Sustainable phosphorus recovery from wastewater and fertilizer production in microbial electrolysis cells using the biochar-based cathode

Reducing the energy consumption and electrode cost for electrochemical recovery of phosphorus (P) from wastewater is crucial for the large-scale application. In this study, biochar electrodes were investigated as the low-cost cathode in a microbial electrolysis cell (MEC) and this P-enriched biochar electrode was directly retrieved as P fertilizer after wastewater treatment. The Fe2+ salt modified biochar significantly increased the electrochemical performance of MECs due to the improved electrical conductivity and cathodic activity. Compared to the pristine biochar cathode, the current density of the MEC increased from 16.8 ± 0.2 A/m3 to 20.7 ± 0.8 A/m3, and the P removal increased from 28.8% ± 1% to 62.4% ± 3.5%. The power consumption was 0.25 ± 0.01 kWh/kg P which was more than one order of magnitude lower than the previous report. It was also demonstrated that the P enriched biochar amended soil improved the Pakchoi cultivation.