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Biogas Fuel Cell
Columbia Boulevard Fuel Cell
Located in Portland, Columbia Boulevard is the largest wastewater treatment plant in Oregon. The facility handles approximately 82 million gallons of wastewater per day. As a byproduct of the sewage treatment process, the plant produces biogas. A fuel cell at the plant uses biogass to generate electricity. The Columbia Boulevard fuel cell is the first installation in the western United States of a fuel cell running on wastewater digester gas and only the third such system in the nation.
Anaerobic digesters at the plant reduce biomass solids and help purify wastewater. The digesters produce biogas, which consists largely of methane, a gas that is rich in hydrogen. After the gas is cleaned to remove impurities, it enters the fuel cell. Inside the fuel cell, a processor extracts hydrogen from the gas. The fuel cell´s power section then combines hydrogen and oxygen to produce water and electricity. A converter changes the direct current output from the power section into alternating current (AC). The AC power is fed into the local power grid.
The fuel cell at Columbia Boulevard is a phosphoric acid fuel cell manufactured by ONSI Corporation. Columbia Boulevard sells the power to Portland General Electric. The City of Portland received financial support for the fuel cell from The Oregon Department of Energy, Portland General Electric and the Fuel Cell Climate Change Program. Support from the Oregon Department of Energy included tax credit through the Business Energy Tax Credit Program. The total cost of the system was about $1.3 million.
The estimated electrical output of the fuel cell is about 170 kilowatts. The system will generate an estimated 1,400,000 kilowatt-hours a year. By producing its own electric power from the fuel cell, Portland expects to save over $60,000 a year in energy costs.
The project will produce environmental benefits by reducing greenhouse gas emissions. Using biogas to generate electricity displaces electricity generation at regional power plants that consume fossil fuels. The result is a reduction in greenhouse gas emissions. A 200-kilowatt fuel cell would offset an estimated 736 tons of carbon dioxide emissions annually.
Gas cleaning is necessary to eliminate impurities in the biogas. These are principally hydrogen sulfide, halogens (fluorine, chlorine and bromine), moisture, bacteria and solids. Biogas also contains carbon dioxide, which cannot be removed easily. The gas-cleaning system at Columbia Boulevard uses a potassium hydroxide impregnated activated carbon filter to remove the hydrogen sulfide. The Oregon Bioenergy Program provided funds to help pay for engineering and design services for the gas-cleaning section of the fuel cell system.