Evaluation of the performance of a microbial fuel cell with modified graphite electrode for the treatment of wastewater from coffee processing

Abstract

In Costa Rica coffee production is the most traditional agroindustrial activity, each year approximately 69,000 tons of coffee are processed through the technique of wet processing. The process has a high environmental impact since it generates eight liters of wastewater/kg of produced coffee. Consequently, the main goal of this research was to evaluate the electric generation of a Microbial Fuel Cell (MFC) with two chambers, using coffee wastewater as a substrate, which would generate a sustainable solution with an added economic value to this waste in Costa Rica. The MFC with a cathode modified with iron phthalocyanines (FePc) generated a coulombic efficiency of 0.7% and a power density of 89 μW/cm2 in a 5-day operation cycle. In addition, it was determined that the MFC decreases the COD of the waste by up to 27% under native substrate conditions, without the use of high temperatures, or chemical mediators for the anodic reaction and platinum electrodes for the cathode chamber. The efficiency of the device can be improved with changes at design level that reduce the ohmic internal resistance and improve electrical generation, the study confirms the potential of the substrate with a native microorganism suitable for the use of MFC technology, shaping the device as a novelty option for the treatment of the waste in Costa Rica.