Biogas is another bio-based technology that harnesses natural sources and processes to produce renewable energy. Animal wastes such as cow manure naturally give off methane as they breakdown. Animal wastes can be processed in an anaerobic (air-free) digester, producing biogas, containing methane, which is used to power modified natural gas engines and generate electricity. The process also improves the fertilizer potential of the manure, too!
Biogas facilities are also sited at landfills, taking advantage of the methane potential of organic wastes that are being broken down. Landfills are already responsible for capturing and eliminating methane— a typical practice involve burning off the methane, producing the tall flames you sometimes see at landfill. Waste-to-methane energy plants go a step further, utilizing much of the same manure to methane technologies to harness that methane, turning trash into electricity. See all Bioenergy Members
According to the Department of Energy, the United States consumed 147 trillion btu of energy from landfill gas in 2003, around a half percent of national natural gas consumption. Worldwide, biogas is being upgraded to fuel-quality compressed and liquefied natural gasses, with 12,000 vehicles running on biogas throughout Europe in 2007. As of January 2014, AgSTAR estimates that there are approximately 239 anaerobic digester systems operating at commercial livestock farms in the United States.
Biogas in Vermont
Vermont currently has more digesters per dairy farm than any other state in the US. Nationally-recognized Vermont “Cow Power” manure-to-methane projects have highlighted the potential for this technology in our dairy-focused agricultural state, while supplying communities with renewable energy, one cow at a time. Currently GMP customers can opt to get a percentage of their electricity from manure-to-methane projects, with participating farms being added each year. Waste-to-methane projects are also well under way, with Washington Electric Cooperative’s 8 MW Coventry plant currently providing two thirds of their electrical capacity.
Across the state, innovative systems and projects are being put in place to harvest this pre-existing form of energy, with many utility customers already plugged in and powered up.
Visit Green Mountain Power for a list of Vermont Farms in the GMP Cow Power and Greener GMP Programs
Learn More About Biogas
- Download REV’s Biogas Educational Factsheet (pdf)
- Union of Concerned Scientists page on Biogas
- US Department of Energy, Energy Efficiency & Renewable Energy, Alternative Fuels and Advanced Vehicles Data Center
- “How it Works” animation from CVPS’ Cow Power Page
- Project brochure for Washington Electric Cooperative’s Coventry landfill gas to energy project (pdf).
- What is anaerobic digestion?
- Are biogas systems/anaerobic digesters only for farm use?
- Does biogas contribute to climate change?
- How much can I save switching to biogas?
Anaerobic digestion (AD) is a biological process that occurs when organic matter is decomposed by bacteria in an oxygen-free environment. This process produces biogas, which consists primarily of methane and carbon dioxide. This gas can be recovered, treated, and used to generate energy in place of traditional biofuels. AD systems are also often referred to as biogas systems. Ontario Ministry of Energy
No. Anaerobic digesters, although more commonly found on farms, can be used in other settings.
Anaerobic digestion can be used in food processing plants and can be similar to farm-based systems or they may be designed to remove organic matter from wastewater. Food processing systems are usually sized to meet either the heating requirements of the facility or to manage by-products produced on-site or from several food processing facilities. Ontario Ministry of Energy
Centralized anaerobic digestion systems are also found throughout Europe. Materials from farms and food processing plants are hauled to a centralized facility operating with a high bio-security hauling process. Other materials, such as source-separated organics, are often added to boost gas production. In many instances, heat from the centralized AD system is used nearby at another commercial facility or for heating residences.
Biodigesters have the potential to mitigate methane emissions by 1.8 million metric tons. While combustion of biogas, like natural gas, produces carbon dioxide (CO2), the carbon in biogas comes from plant matter that fixed this carbon from atmospheric CO2. Thus, biogas production is carbon-neutral and does not add to greenhouse gas emissions. Further, any consumption of fossil fuels replaced by biogas will lower CO2 emissions. University of Florida: Biogas
The profitability of a biogas digester depends on the size of the operation, the method of manure management and local energy costs. Any electricity that is not used on-site can usually be sold to the local utility.
Last updated July, 2014