| Summary: | Microbial fuel cells (MFCs) have recently attracted more attention in the context of sustainable energy production. They can be considered as a future solution for the treatment of organic wastes and the production of bioelectricity. However, the low output voltage and the low produced electricity limit their applications as energy supply systems. The scaling up of MFCs both by developing bigger reactors with multiple electrodes and by connecting several cells in stacked configurations is a valid solution for improving these performances. In this paper, the scaling up of a single air-cathode microbial fuel cell with an internal volume of 28 mL, has been studied to estimate how its performance can be improved (1523 mW/m<sup>3</sup>, at 0.139 mA). Four stacked configurations and a multi-electrode unit have been designed, developed, and tested. The stacked MFCs consist of 4 reactors (28 mL × 4) that are connected in series, parallel, series/parallel, and parallel/series modes. The multi-electrode unit consists of a bigger reactor (253 mL) with 4 anodes and 4 cathodes. The performance analysis has point ed out that the multi-electrode configuration shows the lowest performances in terms of volumetric power density equal to 471 mW/m<sup>3</sup> at 0.345 mA and volumetric energy density of 624.2 Wh/m<sup>3</sup>. The stacked parallel/series configuration assures both the highest volumetric power density, equal to 2451 mW/m<sup>3</sup> (274.6 µW) at 0.524 mA and the highest volumetric energy density, equal to 2742.0 Wh/m<sup>3</sup>. These results allow affirming that to increase the electric power output of MFCs, the stacked configuration is the optimal strategy from designing point of view.
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