United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-98/002
March 1998
Project Summary
Demonstration of Fuel Cells to
Recover Energy from Landfill
Gas—Phase III. Demonstration
Tests, and Phase IV. Guidelines
and Recommendations
J. C. Trocciola and J. L. Preston
The report summarizes the results of
a four-phase program, conducted to
demonstrate that fuel cell energy re-
covery using a commercial phosphoric
acid fuel cell is both environmentally
sound and commercially feasible.
Phase I, a conceptual design and evalu-
ation study, addressed the technical
and economic issues associated with
operation of the fuel cell energy recov-
ery system of landfill gas (LFG). Phase
II included the design, construction, and
testing of a LFG pretreatment unit (GPU)
to remove critical fuel poisons such as
sulfur and halides from the LFG, and
the design of fuel cell modifications to
permit operation on low heating value
(LHV) LFG. Phase III was the demon-
stration test of the complete fuel cell
energy recovery system. Phase IV de-
scribed how the commercial fuel cell
power plant could be further modified
to achieve full rated power on LHV LFG.
The demonstration test successfully
demonstrated operation of the energy
recovery system, including the GPU and
the commercial phosphoric acid fuel
cell modified for operation on LFG.
Demonstration output included: opera-
tion up to 137 kW; 37.1% efficiency at
120 kW; exceptionally low secondary
emissions (dry gas, 15% oxygen) of
0.77 ppmV carbon monoxide, 0.12
ppmV nitrogen oxides, and undetect-
able sulfur dioxide; no forced outages
with adjusted availability of 98.5%; and
709 hours operation on LFG. The pre-
treatment (GPU) operated for 2,297
hours, including 709 hours with the fuel
cell, and documented total sulfur and
halide removal to much lower than
specified <3 ppmV for the fuel cell. The
GPU flare safely disposed of the re-
moved LFG contaminants by achieving
destruction efficiencies >99%. An envi-
ronmental and economic evaluation of
a commercial fuel cell energy system
concluded that there is a large poten-
tial market for fuel cells in this applica-
tion.
This Project Summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention and Control Division, Research
Triangle Park, NC, to announce key
findings 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. EPA has promulgated stan-
dards and guidelines for the control of air
emissions from municipal solid waste
(MSW) landfills. This Clean Air Act regu-
lation will result in the control of up to 7
Tg/year of methane (CH4). Collection and
disposal of waste CH4, a significant con-
tributor to the greenhouse effect, would
result from the emission regulations. This
EPA action provides an opportunity for
energy recovery from the waste CH4 that
could further benefit the environment. En-
ergy produced from landfill gas (LFG) could
offset both the use of foreign oil, and air
emissions affecting global warming, acid
rain, and other health and environmental
issues.
Results of a four-phase program showed
that energy could be recovered from LFG
using a commercial phosphoric acid fuel
cell. Phase I, a conceptual design and
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evaluation study, addressed problems as-
sociated with LFG as the feedstock for
fuel cell operation. Phase II included con-
struction and testing of the LFG pretreat-
ment module to be used in the demon-
stration. Its objective was to determine
the effectiveness of the pretreatment sys-
tem design to remove critical fuel cell cata-
lyst poisons such as sulfur and halides.
Phase III was a demonstration of the com-
plete fuel cell energy recovery concept.
Phase IV provided guidelines and recom-
mendations describing how the PC25™C
power plant could be modified to achieve
full-rated power of 200 kWon LFG, based
on experience gained testing the PC25A
Model.
Phase I
U. S. MSW landfills were evaluated to
determine the potential power output which
could be derived using a commercial 200
kW fuel cell. Each fuel cell would con-
sume 2800 SCMD of LFG to generate
200 kW, assuming a heating value of 4.45
kcal/liter.
The potential power generation market
available for fuel cell energy recovery was
evaluated using an EPA estimate of CH4
emissions in the year 1992. An estimated
4370 MW of power could be generated
from the 7480 existing and closed sites
identified. The largest number of potential
sites >200 kW occur in the 400 to 1000
kW range. This segment represents a
market of 1700 sites or 1010 MW.
The Phase I assessment concluded that
these sites are ideally suited to the fuel
cell concept. The concept can provide a
generating capacity tailored to the site be-
cause of the modular nature of the com-
mercial fuel cell. The best competing op-
tions, Rankine and Brayton Cycles, are
not as effective at these power ratings
due to high emission and poor energy
utilization.
As a result of the assessment, the con-
ceptual design of the commercial concept
was required to be modular (transportable
from site to site) and sized to have the
broadest impact on the market. The de-
sign is based on providing a modular,
packaged, energy conversion system
which can operate on LFGs with the wide
range of compositions typically found in
the U.S. The complete system incorpo-
rates the LFG collection system, a fuel
gas pretreatment system, and a fuel cell
energy conversion system. In the fuel gas
pretreatment section, the raw landfill gas
is treated to remove contaminants to a
level suitable for the fuel cell energy con-
version system. The fuel cell energy con-
version system converts the treated gas
to electricity and useful heat.
