February 4, 2009
TECHNICAL SUPPORT DOCUMENT
FOR THE LANDFILL SECTOR:
PROPOSED RULE FOR
MANDATORY REPORTING OF
GREENHOUSE GASES
Office of Air and Radiation
U.S. Environmental Protection Agency
February 4, 2009
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CONTENTS
1. Industry Description 3
2. Total Emissions 4
3. Review of Existing Programs and Methodologies 4
4. Types of Emissions Information to be Reported 5
4.1 Types of Emissions to be Reported 5
4.2 Other Information to be Reported 5
5. Options for Reporting Threshold 6
5.1 Emissions-based thresholds 6
5.2 Other threshold options 8
6. Options for Monitoring Methods 9
6.1 Calculating Methane Generation using the First-order Decay (FOD) Model 9
6.2 Monitoring Methane Combustion at Flares or Energy Projects 11
6.3 Calculating Generation and Emissions using the IPCC Model 11
6.4 Calculating Generation and Emissions using Gas Collection Data and Collection
Efficiency 12
6.5 Monitoring Landfill Emissions from the Landfill Surface 13
7. Options for Estimating Missing Data 13
8. QA/QC Requirements 14
9. References 15
Appendix A. Assumptions Used in Landfill Threshold Analysis 16
A.1 Municipal Solid Waste (MSW) Landfills 16
A.2 Industrial Waste Landfills 18
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1. Industry Description
The New Source Performance Standard (NSPS) for municipal solid waste (MSW) landfills (40
CFR 60 subpart WWW) includes the following definition for landfills:
"Landfill means an area of land or an excavation in which wastes are placed for
permanent disposal, and that is not a land application unit, surface impoundment,
injection well, or waste pile as those terms are defined under §257.2 of this title."
(Note: 40 CFR 257 is the Criteria for Classification of Solid Waste Disposal
Facilities and Practices)
The landfill NSPS also includes the following definition for MSW landfills:
"Municipal solid waste landfill or MSW landfill means an entire disposal facility
in a contiguous geographical space where household waste is placed in or on land.
An MSW landfill may also receive other types of RCRA Subtitle D wastes
(§257.2 of this title) such as commercial solid waste, nonhazardous sludge,
conditionally exempt small quantity generator waste, and industrial solid waste.
Portions of an MSW landfill may be separated by access roads. An MSW landfill
may be publicly or privately owned. An MSW landfill may be a new MSW
landfill, an existing MSW landfill, or a lateral expansion."
After being placed in a landfill, waste is initially decomposed by aerobic bacteria. After the
oxygen has been depleted, the remaining waste is available for consumption by anaerobic
bacteria, which break down organic matter into substances such as cellulose, amino acids, and
sugars. These substances are further broken down through fermentation into gases and short-
chain organic compounds that form the substrates for the growth of methanogenic bacteria.
These CH/t-producing anaerobic bacteria convert the fermentation products into stabilized
organic materials and biogas.
Methane generation from a given landfill is a function of several factors, including: (1) the total
amount of waste disposed of in the landfill each year (annual waste acceptance rate); (2) the age
of the landfill (or the total quantity of waste in-place); (3) the characteristics of the waste (i.e.,
composition and organic content of waste); and (4) the climatic conditions (temperature and soil
moisture content - wet soils promote anaerobic degradation). The amount of methane emitted is
dependent on the amount of CH4 generated less the amount of CH4 that is recovered (and either
flared or used for energy purposes); and the amount of CFL; oxidized near the landfill surface
prior to being released into the atmosphere.
There are two important federal standards that require MSW landfills to capture and control
landfill gas: the NSPS for MSW Landfills (40 CFR 60 subpart WWW) and the Emission
Guidelines for MSW Landfills (40 CFR 60 subpart Cc). The landfill NSPS requires landfills
that have a design capacity of 2.5-million cubic meters or greater and 2.5-million megagrams
(Mg) or greater and that commenced construction, reconstruction, or modification on or after
May 30, 1991, to capture and control the landfill gas if the non-methane organic compound
(NMOC) emissions exceed 50 Mg per year (Mg/yr). The Emission Guidelines are applicable to
landfills that commenced construction, reconstruction, or modification prior to May 30, 1991,
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but that received waste (or have remaining capacity to receive waste) after November 8, 1987.
The Emission Guidelines, like the NSPS, requires applicable landfills that have a design capacity
of 2.5-million cubic meters or greater and 2.5-million Mg to capture and control the landfill gas
if the non-methane organic compound (NMOC) emissions exceed 50 Mg per year (Mg/yr).
