Life-Cycle Evaluation of Greenhouse Gas
Emissions From Municipal Solid Waste
Management in the United States
Susan A. Thorneloe*, Keith A. Weitz**, Subba R. Nishtala**, and Maria
Zannes***
*Air Pollution Prevention and Control Division, Office of Research and
Development, U.S. Environmental Protection Agency, Research Triangle Park,
North Carolina
** Center for Environmental Analysis, Research Triangle Institute,
Research Triangle Park, North Carolina
***Integrated Waste Services Association, Washington, District of Columbia
SUMMARY: Adopting integrated waste management practices, which include increased
recycling, composting, landfill gas control, and waste-to-energy, has led to a substantial
reduction of greenhouse gas (GHG) emissions in the United States. A recently completed
decision support tool using a life-cycle evaluation was used to evaluate the trends in GHG
emissions for waste management practices in the 1970s versus current practices. This paper
provides a brief overview of this study and the results.
I. INTRODUCTION
Through funding by the United States Environmental Protection Agency (EPA), a municipal
solid waste decision support tool (MSW-DST) has been developed. The MSW-DST was the
result of more than 6 years of research including detailed data collection and software
development. A very rigorous review of the outputs, including extensive project documentation,
Life-Cycle Inventory (LCI) Database for North America, and the MSW-DST, was conducted.
This included close interaction with more than 80 stakeholders representing: (1) state and local
government, (2) environmental interest groups and other non-governmental organizations, (3)
solid waste management industry, (4) aluminum, glass, paper, plastic, and steel industries, (5)
academia, and (6) the public. In addition, three external program peer reviews were conducted
with international experts. The goal was to develop a credible, objective, state-of-the-art tool
that can be used to make more informed choices regarding solid waste management. (Thorneloe
et al, 1999b, Barlaz et al, 1999b) Based on comments from the reviewers, stakeholders, and
ongoing case studies, this has been successfully accomplished.

-------
The MSW-DST and LCI Database were developed through a competed cooperative
agreement between EPA and the Research Triangle Institute (RTI) (CR 823052). In order to
conduct this research, RTI formed a research team of life-cycle practitioners and solid waste
management experts from North Carolina State University, University of Wisconsin at Madison,
Franklin Associates, and Roy F. Weston, Inc. The extensive work to develop the LCI model for
MSW landfills was conducted through funding provided by the Environmental Research and
Education Foundation (EREF). The development of the LCI model for landfills was reviewed in
a paper at Sardinia 99 (Barlaz et al., 1999b). The research team has accomplished the goals of
the cooperative agreement. In addition to EPA and EREF funding, the U.S. Department of
Energy also provided cofunding which was devoted to data collection and analysis.
Currently, the MSW-DST and LCI database are being used in a variety of case studies. A
companion paper describes the various case studies being conducted which help to illustrate how
these tools can be appropriately used. The subject of this paper is our analysis of GHG trends
associated with MSW management in the United States. We used data for the waste
composition, quantity, and management practices for the 1970s and for today. The study was
completed in November 2000 for presentation at the Annual Fall Summit of the U.S. Conference
of Mayors' Municipal Waste Management Association, held in Tacoma, Washington, on
November 15 - 17, 2000. The results from the study indicated that a substantial reduction of
GHG emissions has occurred since the 1970s. This paper provides a brief description of the
study and its results. A more detailed paper documenting this study has been accepted for
publication in the Air and Waste Management Association Journal.
2. METHODOLOGY
The solid waste management industry, through funding by the Integrated Waste Management
Association, initiated this study to evaluate GHG trends in the U.S. Participants in this study
were (1) U.S. Conference of Mayors, (2) Integrated Waste Services Association, (3) RTI, (4)
U.S. EPA, (5) ICF Consulting, (6) Solid Waste Association of North America, (7) Environmental
Industry Associations, and (8) Waste Management, Inc. EPA's Office of Research and
Development (ORD) directed this research and worked cooperatively with EPA's Office of Solid
Waste. RTI was responsible for conducting the study which provided an opportunity to evaluate
the application of the MSW-DST on a national scale.
The methodology for the MSW-DST is based on a life-cycle evaluation of the full range
of multimedia and multipollutant burdens and/or benefits associated with waste management.
For materials recovered from the waste stream, credit is included for the conservation of virgin
resources. For energy, LCI environmental burdens associated with both consumption and
generation (e.g., extraction of oil, production of gasoline) are included. For energy produced
through utilization of landfill gas and combustion of waste, offsets are also included. All GHG
emissions are reported in carbon equivalents. For all waste management activities, except for
landfills, the GHG emissions are instantaneous (e.g., generation and/or combustion of fuel). For
landfills, total emissions resulting from landfilled waste are calculated over a 100-year time
frame for the quantity of waste managed for the 2 years being compared. Also note that the
MSW-DST provides information on a multimedia, multipollutant basis. However, study
participants were interested only in the estimates of GHG emissions to help in evaluating trends.
2

