Effects of architectural changes and inoculum type on internal resistance of a microbial fuel cell designed for the treatment of leachates from the dark hydrogenogenic fermentation of organic solid wastes

A new design of a single chamber MFC-A based on extended electrod surface (larger sigma, specific surface or surface area of electrode to cell volume) and the assemblage or 'sand-wich' arrangement of the anode-proton exchange membrane-cathode (AMC arrangement) and a standard single chamber MFC-B with separated electrodes were tested with several inocula (sulphate-reducing, SR-In; methanogenic, M-In, and aerobic, Ab-In) in order to determine the effects on the internal resistance R-int and other electrical characteristics of the cells. In general, the R-int of the new design cell MFC-A was consistently lower than that of the standard MFC-B, for all inocula used in this work. Resistance followed the order R-int,R-SR-In < R-int,R-M-In << R-int,R-Ab-In. These results were consistent with reports on reducting of ohmic resistance of cells by decreasing inter-electrode distance. Also, the volumetric power P-v output was higher for the MFC-A than for MFC-B; this was congruent with doubling the sigma in the MFC-A compared to MFC-B. Yet, power density P-An delivered was higher for MFC-A only when operated with SR-In and Ab-In, but not with M-In. The MFC-A loaded with SR-In showed a substantial improvement in Pv (ca. 13-fold, probably due to the combined effects of increased sigma and decreased of R-int) and a 6.4-fold jump in P-An compared to MFC-B. The improvement was higher than the expected improvement factors (or algebraic factores; 6.5 improvement expected for Pv due to combined effects of increase of sigma and lowering the R-int; 3.25 improvement expected for P-An due to lowering the R-int). Our results point out to continuing work using the two-set, sandwith-electrode MFC and sulphate-reducing inoculum as a departing model for further studies on effects of inoculum enrichment and electrode material substitution on cell performance. Also, the MFC-A model seems to hold promise for future studies of bioelectricity generation and pollution abatement processing leachates produced during biohydrogen generation in dark fermentation processes of organic solid wastes. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.