Comparison of torrefaction characteristics and structural evolution of agroforestry residues: A study on pine wood and peanut shell

Abstracts To realize energy sustainable development and climate change mitigation, developing efficient energy utilization for forestry and agricultural residues is a critical strategy by thermochemical pretreatment such as torrefaction. In the study, pine wood and peanut shells are selected as biomass feedstocks. Torrefaction is conducted under a nitrogen atmosphere at 200 oC, 230  oC, and 260  oC for 60 min to investigate biomass quality and structural evolution. Torrefied biomass are characterized through proximate analysis, elemental analysis, higher heating value (HHV) measurement, Hardgrove Grindability Index (HGI) determination, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance (SSNMR), and thermogravimetric analysis (TGA). Results show that torrefaction significantly improves biomass physical and chemical characteristics. As the torrefaction temperature increases, heating value improves significantly along with volatile content decrease and fixed carbon content increases. Pine wood exhibits an HHV of 23.041 MJ/kg and HGI of 164 at 260  oC. SEM analysis revealed a looser surface structure after torrefaction, significantly improving the biomass grindability. Torrefaction is an effective pretreatment method for enhancing the quality of agroforestry residues to improve utilization efficiency.