-------
2.1 Data Used for Conducting the Study
EPA's Office of Solid Waste reports annual estimates of the quantity and composition of MSW.
This annual report also provides information on how this waste is being managed (EPA, July
1999), The web site provides this report as well as other documentation (EPA, 1999). The
earliest set of data for MSW management was for 1974 which was used as the base year for this
study (Franklin Associates, 2000). The base year of 1974 is representative of management
practices and the technology mix used in the 1970s. The most recent year that comprehensive
data were available was 1997. However, where more recent data such as the recycling rates for
1999 are available, they were used. The amount of MSW generated in the U.S. increased from
115 million metric tons in 1974 to 197 million metric tons in 1997 (Franklin Associates, 2000;
EPA, 1999).
Figures 1 and 2 provide the technology mix for waste management practices in 1974 and
1997, respectively. Figure 3 compares waste management in 1974 to that in 1997. Since the
1970s, the U.S. has moved toward integrated waste management, has adopted a more diverse
mix of technologies, and has increased the recycling rate from 7 to 28%. There have also been
programs to encourage source reduction and to divert waste from landfills. There is much better
control of landfill gas as a result of energy recovery projects as well as Clean Air Act regulations
that require large landfills (containing more than 2.5 million metric tons of MSW) to collect and
control landfill gas. For further information on these requirements, refer to EPA, 1996.
Currently, about 300 landfills in the U.S. utilize landfill gas for energy recovery projects through
either direct gas use or production of electricity. Also, about 15% of MSW in the U.S. is
managed through waste-to-energy facilities which recover metals and generate electricity (Kane,
1995).
93%
7%
Mixed Waste
Collection
Landfill Without
Gas Control
Presorted
Material
Recovery
Facility
Presorted
Recyclables
Collection
Materials to Reprocessing
Figure 1 - Waste Management Scenario in 1974
3

-------
Yard Waste
5%

Yard Waste
Collection

Composting
Mixed Waste
Collection
57%
15%
Combustion
with Energy
Recovery
Landfill with
Gas Control
and Energy
Recovery
¦+» Ash Landfill
Presorted
Recyclables
Collection
23%
Presorted
Material
Recovery
Facility




r
Materials to Reprocessing
Figure 2 - Waste Management Scenario Today
1974
Today
H Recycling
H Waste-to-Eriergy
I I Landfill
28%
57%
15%
Figure 3 - Past and Present Technologies Used to Manage U.S. Waste Generated
(Note: Most Recent U.S. Statistics Indicate Recycling is at 23% and Composting is at 5%.)
4

-------
2.2 Sources of GHG Emissions from MSW Management
Table 1 lists sources of GHG emissions from waste management. Estimates were developed for
methane (CH4) and carbon dioxide (CO2). Due to limitations in available data for
perfluorocarbons (PFCs) and nitrous oxide (N20), these pollutants were not included in this
analysis. Using guidance from the International Panel on Climate Change, methane was
converted to carbon equivalents using a global warming potential of 21 (EPA, April 2000). As
stated earlier, all GHG emissions were calculated throughout the life cycle. For energy, this
includes the GHG emissions for the consumption as well as the production (e.g., emissions while
diesel truck is being operated and emissions from the production of diesel fuel). For electricity
produced from landfill gas utilization or waste-to-energy, emissions savings were calculated
based on offsetting the national electric grid.
Table 1 - Sources and Savings of GHG Emissions from MSW
Management-Related Technologies Included in the Analysis
Waste Management Activity or
Process
GHG Emissions (CH4 and CO2 fossil) Sources
Collection (recyclables and mixed
waste)
Combustion of diesel fuel in collection vehicles
Production of diesel fuel and electricity (used in garage)
Material Recovery Facilities
Combustion of diesel fuel used for rolling stock (front-
end loaders, etc.)
Production of diesel fuel and electricity (used in
building and for equipment)

