Severn Trent’s £60m Thermal Hydrolysis Plant helps generate even more green power from sewage sludge

Tuesday 29th May

Severn Trent’s new Thermal Hydrolysis Plant (THP) is starting to become operational, with 100 tonnes of sludge being processed on a daily basis.

The £60m scheme changes the way the company treats waste before generating green power and will make the process considerably more efficient, meaning the amount of clean energy generated will increase by almost a third.

More than half of the plant is now up and running, and the company, which serves eight million people across the Midlands and mid-Wales, hopes to see it fully operational by the end of the summer.

The Minworth site already generates enough clean electricity to power the equivalent of 11,000 homes and enough gas to heat 4,800 homes every year and that’s set to increase with THP coming online.

David Nyul, who is leading the project for Severn Trent, explains: “It’s really exciting to see this cutting edge technology starting to become operational.

“This has been a huge investment for us and this innovative tech means that we’ll be generating more green power than ever before at Minworth.  We have significant expertise in anaerobic digestion and THP is the next step to make the process even more efficient in the future.”

The process works by treating sewage sludge, using heat and pressure in a similar way to a pressure cooker – the sludge is heated to 170°C before putting under pressure. This combination of heat and pressure sterilises and shatters the cell structure of the bacteria in the sludge. The treated sludge is then fed into huge digesters which biodegrade the volatile solid matter within the sludge and produce methane rich bio-gas.

Once that part of the process is complete, the sludge is then passed forward to the dewatering process where it is thickened, ready to be recycled as fertiliser for agricultural land.The thermal hydrolysis process has an additional benefit as the leftover solids can be classified as ‘enhanced’ status fertiliser and could potentially be used in the production of crops for human consumption.

David continues: “Minworth is our biggest sewage works and treats waste water from more than 1.6 million homes and businesses across Birmingham and the Black Country. The technology we have already generates both power for use in the works and gas for injection into the national grid.

“The bio-gas we create through this process will both be used to generate electricity and to be treated at our gas to grid plant on site to make it suitable for domestic use before being injected into the grid where it will be used by local homes and businesses.

“The new THP will increase our generation which is good for Severn Trent, for our customers and for the environment.”

By generating renewable energy Severn Trent is able to reduce costs which helps to keep customer bills down – the company currently has the lowest combined average bill in the country.

To find out more about how Severn Trent generates renewable energy visit