Existence of sodium bicarbonate enhanced bioelectricity generation on Chlorella sp. biofilm in a Biophotovoltaic (BPV) system

Sodium bicarbonate (NaHCO 3 ) is a low-cost inorganic carbon source, highly soluble in water and widely used in microalgae research. Using carbon dioxide (CO 2 ) gas in microalgae culture is ideal for algae growth. However, the usage of CO 2 is restricted due to the high cost of CO 2 capture and transportation. In this work, the performance of non-axenic Chlorella sp. (UKM2) biofilms on fluorine doped tin oxide (FTO) glass anodes with varying NaHCO 3 concentrations in the biophotovoltaic (BPV) systems is measured and discussed. The highest power density and photosynthetic pigments were obtained when employing 1 g L −1 NaHCO 3 in the system. The presence of NaHCO 3 increased the photosynthetic pigments e.g., chlorophyll-a and improved the performance of the BPV system. The power output increased by 52% from day 6 (0.023 ± 0.005 mW m −2 ) to day 12 (0.035 ± 0.003 mW m −2 ). After 12 days of operation, the power output of 0.035 ± 0.003 mW m −2 was generated, and the system still operated even after 50 days. For the long-term performance of BPV device, the highest power output of 0.042 ± 0.003 mW m −2 was obtained for the 1 g L −1 NaHCO 3 system which corresponds to 83% increment from day 6 to day 55. However, an excessive amount of NaHCO 3 concentration deteriorated the performance due to the reduction of chlorophyll- a concentration.