Mogden sewage treatment works: Thames Water announces sewage sludge will heat homes in West London 'early this year'

Thames Water has announced that around 4,000 homes in West London will be heated using sewage sludge which has been branded as a “tremendous” and “untapped resource”. Cathryn Ross, CEO of the water company, said effluent within London alone “could generate 10 terawatt hours of wastewater heat.”

She added: “To give you a feel for that, that’s the equivalent of 40 per cent of Hinkley [Point] C [nuclear power station]. That’s a tremendous, untapped resource.”

The company confirmed that a "gas-to-grid" system at its Mogden sewage works in Isleworth will start converting sewage into biomethane "early this year". It has already established a similar facility at Deephams sewage works in Edmonton. Anna Boyle, the firm’s head of catchment at Mogden, said both projects had "set a remarkable example for environmental stewardship and innovation".

Sewage sludge is a by-product of the sewage treatment process which is then digested to produce biogas. This biogas is typically used to generate electricity, using Combined Heat and Power engines. But the new facility will mean that a portion of the biogas is instead taken and filtered so that it can be used as fuel for cooking and heating.

The project was mentioned in September last year by Ms Ross, who at the time was the company’s interim joint CEO. She said it was one of among many sustainability schemes Thames Water is pursuing. She told the London Assembly’s environment committee that the company has also been investigating whether it can directly extract heat from sewage.

At the time, the Henley Mermaids, a campaign group made up of five middle-aged women who share a passion for river swimming, told NationalWorld that the water company should be “focusing on investing in its own crumbling and inadequate sewerage infrastructure to end illegal sewage dumping” not powering homes using sewage. The group said that it is “great to hear novel ideas about using sewage to power homes” but we are “a very long way away” from that.

Councillor Katherine Dunne, deputy leader of Hounslow Council and cabinet member for climate, environment and transport welcomed Thames Water’s initiative. She said: “The Mogden Sewage Treatment Works upgrade will reduce carbon emissions from the plant and is another positive step on Hounslow’s Pathway to Net Zero. 

“Our commitment to bold climate action is unwavering, and we’ll continue to introduce measures that enable the retrofit of council-owned buildings, schools, and our social housing. We welcome Thames Water’s ambitious work to further decarbonise its estate and the positive impact this will have for local communities.”