CLIMATE LEADERS GREENHOUSE GAS INVENTORY PROTOCOL

           CORE MODULE GUIDANCE
           Direct Emissions  from
           Municipal Solid Waste
           Land-filling
CLIMATED
U.S. Environmental Protection Agency
October 2OO4

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The Climate Leaders Greenhouse Gas Inventory Protocol is based on the Greenhouse Gas Protocol (GHG Protocol)
developed by the World Resources Institute (WRI) and the World Business Council for Sustainable Development
(WBCSD). The GHG Protocol consists of a corporate accounting and reporting standard and separate calculation
tools. The Climate Leaders Greenhouse Gas Inventory Protocol is an effort by EPA to enhance the GHG Protocol to fit
more precisely what is needed for Climate Leaders. The Climate Leaders Greenhouse Gas Protocol consists of the
following components:

  Design Principles Guidance

  Core Modules Guidance

  Optional Modules Guidance

All changes and additions to the GHG Protocol made by Climate Leaders are summarized in the Climate Leaders
Greenhouse Gas Inventory Protocol Design Principles Guidance.

For more information regarding the Climate Leaders Program, visit us on the web at www.epa.gov/climateleaders

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       M S W  Landfill  Sources    Guidance

1.  Introduction	1
    1.1. Gases Included	1
    1.2. Sources Included	2
2.  Methods for Estimating CH4 Emissions	4
    2.1. Estimating Landfill Methane Emissions at MSW Landfills without
       Active Gas Collection Systems	4
    2.2. Estimating Landfill Methane Emissions at MSW Landfills with
       Active Gas Collection Systems	6
    2.3. Estimating Methane Emissions from a Continuous Emissions
       Monitoring System (CEMS)	10
    2.4. Bioreactor Landfills	10
3.  Choice of  Methods	11
4.  Solid Waste Input Activity Data and Emission
    Calculation Factors	12
    4.1. Solid Waste Input Activity Data	12
    4.2. Emission Factors Data	13
5.  Completeness	16
6.  Uncertainty Assessment	17
7.  Reporting  and Documentation	18
8.  Inventory Quality Assurance and Quality Control	19
Appendix A. LandGEM  Sample Output	2O
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       M S W  Landfill  Sources    Guidance

Introduction
       This document presents guidance for estimating
       direct greenhouse gas (GHG) emissions from
       owned/operated municipal solid waste landfill
sites. This guidance applies to any company whose
operations involve municipal solid waste landfilling.

Sanitary landfilling is  one of the primary methods of
disposing of municipal solid waste (MSW) and has
been an accepted solid waste management practice for
many decades. In 2000, an estimated 128.3 million tons
(or 116 million metric tonnes), representing approxi-
mately 55.3 percent of the reported 231.9 million tons
(or 210.5 million metric tonnes) of MSW generated
within the United States was managed through landfill-
ing1. A direct result of solid waste landfilling is the
generation of a natural by-product known as landfill
gas (LFG) which is formed through the biodegradation
of the decomposable  organic fraction of the MSW land-
filled. The gas is generally composed of 30 to 60
percent methane (CH4) depending on a number of fac-
tors with the balance primarily carbon dioxide (C02).
Other minor constituents present in the gas can
include oxygen and nitrogen, trace amounts of hydro-
gen, hydrogen sulfide, volatile organic compounds
(VOCs), and moisture. Depending on site characteris-
tics, the LFG generation process can create internal
positive pressure within the waste mass allowing
for the fugitive emission of produced gas through
permeable areas or pathways of least resistance within
the final and temporary cover systems, leachate collec-
tion system and risers, landfill side slopes, etc.

Sources of GHG emissions from municipal solid waste
landfilling include the fugitive release of landfill gas as
well as stationary combustion sources, such as LFG
flares and LFG energy (LFGE) facilities. Additional
sources of GHG emissions include; fleet vehicles,
landfill compactors, earthmovers and other equipment
or machinery that is a necessary or typical part of the
landfill operation that uses fossil fuels.

1.1.  Gases Included

Although CH4, C02, and minor trace gases are all
emitted from fugitive landfill gas release, methane
accounts for the majority of GHG emissions from MSW
landfills2. MSW landfills are the largest human-made
source of CH4 emissions  in the U.S. Landfill gas is made
up of approximately equal amounts (on a volumetric
basis) of CH4 and C02 gas, however, only CH4 is
addressed within this protocol. The C02 produced
through the anaerobic biodegradation of MSW
(C02 fraction of LFG) is not reported. It is assumed
that waste decomposition does not contribute to the
net addition of C02 to the atmosphere. This exclusion
is consistent with Intergovernmental Panel on Climate
Change (IPCC) guidance3.
1 U.S. EPA. Municipal Solid Waste in The United States: 2000 Facts and Figures. 2000 Update; EPA530-R-02-001.

2 In landfills, some carbon from waste can remain stored for long periods of time. The removal of carbon from the natural cycling of carbon between the
  atmosphere and biogenic materials - which occurs when wastes of biogenic origin are deposited in landfills - sequesters carbon. (Wastes of biogenic
  origin include paper, wood products, and yard trimmings, but do not include plastics or other synthetic organics) When wastes of sustainable, biogenic
  origin are landfilled, and do not completely decompose, the carbon that remains is effectively removed from the global carbon cycle. While EPA is con-
  tinuing to study methodologies to measure this type of carbon storage, currently considerable uncertainty remains and thus Climate Leaders does not
  include this process in its GHG accounting.

3 "Decomposition of organic material derived from biomass sources (e.g., crops, forests) which are regrown on an annual basis is the primary source of
  C02 released from waste. Hence, these C02 emissions are not treated as net  emissions from waste in the IPCC Methodology." Revised 1996 IPCC
  Guidelines for National Greenhouse Gas Inventories: Reference Manual, Chapter 6. Waste, Section 6.1 Overview, pg. 6.1.
                               CLIMATE  LEADERS  GHG  INVENTORY  PROTOCOL

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                                      M S W  Landfill  Sources    Guidance
        C02 can also be produced from the combustion
        of CH4 in captured LFG, this is considered
        biomass C02. As with emissions from other
        biofuels combustion, Climate Leaders consid-
        ers that biomass C02 emissions do not
        contribute to C02-equivalent emissions as
        reported in a Climate Leaders Partner's entity-
        wide inventory4. Therefore, the biomass C02
        emitted through the combustion of captured
        LFG are reported but only as a memo item in
        the Partner's inventory. Climate Leaders
Partners are required to account for emissions
of methane from MSW landfill sites.