While these two standards focus on NMOC, they effectively require capture and control of
landfill-generated methane.
In addition to these two standards, the EPA has promoted the beneficial use of landfill gas for
energy (electricity or heat) production through its voluntary Landfill Methane Outreach Program.
This program helps to identify and promote cost-effective landfill gas-to-energy (LFGTE)
projects.
2. Total Emissions
There were approximately 7,800 active MSW landfills in the United States in 1988; in 2004, the
number of active MSW landfills had dropped to about 1,600 (Simmons, et al, 2006). MSW
landfills emitted 111.2 million metric tons of carbon dioxide equivalent (mmtCO2e) in 2006.
Generation of methane at these landfills was 246.8 mmtCO2e; however, 65.3 mmtCO2e was
recovered and used in energy projects, 59.8 mmtCO2e was reduced by flaring, and 12.4
mmtCO2e was oxidized in cover soils (U.S. EPA, 2008b). Based on the decrease in the number
of landfills reported over the past 16 years, it is estimated that there are approximately 6,200
closed MSW landfills in the U.S. that have been closed less than 20 years. Data on these
landfills were unavailable at the time of this analysis.
The majority of the CH4 emissions from on-site industrial landfills occur at pulp and paper
facilities and food processing facilities. In 2006, these landfills emitted 14.6 mmtCO2e.
Approximately 180 pulp and paper facilities have on-site landfills. These landfills emitted 7.3
mmtCO2e in 2006. Approximately 189 food processing facilities have on-site landfills. These
landfills emitted 7.2 mmtCO2e in 2006.
3. Review of Existing Programs and Methodologies
In developing GHG monitoring and reporting options for landfills, a number of existing
programs and guideline methodologies were reviewed. In addition to the NSPS and Emission
Guidelines for MSW landfills, the following resources were examined:
1. 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National
Greenhouse Gas Inventories. Volume 5, Waste.
2. U.S. Department of Energy (DOE). 2007. Technical Guidelines: Voluntary Reporting Of
Greenhouse Gases (1605(B)) Program.
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3. CARB (California Air Resource Board). 2008. Regulation For The Mandatory
Reporting of Greenhouse Gas Emissions: Second 15-Day Modified Regulatory
Language For Public Comment. May 15.
4. Environment Canada (2006). Guidance Manual for Estimating Greenhouse Gas
Emissions, http://www.ghgreporting.gc.ca/GHGInfo/Pages/page 15.aspx?lang=E.
Additional programs and methodological guidance reviewed included: U.S. GHG Inventory,
California Climate Action Registry, EPA Climate Leaders, EU Emissions Trading System, The
Climate Registry, EPA's Landfill Methane Outreach Program, Australia's National Mandatory
GHG Reporting Program (draft), NSPS/NESHAP, and the WRI/WBCSD GHG Protocols.
Each of these sources was reviewed to determine the types of emissions to be reported, the
facility reporting thresholds, and the monitoring methodologies recommended. The reporting
and monitoring options presented in Sections 4, 5, and 6 are commensurate with the
methodologies used in these existing programs and guidelines.
4. Types of Emissions Information to be Reported
4.1 Types of Emissions to be Reported
Based on the review of existing programs and the emission sources at landfills, GHG reporting
for landfills is limited to CfL; because the CC>2 produced from the landfills is considered
biogenic. There are potentially other sources of GHG emissions at facilities that operate
landfills. For reporting options for stationary combustion (including landfill gas combustion for
energy and combustion of fossil fuels used to assist gas combustion efficiency), refer to EPA-
HQ-OAR-2008-0508-004. Biogenic emissions of CC>2 from flaring without energy recovery are
not reported.
In the case of industrial facilities with onsite landfills, industrial process emissions of greenhouse
gases may be occurring onsite as well. Reporting options for landfill emissions are detailed here,
but for reporting options for other sources of industrial process emissions, refer to sections for
that industry in the respective Background Technical Support Documents.
