A water has injected the largest quantity of green gas produced from around 2.5 million people’s ‘processed poo’ into gas pipes serving homes in the Birmingham area. This is thanks to an innovative treatment process, the green gas becomes just as clean and exactly the same as ‘normal gas’ and, every year, it will save around £1.7 million on the company’s gas bill for the benefit of its customers.
So how is it all done and why is Severn Trent Water the first UK water company to do it on such a large scale. The company’s renewable energy development manager, Simon Farris, explains: “Minworth is our largest sewage treatment works; we treat sewage from around 2.5 million people in the wider Birmingham area. Although it’s a little unsavoury, there’s lots and lots of power locked in poo, and when that’s processed it’s perfect to generate clean renewable green gas.
“As part of the sewage treatment process, sewage sludge is produced. At Minworth we feed this to our 16 anaerobic digesters, or ‘concrete cows’, which work like giant cow’s stomachs to digest the waste material to produce energy in the form of gas. Currently, we use 40 per cent of this energy to make electricity, but more can be done – that’s where this new process comes in. With treatment, gas from sewage is made clean enough and at the right consistency to be injected into the gas supply network to power homes in the area. It’s local gas produced from local people!”
Washed, squashed, tested and injected – it’s simple really
Simon continues: “The gas is made suitable for use in homes with a simple process which involves some complex engineering techniques. The gas is ‘washed’ at high pressure, it is then ‘squashed’ or compressed 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’s finally ‘injected’ into the gas supply network. Before it is injected, we have the opportunity to stop the process, so we can be 100 per cent certain it is perfect.
“We generate renewable energy from a number of different sources to help keep costs down for our customers and protect the planet. Innovations like this will help us to generate around 30 per cent of the energy we need to power our sewage and water treatment works from renewable sources by 2015.”