Sewage Based Energy Plan Makes Progress

Proposal to use heat transferred from Mogden water treatment approved

The Mogden Sewage Treatment Works. Picture: Jim Linwood

March 27, 2025

A radical proposal to heat homes in the area using heat generated by water treatment processes has been given the go-ahead by Hounslow Council’s Cabinet.

A request to apply for up to £11m of funding from the Green Heat Network Fund has now been approved. If granted, the money will be used to work up detailed plans and subsidise what would be a £53m project that could be ready as early as 2029.

Once operational, the Hounslow Heat Network scheme would extract heat from water warmed by the treatment process at Mogden Sewage Works in Isleworth.

Cabinet Members heard that the treated water is typically about 20 degrees centigrade as it leaves the works to be discharged into the Thames. Heat could be extracted from this using a heat pump and transferred to clean water which would then be circulated to buildings in buried insulated pipes. Each building would have a heat exchanger, which transfers heat from the heat network pipe to its own heating system, much as a gas boiler would heat the water.

An additional benefit of the plan is that any environmental damage from pumping warm water into the Thames would be reduced.

The energy supplied by the network will initially heat around 30 major buildings, including those at the West Middlesex Hospital, workplaces, public buildings and large residential blocks. It is estimate that it could reduce carbon emissions by as much as 75 per cent compared to gas boilers.

If this is scheme is successful it is hoped ultimately to extend the scheme using private finance to invest £450million.

Councillor Katherine Dunne, Hounslow’s Cabinet Member for Climate, Environment & Transport, said, “Many buildings still rely on gas and we have seen very recently that can put us at the mercy of hugely expensive cost spikes in, even before we take account of the cost to the environment.

“This is certainly the lowest cost option for low carbon heating and there is absolutely no reason why we shouldn’t be doing it. This is tried and tested technology used extensively in Scandinavian countries for decades.

“For now, it’s too early to say if implementation will mean cheaper bills, but we believe it offers some protection against the wild fluctuations in energy prices that we’ve seen in the past few years.

“Eventually, we would like to consider rolling out the heat network to other areas of the borough.”