4.2 Other Information to be Reported
In order to check the reported GHG emissions for reasonableness and for other data quality
considerations, additional information about the emission sources is needed. It is recommended
that, in addition to methane emissions, each reporting landfill should also report methane
generation and, if applicable, methane combustion annual quantities. Additionally, it is
recommended that the following data also be submitted with the annual report:
Data to report—all landfills
a. Waste disposal for each year of landfilling
b. Method for estimating waste disposal
c. Waste composition, if available
d. Method for estimating waste composition
e. Fraction of CfL; in landfill gas (most will use IPCC default)
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f. Oxidation rate (most will use IPCC default)
g. Degradable organic carbon (DOC) (most will use inventory default)
h. Decay rate (most will use inventory default)
i. Fraction of DOC dissimilated (most will use IPCC default)
j. MCF used (most will use IPCC
k. Methane generation using FOD method
1. Methane emissions using FOD method (and deducting methane recovery)
m. Landfill design capacity
n. Estimated year of landfill closure
o. Cover system description
p. Acreage and quantity of waste covered by intermediate cap
q. Acreage and quantity of waste covered by final cap
Additional data to report—landfills with gas collection systems
a. Total volumetric flow
b. CH4 concentration
c. Temperature at which flow is measured
d. Pressure at which flow is measured
e. Destruction efficiency used
f. Methane destruction
g. Estimated gas collection system efficiency
h. Methodology for estimating gas collection system efficiency for landfills with gas
collection systems
i. Number of wells in gas collection system
j. Methane generation using recovery data
k. Methane emissions using recovery data
5. Options for Reporting Threshold
5.1 Emissions-based thresholds
Data were collected and analyzed to evaluate several potential reporting thresholds. The primary
options were based on the CH4 generation at a landfill minus oxidation ("generation threshold")
and CH4 emissions from a landfill, minus oxidation after any destruction of landfill gas at a
combustion device ("emissions threshold"). The generation threshold refers to the methane
generated at the landfill, minus oxidation in landfill cover soils that are expected to occur in the
absence of a landfill gas collection system. The emissions threshold refers to the methane that is
actually emitted to the atmosphere from these landfills taking into account recovered methane
combustion and methane oxidation at the landfill surface. Emissions-based thresholds evaluated
were:
i. An emissions threshold of 1,000 mtCO2e
ii. An emissions threshold of 10,000 mtCO2e
iii. An emissions threshold of 25,000 mtCO2e
iv. An emissions threshold of or 100,000 mtCO2e
v. A generation threshold of 1,000 mtCO2e
vi. A generation threshold of 10,000 mtCO2e
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vii. A generation threshold of 25,000 mtCC^e
viii. A generation threshold of 100,000 mtCC^e
In addition to these emissions-based thresholds, landfills were also categorized as active MSW
landfills, closed MSW landfills, and industrial landfills. The emissions based thresholds were
evaluated for each of these classes of landfills and certain combinations of these classes; the
results of this analysis are presented in Table 1.
Table 1. Summary of Threshold Analysis for Landfills
Source
Category
"Active" MSW
Landfills
Closed MSW
Landfills
Industrial
Landfills, Pulp
and Paper
Industrial
Landfills, Food
Processing
Threshold Level
> 1,000 mtCO2e (generation)
> 1,000 mtCO2e (emissions)
>10,000 mtCO2e (generation)
>10,000 mtCO2e (emissions)
>25,000 mtCO2e (generation)
>25,000 mtCO2e (emissions)
>100,000 mtCO2e (generation)
>100,000 mtCO2e (emissions)
> 1,000 mtCO2e (generation)
> 1,000 mtCO2e (emissions)
>10,000 mtCO2e (generation)
>10,000 mtCO2e (emissions)
>25,000 mtCO2e (generation)
>25,000 mtCO2e (emissions)
>100,000 mtCO2e (generation)
>100,000 mtCO2e (emissions)
> 1,000 mtCO2e (generation)
> 1,000 mtCO2e (emissions)
>10,000 mtCO2e (generation)
>10,000 mtCO2e (emissions)
>25,000 mtCO2e (generation)
>25,000 mtCO2e (emissions)
>100,000 mtCO2e (generation)
>100,000 mtCO2e (emissions)
> 1,000 mtCO2e (generation)
> 1,000 mtCO2e (emissions)
>10,000 mtCO2e (generation)
>10,000 mtCO2e (emissions)
>25,000 mtCO2e (generation)
>25,000 mtCO2e (emissions)
>100,000 mtCO2e (generation)
>100,000 mtCO2e (emissions)
Facilities Covered
Number
1560
1557
1314
1200
1001
686
418
131
5270
5270
2170
1860
1550
1240
620
310
180
180
170
170
100
100
10
10
189
189
170
170
100
100
10
10
Percent
98
97
82
75
63
43
26
8
85
85
35
30
25
20
10
5
100
100
94
94
56
56
6
6
100
100
90
90
53
53
5
5
Emissions Covered
MMTCO2e/year
57.3
57.3
54.0
53.2
47.2
42.6
34.0
20.3
53.4
53.4
50.4
49.6
44.0