LFG is utilized in 110 MSW landfills in
the U.S. These systems have proven the
effectiveness of LFG collection systems.
Therefore, design and evaluation studies
in Phase I were focused on the energy
conversion concept utilizing fuel cells.
The commercial LFG-to-energy conver-
sion system is shown in Figure 1. The fuel
pretreatment system has provisions for
handling a wide range of gas contami-
nants. Multiple pretreatment modules can
be used to accommodate a wide range of
landfill sizes. The wells and collection sys-
tem collect the raw LFG and deliver it at
approximately ambient pressure to the gas
pretreatment system. In the gas pretreat-
ment system, the gas is treated to remove
non-methane organic compounds includ-
ing trace constituents which contain halo-
gen and sulfur compounds.
The commercial energy conversion sys-
tem shown in Figure 1 consists of four
fuel cell power plants. These power plants
are designed to provide 200 kW output
when operating on LFG with a heating
value of 4.45 kcal/liter and for accommo-
dating higher contaminant concentrations.
The output from the fuel cell is utility grade
Landfill gas wells
and collection system Transformer
800 kWfuel cell power plant
operating on landfill gas
Utility grid
Landfill site office
and blower
Gas pretreatment
system
Multiple fuel cell
power plants
Figure 1. Fuel cell energy conversion system commercial concept.
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alternating current. It can be transformed
and put into the electric grid, used directly
at nearby facilities, or used at the landfill
itself. The power plants are capable of
recovering cogeneration heat for nearby
use or rejecting it to the air.
Phase II
The major element of Phase II was the
construction and subsequent testing of a
gas cleanup system at the Penrose Land-
fill site in Los Angeles (Sun Valley), Cali-
fornia. Landfill gases consist primarily of
carbon dioxide (CO2), methane (CH4), and
nitrogen (N2), plus trace amounts of hy-
drogen sulfide (H2S), organic sulfur, or-
ganic halides, and non-methane hydro-
carbons. The specific contaminants in the
landfill gas of concern to the fuel cell are
sulfur and halides. Both of these ingredi-
ents can "poison" and therefore reduce
the life of the fuel cell power plant's fuel
processor. The fuel processor converts
CH4 in the LFG stream into hydrogen (H2)
and CO2 in an endothermic reaction over
a catalyst bed. The catalyst in this bed
can react with the halides and sulfides
and lose its activity; i.e., poison irrevers-
ibly. The system designed to remove fuel
cell contaminants is shown in Figure 2.
This system is known as the Gas Pre-
treatment Unit (GPU). H2S is first removed
by adsorption on a packed bed. The ma-
terial which performs this function is a
specially treated carbon activated to cata-
lyze the conversion of H2S into elemental
sulfur which is deposited on the bed. This
conversion to sulfur is by the reaction:
H2S + _ 02 _ H20 + S
This bed is not regenerable on site, but
the carbon can be regenerated off site if
desired.
The first stage cooler removes water,
some heavy hydrocarbons, and sulfides
which are discharged as condensate to
the Penrose plant's existing water con-
densate pretreatment system. Since the
demonstration landfill GPU operates on a
small slipstream from the Penrose site
compressor and gas cooler, some of the
water and heavy hydrocarbon species are
removed prior to the GPU. Most of the
contaminant halogen and sulfur species
are lighter and remain in the LFG to be
treated in the gas pretreatment unit. All
remaining water in the LFG, as well as
some sulfur and halogen compounds, are
removed in a regenerable dryer bed which
has a high capacity for adsorbing the re-
maining water vapor in the LFG. There
are two dryer beds so that one is always
operational while the other is being regen-
erated. The dry LFG is then fed to the
second stage cooler. This cooler can be
operated as low as -32° C and potentially
can condense out additional hydrocarbons
if present at high enough concentrations.
In addition, the second stage cooler re-
duces the temperature of the carbon bed,
therefore enhancing its adsorption perfor-
mance. The downstream hydrocarbon ad-
sorption unit, whose temperature is con-
trolled by the second stage cooler, is con-
servatively sized to remove all heavy hy-
drocarbon, sulfur, and halogen contami-
nant species in the LFG. This unit con-
sists of two beds of activated carbon so
that one is always operational while the
other is being regenerated. Both the re-
generable dryer and hydrocarbon removal
beds operate on a nominal 16 hour cycle
of each set of beds operating in the ad-
sorption mode for 8 hours and regenera-
tion mode for 8 hours. The gas then
passes through a particulate filter and is
warmed indirectly by an ambient-air finned-
tube heat exchanger to ensure a fuel inlet
temperature above 0° C before being fed
to the fuel cell unit.
The GPU was constructed at Interna-
tional Fuel Cells Corp.'s facility in South
Windsor, Connecticut. Construction of the
unit was completed in February 1993.
Upon completion of construction, the unit
was evaluated at the South Windsor facil-
ity, using N2 as the test gas. The unit
successfully completed the 16 hour con-
trol test verifying that rated flows, pres-
sure, and temperature were achieved. Af-
ter the test, the unit was shipped to the
landfill site located in Los Angeles, Cali-
fornia, where it was installed in April 1993.
