incineration (see
Incineration section).

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8 - 22                                                        WASTEWATER MANAGEMENT
Incineration

Incineration  involves burning dewatered  or  dried sludge solids  at  high temperatures  in
specially-designed furnaces. This method of disposing of raw or digested sludge is commonly
used in many developed countries (about 15 to 20 percent of the sludge in the U.S. and 55
percent of the sludge  in Japan is incinerated) (Farrell,  pers. comm.; Murakami, 1988).
Incineration can reduce the sludge solids to 10 to 20 percent of  their original volume and
virtually eliminate volatile materials, although products of incomplete combustion can create
emissions problems.

The economic feasibility of incineration depends on the moisture and volatile solids content
of the waste, emission control requirements, and conventional fuel prices.  Incineration can
often be cost effective when dewatered, primary (undigested) sludge is burned, since this type
of sludge often contains sufficient energy value to meet the needs of the incineration facilities.
Burning mixtures of primary and  secondary sludge can also be cost-effective.  Incineration of
secondary sludges, sludges with high moisture  levels,  or highly-contaminated  sludge,
however, may require auxiliary fuels to burn off excess moisture or toxic organic compounds
to levels that meet air emissions  requirements.  Depending on these variables and the type of
system used, incineration is estimated to cost: from $200,000 to $500,000 for construction
with a wastewater flow of less than  0.7 Mgal/d, and to cost up to $2.5 to 5.5  million for
wastewater  flows  of up to 100 Mgal/day.  Anuual  operating and maintenance costs  are
estimated to range from $10,000 to $1 million,  assuming a wastewater flow of about 0.1 to
50 Mgal/d (USEPA, 1980).

The main limitation to this technology may be concern over air emissions, which  may make
it difficult to site incinerators near the urban centers where much  sludge is generated.
Incinerating  sludge can also create ash disposal problems, as the ash which remains after
combustion  often contains concentrated levels of heavy metals  and thus has  limited use
options.  In some cases, incinerated ash may be considered  a hazardous waste, potentially
causing  problems  if disposed  of in  a poorly  designed landfill.   Some use and disposal
possibilities being tested include using these materials as ingredients for bricks and pavement
subbases, and  as  fluxing  agents in smelters.  Incinerated  ash from limed sludge  is less
hazardous, and in Japan it is substituted for lime in some soil conditioning processes and used
as a cover at sanitary landfill sites and as top soil (Murakami, 1988).

An  extreme form of incineration, sometimes called  "melting," involves heating sludge to
temperatures of around 1300 to 1500 °C. At these temperatures, the inorganic materials
(silica, iron, aluminum,  calcium, magnesium, potassium and  sodium)  are transformed into a
relatively safe substance termed slag.  Cooled slag has been approved in Japan for use as a
subbase for bicycle roads and footpaths, and as a concrete aggregate. It may also be possible
to mold slag into usable plates or  blocks for construction (Murakami, 1988).
Landfillinq with Methane Recovery

About 25 to 30 percent of the sludge produced during wastewater treatment in the U.S. and
Europe is co-disposed with municipal solid waste in landfills, where it appears that the sludge
may stimulate methane production (Farrell, pers. comm.).  While this disposal method has
potential to cause greater methane emissions at open landfills, the landfilling of sludge is an

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WASTEWATER MANAGEMENT                                                        8-23
excellent option at sites where methane is recovered and  utilized (see Landfill chapter).
Sludge landfills in operation have incurred costs of about $220 per dry metric ton of sludge,
including the costs for dewatering and hauling the sludge, landfill capital, and operation and
maintenance (USEPA, 1989).

A related method of sludge disposal is sometimes called anaerobic composting. This strategy
involves  placing primary sludge in sludge-only landfills, where it is stabilized by anaerobic
bacteria over a period of about ten years. In some cases, plans have  been made to recover
this material for land application (Howe and Coker, 1992).  Methane emissions from this type
of sludge management can be eliminated if the gas produced in the landfill is recovered and
utilized.
Aerobic Composting

Aerobic composting is a relatively quick method of transforming sludge into a useful resource.
This process involves placing raw or digested sludge into aerated pikes, vessels, or open
windrows (stacks of raw  composting  material),  and allowing  the organic  material to
decompose aerobically. The presence of oxygen is ensured by mechanical aeration, or turning
in the case of windrows. The complete composting process generally lasts 20 to 60 days
(Biocycle, 1991).

While sludge can be composted alone, there is growing interest in co-composting sludge with
bulking  agents such as sawdust, wood chips, yard litter and agricultural wastes.  Although
yard and agricultural wastes can be difficult to manage, they are valued for their ability to
enhance the composting process and add organic nitrogen and nutrients to the final product.