39.8
31.7
18.9
7.3
7.3
7.0
7.0
5.0
5.0
1.5
1.5
7.2
7.2
7.0
7.0
5.0
5.0
1.5
1.5
Percent
99.7
99.7
94
93
82
74
59
35
99.6
99.6
94
93
82
74
59
35
100
100
96
96
68
68
21
21
100
100
97
97
69
69
21
21
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Source
Category
Total All
MSW
Landfills
Total All
MSW and
Industrial
Landfills
Threshold Level
> 1,000 mtCO2e (generation)
> 1,000 mtCO2e (emissions)
>10,000 mtCO2e (generation)
>10,000 mtCO2e (emissions)
>25,000 mtCO2e (generation)
>25,000 mtCO2e (emissions)
>100,000 mtCO2e (generation)
>100,000 mtCO2e (emissions)
> 1,000 mtCO2e (generation)
> 1,000 mtCO2e (emissions)
>10,000 mtCO2e (generation)
>10,000 mtCO2e (emissions)
>25,000 mtCO2e (generation)
>25,000 mtCO2e (emissions)
>100,000 mtCO2e (generation)
>100,000 mtCO2e (emissions)
Facilities Covered
Number
6,830
6,827
3,484
3,060
2,551
1,926
1,038
441
7199
7196
3824
3400
2751
2126
1058
461
Percent
88
88
45
39
33
25
13
6
88
88
47
42
34
26
13
6
Emissions Covered
MMTCO2e/year
110.7
110.7
104.4
102.8
91.1
82.4
65.6
39.2
125.2
125.2
118.4
116.8
101.1
92.4
68.6
42.2
Percent
100
100
94
93
82
74
59
35
100
100
94
93
81
74
55
34
5.2 Other threshold options
In addition to these general landfill classes, other specific reporting thresholds were evaluated.
For example, reporting of only NSPS landfills was considered, but this would only result in the
reporting of 36% of the emissions from the landfill sector. Reporting of only landfills that do not
have landfill gas collection systems would require reporting from approximately 6,900 landfills
many of which have very small emissions and would still exclude a significant fraction of the
landfill sector emissions. Excluding closed landfills would mean that 48% of emissions from all
landfills in the United States would not be reported. Consequently, none of these options were
considered further as part of the reporting threshold.
Commensurate with other reporting programs, a generation threshold of 25,000 mtCC^e per year
is recommended. The emissions threshold would exclude reporting from large facilities with gas
collection systems. A generation threshold level of 1,000 or 10,000 mtCC^e increases the
number of reporters by several thousand and this level would likely capture numerous small
landfills that only contribute 5 to 10 percent of the nationwide CFLt emissions. An emissions
threshold level of 100,000 mtCC^e would require reporting by far fewer landfills, but capture
only about 50 percent of emissions from this source.
At the recommended reporting threshold, it is estimated that 1001 active MSW landfills would
report. This would represent around 63% of active MSW landfills, but 82% of methane emitted
from active MSW landfills. Data are not available to calculate the amount of methane emitted
from specific closed landfills, but it is estimated that approximately 1,550 (or approximately 25
percent of) closed landfills would need to report at this threshold and that approximately 82
percent the methane emissions from closed landfills would be included. Overall, approximately
2,551 MSW landfills would report and these facilities would include 91.1 MMTCC^e or
82 percent of the total U.S. CFLt emissions from MSW landfills (see Table 2).
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For industrial landfills, at a generation threshold of 25,000 mtCC^e per year, it is estimated that
approximately 100 landfills at pulp and paper facilities (56% of such landfills) and 100 landfills
at food processing facilities (53% of such landfills) would report emissions. As seen in Table 2,
it is estimated that approximately 68 percent of CFLt emissions from pulp and paper landfills and
69 percent of CFL; emissions from food processing landfills would be accounted for at the
recommended reporting threshold. Data were not available for landfills that may occur at other
industrial facilities (e.g., petroleum refineries).
Table 2. Estimated Number of Facilities Reporting and Emissions Reported at the
Recommended Reporting Threshold
Operation
MSW Landfills
Pulp and Paper on-
site Landfills
Food Processing
onsite landfills
Estimated
Number
Facilities
Reporting
2551
100
100
Percent of All
Facilities of this
Type of
Operation
33
56
53
Emissions
(mtCO2e )
91.1
5.0
5.0
Percent of
All Emissions
from this
Type of
Operation
82
68
69
6. Options for Monitoring Methods
There are three potential monitoring methods: (1) calculation of methane generation using the
IPCC waste model for landfills that do not have landfill gas collection systems; (2) use of gas
flow and composition metering for landfills that have gas collection systems, in addition to
calculating methane generation with the IPCC waste model; and (3) direct emission
measurements from the landfill surface. Direct surface emission measurement techniques are
expensive, they typically provide only short-term measures of emissions, and they often suffer
from high uncertainty.
