Biogas
Biogas is a gaseous renewable energy source[1] produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste, wastewater, and food waste. Biogas is produced by anaerobic digestion with anaerobic organisms or methanogens inside an anaerobic digester, biodigester or a bioreactor.[2]
The gas composition is primarily methane (CH
4) and carbon dioxide (CO
2) and may have small amounts of hydrogen sulfide (H
2S), moisture and siloxanes. The methane can be combusted or oxidized with oxygen. This energy release allows biogas to be used as a fuel; it can be used in fuel cells and for heating purpose, such as in cooking. It can also be used in a gas engine to convert the energy in the gas into electricity and heat.[3]
After removal of carbon dioxide and hydrogen sulfide it can be compressed in the same way as natural gas and used to power motor vehicles. In the United Kingdom, for example, biogas is estimated to have the potential to replace around 17% of vehicle fuel.[4] It qualifies for renewable energy subsidies in some parts of the world. Biogas can be cleaned and upgraded to natural gas standards, when it becomes bio-methane. Biogas is considered to be a renewable resource because its production-and-use cycle is continuous, and it generates no net carbon dioxide. From a carbon perspective, as much carbon dioxide is absorbed from the atmosphere in the growth of the primary bio-resource as is released, when the material is ultimately converted to energy.
Legislation[edit]
European Union[edit]
The European Union has legislation regarding waste management and landfill sites called the Landfill Directive.
Countries such as the United Kingdom and Germany now have legislation in force that provides farmers with long-term revenue and energy security.[47]
The EU mandates that internal combustion engines with biogas have ample gas pressure to optimize combustion, and within the European Union ATEX centrifugal fan units built in accordance with the European directive 2014–34/EU (previously 94/9/EG) are obligatory. These centrifugal fan units, for example Combimac, Meidinger AG or Witt & Sohn AG are suitable for use in Zone 1 and 2 .
United States[edit]
The United States legislates against landfill gas as it contains VOCs. The United States Clean Air Act and Title 40 of the Code of Federal Regulations (CFR) requires landfill owners to estimate the quantity of non-methane organic compounds (NMOCs) emitted. If the estimated NMOC emissions exceeds 50 tonnes per year, the landfill owner is required to collect the gas and treat it to remove the entrained NMOCs. That usually means burning it.
Because of the remoteness of landfill sites, it is sometimes not economically feasible to produce electricity from the gas.[48]
There are a variety of grants and loans the support the development of anaerobic digestor systems. The Rural Energy for American Program provides loan financing and grant funding for biogas systems, as does the Environmental Quality Incentives Program, Conservation Stewardship Program, and Conservation Loan Program.[49]
Global developments[edit]
United States[edit]
With the many benefits of biogas, it is starting to become a popular source of energy and is starting to be used in the United States more.[50] In 2003, the United States consumed 43 TWh (147 trillion BTU) of energy from "landfill gas", about 0.6% of the total U.S. natural gas consumption.[39] Methane biogas derived from cow manure is being tested in the U.S. According to a 2008 study, collected by the Science and Children magazine, methane biogas from cow manure would be sufficient to produce 100 billion kilowatt hours enough to power millions of homes across America. Furthermore, methane biogas has been tested to prove that it can reduce 99 million metric tons of greenhouse gas emissions or about 4% of the greenhouse gases produced by the United States.[51]
The number of farm-based digesters increased by 21% in 2021 according to the American Biogas Council.[52] In Vermont biogas generated on dairy farms was included in the CVPS Cow Power program. The program was originally offered by Central Vermont Public Service Corporation as a voluntary tariff and now with a recent merger with Green Mountain Power is now the GMP Cow Power Program. Customers can elect to pay a premium on their electric bill, and that premium is passed directly to the farms in the program. In Sheldon, Vermont, Green Mountain Dairy has provided renewable energy as part of the Cow Power program. It started when the brothers who own the farm, Bill and Brian Rowell, wanted to address some of the manure management challenges faced by dairy farms, including manure odor, and nutrient availability for the crops they need to grow to feed the animals. They installed an anaerobic digester to process the cow and milking center waste from their 950 cows to produce renewable energy, a bedding to replace sawdust, and a plant-friendly fertilizer. The energy and environmental attributes are sold to the GMP Cow Power program. On average, the system run by the Rowells produces enough electricity to power 300 to 350 other homes. The generator capacity is about 300 kilowatts.[53]
In Hereford, Texas, cow manure is being used to power an ethanol power plant. By switching to methane biogas, the ethanol power plant has saved 1000 barrels of oil a day. Over all, the power plant has reduced transportation costs and will be opening many more jobs for future power plants that will rely on biogas.[54]
In Oakley, Kansas, an ethanol plant considered to be one of the largest biogas facilities in North America is using integrated manure utilization system (IMUS) to produce heat for its boilers by utilizing feedlot manure, municipal organics and ethanol plant waste. At full capacity the plant is expected to replace 90% of the fossil fuel used in the manufacturing process of ethanol and methanol.[55][56]
In California, the Southern California Gas Company has advocated for mixing biogas into existing natural gas pipelines. However, California state officials have taken the position that biogas is "better used in hard-to-electrify sectors of the economy-- like aviation, heavy industry and long-haul trucking".[57]
Society and culture[edit]
In the 1985 Australian film Mad Max Beyond Thunderdome the post-apocalyptic settlement Barter town is powered by a central biogas system based upon a piggery. As well as providing electricity, methane is used to power Barter's vehicles.
"Cow Town", written in the early 1940s, discusses the travails of a city vastly built on cow manure and the hardships brought upon by the resulting methane biogas. Carter McCormick, an engineer from a town outside the city, is sent in to figure out a way to utilize this gas to help power, rather than suffocate, the city.
Contemporary biogas production provides new opportunities for skilled employment, drawing on the development of new technologies.[122]