Because aerobic composting naturally takes place at relatively high temperatures, pathogens
are destroyed as a result of the process.  The final product therefore has many possible
beneficial uses.  These include: soil enrichment of gardens, plant  nurseries, and croplands;
production of potting mixes and topsoil; turf production and maintenance; and reclamation of
disturbed lands.  The market for composted sludge in the U.S. is promising (Biocycle, 1991).

Aerobic sludge composting in windrows is estimated to cost from  $30,000 to $2  million for
construction, and  about $10,000 to  $400,000 per year for operation and maintenance,
assuming a wastewater flow of about 0.1 to 100 Mgal/d.  Static pile composting may cost
about $300,000 for construction and  $30 to 40 per dry ton (USEPA,  1980).
Experimental Uses for Sludge

Other options for stabilizing sludge for use as a fuel are in the experimental stage.  These
include the conversion of sludge into oil by pyrolysis (heating to bring about chemical change)
or direct thermal liquefaction, and secondary dewatering and direct use of sludge as a fuel
(Murakami, 1988).  These appear to  be promising, although  expensive, options for  sludge
stabilization and disposal.

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8-24
WASTEWATER MANAGEMENT
                       Minimize Methane During Sludge
                       Treatment and Disposal
                         many technologies available; others
                         under research and development
                         reduce health risks by stabilizing
                         organics
                         reduce odors
                         reduce methane emissions
                         substantially reduce sludge volume
                         treated sludge useful for land
                         reclamation
                         cost-effective in many cases
                         produce energy

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WASTEWATER MANAGEMENT	8 - 25


8.5  References

Contributions were made by:

   Carl Bartone, Urban Development Division, World Bank, U.S.A.

   Robert Bastian, Office of Wastewater Enforcement and Compliance, USEPA, U.S.A.

   Nadine DeSanto, Marketing Coordinator, Biothane Corporation, U.S.A.

   Dr. Joseph Farrell, Water and Hazardous Waste Treatment Research, EPA/ORD, Risk
   Reduction Engineering Laboratory, U.S.A.

   Joseph Lagnese, environmental engineer, U.S.A.

   Steve Maber, Water and Sanitation Division, World Bank, U.S.A.

   Marvin Rubin, Office of  Water, USEPA, U.S.A.

   Katsuya Sato, Japan Environment Agency, Japan

   John L. Strauss,  Biosphere Corporation S.A., Switzerland

   James Wheeler, Operations Branch, USEPA, U.S.A.


Additional information may be found in the following:

Biocycle Staff, eds.  (1991), The Biocvcle Guide to The  Art and Science of Composting,
Biocycle, Journal of Waste  Recycling.  Emmaus, Pennsylvania: The JG Press, Inc.

Escritt, Leonard B. (1984),  Sewerage and  Sewage Treatment:lnternational Practice. William
D. Haworth, ed. Chichester: John Wiley and Sons Limited.

Hammer, Mark J.  (1986), Water and Wastewater Technology,  second edition,  New York:
John Wiley and Sons.

Howe and Coker (1992), "Residuals Recycling at Alcosan- Two New Approaches," in WEF
1992, Proceedings of "The Future Direction of Municipal Sludge (Biosolids) Management:
Where We Are and Where We Are Going"  Specialty Workshop in Portland, OR, July 16-30,
1992, pp 713-730.

IPCC  (Intergovernmental Panel on Climate Change)  (1990), Climate  Change: The IPCC
Response Strategies, prepared by the Response  Strategies Working Group, with WMO and
UNEP. Geneva, June 9, 1990.

Loehr, Raymond C.  (1984), Pollution Control  for Agriculture, second  edition,  Orlando:
Academic Press, Inc. (Harcourt Brace Jovanovich, Publishers).

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8 - 26                                                      WASTEWATER MANAGEMENT
Murakami, Ken, and Yoshio Oshima (1988), "Treatment, Disposal and Utilization of Sewage
Sludge in  Japan- Current  Practice and  Future Direction,"  Proc. 3rd  WPCF/JSWA  Joint
Technical Seminar on Sewage Treatment Technology.

Sato, Kazuaki  (1984), "Digester  Gas Use in Wastewater Treatment Plants  in Japan,"
presented  at 3rd  International  Symposium  on Environmental  Techniques  Development,
October 1984,  Posan, Korea.

USEPA (United States Environmental Protection Agency) (1980), "Innovative and Alternative
Technology Assessment Manual,"  (CD-53), U.S. Environmental Protection Agency/Office of
Research and  Development,  and  EPA/Water Program  Operations, EPA 430/9-78-009,
February, 1980.

USEPA  (1983),  "Design  Manual: Municipal  Wastewater Stabilization  Ponds,"  U.S.
Environmental Protection Agency,  EPA 625/1-83-015, October, 1983.

