The U.S. Environmental Protection Agency (EPA) has described landfills as an "effectively untapped resource" for renewable energy. The agency estimates that landfills are the source of about 12% of global methane emissions. (Methane is about 21 times more powerful as a greenhouse gas than CO2.)
The EPA estimated that there were some 1,000 projects around the world currently devoted to recovering landfill gas (LFG) for sale to customers. As of December 2007, approximately 445 LFG energy projects (Figure 6) were operational in the U.S., according to the EPA. They generate approximately 11 billion kWh of electricity per year and deliver 236 million cfd of LFG to direct-use applications.
6. Talking trash. Not surprisingly, states with the largest and densest population centers have the highest number of current and potential landfill gas energy projects. Data are for December 2007. Source: EPA
The EPA estimates that approximately 535 additional landfills (out of 1,700 total operating landfills) present attractive opportunities for project development. If fully developed, these additional landfills could produce over 1,200 MW of electricity.
Electricity for on-site use or sale to the grid can be generated using a variety of different technologies, including internal combustion engines, turbines, microturbines, Stirling engines (external combustion engine), Organic Rankine Cycle engines, and fuel cells. The vast majority of projects use internal combustion (reciprocating) engines or turbines; microturbine technology is being used at smaller landfills and in niche applications. Certain technologies, such as the Stirling and organic Rankine cycle engines and fuel cells, are still in the development phase.
The use of biogas (another name for methane produced from waste, manure, or other organic matter) for power generation is most developed in Europe, where Germany has 70% of the global market. In Britain, landfill gas makes up a quarter of the country’s renewable energy.
Among the many new LFG projects announced in the past few months were these:
Indiana: The Oakridge Landfill in Logansport and Liberty Landfill in Buffalo are Waste Management Inc.’s newest Indiana power generating sites to harness the gas produced by decomposing garbage. Waste Management, the nation’s largest garbage hauler, has installed methane-to-electricity systems at 16 of its Indiana landfills and at hundreds more nationwide to turn the gas into power. Last year the company set an ambitious goal to develop up to 60 LFG projects at its landfills by 2012.
South Carolina: A new $3.8 million generating station near Belton, S.C., will use two Caterpillar 20-cylinder engine generators turn methane into power. Santee Cooper and Allied Waste are partners in the 3.2-MW generating station fueled by biogas from the Anderson Regional Landfill.
Asia: GE announced in Oct. that it had opened a new Jenbacher Gas Engine Packaging plant in China to meet demand for the engine-generator sets in Asia. The fuel-flexibility of the Jenbacher engines is making them popular in the region because they operate on either natural gas or a variety of specialty fuels, including coal mine gas, landfill gas, biogas, wood gas, sewage gas, and industrial waste gas.
Mexico: A newly expanded LFG-to-energy project in Monterrey, Mexico, uses GE Energy’s Jenbacher gas engine. The 12-MW project converts the Simeprode landfill’s gas into electricity, which is used to support the solid waste facility’s operations as well as Monterrey’s light-rail system during the day and city street lights at night. The electricity is also being sold at a discount rate to seven municipalities in the greater Monterrey region.
North Carolina: Duke Energy announced in August that it had signed an agreement with Methane Power Inc. to purchase 2 MW of renewable energy generated from the City of Durham landfill, which was closed in the mid-1990s.
Apparently, some folks don’t think the EPA is doing enough to encourage LFG power projects. On Oct. 23 the Environmental Defense Fund filed a notice of intent to sue the EPA for its failure to update emission standards for hundreds of landfills nationwide.