Thousands of UK residents will soon be cooking with "poo-power"'. In a national first, water firms including Severn Trent, Wessex Water and Northumbrian Water are preparing to pipe a continuous supply of biomethane gas directly from sewage-treatment plants into the National Grid.
"Our customers could be at home frying sausages on gas generated at our sewage treatment works," said Mohammed Saddiq, general manager of GENeco, Wessex Water's energy company.
In the past, water firms have used gas produced in sewage treatment to generate electricity on site, but this will be the first time advanced technology to treat methane will produce high-quality biomethane suitable for use in homes.
Dragan Savic, a Professor of Hydroinformatics at Exeter University, said that given the UK had more than 9,000 sewage treatment works, "poo-power" could hold substantial environmental benefits.
"Greenhouse-gas emissions reductions could be significant as the methane normally generated at sewage works is 25 times more harmful to the atmosphere than carbon dioxide," he said. "By capturing methane and pumping it into the National Grid water companies could turn from greenhouse-gas emitters into renewable-energy generators."
According to the latest data from the Environment Agency, the UK water industry, per year, consumes around 8,100 gigawatt hours (GWh) and generates over 4 million tons of greenhouse-gas emissions.
Some English water firms, including Anglian Water, South West Water, Yorkshire Water, and Southern Water, already have Combined Heat and Power plants where gas produced in water treatment is burnt to produce electricity, which is used to power the plant. In some cases excess is sold on to the Grid. Welsh Water and Scottish Water also generate renewable energy in this way.
"Although it's a little unsavoury, there's lots and lots of power locked in poo, and when processed it's perfect to generate clean renewable green gas", said Severn Trent Water's Simon Farris."It's also important for lowering our energy costs... so that we can pass those on to customers."
Mr Farris predicts, over the next 20 years, Severn Trent's gas-to-grid scheme could cut its carbon emissions by 300,000 tons – the weight of more than 50,000 adult African elephants. The volume of biomethane produced will also be greater than the firm's gas needs, allowing it to be classified "self-sustainable".
Severn Trent was first to activate its gas-to-grid systems, this week, injecting 1,200m3 of biomethane into the Grid from Minworth sewage works in Birmingham. When fully operational, it will inject 750m3 of biomethane into the Grid every hour, enough to fuel 4,200 homes annually. Both Severn Trent and Wessex Water intend to pipe a continuous supply into the Grid by mid-October.
Wessex Water's gas-to-grid project at the Bristol sewage works will be the first and largest plant of its kind, using food waste as well as sewage to produce up to 2,000m3 of biomethane an hour, enough to fuel 8,300 homes for a year. Food waste, said spokesman Ian Drury, generates "twice as much" biogas as sewage.
Northumbrian Water plans to implement its gas-to-grid scheme at Howdon in Tyneside later this year and aims to pipe more than 1,000m3 of biomethane to the Grid per hour.
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