Microbial fuel cell for bioelectricity generation with optimisation on electrode and biological factors

Abstract

Microbial fuel cell (MFC) is a novel biotechnology which has the potential for energy conversion and waste treatment. Large scale commercial application of MFCs is presently uneconomical due to the low power density. However, past reviews have indicated that there could be significant improvement in microbial fuel cell performance through electrode modifications which would improve the anodic and cathodic electrochemical processes. This study investigated the feasibility of applying organic dyes as fixed mediator with Shewanella oneidensis as biocatalyst in an MFC. Current generation and reaction rates would be proven via chronoamperometry and cyclic voltammetry tests. A control system without mediator added was carried out and the peak current density recorded was 5.2 uA/cm2. Mediator systems which generate higher current than the control system would be deemed to be an effective mediator. Tests were carried out on 5 organic dyes: Methylene Blue, Neutral Red, Toluidine Blue, Methyl Violet and Crystal Violet. Mediators Methylene Blue, Neutral Red and Toluidine Blue generated peak current densities of 17 uA/cm2, 14 uA/cm2 and 10.7 uA/cm2 respectively. Methylene Blue, Neutral Red and Toluidine Blue proved to be effective mediators for MFC in this study. The second aim of this study was to investigate the feasibility of using Acidiphilium cryptum as biocatalyst for Microbial Fuel Cells. The effect of pH on the current output was studied. As A. cryptum is acidophilic, the pH of the discharge medium was varied to attempt to achieve a higher current output. The conditions of the experimental set up were similar to as before, except that S. oneidensis was substituted with A. cryptum as the biocatalyst. Chronoamperometry tests revealed that although A. cryptum is a DMRB, it is not a suitable biocatalyst as the current produced was negligible.