A team from Penn State University and the company Ion Power (Delaware) has developed a microbial fuel cell (MFC) that both breaks down organic matter and produces hydrogen.
Conventional MFCs (developed to offset wastewater treatment costs) generate electricity from the oxidation-reduction reactions involved in the processes of degradation of organic waste by bacteria.
The new device, called BEAMR for BioElectrochemically-Assisted Microbial Reactor, is based on the use of hydrogen produced by bacterial fermentation. Under normal conditions, this process converts carbohydrate compounds into a limited amount of hydrogen and acetic acid-like residues. By applying a very low voltage (around 250 mV) to an anaerobic MFC, Bruce Logan and his colleagues have however succeeded in increasing the electrochemical potential of bacteria and therefore their ability to break down molecules by-products of fermentation. They were thus able to recover in the form of gaseous hydrogen more than 90% of the protons and electrons resulting from the oxidation of acetate by bacteria. The hydrogen released is itself the fuel for a cell which produces the applied voltage. This simple stimulation makes it possible to extract four times more hydrogen from biomass than fermentation alone.
In theory, the principle experimented by researchers is not limited to carbohydrate compounds; it could be effective
with any soluble biodegradable organic material.
NYT 25 / 04 / 05 (Fuel cell sweaters hydrogen out of bacteria) source.