Landfill gas: A green, renewable power source
In 1983, long before “green” energy became a buzzword and the negative effects of greenhouse gases like methane were widely acknowledged, the Monterey Regional Waste Management District had already developed one of the first landfill gas-to-electric energy plants in the nation.
Methane and carbon dioxide gases are byproducts of the anaerobic decomposition of refuel in the landfill. The Monterey district’s landfill gas system now collects 610 million cubic feet of gas per year, consisting of 50 percent methane and 50 percent carbon dioxide, from refuse that has been buried since the Monterey Peninsula Landfill opened in 1966.
Emcon Associates of San Jose, Calif., designed the original well field and promoted the project. Perennial Energy, Inc. designed and installed the first engine generator system. The project was developed by Palmer Capital of Chicago and financed by the Bank of New England.
In 1986 the Monterey district acquired an engine system and Emcon purchased the gas rights and collection system. In 1994, the project was expanded. A new, 3,200-square-foot building was constructed to house up to four engine generators and switchgear equipment. A third generator was installed, enlarging the overall production capacity of the facility to 2,100 kW. The expansion of the project enabled the district not only to produce enough power to meet all of its own needs but also to generate a greater surplus of electricity to sell. The 1994 expansion of the project was designed by the district staff, the Paul Davis Partnership and Applied Power. It was constructed by Daniels Construction.
The MRWMD was the first in the U.S. to use Austrian-made Jenbacher engines. They were installed in 1997, 1998 and 2002. These engines are designed to burn landfill gas and are used extensively in Europe and other parts of the world. In early 2006 the district replaced the first engine with a new CAT 3520 landfill gas engine that delivers twice the amount of electricity over the original engine.
Currently, the system collects more than 1.5 million cubic feet of gas per day from a 120-acre area containing refuse buried for nearly 40 years. It includes 41 horizontal and vertical gas wells in the active areas of the landfill. Instruments monitor each well and collect data to allow maximum production and ensure minimum gas emissions from the landfill to the environment. As part of the district’s environmental monitoring program, probes have been installed to detect migrating landfill gas.
The project’s four generators now provide approximately 4.6 megawatts of clean alternative power, meeting all of the district’s own power needs and supplying electricity for nearly 4,000 homes. Heat exchangers capture waste heat from the radiators and send it to district buildings for heating and to produce hot water. By using its own power, the district saves approximately $230,000 per year. During the fiscal year 2006-07, gross revenues from electricity sales totaled $1.75 million. Total power produced since 1983 is over 320 million kilowatt hours and total project revenues have surpassed $17 million.
The district is a partner in the U.S. EPA Landfill Methane Outreach Program. The electricity generated by the project is classified by the state and federal authorities as renewable, or “green” energy. In 2007, the project received the gold Excellence Award from the Solid Waste Association of North America in the Landfill Gas Utilization category.
Information provided by the Monterey Regional Waste Management District.
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