A microbial fuel cell (MFC) that operates on plant waste has been developed at the Massachusetts Institute of Technology (MIT).
Researchers say the bacteria-powered cell phone charger could keep people in developing countries talking, even when they live far away from the electricity grid.
Recently, the MIT team's prototype won the 5,000 dollars first prize in the MADMEC contest, sponsored by Dow Chemical to encourage new uses of materials that allow alternative or non-traditional sources of energy.
MFCs use electrons released by feeding bacteria on sugars, starches, and other organic material, to produce electricity.
The scientists said MFC had potential in many areas, from sewage plants that are powered by the sludge they are processing, to powering an MP3 player, like Sony's prototype unveiled in August 2007, or even aquatic robots.
The team's BioVolt prototypes run on less-refined fuel than Sony's glucose-gobbling battery; the bacteria instead digest the cellulose in plant waste.
"There's a lot of cellulosic feedstock in rural areas," said MIT scientist Gerardo la O'.
But as MFCs need to be cheaper in order to be competitive in developing countries, the scientists are using a non-platinum catalyst.
"That allows us to lower the cost. Most MFCs use platinum as a catalyst to combine oxygen with electrons and hydrogen ions into water, as part of the electrochemical reaction that produces power," la O' said.
BioVolt is currently patenting its catalyst and is unwilling to divulge what it is made from. But the team has said it is cheap enough for one of the devices to cost only about two dollars in parts.
According to a New Scientist report, currently it would take around six months to charge a phone's battery using a BioVolt. However, they could be connected together, and further refinement of the catalyst and design should increase the power output around 100 fold.