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Environment

Suddenly, Garbage and Sewage Gas Is a Hot Commodity

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Methane, a natural gaseous byproduct of both rotting garbage in landfills and raw sewage, is increasingly regarded as being valuable.

Instead of allowing methane to float up into the atmosphere, waste companies are increasingly harnessing it for use as heating gas and as a means to produce electricity [San Francisco Chronicle blog].

It seems to be an alternative energy whose time has come: Methane landfill projects are already online in almost every state, and San Antonio has just signed on to become the first city to harvest methane from its sewage treatment facility. Harvesting methane serves a two-fold purpose:

If it is not captured, the E.P.A. says, landfill methane becomes a greenhouse gas at least 20 times more potent than carbon dioxide, the principal greenhouse gas, when it rises into the atmosphere. The agency estimates that landfills account for 25 percent of all methane releases linked to human activity. As a result, capturing methane at former and active landfills is a global housekeeping benefit as well as an important alternative energy niche [The New York Times].

The microbes that feast on organic material in landfills are also active in sewage treatment plants, busily breaking down what managers politely refer to as "biosolids." That realization led to the next step in methane harvesting: Within two years, San Antonio expects to have a fully operational system that will commercialize the gas produced during the treatment of human waste.

The San Antonio Water System will sell captured methane gas generated from the utility's treatment of 140,000 tons of biosolids, or sewage, from customers each year.... "Treating these biosolids generates an average of 1.5 million cubic feet of gas a day," said Steve Clouse, the water system's chief operating officer. "That's enough gas to fill seven commercial blimps or 1,250 tanker trucks each day" [AP].

If their system is a success, many other cities may follow suit.

Image: flickr/D'Arcy Norman

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