Microbial fuel cells, which use electrodes in dirt to power a small motor, have long been more or less a laboratory curiosity. Because they generate such a small amount of power, developing them to charge devices would not be practical in places where electricity is readily available. However, Lebônê Solutions, a startup based in Cambridge, MA, aims to use microbial fuel cells to provide power to Africans who are off the grid. In some parts of Africa, a small amount of energy is enough for a few hours of lamp light in the evening, or for powering the ubiquitous cell phones--something that some residents will walk five hours to a generator to do, says Aviva Presser, a cofounder of Lebônê. The company is made up largely of Harvard University alumni and current Harvard students originally from African countries.

With funding from the Harvard Institute for Global Health, the team has recently completed a pilot study in Tanzania, where members brought six basic microbial fuel cells and taught residents how to use them. The team organized village meetings where team member and Tanzanian native Stephen Lwendo explained how to make the fuel cells.

The team found residents receptive to the idea of easy-to-grow power and keen to use the fuel cells to charge cell phones, run radios, and provide more light. "In Africa, people want to power [small] DC devices," as opposed to large AC devices like a refrigerator, says Lebônê cofounder Hugo Van Vuuren, a Harvard graduate and a South African native. The team hopes to develop the technology to make it competitive with other renewable energies in countries across Africa. Microbial fuel cells could have a distinct advantage because they are initially cheaper to build than a windmill and easier to set up than solar panels. What's more, they could last up to 10 years, says Lebônê cofounder David Sengeh.

Instead of using hydrogen as a fuel, as do conventional fuel cells, microbial fuel cells use naturally occurring microbes to generate power. Bacteria live in the anode, where they eat glucose, sewage, or other waste water, and turn that into electrons and protons. The bacteria transfer electrons to the circuit, which provides small amounts of power.