October 22, 2004 | General

Landfill Methane Fuels Green Energy Program

BioCycle October 2004, Vol. 45, No. 10, p. 37
Power utility based in Sacramento, California has 15-year contract with landfill that provides renewable energy to both commercial and residential customers.

THE KIEFER LANDFILL which is owned by Sacramento County, California, has a 15-year purchase agreement with the Sacramento Municipal Utility District (SMUD) to have its methane used in the SMUD Greenergy program. The gas-to-energy plant has been operating for four years, supplying 50 to 60 percent of the load that now serves more than 28,000 “Greenergy” customers. SMUD offers a flat rate of an extra $6/month to renewable energy participants which now include 900 companies.
Announces SMUD in its promotional outreach efforts: “When you join Greenergy, your company supports the generation of electricity from renewable resources such as solar, wind and biomass. Your participation will distinguish your company as an environmental leader.” The utility matches 100 percent of customers’ energy needs with purchases from renewable sources for use on its power grid. Customers have been responding well to the program, says Jim Burke of SMUD. “Our monthly growth rate has been 44 percent, and the utility offers our green energy customers a flat rate for either the 50 or 100 percent option.”
The region generates about 100,000 tons of green waste per year, with half going to a compost facility operated by Grover Environmental and half going to the county landfill. “We take in about 700,000 tons of municipal solid waste per year,” notes Rich Owings of Sacramento County landfill which generates 8.3 megawatts of power. The gas-to-energy plant pulls methane via 150 wells drilled into the Kiefer Landfill. The gases are used to run three Caterpillar internal combustion engines that turn generators to produce electricity.
Number and spacing of wells depend upon specific landfill conditions such as volume, density and moisture content. Perforated plastic pipes are inserted into the wells, which are constructed by drilling holes to within 15 feet of the landfill bottom. Area around the pipes is filled with large gravel to prevent refuse from plugging perforations. A series of pipes connect the wells to larger, header pipes that deliver the gas to the energy facility where internal combustion engines are located. A dedicated power line is used to deliver electricity to the SMUD distribution system. The grid connection includes metering equipment to monitor sales as well as system protection devices. The facility cost $14 million to construct.
In terms of global warming impact, decomposition of MSW in landfills generates a gas primarily of methane and carbon dioxide – compounds that contribute to ozone formation, a primary cause of smog and greenhouse gases. Landfills are the largest source of man-made methane emissions, comprising almost 40 percent of these emissions annually. Landfill gas also threaten groundwater since it acts as a carrier for trace VOCs. Given that methane’s global warming potential is 23 times that of carbon dioxide by weight, utilization of methane gas at facilities such as Kiefer’s gas-to-energy plant becomes a significant positive benefit to global atmospheric problems.
Project engineers calculate that recovered gas yields the same reduction in greenhouse gases as removing 81,000 cars from the road for one year or planting 110,000 acres of trees. SMUD has committed to increase the renewables portion of its power mix to 10 percent by 2006 and to 20 percent by 2011 through its solar, wind power, biomass and small hydroelectric facilities.

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