Minnesota is blessed with an abundance of renewable energy resources to provide a clean energy future for our state. An often overlooked renewable energy resource is biogas. Biogas holds tremendous potential to help meet our future energy needs. As a versatile and constant energy resource, biogas can be produced from organic feedstocks such as manure, crop residues, and a variety of wastes from food (particularly milk) processing, wastewater treatment, biomass processing byproducts (such as ethanol stillage or biodiesel glycerol), fats, oils and greases. Once biogas is produced, it can be converted into usable forms of energy on a constant basis. It can be utilized for electricity, combined heat and power, natural gas replacement, vehicle fuel and chemical production. Conservative calculations estimate that biogas energy could replace up to 5% of Minnesota’s electricity or natural gas use.
The dominant technology used to produce biogas is anaerobic digestion. An anaerobic digester vessel is heated to accelerate the biological breakdown of organic feedstocks using bacteria, and gas released from the feedstock decomposition is collected and utilized for energy. On-farm projects in Minnesota have begun to utilize anaerobic digestion technology to produce biogas for electricity production. A 250-cow dairy operation in Stearns County is collecting manure from 130 milk cows and adding cheese whey, a by-product of milk processing, from a local processing plant to successfully produce and sell electricity to a local electric utility. There are an additional four on-farm anaerobic digestion projects in Minnesota today. These projects are not only supplying a source of clean, renewable power but the agricultural producers are able to offset their energy use, sell the excess to a local utility and reduce methane emissions (a greenhouse gas with 25 times more heat trapping potential than carbon dioxide).
City sewers carrying household sewage and wastewater to treatment facilities hold another powerful source of biogas production that could be converted into useable forms of energy. A wastewater treatment facility in Fergus Falls is adding thick corn stillage syrup from a local ethanol plant to wastewater sludge to produce six million cubic feet of biogas a year. The biogas is used to offset conventional natural gas used by the plant, saving thousands of dollars every month for the municipal plant.
Landfills provide an additional source of biogas production. Because landfills are the second largest source of human-related methane emissions, landfill gas recovery projects are a critical greenhouse gas reduction strategy. As trash decomposes and methane is released, landfill gas recovery projects can capture that methane and use it to produce electricity and/or heat. Currently Minnesota has six operational landfill gas recovery projects and an additional eight are planned for future development.
Biogas is a unique renewable resource because it can provide energy on a constant basis and destruct or avoid heat-trapping methane emissions. The time is ripe for biogas development to increase in Minnesota. Technology advancements in recent years have diversified ways to produce and use biogas. It is time for biogas to step into the spotlight and become a significant part of our clean energy future.
Great Plains Institute
American Biogas Council