1.2.  Sources  Included
This guidance covers emissions associated
with LFG. When considering LFG emissions
there are different factors to be taken into
account including; production of the LFG,
recovery of the gas, and treatment of the gas
as shown in Figure 1.
             Figure 1: Scope of Emissions Covered  in This Guidance
                                                                      = Included in this Guidance
                              LFG Generated

                                \Collection
                                 System    I
                                Efficiency /
            CH4 Oxidation in Cap
                              Vented   '              ri/n        On-Site Electricity/
               CH4 Emissions (on-or off-site) 1          t-iared/uirect use steam Generation
                                 I      [Sold Off-Site       1              1
                           CH4 Emissions i           CO2 (biomass)    CO2 (biomass)
                                            1       Emissions       Emissions
                                         CH4 Sold
                              Electricity/
                             " Steam Sold
        4  This assumes no net loss of biomass-based carbon associated with the land use practices used to produce these fuels. This
          approach is consistent with that used by the U.S. EPA in conducting the National Inventory, U.S. EPA 2004 Inventory of U.S.
          Greenhouse Gas Emissions and Sinks: 1990-2002, EPA430-R-04-003, April 2004. Also,"C02 emissions from landfill gas recovery com-
          bustion are of biogeneic origin and should not be included in National Totals." IPCC Good Practice Guidance and Uncertainty
          Management in National Greenhouse Gas Inventories, Chapter 5. Waste, Section 5.1.1.2, Methane Recovery pg. 5.10.
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       M S W  Landfill  Sources    Guidance

As mentioned in Section 1.1, projects using LFG
as a fuel in stationary or mobile sources report
the biomass C02 emissions from the combus-
tion of LFG (oxidation of carbon in the LFG) as
a memo item in the inventory5. Methods for
estimating emissions from combustion of LFG
are covered under additional Climate Leaders
guidance. Carbon dioxide emissions resulting
from a flare or an LFG (or LFG supplemented)
electrical power generation station are calcu-
lated according to the Climate Leaders
guidance for Direct Emissions from Stationary
Combustion Sources. Emissions resulting from
liquid or compressed fuels derived from LFG
used in a Climate Leaders Partner's truck or
vehicle fleet are calculated according to the
Climate Leaders  guidance for Direct Emissions
from Mobile Combustion Sources.  Furthermore,
any additional sources of emissions from land-
fill operations, for example, combustion of
fossil fuel in mobile sources or purchases of
electricity, are also reported separately using
the appropriate Climate Leaders guidance.
Climate Leaders Partners are only responsible
for direct emissions at their facilities. If carbon
is sold and leaves the facility stored in  a prod-
uct it should not be counted as a release even
if the product is subsequently burned or other-
wise releases
the stored carbon.

In addition to reporting  of direct emissions,
there is also the potential that landfills  can
report savings due to collection and treatment
of CH4 that would otherwise have been
released to the atmosphere. Guidance for
reporting these reductions is currently under
development.
5 This assumes carbon in LFG is of biogeneic origin and that there is no net loss of biomass-based carbon associated with land use
  practices surrounding the biomass that ultimately decomposes in the landfill to produce the LFG.
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                                M S W  Landfill Sources  Guidance
       Methods  for  Estimating  CH4
       Emissions
          In general, there are two approaches used    potential (L0), and the methane generation
          to estimate CH4 emissions from MSW land-   rate constant (k) to estimate potential annual
          fills, depending on the presence or absence   emission rates from landfill sites. The
       of a gas recovery and control system.          LandGEM is based on Equation 1.
         MSW landfill sites in which gas collection
          systems are absent: use mathematical
          models and apply appropriate default
          factors (see Section 2.1).

         MSW landfill sites with landfill gas recovery
          and control systems: monitor recovered
          landfill gas and apply gas system collection
          efficiency data (see Section 2.2).

       2.1.  Estimating
       Landfill  Methane
       Emissions  at MSW
       Landfills without
       Active Gas  Collection
       Systems

       Through the  Control Technology Center, the
       U.S. EPA has  developed an emissions model
       known as the "Landfill Gas Emissions Model" or
       LandGEM. The model is a tool used to estimate
       annual emission  rates over a user-specified
       interval for methane as well as carbon dioxide,
       non-methane organic compounds (NMOC), and
       a list of other air pollutants. The LandGEM
       model has been implemented within a stand-
       alone software application distributed and
       supported by the U.S. EPA.

       The model uses a first-order decay rate equa-
       tion and operator-entered data for annual
       reported MSW tonnage,  methane generation
       Equation 1: Waste
     Decomposition Model
 where:

 QCH4

 k
 M,
methane emission rate, m3/yr

methane generation rate
constant, year1

methane generation poten-
tial, m3 of CH4/Mg of refuse

mass of the waste in the ith
section (annual increment),
Megagrams (Mg)

age of the ith increment (or
section), in years
This equation computes the methane emission
rate from one annual increment of waste where
Mj is the mass in Megagrams (Mg) (or metric
tonnes) of the annual waste increment and ts is
the age of the ith increment, in years. The mass
of any non-MSW may be subtracted from the
total waste mass in a particular section when
calculating the value for the mass of waste
in that section. The methane emission rates
are summed over all past annual increments
to estimate the total current methane
emission rate, which is further represented
in Equation 2.
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       M S W  Landfill  Sources    Guidance
   Equation 2: Summation of
     Annual Emission Rates
 Q
  CH4
        1=1
 where:

 QCH4

 k
 M,
methane emission rate, m3/yr

 methane generation rate
constant, year1

 methane generation poten-
tial, m3 of CH4/Mg of refuse

 mass of the waste in the fh
section (annual increment),
Megagrams (Mg)

 age of the th increment (or
section), in years
The estimates of landfill methane emissions
from the model only consider methane genera-
tion and not landfill methane released to the
atmosphere. As shown in Figure 1, not all LFG
that is generated gets released to the atmos-
phere. A portion of the methane generated may
be oxidized while passing through the landfill
cover, through soils used for daily cover, and
through alternative cover materials such as
compost used for odor control in, or on, land-
fill covers. Landfill methane emissions from
sites without active LFG recovery systems are
equal to the methane generation less the
amount of methane oxidized based on the
above potential oxidizing sources.

