FOOD WASTE MANAGEMENT October2023
Quantifying Methane
Emissions from Landfilled
Food Waste
v>EPA
U.S. Environmental Protection Agency
Office of Research and Development
E PA-600-R-23-064
-------
Disclaimer
This document has been reviewed in accordance with U.S. Environmental Protection Agency (EPA) policy and
approved for publication.
Authors
Max Krause, U.S. EPA Office of Research and Development, Center for Environmental Solutions and Emergency
Response
Shannon Kenny, U.S. EPA Office of Research and Development, Office of Science Advisor, Policy and
Engagement
Jenny Stephenson, U.S. EPA Region 9
Amanda Singleton, Eastern Research Group, Inc. (ERG)
Reviewers
EPA would like to thank the following people for their independent peer review of the report:
Debra Reinhart, University of Central Florida
Nickolas Themelis, Columbia University
Nazli Ye§iller, California Polytechnic State University
Acknowledgements
The authors would like to thank Lauren Aepli, Claudia Fabiano, Elizabeth Goodiel, and Susan Thorneloe from
EPA, Kameron King and Alexandra Stern from Oak Ridge Institute for Science and Education, Natalie Detwiler
from Oak Ridge Associated Universities, and Gordon Coates, Ben Morelli, Sarah Cashman, Andrew Henderson,
and John Carter from ERG for their contributions to the report.
This report was prepared with support from ERG under GSA Contract GS-00F-079CA.The external peer review of
the report was coordinated by Versar, Inc. under U.S. EPA Contract No. EP-C-17-23.
Cover Photo by Max Krause, with artistic affects applied.
Quantifying Methane Emissions from Land filled Food Waste
-------
ABBREVIATIONS AND ACRONYMS
Abbreviation or Acronym
C&D (Debris)
CFR
CH4
CO2
GCCS
GHG
GHGRP
GWP
IPCC
k
Lo
LandGEM
LMOP
MSW
MMTCO
MTC02e
WARM
Definition
construction and demolition (debris)
U.S. Code of Federal Regulations
methane
carbon dioxide
gas collection and control system
greenhouse gas
Greenhouse Gas Reporting Program
global warming potential
Intergovernmental Panel on Climate Change
methane generation rate constant or waste decay rate
methane generation potential
Landfill Gas Emission Model
Landfill Methane Outreach Program
municipal solid waste
million metric tons of CC>2-equivalents
metric tons of CC>2-equivalents
Waste Reduction Model
Quantifying Methane Emissions from Landfiiied Food Waste
ii
-------
EXECUTIVE SUMMARY
Methane emitted from landfills results from the decaying of organic waste overtime under anaerobic conditions.
Methane is a greenhouse gas (GHG) that affects the earth's temperature and climate system. Because methane
is both a powerful GHG and short-lived compared to carbon dioxide, achieving significant reductions would have
a rapid and significant effect on reducing GHG emissions.
Most estimates of methane emissions from landfills are calculated based on the biodegradation of municipal solid
waste (MSW) as a whole. National estimates of methane emissions from particular components of the organic
fraction of MSW, such as food waste, have not been previously quantified by EPA. In the United States, a
significant fraction of food waste generated is sent to landfills (U.S. EPA, 2020a). In this analysis, EPA has
quantified the methane emissions released into the atmosphere from degrading food waste in MSW landfills in the
United States from 1990 to 2020. There is no other peer-reviewed national reference point for the amount of
methane emissions attributable to food waste in U.S. MSW landfills.
The analysis relies predominantly on existing, widely-used EPA models and data sources. It models landfill
methane emissions based on the following key parameters:
* Total tonnage of landfilled food waste;
* Characteristics of the landfill, such as its operational phase (closed or open), size, cover material, and the
climate in which its located;
* Rate at which food waste and other organic materials break down or decay;
* Schedule for installing, expanding, and maintaining operation of landfill gas collection systems after waste
is deposited and the portion of methane that is captured through landfill gas collection systems; and
* Portion of methane that oxidizes as it passes through the landfill cover material and is converted into
carbon dioxide before going into the atmosphere.
While there is uncertainty in any modeling approach, the results of the analysis indicate:
* In 2020, food waste was responsible for approximately 55 million metric tons of CO2 equivalents (mmt
CC>2e) emissions from U.S. MSW landfills.
* An estimated 58 percent of the fugitive methane emissions (i.e., those released to the atmosphere) from
MSW landfills are from landfilled food waste.
* An estimated 61 percent of methane generated by landfilled food waste is not captured by landfill gas
collection systems and is released to the atmosphere. Because food waste decays relatively quickly, its
emissions often occur before landfill gas collection systems are installed or expanded.
* While total methane emissions from MSW landfills are decreasing due to improvements in landfill gas
collection systems, methane emissions from landfilled food waste are increasing.
* For every 1,000 tons (907 metric tons) of food waste landfilled, an estimated 34 metric tons of fugitive
methane emissions (838 mmt CC>2e) are released.
* Reducing landfilled food waste by 50 percent in 2015 could have decreased cumulative fugitive landfill
methane emissions by approximately 77 million metric tons of CO2 equivalents (mmt CC>2e) by 2020,
compared to business as usual.
As the findings indicate, food waste has an outsized impact on landfill methane emissions due to its relatively
quick decay rate. Since fifty percent of the carbon in food waste is degraded to landfill gas within 3.6 years,
improving gas collection system efficiency in later years cannot substantially reduce these emissions. Diverting
food waste from landfills would be an effective way to reduce methane emissions from MSW landfills.
Quantifying Methane Emissions from Landfilled Food Waste
iii
-------
TABLE OF CONTENTS
Abbreviations and Acronyms ii
Executive Summary iii
List of Figures v
List of Tables v
Introduction 1
Methodology 1
Results & Discussion 9
Implications of Findings 13
Works Cited 14
Appendix A. Percentage of Food Waste in Lanfilled MSW Stream 16
Appendix B. Archetype Landfill Parameters Based on LMOP Database Query 19
Appendix C. Portioning National Tonnage of Landfilled Food Waste amongst the 10 Landfill Archetypes 20
Appendix D. Gas Collection Efficiency Installation and Operation Schedule 23
Appendix E. Modeled Landfilled Food Waste Emission Results 24
Quantifying Methane Emissions from Landfilled Food Waste iv
-------
LIST OF FIGURES
Figure 1. Factors that influence landfill methane emissions 2
Figure 2. Fate of methane generated from landfilled food waste 10
Figure 3. Contributions of food waste to methane emissions at MSW landfills 11
Figure 4. Amount of landfilled food waste and the methane generated from it 12
LIST OF TABLES
Table 1. Decay rates of various organic materials 5
Table 2. Landfill gas collection efficiency schedule 6
Table 3. 2020 Snapshot: Estimated MSW landfill methane emissions 9
Quantifying Methane Emissions from Landfilled Food Waste v
-------
INTRODUCTION
Municipal solid waste (MSW), commonly referred to as garbage or trash, is composed of the common materials
discarded from residential and commercial sources. Each year, roughly half of the MSW generated in the United
States is disposed in landfills (U.S. EPA, 2020a). When organic waste (including food waste) breaks down in
anaerobic (i.e., without oxygen) conditions in landfills, methane is produced. MSW landfills are the third-largest
source of methane emissions from human activities in the United States, contributing methane emissions
equivalent to 94 million metric tons of carbon dioxide (CO2) in 2020 (U.S. EPA, 2023a).1 Methane is a greenhouse
gas (GHG), which affects the earth's temperature and climate system. Because methane is both a powerful
greenhouse gas and short-lived compared to carbon dioxide, achieving significant reductions would have a rapid
and significant effect on global warming potential (U.S. EPA, 2022b).
Food waste comprises about 20 percent of MSW disposed of in U.S. landfills. In 2020, approximately 62.5 million
tons (56.7 million metric tons) of food waste was disposed of in MSW landfills. To understand the impact food
waste has on U.S. landfill GHG emissions, this analysis quantifies the estimated amount of methane emissions
released into the atmosphere from degrading food waste in MSW landfills from 1990 to 2020. This is the first time
EPA has published modeled estimates of annual methane emissions from landfilled food waste. There is no other
known national reference point for the national amount of methane emissions attributable to food waste in MSW
landfills. This analysis relied predominantly on existing, widely-used EPA models and data sources.
METHODOLOGY
This analysis begins with the annual national methane emissions from landfills from the Inventory of U.S.
Greenhouse Gas Emissions and Sinks (U.S. EPA, 2022c). These emissions are not directly measured. Instead,
the emissions are based on the landfill operators' reported methane generation, collection rates, and oxidized
methane, as shown in Equation 1.
