Methane is a greenhouse gas that contributes to global warming and climate change. Methane dissipates in the atmosphere more quickly than carbon dioxide, but is 20 times more effective at trapping heat.
Methane is the primary component of natural gas, which produces less carbon dioxide emissions than other fossil fuels when burned. Methane is also a byproduct of waste decomposition. When agricultural and municipal waste break down in anaerobic environments methane gas is produced. New recovery technologies enable the capture and use of this biogas as a fuel source--reducing greenhouse gas emissions.
Methane as Biogas
When animal manure is placed in an oxygen-deprived environment, such as an anaerobic reactor, bacteria decompose the organic material to produce methane. Untreated biogas rises to the top of the anaerobic reactor where it is captured. Untreated biogas can be used in place of fossil fuels to run the reactor, which requires heat, and used in other farm operations. Some of the biogas is flared to control odor but the remaining gas can be used to run natural gas turbines to generate electricity. Other organic material, like food or cheese whey from dairy processing plants, can be added to the reactor to reduce waste volumes and increase methane output.
Agricultural methane recovery is considered a renewable resource and is particularly important to rural areas in meeting increased voltage demand because it originates there; the electric grid is unnecessary to transfer the energy from the source. Biogas facilities also qualify as carbon offset projects; owners can sell carbon credits.
Landfills also produce methane. About 23 percent of all methane emissions come from solid waste landfills. Similar to biogas facilities, waste decomposition within the landfill produces about 50 percent methane and 50 percent carbon dioxide. The methane is extracted from landfills via wells, blower and flares, and vacuum systems. The methane flows to a central point for processing and treatment.
Landfills can transfer natural gas directly to power plants that burn methane to generate electricity. Recovered methane can also be transported to industrial and manufacturing facilities, reducing fossil fuel use. In 2008, there were 480 landfill methane recovery operations in the United States. Forty more landfills could be retrofitted to recover methane.
Coal bed methane, oil and natural gas operations all produce methane gas. These industries have implemented technologies to recover methane during exploration, transport and delivery processes via specialized well heads and valve designs. Recovered methane is often used to run operations on-site, reducing greenhouse gas emissions.
Recovered methane can be converted to compressed natural gas and liquefied natural gas for vehicle fuel. Natural gas produces less carbon dioxide emissions. Vehicles are large contributors to greenhouse gas emissions, but it is difficult to develop natural gas fueling stations. Government vehicle fleets are an excellent choice for natural gas because central fueling depots are easy infrastructure developments for municipal agencies.
Methane recovery replaces fossil fuel use under certain circumstances, in rural areas, near municipal landfills and government truck fleets. Methane recovery makes it possible to reduce greenhouse gas emissions and solve some energy problems in rural and municipal areas.
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