Performance evaluation of different electrode materials and substrate modifications on bioelectricity generation from bacteria fuel cells

Abstract

The global energy crisis is caused by high energy demand and insufficient resources. Non-renewable energy sources are diminishing, while renewable energy sources are underutilized. An urgent search for alternative energy generation routes is necessary. A microbial fuel cell is a process that makes use of microorganisms like bacteria or fungi as biocatalysts that oxidize waste organic matter to release electrons which in turn are used to produce electricity. An MFC reactor is made of a cathode, an anode, and a substrate onto which microorganisms are fed so that electrons are released for bioelectricity generation. A two-chamber cathode was fabricated in this study. The chamber has a total volume of 120ml and a working volume of 100ml. The chamber was used to investigate the influence of substrate enrichment and type of electrode on electricity production by some selected bacteria (Pseudomonas Tawanensis (PT), Myroides Odoratimimus (MO), Sphingobacterium Mizutaii (SM). The substrate used is locust beans wastewater. The substrate was enriched with either sucrose or acetate. The electrodes include copper, aluminum, aluminum-zinc alloy, soft zinc, and zinc. To determine the most suitable enrichment sources (sucrose and acetate) a mixed culture of the three bacteria was inoculated in the substrate (locust bean wastewater) with a standard graphite electrode. Cellulose acetate was used as the membrane for the chamber in place of the cation exchange membrane. The setup was operated for 20 days. The effect of substrate enrichment and electrode use on bioelectricity and stability was later analyzed. The results from the mixed culture showed that the substrate enriched with sucrose generated a higher voltage (2.15x10^-3 mA) when compared with an acetate-enriched substrate (this generated a voltage of 1.62x10^-3 mA) with graphite as the electrode. Following this result, we selected sucrose as the enrichment source in the remaining experiment. Each bacterium used in this study generated electricity in the chamber containing sucrose-enriched substrate with each of the electrodes used. This implies that all the adopted electrodes are sufficient site for the formation of biofilm through which bioelectricity can be generated. However, the highest voltage (1.72mA) was recorded in the chamber containing Pseudomonas taiwanensis with zinc as the electrode in the chamber. We noted that in all the bacteria used in this study, bioeletricity generation was more stable and consistent with copper as the electrode of choice.