USEPA (1989), "Environmental Regulations and Technology: Use and Disposal of Municipal
Wastewater Sludge," (WH-595), U.S. Environmental Protection Agency/Office of Water,
EPA 625/10-84-003, March, 1989.

USEPA (1990), Methane Emissions and Opportunities for Control: Workshop Results of
Intergovernmental Panel on Climate Change. Response Strategies Working Group, coordinated
by EPA/OAR and Japan Environment Agency, September, 1990.

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CHAPTER NINE
BIOMASS  BURNING
9.1   Background

Methane Emissions

Biomass burning is a major source of global methane emissions.  Methane, along with carbon
dioxide (CO2). carbon  monoxide (CO) and other trace substances, is one of the forms in which
carbon is released into the atmosphere when biomass is burned. Although typically more than
95 percent of the carbon burned  as biomass is released in the form of C02 and CO, a small
but significant component is released as methane (0.5-1.6% by weight) (Norse,  1991). While
the lack of comprehensive data and consistent measurement techniques make it difficult to
determine  global methane emissions from this source, estimates range from  20 to 80 Tg per
year, or  5 to 15 percent of total annual methane emissions from all sources. Emission rates
are expected to increase along with rates of deforestation and landscape degradation.

Most major sources of biomass burning are anthropogenic and fall into two general categories:
1) large  open fires associated with land management practices, common in  forest, savanna
and crop  ecosystems,  and 2) small-scale  fires  in which biomass is  burned for fuel in
households or industry.

In response to declining agricultural yields and population pressures, farmers  in  many regions
regularly convert forests to cropping  and pasture land.  Many of their land  management
techniques involve the burning of standing vegetation. Shifting cultivation in the tropics, for
example, requires that forests be cut, logging  debris and unwanted vegetation burned, and
the land farmed for several years and left fallow to re-vegetate. Large-scale fires in temperate
and boreal forest ecosystems are also common. Estimates indicate that about 1000 Tg of
woody biomass (Norse, 1991) are burned annually on 1  to 5  percent of the world's land
(USEPA, 1990).

Savanna and rangeland biomass is often  burned to  improve  the quantity and quality of
livestock forage, and  in some regions to eliminate parasites  (Menault, 1991). Agricultural
residues are also burned in the field to return nutrients to the soil or reduce shrubs on
rotational fallow lands. Such agriculture-related burning may account for up to  50 percent of
the biomass burned annually (Ahuja,  1990).

Finally, a large amount of global biomass burning falls under the second general category:
biomass fuel burning in households or industry.  While industrial  biomass combustion may be
increasing in importance,  studies to date  have focused on  emissions from  small-scale
combustion. Firewood, charcoal, crop residues and animal dung are burned  for fuel in small-
scale cooking and heating stoves in nearly half of the world's  households. Pilot studies have
indicated that emission  rates for methane and other non-CO2 greenhouse  gases from this
source are high (8-9  g methane/kg dry fuel wood), resulting in potentially  significant total
emissions.  The combustion of  firewood, for instance, may be responsible  for 10 to 45
percent of the methane released  from all global biomass combustion. Firewood combustion

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9-2                                                                BIOMASS BURNING
in developing countries alone may generate 20 to 50 percent of total global carbon emissions
from biomass combustion (Smith et al., 1992).

The exact nature and composition of the products of combustion vary according to the
following factors:

   • Fuel size, composition and distribution;
   • Fuel chemistry; and
   • Moisture content of fuel.

These fuel characteristics affect the duration of the different phases of combustion (flaming,
smoldering and glowing), each of which is associated with a different level of combustion
efficiency (CE).  The percentage of C02 in the combustion products increases as the CE
increases, while the release of methane, non-methane hydrocarbons (NMOCs) and particulates
is enhanced during incomplete combustion phases. Studies show that methane emission rates
from smoldering fires (with CEs of 50 to 80%) are often 2 to 3 times higher than those from
80 to 98 percent efficient flaming fires (Norse, 1991).

In  addition  to  instantaneous emissions, research indicates that  enhanced  biogenic soil
emissions following  open fires may result in continued emissions of methane, N2O and NO for
several years.
Methane Emissions Reduction Strategies

Ongoing work has identified a number of options that could potentially  reduce methane
emissions from biomass burning. These options include:

Reducing the frequency, area and amount of biomass burned:

    • Forests:
       - Increase productivity of existing agricultural lands;
       - Lengthen rotation times of shifting agriculture;
       - Enhance forest resource utilization;
       - Apply alternative silvicultural practices in forest systems;
       - Implement fire management programs;
       - Incorporate charcoal into the soil  after burning;
       - Clear-fell forest before or instead  of burning;

    • Grasslands:
       - Increase grassland management;
       - Substitute game ranching for domestic livestock;
       - Develop fodder trees to feed livestock;

    • Croplands:
       - Compost or  incorporate crop residues into soil;
       - Increase use of crop residues as household fuel;

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BIOMASS BURNING                                                                  9 - 3
      - Replace annual or seasonal crops with tree crops;
      - Minimize soil disturbance;

Improving efficiency of biomass used as fuel:

   • Increase efficiency of biomass cook stoves;
   • Develop high-efficiency gasifiers for crop residues; and
   • Switch to alternative fuels.

