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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]

​Lincolnshire (abbreviated Lincs.) is a county in the East Midlands of England, with a long coastline on the North Sea to the east. It borders Norfolk to the south-east, Cambridgeshire to the south, Rutland to the south-west, Leicestershire and Nottinghamshire to the west, South Yorkshire to the north-west, and the East Riding of Yorkshire to the north. It also borders Northamptonshire in the south for just 20 yards (19 m), England's shortest county boundary.[2] The county town is the city of Lincoln, where the county council has its headquarters.

The ceremonial county of Lincolnshire consists of the non-metropolitan county of Lincolnshire and the area covered by the unitary authorities of North Lincolnshire and North East Lincolnshire. Part of the ceremonial county is in the Yorkshire and the Humber region of England, and most is in the East Midlands region. The county is the second-largest of the English ceremonial counties and one that is predominantly agricultural in land use. The county is fourth-largest of the two-tier counties, as the unitary authorities of North Lincolnshire and North East Lincolnshire are not included.

The county has several geographical sub-regions, including the rolling chalk hills of the Lincolnshire Wolds. In the south-east are the Lincolnshire Fens (south-east Lincolnshire), the Carrs (similar to the Fens but in north Lincolnshire), the industrial Humber Estuary and North Sea coast around Grimsby and Scunthorpe, and in the south-west of the county, the Kesteven Uplands, rolling limestone hills in the district of South Kesteven.