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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]
Weymouth /ˈweɪməθ/ is a seaside town in Dorset, on the English Channel coast of England. Situated on a sheltered bay at the mouth of the River Wey, 11 kilometres (7 mi) south of the county town of Dorchester, Weymouth had a population of 53,068 as of 2018. It is the third largest settlement in Dorset after Bournemouth and Poole.
The history of the town stretches back to the 12th century and includes roles in the spread of the Black Death, the settlement of the Americas and the development of Georgian architecture. It was a major departure point for the Normandy Landings during World War II. Prior to local government reorganisation in April 2019, Weymouth formed a borough with the neighbouring Isle of Portland. Since then the area has been governed by Dorset Council. Weymouth, Portland and the Purbeck district are in the South Dorset parliamentary constituency, which elects one Member of Parliament: as of 2021, the Conservative Richard Drax.
A seaside resort, Weymouth and its economy depend on tourism. Visitors are attracted by its harbour and position, halfway along the Jurassic Coast, a World Heritage Site, important for its geology and landforms. Once a port for cross-channel ferries, Weymouth Harbour is now home to a commercial fishing fleet, pleasure boats and private yachts, while nearby Portland Harbour is the location of the Weymouth and Portland National Sailing Academy, where the sailing events of the 2012 Olympic Games and Paralympic Games were held.
