Jobs
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]
Braintree is a town in Essex, England, and is the principal settlement of Braintree District. It is located 10 miles (16 km) north-east of Chelmsford, 15 miles (24 km) west of Colchester and 35 miles (56 km) north-west of Southend-on-Sea. According to the 2021 Census, the town had a population of 43,492; the urban area, which includes Great Notley, Rayne, Tye Green and High Garrett, had a population of 55,793.[1]
Braintree district has four market towns, picturesque villages, a designer shopping outlet, historic houses and gardens.
The town has grown contiguously with several surrounding settlements. The original settlement and parish of Braintree lay on the River Brain and was bounded on the north by Stane Street, the Roman road from Braughing to Colchester. North of that road was the parish of Bocking. The two parishes were united in 1934 as the parish and urban district of Braintree and Bocking, which was subsequently abolished in 1974 when the modern Braintree District was created. Several local organisations still include Braintree and Bocking in their names.[nb 1]
Braintree is bypassed by the modern-day A120 and A131 roads, while trains serve two stations in the town, at the end of the Braintree Branch Line from Witham.
The town is twinned with Pierrefitte-sur-Seine, France,[2] and gives its name to the towns of Braintree, Massachusetts and Braintree, Vermont, in the United States.[2]
