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Businesses create green gas from human waste

Michelle Ward
5th October 2010
Waste and energy companies are working together to open a plant in Oxfordshire that will be able to convert human waste to biogas, which will then be inserted into the National Grid.
Energy company Centrica, owner of British Gas, is opening a plant at Didcot works sewage in South Oxfordshire, which will be the first in the UK to produce renewable gas from sewage for household use. Waste generated from households and businesses will be used to create biogas that can be used for cooking and heating.

The Didcot facility is a pilot project to demonstrate this new technology and will supply about 200 homes with renewable gas. The project is a joint venture between Thames Water, British Gas and Scotia Gas Networks.

"Feeding this renewable gas directly into the gas grid is the logical next step in our 'energy from waste' business," said Martin Baggs, chief executive of Thames Water.

"What we have jointly achieved at Didcot is a sign of what is to come, which can be replicated across our network and indeed the whole country. Every sewage works in Britain is a potential source of local renewable gas waiting to be put to use."

The process
The facility at Didcot takes waste from the sewage works and produces gas via anaerobic digestion (AD), where bacteria breaks down biodegradable material. The resulting biogas is scrubbed to remove impurities and smell, and propane is added so that it mimics natural gas and can be fed into the gas grid and used in everyday appliances.

The whole process – from flushing a toilet to gas being piped to people's homes – takes around 20 days.

Another AD plant that turns brewery waste and food waste will officially open in Norfolk later this week, while a similar system is already used to create renewable electricity from sewage, where the gas is burned to produce power. This is the first time, however, that biogas from sewage has been pumped directly into the grid for use in homes.

"This is a historic day for the companies involved, for energy from waste technologies, and for progress to increase the amount of renewable energy in the UK," said Chris Huhne, Energy and Climate Change Secretary.

Future of biogas
A study by the National Grid believes that at least 15 per cent of all gas consumed could be made from sewage slurry, old sandwiches and other food thrown away by supermarkets, as well as organic waste created by businesses such as breweries.

The project took six months to complete and cost £2.5 million, and this is only the beginning of more efforts to utilise waste.

"This renewable gas project is a real milestone in Britain's energy history, and will help customers and the environment alike," said Gearoid Lane, managing director of communities and new energy at British Gas. "Renewable gas has the potential to make a significant contribution to meeting the UK's energy needs."

Government role
Government's spending cuts could make it more difficult for companies to come up with the £10 billion needed to develop the new plants and pipelines for this new technology, however. Since it is more expensive to produce renewable gas, companies say they need to be paid twice the market rate for it to make economic sense.

Under the proposed Renewable Heat Incentive (RHI), which is still awaiting Government approval, subsidies would be paid for renewable gas being put into the grid. This would make it feasible for waste companies.

"The Didcot project will prove the technology works, but it is essential that the anticipated financial support follows," said Gaynor Hartnell, chief executive of the Renewable Energy Association. "It was developed in expectation that the RHI will be introduced next year, and we’re waiting for confirmation of this following the Comprehensive Spending Review on October 20."

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Businesses create green gas from human waste
Didcot sewage works in Oxfordshire is now producing biomethane from human waste for injection into the gas grid
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