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.
Willy Verstraete and his colleagues at Ghent University in
Belgium tested the fuel cells in an array of configurations: in
a series, in parallel and individually. Over the course of more
than 200 days, the researchers fed the microbes a diet of
anaerobic and aerobic sludge, as well as hospital and potato
processing factory wastewater. By the end of the experimental
time frame, the short-term power densities--a measure of power
produced per unit of mass--of the fuel cells had tripled. The
team also found that the parallel stack was most efficient at
producing an electric charge, consistently creating stronger
current. The scientists main disc