United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-92/116 December 1992
& EPA Project Summary
Landfill Gas Energy Utilization:
Technology Options and
Case Studies
Don Augenstein and John Pacey
Landfill gas, from refuse decompos-
ing in sanitary landfills, can be a fuel
for a variety of energy applications. This
report discusses technical, environmen-
tal, and other issues associated with
using landfill gas as a fuel, and pre-
sents case studies of projects in the
U.S. illustrating some common energy
uses. The full report, summarized be-
low, begins by covering basic issues
such as gas origin, composition, and
means of collection; environmental and
regulatory background is presented.
Landfill gas' properties as a fuel are
reviewed; equipment that can utilize
landfill gas is discussed. The report
then describes experience with six
projects in the U.S. where landfill gas
has been used for energy. It also refer-
ences literature on other landfill gas
energy projects of interest. Conclusions
regarding uses of landfill gas for en-
ergy are presented.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri-
angle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Gas derived from decomposing refuse
in landfills, or "landfill gas," can be fuel for
a variety of energy applications. Its uses
are currently significant, and increasing.
Because of interest from many parties con-
cerning landfill gas energy, information and
documentation of experience in several
areas of landfill gas energy uses are
needed. The report reviews the various
landfill gas energy uses, their associated
issues and constraints, and case studies
of six landfill gas energy projects in the
U.S. The report provides useful back-
ground to those interested in, and particu-
larly those implementing, landfill gas en-
ergy uses.
Landfill Gas
Most residential and municipal solid
waste in the U.S. is currently disposed of
in sanitary landfills. In landfills, a portion
of the waste organic fraction decomposes
(typically over decades) into landfill gas
containing about half methane, with the
rest carbon dioxide and smaller quantities
of other components. Because of its meth-
ane content (the same methane in pipe-
line or "natural" gas) and the quantity avail-
able, landfill gas is a significant fuel re-
source. It is currently extracted and used
for energy at an increasing number of
sites, currently over 100 in the U.S. Its
properties, and the circumstances of its
use, pose some fairly unique issues and
constraints.
Energy Applications
With appropriate allowance for its fea-
tures, landfill gas is usable in much com-
mercially available equipment that normally
uses more conventional fuels such as pipe-
line natural gas. The applications (both
current and potential) that can use it are
shown in Table 1. Also shown are esti-
mated extents to which the applications
are carried out in the U.S.
Printed on Recycled Paper
-------
Tabla 1, Landfill Gas Energy Applications
Application'
Current degree of use'
Current applications
Space heating (and cooling)
Industrial process heat
Boiler fuel
Electric generation: 1C engines
Electric generation: gas turbines
Electric generation: steam turbines
Purification for pipeline use
Potential future applications
• Electric generation using fuel cells
• Compressed methane vehicle fuel
• Synfuel or chemical feedstock
Limited
Limited
Moderate
Most common
Common
Limited
Moderate
N/A
N/A
N/A
Most significant actual or potential uses.
Statistics on use are far from complete. Defining degree of use in terms of the fraction of the total landfill gas
recovered and used for energy in the U.S., "limited" is of the order of 5%, "moderate" 5 to 20%, "common" 20% or
more, and "most common" about 50%.
Technical Considerations with
Gas Energy Uses
Specific factors and likely consequences
nood to be considered when landfill gas
(rather than more "conventional" fuels) is
used in any application. Two important
considerations common to most applica-
tions are, equipment derating, which oc-
curs because of landfill gas1 lower energy
content, and the possible effects of con-
taminants. Equipment deratings compared
to operation on pipeline gas or other fuels
are most often between 5 and 20%. This
is because of both the gas1 inert compo-
nents and also sometimes parasitic en-
ergy uses (compression). Contaminants
are present to varying levels in gas from
all landfills and can corrode equipment
and cause other problems. Because of
contaminants, gas cleanup is important;
current gas cleanup approaches have lim-
its in that some of the halogenated com-
pounds that are threats because they can
cause equipment corrosion are not easily
removed. For this and other reasons, con-
taminant- related problems remain frequent
in landfill gas energy projects. Because of
the contaminants, lower energy content,
and other factors, several design and op-
erational modifications have been devel-
oped to adapt conventional equipment to
landfill gas energy use.
Other factors are important in gas en-
ergy applications. These include whether
gas use is intermittent or continuous. Ap-
plications that can use the gas continu-
ously, such as electric generation, are the
most attractive because the gas is con-
tinuously available and there is no estab-
lished way of storing it. Several issues of
normal concern for landfill gas (such as
forecasting its recoverable quantity over
time, and collecting it efficiently) are also
key factors in using it for energy.
Environmental Issues
Energy use of landfill gas has environ-
mental consequences that can be consid-
ered predominantly beneficial. Extracting
methane mitigates migration hazards, and
emission of the landfill gas constituents.
These constituents include both non-
methane organic compounds (NMOCs) of
concern as local air pollutants, and the
methane, which is a potential contributor
to climate change ("greenhouse effect").
The energy use of methane also most
typically offsets fossil fuel use elsewhere,
reducing the emissions that would other-
wise be associated with the use of that
fossil fuel. The energy conversion equip-
ment emissions can, however, be a con-
cern; equipment must meet emission con-
straints.
Economic Factors
Cost/benefit ratios of landfill gas appli-
cations at different sites vary greatly be-
cause of high variability in costs, revenues,
and revenue-equivalent benefits. This is
partly due to site-specific factors that influ-
ence costs, and partly due to energy mar-
ket conditions, which influence revenue.
In particular available revenue from elec-
tric energy sales varies greatly from loca-
tion to location around the U.S. Energy
conversion practicality is limited by eco-
nomics at many U.S. landfill sites, includ-
ing at many of the smaller sites.