The feasibility of some of these options has been demonstrated in many regions of the world.
The  potential for reducing methane  emissions from biomass burning has received some
attention, but further work is need  to fully quantify management impacts.   Substantial
research efforts are required to determine the quantity and types of emissions released and
the potential for reducing these emissions.  Since strategies that focus on reducing  or
modifying biomass burning will affect other greenhouse gases as well, assessing  response
options  will require a comprehensive accounting of the greenhouse gas balance.  Research is
also  needed  to identify the reduction options which  are culturally, economically and
ecologically appropriate for each region, and which will not threaten food security.

Other collateral benefits will  result from  reducing  biomass  burning.   These include
maintenance of forest and agricultural resources, reduced soil erosion, and the protection of
human  health,  life and  property.   Several strategies have already  gained international
acceptance for  their potential to protect species diversity and reduce rates of deforestation.
For example, implementation of one hectare of agroforestry in tropical latitudes can offset 5
to 20 hectares  of deforestation (Dixon, 1992).  The multiple crops and sustained  nature of
agroforestry offer other benefits. These and other areas of possible research are discussed
on the following pages.
9.2   Opportunities for Reducing Methane Emissions
Research to date shows that the burning of crop lands,  grasslands and  forests may be
reduced through sustained land management programs and the promotion of different land use
practices. Emissions from biomass burned as fuel may be reduced through  the use of more
efficient stoves, other combustion devices and fuels.
Reducing the Frequency. Area and Amount of Biomass Burned

   Forests

   •   Increase productivity of existing agricultural lands.  The conversion  of forest and
       savanna to agricultural land could be reduced by the widespread use of sustainable
       agricultural practices which optimize yields and intensive practices which increase
       productivity.   Possible practices include the use of chemical and organic fertilizers,
       biotechnology, improved cultivar species and/or appropriate  management systems
       which minimize soil disturbance.  Reclaiming degraded agricultural lands may also be

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9 - 4                                                                BIOMASS BURNING
      an option.  These efforts could be aided by educational programs designed to provide
      an  understanding of organic  residue management and  the  consequences  of soil
      degradation (Norse,  1991).

   •  Lengthen rotation times and improve productivity of shifting agriculture.   Increasing
      the length of the fallow period and improving crop yields would allow abandoned land
      to reforest, slowing  forest conversion and reducing emissions of greenhouse gases
      (Andrasko  et  al., 1991).   A number of integrated or agroforest  systems can be
      employed to achieve this goal.

   •  Enhance forest  resource use.   Making the harvesting of  forest resources  an
      economically viable alternative to agriculture could decrease forest burning. Possible
      options  include developing  uses for forest  products  and establishing forest and
      agroforest  cropping  systems (Norse, 1991).  Research  is necessary to determine
      appropriate tree species and agroforestry cultivation methods in different regions, and
      the effects of these trees  on regional soils and crops.

   •  Apply alternative silvicultural practices in  forest systems.  Routine removal of interim
      crops can  significantly  reduce fuel load  and  improve  forest productivity.   Forest-
      thinning is a well-developed management option which  could be  an alternative to
      burning.

   •  Implement fire management programs. Fire management programs are designed to
      prevent, detect and suppress  natural and accidental fires. The most common fire
      management tool is prescribed burning, which involves burning excess forest biomass
      under confined and monitored conditions in order to reduce available combustible fuels.
      This practice has been shown to reduce the intensity and size of wildfires.

      Fire management programs have been successfully utilized in Canada, the United
      States and Australia for  many years, and could have significant benefits in developing
      countries where  large areas burn annually; potential for reducing greenhouse gas
      emissions must be explored through study of the ecologies of candidate forests, and
      optimal fire sizes and frequencies.

   •  Incorporate charcoal into  the soil after burning.  Plowing charcoal into forest soil,
      although a labor-intensive  process, could  prevent it from burning again in subsequent
      fires  (Andrasko et al., 1991).

   •  Clear-fell forest before or  instead of burning.  Clear-felling trees and selling them for
      lumber  or other wood products instead of burning them could reduce the amount of
      biomass burned in many regions (Andrasko et al., 1991). The feasibility of this option
      depends on available transportation and markets.