6.1 Calculating Methane Generation using the First-order Decay (FOD) Model
The 2006 IPCC Guidelines' Waste Model produces emissions estimates that reflect the
degradation rate of wastes in a landfill (IPCC, 2006). To assist in developing CH4 emission
estimates for solid waste disposal sites (SWDS), the IPCC developed the Waste Model and
improved default values for thee organic content and degradation rate constants for different
types of waste materials. The basic FOD equation for the methane generation rate in the IPCC
Waste Model using the "bulk waste" option and a time delay of 6 months is presented below (see
Equation 1). This is the simplest calculation performed by the model.
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x=S
Equation 1.
A = CH4 GenerationT (Mg/ yr) =
where,
x = the year in which waste was disposed;
S = the start year of inventory calculation;
T= the inventory year for which emissions are calculated;
Wx = the quantity of waste disposed at SWDS (metric tons);
Lo = CH4 generation potential = MCF • DOC • DOCF • F • 16 /12 (Mg CH4/Mg waste);
MCF = methane correction factor (fraction);
DOC = degradable organic carbon [fraction (Mg C/Mg MSW)];
DOCp = fraction of DOC dissimilated (fraction);
F = fraction by volume of CH4 in landfill gas; and
k = reaction rate constant (yr"1).
The model includes the delay time (in months) for CH4 generation as an input parameter to the
model, and adjusts the emission inventory calculations accordingly.
The model also provides an option in which CH4 generation can be estimated for different types
of waste materials (wood, food, garden, paper, textiles, etc.) by repeating the above calculation
for each type of waste. This approach requires waste-specific disposal quantities and values of
DOC and k by waste type; the IPCC Guidelines provides default values for DOC and k by waste
type.
To accurately estimate emissions using this method, waste disposal data are needed for the 50
year period prior to the year of the emissions estimate.
Annual waste disposal data are to be estimated using receipts for disposal where available and
extrapolation for years where these data are not available.
For years where waste composition data are available, emissions are estimated using waste
composition. When waste composition data are unavailable, composition estimates are to be
developed by extrapolating/interpolating with available waste composition data, by using
regional composition data (as available) or by using bulk waste values developed for the United
States.
The model will calculate emissions using the appropriate values for DOC, DOCp, and k based on
the waste composition entered. The selection of appropriate k values should also consider
regional rainfall amounts.
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6.2 Monitoring Methane Combustion at Flares or Energy Projects
Direct measurement for methane combustion methods depend on two measurable parameters:
1) the rate of gas flow to the combustion device; and 2) the CH4 content in the gas flow. These
can be quantified by directly measuring the gas stream to the destruction device(s).
Continuous Metering. The instrumentation recommended for continuous measurement measures
both flow and gas concentration. Several direct measurement instruments also use a separate
recorder to store and document the data. A fully integrated system that directly reports CH4
content requires no other calculation than summing the results of all monitoring periods for a
given year. Internally, the instrumentation is performing its calculations using algorithms
similar to the equation below.
Monthly Sampling. The two primary instruments used in the monthly monitoring method are a
gas flow meter and a gas composition meter. The gas flow meter must be installed as close to the
landfill gas combustion device as possible to measure the amount of gas reaching the device.
Two procedures are used for data collection in the monthly monitoring method:
1. Calibrate monitoring instrument in accordance with the manufacturer's specifications.
2. Collect four sets of data: flow rate (scfm); CH4 concentration (%); temperature (°R);
and pressure (atm) from the inlet landfill gas (before any treatment equipment using a
monitoring meter specifically for CH4 gas.)
The amount of CH4 destroyed during the year is calculated using Equation 2. This equation can
be used for either monthly sampling or for continuous monitoring systems that are not integrated.
Equation 2.