Based on the site size and gas management
practiced, some landfills may have installed
passive controls (wells, horizontal collectors
and/or trenches) which simply vent collected
gas to the atmosphere. Passive controls rely
on the gas generation and internal pressure
created within the waste mass to move the gas
through diffusion and/or convection to the
atmosphere. To date, there are no industry
standard accepted collection efficiencies for
passive LFG venting systems. If the methane
emissions resulting from a passive venting sys-
tem are measured, the emissions are a fraction
of the overall gas emission estimated using the
gas generation model. Passive controls may
reduce the potential for methane to be oxi-
dized.

Equation 3 describes the calculation to convert
methane generated into methane emissions,
default values for factors used are provided in
Section 4.2.

  Equation  3: Estimating CH4 Emissions
             Based  on Generation

 CH4 Emissions = CH4 generated x (1 - oxidation factor)
                             The methodology used to determine methane
                             emissions from MSW landfills through the gas
                             generation method is as follows and assumes no
                             active or passive gas control is implemented:

                             Step 1:  Determine the landfill methane gen-
                                  eration rate. This is done using the
                                  LandGEM model as described above and
                                  following the user manual to enter
                                  required landfill and model data and step
                                  through the program. Input data include
                                  Mg (metric tonnes) per year of municipal
                                  solid waste accepted and buried, the year
                                  the landfill opened, the current year, land-
                                  fill design capacity, landfill closure year,
                                  and waste in place. Input data includes
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                                   M S W Landfill  Sources   Guidance
            the methane generation potential (L^, the
            methane generation rate constant (k) and
            selected methane concentration. A
            Climate Leaders Partner may also make
            these calculations directly using the first-
            order decay equations that are the basis
            of the LandGEM model if so desired.

       Step 2:  Determine the fraction of methane
            oxidized. Landfill gas may pass through
            the landfill cover, intermediate cover soils
            or alternative cover materials (compost)
            before being released to the environment.
            There is the potential that microbes in
            the soil or cover material may oxidize
            some of the methane in the gas. This oxi-
            dation reduces  the amount of methane
            released to the  environment. The Climate
            Leaders approach is to use a default fac-
            tor of 10/6 for the fraction of methane
            oxidized.  Refer  to Section 4.2 for discus-
            sion of default parameters.

       Step 3:  Calculate methane emissions. Once
            the above parameters are known
            Equation  3 can  be used to determine
            amount of methane emissions. Methane
            emission  rates have to be converted from
            volume to mass through a simple conver-
            sion calculation based on the assumed
            density of methane.

       Note: If the Climate Leaders Partner proposes
            to use measured flow rates from a passive
            gas collection and venting system to deter-
            mine the net methane emission based on
            the collection efficiency of the passive sys-
            tem, a methodology must be presented for
            determining the passive collection efficien-
            cy. There  is no widely accepted method for
            doing so.  Therefore this approach has not
     been considered in the above methodolo-
     gy or the example for estimating methane
     emission from MSW landfills without active
     LFG collection systems.

2.2.  Estimating
Landfill  Methane
Emissions  at MSW
Landfills with  Active
Gas  Collection
Systems
Methane generation at MSW landfills with
active gas collection systems (that is, incorpo-
rating gas collection systems used to extract
LFG under an induced vacuum applied to the
recovery wells and collection system) could be
estimated using data from the gas collection
system, verified by a qualified third party using
U.S. EPA verification methods, and applying a
collection system efficiency suitable to the site
specific nature of the landfill cover system and
gas collection system installation. The differ-
ence between the methane gas generation
calculated in this manner and the measured
methane gas recovery from the gas collection
system (less the amount of methane oxidized
within the final cover system) plus any vented
gas is the net methane emission to the atmos-
phere. Equation 4 describes the calculation to
convert amount of collected methane into
methane emissions.

The methodology used to determine methane
emission data from MSW landfills through the
active gas collection method is as follows,
default factors are provided in Section 4.2:

Step 1: Determine the amount of methane
     collected. Landfill gas collection and/or
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      M S W  Landfill  Sources    Guidance
             Example CH4  Emissions Calculation for  MSW Landfills
                                without Active  LFG  Collection

A Climate Leaders Partner owns a MSW Landfill Site which has been receiving primarily domestic waste for the past 20 years
and is still active (year opened 1982). Under the NSPS regulations the Partner has not yet been required to install a LFG control
mechanism. The landfill site has a permitted capacity of 3 million cubic meters and has annual waste acceptance records from
the time of opening. Average waste compaction density is 0.8 tonnes/m3 (1,350 lb/yd3).  The site is located in a very dry climate
receiving less than 635 mm (25 inches) of precipitation per year. The Partner has not assessed methane emissions previously at
the site.

The Partner uses the Landfill Gas Emissions Model (LandGEM Version 2.01) to calculate the methane emissions using the AP-42
default factors for the methane generation potential (L0 = 100 m3 of CH4/Mg of MSW landfilled) and methane generation rate con-
stant (k = 0.02/yr). The final cover system is one meter of clay and topsoil and does not have a flexible membrane liner.

Step 1 - Estimate current methane generation rate using the LandGEM (Version 2.01):

        Model Inputs:

        Waste disposal    =      annual tonnage of MSW for each filling year (Mg)
        L0              =      AP-42 default (100 m3/Mg)
        k               =      AP-42 default (arid 0.02/yr)

        Design capacity in Mg (or metric tonnes), year landfill opened and current year
        Methane concentration = 50% by volume

LandGEM output yields a  methane emission rate in both mass (Mg) and volume (m3) on an annual basis. Conversion from the
volumetric to a mass emission rate of methane is achieved through the use of the density of methane. The LandGEM Model
assumes a density of methane at 1 atmosphere and 20C, which is equal to 0.667 kilograms/cubic meter (0.0416 lb/ft3). A sample
report generated using LandGEM 2.01 is presented in Appendix A using the above parameters and an average annual waste
acceptance of 80,000 Mg/yr.

