Stack Development and Power Generation Efficiency Analysis of 3D-Printed Plant Microbial Fuel Cells Growing Mung Beans (Vigna Radiata)

Plant microbial fuel cell (PMFC), a green energy source, is a bioelectrochemical system that converts rhizodeposits to bioelectricity. This paper investigated the stacking efficiency of PMFCs with USB connectivity using 3D-printed conductive PLA electrodes with Vigna radiata as the model plant. The stacking techniques successfully connected 16 PMFCs in pure and varying combinations of series and parallel. Stacking all cells in pure parallel obtained a maximum voltage of 98.4 mV. However, due to voltage reversal, cumulative stacking of PMFCs in pure series or parallel is inefficient and not an ideal strategy for scale-up. Further evaluation of the overall performance was done by stacking the cells in series-parallel and parallel-series configurations. The results revealed that stacking 6 (3P-S), 8 (4P-S), and 12 (4P-2S) cells in parallel-series correspondingly amplified the power and power densities of the system. Essentially, it was reported that stacking two sets of two parallel cells in series (2P-S) collected the highest power and power density of 0.42 µW and 13.76 µW/m
²
, respectively. Despite optimizing the power and power density, PMFC still faces a challenge in retaining the power and power density while connecting stacked cells. The scale-up potential of this system, the optimal power density of PMFCs could be improved by design optimization of electrodes and further analysis of the factors influencing the power generation capacity of this environmentally benign technology.