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Slough plant turns sewage into new renewable fuel

Thames Water has begun drying sludge at Slough Sewage Works in Berkshire to produce a new renewable fuel that burns like wood chip.

Thames Water said the £1.5M sewage sludge dryer at Slough will reduce its carbon emissions by more than 500t annually and bring up to £300,000 a year of operational cost benefits. The cost saving comes from reducing use of non-renewable gas from the grid, additional government Rewewable Obligation Certificate (ROC) feed-ins and reducing the volumes of leftover sludge that need to be trucked to spread on agricultural land as fertiliser.

Some 20% of the solids left over from the treatment process at the Slough works — about 5t a day of sludge — are being put through the new dryer. The resulting “sludge flakes” are then transported to Crossness sewage works in Bexley, east London, where they are fed into a sludge-powered generator to generate renewable electricity.

Using more sludge flakes — which are 95% dry and thus more readily combustible than more traditional sludge cake which is only 25% dry — will reduce the generator’s reliance on non-renewable gas from the grid to keep the fire going in the machine.

Readers' comments (2)

  • David Smith

    How long has it been operational?

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  • This article does not explain where the energy comes from to dry the sludge. Is it fair to presume that the transport of flakes is more sustainable than cake? What will the effect be on traditional sludge cake clients? Globally is there a net gain?

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