With EPA's recent announcement that new landfills will be required to capture two-thirds of their methane and air toxic emissions by 2023 (13 percent more than current requirements), the Obama Administration takes another step forward to curb greenhouse gas emissions. This step is especially valuable since landfills are the third largest source of methane emissions in the U.S. and methane is a greenhouse gas 25 times more potent than carbon dioxide. Additionally, when landfill gas is captured, it can be used for another purpose: energy. The process of capturing and using landfill gas (LFG) is considered biomass renewable energy.
Cities around the world are utilizing emissions from landfills to provide electricity to plants, manufacturing facilities, homes, businesses, and transportation. We expect using LFG for good will be receiving more attention especially if the EPA is successful in applying the elevated requirements to existing landfills and as countries around the world seek to reduce emissions. Here are 5 things you should know about the process of capturing and using methane from landfills for electricity:
1. Landfill gas (LFG) is 50 percent methane and usually captured through drilling vertical wells or horizontal piping
Gas comprised of 50 percent methane, 42 percent carbon dioxide, the rest nitrogen and oxygen compounds, is emitted as bacteria decomposes waste in landfills. Peak production is about a year after material is in the landfill, but can be generated for 20 years. LFG collection typically begins after a portion of the landfill is closed to incoming waste. The methane rises naturally to the top of the landfill and can be collected in wells, pipes, or a combination of other developing technologies. Once captured, gas is usually moved through a common pipe system to be heated, cooled, and filtered to remove dirt and other small particles. Gas can be used for electricity generation, heat or steam, or as an alternative fuel for vehicles. Most LFG energy projects produce electricity, although a growing number of combined heat and power (CHP) systems produce both, also known as co-generation.
2. LFG is converted to electricity through variety of technologies, but usually an internal combustion engine
Internal combustion engines are most commonly used to turn landfill gas into electricity, but gas turbines, (micro)turbines, stirling engines (external combustion engine), and fuel cells are also used. Some claim fuel cells as being the most environmentally friendly. According to the EPA, every million tons of municipal solid waste in a landfill is estimated to be able to produce approximately 432,000 cubic feet per day (cfd) of LFG, which, through various technologies, could generate approximately 0.78 megawatts (MW) of power or provide 9 million Btu per hour of thermal energy.
3. Using landfill gas for electricity is global
Germany is the world's top producer of energy from landfill gas; in 2009, Germany produced enough electricity from biogas to power 3.5 million homes. Sweden has even been operating a biogas-powered train since 2005. It shuttles passengers between two cities that are 75 miles apart. Projects are not limited to developed nations and international organizations such as the World Bank have coordinated various such projects around the world. The Gramacho Landfill in Brazil, financed by the clean development mechanism (CDM), was able to reduce emissions and generate $232 million worth of carbon credits, the total value of the methane emissions avoided by the landfill-to-electricity program.
4. Projects are more common in the U.S. than you think
There are 636 operational landfills gas-to-energy projects in the U.S. with an additional 450 identified as good candidates (map of projects by state as of January 2014 available here). California is utilizing landfill gas for energy the most, with 76 operational projects; followed by Illinois at 44 projects and North Carolina with 32. Texas and New York both have 29. However, NY has almost tapped out candidate landfills while another 49 have been identified in Texas. In the U.S., the EPA's Landfill Methane Outreach Program provides resources and support for LFG-to-energy projects including a benefits calculator to estimate direct, avoided, and total greenhouse gas reductions, as well as environmental and energy benefits.
5. Feasibility and cost-effectiveness depends on various factors
Not all landfills are good candidates for LFG to energy projects. According to the Global Methane Initiative, a country-level partnership to reduce methane emissions, the feasibility for a particular landfill depends on numerous technical and economic considerations, such as waste composition and volume, quality and quantity of the gas, availability and location of a suitable end user, project capital and operation and maintenance (O&M) costs, and financing options. Of course particular investment costs determine whether or not a LFG-to-energy project is implemented, but the benefits from landfill gas capture and use do include the creation of green jobs and revenues from the sale of the gas, making such operations attractive to private companies. Costs can also be reduced through selling carbon offsets for the amount of greenhouse gas emissions avoided through the project, as the Brazilian Gramacho Landfill demonstrates.
With the large amount of gas being produced in landfills (and sometimes causing fires and explosions in the sites), the gas-to-energy process offers a cost-effective and environmental solution to tackling greenhouse gas emissions and providing alternative fuel sources. We do expect more landfill gas-to-energy projects to come online and methane capture expectations to continue to increase, especially as the technology evolves and improves.