Thermokinetic Mapping of Activation Energy Evolution from Biomass to Biochar and Activated Carbon

Introduction: Understanding the thermokinetic evolution of biomass-derived carbons is critical for optimizing their structural stability and functional performance in advanced applications. Agricultural residues, such as pepper, tomato, and eggplant waste, offer sustainable carbon precursors; however, the evolution of activation energy during their transformation into biochar and activated carbon remains poorly understood. Methodology: Raw biomass, derived biochars, and KOH-activated carbons were systematically investigated using thermogravimetric analysis under controlled heating conditions. Kinetic parameters were determined by combining the Arrhenius, Coats – Redfern, and isoconversional Kissinger – Akahira – Sunose/Ozawa – Flynn – Wall models to track changes in activation energy throughout the conversion pathway. Results and Discussion: The materials exhibited multistage thermal degradation behavior, with significant mass losses associated with hemicellulose and cellulose decomposition between 200 and 400°C. Progressive shifts of Tmax toward higher temperatures and increased residual mass from biomass to activated carbon indicated enhanced carbon consolidation and thermal stability. Activation energy increased systematically from raw biomass (−66 to 55kJ mol−1) to biochar (63–93kJ mol−1), reaching up to 118kJ mol−1 for activated carbons, reflecting a transition to carbon lattice – controlled kinetics. Conclusion and Recommendations: This study elucidates the structure – reactivity transformation from biomass to engineered carbons driven by aromatization and stabilization. The presented thermokinetic mapping provides a rational framework for designing biomass-derived carbons tailored for adsorption, catalysis, and energy storage applications.