Performance Optimization of Series-Connected Supercapacitor Microbial Fuel Cells Fed with Molasses-Seawater Anolytes

Microbial fuel cells (MFCs) utilizing livestock wastewater represent a critical path toward sustainable energy and net-zero emissions. To maximize this potential, this study investigates a novel circuit configuration, integrating twin MFCs with dual supercapacitors in a closed-loop system, to enhance charge storage and electricity generation. By utilizing molasses-seawater anolytes, the study establishes a performance benchmark for optimizing energy recovery in future livestock wastewater treatment applications. The self-adjusting potential difference between interconnected MFCs is verified, and supercapacitors significantly improve energy harvesting by reducing load impedance and balancing capacitor plate charges. Voltage gain across supercapacitors exceeds that of single MFC charging, demonstrating the benefits of series integration. Experimental results reveal that catholyte properties—electrical conductivity, salinity, pH, and dissolved oxygen—strongly influence MFC performance. Optimal conditions for a neutralized anolyte (pH 7.12) include dissolved oxygen levels of 5.37–5.68 mg/L and conductivity of 24.3 mS/cm. Under these conditions, supercapacitors charged with sterile diluted seawater catholyte store up to 40% more energy than individual MFCs, attributed to increased output current. While the charge balance mechanism of supercapacitors contributes to storage efficiency, its impact is less pronounced than that of conductivity and oxygen solubility. The interplay between electrochemical activation and charge balancing enhances overall electricity harvesting. These findings provide valuable insights into optimizing MFC-supercapacitor systems for renewable energy applications, particularly in livestock wastewater treatment.