Note: If the annual waste acceptance is unknown for any  increment or interval, then the average annual waste acceptance
should be used accordingly.

Step 2 - Determine the fraction of methane oxidized:

        The methane oxidation factor is assumed to be 10% by volume (0.10). (see Section 4.2)

Step 3 - Calculate emissions:

        This is done using the parameters specified above and Equation 3 outlined in Section 2.1

        CH4 Emissions = CH4 generated x (1 - oxidation factor)

        For the year 2003:

        CH4 generated =  1.85 x 103 tonnes (or Mg)/yr. (from the LandGem output shown in Appendix A)

        CH4 Emissions =  1.85 x 103 x (1 - 0.10) = 1.66 x 103 metric tonnes of CH4 emitted in 2003.

Note: Emissions from any on-site combustion device are calculated using the Climate Leaders guidance for Direct Emissions
from Stationary Combustion Sources. Emissions from these calculations, along with any other emissions sources, are added to
the total emissions of the  site.
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                                          M S W  Landfill  Sources    Guidance
        Equation 4:  Estimating  CH4 Emissions Based  on Collection
                  CH4 Collected
CH4 Emissions = [( -	CH4 Collected) x (1 - OF)] + (CH4 Collected x  Vent)
where:
Coll
   eff
OF

Vent
                     Coll
                         eff
CH4 Collected  =   CH4 Collected by active gas collection system
collection system efficiency

oxidation fraction

fraction vented
                  combustion systems generally are
                  equipped with LFG composition and flow
                  monitoring equipment which can be used
                  to continually monitor methane capture
                  from the landfill. In the event flow and
                  composition data are not continuously
                  monitored, routine gas sampling and flow
                  measurement using portable monitoring
                  equipment with data recording capability
                  could be used, providing data can be sup-
                  ported through third party verification
                  methods.

             Step 2: Determine the collection system effi-
                  ciency. With a gas collection system in
                  place there may still be some fugitive gas
                  that is not collected by the system. This
                  could be due to spacing of gas collection
                  wells, gas pressure, maintenance of the
                  cover, etc. Refer to Section 4.2 for default
                  selection of suitable collection system
                  efficiency to  be used.

             Step 3: Determine the fraction oxidized.
                  Landfill gas that is not collected passes
                  through the landfill cover before  being
                  released to the environment. There is the
                  potential that microbes in the soil of the
                                             landfill cover oxidize some of the methane
                                             in the gas. This oxidation reduces the
                                             amount of methane released to the environ-
                                             ment. The Climate Leaders approach is to
                                             use a default factor of 10% for the fraction
                                             of methane oxidized. Refer to Section 4.2
                                             for discussion of default parameters.

                                         Step 4: Determine the fraction of gas vented.
                                             This is the amount of the collected gas that
                                             is vented directly to the atmosphere. It
                                             could either be through an active venting
                                             system, or in some cases gas may also be
                                             vented during scheduled start-up/shut
                                             down periods as well as from a malfunction
                                             of the primary LFG control device.
                                             Estimates should be made for LFG control
                                             device downtime if gas is vented during
                                             that period.

                                         Step 5: Calculate methane emissions. Once all
                                             the parameters are known, Equation 4 can
                                             be used to determine the amount of
                                             methane emissions. Methane emission
                                             rates can be converted from volume to
                                             mass through a simple conversion
                                             calculation based on the density of
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       M S W  Landfill  Sources     Guidance
            Example  CH4 Emissions Calculation based on Collection

A Climate Leaders Partner has a MSW Landfill Site which has been receiving waste for the past 15 years and is still active. Based
on meeting criteria under the NSPS regulations, the Partner has installed a LFG collection and enclosed flaring system. The land-
fill site has  been receiving 300,000 tonnes (Megagrams) of MSW per year and the site is located in a temperate climate receiving
greater than 635 millimeters (25 inches) of precipitation per year. The partner has assessed methane and non-methane organic
compound emissions previously at the site using the Landfill Gas Emissions Model with the required defaults  for NSPS report-
ing. All LFG collected is flared at the site and the gas collection system is currently thermally destroying a consistent average of
1,000 standard cubic feet per minute (scfm) of LFG with a methane concentration of 53% by volume. The landfill is a currently
active with  5 years of operation remaining and will be eventually closed with a low permeability clay cover.

Step 1 - Determine the amount of methane collected:
                                    1,000 ft3/minx 0.53
           CH, collected/year    =    	 x 525,600 minutes/year
              4                          35.31 ft3/m3

                                    7.89 x 106 m3/yr

Step 2 - Determine the collection system efficiency:
        The collection system efficiency is assumed to be 75% by volume (0.75). (see Section 4.2)

Step 3 - Determine the fraction of methane oxidized:
        The fraction oxidized is assumed to be 10% by volume (0.10). (see Section 4.2)

Step 4 - Determine the fraction of methane gas vented:
        Flare station records indicate that approximately 1% (0.01) of the recovered gas  is vented during routine and
        unscheduled maintenance annually. These estimates should be made for flare system downtime if gas is vented during
        that period.

Step 5 - Calculate methane emissions:
        CH4 emissions    =        [((CHj collected/collection system efficiency) - CH4 collected) x (1-oxidation factor)] +
                                [CH4 collected x fraction vented]

        CH4 emissions    =        [((7.89 x 1$ m3/yr/0.75) - 7.89 x 106 m3/yr) x (1 - 0.10)]+ [7.89 x 106 m3/yr x 0.01]
                                [2.63 x 106 m3/yr x 0.90] + 7.89 x 104 m3/yr
                                2.45xl06m3/yr

Note: Conversion from the volumetric to a mass emission rate of methane is achieved through the use of the density of
methane. The density of methane  is equal to 0.667 kilograms/cubic meter (0.0416 lb/ft3) at 1 atmosphere and 20C.

