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Anaerobic Digestion
Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen.[1] The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the fermentation used industrially to produce food and drink products, as well as home fermentation, uses anaerobic digestion.
Anaerobic digestion occurs naturally in some soils and in lake and oceanic basin sediments, where it is usually referred to as "anaerobic activity".[2][3] This is the source of marsh gas methane as discovered by Alessandro Volta in 1776.[4][5]
The digestion process begins with bacterial hydrolysis of the input materials. Insoluble organic polymers, such as carbohydrates, are broken down to soluble derivatives that become available for other bacteria. Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids. In acetogenesis, bacteria convert these resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide amongst other compounds. Finally, methanogens convert these products to methane and carbon dioxide.[6] The methanogenic archaea populations play an indispensable role in anaerobic wastewater treatments.[7]
Anaerobic digestion is used as part of the process to treat biodegradable waste and sewage sludge. As part of an integrated waste management system, anaerobic digestion reduces the emission of landfill gas into the atmosphere. Anaerobic digesters can also be fed with purpose-grown energy crops, such as maize.[8]
Anaerobic digestion is widely used as a source of renewable energy. The process produces a biogas, consisting of methane, carbon dioxide, and traces of other 'contaminant' gases.[1] This biogas can be used directly as fuel, in combined heat and power gas engines[9] or upgraded to natural gas-quality biomethane. The nutrient-rich digestate also produced can be used as fertilizer.
With the re-use of waste as a resource and new technological approaches that have lowered capital costs, anaerobic digestion has in recent years received increased attention among governments in a number of countries, among these the United Kingdom (2011),[10] Germany,[citation needed] Denmark (2011),[11] and the United States.[12]
Gedling is a village and former civil parish which gives its name to the larger Borough of Gedling in Nottinghamshire, England. It lies 4 miles (6.4 km) north-east of Nottingham city centre. The parish was abolished in 1935 and absorbed into the urban district of Carlton, which in turn was abolished in 1974 on the creation of borough of Gedling. The population of the Gedling ward at the 2011 census was 6,817[1] and 111,787 for the district.[2] Gedling was recorded in the Domesday Book and is still a distinct settlement, although residential, commercial and industrial growth in the wider borough of Gedling and the neighbouring city of Nottingham, boroughs of Broxtowe and Rushcliffe and district of Ashfield (as well as the Derbyshire boroughs of Amber Valley and Erewash, which have become increasingly urban around Nottingham) means it can be difficult to distinguish the village of Gedling from the nearby town of Carlton, with which it has become contiguous.
Gedling was first settled around Saxon times, when the Saxon chief Gedl (hence the name Gedling, coming from the chief "Gedl" and "Ing" being Saxon for People, Gedl-Ing meaning "Gedl's People") sailed up the River Trent, and then up the Little Ouse dyke, until he could get no further upstream. He landed at the spot which is thought to be the present-day site of All Saints' Church. Gedling has had several versions of its name including Ghellinge, Gedlinga, Geddlings, and Gettang.
Despite being a fairly small place, Gedling gives its name to the local borough council which has its offices in nearby Arnold, and also to the local parliamentary constituency, which covers the suburbs to the east of Nottingham, including Arnold and Carlton. Village pubs are the Gedling Inn (once the Chesterfield Arms) and The Willowbrook on Main Road.
