Biochar waste derived electrodes performances in different bioelectrochemical applications

Microbial fuel cells (MFC), microbial electrolysis cells (MEC) and microbial electrosynthesis (MES) are environmentally friendly technologies that enable the use of organic waste as a source to produce renewable bioenergy. To optimise these systems and enhance bioenergy production the choice of cathode material is crucial. This work studied the performances of two ad hoc biochar-based cathode materials: one obtained from pyrolysis of organic fraction of municipal solid waste (OW) and the other of woody chips (WC). The use of these two materials was explored in the context of three different bioelectrochemical reactors scope: MFC, MEC and MES. Cathodes were characterized through composition (C, N, mineral content and fibres distribution), pH, specific surface area and infrared spectroscopy; then production of electricity, methane (CH4), and volatile fatty acids (VFAs) was described from carbon dioxide (CO2); and finally the microbial community was explored through 16S rRNA gene sequencing. WC-based electrodes performed better than OW-based ones. WC generated twice the amount of electricity than OW in MFC modality. In MEC modality, WC achieved both higher CH4 production and concentration than OW . In MES modality, WC produced ten times more acetic acid than OW . Best WC-biochar cathode performance was attributed to its higher Brunauer Emmett Teller (BET) value and its carbonaceous graphite-like structure.