A Critical View of Microbial Fuel Cells: What Is the Next Stage?

Microbial fuel cells (MFCs) have garnered interest from the scientific community since the beginning of this century and this has caused a considerable increase in the scientific production of MFCs. However, the ability of MFCs to generate power has not increased considerably within this timeframe. In recent years, the power generated by MFCs has remained at an almost contact level owing to difficulties in the scale-up of the technology and thus the application of MFCs for powering systems with high energy demands will not be fully developed, at least within a short temporal horizon. Scale-up by increasing the size of the electrodes has failed, because of the wrong assumption that a linear function describes the relationship between the amount of power generated by a MFC and its size. However, more efficient energy generation upon working with small MFCs has been described. This has led to a new approach for scaling up on the basis of miniaturization and replication. Then, MFCs can be connected electrically in series to increase the overall potential and in parallel to increase the overall current. However, cell-voltage reversal and ionic short-circuit issues must be solved for this approach to be successful. Nowadays, the applicability of MFC technology in wastewater treatment does not make any sense in light of the power levels reached, despite the fact that MFCs were seen as a paramount opportunity less than a decade ago. However, MFCs can be used for wastewater treatment with coupled energy generation, as well as for other technologies such as biosensors and biologically inspired robots.