The GPU was successfully tested at
the Penrose landfill site in Los Angeles
(Sun Valley), California. The GPU suc-
LFG
Condensation
of water and
hydrocarbons
Adsorption
of water
Adsorption of hydrocarbons
including organic sulfur and
halogen compounds
To
flare
Clean
LFG to
fuel cell
Regeneration
11.8 liters/sec
260° C
Regeneration
Water
desorption
To
flare "**
260° C
Regeneration
H/C
desorption
Figure 2. Landfill gas pretreatment unit (GPU) system.
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cessfully removed the sulfur and halogen
compounds contained in the LFG to a
level significantly below the specified value
for use with the phosphoric acid fuel cell
and to date has operated for approximately
2300 hours.
Table 1 compares the measured sulfur
and halide contents of the gas produced
by the GPU to the specification value.
The data verify that the GPU reduces the
sulfur and halide contents of LFG to a
concentration lower than required by the
fuel cell power plant. The exceptionally
low GPU exit contaminant levels indicate
that the low temperature cooler is not es-
sential, even though the reduced tempera-
ture in the activated carbon bed increases
capacity for sulfur and halogen com-
pounds. For system simplification in the
future, it may be beneficial to eliminate
the low temperature cooler, and simplify
the refrigeration system, in exchange for
increasing the activated carbon bed vol-
ume slightly. The favorable results of the
GPU testing led into Phase III, which en-
tailed characterizing the performance (i.e.,
emissions, efficiency, and power output)
of the commercial phosphoric acid fuel
cell power plant when operating on LFG
which has been purified by the GPU.
Phases III and IV
The power plant utilized in this program
is a commercial PC25™ 200 kW phos-
phoric acid fuel cell. The power plant was
shipped and installed at the Penrose Land-
fill during 1994. The unit was started on
natural gas prior to its modification for
operation on LFG. This testing was con-
ducted to establish a baseline performance
level. Upon completion of the natural gas
testing, the unit was shut down, modified
for LHV gas, and subsequently connected
to the GPU for testing on LFG. All power
produced by the unit was fed into the
electrical grid for sale to the local electri-
cal utility, the Los Angeles Department of
Water and Power (LADWP). This fuel cell
is the first ever connected to the LADWP
utility system grid. The revenue produced
by the sale of this electricity was used to
help offset program costs.
Emission testing of the power plant ef-
fluent was conducted during February
1995. Using EPA methods 6c, 7e, and 10,
respectively, emission levels of sulfur di-
oxide were undetectable at a detection
limit of 0.23 ppm, while nitrogen oxides
averaged 0.12 ppm and carbon monoxide
averaged 0.77 ppm. All the data are dry
measurements corrected to 15% oxygen.
These emission levels verify that fuel cells
can operate on LFG while maintaining the
low emission levels characteristic of this
commercial fuel cell power plant.
An exciting dimension of the PC25 op-
erating on LFG is that, unlike internal com-
bustion engines and turbines, the unit has
significant siting characteristics due to its
demonstrated low levels of emissions,
noise, and vibration. It can be located
remote from the landfill using gas piped
from the site. In this way, its thermal en-
ergy, as well as its power, can be put to
constructive use at a customer's building.
In addition, by siting at the building, the
economics improve significantly since the
power plant displaces commercial elec-
tricity which has a much higher cost than
the revenue which would be received if
the fuel cell were sited at a landfill and
received utilities' "avoided" cost. Utilizing
the fuel cell's thermal energy can result in
an overall efficiency [i.e., (Electrical En-
ergy plus Thermal Energyj/Energy Con-
tent of Gas Consumed] of 80%. This high
efficiency conserves natural resources and
reduces the amount of CO2 emitted to the
atmosphere. It also improves the econom-
ics, since heat may be sold to the building
owner.
Table 1. GPU Sulfur and Halide Contaminant Removal Performance and Specification (ppmV)
Contaminant Inlet Outlet Specification
Total Sulfur (as H2S)a
Total Halides (as Chloride)b
117
47
<0.047
<0.032
<3
<3
aMeasured by gas chromatography/flame photometric delineation by EPA methods 15, 16, and 18
bMeasured by gas chromatography by EPA method TO-14
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J. Trocciola andJ. Preston are with International Fuel Cells Corp., South Windsor,
CT 06074.
Ronald J. Spiegel is the EPA Project Officer (see below).
The complete report consists of two volumes, entitled "Demonstration of Fuel Cells
to recover Energy from Landfill Gas—Phase III. Demonstration Tests, and Phase
IV. Guidelines and Recommendations:"
Volume 1. Technical Report (Order No. PB98-127368; Cost: $25.00)
Volume 2. Appendices (OrderNo. PB98-127376; Cost: $57.00)
The above reports will be available only from: (cost subject to change)
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air Pollution Prevention and Control Division
National Risk Management 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-98/002
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