Novel laser-driven fast pyrolysis of biomass: Insights into biochar characteristics and applications

Biomass pyrolysis is a promising technology for producing biochar, but conventional methods often lack precise control over heating rates and real-time monitoring, particularly in fast pyrolysis. A novel laser-driven fast pyrolysis (LFP) system was developed, achieving ultrafast heating rates (100°C/s) and enabling non-contact temperature measurement through infrared thermometry. Experiments were conducted using poplar wood as feedstock, with heating rates of 10°C/s and 100°C/s, spanning temperatures from 400°C to 700°C. Results showed that fast heating significantly reduced biochar yield, predominantly below 400°C due to rapid devolatilization. The pore volume and specific surface area began increasing within a distinct temperature range (500-600°C), independent of heating rates. However, at 600°C, pore volume decreased by sixfold (0.127 → 0.021 ml/g) and specific surface area by eightfold (223.71 → 27.83 m²/g) under fast heating, accompanied by a four orders of magnitude electrical resistivity decrease (4.68e4 → 5.81 Ω·cm). These findings demonstrate the feasibility of the LFP system for providing critical technical parameters and guidance in optimizing biochar properties, particularly under fast heating conditions. By elucidating the effects of heating rates on biochar yield, porosity, specific surface area, and electrical resistivity, this study offers valuable insights into sustainable biomass conversion technologies.