Fuel cells could energize treatment plants

Diagram courtesy Hydrogenics Corporation.

Fuel cells operating at wastewater treatment facilities have been demonstrating a cutting-edge application for reducing emissions of methane and carbon dioxide, pollutants that contribute to global warming.

A fuel cell in Yonkers, New York, utilizing Anaerobic Digester Gas (ADG) has the distinction of being the first project of its kind in the Western Hemisphere. According to Yan Kishinevsky of the New York Power Authority, more than 90% of the wastewater treatment plants in the United States generate ADG as a by-product of their operation, requiring many of these plants to be regulated as stationary sources of air pollution under the Clean Air Act.

The gas, primarily methane and carbon dioxide, is a by-product of sewage treatment. Modern plants flare the gas, and many more are using it to power absorption chillers, reciprocating electric generators, or even as fuel for a gas turbine. All of these options contribute much more pollution to the air and are less efficient than a fuel cell.

Realizing the potential of digester gas as a fuel, NYPA enlisted the help of Westchester County in finding a way to utilize the gas while reducing plant emissions. The partners decided that fuel cells were the solution. To demonstrate the application, they installed a 200-kilowattt fuel cell power plant, manufactured by International Fuel Cells of Connecticut, at the Yonkers Wastewater Treatment Plant. The fuel cell is producing power at just below $0.08/kWh, and while the original estimated operation maintenance costs were $0.015/kWh, they are substantially below that figure to date.

Fuel cells use a chemical reaction, rather than combustion, to produce electricity in a process that is the reverse of electrolysis. In electrolysis, an electric current applied to water produces hydrogen and oxygen. By reversing this process, hydrogen and oxygen are combined in the fuel cell to produce electricity and water.

The environmental benefits of fuel cells are significant, especially when compared with typical fossil-fuelled power plants. Air emissions, in particular, are much lower from a fuel cell. For example, the Power Authority's 200-kw fuel cell in Yonkers generates about 1.6 million kilowatt-hours of electricity a year, and in that time releases only 72 pounds of emissions into the environment. In comparison, an average fossil-fuelled plant generating the same amount of electricity annually produces more than 41,000 pounds of pollutants.

"Projects like these demonstrate the enormous potential of fuel cell technology to do 'double-duty' for our environment," says Robert Rose, executive director of the US Fuel Cell Council. "First, they capture waste gases which are contributors to global warming. Second, by utilizing digester gas, a renewable source of fuel, fuel cells reduce the need for traditional, fossil-fuel based power generation. As an added bonus, fuel cells are a more efficient way to generate electricity -- you're harnessing more power from the fuel."

Source: US Fuel Cell Council, Tel: (202) 293-5500

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