Electricity generation from sweet potato-shochu waste using microbial fuel cells

Electricity generation and treatment of sweet potato-shochu waste, acidic and organic-rich slurry, was examined using cassette-electrode microbial fuel cells (CE-MFCs). Among CE-MFCs with raw (73 g-chemical oxygen demand chromium COD_Cr/L) and different concentration of diluted sweet potato-shochu waste (0.5, 1, 5, 10, and 20 g-COD_Cr/L) without pH control, the maximum power density (1.2 W/m³) and COD_Cr removal efficiency (67.4 ± 1.8%) were observed in the CE-MFCs with 10 g-COD_Cr/L shochu waste. The concentration of organic acid was decreased to below the quantification limits during the 9-day operation in the CE-MFC with 10 g-COD_Cr/L shochu waste. During the same period, the electrolyte pH was increased from 4.2 to 6.6. Microbial community analysis revealed that the genus Clostridium (75.4%) was predominant in the CE-MFCs with raw shochu waste, whereas Bacteroides (65.3%) and Clostridium (12.1%) were predominant in the CE-MFCs with 10 g-CODCr/L shochu waste.