Effect of pyrolysis temperature and correlation analysis on the yield and physicochemical properties of crop residue biochar

•Pyrolysis temperature had similar effects on four different crop residues biochar.•The maximum losses rate in biochar was observed below 400 °C.•Rice straw biochars have high yield superiority.•Higher temperature biochars had high stability and an orderly crystal structure. The aim of this study was to evaluate how pyrolysis temperature influences the yield and physicochemical properties of biochar. We produced biochar from four feedstocks (wheat straw, corn straw, rape straw, and rice straw) pyrolyzed at 300, 400, 500, and 600 °C for 1 h, respectively. The results showed that all biochar yields decreased consistently with increasing temperature during pyrolysis and showed a steady decrease over 400 °C. Rice straw derived biochar had high yield superiority due to its higher content of ash. Pyrolysis temperature has significant effects on the properties of biochar; demonstrating a negative relationship with H, O, H/C, O/C, (O + N)/C, and functional groups, whilst having a positive relationship with C, ash, pH, electrical conductivity, and surface roughness. Higher pyrolysis temperature was beneficial to the formation of a more recalcitrant constitutions and crystal structure, making it available for material application.