Scientific American has a blurb on the activities of some Belgian scientists, who’ve managed to convert bacterial breakdown into something useful:
Millions of tiny microbes infest the water that carries the detritus of human life and society. Some of them steadily break down the organic material in waste streams and produce electrons in the process. By harvesting these electrons, scientists have created microbial fuel cells. New research shows how such biological power plants can be stacked to create usable current.
…The scientists main discovery, however, had to do with the co-evolution of the electrochemical properties of the fuel cell and the actual microbial community. At the start of the experiment, the tiny power plants relied on a diverse community of proteobacteria, including several species of Geobacter and Shewanella, and produced power somewhat inefficiently. But by the end of the experiment–when performance was at its peak–one species, Brevibacillus agri, made up the majority of the electron-producing microbes.
So, another breakthrough: This is a battery that gets better with time, instead of worse.