Evaluation of Methyl Red and Lactate as a Mediator and a Simple Carbon Source on Electrochemical Performance of Urmia lake Sediment Microbial Fuel Cell

The energy crisis is an urgent issue due to the increased consumption of fossil fuels. Therefor alternative energy sources are, of critical importance. Sediment Microbial fuel cells (SMFCs) are more important among other renewable energy sources in which chemical energy in organic compounds is converted to electrical energy due to proper bacteria (exoelectrogens) catalytic activity. In this study, one liter glassy reactor was used, half of it was filled with Urmia lake sediment, where microbial consortium are present, as anodic part and upper half was filled with lake water as cathodic part. Copper wires attached to graphite electrodes 4×4 cm² (choice electrode) and via an external resistance 2/2 kΩ two sections related to each other. Electrochemical performance was evaluated by a digital voltimeter. The effectiveness of methyl red as mediator and lactate after determination of optimum concentration which is added every 15 days was evaluated. All fuel cells were studied for over 45 days of experiment. The results demonstrated the mediator SMFC with power density of 7/54 mW/m² has a distinct difference with mediator-less SMFC with power density of 0.46 mW/m². The recorded power density of SMFC with lactate and mediator was 4/44 ± 1/44 mW/m².
Discussion and Sediment microbial consortia degrade available organic compounds and transfer to the anode electrode by using synthetic mediators. The results showed, in addition to external synthetic mediator, methyl red increases fuel cell electrochemical performance. While it was expected that fuel cell performs well in the presence of mediator and external carbon source, we witnessed better electrochemical performance in the absence of lactate.