United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/SR-92/007 Feb. 1992
& EPA Project Summary
Demonstration of Fuel Cells to
Recover Energy from Landfill
Gas: Phase I Final Report:
Conceptual Study
G. J. Sandelli
International Fuel Cells Corporation
is conducting a U.S. EPA-sponsored
program to demonstrate energy recov-
ery from landfill gas using a commer-
cial phosphoric acid fuel cell power
plant. The U.S. EPA Is Interested in
fuel cells for this application because
it is potentially one of the cleanest
energy conversion technologies avail-
able. The report discusses the results
of Phase I, a conceptual design, cost,
and evaluation study. The conceptual
design of the fuel cell energy recovery
concept is described and its economic
and environmental feasibility is pro-
jected. A preliminary design of the
project demonstration was established
from the commercial concept. It ad-
dresses the key demonstration issues
facing commercialization of the con-
cept. Candidate demonstration sites
were evaluated, which led to selection
and EPA approval of the demonstra-
tion site.
A plan for Phase II activities is dis-
cussed. Phase II will include construc-
tion and testing of a landfill gas
pretreatment system which will render
landfill gas suitable for use in the fuel
cell. Phase III will be demonstration of
the energy recovery concept.
This Project Summary was devel-
oped by EPA's Air and Energy Engi-
neering Research Laboratory, Research
Triangle 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
The U.S. Environmental Protection
Agency (EPA) has proposed standards and
guidelines for the control of air emissions
from municipal solid waste landfills. Al-
though not directly controlled under the
proposal, the collection and disposal of
waste methane, a significant contributor to
the greenhouse effect, would result from
the emission regulations. This EPA action
will provide an opportunity for energy re-
covery from the waste methane that could
further benefit the environment. Energy
produced from landfill gas could offset the
use of foreign oil, and air emissions affect-
ing global warming, acid rain, and other
health and environmental issues.
International Fuel Cells Corporation
(IFC) was awarded a contract by the U.S.
EPA to demonstrate energy recovery from
landfill gas using a commercial phosphoric
acid fuel cell. IFC is conducting a three-
phase program to show that fuel cell en-
ergy recovery is economically and
environmentally feasible in commercial
operation. Work was initiated in January
1991. The project report discusses the
results of Phase I, a conceptual design,
cost, and evaluation study, which ad-
dressed the problems associated with land-
fill gas as the feedstock for fuel cell
operation.
Phase II of the program includes con-
struction and testing of the landfill gas
pretreatment module to be used in the
demonstration. Its objective will be to de-
termine the effectiveness of the pretreat-
ment system design to remove critical fuel
cell catalyst poisons such as sulfur and
Printed on Recycled Paper
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halkies. A challenge test is planned to
show the feasibility of using the pretreat-
ment process at any landfill in conjunction
with the fuel cell energy recovery concept.
A preliminary description of the gas
pretreater is presented.
Phase III of the program will be demon-
stration of the fuel cell energy recovery
concept. The demonstrator will operate at
Panrose Station, an existing landfill gas-
to-enargy facility owned by Pacific Energy
in Sun Valley, California. Penrose Station
is an 8.9 MW internal combustion engine
facility supplied with landfill gas from four
landfills. The electricity produced by the
demonstration will be sold to the electric
utility grid.
Phase II activities began in September
1991, and Phase III activities are sched-
uled to begin in January 1993.
Commercial Fuel Cell Landfill
Gas to Energy System
Conceptual Design
A commercial fuel cell landfill gas to
energy system concept was designed to
provide a modular, packaged, energy con-
version system which can operate on land-
fill gases with a wide range of composi-
tions as typically found in the United States.
The complete system incorporates the land-
fill gas collection system, a fuel gas pre-
treatment system, and a fuel cell energy
conversion system. In the fuel gas pre-
treatment system, the raw landfill gas is
treated to remove contaminants to a level
suitable for the fuel cell energy conversion
system. The fuel cell energy conversion
system converts the treated gas to elec-
tricity and useful heat.
Landfill gas collection systems are pres-
ently in use in over 100 landfills in the
United States. These systems have been
proven effective for the collection of landfill
gas. Therefore these design and evalua-
tion studies were focused on the energy
conversion concept.
Overall System Description
The commercial landfill gas to energy
conversion system is illustrated in Figure
1. The fuel pretreatment system has provi-
sions for handling a wide range of gas
contaminants. Multiple pretreatment mod-
ules can be used to accommodate a wide
range of landfill sizes. The wells and col-
lection system collect the raw landfill gas
and deliver it at approximately ambient
pressure to the gas pretreatment system.
In the gas pretreatment system the gas is
treated to remove non-methane organic
compounds (NMOCs) including trace con-
stituents which contain halogen and sulfur
compounds.
