Work

Effect of Thermal Severity on the Structural Evolution and Stability of Rice Husk Biochar

Year: 2026

Type: article

Abstract: This study evaluates the effect of thermal severity on the yield, structural evolution, and stability of biochar produced from rice husk via controlled pyrolysis. The raw biomass, containing 1.67 wt% moisture, 60.94 wt% volatiles, and 21.66-wt% fixed carbon, proved highly suitable for thermochemical conversion. Using a 3 × 3 factorial design (500–700 °C; 30–60 min), variance analysis revealed temperature as the dominant variable (F = 67.15; p < 0.001; ηp2 = 0.88), alongside a significant temperature time interaction (F = 6.19; p = 0.003). Maximum biochar yield occurred at 500 °C and 60 min (59.4 ± 2.0 wt%), whereas heating to 700 °C reduced yields to 41.8–44.0 wt% via enhanced devolatilization and secondary cracking. Structurally, the biochar developed a predominantly mesoporous matrix with a maximum BET surface area of 56.23 m2/g and ~4.9 nm average pore diameters. Furthermore, FTIR and DSC analyses demonstrated that higher thermal severity reduced oxygen-containing functional groups while increasing thermal stability and aromatic reorganization. Ultimately, 700 °C (at the 45 min residence time evaluated for porosimetry) provided the greatest structural development (maximum BET surface area), while 700 °C/60 min provided the highest thermal-oxidative stability, and lower severities favored biochar yield, revealing a trade-off between mass recovery and structural/stability performance. These findings establish that thermal severity dictates the physicochemical evolution of rice husk biochar, offering vital criteria for optimizing energy and environmental applications.

Source: Biomass

DOI: 10.3390/biomass6040056