Scalability of self-stratifying microbial fuel cell: Towards height miniaturisation

The scalability of bioelectrochemical systems is a key parameter for their practical implementation in the realworld. Up until now, only urine-fed self-stratifying microbial fuel cells (SSM-MFCs) have been shown to be scalable in width and length with limited power density losses. For practical reasons, the present work focuses on the scalability of SSM-MFCs in the one dimension that has not yet been investigated, namely height. Three different height conditions were considered (1 cm, 2 cm and 3 cm tall electrodes). The normalised power density of the 2 cm and 3 cm conditions were similar either during the durability test under a hydraulic retention time of approximate to 39 h (i.e. 15.74 +/- 0.99 mu W.cm(-3)) and during the polarisation experiments (i.e. 27.79 +/- 0.92 mu W.cm(-3)). Conversely, the 1 cm condition had lower power densities of 11.23 +/- 0.07 mu W.cm(-3) and 17.73 +/- 3.94 mu W.cm(-3) both during the durability test and the polarisation experiment, respectively. These results confirm that SSM-MFCs can be scaled in all 3 dimensions with minimal power density losses, with a minimum height threshold for the electrode comprised between 1 cm and 2 cm. (C) 2019 The Authors. Published by Elsevier B.V.