The commercial energy conversion sys-
tem shown in Rgure 1 consists of four fuel
cell power plants. These power plants are
designed to provide 200 kW output when
operating on landfill gas with a heating
value of 500 Btu/scf.* The output from the
fuel cell is utility grade ac electric power. It
can be transformed and put into the elec-
tric grid, used directly at nearby facilities,
or used at the landfill itself. The power
plants are capable of recovering cogen-
eration heat for nearby use or rejecting it to
air.
'1 Btu/scf. 37.3 kJ/sm*
Landfill Gas Wells and
Collection System
Transformer
Collection Syt
•«*•> • •, MIMM t*««"^V
Utility
Grid
\
Multiple Fuel Cell
Power Plants
Landfill Site
Office and
Blower
Gas Pretreatment
System
Figure 1. Fuel cell energy recovery commercial concept
-------
As configured in Figure 1. the commer-
cial system can process approximately
18,000 scf/h* of landfill gas (mitigate 9050
scf/h of methane) with minimum environ-
mental impact in terms of liquids, solids, or
air pollution.
Fuel Pretreatment System
The fuel pretreatment system incorpo-
rates two stages of refrigeration combined
with three regenerable adsorbent steps.
The use of staged refrigeration provides
tolerance to varying landfill gas constitu-
ents. The first stage significantly reduces
the water content and removes the bulk of
the heavier hydrocarbons from the landfill
gas. This step provides flexibility to accom-
modate varying landfill characteristics by
delivering a relatively narrow cut of hydro-
carbons for the downstream beds in the
pretreatment system. The second refrig-
eration step removes additional hydrocar-
bons by a proprietary process and
enhances the effectiveness of the acti-
vated carbon and molecular sieve beds,
which remove the remaining volatile or-
ganic compounds and hydrogen sutfide in
the landfill gas. This approach is more
flexible than utilizing dry bed adsorbents
alone and has built-in flexibility for the wide
range of contaminant concentrations which
can exist from site to site and even within a
single site varying with time.
The three adsorbents are regenerated
by using heated gas from the process
stream. A small portion of the treated land-
fill gas is heated and then passes through
the beds to strip the adsorbed contami-
nants. After exiting the final bed, the re-
generation gas is fed into a low nitrogen
oxide (NOX) incinerator where it is com-
bined with the vaporized condensates from
the refrigeration processes, and the mix-
ture is combusted to provide 98% destruc-
tion of the NMOCs from the raw landfill
gas.
The pretreatment system design pro-
vides flexibility for operation on a wide
range of landfill gas compositions: it has
minimal solid wastes, high thermal effi-
ciency, and low parasite power require-
ments. The pretreatment system is based
upon modification of an existing system
and utilizes commercially available com-
ponents. The process train and operating
characteristics need to be validated by
demonstration. Key demonstrations in
Phase II will include: the achievement of
low total halide contaminant levels in the
treated gas; effectiveness of the regenera-
tion cycle as affected by regeneration time
* 1 scf/h = 0.028 sm'/Ji
and temperature; durability of the regener-
able beds; and tow environmental emis-
sions.
Fuel Cell Power Plant
The commercial landfill gas energy con-
version conceptual design incorporates four
200-kW fuel cell power units. Since each
of the four units in the concept is identical,
this discussion will focus on the design
issues for a single 200-kW power unit.
A preliminary design of a fuel cell power
plant was established to identify the de-
sign requirements which allow optimum
operation on landfill gas. Three issues spe-
cific to landfill gas operation were identi-
fied which reflect a departure from a design
optimized for operation on natural gas. A
primary issue is to protect the fuel cell from
sulfur and halide compounds not scrubbed
from the gas in the fuel pretreatment sys-
tem. An absorbent bed was incorporated
into the fuel cell fuel preprocessor design
which contains both sulfur and halide ab-
sorbent catalysts. A second issue is to
provide mechanical components in the re-
actant gas supply systems to accommo-
date the larger flow rates that result from
use of dilute methane fuel. The third issue
is an increase in the heat rate of the power
plant by approximately 10% above that
anticipated from operation on natural gas.
This is a result of the inefficiency of using
the dilute methane fuel. The inefficiency
results in an increase in heat recoverable
from the power plant. Because the effec-
tive fuel cost is relatively low, this decrease
in power plant efficiency will not have a
significant impact on the overall power plant
economics.
The landfill gas power plant design pro-
vides a packaged, truck transportable, self-
contained fuel cell power plant with a
continuous electrical rating of 200 kW. It is
designed for automatic, unattended opera-
tion, and can be remotely monitored. It can
power electrical loads either in parallel with
the utility grid or isolated from the grid.
Environmental and Economic
Assessment of the Fuel Cell
Energy Conversion System
The commercial application of the con-
cept to the market described previously
was assessed. For the purpose of the
evaluation, a site capable of supporting
four fuel cell power modules was selected.
