United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S7-91/002 Apr. 1991
vxEPA Project Summary
Approach for Estimating Global
Landfill Methane Emissions
R.L. Peer, A.E. Leininger, B.B. Emmel, and S.K. Lynch
This report is an overview of avail-
able country-specific data and modeling
approaches for estimating global land-
fill methane. Current estimates of global
landfill methane indicate that landfills
account for between 4 and 15% of the
global methane budget. The report de-
scribes an approach for using country-
specific and field test data to develop a
less uncertain estimate of global landfill
methane. Development of enhanced
emissions factors for landfills and other
major sources of methane will improve
the understanding of atmospheric
chemistry and feedback effects, will
target mitigation opportunities, and will
ensure cost-effective mitigation strate-
gies.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
In response to concerns about global
warming, the U.S. EPA's Office of Re-
search and Development (ORD) has initi-
ated a program to characterize the effects
of global change, including identifying and
quantifying emission sources. EPA's Air
and Energy Engineering Research Labo-
ratory (AEERL) is part of this effort, and is
particularly concerned with quantifying
emissions sources both in the U.S. and
globally.
Considerable effort has been expended
studying carbon dioxide (CO2) emissions
since CO2 is responsible for most of the
global warming. Methane is of particular
concern since its radiative forcing potential
has been estimated to be 20 to 30 times
that of CO2 on a mole basis; furthermore,
atmospheric methane is increasing at a
faster rate than any other greenhouse gas
except for chlorofluorocarbons. Although
the major sources of methane are known
qualitatively, considerable uncertainty ex-
ists about the quantitative emissions from
each source. One of the goals of AEERL's
global climate research program is to de-
velop enhanced emission factors for
methane sources. This will improve the
understanding of atmospheric chemistry
and feedback effects, will target mitigation
opportunities, and will ensure cost-effective
mitigation strategies.
The current state of knowledge for
landfills—a major source of methane—is
summarized in this report. The report pro-
vides an evaluation of the approaches cur-
rently available for estimating global land-
fill methane. The report also provides an
overview of data from current literature on
methanogenesis in landfills, an evaluation
of methane emission models, and inter-
views with experts in this field. An approach
is identified using country-specific and field
test data for reducing the uncertainty as-
sociated with current estimates of global
emissions of landfill methane.
The best approach is obviously deter-
mined by a variety of factors including the
desired level of accuracy, desired resolu-
tion, data limitations, and budget and time
constraints. The level of accuracy is largely
Printed on Recycled Paper
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determined by the needs of the users of
the model outputs which have widely
varying needs. Policymakers need quanti-
tative measures of landfill emissions in
order to develop mitigation strategies and
to assign priorities to mitigation programs.
However, they may need only one num-
ber, such as average annual global meth-
ane emissions from a given source; the
finest resolution they may need is likely to
be at the country-specific level. At the other
end of the spectrum are the outputs needed
to supply information to regional and global
atmospheric models. If so, the resolution
of the data will need to be finer. Spatially,
the emissions may be needed for grid cells
as large as 10°x10° or as small as 1°x1°.
Temporally, time periods of less than a
year may be desirable.
At this time, rt is recognized that these
divergent needs exist, and rt is not certain
that the needs of all users can be met. The
limitations to meeting all these needs are
partly related to the costs of model devel-
opment. Even more critical, however, is
the large amount of uncertainty associated
with modeling methanogenesis. Cost con-
siderations aside, the data required as in-
puts for a mechanistic model of methane
production may not exist. These consider-
ations have been taken into account in
developing a model for estimating global
landfill methane.
The report summarizes conclusions and
recommendations of this study, discusses
several different modeling approaches that
are currently available, discusses data
needs and availability, presents a concep-
tual scheme for a global landfills model,
and outlines a program to develop that
model further.
R.L Peer, A.E. Leininger, B.B. Em met, and S.K. Lynch are with Radian Corp.,
Research Triangle Park, NC 27709.
Susan A. Throneloe is the EPA Project Officer (see below).
The complete report, entitled "Approach for Estimating Global Landfill Methane
Emissions,"(Order No. PB91-149534/AS; Cost: $17.00, subject to change) will
be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, v'A 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
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EPA/600/S7-91/002
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