Tuesday, March 13, 2012

New device Heralds Potential to Turn Sewage Plants Into Power Stations by Damian Carrington

Biodigesters at United Utilities Daveyhulme plant which processes 714m litres of sewage from Manchester each day. Photograph: Ashley Cooper/Corbis

Sewage can be used to generate electricity using a new device revealed by scientists on Thursday. It combines a fuel cell with other technologies to convert waste water treatment stations into power plants, which the researchers believe could provide the power for entire water grids.

"We certainly could take care of the whole water system: the treating and pumping of water, which currently requires substantial amounts of power," said Prof Bruce Logan at Pennsylvania State University in the US. "We also treated the organic matter much faster."

His team's work is published in the journal Science and is "the proof of concept", Logan said. "Our hope now is to optimise the electricity generation as much as possible."

Switching sewage plants from users to generators of electricity would be especially useful in developing countries, said Logan, an environmental engineer specialising in water systems. "There are 2 billion people in the world who need sanitation, including 1 billion who need access to clean water," he said. "If you go into a country and give them a waste treatment system - the World Bank and others have done this - they do not keep it going, as it needs power and maintenance. It is a drain on the community. But if you can also provide electricity for lighting, or charging mobile phones, that's a game-changer."

The new device combines two types of energy-producing technology: a microbial fuel cell, in which bacteria consume organic matter to produce a current, and a reverse electrodialysis system, in which positive and negative ions are separated by a series of membranes, also creating a current. Microbial fuel cells are relatively inefficient while reverse electrodialysis requires many specialised membranes, making it expensive.

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