Study on low temperature oxidation and thermal safety of biochar

Low-temperature oxidation behavior and thermal safety of biochar are crucial considerations during its storage. This study investigated the physicochemical structures and oxidation behavior of corn stalk chars produced at 400-600 °C using thermal analysis and a custom static oxidation system to assess oxygen consumption and gas emissions. Oxidation kinetics were modeled through AKTS thermodynamic analysis. Results revealed enhanced aromaticity and reduced aliphatic/oxygen groups with increasing pyrolysis temperature, along with an inverse relationship between pyrolysis temperature and biochar's activation energy/spontaneous combustion tendency. Oxygen consumption decreased with higher pyrolysis temperatures and lower ambient temperatures, reaching minimum values for 600 °C biochar at 40 °C and maximum for 400 °C biochar at 130 °C. Ethane emerged as the primary gaseous oxidation product. Although all biochars showed low ambient-temperature reactivity risks, their spontaneous combustion potential escalated with elevated environmental temperatures and reduced pyrolysis temperatures. The findings highlight pyrolysis temperature optimization as critical for balancing biochar stability and safety across storage conditions.