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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]

​Yorkshire (/ˈjɔːrkʃər, -ʃɪər/; abbreviated Yorks), formally known as the County of York, is a historic county of Northern England and the largest in the United Kingdom.[3] Because of its great size in comparison with other English counties, functions have been undertaken over time by its subdivisions, which have also been subject to periodic reform. Throughout these changes, Yorkshire has continued to be recognised as a geographic territory and cultural region.[4] The name is familiar and well understood across the United Kingdom and is in common use in the media and the military,[5] and also features in the titles of current areas of civil administration such as North Yorkshire, South Yorkshire, West Yorkshire and the East Riding of Yorkshire.

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Within the borders of the historic county of Yorkshire are large stretches of unspoiled countryside, particularly within the Yorkshire Dales, North York Moors and Peak District national parks.[6] Yorkshire has been nicknamed "God's Own Country".[4][7][8]

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The emblem of Yorkshire is the White Rose of the English royal House of York, and the most commonly used flag representative of Yorkshire is the white rose on a blue field[9] which, after nearly fifty years of use, was recognised by the Flag Institute on 29 July 2008.[10] Yorkshire Day, held annually on 1 August, is a celebration of the general culture of Yorkshire, ranging from its history to its dialect.[11]

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Yorkshire is covered by different Government Office Regions. Most of the county falls within Yorkshire and the Humber while the extreme northern part of the county, such as Middlesbrough, Redcar, Holwick and Startforth, falls within North East England. Small areas in the west of the county are covered by the North West England region.