Pyrolysis temperature had effects on the physicochemical properties of biochar

Biochar is the carbon-rich product obtained when biomass is anaerobically heated. In this study, different materials (corn straw and peanut shell) and pyrolysis temperatures (350, 450 and 550 °C) affect the elemental composition, surface structure, and biochar properties. The results showed that the carbon (C) content in biochar increased as the temperature increased, but hydrogen (H) and nitrogen (N) did not change. The alkane overpressure of corn straw and peanut shell increased first and then decreased with the increased temperature; the fatty alkyl chain disappeared, but the ash content increased at 550 °C. At high temperatures, the aromaticity (H/C ratio) and hydrophobicity (O/C ratio) of biochar become "carbon-rich particles", while the polarity (O + N)/C decreases significantly. The pore wall of biochar became thinner with the increase in pyrolysis temperature, the internal pore structure became larger, and a large number of micropores appeared in biochar. Biochar pyrolysed at 550 °C has much higher C, ash content, pore, and stronger buffering capacity, and thus is more promising to improve soil health.