Sustainability Bioethanol Production From Agricultural Waste With Valorisation Of Fermentation Residues In Microbial Fuel Cells

Bioethanol is a renewable fuel produced from the fermentation of sugars and starches in plant-based biomass. However, large-scale production generates considerable wastes, which, if untreated, may cause environmental concerns. These by-products can instead serve as substrates for microbes in microbial fuel cells (MFCs), bioelectrochemical systems that generate electricity through microbial metabolism. This study aims to reduce environmental pollution by developing a hybrid system that integrates two processes: (i) bioethanol production from agricultural residues and (ii) MFC operation utilizing the resulting wastes. Rice straw was selected as feedstock. Pleurotus ostreatus (oyster mushroom) degraded the lignocellulosic structure to release fermentable sugars, which were fermented by Saccharomyces cerevisiae (yeast) into bioethanol and CO₂. The ethanol was distilled, while byproducts (thin stillage, yeast autolysate) were supplied to the MFC. In the anode chamber (anaerobic), Shewanella oneidensis. consumed the wastes and generated electrons which facilitated electrical generation, while protons diffused through a proton exchange membrane. In the cathode chamber (aerobic), Bacillus subtilis facilitated the reduction reaction. Electrical output was measured using a multimeter across the anode and cathode, followed by load application with known resistors. The hybrid system produced bioethanol with a yield of ~0.22 g g⁻¹ dry rice straw
and generated an open circuit voltage of ~0.60 V and current output of 0.6 mA (power density ~36 mW m⁻²). These results demonstrate the feasibility of coupling bioethanol production with MFCs, providing dual benefits: renewable fuel generation and sustainable electricity recovery. This approach reduces agricultural waste, promotes waste-toenergy conversion, and contributes to lowering environmental pollution.