Emitted = Generated - Collected - Oxidized (Eq.1)
Modeled methane emissions from landfills are subject to interpretation due to the various parameters that can
influence the calculated estimates. The data sources, approaches, and limitations for each of the key parameters
are discussed within this document. However, since national estimates of methane emissions are currently based
on modeled emissions, this analysis compares the estimates of modeled methane emissions for MSW landfills as
a whole with the estimates of modeled methane emissions for landfilled food waste. This provides a basis of
comparison to food waste's contributions to emissions from this source category as shown in Equation 2.
EgHGI - Efood = Enon-food (Eq. 2)
Where Eghgi is the MSW landfill emissions as reported in the Greenhouse Gas Inventory, Efood is the landfilled
food emissions calculated here, Enon-food is the difference which is attributed to all other biodegradable sources in
the landfill.
1 In 2020, emissions from MSW landfills accounted for approximately 86 percent of total landfill emissions (94.2 MMT C02 Eq.), while
industrial waste landfills accounted for the remainder (15.1 MMT C02 Eq.). Nationally, there are significantly fewer industrial waste landfills
(hundreds) compared to MSW landfills (thousands), which contributes to the lower national estimate of methane emissions for industrial waste
landfills. Additionally, the average organic content of waste streams disposed in industrial waste landfills is lower than MSW landfills (U.S.
EPA, 2022a).
Quantifying Methane Emissions from Landfilled Food Waste
1
-------
Key EPA Data Source
Inventory of U.S. Greenhouse Gas (GHG) Emissions and Sinks (U.S. GHG Inventory)
The U.S. GHG Inventory tracks GHG emissions and sinks by source, economic sector, and greenhouse gas,
from 1990 to present, releases a report each year. Overtime, the methodology for estimating annual landfill
methane emissions has evolved. For 1990-2004, the U.S. GHG Inventory currently uses a U.S.-specific first-
order decay model following the 2006IPCC Guidelines with the tonnages of landfilled estimated from a national
total of waste generated (based on states' survey responses) and a national average disposal factor developed
by BioCycle in collaboration with Columbia University for The State of Garbage in America reports.
With the introduction of EPA's Greenhouse Gas Reporting Program (GHGRP), the U.S. GHG Inventory began a
transition, relying on net methane emissions reported by landfills between 2005-2009. Within the GHGRP, MSW
landfill operators report modeled annual methane generation and emissions. From 2010 to present, the U.S.
GHG Inventory uses net methane emissions as directly reported by landfill operators through the GHGRP, with
a scale-up factor to account for emissions from landfills that aren't required to report to the GHGRP.
Tor more details, refer to the U.S. EPA (2022) Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2020 (EPA 430-R-22-003) and the EPA
Greenhouse Gas Reporting Program Subpart HH Information Sheet (2018) https://www.epa.gov/ghgreporting/subpart-hh-information-sheet
Within a landfill, several factors influence the amount of methane that is generated and emitted. These
parameters include the:
Total tonnage of landfilled material and its composition, particularly the portion that is
degradable organic material such as food waste;
St
Characteristics of the landfill, such as its size, cover materials, use of system for
leachate recirculation, and the climate in which it is located;
Rates at which food waste and other biodegradable (sometimes called organic)
materials decompose (break down or decay);
The schedule for installing, expanding, and maintaining operation of the landfill gas
collection system after waste is deposited, and the portion of methane that is captured
through landfill gas collection systems; and
1
Portion of methane that oxidizes as it passes through the landfill cover material and is
converted into carbon dioxide before going into the atmosphere.
Figure 1. Factors that influence landfill methane emissions.
Quantifying Methane Emissions from Landfilled Food Waste
2
-------
Tonnage of Landfilled Food Waste
A substantial amount of the food waste generated in the United States is ultimately disposed of in MSW landfills.
Because MSW landfills typically receive co-mingled wastes, landfills often do not have the ability to track the
tonnage of incoming food waste specifically, and the annual estimates of food waste disposed at landfills vary
depending on the method used (Kibler et al., 2018; Thyberg et al., 2015). The waste tonnage inputs into the
modeling for methane generation significantly impact the results. Appendix A compares two approaches for
estimating tonnages of landfilled food waste. The first is EPA's Advancing Sustainable Materials Management
Facts and Figures reports. The second is EPA's Greenhouse Gas Reporting Program (GHGRP). Facts and
Figures uses information from trade associations and economic data to estimate food production, use, loss, and
waste. GHGRP is reporting program whereby landfill operators submit information regarding tons of landfilled
waste disposed annually. Figure A1 displays the different estimates by year.
For the tonnage of landfilled food waste, this analysis uses data from the EPA Greenhouse Gas Reporting
Program (GHGRP) since landfills are required to directly report bulk waste data annually, and these data are
certified and confirmed using a multi-step verification process. Some landfills do not meet the threshold for
GHGRP requirements and others phase out of reporting requirements overtime. This analysis did not apply a
scale-up adjustment factor to account for difference in the landfills that report to GHGRP and the total number of
MSW landfills, since it is assumed to be minimal. EPA estimates that the landfills reporting to the GHGRP
represent more than 91% of the total emissions from MSW landfills (U.S. EPA, 2023a).
Landfill owners may report detailed tonnages of specific waste categories, such as food waste, but the vast
majority do not. Typically landfills track incoming wastes by the weight of trucks bringing in co-mingled wastes.
Thus, most landfills report only total waste tonnages, or separate the total out into one of three broad categories -
bulk waste (where food waste and other MSW would be categorized), inert waste (such as glass, plastics, metal
and concrete), or construction and demolition (C&D) waste (40 CFR 98).
Where food waste reports were available from reporting facilities, they were used in this analysis. For operators
reporting in three broad categories, inert and C&D data were removed from the annual disposal rates. For landfills
that reported a single bulk waste category, disposal rates were adjusted downward by applying the average
percent per year reported to be C&D, inert, or other specific waste streams by reporters that provided data in the
three main categories. This modified bulk waste value, excluding any actual or estimated inerts, C&D, or other
non-food waste material-specific categories, was used as the basis of annual waste tonnage rates for the
analysis.
For GHGRP bulk waste data or modified bulk waste data, the percent of landfilled MSW that was food waste from
the EPA Facts and Figures composition of landfilled MSW data was applied to calculate an annual national
estimated food waste disposal tonnage. See Appendix A for the percent of food waste in each year for 1960
through 2020.
~ chetype Landfills
The promulgation of the 1976 Resource Conservation and Recovery Act (RCRA) required operating landfills to
have liner systems to prevent groundwater contamination. Clean Air Act amendments further required gas
collection systems to mitigate air emissions. As a result, small, town dumpsites closed and larger, regional
sanitary landfills have opened. The number of operating landfills in 1988 was 7,924 and in 2020 there were
roughly 1,300 operating landfills (U.S. EPA, 2023a; U.S. EPA, 2001). While the total number of landfills
decreased substantially, the average size of each landfill remaining in operation has increased as many landfills
have transitioned to serve a larger regional area. These larger landfills have larger annual waste acceptance
rates, providing the opportunity for larger amounts of waste disposal prior to when the landfill gas collection
system may be installed. This timing is especially relevant for food waste disposal because food waste decays
more quickly than other types of MSW.
Because landfills were much smaller, the safety concern for explosive methane gas was not well understood, and
because the technology was not widely available, very few of the landfills that operated and closed prior to the
1980s installed a gas collection and control system (GCCS).
Quantifying Methane Emissions from Landfilled Food Waste
3
-------
To reflect the variation in landfill operating practices from 1960 through 2020, ten archetypes for MSW landfills
(i.e., 10 "model" landfill types) were created in this study. The parameters for the archetypes included average
landfill open and closure years, presence of a gas collection system, and total waste-in-place amounts and were
derived from the U.S. EPA Landfill Methane Outreach Program (LMOP) (U.S. EPA, 2021b). Appendix C details
the landfill parameters of each of the 10 archetype landfills used for this indicator.
Landfill and Landfill Gas Energy Database
(LMOP Database)
The 2,600 landfills in the LMOP database (U.S.
EPA, 2021 b) were partitioned into this set of 10
archetype landfills to identify the relative fraction
of waste disposed across a variety of landfill
parameters. Overall, there was robust coverage of
landfills in the database with known closure year
to develop the models. Nearly 90 percent of the
total number of landfills, and 99 percent of the
waste-in-place totals in the LMOP database, were
reflected by the 10 models. The remaining 10
percent of landfills and less than one percent of
waste-in-place totals had an unknown closure
year and could not be assigned to one of the
models.