Case Studies
The case studies review landfill gas en-
ergy uses at six sites within the U.S. The
case studies are "snapshots" representing
a few of the total of U.S. landfill gas en-
ergy projects. They do, however, illustrate
experience and some benefits. The sites,
with their applications, are
1. The Brown Station Road Landfill,
Prince George's County, Maryland.
At this facility, the landfill gas is used
to fuel electric power, space heat-
ing, and hot water provided to a
very large county building complex.
Surplus electric power generated is
vended to the local utility grid.
—2. The Qtay Landfill, San Diego,--Cali-
fornia. At this site a Cooper-Supe-
rior* internal combustion (1C) engine
powered generator provides electri-
cal power for export sale to the local
utility grid.
3. The Marina Landfill, Marina, Califor-
nia. At this site two Waukesha 1C
engine powered generators produce
electrical power for export sale to
the utility grid. The facility was one
of the first to be implemented and is
one of the longest running in the
U.S.
4. The Sycamore Canyon site, San Di-
ego, California. This site illustrates
the use of Solar combustion gas tur-
bines to power generation of elec-
tricity for sale to the local utility grid.
5. A site in Raleigh, North Carolina,
where landfill gas is pipelined 3/4-
mile (1.2 km) to a local pharmaceuti-
cal plant. It fuels a Cleaver-Brooks
boiler at the plant that provides most
of the plant process steam needs.
6. A site in-Yolo County, California,
where landfill gas fuels three Cater-
pillar engines that power electric gen-
eration for sale to the local utility.
The case study applications reflect that
1C engine and gas turbine powered elec-
tric generators are the most common ap-
plications of landfill gas energy. A space-
heat and steam-generation project are also
included in the case studies. These case
study applications are considered to be
among the more attractive candidate ap-
proaches for future sites.
Though case studies cover only six
projects, the spectrum of experience is
indicative of the variety and site specificity
of U.S. landfill gas energy projects. Two
projects (1 and 6 above) experienced se-
rious and unforeseen problems at one or
* Mention of trade names or commercial products
does not constitute endorsement or recommendation
for use.
-------
more times. Two projects (2 and 5 above)
appear to have done well since inception.
The other .two do well technically but eco-
nomic performance has not been as good
as technical performance because of low
electric revenue.
The details and complexities of imple-
menting several projects (sites_1, 3, 5,
and 6) may be of particular interest to
others contemplating energy uses.
Conclusions
Based on this study, important conclu-
sions include:
• Landfill gas can be a satisfactory
fuel for a wide variety of applica-
tions, and its use in these applica-
tions provides environmental and
conservation benefits. Many types
of energy equipment that operate on
more "conventional" fuels can also
operate on landfill gas.
• Some reduction in the energy output
of conventional equipment, about 5
to 20 percent compared to output on
conventional fuels, is normally asso-
ciated with landfill gas use.
• When landfill gas is used as a fuel,
its properties and unique nature, and
particularly its contaminants, must be
considered. Many pitfalls are pos-
sible in landfill gas energy applica-
tions. Especially important are equip-
ment damage caused by the gas
contaminants, and gas supply prob-
lems such as shortages resulting
from incorrectly forecasting the avail-
ability of the gas.
Cleanup stringency and methods
vary widely. The necessary degree
of landfill gas cleanup has not been
well established. Cleanup is often
expensive, both economically and in
energy requirements.
• The optimum tradeoffs between
cleanup stringency and the frequency
of maintenance, such as oil changes,
are not well established.
• Collection technologies are devel-
oped but probably could be further
improved.
• Methods of forecasting gas availabil-
ity for new sites are available but
could be improved.
• Economics vary greatly; at some
sites, economics may be excellent
._ .. but at Bothers, economics are_a_ ma-,
jor limitation. Economics now tend
to preclude smaller scale and re-
mote site uses where electric power
sale prices are low and there are no-
other convenient energy applications.
• Emission limits in some U.S. loca-
tions may also inhibit landfill gas en-
ergy uses despite an environmental
balance sheet that would generally
appear to be strongly positive.
Further Needs
Based on this project's work and cited
literature, further needs regarding landfill
gas energy use appear to include:
Examining ways to improve and stan-
dardize gas cleanup for specific ap-
plications.
• Examining further the tradeoffs be-
tween approaches such as more
stringent gas cleanup and mainte-
nance measures such as more fre-
quent oil changes.
• Examining further optimum operat-
ing parameters, such as the best oil,
coolant, and exhaust gas tempera-
ture.
• Examining further and documenting
appropriate engine and other equip-
ment design modifications to reduce
current contaminant-related problems
experienced with landfill gas use.
• Improving technology in ancillary ar-
eas that relate to energy uses such
as forecasting gas recoverability and
improving gas collection efficiency
and reliability.
•_ _ Developing and improving economic
small-scale uses for the landfill gas.
• Developing further detailed docu-
mentation of experienced problems,
and attempted and successful solu-
tions to them, to benefit the commu-
nity of present and future landfill gas
users.
• Examining ways to reduce economic
(and institutional) barriers to landfill
gas energy applications.
Technical improvements, in the areas
referred to above, should help advance
landfill gas energy use. In addition, incen-
tives and other approaches are possible
that may help to reduce the nontechnical
barriers to landfill gas energy use.
•U.S. Government Printing Office: 1993 — 750-071/60174
-------
D, Augenstein andJ. Paceyare with EMCON Associates, San Jose, CA 95131.
Susan A, Thorneloe is the EPA Project Officer (see below).
The complete report, entitled "Landfill Gas Energy Utilization: Technology Options
and Case Studies," (Order No. PB92-203116/AS; Cost: $27.00; subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 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
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-92/116
------- |