Development of a procedure to rapidly acclimate a microbial fuel cell (MFC) for electricity production

Various techniques to enrich electrochemically active bacteria on an electrode using acetate as a substrate were studied. The first method was to use sludge and a carbon electrode and this resulted in power generation at a level of 10 mw/min within 50 hr. A second method was to first enrich the sludge with iron reducing bacteria in batch culture, but power densities were low unless the reactor was inoculated with L-cysteine to scavenge oxygen. A third method was to coat the electrode with iron oxide and add sludge. In this case, the maximum power density was three times higher than that using only the carbon electrode (0.04 mM acetate solution) after enrichment. A fourth method was to apply a "paste" bacteria from a reactor producing electricity, forming an immediate biofilm on the electrode surface. This did not affect the acclimation time but did increase power density to 40 mw/sq m. A fifth method was to introduce a second electrode on separate circuit. The acclimation time and total power output of the microbial fuel cell were not affected using a second electrode, but this method was successful at enriching on the new electrode only bacteria growing in the reactor. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).