 Microbial fuel cells, MFCs, are devices that can use bacterial metabolism to produce an electrical current from organic substrates. The promise of sustainable energy production from organic wastes has led to increased interest in MFCs. Researchers are uncovering that the greatest value of MFC technology may not be the production of electricity but the ability of electrode-associated microbes to degrade wastes. This article was authored by Kelly P. Nevin and Ashley E. Franks.