Chemical Composition and Reactivity of Quercus Pubescens Bark and Bark Fractions for Thermochemical Biorefinery Applications

Abstract

Advancing circular bioeconomy in thermochemical biorefineries requires species-specific data that link biomass composition and thermochemical performance. Here, we provide the first integrated thermochemical dataset for Quercus pubescens bark combining FT-IR, XRD, XRF, TGA, and measured ash fusion temperatures (AFT). The results reveal that bark is enriched in phenolic extractives (21.2%) and inorganics (15%), with calcium oxalate monohydrate (COM) dominating the inorganic fraction, as confirmed by FT-IR and XRD. Thermal decomposition occurs between 150 degrees C and 690 degrees C. Pyrolysis follows diffusion-controlled kinetics, with apparent activation energies for bark and its fractions ranging between 70 and 103 kJ mol-1. Extraction increases the activation energy of bark. The ash exhibits a high AFT (softening: 1421 degrees C, flow: 1467 degrees C), placing this feedstock within the low-slagging, moderate-fouling range compared to other lignocellulosics. The observed COM-to-CaCO3/CaO transformation upon heating contributes to the elevated AFT. Reactivity analyses of bark fractions support thermochemical biorefinery routing of fractions: extracted bark (EB) and desuberinised bark (DB) are highly reactive and well-suited to combustion/gasification, whereas raw bark (B) and Klason lignin (KL) exhibit higher thermal stability and yield more persistent char, favoring slow pyrolysis for biochar production. Such routing strategies optimize energy recovery and also enable co-products with environmental co-benefits.