0.0423 x^ *(— 1
oo% (Tn j (i j uooojf
Where:
R = quantity of recovered CH4 (Mg/yr)
Vn = average volumetric flow rate over time period n (acfm)
Concn = average CH4 concentration in gas flow over time period n (in %)
0.0423 = Ib. CH4/scf (at 520°R or 60°F and 1 atm)
Tn = average temperature at which flow is measured over time period n (°R)
Pn = average pressure at which flow is measured over time period n (atm)
tn = Time period since last measurement (min)
0.454/1000 = Conversion factor (Mg/lb)
6.3 Calculating Generation and Emissions using the IPCC Model
Generation, adjusted for oxidation, is calculated from the methane generation rate and the
assumed oxidation factor according to Equation 3 .
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Equation 3.
Adjusted Generation = A x (1 - OX)
Where:
OX = oxidation, default rate is 0.1 (10%)
For landfills with gas collections systems, the emissions are reduced by the amount of gas
recovered while considering the destruction efficiency of the control system. Emissions are
calculated using Equation 4. Equation 4 reduces to Equation 3 when R = 0. That is, for landfills
that do not have gas collection systems, the emissions calculated are equal to the adjusted
generation.
Equation 4.
Emissions = (A - R) x (1 - OX) + R x (1 - DE)
Where:
DE = destruction efficiency, default rate is 0.99
OX = oxidation, default rate is 0.1 (10%)
6.4 Calculating Generation and Emissions using Gas Collection Data and Collection
Efficiency
For landfills with gas collection systems, an alternative method for estimating the methane
generation rate and subsequently the adjusted generation and emissions is to use the gas
collection data and estimated gas collection system efficiency. The methane generation rate
estimated from gas collection data is the quantity of methane recovered divided by the collection
efficiency (CE) of the landfill gas collection system (A = R/CE). Substituting for this expression
for A in Equations 3 and 4 yield equations for the adjusted generation and emissions as
calculated using the gas collection data and estimated gas collection system efficiency, which are
provided here as Equations 5 and 6, respectively.
Equation 5.
Adjusted generation = R/CEx(l - OX)
Where:
OX = oxidation, default rate is 0.1 (10%)
CE = collection efficiency, estimated at landfill
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Equation 6.
Emissions = [R x (1/CE - 1)] x (1 - OX) + R x (1-DE)
Where:
OX = oxidation, default rate is 0.1 (10%)
CE = collection efficiency, estimated at landfill
6.5 Monitoring Landfill Emissions from the Landfill Surface
A variety of measurement techniques have been used to measure the flux of methane gas at the
surface of the landfill. One commonly used approach is flux chamber measurements. A flux
chamber is a small enclosure used to collect gas as it is released from the surface of the landfill.
The flux chamber covers a small area of the landfill and the methane concentration and quantity
of gas collected and swept from the chamber is measured to calculate a flux of methane per area
of the landfill. Difficulties associated with flux chamber measurements include the limited time
and area over which measurements can be made. The surface of the landfill is not perfectly
homogeneous and landfill gas will be released at different rates at different areas across the
landfill. A significant fraction of the landfill gas releases may be focused in very limited areas
where larger fissures in the surface soil exist. As such, it is difficult to get representative
measurements across the entire landfill area. Additionally, flux chamber measurements are
generally short-term tests. Variations in short-term emissions may occur due to barometric
pumping, unusually dry or wet weather, etc. Consequently, there is significant uncertainty
associated with a short-term, one-time test.
Open-Path Fourier Transform Infrared Spectroscopy (OP-FTIR) systems have also been used to
measure emissions from large area sources such as landfills. OP-FTIR systems use multiple
beams to determine vertical and horizontal gradients. Radial scanning techniques can be used to
locate potential hot spots; vertical gradient measurements are used for determining mass flux
rates. OP-FTIR monitoring requires significant capital investment and is a complicated system
to maintain and operate correctly. The accuracy of the plume flux measurements are dependent
on acceptable wind conditions. While the OP-FTIR system can more easily obtain an integrated
flux rate from a relatively large landfill area, these systems are typically used to assess emission
over a relatively short study period, and the hourly or daily measurements made during a one-
time test may not be representative of the annual average emissions.
7. Options for Estimating Missing Data
For missing waste quantity data, it is recommended that reporters use historical waste disposal
data or historical population served by the landfill and per capita waste disposal data (can be
derived from current year waste acceptance and population). For missing gas recovery data, the
average gas recovery rate measured over the previous week should be used. If gas recovery data
are missing for more than one week, gas recovery rate of zero must be used until the monitoring
system is operational. EPA considered not deducting CH4 combustion that was not recorded, but
not including CH4 recovery could greatly overestimate an entity's emissions. On the other hand,
allowing extended periods of missing data provides little incentive to repairing the monitoring
system.
