Biogas Generation by Anaerobic Digestion

June 8, 2016

Being in the construction industry we get to work on a lot of ground-breaking projects.  With renewable energy close to our hearts, in addition to wind turbines, we enjoy working on biogas installations.  Here’s a little more about the fascinating subject.

What is biogas?

Biogas is a mixture of carbon dioxide and methane. It can be used as a relatively low-cost fuel for the generation of energy and heating. Biogas is a renewable fuel, so it qualifies for renewable energy subsidies. It is currently used in a combined heat and power plant or cleansed of carbon dioxide and injected into the National Grid.
It is possible to concentrate the methane within biogas to the same quality standards as fossil fuel derived natural gas to produce biomethane. If concentrated and compressed this biogas can then be used in vehicle transportation. Compressed biogas is becoming widely used in Sweden, Switzerland, and Germany for cars, trucks and trains. Biogas is estimated to have the potential to replace around 17% of vehicle fuel in the UK through a series of specially adapted cars.

How is biogas made?

Biogas is made through a process called anaerobic digestion (AD). This involves a series of natural biological processes whereby organic waste material – known as feedstock – is broken down by micro-organisms and converted into biogas.
The biogas is used in a combined heat and power plant or cleansed of carbon dioxide and injected into the National Grid. A by-product of the AD process is digestate. Digestate is a stable, nutrient-rich substance that is most commonly used as a renewable fertiliser or a soil conditioner.

Sources of Feedstock for the production of biogas:

  • organic waste from the food processing industry
  • organic waste from agricultural sources
  • post-consumer organic waste, broken down into municipal, household waste and waste from industrial and commercial sources including hotels, supermarkets, prisons, schools and hospitals.

Why support the building of AD plants?

  • plenty of feedstock with over 7m tonnes domestic waste each year and a further 12m tonnes by the commercial and industrial food industry
  • The Government has committed that by 2020, biological material sent to landfill sites must be at 35% of the levels recorded in 1995
  • there is currently a shortfall in residual waste treatment facilities, such as anaerobic digestion plants which give value to resources currently wasted on landfill
  • by 2014, producers of biodegradable and organic waste face the possibility of their landfill tax (a tax on the disposal of waste to landfill sites) rising to £80 per tonne (up from £40 per tonne in 2009)
  • renewable energy generation not reliant on weather unlike wind and solar

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