        QCH4 tonnes/yr.    =       2.45 x 106 m3/yr. x 0.667 kg/m3 x 1 tonne/1000 kg = 1,634 tonnes/yr.

Note: The latest version of  LandGEM as described in the previous section and sample calculation is used to estimate the
methane emission rate in the area not served by the landfill gas collection system, as applicable. Also, emissions from any on-
site combustion device would be calculated using the Climate Leaders guidance for Direct Emissions from Stationary Combustion
Sources. Emissions from these calculations, along with any other emissions sources, are added to the total emissions of the site.
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                                         M S W  Landfill  Sources   Guidance
                  methane at standard temperature and
                  pressure conditions.

             The method of estimating landfill methane
             emissions at MSW sites incorporating LFG
             collection systems described in this section
             should be used only for landfill cells or landfill
             areas being served by the gas collection sys-
             tem. Estimation of landfill methane emissions
             for cells or landfill areas not being served or
             equipped with active gas recovery systems
             should be calculated using LandGEM (Version
             2.01), as described in Section 2.1.

             2.3. Estimating
             Methane Emissions
             from  a Continuous
             Emissions Monitoring
             System  (CEMS)

             Neither the New Source Performance
             Standards (NSPS) nor the U.S. Clean Air Act
             require continuous monitoring systems for
             methane emissions on MSW landfills. However,
             the new National Emission Standards for
             Hazardous Air Pollutants (NESHAP) for MSW
             Landfills require procedures for operating and
             maintaining the collection and control system,
             including the continuous monitoring system
             during periods of start-up, shut-down and
             malfunction for LFG active collection systems
             on NSPS landfill sites6.

             The landfill gas combustion systems generally
             are equipped with LFG composition and flow
             monitoring equipment which can be used to
             continually monitor methane capture from the
                                                landfill. This equipment could potentially be
                                                used to monitor other GHG emissions such as
                                                C02 (biomass), CH4, and nitrous oxide (N20)
                                                from stationary combustion sources (see
                                                Climate Leaders guidance for Direct Emissions
                                                from Stationary Combustion Sources).

                                                2.4.  Bioreactor
                                                Landfills

                                                Bioreactor landfills enhance the microbio-
                                                logical process involved within  the landfill to
                                                speed up the rate of waste decomposition.
                                                This enhancement can occur through several
                                                means. If the decomposition process is anaero-
                                                bic, methane gas is produced. Estimating
                                                emissions from bioreactor landfills can be done
                                                using one of the methods outlined in this
                                                guidance. The recommended choice of method
                                                is discussed in Section 3. If emissions are to be
                                                estimated based on the Landfill Gas Emissions
                                                Model (described in Section 2.1 Estimating
                                                Landfill Methane Emissions at MSW Landfills
                                                without Active Gas Collection Systems) the
                                                parameters of the model, and potentially the
                                                model itself, are different than for a standard
                                                MSW landfill. Currently there is  no good data
                                                on appropriate default factors that could be
                                                used to represent bioreactor landfills in this
                                                approach. More work is needed on this area,
                                                therefore, it is recommended that emissions
                                                from bioreactor landfills be estimated based on
                                                an active collection system approach
                                                (described in Section 2.2) or through CEMS
                                                (described in Section 2.3).
             6 40 CFR 63 National Emission Standards for Hazardous Air Pollutants: Municipal Solid Waste Landfills, Final Rule.
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      M S W  Landfill  Sources    Guidance

Choice   of  Methods
       The preferred choice of method used
       to estimate emissions depends on the
       type of information available. If the site
has a gas collection system in place and has
good data on the amount of gas collected and
the methane concentration in the gas, then
the emission calculation method based on gas
collected is preferred. Using the data gathered
from the LFG collection system is likely to
provide a more precise estimate of net gas
emissions than gas modeling, even if the
estimate of collection efficiency is itself
relatively imprecise.
However, if there is no collection system in
place then the modeling approach is the
preferred method for calculating emissions.
The approaches for measuring or recording the
estimated landfill methane emissions in order
of preference are therefore:

1.  Partner has LFG quantity (volume) and
   quality (composition) of LFG captured
   within the gas collection system at the site.

2.  Partner has landfill parameters, waste
   composition data and annual waste accept-
   ance figures for the site and uses LandGEM.
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                                         M S W  Landfill  Sources    Guidance
             Solid  Waste  Input  Activity  Data
             and   Emission   Calculation
                    This section discusses choices of activi-
                    ty data and factors used for calculating
                    landfill methane emissions. This guid-
             ance has been structured to accommodate
             Partners with varying levels of available
             information. Whenever possible, the preferred
             approach described within this document for
             estimating emissions from MSW landfills with
             or without gas collection systems should be
             the option employed to allow for the greatest
             level of accuracy in the landfill methane
             emission estimates.

             4.1. Solid  Waste  Input
             Activity Data
             When calculating landfill methane emissions
             using the LandGEM model, the initial
             information required is the type of waste
             (historical/current) accepted by the landfill
             site and the annual tonnage records, if
             available over the life of the landfill. Generally,
             depending on the landfill size and  age, older
             sites will have only minimal filling records
             available for the late 1960's up to the early
             1980's. In this case, annual tonnage and waste
             stream data can be taken as averages  over the
             years required. If inert material has been
             accepted in known quantities and  landfilled,
             these tonnage data should be subtracted from
             the overall annual MSW figures used in the
             calculation of the landfill methane emissions.
             The next source of data required is the climatic
             condition of the site (i.e., arid with less
             than 635 millimeters or 25 inches of annual
                                                precipitation, or non-arid with greater than 635
                                                millimeters of annual site precipitation), this
                                                determines what default factor is selected for
                                                the methane generation rate constant. If input
                                                parameters other than defaults are used, site
                                                specific data obtained by gas recovery testing
                                                is the next data source. The minimum site data
                                                which must be reported to conduct a methane
                                                emission estimate is 1) the type of waste and,
                                                2) annual tonnage figures.