The national tonnage of landfilled food waste was
then allocated to the 10 archetype landfills. The
food waste tonnage was divided proportionally
using the total waste-in-place amounts among the
landfills that operated each year. For example, if
landfills operating in the year 1961 fit under only
two of the archetypal landfills, then the national
landfilled food waste tonnage was assigned
proportionally among only those two archetypes.
However, if landfills operating in 1982 resembled
eight of the 10 archetypes, then the national
landfilled food waste tonnage was divided proportionally among those eight archetypes. Since 1980, the majority
of food waste has gone to landfills with landfill gas capture systems and was modeled as such. Appendix C
details how the national food waste disposal quantities were assigned to each of the 10 landfill archetypes.
of the reported data parameters into its database.
stakeholders and waste officials to reduce or avoid
Methane emitted from landfills is a result of organic waste decaying under anaerobic conditions. Organic waste
decays over many years after it is placed in a landfill. Temperature, moisture, pH, and type of organic waste
impacts how quickly it decays. Because of this decomposition pattern, the estimated methane emissions in a
particular calendar year are the sum of emissions that are generated from waste disposed over a historical time
horizon. The emissions estimate for the period of interest (1990-2020) relies on estimated annual food waste
disposal rates for the period of 1960 through 2019.
The decay rate is a first order reaction - the higher the rate, the faster the decay. For example, a decay rate of
0.02 means that half of the carbon has been degraded to methane in 34.7 years, whereas a decay rate of 0.2
means that half of the carbon has been degraded in 3.47 years. Organic materials have varying rates of decay,
with examples shown in the table below. This analysis used the national average food waste decay rate (k) of
0.19 year-1 from EPA's Waste Reduction Model v15 (WARM) and methane generation potential of 109 m3/Mg of
food waste2 based on WARM default degradable organic carbon content of food waste category (U.S. EPA,
2020b). These values were input into EPA's Landfill Gas Emissions Model (LandGEM) to calculate methane
generation for each of the 10 archetype landfills.
2 Methane generating potential value of 1.62 MTC02e/short ton (WARM v15) equates to 109 m3/Mg which is the required LandGEM input units
of measure.
Quantifying Methane Emissions from Landfilled Food Waste
4
-------
Table 1. Decay rates of various organic materials
Material
Decay rate
(yr-1)
Number of years over
which 1/2 of the carbon has
been degraded to methane
Branches (Yard)
0.02
34.6
Cardboard
0.03
23.1
Copy paper
0.04
17.3
Dimensional lumber
0.11
6.3
Food waste
0.19
3.6
Leaves (Yard)
0.22
3.2
Grass (Yard)
0.39
1.8
Source: EPA WARM v15
The WARM defaults for food waste decay rates (k) and food waste methane generation potential (Lo) serve as a
commonly used source of landfill gas modeling parameters for the nation. The decay rates in WARM are based
on a study by De la Cruz and Barlaz (2010) which measured component-specific decay rates in laboratory
experiments, with a lab-scale decay rate for food waste of 0.3 yr1. The national average food waste decay rate
from WARM of 0.19 yr1 is a weighted average of component-specific decay rates from De la Cruz and Barlaz
(2010) based on the share (as determined by EPA expert judgement in 2010) of waste received at four categories
of landfills with different moisture scenarios (influenced by annual precipitation and leachate recirculation). The
U.S. GHG Inventory uses a modified decay rate for food waste of 0.151 per year. The component specific decay
rate from De la Cruz and Barlaz (2010) serves as a starting point for this value but a weighted average based on
annual precipitation categories and population residing in each precipitation category is applied (U.S. EPA,
2022c). In reality, the decay rate could vary by landfill according to climate (temperature and precipitation), landfill
operations (e.g., are liquids being recirculated or added at the landfill), and the type of food waste landfilled (Jain
etal., 2021).
Landfill Gas Collection Systems
Methane collection in any calendar year will depend on a variety of factors, including the operating status of the
landfill, whether or not the landfill has a landfill gas collection system installed, and the schedule for installing,
expanding, and maintaining operation of the GCCS after waste is deposited.
This analysis estimated the fraction of landfills operating with and without active landfill GCCS based on data
reported to EPA LMOP (U.S. EPA, 2021b). The presence or absence of a GCCS was identified and then the total
fraction of waste disposed in each of the archetype landfills was determined to allocate the methane generation
estimates to different GCCS scenarios. Each analysis assumes that the collection system remains operational in
a given area of the landfill for a 30-year period. Based on the selected decay rate, at 30 years, food waste will
have decomposed 99.6% of the anaerobically degradable carbon to methane and carbon dioxide. Thus, in this
scenario, modeling food waste methane generation beyond 30 years is unnecessary.
Quantifying Methane Emissions from Landfilled Food Waste
5
-------
Table 2. Landfill gas collection efficiency schedule
WARM default collection scenario
Collection Efficiency Years
0% 0-4
50% 5-9
75% 10-14
82.5% 15-20
90% Final Cover
Source: EPA WARM v15
b.¦!v„
This analysis uses a phased landfill gas collection schedule with a four-year lag period before a GCCS is installed
after waste is deposited, based on when landfills are obligated to install a gas collection system to comply with
EPA's New Source Performance Standards (NSPS) and the state and federal plans that implement the EPA
Emission Guidelines. These federal rules allow for an initial lag period to install a gas collection system of 30
months after the first nonmethane organic compounds (NMOC) report shows that the emission thresholds in the
rule have been triggered. Once the system is installed the rules allow for expansion of the gas collection system
at a schedule of every two years if the cell is closed and at final grade and five years for active cells. Based on
public feedback and comments received on the proposed NSPS3, most modern large landfills do not reach final
grade within 2 years and a majority of landfills are complying with the 5-year gas collection system expansion
provision (40 CFR 60, 2016). Therefore, a 4-year expansion lag time was assumed to represent the baseline.4
The EPA WARM model assigned collection efficiencies to each phased expansion of the GCCS.
A phased collection accounts for landfill operations in which some part or cells of the landfill may be actively
receiving wastes and, overtime, more of the landfill is permanently covered. Collection efficiencies can vary
widely depending on gas collection system operations and maintenance (Anshassi et al., 2022; Barlaz et al.,
2009; Themelis & Bourtsalas, 2021). The schedules and collection efficiencies for gas collection system
operations may vary depending on how well the gas collection system is designed and maintained, as well as
how quickly an operator decides to install or expand its gas collection system coverage area. Even a well-
operated gas collection system may experience periodic shutdowns to address system repairs, so these
collection efficiency assumptions are not reflective of constant rates throughout the year. In addition to the
operation of the gas collection system, other landfill operating practices such as landfill cover maintenance and
removal of immediate cover during gas well installation may decrease the instantaneous gas collection efficiency
and increase the release of fugitive emissions (Spokas et al., 2021).
After landfill gas is collected, it is routed to a control device. The control device can be an open or enclosed flare,
or in the case of landfills with energy recovery projects the control device could be an engine, boiler, or gas
processing equipment for generating electricity or equipment to upgrade the landfill gas into renewable natural
gas. Regardless of the control device, the estimated methane destruction efficiency exceeds 99 percent any year
where GCCS is anticipated to be operating at a landfill. A destruction efficiency of 99 percent was used for any
collected gas based on EPA Best Available Control Technology (BACT) guidance for landfills (U.S. EPA, 2011).
Appendix D provides a lookup table for landfill gas collection efficiency installation and operation schedule.
ethane Oxidized
Open MSW landfills apply daily cover over the waste actively being disposed of in the landfill. The daily cover
materials are typically soils, though some states allow the use of alternative daily cover of green waste, waste
derived materials (e.g., shredded tires), biosolids, and contaminated soil (U.S. EPA, 2022a). Intermediate covers
are used once the landfill attains a certain height and active disposal will not occur again in that area for an
3 79 FR 41796
4 See 60.765(b) and 60.762(b)(2)(H) for initial and expansion lag times allowed by the NSPS regulations.
Quantifying Methane Emissions from Land filled Food Waste
6
-------
extended period (i.e., months or years). Once the landfill cell has achieved its maximal height and will no longer
receive waste, a final cover system consisting of thick earthen materials and geosynthetics designed to minimize
infiltration of liquids and soil erosion are placed (40 CFR 258). Each of these types of covers vary in thickness,
soil or material type.