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8. QA/QC Requirements
In order to ensure the quality of the reported GHG emissions, the following quality
assurance/quality control (QA/QC) activities are recommended:
(1) Reporters are to maintain annual records on waste acceptance quantities and waste
composition, and records on daily gas flow and methane content to combustion device.
(2) Reporters are to maintain records of Waste Model input values used (historical waste
disposal quantities, DOC values, k values, etc.)
(3) All fuel flow meters and gas composition monitors, and/or heating value monitors that are
used to provide data for the GHG emissions calculations should be calibrated prior to the
first reporting year, using a suitable method published by a consensus standards
organization (e.g., ASTM, ASME, API, AGA, etc.). Alternatively, calibration procedures
specified by the flow meter manufacturer may be used. Fuel flow meters and gas
composition monitors should be recalibrated either annually or at the minimum frequency
specified by the manufacturer.
(4) Documentation of the procedures used to ensure the accuracy of the estimates of fuel usage,
gas composition, and/or heating value including, but not limited to, calibration of weighing
equipment, fuel flow meters, and other measurement devices should maintained. The
estimated accuracy of measurements made with these devices should also be recorded, and
the technical basis for the estimates should be provided.
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9. References
CARB (California Air Resource Board). 2008. Regulation For The Mandatory Reporting of
Greenhouse Gas Emissions: Second 15-Day Modified Regulatory Language For Public
Comment. Available at: http://www.arb.ca.gov/regact/2007/ghg2007/ghgattachment 1.pdf.
May 15.
Environment Canada (2006). Greenhouse Gas Emissions Reporting: Technical Guidance on
Reporting Greenhouse Gas Emissions. Available at:
http ://www. ghgreporting. gc. ca/GHGInfo/Pages/page 15. aspx?lang=E.
IPCC. 2006. 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National
Greenhouse Gas Inventories. Volume 2, Energy; Chapters 2 and 4. Available at:
http://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html.
RTI International. 2005. Development of Landfill-specific Methane Inventory Model.
Memorandum from Jeff Coburn and Marvin Branscome, RTI, to Elizabeth Scheele, EPA,
dated May 6, 2005
Simmons, P., N. Goldstein, S.M. Kaufman, N.J. Themelis, and J. Thompson, Jr. 2006. "The
State of Garbage in America" Biocycle, Vol. 47, No. 4, April. Available at:
http://www.jgpress.com/archives/_free/000848.html
U.S. Department of Energy (DOE). Technical Guidelines: Voluntary Reporting Of Greenhouse
Gases (1605(B)) Program. Section I.E. 4.1.6. Iron and Steel Production. January 2007.
U.S. Environmental Protection Agency. 2008a. CEMS Cost Model. Available at:
http ://www. epa. gov/ttn/emc/cem/cems.xls.
U.S. Environmental Protection Agency. 2008b. Inventory of Greenhouse Gas Emissions and
Sinks: 1990-2006. EPA-430-R-08-005. Office of Atmospheric Programs, Washington,
DC. April 15.
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Appendix A. Assumptions Used in Landfill Threshold Analysis
This appendix summarizes the key assumptions and methodologies used to estimate the number
of landfills and the emissions included for various landfill emission reporting thresholds. The
assumptions and methodologies used for municipal solid waste (MSW) landfills are presented
first, and then the assumptions and methodologies used for industrial waste landfills are
presented.
A.1 Municipal Solid Waste (MSW) Landfills
Number of MSW Landfills
• The number of active and recently closed landfills was estimated from data presented in
"The State of Garbage in America" (BioCycle, 47(4), April 2006, pp. 26-43). A graph on
page 27 indicates that there were approximately 7,800 landfills in 1988 and 1,654
landfills in 2004. It was assumed that in 2006, the active landfills were approximately
1,600, so that there are approximately 6,200 (7,800 - 1,600) landfills that closed over the
past 18 years (i.e., since 1988), and approximately 460 landfills active landfills that are
not included in the landfill-specific model.
Methane Generation
• A landfill-specific model developed by RTI was used to estimate methane generation
rates in 2006. This model includes 1,142 landfills from the LMOP database that did not
report gas collection in 2003, or were projected to close prior to 2003. Based on the
waste acceptance rates (WAR), these landfills accounted for 88.5 percent of the waste
landfilled annually in the United States. The landfill specific model used the first order
decay model with an LO of 100 m3/mt and three different k values based on rainfall levels
(identical to what is used in the U.S. GHG Inventory). More details of the landfill
specific model are provided elsewhere.1
• Total active landfill methane generation was estimated by taking the model's estimated
methane generation and dividing it by 88.5% (proportion of total WAR covered by these
landfills). This total was then multiplied by 11.5% to estimate the total methane
generation for the "missing" active landfills. These "missing" landfills are generally
assumed to be small or to be construction and demolition debris landfills.
