The potential of whey in driving microbial fuel cells: A dual prospect of energy recovery and remediation

Abstract

Renewable and green energy resources are paramount to environmental sustainability. Microbial fuel cells (MFCs) are potential candidates for these alternatives but there is need to search for cheaper fuels to drive the MFCs for realistic large scale applications. A high strength effluent such as whey, which poses a serious environmental threat, is a good candidate for fueling the MFCs with an added advantage of    bioremediation. Thus, cheese whey was evaluated for its ability to drive MFCs and the extent of whey remediation was also investigated during the operation of MFCs in this study. Three experimental anodic setups: Raw (unamended) whey alone, heat treated (sterile) whey inoculated with Enterobacter cloacae subspecies dissolvens, and raw whey inoculated with E. cloacae where employed. Native whey microbes achieved 44.7 ± 0 .2% total chemical oxygen demand (tCOD) removal efficiency and 0.04% coulombic efficiency (ε_cb). The maximum power density generated was 0.4 W/m² (normalized to the anode surface area). Upon introduction of an exogenous electricigenic E. cloacae culture in the whey, the tCOD removal efficiency dropped to 5% while ε_cb was the highest (3.7%) with maximum power density of 16.7 ± 1.8 W/m². However, a combination of E. cloacae and unsterilized/unamended whey gave 1.1 W/m², ^εcb of 0.5% and 22.1% tCOD removal. The results confirmed the ability of whey to be used as a fuel in the anodic chamber to drive electricity generation in an MFC system with its partial remediation, but absence of synergism between E. cloacae and the electricigens is inherent to whey.

Keywords: Microbial fuel cell, cheese whey, coulombic efficiency, bioremediation, sustainable energy, electricigen