Production and Characterization of Slow Pyrolysis Biochar

Abstract

Biochar is charred material produced from biomass, i.e. by means of pyrolysis, with the intention to be used as a soil amendment and as a method to permanently store CO2 in the soil. In this study, the effect of slow pyrolysis process conditions and biomass feedstock type on key characteristics of the produced biochar was studied. Feedstocks included pine wood, wheat straw, green waste and dried algae while process conditions investigated during batch, slow pyrolysis included treatment temperature and residence time. In proximate analysis of the produced biochars, it was found that the fixed C­content strongly depended on the intensity of the thermal treatment, while the actual yield in fixed carbon was practically insensitive to the treatment temperature or residence time. The pH in solution, higher heating value and BET surface positively correlated with pyrolysis temperature. Finally, in soil incubation tests, it was found that the addition of biochar to the soil initially reduced the C­mineralization rate, indicating that the soil microculture needs to adapt to the new conditions, which was more pronounced when adding chars with high fixed C­content, as chars with low C­content had a larger amount of volatile, easier biodegradable, C­ compounds.