Metal Foam Electrodes and Ligno-Cellulosic Waste in Microbial Fuel Cell Setup

Optimization of electrode structure and materials is a subject taken into high consideration to improve the performance of microbial fuel cell (MFC) systems. In this work we show the use of novel electrodes made of metal alloys with a peculiar foam structure. The foam structure of the electrodes, realized according to a proprietary process [1], is intended to increase the electrode surface available to the microorganisms for the formation of the biofilm. The use of cast iron (GS800) and stainless steel (304) foams as electrodes in MFC run with Shewanella oneidensis has shown a 5-fold increase of current density at the anode, compared to the use of massive electrodes made of the same materials. Also MFC systems with cast iron foam electrodes resulted in better performance, compared to massive ones, but heavy corrosion phenomena caused by microbial metabolism were clearly visible at the anode and also drastic modifications occurred on the cathode surface. Concomitant to the study on the advantages given by the use of foam structured electrodes over massive ones, we isolated from waste water samples bacterial strains able to grow in the presence of the so called “fermentation inhibitors”. These compounds, which are of very diverse chemical nature, are released during the treatment of ligno-cellulosic material that is necessary to make such material fermentable by yeast for the production of ethanol as second generation biofuel. MFC were run in the presence fermentation inhibitors in order to determine whether they could be removed through the metabolic activity of bacteria. Removal of fermentation inhibitors through MFC technology would allow efficient coupling of MFC technology and bioethanol production by making ligno-cellulosic material less toxic for yeast and therefore improving ethanol yields. Consequently, MFC technology could get an important role in biorefinery concepts.