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<p>Rice husk (RH), an abundant agricultural by-product, offers significant potential for sustainable energy generation and material recovery due to its lignocellulosic composition and high silica content. We conducted a detailed thermo-kinetic analysis of RH under inert and oxidative atmospheres. Initial characterization showed that RH is primarily composed of cellulose (56.6%, mass fraction), lignin (30.3%), and hemicellulose (7.5%), with a high ash content (25.2%) dominated by silica (SiO<sub>2</sub>: 254086.65&#xa0;mg/kg). This makes RH a valuable source of amorphous silica, though it may cause slagging, fouling, and maintenance challenges in high-temperature thermochemical systems. Under combustion, oxygen accelerated devolatilization, resulting in higher mass loss, lower activation energies (99.09–114.95&#xa0;kJ/mol), and faster kinetics compared to pyrolysis (hemicellulose: 4.06–29.17&#xa0;kJ/mol; cellulose: 158.80–188.71&#xa0;kJ/mol; lignin: 61.43–79.81&#xa0;kJ/mol). Thermodynamic analysis indicated that oxidation promoted more ordered transition states and reduced energy barriers, enhancing the conversion efficiency. Performance indices were introduced to evaluate combustibility, ignition, and reactor safety. During pyrolysis, RH components transitioned from diffusion- or nucleation-controlled kinetics at low conversions to reaction-order control at higher conversions. Combustion initially followed chemical control, shifted to diffusion-limited kinetics as char and ash accumulated, and reverted to chemical control during residual carbon oxidation. Lignin displayed complex, multi-step kinetics under both conditions. These results provide a comprehensive understanding of RH thermal behavior, supporting the design of more efficient and safer thermochemical systems and valorization strategies, including energy recovery, biochar, syngas generation, and amorphous silica extraction for sustainable bio-based industries.</p> Graphical abstract <p></p>

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Thermo-kinetic and reactivity analysis of rice husk and its macromolecular constituents during thermochemical conversion for sustainable valorization

  • 期刊论文

  • 发表日期：

    2026年4月30日

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  • Hamado Ouedraogo,
  • Yohan Richardson,
  • María González Martínez,
  • Sayon dit Sadio Sidibe,
  • Ange Nzihou

摘要

Rice husk (RH), an abundant agricultural by-product, offers significant potential for sustainable energy generation and material recovery due to its lignocellulosic composition and high silica content. We conducted a detailed thermo-kinetic analysis of RH under inert and oxidative atmospheres. Initial characterization showed that RH is primarily composed of cellulose (56.6%, mass fraction), lignin (30.3%), and hemicellulose (7.5%), with a high ash content (25.2%) dominated by silica (SiO2: 254086.65 mg/kg). This makes RH a valuable source of amorphous silica, though it may cause slagging, fouling, and maintenance challenges in high-temperature thermochemical systems. Under combustion, oxygen accelerated devolatilization, resulting in higher mass loss, lower activation energies (99.09–114.95 kJ/mol), and faster kinetics compared to pyrolysis (hemicellulose: 4.06–29.17 kJ/mol; cellulose: 158.80–188.71 kJ/mol; lignin: 61.43–79.81 kJ/mol). Thermodynamic analysis indicated that oxidation promoted more ordered transition states and reduced energy barriers, enhancing the conversion efficiency. Performance indices were introduced to evaluate combustibility, ignition, and reactor safety. During pyrolysis, RH components transitioned from diffusion- or nucleation-controlled kinetics at low conversions to reaction-order control at higher conversions. Combustion initially followed chemical control, shifted to diffusion-limited kinetics as char and ash accumulated, and reverted to chemical control during residual carbon oxidation. Lignin displayed complex, multi-step kinetics under both conditions. These results provide a comprehensive understanding of RH thermal behavior, supporting the design of more efficient and safer thermochemical systems and valorization strategies, including energy recovery, biochar, syngas generation, and amorphous silica extraction for sustainable bio-based industries.

Graphical abstract