Biogas

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Figures from the U.K. Government and the biogas industry show that generating gas from waste can produce cheaper energy in the short term with fewer carbon emissions than current controversial hydraulic fracturing projects. Economic, social and environmental factors necessitate managing organic waste to a new level. Demand for biogas – renewable energy digested from biomass – is expected to soar as the United Kingdom (U.K.) faces up to climate change challenges.

Biogas is (50/50) methane and carbon dioxide (CO2), a product of the natural decomposition of any organic substance of animal or plant origin due to the activity of anaerobic bacteria functioning in a non-oxygen environment.

Figures from the U.K. Government and the biogas industry show that generating gas from recycling plant and animal nutrients can produce cheaper energy in the short term with fewer carbon emissions than current controversial hydraulic fracturing projects, emission savings of 7.5m+ tonnes of CO2 a year. Biogas can replace firewood or fossil fuels, which are becoming more expensive as supply struggles to keep up with demand. Biogas production saves the space required to store and utilize waste. The economy may miss out on up to £3bn a year and 35000 jobs by failing to exploit biogas.

The Committee on Climate Change estimates that 5% of the U.K.’s domestic gas needs could be supplied with gas from biomass and waste by 2020. The Anaerobic Digestion and Biogas Association calculates that it could be twice as much. At present about one million tonnes of waste is used to generate biogas using anaerobic digestion techniques. Waste would otherwise be sent to landfill or decompose. The U.K. throws away 15 million tonnes of food waste a year, for example from homes, schools, industry and retail outlets. 90 million tonnes of animal waste is also produced in the U.K. each year, only a tiny portion of which is used for energy production. A full third of the world’s food is wasted. Discarded food accounts for a staggering amount of planet-warming greenhouse gas emissions.

A wide variety of materials (substrates) are used to generate biogas for heat and power production and other uses in Europe.

Common Substrates

Residues from food production – apple juice, wine, oil, sugar
Residues from alcohol production – beer, brewer grains
Residues from food and vegetable packing plants
Residues from biofuel production
Off-specification batches from the food industry i.e. expired best-before, production errors
Leftovers – restaurants, greenhouses, milk and dairy production
Excrement – animal, human, manure, silage, abattoir waste
Plant material and energy crops – maize, wheat, sugar beets, grains, grass, straw

Producing biogas from energy crops – maize and grass silage, for example – or liquid manure is controversial due to high energy usage. It is claimed that biogas should be produced solely from organic residues and waste materials.

Substrates are fed into digesters, where they are heated and agitated to produce biogas, which bubbles to the top and is collected in a container. The biogas is then fed into a cogenerator which produces electricity and heat. The remaining substrates can be used as high-quality eco-fertilizer. European farmers are investing in biogas production, to power dairies for example, particularly in Germany, which is home to more than 80% of European production of biogas from biomass.

Biogas can be used as a transport fuel in specially adapted vehicles. For example, wheat can be fermented and mixed with petrol to produce greener fuel (bioethanol). Water is added to flour crushed from wheat and brewed into beer. The alcohol is distilled out for fuel and the solids are turned into animal feed to go to U.K. farms.

In the U.K. there are currently only 40 megawatts-worth of new biogas projects under construction and a similar number awaiting planning permission. Projects capable of producing a further 180MW have been given the green light. That would double current production, approximately 8% of total biomass use, still tiny compared to a typical fossil fuel power station.

Drax Power Station in North Yorkshire is the U.K.’s largest coal plant with a capacity of 4,000MW. Drax has a £700 million programme underway to convert three of the plant’s six units to biomass. It is one of two preferred bidders in the long-running Carbon Capture and Storage Commercialisation Programme Competition. Gas-fired Peterhead Power Station is the other final entry.

Leila Deen, energy campaigner at Greenpeace, says: “With the right policies in place, biogas could provide up to half the U.K.’s domestic heat, reduce landfill and help us achieve our climate change targets. But David Cameron is too tipsy on the fracking kool-aid to acknowledge the potential of biogas. If his government put half as much effort into incentivising green energy as it does into foisting fracking on communities that don’t want it, the U.K. would be well on its way to long-term energy security. Biogas would help farmers and people in rural communities, rather than incensing them.”

Diageo’s £17m bioenergy plant at the Roseisle Scotch whisky distillery on Speyside, Scotland, won the award for Renewable Energy Project of the year at the 2013 BusinessGreen Leaders Awards. The plant opened in 2010, and now provides clean water, heat from waste and half of Roseisle’s electricity needs. The site’s carbon emissions have been reduced by around 13,000 tonnes a year. Water consumption is minimised through a closed loop on the distillery condensers. The innovative plant combines a range of clean technologies, including anaerobic digestion to convert the draff and pot ale by-products into methane, which is fed into a biomass boiler. Roseisle is the first malt whisky distillery in the industry to generate renewable energy from its co-products. Diageo is now poised to open a giant bioenergy plant at the Cameronbridge distillery in Scotland. It will reduce total company CO2 emissions by 5%+ by the end of 2014.

Biomass footnote

At the dawn of the millennium, 70% of the residents in Aberdeen’s tower blocks suffered from fuel poverty. In 2002 the City Council set up Aberdeen Heat and Power Ltd. to provide cheap power, created by burning waste material and using green technology for hyper-efficient energy conservation. Today hundreds have been taken out of fuel poverty. The Council are now extending the scheme elsewhere in the city. This initiative has won a Global Climate Award from the International Energy Agency. A not-for-profit enterprise, Aberdeen Heat and Power Ltd. is the first UK company to win the award.

http://www.aberdeenheatandpower.co.uk/

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