For a century, scientists have known that a trickle of electricity could be harvested from the metabolic reactions of bacteria living in soil. To most scientists, it was a parlor trick—a lot of effort to generate a tiny current. Now, a team at Harvard called Lebônê has used the idea to design an inexpensive battery for use in sub-Saharan Africa, where more than 500 million people live without power. The microbial fuel cell, or MFC, can produce enough current to power LED lights and charge cellphone batteries.
In 2008, Lebônê (the word means “light stick” in southern Africa’s Sotho language) field-tested its first prototype in Tanzania, the home country of team member Stephen Lwendo. Simple and cheap, the MFC came in a 5-gallon bucket. It consisted of a graphite-cloth anode, a chicken-wire cathode, manure-rich mud for fuel, a layer of sand to act as an ion barrier and salt water as an electrolyte—all attached to an electronic power-management board. In June 2009, team members traveled to Namibia to launch a pilot program featuring 100 MFCs made from small canvas bags that can be linked for increased voltage. The bags are filled with dirt and buried. When watered to keep the microbes munching, the buried cells can produce power for months. “Rural Africans are used to getting resources out of the ground,” says team member Aviva Presser Aiden, a doctoral student in applied math and genomics at the Broad Institute of MIT and Harvard. “We want to tap that familiarity.”
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