The biomethane project that turns human waste into green gas that we featured in May has now gone live. The project is now converting the treated sewage of 14 million Thames Water customers into clean, green gas and is pumping that gas into people's homes.
The new biogas plant – sited next to the Didcot sewage works in Oxfordshire – has been officially opened by Energy and Climate Change Secretary Chris Huhne, who said: "It's not every day that a Secretary of State can announce that, for the first time ever in the UK, people can cook and heat their homes with gas generated from sewage. This is an historic day for the companies involved, for energy from waste technologies, and for progress to increase the amount of renewable energy in the UK."
Hoped to be the first of many such installations, the process starts when one of Thames Water's 14 million customers flushes the loo. The waste makes its way to the Didcot sewage works to begin its treatment and/or recycling. The solids, or sludge, go on to be warmed up in huge vats so that bacteria can break down any biodegradable material in a process known as anaerobic digestion.
The end result of this process is biogas, which is further cleaned up before being fed into the gas grid. It takes around 20 days from flush to finish for the process to complete and will produce enough renewable gas to up to supply 200 homes.
The average person is said to produce about 30kg/66lbs (dry weight) of sludge every year. This means that if all the 9,600 waste treatment facilities in the UK similarly processed sewage from the whole population, it could meet the annual gas demand of over 200,000 homes. A study by the national grid has indicated that up to 15 per cent of domestic gas needs could be met by biomethane as soon as the year 2020.
Martin Baggs of Thames Water said: "We already produce GBP15 million [US$23.8 million] a year of electricity by burning biogas from the 2.8 billion liters [739.7 million US gallons] a day of sewage produced by our 14 million customers. Feeding this renewable gas directly into the gas grid is the logical next step in our ‘energy from waste' business. What we have jointly achieved at Didcot is a sign of what is to come."
The joint venture between Thames Water, British Gas and Scotia Gas Networks is seen as an important move towards low carbon gas production in the UK. According to Gearóid Lane of British Gas, the project "is just one part of a bigger project, which will see us using brewery and food waste and farm slurry to generate gas to heat our British Gas homes."
The biogas project took six months to complete at a cost of GBP2.5 million (US$3.9 million).