THE recent waste strategy review by the Department of Environment food and rural affairs (Defra) states that the "UK produces approximately seven million (five in England) tonnes of food waste per year and about 90 million (40-60 in England) tonnes animal slurry and manure that could realistically be available for utilisation by anaerobic digestion (AD) technology."

The review also states that "in England this could generate at least 3-5 TWh electricity per year by 2020 (a heat equivalent of 6-10TWh). 1TWh is equivalent to 1,000 million 1Kilowatt electric fires left running for an hour. A typical household uses three to 4,000KWhr and this is equivalent to over 1 per cent U.K electricity production. AD can be extended to include food industry and catering wastes which would reduce cost of collection and provide much greater quantities of renewable energy and reduce carbon emissions by displacing fossil fuels.

Collection of food waste and in-vessel composting as practiced in Gloucestershire at present adds significant carbon emissions. It also increases the carbon footprint of garden waste which previously was composted either at home or if collected, centrally in windrows. Capturing the biogas from one tonne of food waste will save between 0.5 and 1 tonne of CO2 equivalent.

The UK water industry treats 66 per cent of sewage sludge by AD, generating in the region of 1TWh per year of electricity in 2010. AD is widespread in countries such as India and China, even small domestic and village scale installations producing valuable biogas for cooking and running irrigation pumps. AD is also widespread in Europe. Biogas from AD is purified and injected into mains gas in Germany and Sweden to supplement imports and reduce cost.

AD is not rocket science and believe it or not there were AD installations in Victorian times in many parts of the world with the gas used to light street lamps.

The present arrangements for garden and food waste collection and treatment in Gloucestershire is environmentally harmful, is unsustainable, and adds significantly to the council tax paid by our citizens who have been kept in the dark by the authorities regards its true cost and environmental impact.

– Venk Shenoi, Blaisdon.