                                                When calculating landfill methane emissions
                                                based on gas collected, the main initial source
                                                data required is  the volume of LFG annually
                                                captured and measured methane concentration
                                                by volume. This  is the preferred method of
                                                estimating landfill methane emissions based on
                                                assumed or calculated gas  collection system
                                                efficiency. In the case where a collection
                                                system covers only a portion of the site, a
                                                percent coverage must be used and reflect the
                                                overall area of influence for the gas collection
                                                system. The landfill methane emissions from
                                                large portions of the site and cells not contain-
                                                ing LFG recovery systems and equipment are
                                                estimated separately using measured waste
                                                tonnage data and emission model calculations.

                                                Landfill gas is metered in terms of physical
                                                and chemical units (i.e., mass or volume and
                                                percent methane by volume) and it is recom-
                                                mended that Partners track landfill methane
                                                generation, recovery (including composition
                                                by volume) and  emissions to the atmosphere
                                                in terms of these physical and chemical units.
                                                Partners with MSW landfills incorporating gas
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       M S W  Landfill  Sources   Guidance

collection should be continuously measuring
gas recovered through gas collection monitor-
ing systems. However, depending on the
consistency of the sustainable volumes of LFG
recovered, Partners may choose to monitor
methane concentration periodically throughout
the year. Quantity of landfill gas for recovery
and methane composition may vary due to
changes in site conditions, gas line blockages,
damage to LFG system from site activities, sys-
tem down time and fluctuations in anaerobic
conditions (resulting from possible air ingres-
sion). For these reasons, it is recommended
that continuous metering and data computa-
tion of LFG volumetric flow rate and methane
concentration is conducted, for emission
reporting accuracy as well as for future
emission reduction verification requirements.

4.2.  Emission  Factors
Data

A factor that is required for the methane
collected method of calculating emissions is
the LFG collection system efficiency (if one is
installed). Gas collection system efficiency
factors can vary widely depending on the type
of landfill gas collection system (horizontal
versus vertical, or a combination of both),
construction and condition of the landfill
cover, the landfill site characteristics, differen-
tial settlement, moisture, or other factors.

If the landfill is completely served by a gas
collection system, then the waste management
industry assumption has been that a collection
efficiency of 75 percent or greater is typically
achieved.7  This collection efficiency factor is
used as a default by Climate Leaders. Data sup-
porting more precise estimates is not available
and this assumption is likely to provide
estimates that are more precise than using the
LandGEM model for the reasons discussed
within this guidance document.

Over the past several years, many landfills
subject to the New Source Performance
Standards (NSPS) for MSW Landfills
(40 CFR Part 60, Subparts WWW and CC) have
been required to conduct surface sweep
monitoring of landfill emissions. Sites with fully
functional and well-maintained low permeabili-
ty cover systems have been found (indeed are
required) to demonstrate near-zero surface
emissions. Therefore, it is reasonable to
assume that sites subject to the NSPS have a
higher collection efficiency than the above-
mentioned waste management industry
standard assumption. If the Climate Leaders
Partner uses an active collection system
efficiency which is  greater than 75% the
methodology and assumptions used to
determine the site specific collection efficiency
shall be reported. Closed NSPS landfills with
impermeable geomembrane covers and active
gas controls are expected to have a collection
system efficiency greater than 90%, based on
the consistent reporting of near-zero surface
emission measurements.

Climate Leaders Partners may own or operate
MSW landfill sites which simply vent small
amounts of LFG to the atmosphere for safety
reasons and/or to prevent lateral subsurface
migration from the landfill. This is frequently
done using passive venting systems such as
final cover gas vent layers, vent wells, horizon-
tal gas migration cut-off trenches, and
under-slab venting  systems for on-site build-
ings or structures. There are no standard
7 Compilation of Air Pollutant Emission Factors, AP-42, U.S. EPA, 1998. op.cit. p. 2.4 - 6.
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                                             M S W  Landfill  Sources    Guidance
               collection system efficiencies for passive vent-
               ing systems and each emission estimation
               using passive systems, and the recovery effi-
               ciency applied, are evaluated on a site specific
               basis. Effectiveness of passive venting is
               generally determined by monitoring methane
               concentrations in perimeter soils and at
               building or structure foundations.

               Another factor to be considered for both
               methods of estimating emissions is for
               methane oxidized as a result of methane oxi-
               dizing bacteria found within the landfill cover
               system,  intermediate soils and alternative daily
               cover systems. Studies have been conducted
               which support methane oxidation, however the
               rates can vary substantially based on the final
               cover composition, thickness and seasonal
               variations8. Average oxidation of methane (on
               a volumetric basis) in some laboratory and
               case studies on landfill covers have indicated
               ranges from 10 percent to over 25 percent
               with the lower portion of the range being
               found in clay soils and higher in topsoils9.
               A conservative approach is an assumption
               that 10/6 of the non-captured landfill methane
               passing through the final cover system or soils
               may potentially be oxidized. Methane oxidation
               factors can be much higher for intermediate
               cover materials such  as compost applications.

               Due to the uncertainty involved and the lack of
               a standard method to determine oxidation rate,
               EPA recommends the default factor of  10/6 by
               volume methane oxidation for landfills with
               low permeability cover systems. Landfill cover
                                                      systems incorporating a flexible membrane
                                                      liner (FML) within the final cover system have
                                                      negligible methane oxidation and the default
                                                      oxidation rate for these types of covers is
                                                      equal to zero.

                                                      Use of the methane generation method of cal-
                                                      culating emissions requires use of a first order
                                                      decay model, which is  the basis of the U.S. EPA
                                                      LandGEM computer software. The model has
                                                      input parameters used to represent character-
                                                      istics of the waste as described in Section 2.1.
                                                      The variables k and L0 that determine the rate
                                                      of gas production are functions of site-specific
                                                      conditions. A set of default values for k and L0
                                                      are listed in the U.S. EPA's Compilation of Air
                                                      Pollutant Emission Factors, Document No. AP-
                                                      42, (1998)10. The L0 factor is a function of the
                                                      waste composition and a single default is
                                                      provided for typical municipal solid waste.

