Corporate Responsibility

Sludge as a resource.

Last reviewed:
Sewage sludge is the essential solid by-product of the wastewater treatment process, but it’s a valuable resource too. We treat sludge safely, and recycle it to land sustainably. We recycled 98.7 per cent of biosolids to agricultural land in 2017/18. We also use sludge to generate renewable electricity and reduce our reliance on energy imported from the grid. In 2017/18, we increased our renewable electricity generation from sludge by 11 per cent compared to the previous year.

Sludge cake storage at Long Reach sewage treatment works.

Our sludge strategy.

Our 25-year sludge strategy continues to provide the framework for our sludge investment proposals, which include:

  • Ensuring safe and sustainable recycling – to give confidence to farmers and food producers, but also to reduce our reliance on agricultural land by using other forms of treatment and energy generation.
  • Increasingly adopting treatment processes that will maximise the generation of renewable energy and minimise the volume of sludge produced.

Responsible sludge management.

Producing, treating, recycling, reusing and disposing of sewage sludge is controlled by comprehensive legislation. We maintained 100 per cent compliance with this in 2017/18.

We transport and treat 4.4 billion litres of sewage every day, and last year we produced more than 366,200 dry tonnes of sludge. We treated approximately 93.5 per cent of this sludge using anaerobic digestion or incineration. This allowed us to increase our renewable energy generation by 11 per cent compared to previous years. This also helps to reduce the volume of biosolids (treated sludge) which we take to agricultural land for recycling – an essential part of our strategy to become more sustainable.

We have recently transformed the way we manage sludge by implementing more efficient sludge inventory management and transport logistics between treatment sites. Click on the case study below to find out more: