Severn Trent goes self-sufficient in renewable gas

An example of Malmberg’s double container COMPACT plant, which is used in the upgrading of biogas to biomethane through the ‘water washing process’.

Work will soon start on the largest fully commercial gas-to-grid plant to be built in the UK to date, which will purify sewage gas on behalf of Severn Trent Water.

When completed, it will process up to 1500m3 per hour of renewable biogas to a state at which it can be safely injected into the national gas grid and make the water company self-sufficient in gas.

Imtech Waste, Water and Energy (Imtech) has been awarded the contract, worth an estimated £6.4 million, by Severn Trent Water to construct the Minworth Gas-to-Grid plant. The project will run for 60 weeks.

This project has only been made financially viable following the recent introduction of the Government’s Renewable Heat Incentive scheme.

Its award has resulted in job creation at Imtech, with a number of new team members employed specifically for this high profile project, including project management, QS and engineering positions, as well as several general site staff jobs.

Commented Nick Small, operations manager at Imtech: “We are extremely pleased to have been awarded such a high profile contract, which represents a significant step change for the waste industry in the UK.

"Severn Trent is already the UK’s largest producer of electricity from sewage gas producing 192GWh in 2012/13, and with the help of Imtech this will enable Severn Trent to become totally self sufficient in gas demand."

The project represents another key milestone in the development of the Waste and Energy business at Imtech, after it recently began work on a prestigious contract to develop the Wakefield AD biogas plant with Shanks Waste Management. This is part of a wider agreed plan to reduce the landfill diversion rate of Wakefield district waste by 90%.

The production of grid-quality biogas from sewage is not without technical problems, but a partial solution to these has been found at Cranfield University, which, earlier this month, received an award for its research in this area.

The research was recognised by the Worshipful Company of Engineers for excellence in engineering that benefits the environment.

It was awarded for looking at the most effective methods for removing chemicals called siloxanes from the process. Siloxanes end up in sewage because they are widely used to soften, smooth, and moisten, in products such as shampoos and moisturisers.

But they do not decompose in the sewage system, and so find their way into the waste matter that remains following the sewage treatment process. They then turn into silicon dioxide, or sand, during the process of burning this waste for biogas and ‘green energy’, which can block engines and cause costly damage.

PhD student Caroline Hepburn, whose research is funded by Severn Trent Water, was presented with the Hawley Award and a cheque for £5,000 at the Worshipful Company of Engineers’ Annual Awards Dinner, on 9 July by Sir George Cox, Board Member of NYSE-Euronext and Director of Shorts, the aerospace company.

Pic from Imtech

An example of Malmberg’s double container COMPACT plant, which is used in the upgrading of biogas to biomethane through the ‘water washing process’.