Methane that is not collected by the gas collection system moves to the surface of the landfill where it can escape
to the atmosphere. Biologically active and well-maintained soil cover systems can oxidize methane to carbon
dioxide. The magnitude of bio-conversion from methane to carbon dioxide is a function of soil type and moisture
content, the flux or flow of methane, and other daily weather conditions (Chanton et al., 2009; IPCC, 2007;
Schuetz et al., 2003; Ye§iller et al., 2022). In US landfill emission models, the oxidation credit is assigned based
on the soil type and a simple coefficient ranging from 0-35 percent. The range of oxidation as a percentage of
uncollected methane reflects poorly managed or exposed wastes to well-maintained and geo-engineered soil
systems.
Unlike gas collection, which would be expected to expand or increase overtime, methane oxidation is a function
of soil type and landfill management, not necessarily landfill age. Landfills with final covers that include thick clay
layers and possibly geomembranes are designed to prevent methane escape, substantially increasing methane
collection but reducing methane oxidation. Alternately, intermediate covers can have strong oxidation potential
(Barlaz et al., 2009; Chanton et al., 2009). Daily covers, applied in areas of active disposal, are primarily used for
vector control (e.g., birds and other wildlife), to prevent food scavenging, and are not intended to oxidize methane.
Because soil types are assumed, the modeling applied an oxidation rate of 25 percent for all years. While higher
oxidation rates can be achieved, 25 percent was used as an approximate average. Appendix D provides a table
of the gas collection, oxidation rates, and gas system destruction efficiencies used in the analysis.
Methane Generation
For this analysis, methane generated in years 1990 through 2020 was calculated by the U.S. EPA LandGEM
model, which uses a first-order kinetic model of methane production in landfills. The modeling parameters used in
the LandGEM model were as follows:
* Tonnage of landfilled food waste. See Appendix
* Landfill open and closure years - varies dependi
Appendix C.
* Food waste decay rate (k) - 0.19 per year
based on WARM national weighted average
based on moisture content of the landfill
receiving the waste (U.S. EPA 2020c).Methane
generating potential (L0) - 109 m3/Mg of food
waste based on WARM default degradable
organic carbon content of food waste category
(U.S. EPA 2020c).
¦ Methane content of landfill gas - 50 percent
(LandGEM model default). Landfill gas is
typically composed of 50 percent methane, 50
percent carbon dioxide and less than 1 percent
of nonmethane organic compounds by volume
(U.S. EPA, 2005)
The fugitive methane emissions that are released into
the atmosphere are calculated by modeling the
estimated methane generation rates from the decay of
landfilled food waste minus the methane collected and
combusted, minus methane emissions oxidized by the
landfill surface cover. LandGEM was used, with the
parameters specified above, to calculate the estimated
methane generation rates from landfilled food waste.
The LandGEM model was run for each of the ten
on parameters for each archetype landfill. See
Spotlight on EPA Tools
Landfill Gas Emissions Model (LandGEM)
An excel-based tool is used to estimate emission rates
for total landfill gas, methane, carbon dioxide,
nonmethane organic compounds, and individual air
pollutants from municipal solid waste landfills. It can be
used for determining whether a landfill is subject to the
control requirements of federal regulations for MSW
landfills laid out by the Clean Air Act. The model can
also be used to generate annual and total emissions
estimates for use in emissions inventories and air
permits.
Waste Reduction Model (WARM)
Based on lifecycle assessment data, this tool provides
total lifecycle GHG emissions estimates from different
waste management practices, including landfilling.
Quantifying Methane Emissions from Landfilled Food Waste
7
-------
archetype landfills, reflecting the years of operation and the annual tonnages of food waste disposed of in the
landfill, resulting in annual methane generation estimates. Then, for the five archetype landfills that had a gas
collection system, the landfill gas collection efficiency schedule, along with the 99 percent destruction efficiency of
the landfill gas by combustion, was applied to the annual methane generation values. A methane oxidation rate of
10 percent was applied for all 10 of the archetype landfills. Appendix F provides the summed annual methane
generation and methane emission estimates from landfilled food waste for 1990 to 2020.
Limitations
The primary sources of uncertainty for this analysis are the derivation of the landfilled food waste tonnages and
limitations associated with using a simplified first-order decay model. Because no quantified uncertainty
measurements are available for methane from landfilled food waste, the estimates of methane emissions could be
higher or lower. Various parameters can influence the model-based estimates, such as variations in decay rate
due to temperature and precipitation, the efficacy of gas collection systems, and other landfill maintenance
practices such as the presence of a leachate recirculation system (Amini et al., 2012; Amini et al., 2013).
Uncertainty in estimated methane emissions could affect conclusions drawn and the relationship between total
U.S. GHG emissions and those specifically from landfilled food waste.
Several sources of uncertainty such as the amount of food waste disposed of in landfills each year are expected
to be consistent across time and should not affect relative trends in food waste methane emissions. The decay
value of food waste, which can vary depending on climate and temperature, can also create uncertainty and
variability, although to a lesser extent than the uncertainty over the exact amount of food waste disposed of in
landfills each year.
While the LMOP database used to create the representative model landfills is the most comprehensive national
database of landfills available, the database focuses on landfills that are active or that have closed since 1990.
Data received for inclusion in the LMOP database are reviewed for reasonableness and are corroborated via
other data sources when possible. The database is incomplete for landfills closing prior to 1990. However,
methane emissions from food waste disposed from these older landfills are not expected to have a significant
impact on the methane emissions occurring in the period of 1990-2020 because most of the methane emitted
from degrading landfilled food waste occurs within 30 years of its disposal (De la Cruz & Barlaz, 2010).
Quantifying Methane Emissions from Landfilled Food Waste
8
-------
RESULTS & DISCUSSION
The purpose of this study was to estimate the quantity of methane emissions released into the atmosphere from
degrading food waste in MSW landfills nationally from 1990 to 2020, to understand the impact food waste has on
landfill methane emissions. The analysis relied predominantly on existing, widely-used EPA models and data
sources, such as GHG Inventory, GHG Reporting Program, LMOP database, and the WARM and LandGEM
models. See Appendix E for a data table of results.
The five main findings of the study are:
~ An estimated 58 percent of fugitive methane emissions from MSW landfills are from
landfilled food waste.
Methane emissions from landfilled food waste are a subset of the total methane emissions from MSW
landfills. Landfilled food waste is contributing to more methane emissions than other landfilled materials
because it degrades more quickly, and this quicker decay can occur before a GCCS is installed or expanded
at the landfill.
In 2020, landfilled food waste was responsible for an estimated 58 percent of the total methane emissions
from MSW landfills, emitting approximately 55 mmt CChe methane emissions based on a 100-year global
warming potential (GWP). According to EPA's Greenhouse Gas Equivalency Calculator, this is equivalent to
the annual GHG emissions from 15 coal-fired power plants (U.S. EPA, 2023b). See Table 3, below, for
detailed information on 2020 landfill methane emissions. Results were also calculated with 20-year GWP,
which estimates the energy absorbed by a gas over 20 rather than 100 years, since methane has a much
shorter lifetime than carbon dioxide. In 2020, landfilled food waste emitted 180 mmt CChe based on a 20-year
GWP.
Table 3. 2020 Snapshot: Estimated MSW landfill methane emissions
Fugitive Methane Emissions Methane Generation
Contributions
mint CO. e
%
mmt CO e
mmt CO e
%
mmt CO e
(100 yr GWP)
Total
(20 yr GWP)
(100 yr GWP)
Total
(20 yr GWP)
TOTAL
94
100%
309
305
100%
1.000
Food Waste
55
58%
180
89
29%
293
Other Waste
39
42%
129
215
71%
707
Notes: Totals may not sum due to independent rounding. a100-year GWP of methane = 25 (consistent with
the US GHG Inventory (U.S. EPA, 2022c). b20-yearGWP of methane = 82 (U.S. EPA, 2023c).
~> An estimated 61 percent of methane generated by landfilled food waste avoids collection by
landfill gas collection systems and becomes fugitive emissions (i.e., is released to the
atmosphere).
In 2020, an estimated 61 percent of the methane generated from landfilled food waste escaped to the
atmosphere before it could be collected or oxidized.
Figure 2 illustrates total methane generated from landfilled food waste, breaking down (1) the amount that is
emitted into the atmosphere as fugitive methane emissions (shown in dark blue) and (2) the amount that is
captured by the collection system or oxidized by the landfill soil cover (shown in light blue).
