LANDFILL GAS TO ENERGY PROJECT CASE STUDIES: A GLOBAL PERSPECTIVE ON APPROACHES AND RESOURCES FOR REDUCING METHANE EMISSIONS

摘要

Methane is the second most abundant greenhouse gas (GHG) after carbon dioxide (CO2) and is responsible for more than one-third of anthropogenic (human induced) warming in the world today. Although methane makes up only 14 percent (%) of GHG emissions worldwide, its higher global warming potential (GWP) compared to CO2 (nearly 25 times higher) makes it a significant factor in climate change. Methane is emitted into the atmosphere from several human-related sources, including agriculture, coal mines, landfills, oil and gas systems, and wastewater. As seen in Figure 1, global anthropogenic methane emissions for 2010 were estimated to be 6,875 million metric tons of CO2 equivalent (MMTCO2E) and are anticipated to increase by 15% to 7,904 MMTCO2E by 2020. Globally, landfills are the third largest anthropogenic emission source, contributing approximately 12% of methane emissions or nearly 750 MMTCO2E. In the United States, landfills accounted for 17% of all methane emissions in 2009. Landfill gas (LFG) - generated as solid waste decomposes in a landfill - consists of just under 50% methane and 50% CO2, with a small percentage of non-methane organic compounds and trace amounts of inorganic compounds. The amount of methane generated in a landfill depends upon the quantity and moisture content of the waste as well as the design of and management practices at the landfill.