The site would produce approximately
434,000 scf of landfill gas per day. The gas
contains approximately 50% methane with
a heating value of 500 Btu/scf.
The analysis of the environmental im-
pact shows that both the fuel cell and a
flare system can be designed to eliminate
the methane and the non-methane organic
compounds from the landfill gas system.
For the example site considered, the meth-
ane elimination is essentially complete for
both systems, and 98% of the NMOCs are
destroyed. Trace amounts of sulfur oxides
(SO.) and NOX will be emitted in each
case. With the fuel cell system, however,
significant reductions of NO, and SO, will
be achieved due to the fuel cell energy
generation. This analysis assumes an 80%
capacity factor for the fuel cell and offset-
ting emissions from electric utility power
generation using a coal-fired plant meeting
New Source Performance Standards. For
the example site, the fuel cell energy con-
version system provides 5.6 million kWhr
of electricity per year, with a net reduction
of 35.2 tons* per year of NO, and 16.8 tons
per year of SOS from reduced coal use.
Economically the fuel cell energy sys-
tem has the potential for deriving revenues
from electric sales, thermal sales, and emis-
sion offsets credits. These revenues can
be used to off set the investment cost asso-
ciated with gas collection, gas pretreat-
ment, and fuel cell power units. The level
of these revenues depends upon the value
of the electricity, the amount and value of
the heat used, and the value of the emis-
sions offsets.
The fuel cell energy conversion system
was studied to establish the net revenues
or costs for processing landfill gas to miti-
gate methane emissions. For this analysis,
h was assumed that the fuel cell energy
conversion system and the flare system
would have an overall annual capacity fac-
tor of 80%. For this analysis, two levels of
fuel cell installed costs were considered^
The lower level represents a fully mature
cost when the power plant has been ac-
cepted into the marketplace, and is rou-
tinely produced in large quantities. The
upper level represents a price level when
the power plant is being introduced into
the marketplace, and is produced on a
moderate and continuous basis.
Figure 2 shows the fuel cell revenues
for the most stringent application situation
(no emission credits or thermal energy
utilization). In this case, the fuel cell re-
ceives revenues only from the sale of elec-
tricity. Although the emissions are lower
from the fuel cell, no specific credit or
value is attached to them for this example.
Under these conditions the fuel cell is still
the economic choice for most locations at
the mature product installed cost. At the
entry level cost the fuel cell is economical
in those areas where the value of electric-
* 1 ton = 907 kg
-------
3000
2000
rooo
5*5 0
!U.
so
-2000
Fuel Cell Installed Cost
Mature Product
Market
Entry
Cost
I
Hare Economic Gas Collection
Option andFlare
I I I
2.0 4.0 6.0 8.0 10.0 12.0
Value Received for Fuel Cell Electricity, kWh
14.0
Figure 2. Comparison of fuel cell to flare for methane mitigation assuming electric revenues
only.
Hy Is 9 cents per kWh or higher. With the
potential for revenue from thermal energy
or emission offset credits, the economics
become more competitive. Thus the appli-
cability of the concept would become at-
tractive to a broader market.
Other energy conversion systems could
also produce electric and/or thermal en-
ergy. Both the internal combustion engine
and the gas turbine engine have been
suggested as options for methane mitiga-
tion at landfill sites. For the landfill size
selected for this analysis, the internal com-
bustion engine is more effective than the
gas turbine options for cleanup. This is
used as the basis for the comparisons
provided here. The internal combustion
engine can provide both heat and electric
energy while consuming the methane at
the landfill gas site. With the present state-
of-the-art technology, however, a lean-bum
internal combustion engine has higher lev-
els of NO, emissions than the fuel cell
unless special precautions are taken to
clean the exhaust. For this analysis two
cases were considered. The first case as-
sumes no cleanup of the internal combus-
tion engine exhaust, and the second
assumes that the exhaust is cleaned with
selective catalytic reduction (SCR). Since
the SCR employs a catalyst in the cleanup
system, the landfill gas will have to be
pretreated in a manner similar to the fuel
cell system. For those cases with a SCR
cleanup system, a pretreatment system
has also been included as part of the total
system cost.
Figure 3 shows the results of the eco-
nomic analysis for the fuel cell system and
the internal combustion engine system.
Since both systems can provide electricity,
the comparison between the systems is
based on the cost of electricity generated
from the energy conversion system with
appropriate credit for thermal sales and/or
emission offsets. The fuel cell is competi-
tive at the full mature price when no ex-
haust cleanup is required with the internal
combustion engines. However, the opera-
tion of the internal combustion engine at
the landfill site would be quite dirty, and
significant amounts of NO, would be added
to the ambient air compared to the fuel
cell. For many locations where the fuel cell
would be considered, such as California or
other high emissions areas, the exhaust
cleanup option is required. Consequently,
the fuel cell option would be fully competi-
tive with the internal combustion engine
option for most cases where on-s'rte cleanup
of the internal combustion engine is re-
quired. In areas where a SCR would be
employed to clean up an internal combus-
tion engine exhaust, the fuel cell concept
is competitive at entry level cost.
