Anode biofilm maturation time, stable cell performance time, and time-course electrochemistry in a single-chamber microbial fuel cell with a brush-anode

Abstract For accurate and reproducible experimental data in the MFC research, it is important to know when MFCs produces stable cell performance. Herein, four replicate single-chamber MFCs were tested for 17 weeks by using polarization and cyclic voltammetry (CV) tests. The strong MFCs (#2,4,3) showing continuous performance enhancement initially (3-9 weeks) produced good subsequent performance (9-17 weeks). MFC-1 experienced a performance drop initially and showed bad subsequent performance. MFCs performance became stable after 9 weeks. The strong MFCs produced power 2.8-3.6 times higher and anode resistance 7.5-23.9 times lower than the weak MFC-1. However, cathode resistances were similar in all MFCs. CV results showed anodic current production increased continuously in all MFCs, indicating anode biofilms kept growing. However, MFC performance did not increase accordingly. Anodic CVs had a typical S-shape curve, but those of MFC-1 showed straight lines from the 9th week. The weak MFC-1 showed smaller CV currents and thinner CV curves than the strong MFCs. In the 17th week of MFC-1, as the anode resistance was reduced by 47%, anodic current and MFC performance increased. Regression analysis showed anode resistance was a major performance limiting factor of the weak MFC and cathode resistance was that of the strong MFCs. Conclusively, 1) Initial MFC performance determines subsequent performance, 2) Stable cell performance time is 9 weeks, 3) Anode maturation time is more than 17 weeks, 4) Improve anodes in weak MFCs and cathodes in strong MFCs.