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King County, PSE, and Bio Energy-Washington generate power from landfill gas

King County, Puget Sound Energy (PSE) and Bio Energy-Washington, a company specialising in building landfill gas-to-energy systems, are joining forces to produce green energy from landfill gas.

The project will use the methane gas generated from decomposing waste buried at King County’s Cedar Hills Regional Landfill in Maple Valley, about 20 miles southeast of Seattle, Washington, USA. Methane produced by the landfill will be collected, processed, and piped to PSE’s natural gas-fired power plants.

A connecting line that runs between the landfill and the adjacent Northwest Pipeline – the region’s main transmission supply line for natural gas – will transport the methane gas to the PSE plants. PSE will use the methane to generate an estimated 287,000 MWh of electricity annually

The power PSE produces from Cedar Hills’ methane could make Cedar Hills the third-largest landfill-gas energy project in the USA. Moreover, Cedar Hills could rank among the country’s larger non-wind renewable-power projects.

Bio Energy-Washington is building and operating the gas-to-energy facility at Cedar Hills, which includes the quarter-mile pipeline for shipping the processed landfill gas to Northwest Pipeline and on to PSE’s natural gas-fired power plants.

The gas-processing plant includes a series of sequential steps which remove all the contaminants found in landfill gas. The end result is said to be gas that is cleaner than natural gas recovered from conventional gas wells.

Bio Energy-Washington estimates that it will process and deliver at least 4.5 million ft3 of methane daily from the county landfill. Deliveries are expected to average about 5.5 million ft3 per day over 20 years.

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