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Thames uses evacuation for electrification

Thames Water has reported saving some £15M in its electricity bills by using human waste to generate power.

The company generates some 14% of its power from either burning sewage sludge or methane derived from it.

Thames Water’s climate change strategy manager, Dr Keith Colquhoun, said: “There’s no polite way of saying this but what we produce - our poo - isn’t simply waste, it’s a great source of energy. That’s good news because we treat 2.8 billion litres of sewage every day at our 349 sewage works. The solids in sewage have a high calorific content that we use to generate electricity.

“And this isn’t a gimmick: as well as helping us to be more sustainable as a company, it also saves money - £15M less of customers’ cash spent on National Grid energy last year alone, which ultimately has a downward pressure of bills.

“Our goal is to cut greenhouse emissions by 20% on 1990 levels by 2020 - that’s about 200,000 tonnes less CO2. By using poo power and other renewable energy sources, we’re making significant progress towards this target after cutting emissions by five per cent in the past two years, despite grid energy becoming more carbon-intensive.

“Delegates at the Copenhagen Climate Change Summit must face that fact that combating climate change is no longer about talk. It’s about all of us taking action - and in our case, that includes poo power.

Thames Water has the largest renewable electricity generation capacity within the M25, using:

  • Thermal destruction with energy recovery, where sewage sludge, which is the solid content of the sewage after it has been dried and processed into blocks of ‘poo cake’, is burned to generate power
  • Anaerobic digestion, or CHP (combined heat power) generation, which is where methane derived from sewage sludge is burned to created heat, which in turns generates power.

The following Thames Water sewage works have CHP plants: Maple Lodge (Rickmansworth), Mogden (Isleworth), Rye Meads (Herts), Deephams (Edmonton), Oxford, Reading, Long Reach (Dartford), Slough, Hogsmill (Kingston), Beddington (Surrey), Swindon, Bishops Stortford, Banbury, Aylesbury, Basingstoke, Bracknell, Camberley, Crawley, East Hyde (Luton) and Wargrave (Berks).

Two plants use thermal destruction: Beckton in north east London - Europe’s largest sewage works, and Crossness in south east London.

Sewage sludge is finally offered to farmers to use as fertiliser or to developers as landscaping material or soil improver.

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