Synergistic effects between solid potato waste and waste activated sludge for waste-to-power conversion in microbial fuel cells

Environmental pollution and energy shortage are two important concerns that may seriously impair the sustainable development of our society. Microbial fuel cells (MFCs) are attractive technology for the direct conversion of chemical energy of organic wastes into electric power to realize simultaneous electrical power recovery and environmental remediation. In comparison to organic wastewater, solid organic waste is more difficult to be degraded. Food waste as one of the important organic wastes has significant impact on our ecosystem. Here, by taking solid potato waste (SPW) as a typical solid food waste, the impact of waste activated sludge (WAS) as a second waste to introduce synergistic effects between them to enhance waste-to-power conversion in microbial fuel cell (MFC) was systematically investigated. For the MFCs with seven different mixing ratios of SPW and WAS, the MFC with mixing ratio of 6:1 produced the highest maximum current density and maximum power density of 320.1 mA/m² and 14.1 mW/m². Mixing larger ratios of WAS (2:1 and 4:1) resulted in only a very slight increase in coulombic efficiency; while mixing smaller ratios of WAS (6:1, 8:1 and 10:1) significantly increased the coulombic efficiency, and the coulombic efficiency showed an obvious increase as the WAS mixing ratio decreased. Less humic acid- and fulvic acid-like substances were formed from the hydrolysis and degradation of SPW and WAS, and most of dissolved macromolecular organic matters were hydrolyzed into organic fractions with small molecular weight. Principal component analysis indicated that the composition of dissolved organic matters was significantly influenced by different mixing ratios of SPW and WAS throughout the operation. The study provides a promising strategy for enhancing energy recovery from SPW in MFCs.