   Grasslands

   •  Increase grassland management. Wildfire prevention similar to forest practices may
      be possible in grasslands. The greatest potential, however, may lie in intensifying land
      management in order to reduce the frequency and area of  fires which are intentionally

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BIOMASS BURNING                                                                  9 - 5
      set to improve forage.  This strategy would require significant research on regional
      vegetation, climate, and cultural practices.

   •  Substitute game ranching for domestic livestock.  Unlike domestic livestock, which
      require the highly-nutritional young forage which grows after grasslands are burned,
      animals native to a region are adapted to naturally occurring vegetation.  Raising native
      game instead of livestock where feasible may therefore reduce burning needs, increase
      forage yield per field, reduce costs, and reduce animal-related  methane emissions.
      Stall-feeding domestic livestock may also be  possible,  but would be constrained by
      local technology and pastoralist lifestyles (Andrasko et al., 1991).

   •  Develop fodder trees to feed livestock. Fodder-producing tree plantations could replace
      pasture as food for stall-fed livestock. This option would  require capital and time for
      phasing in fodder trees. Several thousand multi-purpose tree species which produce
      food, fuel, and fodder have been identified and tested worldwide.

   Croplands

   •  Incorporate  crop residues into soils instead of  burning.  Many common agricultural
      systems, such as shrub-fallow systems and high-yield grain crops, depend on  burning
      to remove biomass from fields and increase soil fertility.  Incorporating crop residues
      into the soil,  although  a labor-intensive  process,  could  increase soil fertility while
      reducing methane  emissions.

   •  Increase use of crop residues as household fuel.   Removing field wastes and using
      them as  fuel in household stoves  or gasifiers could reduce  agricultural  burning.
      Programs to increase cropland  productivity could increase the mass of field  wastes
      available for use as fuel, further reducing the need to burn other types of biomass for
      energy.

   •  Replace annual or  seasonal crops with tree crops.  Tree crops, which do not  require
      periodic burning, may be a suitable alternative,to some annual or seasonal crops.
      Integrated and/or agroforest systems have been employed by farmers in some regions
      for centuries.  Such a transition in new areas, however, would require consideration
      of time and  capital investments, farmer education and market development.

   •  Minimize soil disturbance. Soil-site disturbance generally increases biogenic methane
      emissions.  Alternative management  options,  such  as no-till or  reduced-tilling
      techniques, are available for implementation in many regions. Soil biology, chemistry
      and structure can  also be managed to reduce emissions.
Improving Efficiency of Biomass used as Fuel

   Increase efficiency of biomass cookstoves: Research has shown that it is possible to
   double the efficiency of cookstoves (now typically 10 to 12 percent), thus reducing the
   amount  of  fuel required for  cooking and cost-effectively reducing greenhouse  gas
   emissions by one half (Ahuja, 1990). This process may involve a trade-off: improving the
   stove's heat transfer efficiency reduces  its combustion efficiency,  thus increasing the

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9 - 6                                                                BIOMASS BURNING
   proportion of methane produced. Improved stove models still show reductions in methane
   emissions,  however, because of dramatically decreased fuel requirements.  Accurate
   measurements of thermal efficiencies and emissions from different types of stoves are
   needed.

   Develop high-efficiency gasifiers for crop residues: High-efficiency combustion systems
   such as gasifiers could be used to burn crop residues.  Biomass Degeneration systems
   have also been suggested as an efficient option.  Demonstration and feasibility projects
   would be necessary for the development of these devices.

   Switching to alternate fuels:  Switching from the use of biomass fuels to the use of
   commercial fuels such as kerosene or liquid petroleum gas (LPG) could  reduce total
   resulting greenhouse gas emissions from cookstoves. Such reductions are especially likely
   in areas where  biomass fuel is harvested on a  non-renewable basis, resulting  in net
   deforestation. In these areas all of the CO2 released from biomass burning results in a net
   atmospheric CO2 increase.

   This strategy may  even be beneficial in areas where there is no net deforestation.
   Although CO2 from stoves does not appear to contribute to the greenhouse effect in such
   areas (Ahuja, 1990), the  greenhouse  impact of  emissions  of methane and  other
   greenhouse gases may exceed those from CO2, especially in the short term  (Smith et al.,
   1992; Smith and Thorneloe, 1992).  Fuel switching may thus be justified for its potential
   to reduce these  other gases.  Implementation of this strategy would be constrained by
   availability  and fuel  costs.

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BIOMASS BURNING                                                                 9 - 7


9.3  References

Contributions were made by:

   Kenneth  J. Andrasko, U.S. Environmental Protection Agency, U.S.A.

   Bob Dixon, U.S. Environmental Protection Agency, U.S.A.

   David Norse, Food and Agriculture Organization of the  United Nations, Italy

   Kirk R. Smith, Environment and Policy Institute, East-West Center, U.S.A.