5100-year GWP of methane = 25 (consistent with the US GHG Inventory (U.S. EPA, 2022a))
6 20-year GWP of methane = 82 (U.S. EPA, 2022d)
Quantifying Methane Emissions from Landfilled Food Waste
3
-------
Collected or Oxidized
Emitted
100-
o
E°
2 E
a) ro
S5
O "o
• §
m U-
re
j= "O
d)
0> ==
"O
c
re
80-
~ 60-
40-
= 20-
0-
# CK^ C# # ^ ^ «Sf> <# ^ ^ ^ ^ ^ #
Year
Figure 2. Fate of methane generated from landfilled food waste
~ While total emissions from MSWlandfills are decreasing, methane emissions from landfilled
food waste are increasing.
As shown in Figure 3, total methane emissions from MSW landfills decreased by 43 percent from 1990 to
2020 as federal and state regulations for gas collection requirements expanded. This has led to
improvements in national gas collection efficiencies as more landfills have controlled their emissions,
particularly at later points of the landfill lifetime (where gas generation is dominated by paper products and
other non-food waste components).
During this same time period, methane emissions from landfilled food waste increased steadily by 295
percent.
This is due to annual increases in the amount of food and all other MSW components being landfilled.
Food waste emissions occur earlier and landfill operators are collecting more gas later in the landfill lifetime.
Thus, for materials like biodegradable textiles, paper products, and wood, which degrade more slowly, more
of the landfill gas is collected.
Quantifying Methane Emissions from Landfilled Food Waste
10
-------
Food waste
All other wastes
180
c^3 o$* e£V Ci° c£> N? \W _\^ nS® -*?>
Year
Figure 3. Contributions of food waste to methane emissions at MSW landfills.
For every 1,000 tons (907 metric tons) of food waste landfilled, an estimated 34 metric tons
of fugitive methane emissions are released.
Using the modeling parameters as described in the methodology section, along with the same moisture and
carbon content for food waste from the U.S. Greenhouse Gas Inventory (U.S. EPA, 2022f) for the carbon
storage portion, it is estimated that for every 1,000 tons (907 metric tons) of food waste sent to a landfill, 22
metric tons of carbon originating from food waste remains as carbon stored in the landfill after 30 years, and
34 metric tons is emitted as fugitive methane7 over a 30-year period after disposal. For every one metric ton
of carbon dioxide equivalent (MTCC>2e) that is stored, approximately 16 MTC026 were released as fugitive
methane emissions.
~ Reducing food waste by 50 percent in 2015 could have decreased cumulative fugitive landfill
methane emissions by approximately 77 million MTC02e. compared to business as usual, by
2020.
The amount of food waste disposed in landfills has steadily increased since 1990, with a corresponding
increase in methane generation and emissions. There is increasing focus on preventing wasted food and
reducing the amount of it that is disposed in a landfill. While this analysis did not project future tonnages of
landfilled food waste and associated emissions, it can be used to examine the effects had landfilled food
waste been halved in 2015 and held constant through 2020. The year 2015 was chosen because this is the
year the U.S. set the National Food Loss and Food Waste Reduction Goal to halve food waste by 2030.
Based on the approach described earlier, using GHGRP landfill tonnages to derive an amount of food waste
landfilled, this analysis estimated that nearly 46 million metric tons of food waste was disposed in landfills in
2015. If the U.S. had halved the amount of food waste to approximately 23 million tons starting in 2015 and
held that constant through 2020, approximately 77 mmt C02e fewer methane emissions would have been
emitted from MSW landfills in the subsequent five years. This emissions reduction is roughly equivalent to the
carbon dioxide emissions from 21 coal-fired power plants or 15 million homes' energy use for a year (U.S.
EPA, 2023b).
7 Equivalent to 1,307 metric tons of CChe, based on GWP of 25 kg CCbe / kg ChU, from the IPCC AR4, 100-year time horizon or more than
4,200 MTCCbe based on a 20-year GWP for methane.
Quantifying Methane Emissions from Landfilled Food Waste
11
-------
Figure 4 shows tonnage of food waste landfiiled and total fugitive methane emissions from landfills each year
from 1990 to 2020. The greeniine shows the methane emissions based on the amount of food waste landfiiled (as
reported and derived from the GHGRP tonnages). The yellow line reflects the impact to methane emissions had
the amount of landfiiled food waste been cut in half in 2015 and held constant (hatch pattern).
Food waste landfiiled — Current Status Alternate Scenario
-------
IMPLICATIONS OF FINDINGS
While the potential to reduce methane emissions by reducing landfilled food waste has been well established
(Hodge et al., 2016; Levis & Barlaz, 2011), this is EPA's first estimate of annual methane emissions from
landfilled food waste in the United States. Because of its relatively fast decay rate, most of the food waste-based
methane escapes to the atmosphere before it can be captured with a typical GCCS. Although food waste
comprises 24 percent of the MSW stream, it constitutes an estimated 58 percent of annual landfill methane
emissions. Thus, it can be reasonably stated that food waste has an outsized impact on landfill methane
emissions. Reducing the amount of food waste disposed in landfills would be an effective way to reduce methane
emissions from MSW landfills.
MSW landfills are a significant source of methane emissions in the U.S. for which landfilled food waste is a
leading contributor. There are management options for food waste other than landfills that are less damaging to
the climate. Comparative lifecycle assessment analyses evaluating management pathways for food waste have
found that landfills are the least preferable pathway because they have higher greenhouse gas emissions (Morris
et al., 2017). Landfilling food waste does not promote a circular economy because it fails to utilize the nutrient
value of the food waste.
The most environmentally preferable approach is to prevent food from being wasted (Kibler et al., 2018). More
than one-third of the U.S. food supply is not consumed, resulting in a "waste" of resources—including agricultural
land, water, pesticides, fertilizers, and energy—and the generation of environmental impacts—including
greenhouse gas emissions and climate change, consumption and degradation of freshwater resources, loss of
biodiversity and ecosystem services, and degradation of soil quality and air quality (U.S. EPA, 2021a). Given the
significant resource inputs (land, water, fertilizer, etc.) used to produce and deliver food to consumers, to then
have it go to waste and be disposed in a landfill, generating methane emissions, compounds the environmental
impacts of food waste.
Quantifying Methane Emissions from Landfilled Food Waste
13
-------
WORKS CITED
40 CFR 60. - Subpart Cf - Emission Guidelines and Compliance Times for Municipal Solid Waste Landfills. 2016.
https://www.ecfr.gov/current/title-40/chapter-l/subchapter-C/part-60/subpart-Cf.
40 CFR 98. - Subpart HH - Municipal Solid Waste Landfills. 2009. Code of Federal Regulations.
https://www.ecfr.qov/current/title-40/chapter-l/subchapter-C/part-98/subpart-HH.
40 CFR 258. - Criteria for Municipal Solid Waste Landfills. 1991. Code of Federal Regulations.
https://www.ecfr.qov/current/title-40/chapter-l/subchapter-l/part-258.
Amini, H.R., Reinhart, D.R., Mackie, K.R. 2012. Determination of first-order landfill gas modeling parameters and
uncertainties. Waste Management, 32(2), 305-316. 10.1016/j.wasman.2011.09.021
Amini, H.R., Reinhart, D.R., Niskanen, A. 2013. Comparison of first-order-decay modeled and actual field
measured municipal solid waste landfill methane data. Waste Management, 33(12), 2720-2728.
10.1016/j.wasman.2013.07.025
Anshassi, M., Smallwood, T., Townsend, T.G. 2022. Life cycle GHG emissions of MSW landfilling versus
Incineration: Expected outcomes based on US landfill gas collection regulations. Waste Management,
142, 44-54. https://doi.Org/10.1016/i.wasman.2022.01.040
Barlaz, M.A., Chanton, J.P., Green, R.B. 2009. Controls on landfill gas collection efficiency: instantaneous and
lifetime performance. Journal of the Air & Waste Management Association, 59(12), 1399-1404.
Chanton, J.P., Powelson, D.K., Green, R.B. 2009. Methane oxidation in landfill cover soils, is a 10% default value
reasonable? Journal of environmental quality, 38(2), 654-663.
Cusworth, D.H., Duren, R.M., Thorpe, A.K., Tseng, E., Thompson, D., Guha, A., Newman, S., Foster, K.T., Miller,
C.E. 2020. Using remote sensing to detect, validate, and quantify methane emissions from California
solid waste operations. Environmental Research Letters, 15(5), 054012. 10.1088/1748-9326/ab7b99
De la Cruz, F.B., Barlaz, M.A. 2010. Estimation of Waste Component-Specific Landfill Decay Rates Using
Laboratory-Scale Decomposition Data. Environmental Science & Technology, 44(12), 4722-4728.
