Wednesday, August 04, 2010
Britain's largest water and sewerage company generated a 14 per cent of its power needs from a combination of burning sewage sludge at some locations, and anaerobically digesting it at others, and then burning the methane derived from it.
Thames Water's Climate Change Strategy Manager, Dr Keith Colquhoun, is quoted as saying that their investment in renewable energy plants has been
"good news because we now 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 spent on energy last year alone, saving money for customers."
"Our goal is to cut greenhouse emissions by 20 per cent on 1990 levels by 2020 - that's about 200,000 tonnes less CO2. By using sludge derived 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 the fact that combating climate change is no longer about talk. It's about all of us taking action - and in our case, that includes sludge power."
Thames Water - which has the largest renewable electricity generation capacity inside the M25 motorway ring, excluding the commercial electricity generators - uses two methods to generate power from sewage:
1. Thermal destruction with energy recovery, where sewage sludge, which is the solid content of the sewage dried into blocks of 'poo cake', is burned to generate power; and
2. Anaerobic digestion, or (with) CHP (combined heat and power) generation, which is where methane derived from sewage sludge is burned to created heat, which in turn generates power.
The following Thames Water sewage works have AD/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).
And the following two works use thermal destruction:
Beckton, in East London north of the River Thames, Europe's largest sewage works, which treats about 3.5 million people's waste every day; and Crossness, in East London south of the river, which treats the human equivalent of 2 million people's waste.
After it has been used to generate electricity, Thames Water then offers the remaining sewage sludge to farmers to use as fertiliser, or to developers as landscaping material or soil improver. In 2008/09 the firm put 100 per cent of its sewage sludge to beneficial use, sending none of it to landfill and as a result saving millions of pounds in UK landfill tax.
Further details about using sludge to generate power and Thames Water's 100 % win-win utilisation of sludge for renewable energy production can be found in the company's Corporate Responsibility Report