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Managing sewage sludge

Sewage sludge, being mainly an energy-rich organic material, is a valuable by-product of the wastewater treatment process.

We treat sludge to a high standard with the vast majority treated through anaerobic digestion. This generates a high-methane content biogas that can be used as fuel in our combined heat and power (CHP) engines. This generates renewable energy that is then used to run our largest sites.

How we use sewage sludge

Some of our sludge is used in incineration with energy recovery at our Beckton and Crossness treatment works in London. We put 100% of our sludge to beneficial re-use, mainly through recycling to agriculture as a nutrient-rich fertiliser or for use in land restoration projects as a bulk soil improver. Where we can, we also recycle the resulting ash from our incineration process.

The recycling of treated sewage sludge (known as ‘biosolids’) to agriculture is carried out under strict regulations by which we've consistently maintained our 100% compliance.

This includes the ‘Safe Sludge Matrix’, an agreement between water companies and the British Retail Consortium. The agreement sets out standards for the application of biosolids to crops and strict controls on the quality.

We must ensure we continue to manage sewage sludge in a safe, sustainable and beneficial way. To achieve this, we're continuing to implement a strategy that makes the best use of our sludge. This strategy considers issues of acceptability, energy, transport, odour, nutrients, local constraints and innovative uses in the future.

Photograph of a large truck in a field