Thames Water turns sewage sludge into electricity

Sewage sludge - the solid waste that is left over after sewage has been treated - is being turned into electricity by Thames Water. The electricity generated at 22 sewage treatment works will be pooled with other enterprises' "green" electricity and, from April 2000, will be available for purchase by businesses with power demands of less than 100kW.

Electricity is generated, in the most part, by combined heat and power (CHP) plants – more efficient than conventional gas-fired power stations – at Thames sewage treatment works. The CHP plants use methane given off by the sewage sludge to generate electricity.

At current rates of generation, Thames will contribute about 24MW of electricity, or enough to power 38,000 homes. Electricity is generated at Beckton Sewage Treatment Works in east London and at works in Oxford, Swindon and Slough.

An EU law banning the dumping of sewage sludge in the sea recently came into force and UK water companies have had to find other ways of getting rid of sludge. “We’re making a virtue of the law,” Andrew Boyd of Thames Water told edie. “It wasn’t a viable option in the Greater London area to use the sewage sludge on farm land, so we decided to use it to produce green energy. We hope to develop uses of the ash residue in products like building aggregates.”

The Renewable Energy Company will organise the sale of Thames Water’s electricity.

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