In Seattle, Third Year of Landfill-Powered Electricity Age Begins

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All the electricity from Seattle City Light’s renewable power program goes into the grid, so it’s not actually possible to specify what flavor of electricity you prefer to get at your outlets: wind, solar, or landfill methane.

But it’s still true that, for the past two years, about 5,600-homes-worth of Seattle electricity (six megawatts) has come from the Columbia Ridge landfill‘s methane production. Seattle sends about 400,000 tons of trash to Columbia Ridge annually–it’s one of our nation’s largest landfills.

In December 2009, landfill operator and renewable power generator Waste Management brought a $10-million electrical power plant online, fueled by the methane gas the landfill’s organic decay produces. For years, that methane had simply been burned off (“flared”)–you had to do something with it, as it can suffocate or even explode if allowed to build up. Even our waste was generating greenhouse gases.

But thanks to renewable-energy pushes like Washington’s I-937–which requires larger electric utilities to get 15 percent of their output from renewable energy by 2020–burning methane to create electricity became a feasible energy source. The Los Angeles Times counted some 500 electricity-producing landfills across the U.S. in 2010.

In January 2010, Seattle City Light bought all six megawatts of Columbia Ridge’s capacity, for the next 20 years. (Landfills don’t supply methane forever–eventually the organic matter present has decomposed.)

City Light’s Scott Thomsen says that while six megawatts is a drop in the bucket of Seattle’s electricity needs, methane-powered electricity is more important than it might seem, because it can meet baseload demands. Columbia Ridge’s turbines produce their electricity day and night, day in and day out, as opposed to solar (daytime only) and wind (most productive evenings and overnight).

It’s all about the “volume and shape” (see daily power graph) of the electricity, Thomsen says. Because electricity is not practically speaking storable, from a utility’s perspective, 24/7 sources are more valuable. How much more valuable? I asked Thomsen about kilowatt-hour cost estimates, but he couldn’t say, beyond that the Columbia Ridge contract was “competitive” with other renewable energy sources.