Cedar Wood-Based Biochar: Properties, Characterization, and Applications as Anodes in Microbial Fuel Cell

In this study, the relationship between pyrolysis temperature of woody biomass and physicochemical properties of derived biochar was investigated for microbial fuel cell (MFC) application. Physical and chemical properties of biochar were characterized for different pyrolysis temperatures. Results showed that biochar obtained at 400 °C was not conductor, while biochars prepared at 600 °C, 700 °C, and 900 °C exhibited decreased electrical resistivity of (7 ± 6) × 10³ Ω.m, (1.8 ± 0.2) Ω.m, and (16 ± 3) × 10^-3 Ω.m, respectively. Rising pyrolysis temperature from 400 to 700 °C exhibited honeycomb-like macroporous structures of biochar with an increase in the specific surface area from 310 to 484 m².g^-1. However, the production of biochar at 900 °C reduced its specific surface area to 136 m².g^-1 and caused the loss of the ordered honeycomb structure. MFCs using anodes based on biochar prepared at 900 °C produced maximum power densities ((9.9 ± 0.6) mW.m^-2) higher than that obtained with biochar pyrolyzed at 700 °C ((5.8 ± 0.1) mW.m^-2) and with conventional carbon felt anodes ((1.9 ± 0.2) mW.m^-2). SEM images of biochar-based anodes indicated the clogging of macropores in honeycomb structure of biochar prepared at 700 °C by growth of electroactive biofilms, which might impede the supply of substrate and the removal of metabolites from the inside of the electrode. These findings highlight that electrical conductivity of biochar is the major parameter for ensuring efficient anodes in microbial fuel cell application. Schematic representation of cedar wood-based biochar and its application as anode in MFC.