Electricity generation from pure lactic acid and cottage cheese whey in a Microbial fuel cell using Shewanella Putrefaciens MTCC 8104: Mathematical modelling and Experimental studies

Mathematical models of microbial fuel cells (MFCs), developed so far, often rely on simplified assumptions regarding microbial growth kinetics, substrate utilization, and extracellular electron transfer. Such oversimplifications limit their predictive accuracy and applicability to real waste-derived substrates, which typically contain inhibitory compounds and variable organic compositions. To address these shortcomings, this study presents a comprehensive mathematical model of a mediator-less MFC employing Shewanella putrefaciens MTCC 8104 as suspended culture in anode chamber. The performance of MFCs, run on pure lactic acid and cottage cheese whey, was systematically compared. The model integrates substrate degradation and microbial growth kinetics with electron transfer mechanisms to accurately predict bioelectricity generation. Experimental validation demonstrated strong agreement between model predictions and measured data, with root mean square error (RMSE) and normalized RMSE (NRMSE) values remaining well below 10% for both current and power density, confirming the robustness of the model. Results revealed that the pure lactic acid–fed MFC achieved maximum power and current densities of 1147 mW/m ² and 2.21 A/m ² , respectively. In comparison, the cottage cheese whey–fed MFC exhibited lower values— 287.48 mW/m ² and 0.92 A/m 2 — representing 25.1% and 41.6% reductions, respectively. While performance with whey was lower, its use offers substantial economic and environmental benefits, as it valorizes an abundantly available agro-industrial by-product otherwise treated as waste. This dual advantage highlights the promise of integrating renewable energy recovery with sustainable waste management. The validated mathematical model provides a reliable framework for scaling up MFCs operated with similar substrates.