The world continues to seek new methods to generate and store electricity. There is no perfect solution. Challenges include reliability, renewability and greenhouse gas emissions. This series seeks to explore those questions. This month, we look at landfill gas.
Landfill gas (also called biogas) is produced by decomposing solid waste. That gas can be captured and used to operate electric generators. The process isn’t perfect but it’s an effective way turn pollutants into a useful fuel and ultimately, into electricity.
When waste is buried at a landfill, gases begin forming within around six months and may continue to be produced for many years into the future. As long as humans create waste, biogas will be produced, as it is the natural consequence of decomposition. It is composed primarily of methane (CH4) and carbon dioxide (CO2). Both of those are considered greenhouse gases. Methane is the same energy-dense material found in Natural Gas. Landfills are the third largest source of methane in the United States.
At some municipal landfills, biogas simply vents through the ground into the atmosphere. Most landfills use a system to tap and “flare” the gas off in small bursts of flame. Flaring does help limit greenhouse gas emissions but fails to make use of potential chemical energy.
Many modern landfills have begun capturing the gas to power boilers, dryers or electric generators.
A standard landfill gas capture system consists of vertical wells drilled into each acre of buried waste. These well heads can capture 60% - 80% of the gas being produced and channel it into tanks where impurities are removed. This process has the added benefit of reducing odor and other hazards associated with emissions. The gas can then be used generators that have been built specifically to burn methane gas.
Many landfill gas operations have an up-time of 95%, meaning they can reliably and predictably produce power whenever needed. The facilities are fairly small compared to other electrical generation sources. In 2018, landfill gas produced less than 1% of the electricity in the United States, but these plants are able to turn a pollutant into a much cleaner energy source.
For more information, visit: www.eia.gov
- Methane can be captured from landfills, sewage treatment plants, paper mills and food processing plants
- The Coffin Butte Landfill Gas Generation Project is located near Corvallis, Oregon. They began operations in 1995 as a way for electric cooperatives to offer a renewable power subscription to their customers
- Five large engines have been converted to operate on methane instead of diesel to make electricity
- Coffin Butte landfill maintains over 300 gas wells and the generation facility produces 5.66 megawatts of power — enough to provide electricity to around 4,000 homes
- The facility is owned and operated by PNGC Power and Clearwater Power customers have access to this renewable resource