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 ------- 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. ------- 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 ------- ------- 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 ------- |