   Darold Ward and Wei Min Hao, Intermountain Research Station, U.S.A.


Additional information may be found in the following:

Ahuja, Dilip (1990), "Research Needs for Improving Biofuel  Burning Cookstove Technologies:
Incorporating Environmental Concerns," in Natural Resources Forum.  May.

Andrasko, Kenneth J., Dilip R. Ahuja, Steven M. Winnettand Dennis A. TirpaM 1991), "Policy
Options for Managing Biomass Burning to Mitigate Global Climate Change," in Global Biomass
Burning: Atmospheric. Climatic and Biospheric Implications. Joel S. Levine, ed., Cambridge,
Massachusetts: MIT Press.

Burke, Lauretta and Daniel Lashof (1989), "Greenhouse Gas Emissions Related to Agriculture
and Land-Use Practices," February, 1989.

Dixon, Bob (1992), USEPA,  personal communication.

Lashof, D.A. and D.A. Tirpak (1990), Policy Potions for Stabilizing Global Climate: Report to
Congress. USEPA, Washington, D.C., EPA/21P-2003.1.

Menaut, J.C., L. Abbadie, F. Lavenu. Ph. Loudjani and A. Podaire (1991),  "Biomass Burning
in West African Savannas," (draft, for J. Levine, ed.. Global  Biomass Burning. Cambridge, MIT
Press).

Norse, D. (1991) "Biomass Burning," Food and Agriculture Organization of the United Nations,
November  (draft).

Smith, Kirk R., R.A. Rasmussen, Ferdinand Manegdeg, and  Michael Apte (1992), Greenhouse
Gases from Small-Scale Combustion in Developing Countries: A Pilot  Study in Manila.
Prepared by Air and Energy Engineering  Research Laboratory, Research Triangle Park, N.C.,
for EPA/OAR and EPA/OPPE

Smith, Kirk R. and  Susan A. Thorneloe  (1992),  "Household Fuels in  Developing Countries:
Global Warming, Health, and Energy Implications," for presentation at EPA Symposium on
Greenhouse Gas Emissions and Mitigation Research, August 20, 1992, Washington, D.C.

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9 - 8                                                              BIOMASS BURNING
USEPA (United States Environmental Protection Agency) (1990), Methane Emissions and
Opportunities for Control: Workshop Results of Intergovernmental Panel on Climate Change.
USEPA, Washington, D.C., EPA/400/9-90/007.

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CHAPTER TEN
RICE  CULTIVATION
10.1        Background

Methane Production. Transport and Emissions

Methane released  during flooded rice cultivation is  a  major source of global methane
emissions.  Methane,is produced in the soils of flooded  rice fields, largely from the anaerobic
decomposition of organic material by methanogenic bacteria. These organic materials include
carbon sources such as root  exudates, soil organic matter, and floodwater  biomass (i.e.
algae), as well as organic fertilizers.

An estimated 60 to 80 percent of the methane which is produced is oxidized in the upper
layer of the soil by aerobic methanotrophic bacteria, and inside the plant, and leached away
with the percolating water as dissolved methane. The remaining, non-oxidized  methane is
transported from the submerged soil into the atmosphere primarily through the intercellular
gas space system of the rice plant; most of this methane is released into the atmosphere from
the plant's culm (an aggregation of leaf sheaths).  Methane is also transported by diffusion
through the floodwater and ebullition (bubbling up of gas). Exhibit 10-1 illustrates emissions
of methane from flooded rice fields as the net result of methane production, oxidation, and
transport to the atmosphere.

The quantity  of methane emitted  by a rice field depends upon several important factors.
These include:

   • Soil factors;
   • Nutrient management;
   • Water regimes; and
   • Cultivation practices.
Methane Mitigation Strategies

Recent research has begun to identify various management practices that could potentially
reduce methane emissions from rice cultivation. Recognizing that increasing rice productivity
and satisfying other social and cultural constraints are fundamental objectives, experts in the
area generally believe that  10 to 30 percent reductions in methane emissions from rice
cultivation, relative to current levels, may be possible over the long term (Braatz and Hogan,
1991). However, much additional research is needed to establish and demonstrate practices
that will maintain or increase rice productivity while reducing methane emissions from rice
cultivation.  Present knowledge indicates that modifications in the following  practices have
the potential to reduce methane emissions:

   • Cultivar selection;
   • Nutrient management;
   • Water management; and

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10-2
                                                                       RICE CULTIVATION
   • Cultivation practices.

