Fuel from sewage plant claims a UK first

The water company’s £1.5m sewage sludge dryer in Slough claims to be the first facility in the UK to produce fuel from sewage, rather than just reducing the volume of waste, with the aim of contributing to Britain’s low carbon economy.

As part of the process, five tonnes of sewage sludge, 20% of the solids left over from the treatment process at the Slough works, are dried and turned into woodchip-like flakes by heating to around 180 degrees centigrade each day and dried off using heated rotating paddles. This creates a highly-combustible renewable fuel which burns in a similar way to woodchip.

However, as the flakes are 95% dry they burn more easily than the usual fuel of 25% dried sludge cakes. The flakes are then fed into a sludge-powered generator at Crossness sewage works, Bexley and burnt to generate electricity.

According to Thames Water, as the flakes are drier than the cake less non-renewable gas is needed to keep the fire going, making it a more energy efficient process.

Thames Water’s head of innovation, Rupert Kruger, said: “This is the first time in Britain that a waste dryer has been used to create ready-to-burn fuel from sewage sludge, rather than simply being used as a waste-reducer.

“This innovative approach demonstrates our clear intent to help move Britain towards becoming a low-carbon economy by unlocking every ounce of renewable energy potential from waste.”

This latest initiative by Thames Water forms part of its on-going waste to energy drive, which has seen it generate on average £15m of electricity a year by burning biomethane from sewage.

Carys Matthews