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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.
Wiltshire (/ˈwɪlt.ʃər, -ʃɪər/;[1] abbreviated to Wilts) is a ceremonial county in South West England. It borders Gloucestershire to the north, Oxfordshire and Berkshire to the east, Hampshire to the south-east, Dorset to the south, and Somerset to the west. The largest settlement is Swindon, and Trowbridge is the county town.
The county has an area of 1,346 sq mi (3,490 km2) and a population of 720,060. The county is mostly rural, with the centre and south-west sparsely populated. After Swindon (183,638), the largest settlements are the city of Salisbury (41,820) and the towns of Chippenham (37,548) and Trowbridge (37,169). For local government purposes the county comprises two unitary authority areas: Swindon and Wiltshire.
Undulating chalk downlands characterize much of the county; the North Wessex Downs in the east, Salisbury Plain in the centre and Cranbourne Chase in the south. The north-west is part of the Cotswolds, a limestone area. The county's major rivers are both called the Avon: the northern Avon enters the county in the north-west and flows in a southwesterly direction before leaving it near Bradford-on-Avon; the southern Avon rises on Salisbury Plain, flows through Salisbury and then into Hampshire.
Salisbury Plain is noted for the Stonehenge and Avebury stone circles, which together are a UNESCO World Heritage Site, and other ancient landmarks. Much of the plain is a training area for the British Army. The city of Salisbury is notable for its medieval cathedral. Large country houses open to the public include Longleat, where there is also a safari park, and the National Trust's Stourhead.