Substantial  research efforts are  required to  identify  the most feasible  and regionally
appropriate and feasible methane mitigation opportunities.  Since long periods of time are
required for evaluation of mitigation options and subsequent demonstration, promotion, and
adoption of those options  found to be effective,  it is necessary that comprehensive and
coordinated research take  place over the next several years.  This may best be achieved
through the formation of a research consortium  of the major rice-growing countries, to
facilitate regional and international collaboration and research on methane emission issues.
Different avenues of research which should be pursued  under such a program are outlined
below.
                                     Exhibit 10-1
               Methane Production and Emission from Flooded Rice Held*
          CH4
        Emission
          CH4
        Oxidation
          CH4
        Production
        Leaching - CH4
       Dissolved in Water
                                                                           anoxic

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RICE CULTIVATION                                                                 10-3
10.2       International Research Plan

A comprehensive approach including management of water regimes, development of cultivars,
efficient use of fertilizers, and other management  practices can be formulated to achieve
reductions in methane emissions.  However, current knowledge is insufficient in the areas of
the complex interaction between methane production and oxidation,  as well as the exchange
of methane between the atmosphere and rice fields. The following sections briefly describe
the current understanding of and the types of research needed in each of these areas.
Cultivar Selection

Rice cultivars appear to produce differing amounts of methane over the growing season.
Studies show two or three peaks in emissions occurring during the season, believed to be
times when high concentrations of organic root exudates or root litter are available to soil
bacteria.  Methane production is thought  to be  positively linked to the  amount of root
exudates on the rice variety. Development and use of varieties that minimize root exudation
may, therefore, reduce the quantity of organic matter available for decomposition, thereby
reducing methane emissions.

Certain rice cultivars may also affect the rate of oxygen and methane transport through the
plant (Figure 1). Downward oxygen transport and associated oxidation of methane in the soil
rhizosphere, as well as upward methane transport, may vary among cultivars,  providing
opportunity for  additional methane reduction through cultivar selection.

Cultivar selection  would  be easy to implement  compared to other  methane  mitigation
strategies, and would be practical if rice productivity was maintained. Comprehensive studies
of rice varieties are needed to determine the relationship between rice variety and methane
emission, and whether gas transport and  loss of organic  material from roots affect yields.
Nutrient Management

Several nutrient management techniques are used in rice cultivation, including the application
of raw or composted organic material, and the addition of nitrogen fertilizers (e.g., ammonium
sulfate and urea). The application of nitrogen fertilizers appears to reduce methane emissions
relative to  unfertilized fields and  fields  fertilized with  organic material, particularly if the
fertilizer is deeply incorporated into the soil. This reduction is believed to occur because the
C:N ratio of the  soil is decreased so that more organic  carbon remains in the soil biomass.
In contrast, the application of raw organic material such as rice straw to rice fields, whether
or not in combination with mineral  fertilizers,  appears  to enhance methane emissions.
Composted organic material  also enhances emissions, but to a much lesser extent. Thus the
use of nitrogen fertilizers and/or the replacement of raw with composted organic materials
may be options for mitigating methane emissions.

Nitrification inhibitors also have the potential to limit methane production in rice fields. These
chemicals restrict the bacterial oxidation of nitrogen, thus decreasing nitrogen loss in flooded
soils.  Encapsulated calcium carbide (ECC), a  nitrification inhibitor used  in conjunction with

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10-4                                                                 RICE; CULTIVATION
ammonium sulfate or urea,  releases acetylene  (C2H2), which has been shown to reduce
methane emissions.

Nitrogen fertilizers are already the major sources of N for flooded rice, a primary necessity to
sustaining or increasing rice production in Asia. However, strategies based on using these
fertilizers and other additives such as nitrification inhibitors must be integrated with existing
nutrient management techniques, and their technical and socioeconomic feasibility explored.
Research efforts are needed to  determine the potential  of different types of fertilizers to
reduce methane emissions, the effects of amount, timing and application on emissions, and
the relationships of soil properties with additions of different nutrients.
Water Management

Methane emissions may be influenced by the type of water regime (e.g., inundation period and
drainage schedule) used during rice cultivation.  Draining the rice field during the growing
season or  between crops seems to decrease methane production by increasing the state of
oxidation of the paddy soil.  Studies show, however, that in order to avoid a decrease in
productivity, soil water contents must be kept above 70 percent of saturation during  the
second  half of  the vegetative  stage and before  flowering, when the  rice plants are most
susceptible to drought.

Methane emissions may also significantly decrease with increasing rates of water percolation
because organic substances can be leached away with the percolating water, reducing  the
available substrate for methanogens. In addition, the infiltrating water may introduce fresh
dissolved oxygen into the reduced layer in flooded soils, thus increasing the redox potential
of the soil and inhibiting methane production.