                                                      The k factor is a rate constant that is a func-
                                                      tion primarily of the refuse moisture content.
                                                      Two  default values are listed for this factor,
                                                      one for arid regions (less than 635 mm or 25
                                                      inches of precipitation per year) and another
                                                      for non-arid regions. The AP-42 default values
                                                      are listed below.

                                                      Parameter    AP-42 Default Value
                                                        L0           100 m3/t
                                                        k             0.04/yr (non-arid area)
                                                                      0.02/yr (arid area)
               8  "Quantifying the Effect of Oxidation on Landfill Methane Emissions". P. Czepiel, B. Mosher, P.M. Crill, and R.C. Harriss. 1996. Journal
                 of Geophysical Research, Volume 101: 16712-16729.

               9  "Isotopic signatures of atmospheric methane at NIGEC tower sites and of anthropogenic sources of methane to the atmosphere ".
                 Annual Progress Report for FY 97/98, National Institute of Global Environmental Change.

               10 Compilation of Air Pollutant Emission Factors, AP-42, 5th Edition, Volume 1: Stationary Point and Area Sources Chapter 2: Solid
                 Waste Disposal, Section 2.4, U.S. EPA Supplement E, November 1998. p. 2.4 - 4.
1 4
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       M S W  Landfill  Sources    Guidance

These default parameters are based on
average moisture conditions and generally
reflect "dry-tomb" style landfill applications for
various  climates. For "bioreactor" type landfills
the methane generation rate constant is gener-
ally high due to the amount of moisture added
to the waste, resulting in a higher production
rate of LFG over a shorter interval of time. Gas
generation rates for bioreactor type landfills
are generally in the order of two to three times
that of dry tomb landfill operations.

It is suggested that Climate Leaders Partners
having MSW landfill sites without gas collec-
tion systems use the LandGEM computer
model (LandGEM Version 2.01) with AP-42
default factors or site specific determined
values for parameters L0 and k. LandGEM 2.01
can be obtained through the U.S. EPA's
Technology Transfer Network (TIN) at:

       http://www.epa.gov/ttn/catc/
       products. html#software

Partners who are landfill owners may have
collected data to establish site-specific values
of k and L0 for this widely used model of land-
fill gas emissions. These values may be used if
they were derived using methods approved by
U.S. EPA for this purpose. Partners should
make available the data, data collection proce-
dures, and calculations they used in deriving
these site-specific factors for verification if
they are used for estimating landfill methane
emissions.
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                                          M S W  Landfill  Sources   Guidance
              Completeness

                  In order for a Partner's GHG corporate
                  inventory to be complete it must include
                  all emission sources within the company's
              chosen inventory boundaries. See Chapter 3 of
              the Climate Leaders Design Principles for
              detailed guidance on setting organizational
              boundaries and Chapter 4 of the Climate
              Leaders Design Principles for detailed guidance
              on setting operational boundaries of the corpo-
              rate inventory.

              On an organizational level the inventory should
              include emissions from all applicable facilities.
              Completeness of corporate wide emissions
              can  be checked by comparing the list of
              facilities included in the GHG emissions
              inventory with those included in other
              emission's inventories/environmental report-
              ing,  financial reporting, etc.

              At the operational level, a Partner should
              include all emission sources from the facilities
              included in their corporate inventory. For a
              Partner who's operations include MSW landfill-
              ing,  possible emissions sources are stationary
              fuel combustion, combustion of fuels in mobile
              sources, purchases of electricity,  HFC emis-
              sions from air conditioning equipment and
              methane emissions from MSW decomposition.
              Partners should refer to this guidance docu-
              ment for calculating methane emissions from
              MSW decomposition and to the Climate
              Leaders Core Guidance documents for calculat-
              ing emissions from other sources.
                                                  Partners should be aware when using this guid-
                                                  ance that any losses in methane collected
                                                  based on fugitive emissions through piping sys-
                                                  tems should be accounted for. Landfill gas
                                                  could be lost due to fugitive releases of LFG
                                                  from collection system valves and piping as
                                                  well as through the leachate collection system
                                                  (LCS). It should be noted that the leachate col-
                                                  lection system can be a significant pathway for
                                                  landfill methane emissions. Generally most LFG
                                                  collection systems installed incorporate provi-
                                                  sions for recovery of gas from the LCS piping
                                                  and storage network.

                                                  As described in Chapter 1 of the Climate
                                                  Leaders Design Principles, there is no materiali-
                                                  ty threshold set for reporting emissions. The
                                                  materiality  of a source can  only be established
                                                  after it has  been assessed. This does not nec-
                                                  essarily require a rigorous quantification of all
                                                  sources, but at a minimum, an estimate based
                                                  on available data should be developed for all
                                                  sources.

                                                  The inventory should also accurately reflect
                                                  the timeframe of the report. In the case of
                                                  Climate Leaders, the emissions inventory is
                                                  reported annually and should represent a full
                                                  year of emissions data.
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      M S W  Landfill  Sources    Guidance

Uncertainty  Assessment
        Uncertainties in estimating methane
        emissions from MSW landfill sites
        without gas collection systems is
high based on the fact the landfill is not a
homogeneous mass of waste deposited under
fully controlled conditions.

The emission estimates using the first-order
decay equation with standard default factors
could have a +/- error of 200% or more depend-
ing on actual site conditions11. There is always
a level of uncertainty in the accuracy of meas-
urements or estimates of the annual landfilled
waste mass, including the variability in the
waste composition. A very important factor
in modeling landfill gas emissions is the under-
lying assumption that the waste composition is
typical (which is generally not the case).

Gas generation and subsequent emission of
that gas  to the atmosphere is based on many
factors as discussed throughout this docu-
ment. Also, the first-order decay equation
does not take into account a lag period from
initial placement of waste and assumes gas
generation commences within the first year of
waste placement. Experience with gas collec-
tion from landfills in arid locations shows that
they can exhibit extremely long lag times from
the initial placement of waste until the onset of
significant anaerobic gas production.

Uncertainties associated with estimating land-
fill methane emissions are lessened using
recovery data available from MSW landfills
incorporating a gas collection system.
Assuming that a properly designed gas
recovery system falls in a typical range for gas
collection system efficiency, the confidence
level is higher when back calculating the
landfill methane emissions using default or site
specific gas collection system efficiencies then
the confidence level obtained using the first-
order  decay equation.