• Methane generation from closed landfills was estimated from the 2006 inventory
methane generation rates minus methane generation from active landfills.
Generation adjusted for oxidation
• Adjusted generation was estimated as methane generation less 10% oxidation of methane
near the landfill surface. This was used for all landfills (both open and closed). Adjusted
generation = Generation x (1-OX), where OX = oxidation fraction = 0.1 or 10%.
Emissions
• For the landfills included in the landfill-specific model, methane recovery was assumed
to be 75 percent of the methane generation rate under the following 3 conditions:
o The landfill is known to have a flare or landfill gas-to-energy (LFGTE) project
based on data available in the LMOP, EIA, or flare vendor databases used to
estimate CH4 recovery for the U.S. GHG Inventory.
1 "Development of Landfill-specific Methane Inventory Model" Memorandum from Jeff Coburn
and Marvin Branscome, RTI, to Elizabeth Scheele, EPA, dated May 6, 2005.
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o The landfill is projected to be subject to the NSPS: design capacity greater than
2.5-million Mg AND Year Open is 1991 or more recent AND 2006 methane
generation exceeds 1,174 mtCH4/yr (estimated to be equivalent to 50 Mg
NMOC/yr).
o The landfill is projected to be subject to the Emission Guidelines: design capacity
greater than 2.5-million Mg AND accepted waste in 1988, 1989, or 1990 AND
2006 methane generation exceeds 1,174 mtCH4/yr.
Emissions were than estimated as: (Generation - Recovery)x(l-OX), where OX =
oxidation fraction = 0.1 or 10%.
For active landfills not in the landfill-specific model, it was assumed that none had
recovery, so that emissions = adjusted generation.
For closed landfills, the total methane recovery estimate from the U.S. GHG inventory
was subtracted from the recovery estimated for the active landfills included in the
landfill-specific model. The emissions from closed landfills was then calculated to be
(Generation - Recovery) x (1-OX), where OX = oxidation fraction = 0.1 or 10%. This
yields nationwide methane emissions from both open and closed landfills of
111.1 MMTCO26 (commensurate with the inventory).
Threshold analyses for the active landfills included in the landfill specific model were
performed directly on the model predictions for each landfill.
Threshold analyses for the active landfills not included in the landfill specific model were
estimated based on expert judgment from the average size of the landfills.
o For the roughly 460 active landfills not included in the landfill-specific model, the
average adjusted generation per landfill was 39,000 mtCO2e. Based on this
average emissions rate, it was assumed 95% of these landfills exceed the IK
threshold; 80% of these landfills exceed the 10K threshold, 50% exceed the 25K
threshold, and 10 percent exceed the 100K threshold. The proportion of
generation covered by a threshold was assumed to be the same as the portion of
emissions over the threshold as calculated for the modeled landfills. For the 460
active landfills not in the landfill specific model, the landfill counts and emissions
covered by the emission thresholds were set equal to the counts and emissions
calculated for the generation threshold because these landfills were assumed not
to have recovery.
o For the closed landfills, the average adjusted generation per landfill was estimated
to be approximately 10,800 mtCO2e and the average emissions per landfill was
approximately 8,600 mtCO2e. Based on these average emissions rates, it was
assumed:
• 85% of these landfills exceed the IK generation threshold
• 85% exceed the IK emissions threshold
• 35% of these landfills exceed the 10K generation threshold
• 30% exceed the 10K emissions threshold
• 25% exceed the 25K generation threshold
• 20% exceed the 25K emissions threshold
• 10% exceed the 100K generation threshold
• 5% exceed the 100K emissions threshold.
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o The percentage of the emissions covered by a threshold level for the closed
landfills was assumed to be the same as the percentage of emissions covered by
the threshold for all active landfills.
A. 2 Industrial Waste Landfills
• The number of industrial landfills was estimated based on 1987 screening survey of
industrial Subtitle D waste management practices.
• Methane generation and methane emissions were estimated based on U.S. GHG
Inventory estimates.
• The number of landfills and percentage of waste covered by each threshold was estimated
based on expert judgment and the average methane emissions potential for the industrial
landfills.
• Industrial landfills were assumed not to have recovery, so there is no difference in the
generation versus emissions thresholds.
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