Based on the analysis of both the flare
option and other energy conversion op-
tions, the fuel cell power plant is fully com-
petitive in all situations in the mature
production situation. For initial power plant
applications with limited lot production, the
fuel cell power plant is competitive in areas
with high electric rates and/or severe emis-
sions restrictions at the local landfill site.
Demonstration Project
Preliminary Design
The objective of the demonstration
project is to validate the economic and
environmental feasibility of a commercial
fuel cell energy recovery concept operat-
ing on landfill gas. A preliminary design of
the demonstration project shown in Figure
4 is described, which identifies the key
issues to be resolved before demonstra-
tions and describes the major components
of the demonstration project.
Demonstration project design require-
ments were derived from the commercial
concept. These requirements were used
to define project site selection criteria, gas
pretreatment system design, and commer-
cial fuel cell modifications to accommodate
landfill gas.
The site selected for the demonstration
project is the Penrose Station in Sun Val-
ley, California. This site, owned and oper-
ated by Pacific Energy, accepts landfill gas
from four municipal sold waste landfills.
Penrose Station presently produces 8.9
MW of electricity from landfill gas, using
internal combustion engines. The demon-
stration will operate on a slip stream from
Penrose's gas feed.
Because Penrose accepts gas from four
fills, some of which contain industrial waste,
the composition and contaminant levels
vary considerably. Average methane con-
tent is 44% and the gas typically contains
150 ppmv sulfur and 78 to 95 ppmv halides.
The sulfur contaminant levels are higher
than typically found in municipal solid waste
landfill gas. A successful demonstration at
Penrose will show applicability of the con-
cept to a broad segment of the market.
Conclusions
Based on the environmental and eco-
nomic evaluation of the commercial fuel
cell energy system, the following can be
concluded:
-------
10.0
8.0
6.0
4.0
2.0
Electricity Sates
Thermal Recovery
Emissions Offsets
With
SCR
Exhaust
Cleanup
Mature
Product
Cost
No
Exhaust
Cleanup
HP272-04
R9117O9
Fuel Cell
Energy Conv.
System
I.C.E.
Energy Conv.
System
Figure 3. Comparison of fuel cell to internal combustion engine
energy conversion system.
The fuel cell landfill gas to energy
conversion system provides a net
reduction in total emissions while si-
multaneously mitigating the methane
from the landfill gas.
Fuel cells will be competitive at initial
product prices on landfill sites lo-
cated in high electric cost areas or
where the thermal energy can be
utilized. The fuel cell Will also be
attractive where there is a credit for
the environmental impact of fuel cell
energy conversion.
When the projected mature product
price is achieved, fuel cells will be
competitive for most application sce-
narios. In .many situations, fuel cells
will provide net revenues to the land-
fill owners. This could, in the long
term, result in methane mitigation
without additional cost to the ultimate
consumer.
A demonstration project design was
established which addresses the key
technical issues facing commercial
application of the fuel cell energy
recovery concept to the market. A
site has been selected for the dem-
onstration which fairly represents the
landfill gas market.
Recommendations
Phase II of the project, which evaluates
the gas pretreatment system at the se-
lected site, should be conducted to verify
that landfill gas can be cleaned to meet
fuel cell requirements. The pretreatment
system design needs to be finalized to
resolve the remaining cleanup issues and
construction started as soon as possible in
Phase II. A challenge test should be de-
fined to evaluate the limits of operating
capability of the pretreatment system in-
cluding regeneration and adsorption break-
through conditions.
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Penrose
Station
Gas Wells
and
Collection
System
(PacHic Energy)
Utility
Power
Lines
A
AC Power*"
to Grid
Gas-Guard®
Gas Pretreatment
System
(Biogas
Development Inc.)
PC25
Fuel Cell
Power Plant
(ONSICorp.)
Landfill
X
x
x
X
x
Natural Gas
Southern California Gas Company
Flgvn4. Proposed demonstrator concept
if U.S. GOVERNMENT PRINTING OFFICE: IW - 64O-OHO/40167
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GJ. Sandeltiis with International Fuel Cells Corp., South Windsor, CT 06074.
Ronald J. Spiegel is the EPA Project Officer, (see below).
The complete report, entitled "Demonstration of Fuel Cells to Recover Energy from
Landfill Gas: Phase I Final Report: Conceptual Study," (Order No. PB92-137520/AS;
Cost: $19.00, 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
EPA/600/SR-92/007
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