Sewage plant makes electricity from waste gas; Instead of air pollutants, only byproduct hot water


YONKERS, N.Y. -- Sewage treatment plants purify water, but they also foul the air with methane and sulfur and nitrogen oxides, which smell bad and contribute to smog and global warming.

Now, a sewage plant here is turning its unwanted gas into electricity and heat. The only byproduct, officials say, is hot water.

The new fuel-cell system, the first for a sewage plant in North America, has proved to be effective after a year of operation, officials from the New York Power Authority said. The system generates 200 kilowatts of electricity, enough to supply 60 typical homes, the officials said.

In the process, more than 20 tons of gas that would otherwise have been burned off in the open air or wafted away was turned into electricity last year, said Shalom Zelingher, the director of research for the Power Authority.

The hot water generated was used to warm bacteria that help break down the sewage. "This is not just a concept anymore," he said.

Fuel cells run on hydrogen, which is contained in standard fossil fuels such as natural gas and gasoline and also in methane. They produce no significant pollution because they use a chemical reaction to harvest energy from the fuel without burning it, Zelingher said.

The same process supplies electricity on the space shuttle and is finding more uses each year on Earth. Some of the biggest benefits come at a sewage plant, where the system uses waste methane, which is abundant and free, instead of natural gas or some other fuel that must be bought.

The systems can also be run with gas from landfills.

New York City environmental officials recently inspected the Yonkers system and said they hoped to install fuel cells at some of the city's 14 sewage plants, in hopes of recycling some of the 1.6 billion cubic feet of gas generated every year. Most of that gas is now burned off in flares at the plants.

Fuel cells have been around for decades, but because of their high price and complicated technology they have been relegated until recently to exotic applications such as the space program.

Federal energy officials say one of the greatest benefits of using a fuel cell at a sewage plant or landfill comes from consuming methane, a gas that otherwise contributes significantly to the growing greenhouse effect.

Pub Date: 2/14/99

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