Manure to fill gas grid

LONDON (Reuters) - Manchester's toilets will soon be contributing to the local gas network under a green energy project planned by United Utilities Group Plc and National Grid Plc.

In a UK first, the two companies plan to turn a by-product of the wastewater treatment plant at Davyhulme in Manchester, northwest England into gas for the local network and fuel for a fleet of sludge tankers.

The Mancunian biogas will be upgraded to remove carbon dioxide and trace elements, leaving biomethane which will be conditioned with propane and odorants before being pumped into the network and back into their homes.

"Biomethane is a fuel for the future," Janine Freeman, head of National Grid's Sustainable Gas Group said. "Not only are we reusing a waste product, but biomethane is a renewable fuel, so we helping to meet the country's target of 15 percent of all our energy coming from renewable sources by 2020."

Biogas is produced through a process called "anaerobic digestion" when wastewater sludge is broken down by the action of microbes.

The 4.3 million pound ($7.10 million) project should be operational by early 2011 and supply enough gas for about 500 homes. The overall potential of biomethane from a plant like Davyhulme would be to supply about 5,000 homes, National Grid said.

Unlike electricity generated from wind turbines, biogas offers a steady stream of green energy.

"Sewage treatment is a 24-hour process so there is an endless supply of biogas," Caroline Ashton, United Utilities biofuels manager, said.

"It is a very valuable resource and it's completely renewable. By harnessing this free energy we can reduce our fuel bills and reduce our carbon footprint."

One of United Utilities' sludge tankers has already been converted to run on the gas and the company expects to save hundreds of thousands of pounds a year in fuel costs with the 24 tankers it aims to convert initially.

It was not clear whether Manchester's home-made gas suppliers will get a discount on their own bills for their efforts.

(Reporting by Daniel Fineren)