Sustainable bio-energy generation via the conversion of spent wash using dual chamber microbial fuel cell

Abstract

Microbial fuel cells (MFCs) are innovative devices that combine microbial processes with electrochemical reactions to convert organic matter in wastewater into electricity while simultaneously treating the wastewater. One such application is the treatment of spent wash, a highly polluting effluent generated from the distillery industry after crude mesh is separated into ethanol and spent wash. Spent wash, also known as distillery effluent or stillage, is a highly challenging wastewater treatment method due to its high chemical oxygen demand (COD), biological oxygen demand (BOD), and total dissolved solids (TDS). These characteristics make it a complex and polluting industrial effluent that requires specialized treatment processes to reduce its environmental impact effectively. However, MFCs have shown promise in treating spent wash, as they can utilize the organic matter in wastewater as a fuel source for microbial growth as well as for electricity generation. For the treatment of spent wash, Saccharomyces cerevisiae sp. was used as a biocatalyst along with 340 mol/L potassium ferricyanide in the cathode chamber and 170 mol/L methylene blue in the anode as a mediator. All tests were conducted by balancing a one-liter volume for power production from spent wash in MFC with the optimal conditions of 10% agarose, pH 8.5, 300 mL/min of aeration in the cathode chamber, and 40% (in weight) substrate concentration. At an ideal concentration, the maximum current and power density are roughly 53.41 mA/m² and 72.22 mW/m², respectively. For each litre of processed spent wash, a maximum voltage of 850 mV (4.5 mA) was obtained. Amazingly, 91% of COD and BOD were removed from the effluent MFC. These findings show that MFCs are capable of producing electricity and efficiently removing COD from wasted wash at the same time.

Graphical abstract