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REPP
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Biomass: Landfill Methane, Explained
By Virinder Singh
Landfills across the United States are a fount of potential energy. Landfill gas is created when waste in a landfill decomposes. This gas is about 50 percent methane (CH4), also known as natural gas, and 45 percent carbon dioxide (CO2). Instead of allowing landfill gas to escape into the air, the gas can be captured, converted, and used as an energy source. Using the gas helps to reduce odors and other hazards associated with landfill gas emissions, and it helps prevent methane from migrating into the atmosphere and contributing to local smog and global climate change.1
Landfill methane has attracted considerable attention due to its relative ease of installation and its clear environmental benefits. On a pound for pound basis, unflared methane imposes twenty-one times the climate change impact than does CO2. On an electricity production basis, when burning methane that would otherwise be released from a landfill into the atmosphere, a landfill gas fueled electric generator typically avoids the equivalent of 10,000 to 15,000 lbs of CO2 per MWh. In effect such a landfill gas fueled electric generator is offsetting far more CO2 emissions per MWh of electric generation than is emitted from coal plants or any other common form of electric generation.
Landfill methane projects can involve a variety of power generation technologies in a wide range of sizes. The size and type of generation technology depends upon the amount of methane captured. Landfills with low capture rates can use internal combustion engines (250 kW and up), ones with medium capture rates can use gas turbines (3 MW and up), ones with high capture rates can use Rankine Cycle steam turbines (8 MW and up), and ones with very high capture rates can utilize combined cycle engines (20 MW and up).
Landfill methane project economics are promising—electricity costs for different landfill methane options all fall within the range of costs for new combined cycle natural gas plants.
In addition to the 200 landfill methane recovery projects in the U.S., U.S. EPA estimates that up to over 500 landfills in the U.S. could install economically viable landfill energy projects.
For more information on landfill gas and its uses, read US EPA's Emerging Technologies for the Management and Utilization of Landfill Gas PDF Document and see the EPA's Landfill Methan Outreach Program for more about what's happening in your state.
Bibliography:
NREL photo library
PIX number: 03766
Reclaiming postconsumer wastes; Argonne scientists are studying methane generation in landfills. Special probes are inserted to measure the gas pressure within the landfill.
Credit: Argonne National Lab
Date: 1/1/93
Definition from http://www.epa.gov/outreach/lmop/faq.htm#8
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