Thermodynamic and Kinetic Insights into Biochar Production from Empty Fruit Bunches: A Volatile-State Approach

Abstract This study presents the novel integration of a volatile-state perspective into the Kissinger-Akahira-Sunose (KAS) kinetic model for empty fruit bunches (EFB) pyrolysis, addressing key limitations of conventional solid-state models that assume full conversion and neglect volatile emissions and ash formation. Unlike traditional approaches, the modified volatile-state KAS method captures the dynamic behavior of volatile compounds during thermal decomposition, yielding an average activation energy reduction of 14.2% compared to the solid-state method. Thermogravimetric analysis (TGA) shows a non-linear variation in activation energy with conversion, reflecting complex structural changes in EFB. The volatile-state model provides a more consistent activation energy (151.99 kJ/mol) and high correlation coefficients (R² up to 0.9993), affirming its reliability. Additionally, thermodynamic parameters—enthalpy (ΔH = 147.27 kJ/mol) and Gibbs free energy (ΔG = 100.57 kJ/mol)—are derived to deepen the mechanistic understanding of the process. By integrating kinetic and thermodynamic insights with this novel framework, the research offers a more accurate and predictive model for optimizing energy-efficient biochar production, with significant implications for sustainable energy, waste management, and carbon sequestration industries.