Yard Waste Composting Facility
Combustion of diesel fuel used for rolling stock
Production of diesel fuel and electricity (used for
equipment)
Combustion (waste-to-energy)
Combustion of waste
Offsets from electricity produced
Landfill
Decomposition of waste
Combustion of diesel fuel used for rolling stock
Production of diesel fuel
Offsets from electricity produced
Transportation
Combustion of diesel fuel used for vehicles
Production of diesel
Reprocessing of Recyclables
Offsets (net gains or decreases) from reprocessing
recyclables recovered; offsets include energy- and
process-related data
5

-------
3. RESULTS AND DISCUSSION
Table 2 provides the estimate of GHG emissions for (1) collection and transportation,
(2) recycling/composting, (3) waste-to-energy or MSW combustion, and (4) landfilling.
Columns A and B represent the estimate of GHG emissions in 1974 and 1997 for the respective
waste quantity, composition, and management practices. Since the 1970s, there is a more
diverse technology mix as well as advancements in landfill technology. There is more
integration of waste management which has resulted in efficiencies that have reduced
environmental burdens and cost.
Column C of Table 2 estimates the quantity of GHG emissions that would be emitted today if we
still relied on the same management practices and technology mix that we used in 1974. As you
can see, 51 million metric tons of carbon equivalents (MMTCE) would result from the amount of
MSW that we now manage if we still used the same technology mix and management practices
from the 1970s. Column C - B presents the estimate of GHG emissions that have been avoided
as the result of improved waste management practices and greater utilization of more advanced
and efficient technologies. Approximately 41 MMTCE are avoided as the result of landfill gas
control, utilization of landfill gas and use of waste-to-energy facilities, and recycling. Figure 4
presents these results, comparing the current technology path and that used in 1974.
Table 2 - GHG Emissions From U.S. Waste Management (MMTCE/year)

GHG Equivalents
Waste Management Technology
1974
(A)
1997
(B)
1997
with 1974
Technology
(C)
Avoided
GHG
Emissions
(C-B)
Collection/Transportation
0.5
1
1
0
Recycling/Composting
-1
-7
-3
4
Waste-to-Energy/MSW Combustion
0
-5
0
5a
Landfilling
36
21
53
32
Total
35
10
51
41
aIf avoided landfill GHG emissions are also included in the analysis, then the total avoided GHG emissions from
waste-to-energy combustion would be approximately 11 MMTCE.
6

-------
60
~ Net GHG Emissions
50
1974 Technology Path
40
41 MMTCE
Avoided
30
20
Actual Integrated Waste
Management Technology Path
10
0 —
1970
1980
1985
1990
1995
1975
2000
Year
Figure 4 - Comparison of Net GHG Emissions for MSW Management
3.1	Results for Recycling
In 1974, ~8 MMT (7% of our waste stream) was being recycled. Today, 28% of our MSW is
recycled (i.e., 53 MMT), which avoids 4 MMTCE. These estimates include GHG emissions
associated with (1) materials separations and reprocessing and (2) GHG emissions from the
operation of composting facilities. The offsets that were used for recycling of more than 20
components in MSW (e.g., aluminum and steel cans, glass containers, plastics, newsprint,
corrugated containers, phone books) are documented in a report that provides the LCI for
manufacturing different products using "virgin" resources versus materials recovered in our
waste stream. Availability of this document and the resulting database for North America,
including the data for the production and consumption of different fuels for the national grid and
regional grids, can be found on the project web site (RTI, 2000). Recycling and composting also
divert waste from landfills. If this waste were managed as it was in 1974, there would be
increased emissions of CH4, a very potent GHG.
3.2	Results for Waste-to-energy (or MSW Combustion)
This technology reduces GHG emissions through the production of electrical energy which in the
U.S. typically results in displacing fossil-fuel-fired power plants. In addition, diverting waste
from landfills helps to avoid CH4. The offset from energy production is quite significant since,
for the same unit of energy, the combustion of coal produces a greater quantity of GHG
emissions.
In 1974, there were no operating waste-to-energy facilities in the U.S. Currently, 29
million metric tons of MSW or -15% is managed through this technology resulting in avoiding
7