10.1021/es100240r
Duren, R.M., Thorpe, A.K., Foster, K.T., Rafiq, T., Hopkins, F.M., Yadav, V., Bue, B.D., Thompson, D.R., Conley,
S., Colombi, N.K. 2019. California's methane super-emitters. Nature, 575(7781), 180-184.
Hodge, K.L., Levis, J.W., DeCarolis, J.F., Barlaz, M.A. 2016. Systematic Evaluation of Industrial, Commercial, and
Institutional Food Waste Management Strategies in the United States. Environmental Science &
Technology, 50(16), 8444-8452. 10.1021/acs.est.6b00893
IPCC. 2007. 2006 IPCC Guidelines for National Greenhouse Gas Inventories Volume 5 Waste, https://www.ipcc-
nqqip.iqes.or.ip/public/2006ql/vol5.html. Accessed on: 4/5/2022.
IPCC. 2019. Chapter 3 Solid Waste Disposal, in: 2019 Refinement to the 2006 IPCC Guidelines for National
Greenhouse Gas Inventories, (Eds.) E. Calvo Buendia, K. Tanabe, A. Kranjc, J. Baasansuren, M.
Fukuda, Ngarize S., A. Osako, Y. Pyrozhenko, P. Shermanau, S. Federici, IPCC. Switzerland.
Jain, P., Wally, J., Townsend, T.G., Krause, M., Tolaymat, T. 2021. Greenhouse gas reporting data improves
understanding of regional climate impact on landfill methane production and collection. PloS one, 16(2),
e0246334.
Kaplan, P.O., Decarolis, J., Thorneloe, S. 2009. Is it better to burn or bury waste for clean electricity generation?,
ACS Publications.
Kibler, K.M., Reinhart, D., Hawkins, C., Motlagh, A.M., Wright, J. 2018. Food waste and the food-energy-water
nexus: A review of food waste management alternatives. Waste Management, 74, 52-62.
10.1016/j.wasman.2018.01.014
Levis, J.W., Barlaz, M.A. 2011. What is the most environmentally beneficial way to treat commercial food waste?
Environmental science & technology, 45(17), 7438-7444.
M0nster, J., Kjeldsen, P., Scheutz, C. 2019. Methodologies for measuring fugitive methane emissions from
landfills—A review. Waste Management, 87, 835-859.
Quantifying Methane Emissions from Land filled Food Waste
14
-------
Morris, J. 2010. Bury or burn North America MSW? LCAs provide answers for climate impacts & carbon neutral
power potential. Environmental science & technology, 44(20), 7944-7949.
Morris, J. 2017. Recycle, bury, or burn wood waste biomass?: LCA answer depends on carbon accounting,
emissions controls, displaced fuels, and impact costs. Journal of Industrial Ecology, 21(4), 844-856.
Morris, J., Brown, S., Cotton, M., Matthews, H.S. 2017. Life-cycle assessment harmonization and soil science
ranking results on food-waste management methods. Environmental science & technology, 51(10), 5360-
5367.
Schuetz, C., Bogner, J., Chanton, J., Blake, D., Morcet, M., Kjeldsen, P. 2003. Comparative oxidation and net
emissions of methane and selected non-methane organic compounds in landfill cover soils.
Environmental science & technology, 37(22), 5150-5158.
Spokas, K., Bogner, J., Corcoran, M. 2021. Modeling landfill CH4 emissions: CALMIM international field
validation, using CALMIM to simulate management strategies, current and future climate scenarios. Elem
SciAnth, 9(1), 00050.
Themelis, N.J., Bourtsalas, A. 2021. Methane generation and capture of US landfills. J. Environ. Sci. Eng. A, 10,
199-206.
Thyberg, K.L., Tonjes, D.J., Gurevitch, J. 2015. Quantification of Food Waste Disposal in the United States: A
Meta-Analysis. Environmental Science & Technology, 49(24), 13946-13953. 10.1021/acs.est.5b03880
U.S. EPA. 2020a. Advancing Sustainable Materials Management: 2018 Tables and Figures.
https://www.epa.gov/sites/default/files/2021~
01/documents/2018 tables and figures dec 2020 fnl 508.pdf. Accessed on: November 2021.
U.S. EPA. 2011. Available and Emerging Technologies for Reducing Greenhouse Gas Emissions from Municipal
Solid Waste Landfills. U.S. EPA.
U.S. EPA. 2022a. Chapter 6: Land Use, Land-use Change, and Forestry, in: Inventory of U.S. Greenhouse Gas
Emissions and Sinks: 1990-2020.
U.S. EPA. 2020b. Documentation for Greenhouse Gas Emission and Energy Factors Used in the Waste
Reduction Model (WARM).
U.S. EPA. 2021a. From Farm to Kitchen: The Environmental Impacts of U.S. Food Waste.
U.S. EPA. 2023a. GHGRP Waste Sector Profile. Waste Sector 2021. https://www.epa.gov/ghgreporting/ghgrp~
waste-sector-profile. Accessed on: 06/01/2023.
U.S. EPA. 2023b. Greenhouse Gas Equivalencies Calculator, https://www.epa.gov/enerqv/qreenhouse~gas-
eauivalencies-calculator#results. Accessed on:
U.S. EPA. 2022b. Importance of Methane, https://www.epa.gov/qmi/importance-methane
Accessed on: 04/20/2023.
U.S. EPA. 2022c. Inventory of US Greenhouse Gas Emissions and Sinks 1990-2020.
U.S. EPA. 2005. Landfill Gas Emissions Model (LandGEM) Version 3.02 User's Guide. EPA-600/R-05/047. U.S.
EPA.
[dataset] U.S. EPA, Landfill Methane Outreach Program (LMOP) Landfill and LFG Energy Project Database,
2021b.
U.S. EPA. 2001. Municipal Solid Waste in The United States: 1999 Facts and Figures. EPA530-R-01-014.
U.S. EPA. 2023c. Understanding Global Warming Potentials, https://www.epa.gov/ghgemissions/understanding-
global-warming-potentials. Accessed on: 7/31/2023.
Ye§iller, N., Hanson, J.L., Manheim, D.C., Newman, S., Guha, A. 2022. Assessment of methane emissions from a
California landfill using concurrent experimental, inventory, and modeling approaches. Waste
Management, 154, 146-159. https://doi.Org/10.1016/i.wasman.2022.09.024
Quantifying Methane Emissions from Land filled Food Waste
15
-------
APPENDIX A. PERCENTAGE OF FOOD WASTE IN LANDFILLED
MSW STREAM
The EPA Facts and Figures report makes landfilled waste composition data available for most years 1960 through
2018 in its most recent release (U.S. EPA, 2020a). This release provides data for 1960, 1970, 1980, 1990, 2000,
2005, and 2010 through 2018. To provide data for some of the missing years, data were obtained from the 2012,
2013, and 2014, and 2015 versions of the Advancing Sustainable Materials Management: Facts and Figures
reports, as well as historical data tables that EPA developed for 1960 through 2018. Remaining years in the time
series for which data were not available in Facts and Figures were estimated using linear interpolation matching.
The missing values match those that are used in the U.S. Greenhouse Gas Inventory Chapter 6 - Land-Use-
Land-Use Change, and Forestry (U.S. EPA, 2022c). Since the Advancing Sustainable Materials Management:
Facts and Figures has not been updated since 2018, the percentage of landfilled MSW that is food waste for 2019
and 2020 were set equal to 2018 annual rates.
EPA has two data sets for annual tonnages of landfilled waste. One data set is the tonnages of broad categories
of landfilled material as reported by landfills to the EPA GHGRP which was described earlier. The second data set
is EPA's Facts and Figures which estimates the tonnages of materials or wastes generated by sectors and how
that material is managed (recycled, composted, landfilled, incinerated, etc).
For food waste, the EPA Facts and Figures applies sector specific (i.e., residential, institutional, and commercial)
food waste generation factors and information on how the food waste is managed (ex. composted, anaerobically
digested, landfilled) to estimate the amount of food waste generated and the portion that is landfilled. EPA
estimated wasted food generation from residential, commercial, and institutional sources, using data from
sampling studies and industry-specific studies in various parts of the country in combination with demographic
data on population and national, industry-specific business statistics. Management pathway estimates (including
amount landfilled) relied on various industry-specific studies, as well as facility-reported anaerobic digestion
data and state-re ported composting data.
