Comparative thermal and structural analysis of biochar from rapeseed meal and Fraxinus excelsior sawdust

• Biochar was produced from rapeseed meal and Fraxinus excelsior sawdust via slow pyrolysis. • Comprehensive thermal, chemical, and structural characterization was performed. • FTIR and Raman confirmed stable carbon structures and functional group variations. • TGA and DSC revealed strong thermal stability and distinct energy retention behavior. • Statistical analysis validated differences in carbon content and thermal properties. This study investigates the production and thermal characterization of biochar derived from two biomass sources: rapeseed meal and sawdust of Fraxinus excelsior. Biochars were produced through slow pyrolysis at 350°C, and their chemical composition, thermal stability, and carbon structure were analyzed using FTIR, Raman spectroscopy, CHNS analysis, TGA/DTG, and DSC. The results showed high fixed carbon contents of 59.3% for rapeseed meal and 57.6% for wood-based biochars, with sulfur contents below 0.1%. FTIR and Raman analyses confirmed the formation of stable carbonaceous structures with characteristic functional groups. TGA revealed strong thermal stability, with residual masses of 42% and 47% at 1000°C for rapeseed and wood biochars, respectively. DSC analysis demonstrated that wood-derived biochar retained more energy, while rapeseed biochar exhibited higher carbon content. A statistical comparison using bootstrap, effect size, and Bayesian estimation confirmed these trends. Overall, both biochars demonstrate strong potential as sustainable, carbon-rich alternatives for high-temperature industrial applications.