-------
-5 MMTCE. If the amount of waste going to waste-to-energy facilities in 1997 were managed
as it was in 1974, an additional 6 MMTCE would be generated. Therefore, the total quantity of
GHG emissions avoided through the use of waste-to-energy is ~11 MMTCE.
3.3	Results for Landfills
Approximately 57 % or 129 MMT of MSW and combustion ash is landfilled. In 1974, 108
MMT of MSW was landfilled. Landfills with gas collection and control systems reduce the
quantity of GHG emissions released that result from the decomposition of waste. Current Clean
Air Act regulations require "large" landfills to collect and control the gas that results from the
decomposition of waste. Many of these sites flare (i.e., combust) the gas. However, about 300
landfill gas-to-energy projects today (versus zero in 1974) utilize the landfill CH4. These
projects include direct gas use and electricity generation using internal combustion engines and
turbines. For these sites, an additional GHG reduction is associated with conservation of fossil
fuel We used the mix of energy technologies in place to calculate the resulting offset. We also
used a 100-year time horizon to calculate the total emissions associated with the landfilling of
MSW in 1974 and 1997. As you can see from Table 2, 32 MMTCE are avoided which
represents -80% of the total reductions avoided through use of improved technology and
management practices.
3.4	Collection and Transportation
Collection and transportation of MSW accounted for -0.5 and 0.9 MMTCE in 1974 and 1997,
respectively. This is the only activity where we have seen an increase in GHG emissions. This
is due to the increased volume of waste (115 to 197 MMT) as well as increases due to waste
separation and collection programs for recycling and composting. With increased emissions
from collection and transportation, emissions of sulfur oxides, nitrogen oxides, carbon
monoxide, ozone, and particulate must be considered. For those regions in non-attainment status
for what we call "Criteria Pollutants" in the U.S., we recommend using a multipollutant,
multimedia analysis which the MSW-DST has the capability to provide before making policy
decisions. This helps to avoid trading off one environmental problem for another.
4. CONCLUSIONS
Since 1974, the U.S. has moved away from simply landfilling waste in uncontrolled sites.
Through the use of integrated waste management, recycling/composting, waste-to-energy, and
better control of landfill gas, communities across the U.S. are avoiding -41 MMTCE of GHG
emissions per year. The total quantity of GHG emissions from MSW management was reduced
by a factor of 5 (51 to 10 MMTCE) from what it otherwise would have been, despite a more than
70% increase of MSW. This study found that there has been a positive impact on GHG
emissions as a result of actions taken by local governments managing MSW. There are
additional opportunities for further reductions, but it is important to take into account any
potential tradeoffs with other pollutants by considering multimedia and multipollutant impacts.
Although not presented in this paper, the potential carbon that is stored (not released to the
atmosphere) was also calculated. The results are directionally similar, but the magnitude of the
8

-------
numbers varies substantially. GHG reductions have also been calculated for a number of
communities, providing information on the current level of GHG emissions and opportunities for
further reductions. Although the MSW-DST was developed for assisting primarily with local
decision making, it was concluded that the MSW-DST was also of benefit in helping to evaluate
national trends in GHG emissions associated with MSW management.
ACKNOWLEDGEMENTS
The authors wish to thank the participants in this study for providing data and information and
reviewing interim drafts. We also would like to thank the U.S. Conference of Mayors for their
efforts to better understand trends in GHG emissions from MSW management and promoting
sustainable solutions for finding improved environmental performance.
REFERENCES
Barlaz M.A., Camobreco V., Repa E., Ham R.K., Felker M., Rousseau C, Rathle J., (1999a)
Life-Cycle Inventoryof a Modern Municipal Solid Waste Landfill, Sardinia 99, Seventh
International Waste Management and Landfill Symposium, Published in Proceedings, Volume
III, Pages 337-344, October 4-8, 1999.
Barlaz M.A., Ranjithan S.R., Brill E.D. Jr., Dumas R.D., Harrison K.W., Solano E., (1999b)
Development of Alternative Solid Waste Management Options: A Mathematical Modeling
Approach, Sardinia 99, Seventh International Waste Management and Landfill
Symposium, Published in Proceedings, Volume I, Pages 25-32, October 4-8, 1999.
Franklin Associates, Limited. Prairie Village, KS. Unpublished 1974 waste characterization data
supplied though personal communication with Marge Franklin, March 2000.
Kane, C., Radian Corporation, Research Triangle Park, NC. Memorandum to Walt Stevenson,
U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards,
Combustion Group. "Summary of Performance Data from Twelve Municipal Waste
Combustor Units with Spray Dryer/Fabric Fiiter/SNCR/Carbon Injection Controls." October
17, 1995.
Research Triangle Institute. Pollution Prevention. Life Cycle Management of
Municipal Solid Waste, http://www.rti.0rg/units/ese/p2/lca.cfrn#life (accessed September
2000).
Thorneloe, S.A., Roqueta, A., Pacey, J., Bottero, C, (1999a) Database of Landfill Gas to Energy
Projects in the United States; Sardinia 99, Seventh International Waste Management and
Landfill Symposium, Published in Proceedings, Volume II, Pages 525-533, October 4-8, 1999.
Thorneloe, S.A., Weitz K., Barlaz, M., Ham, R.K., (1999b) Tools for Determining Sustainable
Waste Management Through Application of Life-Cycle Assessment: Update on U.S.
Research, Sardinia 99, Seventh International Waste Management and Landfill Symposium,
Published in Proceedings, Volume V, Pages 629-636, October 4-8, 1999.
U.S. Environmental Protection Agency. Inventory of U.S. Greenhouse Gas Emissions and Sinks:
1990-1998; EPA 236-R-0G-001, NTIS PB2000-100397; Office of Policy, Planning, and
Evaluation: Washington, DC, April 2000.
9

