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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