ABSTRACT
Environmental applications (e.g., wastewater treatment, bioremediation, etc.) of microbial electrochemical technologies (METs) can be implemented at large-scale if bioelectrodes are not fabricated with expensive materials. Several different types of METs are currently under development at pilot and full-scale, where traditional carbon-based high-tech electrode materials (e.g., carbon fibers, cloths and felts, graphite, etc.) are not ideal candidates. Biomass-derived charcoal can be obtained in large amounts by relatively sustainable and feasible carbonization processes (i.e., pyrolysis, hydrothermal carbonization) of agro-forestry residues. Because biochar has often been considered a relatively low-conductive material, its application in METs has been relatively limited and the literature on this topic is relatively scarce. However, biochar has been largely studied by materials scientists, as well as by soil scientists, for other applications and under different points of view.
Here, we explore these different literature fields and we propose a new class of ‘electroactive biochar’ (e-biochar) with enhanced properties for bioelectrodes that can be sustainably produced at large scales. The electroactive properties of such materials (e.g., electrical conductivity, capacitance, superficial redox functional groups, porosity distribution and capacity to host electroactive microbial communities) can be optimized under the point of view of METs by playing with the characteristics of precursor biomass, the thermochemical processes conditions as well as pre-, in situ and post treatments. The methods to rigorously characterize and tailor e-biochar’s properties are also discussed, together with the most relevant (multidisciplinary) research challenges, toward application in METs.
