Microbial fuel cells (MFC) are cells that can generate electricity from organic matter or organic wastes.
A Geobacteria species oxidize organic waste and the by product electrons is transferred to the electrode.
It is similar to conventional fuel cells. But are electrochemical devices which undergo chemical reaction to power electronic devices.
Lot of R&D is going on to improve the efficiency of such cells. Since their output voltage generated is very low .
A type of MFC is the Benthic Unattended Generator also known as BUG.