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Severn Trent has invested £15m to build three biomethane plants that will turn the gas produced in the digestion of sewage sludge, energy crops from contaminated land and food waste into a gas that can be injected into the grid.

The equipment and processes are up and running at Strongford Sewage Treatment Works in Stoke and at Stoke Bardolph Sewage Treatment Works in Nottingham, with Spondon Sewage Treatment Works due to become operational when the food waste digestion plant that is currently under construction is completed next year.

Martyn Lightfoot, renewable energy development engineer at Severn Trent, explains:  “This investment is all part of our programme to self-generate the equivalent of half of the energy we use by 2020.

“The biomethane process that takes place at these plants produces a renewable gas that is a fully sustainable resource and can be injected directly into the grid or use in nearby homes and businesses. “These new plants will help us save around £3m a year on our energy bills, and that saving will be passed on to our customers who already pay less than £1 a day for their clean and waste water services.”

Severn Trent, which serves eight million people across the Midlands and into north and mid-Wales, has invested heavily in renewable energy in recent years and is now leveraging this expertise to generate both energy and income.Each plant will produce up to 500m³ an hour of biomethane from 1,000m³ of biogas, which is roughly enough to fill up to eight hot air balloons a day, and will operate 365 days a year and 24 hours a day.

The green gas generated at all three sites would be enough to heat more than 8,000 homes for a year. The gas is made suitable for use in homes, industry or vehicles with a process which involves some complex engineering techniques where the gas is ‘washed’, ‘squashed’ and ‘tested’.

The gas is washed at high pressure, it is then squashed so it is at the same pressure as natural gas and then it is tested for quality and an odour is added so it smells like normal gas.

Once that has been done, it is finally injected into the gas supply network.

Martyn continues: “We’ve been experts in anaerobic digestion for more than 60 years, and creating sustainable and clean energy is now a huge part of our business.

“It’s an area where we’re continuing to develop our knowledge and skills to make sure we continue to operate as a sustainable business long into the future.”

Severn Trent recently revealed it produces the equivalent of 38% of the energy it uses, and is well on its way to meeting its 50% target.

For more information about the company’s approach to renewable energy visit www.stwater.co.uk/renewables