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.
The Metropolitan Borough of Walsall is a metropolitan borough in the West Midlands, England. It is named after its largest settlement, Walsall, but covers a larger area which also includes Aldridge, Bloxwich, Brownhills, Darlaston, Pelsall and Willenhall. It also serves as the post town for nearby Cannock Chase District and Lichfield District respectively.
The borough had an estimated population of 254,500 in 2007.[2]
The current boundaries were set as part of the provisions of the Local Government Act 1972, with a change to the north of the borough in 1994.[3] It is bounded on the west by the City of Wolverhampton, the south by the Metropolitan Borough of Sandwell, to the south east by the City of Birmingham, and by the Staffordshire districts of Lichfield, Cannock Chase and South Staffordshire to the east, north and northwest respectively. Most of the borough is highly industrialised and densely populated, but areas around the north and east of the borough are open space.
In 1986 the borough became an effective unitary authority when the West Midlands County Council was abolished. However it remains part of the West Midlands for ceremonial purposes, and for functions such as policing, fire and public transport.