-------
U.S. Environmental Protection Agency. Characterization of Municipal Solid Waste in the United
States: 1998 Update; EPA 530-R-99-021; Office of Solid Waste and Emergency Response:
Washington, DC, July 1999, http://www.epa.gov/epaoswer/osw/index.htm.
U.S. Environmental Protection Agency, "Standards of Performance for New Stationary Sources
and Guidelines for Controls of Existing Sources, Municipal Solid Waste Landfills", Final Rule
and Guidelines, 61 Federal Register 49, 1996. Pages 9905-9944, March 12, 1996,
http ://w w w.epa. go v/ttn/atw/landfill/landflp g. html.
10

-------
TECHNICAL REPORT DATA
N RM RL~ RT P P- 615 (Please read Instructions on the reverse before complef
1. REPORT NO. 2.
EPA/600/A-01/113
3. RECI
4, TITLE AND SUBTITLE
Life-cycle Evaluation of Greenhouse Gas Emissions
from Municipal Solid Waste Management in the
United States
5. REPORT DA 1 fc
6. PERFORMING ORGANIZATION CODE
7.authors s.Thorneloe (EPA), K. Weitz and S. Nishtala
(RTI), and M.Zannes (IWSA)
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Research Triangle Institute Integrated Waste Services
P.O.Box 12194 Association
RTP. NC 27709 "01 H Street> NW
Washington, DC 2005
10, PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
NA
12 SPONSORING AGENCY NAME AND ADDRESS
U. S. EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper;
14. SPONSORING AGENCY CODE
EPA/600/13
15 supplementarynotes^pp^jq project officer is Susan A. Thorneloe, Mail Drop 63, 919/541-
2709. For presentation at 8th Int. Waste Management and Landfill Conference,
Cagiiari, Sardinia, Italy, 10/1-5/01.
16. ABSTRACT paper discusses a life-cycle evaluation of greenhouse gas (GHG) emis-
sions from municipal solid waste (MSW) management in the U.S. (NOTE: Using
integrated waste management, recycling/composting, waste-to-energy, and better
control of landfill gas, communities across the U.S. are avoiding about 41 million
metric tons of carbon equivalents (MMTCE) of GHG emissions. The total quantity of
GHG emissions from MSW management was reduced by a factor of 5 (51 to 10 MMTCE)
from what it otherwise would have been, despite a more than 70% increase of MSW.)
The evaluation found that there has been a positive impact on GHG emissions as a
result of actions taken by local governments managing MSW. There are additional
opportunities for further reductions, but it is important to take into account any po-
tential tradeoffs with other pollutants by considering multimedia and multipollutant
impacts. Although not presented in the paper, the potential carbon that is stored (not
released to the atmosphere) was also calculated. The results are directionally simi-
lar, but the magnitude of the numbers varies substantially. GHG reductions have also
been calculated for a number of communities, providing information on the current
level of GHG emissions and opportunities for further reductions.
17 KEY WORDS AND DOCUMENT ANALYSIS
a DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
C, COSATI Field/Group
Pollution Evaluation
Greenhouse Effect Life
Gases Carbon
Emission
Wastes
Management
Pollution Control
Stationary Sources
13 B
04A
07D
14G
05A
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report)
21. NO. OF PAGES
20. SECURITY CLASS (This Page)
22. PRICE
EPA Form 2220-1 (Rev. 4-77 ) PREVIOUS EDITION IS OBSOLETE	forros/admin/techrpt frm 7/8/99 pad

-------