The approach used in this analysis of deriving an estimated amount of food waste from modified GHGRP
landfilled tonnages compared to the approach employed by Facts and Figures for estimating the amount of
landfilled food waste result in significant differences in annual tonnage values as shown in the table and figure A1
below. The GHGRP data inputs are significantly larger than the EPA Facts and Figures in the most recent years.
For example, in 2018, the EPA Facts and Figures reports 35 million tons of food waste landfilled (U.S. EPA,
2020a), whereas the amount of landfilled food waste based on the GHGRP data, with the application of the waste
composition percentage of food waste comprising 24 percent of the tonnage disposed in MSW landfills, is 58
million tons.
Quantifying Methane Emissions from Landfilled Food Waste
16
-------
Table A1. Composition of food in landfilled MSW by year 1960-2020.
Overall %
food waste
Year
in MSW
Source8
1960-1969
14.8%
1990-2018 edg file from Table 4 Materials Landfilled in U.S. MSW Stream
1970-1979
11.3%
1990-2018 edg file from Table 4 Materials Landfilled in U.S. MSW Stream
1980- 1989
9.5%
1990-2018 edg file from Table 4 Materials Landfilled in U.S. MSW Stream
1990
13.6%
1990-2018 edg file from Table 4 Materials Landfilled in U.S. MSW Stream
1991
14.0%
US GHG Inventory, Chapter 6 working calc file for 1990-2019
1992
13.9%
US GHG Inventory, Chapter 6 working calc file for 1990-2020
1993
14.0%
US GHG Inventory, Chapter 6 working calc file for 1990-2021
1994
14.2%
US GHG Inventory, Chapter 6 working calc file for 1990-2022
1995
15.0%
US GHG Inventory, Chapter 6 working calc file for 1990-2023
1996
16.2%
US GHG Inventory, Chapter 6 working calc file for 1990-2024
1997
15.8%
US GHG Inventory, Chapter 6 working calc file for 1990-2025
1998
15.9%
US GHG Inventory, Chapter 6 working calc file for 1990-2026
1999
15.5%
US GHG Inventory, Chapter 6 working calc file for 1990-2027
2000
17.3%
1990-2018 edg file from Table 4 Materials Landfilled in U.S. MSW Stream
2001
17.8%
US GHG Inventory, Chapter 6 working calc file for 1990-2027
2002
17.7%
US GHG Inventory, Chapter 6 working calc file for 1990-2028
2003
18.3%
US GHG Inventory, Chapter 6 working calc file for 1990-2029
2004
18.1%
US GHG Inventory, Chapter 6 working calc file for 1990-2030
2005
18.5%
1990-2018 edg file from Table 4 Materials Landfilled in U.S. MSW Stream
2006
18.7%
US GHG Inventory, Chapter 6 working calc file for 1990-2030
2007
19.1%
US GHG Inventory, Chapter 6 working calc file for 1990-2031
2008
19.9%
US GHG Inventory, Chapter 6 working calc file for 1990-2032
2009
21.3%
US GHG Inventory, Chapter 6 working calc file for 1990-2033
2010
21.0%
1990-2018 edg file from Table 4 Materials Landfilled in U.S. MSW Stream
2011
21.3%
2012
21.0%
2013
21.0%
2014
21.7%
2015
22.0%
2016
21.9%
2017
21.8%
2018
24.1%
2019
24.1%
same as 2018 percentages
2020
24.1%
same as 2018 percentages
8 U.S. EPA. Sustainable Materials Management (SMM) - Materials and Waste Management in the United States Key Facts and Figures
https://edq.epa.gov/meta da ta/catatoa/search/resource/details.paqe?uuid=C9310A59~16D2-4002-B36B~2BQA1C637D4E
Quantifying Methane Emissions from Landfilled Food Waste
17
-------
— Facts and Figures — GHGRP-derived
tfi (/>
to c
2020
Figure A1. Comparision of estimates of food waste disposed in MSW landfills from Facts & Figures and
those reported and derived from GHGRP.
Quantifying Methane Emissions from Landfilled Food Waste
18
-------
APPENDIX B. ARCHETYPE LANDFILL PARAMETERS BASED ON LMOP DATABASE
QUERY
Archetype
ID
Criteria
Note
# of Landfills in
LMOP database
meeting criteria
Avg Landfill
Open Year
Avg Landfill
Closure Year
Total Waste in Place
(short tons)
% of waste in
place overall
1
Closure Year <1987, Landfill gas (LFG)
Collection System in Place = Yes or Shutdown
1987 is the year
RCRA permit
program was
established
61
1962
1982
265,258,326
2.08%
2
Closure Year <1987, LFG Collection System in
Place = No or Unknown
43
1962
1980
51,303,945
0.40%
3
Closure Year >=1987 and <=1996, LFG
Collection System in Place = Yes or Shutdown
1996 NSPS
federal regulations
for gas collection
were finalized
191
1967
1992
795,766,476
6.23%
4
Closure Year >=1987 and <=1996, LFG
Collection System in Place = No or Unknown
438
1973
1993
325,238,895
2.55%
5
Closure Year >1996 and <=2006, LFG
Collection System in Place = Yes or Shutdown
10-year increment
141
1972
2000
719,276,991
5.63%
6
Closure Year >1996 and <=2006, LFG
Collection System in Place = No or Unknown
175
1974
2000
113,004,184
0.88%
7
Closure Year >2006 and <=2016, LFG
Collection System in Place = Yes or Shutdown
2016 year that
NSPS regulations
for gas collection
were revised
78
1972
2011
626,202,646
4.90%
8
Closure Year >2006 and <=2016, LFG
Collection System in Place = No or Unknown
65
1977
2011
51,381,777
0.40%
9
Closure Year >2016, LFG Collection System in
Place = Yes or Shutdown
10-year increment
750
1979
2060
9,074,438,867
71.03%
10
Closure Year >2016, LFG Collection System in
Place = No or Unknown
412
1983
2067
754,288,284
5.90%
Total for All 10
Models
2354
12,776,160,391
Quantifying Methane Emissions from Landfilled Food Waste
19
-------
APPENDIX C. PORTIONING NATIONAL TONNAGE OF LANDFILLED FOOD WASTE
AMONGST THE 10 LANDFILL ARCHETYPES
Year
National Food
Waste Landfilled
Landfill Archetypes
(short tons)
#1
#2
#3
#4
#5
#6
#7
#8
#9
#10
1960
2,240,494
83.8%
16.2%
1961
2,709,591
83.8%
16.2%
1962
3,009,831
83.8%
16.2%
1963
3,295,539
83.8%
16.2%
1964
3,424,092
83.8%
16.2%
1965
4,063,917
83.8%
16.2%
1966
4,272,020
83.8%
16.2%
1967
4,426,659
23.8%
4.6%
71.5%
1968
5,191,921
23.8%
4.6%
71.5%
1969
5,371,402
23.8%
4.6%
71.5%
1970
4,986,164
23.8%
4.6%
71.5%
1971
5,506,283
23.8%
4.6%
71.5%
1972
6,397,592
10.8%
2.1%
32.4%
29.3%
25.5%
1973
11,998,049
9.5%
1.8%
28.6%
11.7%
25.8%
22.5%
1974
12,856,725
9.2%
1.8%
27.5%
11.2%
24.8%
3.9%
21.6%
1975
13,651,479
9.2%
1.8%
27.5%
11.2%
24.8%
3.9%
21.6%
1976
14,355,937
9.2%
1.8%
27.5%
11.2%
24.8%
3.9%
21.6%
1977
16,169,821
9.0%
1.7%
27.0%
11.0%
24.4%
3.8%
21.2%
1.7%
1978
17,217,522
9.0%
1.7%
27.0%
11.0%
24.4%
3.8%
21.2%
1.7%
1979
17,959,584
2.2%
0.4%
6.6%
2.7%
6.0%
0.9%
5.2%
0.4%
75.5%
1980
16,125,307
2.2%
0.4%
6.6%
2.7%
6.0%
0.9%
5.2%
0.4%
75.5%
1981
16,707,403
2.2%
6.6%
2.7%
6.0%
0.9%
5.2%
0.4%
75.8%
1982
17,123,711
2.2%
6.6%
2.7%
6.0%
0.9%
5.2%
0.4%
75.8%
1983
17,861,594
6.4%
2.6%
5.8%
0.9%
5.0%
0.4%
72.8%
6.1%
1984
18,371,039
6.4%
2.6%
5.8%
0.9%
5.0%
0.4%
72.8%
6.1%
1985
18,808,725
6.4%
2.6%
5.8%
0.9%
5.0%
0.4%
72.8%
6.1%
Quantifying Methane Emissions from Land filled Food Waste
20
-------
Year
National Food
Waste Landfilled
(short tons)
#1
#2
#3
La
#4
indfill An
#5
chetype.
