Electricity generation influenced by nitrogen transformations in a microbial fuel cell: assessment of temperature and external resistance

Abstract

Microbial fuel cells (MFC) generate clean energy from organic wastes. This study reports the development and application of novel lab-scale MFC with granular activated carbon-modified electrode fed with synthetic sugarcane vinasse. Biological activity involving nitrogen in the cathode chamber was assessed as a strategy to improve cathode performance under different temperatures (~25, 35 and 55 °C) and external resistance (13 and 300 Ω). High organic matter removal (>90%) was obtained regardless of the condition applied. Nitrification occurred in the cathode chamber at temperature up to 35 °C; this resulted in a decrease in pH to <7, which favored the cathode performance. The anode, applied at 35 °C and 55 °C, presented lower internal resistance and more negative potentials; this shows that the temperature reduced the anode overpotentials. The application of 13 Ω external resistance promoted higher electrogen activity, which resulted in coulombic efficiency up to 12.6 ± 2.4% against 1.9 ± 0.2% at 300 Ω. The combination of the proposed configuration, operation and electrode materials yielded maximum power density of 41.3 W m−3, which is higher than values reported by other studies with similar electrode materials, reactor configuration (not stacked) and substrate composition (diversified). The findings contribute to the development of scalable renewable energy generation systems based on combination of biochemical and bioelectrochemical processes in wastewater treatment.