Properties of biomass-derived biochars: Combined effects of operating conditions and biomass types

Combined effects of operating conditions including heating temperature (200-700 °C), time (1-8 h) and rate, and atmosphere (air-flow, air-limited and N2) on the physicochemical properties of biochars with pine sawdust, maize straw and sugarcane bagasse as feedstocks were investigated. The results demonstrated that production temperature and atmosphere acted as the predominant factors that determined the properties of biochars. The X-ray diffraction data confirmed the occurrence of phase transition in the biomass structures at around 400 °C. Heating time and rate showed little effect on the functional group compositions of the biochars within 8 h, particularly under N2 atmosphere. In addition, the molecular weights of the biochar-derived dissolved organic carbon tended to increase with increasing temperature. Feedstock type also affected the biochar properties by the compositional differences in mineral salts and cellulose/lignin in the three biomass materials. This work provides important information for optimizing procedures for biochar production with desired properties and high yield.