#6
5
#7
#8
#9
#10
"HrST1
¦"TnT"
¦"TiTT'
1987
19,436,502
6.4%
2.6%
5.8%
0.9%
5.0%
0.4%
72.8%
6.1%
1988
19,708,723
6.4%
2.6%
5.8%
0.9%
5.0%
0.4%
72.8%
6.1%
1989
18,926,801
6.4%
2.6%
5.8%
0.9%
5.0%
0.4%
72.8%
6.1%
1990
27,300,277
6.4%
2.6%
5.8%
0.9%
5.0%
0.4%
72.8%
6.1%
1991
27,630,599
6.4%
2.6%
5.8%
0.9%
5.0%
0.4%
72.8%
6.1%
1992
27,161,674
6.4%
2.6%
5.8%
0.9%
5.0%
0.4%
72.8%
6.1%
1993
29,340,098
2.8%
6.2%
1.0%
5.4%
0.4%
77.8%
6.5%
1994
30,541,833
6.3%
1.0%
5.5%
0.5%
80.0%
6.7%
1995
32,410,830
6.3%
1.0%
5.5%
0.5%
80.0%
6.7%
1996
35,023,203
6.3%
1.0%
5.5%
0.5%
80.0%
6.7%
1997
35,022,294
6.3%
1.0%
5.5%
0.5%
80.0%
6.7%
1998
36,860,282
6.3%
1.0%
5.5%
0.5%
80.0%
6.7%
1999
39,494,975
6.3%
1.0%
5.5%
0.5%
80.0%
6.7%
2000
44,288,350
6.3%
1.0%
5.5%
0.5%
80.0%
6.7%
2001
46,250,549
6.0%
0.5%
86.4%
7.2%
2002
46,281,208
6.0%
0.5%
86.4%
7.2%
2003
42,225,256
6.0%
0.5%
86.4%
7.2%
2004
43,638,932
6.0%
0.5%
86.4%
7.2%
2005
45,319,668
6.0%
0.5%
86.4%
7.2%
2006
45,270,279
6.0%
0.5%
86.4%
7.2%
2007
45,313,558
6.0%
0.5%
86.4%
7.2%
2008
44,736,010
6.0%
0.5%
86.4%
7.2%
2009
44,518,482
6.0%
0.5%
86.4%
7.2%
2010
49,233,853
6.0%
0.5%
86.4%
7.2%
2011
46,478,244
6.0%
0.5%
86.4%
7.2%
2012
45,658,443
92.3%
7.7%
2013
45,915,014
92.3%
7.7%
2014
47,705,780
92.3%
7.7%
2015
50,596,724
92.3%
7.7%
Quantifying Methane Emissions from Land filled Food Waste
21
-------
National Food
Landfill Archetypes
Year
Waste Landfilled
(short tons)
#1
#2
#3
#4
#5
#6
#7
#8
#9
#10
"¦wrr"
¦"TTT"
2017
54,420,675
92.3%
7.7%
2018
61,385,991
92.3%
7.7%
2019
62,387,910
92.3%
7.7%
2020
62,479,750
92.3%
7.7%
Quantifying Methane Emissions from Land filled Food Waste
22
-------
APPENDIX D. GAS COLLECTION EFFICIENCY INSTALLATION
AND OPERATION SCHEDULE
Year From Waste Destruction Efficiency for
Placement
Collection Efficiency
Collected Methane
Oxidation Rate'
0
0.0%
N/A
25%
1
0.0%
N/A
25%
2
0.0%
N/A
25%
3
0.0%
N/A
25%
4
0.0%
N/A
25%
5
50.0%
99%
25%
6
50.0%
99%
25%
7
50.0%
99%
25%
8
50.0%
99%
25%
9
50.0%
99%
25%
10
75.0%
99%
25%
11
75.0%
99%
25%
12
75.0%
99%
25%
13
75.0%
99%
25%
14
75.0%
99%
25%
15
82.5%
99%
25%
16
82.5%
99%
25%
17
82.5%
99%
25%
18
82.5%
99%
25%
19
82.5%
99%
25%
20
82.5%
99%
25%
21
90%
99%
25%
22
90%
99%
25%
23
90%
99%
25%
24
90%
99%
25%
25
90%
99%
25%
26
90%
99%
25%
27
90%
99%
25%
28
90%
99%
25%
29
90%
99%
25%
30
90%
99%
25%
31
90%
99%
25%
32
90%
99%
25%
33
90%
99%
25%
34**
90%
99%
25%
35
0%
0%
25%
36-139
0%
0%
25%
An oxidation rate of 25% was used for all archetype landfills, even the five archetypes that did not have landfill
gas collection systems.
*Allows for 30 years of gas collection in the area it was installed
*Allows for 30 years of gas collection in the area it was installed
Quantifying Methane Emissions from Land filled Food Waste
23
-------
APPENDIX E. MODELED LANDFILLED FOOD WASTE EMISSION
RESULTS
Year of
Emissions
Total Methane Emissions - from Landfilled Food Waste based on GHGRP, WARM collection
efficiency scenarios
m3/yr
million metric tons C02e/yr
(GWP of methane = 25)
Methane
Generation
(m3/yr)
Methane
Emissions
-After
Collection
and
Oxidation
Methane
Emissions -
Post
Combustion
(m3/yr)
Methane
Generation
Methane
Emissions
-After
Collection
and
Oxidation
Methane
Emissions -
Post
Combustion
Total
Methane
Emissions
1990
1.784E+09
1098640816
3189969.336
30.22
18.61
0.05
18.66
1991
1.948E+09
1212249283
3314126.917
32.99
20.54
0.06
20.59
1992
2.089E+09
1309410917
3431151.867
35.39
22.18
0.06
22.24
1993
2.198E+09
1382725551
3540542.31
37.23
23.42
0.06
23.48
1994
2.325E+09
1471121352
3637858.745
39.39
24.92
0.06
24.98
1995
2.452E+09
1561118824
3701054.27
41.53
26.44
0.06
26.51
1996
2.588E+09
1640815212
4006546.004
43.85
27.79
0.07
27.86
1997
2.747E+09
1739704354
4271602.199
46.53
29.47
0.07
29.54
1998
2.878E+09
1822370380
4478785.191
48.75
30.87
0.08
30.95
1999
3.018E+09
1910053754
4710650.398
51.12
32.36
0.08
32.44
2000
3.179E+09
2012411741
4960498.313
53.86
34.09
0.08
34.17
2001
3.396E+09
2151247476
5274322.65
57.52
36.44
0.09
36.53
2002
3.609E+09
2285379673
5615893.301
61.13
38.71
0.10
38.81
2003
3.785E+09
2396889981
5895819.396
64.12
40.60
0.10
40.70
2004
3.861 E+09
2431342273
6195376.487
65.41
41.19
0.10
41.29
2005
3.949E+09
2471255104
6535511.836
66.89
41.86
0.11
41.97
2006
4.05E+09
2513751042
6981199.644
68.60
42.58
0.12
42.70
2007
4.133E+09
2542039934
7432595.892
70.01
43.06
0.13
43.19
2008
4.202E+09
2565958643
7806374.82
71.18
43.47
0.13
43.60
2009
4.249E+09
2586779992
8001612.53
71.98
43.82
0.14
43.95
2010
4.285E+09
2596617810
8223819.444
72.58
43.99
0.14
44.12
2011
4.395E+09
2659862912
8489019.972
74.46
45.06
0.14
45.20
2012
4.439E+09
2675268534
8723268.81
75.20
45.32
0.15
45.47
2013
4.462E+09
2677265048
8918318.013
75.58
45.35
0.15
45.50
2014
4.484E+09
2685329163
9038521.093
75.96
45.49
0.15
45.64
2015
4.534E+09
2714995977
9141267.301
76.81
45.99
0.15
46.15
2016
4.625E+09
2765069960
9386118.828
78.35
46.84
0.16
47.00
2017
4.728E+09
2833168924
9504932.613
80.09
47.99
0.16
48.15
2018
4.852E+09
2920563053
9578536.128
82.19
49.47
0.16
49.64
2019
5.075E+09
3083132546
9641137.704
85.97
52.23
0.16
52.39
2020
5.277E+09
3226428285
9748241.859
89.39
54.65
0.17
54.82
Quantifying Methane Emissions from Land filled Food Waste
24
-------
vvEPA
U.S. Environmental Protection Agency
Office of Research and Development
------- |