Water management as a possible mitigation practice depends on the physical characteristics
of a region, and is only feasible in certain areas. The most suitable areas for this strategy are
those with lowland and flatland irrigated rice fields, which have highly secure and controllable
water supplies. These techniques are not suitable on terraced hillsides, where drainage may
cause physical  damage to fields (e.g. collapse of terrace construction) and reduced  yields.
Drainage may also be less feasible in rainfed areas, where rice cultivators depend on the water
stored in the fields.

Research efforts should focus on the relative effects of different water management schemes
on methane emissions,  and on determining  which rice ecologies, climatic regions and
socioeconomic  conditions are most suitable for altered water management schemes.  The
effects  of  different  water management schemes on nitrous oxide emissions  is also an
important research issue.
Cultivation Practices

The adaptation of some tillage, seeding, and weeding techniques in order to minimize water
use and mechanical soil disturbance may have potential for decreasing methane emissions
from rice cultivation. The substitution of wet tillage and transplanting of rice seedlings with
dryland tillage and dry seeding, for example, appears to reduce methane emissions.  This is

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RICE CULTIVATION                                                                 10-5
believed to be the result of shortening the anaerobic phase of the growing season, which may
raise the soil redox potential and result in delayed and lower methane production.  Minimum
or zero tillage should have similar effects.

Avoiding the mechanical disturbance of soil  during weeding may also reduce methane
emissions by minimizing the release of gases trapped in the soil. In addition, refraining from
weeding reduces the amount  of  organic  substrate (i.e.,  uprooted weeds) available to
methanogens, which may also contribute to the reduction of methane.

Many cultural  practices  that enhance methane emissions have been developed to suit the
physical, biological, and socioeconomic conditions of different regions, and many reduction
strategies may not be applicable. For this reason, revising these practices in order to reduce
methane emissions will not be appropriate or acceptable unless other rice cultivation changes
make these revisions practical.   Assessing how and  to what  extent land  preparation
techniques, seeding and transplanting techniques affect methane emissions should therefore
be a low research priority.

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10-6
                                                         RICE CULTIVATION
10.3
References
Contributions to this set of technological assessments were made by:

   Kathleen Hogan, Chief, Methane Programs, Global Change Division, USEPA

   Heinz-Ulrich Neue, International Rice Research Institute

   Katsu Minami, Japan National Institute of Agro-Environmental Sciences
The following also contributed to the EPA's Rice Research Plan:
Lex Bouwman
National Institute of Public Health
and Environmental  Protection, RIVM
Netherlands

Barbara Braatz
ICF Incorporated
U.S.A.

Bernard Byrnes
International Fertilizer Development
Center
U.S.A.

Ralph Cicerone
University of California at Irvine
U.S.A.

Alex Guenther
National Center for Atmospheric  Research
U.S.A.

Alan Hills
National Center for Atmospheric  Research
U.S.A.

Kathleen Hogan
USEPA
U.S.A.

Lee Klinger
National Center for Atmospheric  Research
U.S.A.
                                Victor Law
                                Tulane University
                                U.S.A.

                                Charles Lindau
                                Louisiana State University
                                U.S.A

                                Katsu Minami
                                Japan National Institute of
                                Agro-Environmental Sciences
                                Japan

                                Arvin Mosier
                                U.S. Department of Agriculture
                                U.S.A.

                                Heinz-Ulrich Neue
                                International Rice Research Institute
                                Philippines

                                David Olszyk
                                USEPA
                                U.S.A.

                                William Patrick
                                Louisiana State University
                                U.S.A.

                                Heinz Rennenberg
                                Fraunhofer Institute for Atmospheric
                                Environmental Research
                                Germany

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RICE CULTIVATION                                                               10-7
Kurt Roos                                   William Steen
USEPA                                      USEPA
U.S.A.                                      U.S.A.

John Rogers                                 Patrick Zimmerman
USEPA                                      National Center for Atmospheric Research
U.S.A.                                      U.S.A.

Ronald Sass
Rice University
U.S.A.
Additional information may be found in the following:

Braatz, Barbara and Kathleen Hogan, eds. (1991), "Sustainable Rice Productivity and Methane
Reduction-Research Plan," USEPA, Office of Air and Radiation, September.

Neue, Heinz-Ulrich and P.A. Roger (1991), "Methane Formation and Fluxes in Rice Fields,
Principles and Prospects," presented at NATO Advanced Research Workshop on Atmospheric
Methane Cycle: Sources, Sinks, Distributions and Role in Global Change, October 6-11,1991,
Portland, Oregon, U.S.A. (abstract).

USEPA (United States Environmental Protection Agency) (1990), "Methane Emissions and
Opportunities for Control: Workshop Results of Intergovernmental Panel on Climate Change,"
September. (EPA/400/9-90/007)

USEPA (1990), "Workshop on Rice  Research and Methane Reduction: Summary Report,"
September, Washington,  D.C

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