Resources recovery in the dairy industry: bioelectricity production using a continuous microbial fuel cell

The increasing food demand and the exhaustion of non-renewable fuels provide new market opportunities in the agro-farming sector. Biological systems designed to add value to useless organic sub-products and to generate off-grid electricity may be one of the most interesting outcomes. Therefore, the capacity of some microorganisms to transfer electrons generated during organic carbon oxidation directly to an anode in a so-called microbial fuel cell (MFC) might be an asset in a sustainable management context. In this regard, the main goal of the present work was to evaluate the performance of a continuous MFC applied in a dairy industry. A maximum voltage of 576 mV was produced during continuous operation, corresponding to a power density of 92.2 mW m−2 or 1.9 W m−3. MFC was able to remove 1298 ± 617 mg L−1 of chemical oxygen demand (COD) at a hydraulic retention time of 8.4 h, and the maximum COD removal (63 ± 5%) was achieved after 20 days of continuous operation. In addition, the coulombic efficiency average was around 10.5 ± 10% with a maximum of 24.2 ± 1.5%. In average, the MFC was able to extract a specific energy of 8.95 × 10−2 kW h kg−1 COD with a maximum output of 20.53 × 10−2 kW h kg−1 COD. In conclusion, the MFC technology is a valuable option for simultaneous wastewater treatment and energy recovery and deserves to be tested and scaled-up in the dairy industry.