Nutrient Recovery from Food Waste–Derived Anaerobic Digestate Using Dual-Chamber Microbial Fuel Cell: A Technoeconomic Assessment

Abstract Anaerobic digestate obtained from a digester operated on food waste was further treated in a dual-chamber microbial fuel cell (D-MFC) for nutrient recovery. Digestate was fed to the D-MFC at different dilutions [chemical oxygen demand (COD): 1,000–5,000 mg/L] in fed-batch mode and at different organic loading rates (OLRs) (0.85–1.70 kg/m 3 /day) in continuous mode. Peak power densities of 2.02 and 1.72 W/m 3 were achieved at a COD concentration of 3,000 mg/L and OLR of 1.35 kg/m 3 /day, respectively, due to strengthened metabolic activity of exoelectrogens. However, at an excessively high OLR, reactor performance declined due to variation in the microbial community structure, facilitating the dominance of non-exoelectrogens over exoelectrogenic microorganisms. Based on D-MFC operation over 80 days, the average COD and ammonia ( NH 4 + - N ) removal efficiencies were 96 ± 1 percent and 62 ± 3 percent, respectively, while phosphorus release increased the average PO 4 3 − - P concentrations to 33 mg/L in anode effluent. Further, struvite precipitation led to NH 4 + - N and PO 4 3 − - P recovery of 87 percent and 94 percent, respectively, thus yielding 3.17 kg struvite/m 3 of treated digestate. Technoeconomic analysis for a 2,000 L D-MFC indicated a payback period of six years for the initial capital expenditure based on revenue generation from recovered nutrients and wastewater treatment. Overall, the long-term operational stability and enhanced nutrient recovery prove this approach to be a promising solution for AD effluent management on a large scale.