Heat recovery from sewage offers low-carbon energy from waste

Heat recovery from sewage offers low-carbon energy from waste.
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HEAT derived from treated sewage water could be used to heat a housing estate in a first for the UK. Using excess heat recovered from water treatment plant discharge, some 2 000 homes will be able to benefit from a low-carbon energy source.

Extracting heat from sewage

The scheme is under development by a partnership between water utility company Thames Water and the local council for Kingston upon Thames in the south eastern UK.

A first of its kind in England, the so-called “poo power” scheme is part of the planned regeneration of Kingston’s Cambridge Road Estate, including a district heating network.

Under the plans, heat exchangers will recover energy from around a third of the final effluent from the Hogsmill sewage treatment works, which serves some 380 000 Thames Water customers.

Heated from bathing, cooking and other uses, currently the temperature of the final effluent is typically around 10-15°C year-round.

Once the heat recovery scheme is operating the effluent temperature will be chilled to be closer to ambient temperatures while the heat extracted will be circulated in a district network at more than 65°C.

If successful, up to 7GWh of heat could be recovered every year, saving some 105 000 tons of carbon dioxide equivalent emissions over the estimated 30-year lifespan of the project.

Expanding the role of poo power

Once the system is installed it is anticipated that the heating network will expand to include additional public and commercial buildings in Kingston town centre.

“This is ground-breaking. It’s a first for England and shows we are serious about reducing carbon in the borough. This is a real opportunity,” said councillor Caroline Kerr, leader of Kingston Council.

A final decision on the project is due in the coming months and follows on from extensive feasibility studies over the last two years funded by both the UK central government and the Greater London Authority.

This funding also covered preliminary design work. In the meantime, Thames Water has submitted an application for capital funding from the government. A formal decision on this funding application is due this month.

“Renewable heat from our sewer network is a fantastic resource,” said Sarah Bentley, Thames Water’s chief executive officer. She added: “We’re confident innovative district heating schemes like this will offer… opportunities to ensure we leave our planet in a better place for future generations.”

Renewable energy sources such as bioenergy, wind and solar, currently generates around a quarter of Thames Water’s electricity needs, saving around £40 million in energy costs each year. The company aims to achieve net zero carbon emissions by 2030.

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