The area of methane oxidation is not fully
defined and even using a 10 percent methane
oxidation factor can lead to uncertainty in
annual emission estimations calculated and
subsequently reported.
11 Ibid, p. 2.4-4.
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                                           M S W  Landfill  Sources    Guidance
              Reporting  and   Documentation
                     Partners are required to complete the
                     Climate Leaders Reporting Requirements
                     and report annual emissions. In order
              to ensure that emissions  estimates are
              transparent and verifiable, the input data
              used to develop the emission estimates should
              be clearly documented and all sources listed in
                                                   Table 1 should be maintained for each
                                                   relevant year. These documentation sources
                                                   should be collected to ensure the accuracy
                                                   and transparency of the related emissions data,
                                                   and should also be reported in the Partner's
                                                   Inventory Management Plan (IMP).
              Data
                       Table 1:   Documentation  Sources for
                     Solid Waste Landfill  Methane Emissions

                                                Documentation Source
              Total permitted landfill capacity
                                                Operating Certificate or Permit
              Year opened
                                                Landfill site records
              Year of closure
                                                Operating Certificate or Permit, site records
              Current area devoted to landfilling
                                                Current contour maps and filling plans
              Annual landfill acceptance rate for the site
              Tonnage figures including waste in place
                                                Weigh scale records, volumetric calculations,
                                                aerial photographs, and landfill annual reports
              MSW composition (% MSW, other organic
              wastes, C&D, Fill)
                                                Waste categorization based on weigh scale
                                                records including reused and recycled material
                                                broken down by percent, mass or volume.
              Average Waste moisture content
                                                Waste records, climate data
              Average Waste Depth
                                                Up-to-date contour map, site records.
              Meteorological data, primarily precipitation
                                                Local weather authority or on-site meteorological
                                                station
              LFG flow rate and composition
                                                Site testing, Gas collection monitoring system,
                                                flow meter, in-line chromatograph or gas analyzer,
                                                third party laboratory analysis
              Landfill area covered by gas collection system     LFG system record drawings
              Emission factors and default input methane
              emission model parameters
                                                All applicable sources, U.S. EPA with programs such as
                                                the Landfill Methane Outreach Program (LMOP), also
                                                SWANA technical documents
              Landfill gas captured, flared and/or utilized
                                                Gas collection monitoring system, flow meter, in-line
                                                chromatograph or gas analyzer, third party laboratory
                                                analysis
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      M S W  Landfill  Sources    Guidance

Inventory
Quality  Control
Assurance  and
       Chapter 7 of the Climate Leaders Design
       Principles provides general guidelines
       for implementing a QA/QC process for
all emission estimates. For MSW landfill
sources, a review of input data and emission
factors should be verified for various
approaches, specifically if customized defaults
were developed based on site specific data.
QA/QC may include, but not limited to:

  Landfill methane emissions calculated using
   Landfill Gas Emission Model compared with
   emissions calculated using proprietary gas
   generation models developed by industry
   experts or other agencies.

  Landfill methane emissions calculated by
   gas collection system efficiency in compari-
   son to emissions estimated through gas
   modeling.
Examining the quality assurance and quality
control program associated with equipment
used for facility level LFG flow rate and
composition measurements and any equip-
ment used to calculate site-specific
emissions factors, or emissions.

Performing back-checks and re-calculations
for all equations used.

Landfill gas sampling and third-party labora-
tory analysis using the applicable U.S. EPA
test methods for determination of methane
and total hydrocarbon content.

Ensuring that measuring and monitoring
equipment is maintained, operated and
calibrated based on manufacturer's  recom-
mendation and calibration and maintenance
records kept for audit purposes.
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                                 M S W  Landfill  Sources   Guidance
           LandGEM  Sample Output

           The following is a sample text emission output report generated using LandGEM Version 2.01
           and based on the example and model input parameters in Section 2.1.
LandGEM 2.01 Text Report
Source: Operating Parameters: ALANDFILLOOO
Model Parameters
Lo : 100.00 mA3/Mg ***** User Mode Selection *****
k : 0.0200 1/yr ***** User Mode Selection *****
NMOC : 4000.00 ppmv ***** User Mode Selection *****
Methane : 50.0000 % volume
Carbon Dioxide : 50.0000 % volume
Landfill
Parameters





Landfill type : No Co-Disposal
Year Opened : 1982 Current Year : 2003 Closure Year: 2012
Capacity : 2400000 Mg
Average Acceptance Rate Required from Current Year to Closure Year : 80000.00 Mg/year
Model Results
Year
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
Refuse In
Place (Mg)
8.000E+04
1.600E+05
2.400E+05
3.200E+05
4.000E+05
4.800E+05
5.600E+05
6.400E+05
7.200E+05
8.000E+05
8.800E+05
Methane Emission Rate
(Mg/yr)
1.067E+02
2.114E+02
3.139E+02
4.145E+02
5.130E+02
6.096E+02
7.043E+02
7.971E+02
8.880E+02
9.772E+02
1.065E+03
(Cubic m/yr)
1.600E+05
3.168E+05
4.706E+05
6.212E+05
7.689E+05
9.137E+05
1.056E+06
1.195E+06
1.331E+06
1.465E+06
1.596E+06
Methane Emission Rate
Year
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003

Refuse In
Place (Mg)
9.600E+05
1.040E+06
1.120E+06
1.200E+06
1.280E+06
1.360E+06
1.440E+06
1.520E+06
1.600E+06
1.680E+06

(Mg/yr)
1.150E+03
1.234E+03
1.317E+03
1.397E+03
1.476E+03
1.554E+03
1.630E+03
1.704E+03
1.777E+03
1.849E+03

(Cubic m/yr)
1.724E+06
1.850E+06
1.973E+06
2.094E+06
2.213E+06
2.329E+06
2.443E+06
2.554E+06
2.664E+06
2.771E+06

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&EPA
     United States
     Environmental Protection
     Agency

     Office of Air and Radiation (6202J)
     EPA430-K-04-011
     October 2004
     www.epa.gov/climateleaders

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