Comparing the performance of microbial fuel cell with mechanical aeration and photosynthetic aeration in the cathode chamber

In this study, the cathode chamber of the microbial fuel cell (MFC) was aerated using the photosynthetic aeration method and was compared with the mechanical aeration method in terms of power generation. Light energy for photosynthetic aeration was supplied in different regimes. The dissolved oxygen of 8.0–9.0 mg/L in the cathode chamber under mechanical aeration was increased to 10.0–11.0 mg/L under photosynthetic aeration of continuous light supply. The maximum power density obtained in the mechanical aeration was increased by 34.5% when photosynthetic aeration employed. Also, the algal assisted cathodic reaction under photosynthetic aeration reduced the internal resistance of the cell by 13.7%. To simulate with natural sun lighting conditions, 12/12 h of dark/light regime was tested to observe the stability of the MFC. During the light phase, microalgae carried out photosynthesis and provided the oxygen required for the cathodic reaction while in the dark phase, the voltage in the cell dropped due to the respiration by microalgae. The dissolved oxygen level dropped to 6.5–7.5 mg/L during the dark phase. Cathode chamber was also operated under 32/32 h of light/dark regime to observe the voltage variation under longer cycles. A higher voltage drop was observed in 32/32 h light/dark regime, as compared with 12/12 h of light/dark regime. Biomass productivity of 0.58 g/L/day was achieved in the MFC conducted under continuous light. It was reduced to 0.51, and 0.39 g/L/day under 12/12 h, and 32/32 h of light/dark regimes, respectively. The results suggested that photosynthetic aeration has the potential to achieve better power generation in the cell than mechanical aeration with an additional advantage of simultaneous microalgal biomass production.