Performance of a scaled-up Microbial Fuel Cell with iron reduction as the cathode reaction

► We studied performance of a scaled-up MFC with iron reduction at the cathode. ► The projected surface area was 0.5 m 2. ► At maximum performance, the MFC produced 2.0 W m −2. ► Cathode performance increased compared to oxygen reduction on the same material. ► Cathode was still the main limiting factor. Scale-up studies of Microbial Fuel Cells are required before practical application comes into sight. We studied an MFC with a surface area of 0.5 m 2 and a volume of 5 L. Ferric iron (Fe 3+) was used as the electron acceptor to improve cathode performance. MFC performance increased in time as a combined result of microbial growth at the bio-anode, increase in iron concentration from 1 g L −1 to 6 g L −1, and increased activity of the iron oxidizers to regenerate ferric iron. Finally, a power density of 2.0 W m −2 (200 W m −3) was obtained. Analysis of internal resistances showed that anode resistance decreased from 109 to 7 mΩ m 2, while cathode resistance decreased from 939 to 85 mΩ m 2. The cathode was the main limiting factor, contributing to 58% of the total internal resistance. Maximum energy efficiency of the MFC was 41%.