Glycerol conversion and power generation in microbial fuel cells: insect exuviae biochar as electrodes and insect frass as biostimulants
Insects are a suitable raw material for refinement into biodiesel owing to their high fat content, but the refining process produces large amounts of insect waste and glycerol as a byproduct. Biochar electrodes were produced from insect waste for application in microbial fuel cells (MFCs), and experiments were performed to evaluate the electrochemical performance and glycerol conversion efficiency. The biochar was characterized by rich functional groups (O–H, O=C=O, C=C, C=O) and high microporosity, which favored the colonization of microbes. Among the electrode configurations considered, the optimal configuration was a biochar anode and carbon cloth cathode (B-MFC), showing the highest glycerol conversion efficiency (>95%). The B-MFC also exhibited the highest power density (122.3 mA/m3), 1.46-2.34 times that of the other MFCs tested. Adding Nitrogen-rich insect frass to the anode tank further stimulated microbial growth and increased power production, with the highest voltage output of 443.2 mV at 10 mg/L nitrogen concentration, 1.18 times higher than without addition. This study is the first to utilize insect exuviae as biochar electrodes in an MFC to solve the problems of excessive insect waste from biodiesel refinement and converting glycerol into a renewable energy source.
