Banner Default Image

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]

​Sleaford (historically known as New Sleaford) is a market town and civil parish in Lincolnshire, England. Since 1973, the parish boundaries have included Quarrington to the south-west, Holdingham to the north and Old Sleaford to the east – contiguous settlements and former civil parishes which, with New Sleaford, had formed an Urban District. The town is on the edge of the fertile Fenlands, about 11 miles (18 kilometres) north-east of Grantham, 16 mi (26 km) west of Boston, and 17 mi (27 km) south of Lincoln. With a population of 17,671 at the 2011 Census, the town is the largest settlement in the North Kesteven district. Bypassed by the A17 and the A15, it is connected to Lincoln, Newark, Peterborough and King's Lynn. Sleaford railway station is on the Nottingham to Skegness (via Grantham) and Peterborough to Lincoln Lines.

The first settlement formed in the Iron Age where a prehistoric track crossed the River Slea. It was a tribal centre and home to a mint for the Corieltauvi in the 1st centuries BC and AD. Evidence of Roman and Anglo-Saxon settlement has been uncovered. In the medieval period, records differentiate between Old and New Sleaford, the latter emerging by the 12th century around the present-day market place and St Denys' Church; Sleaford Castle was also built at that time for the Bishops of Lincoln, who owned the manor. Granted the right to hold a market in the mid-12th century, New Sleaford developed into a market town and became locally important in the wool trade, while Old Sleaford declined.

From the 16th century, the landowners were the Carre family, who operated tight control over the town, and it grew little in the early modern period. The manor passed from the Carre family to the Hervey family by the marriage of Isabella Carre to John Hervey, 1st Earl of Bristol, in 1688. The town's common land and fields were legally enclosed by 1794, giving ownership mostly to the Hervey family; this coincided with the Slea's canalisation; the Sleaford Navigation brought economic growth until it was superseded by the railways in the mid-1850s. In the 20th century, the sale of farmland around Sleaford by Bristol Estates led to the development of large housing estates. The subsequent availability of affordable housing combined with the town's educational facilities and low crime rates made it an attractive destination for home-buyers. As a result, the town's population underwent the fastest growth of any town in the county in the 1990s.

Sleaford was primarily an agricultural town until the 20th century, supporting a cattle market, with seed companies, such as Hubbard and Phillips, and Sharpes International Seeds, being established in the late 19th century. The arrival of the railway made the town favourable for malting. Industry has declined, and in 2011 the most common occupations are in wholesale and retail trade, health and social care, public administration and defence and manufacturing. Regeneration of the town centre has led to the redevelopment of the old industrial areas, including the construction of the National Centre for Craft & Design on an old wharf.