Thermochemical Conversion of Beech Wood Residues in a Fixed-Bed Reactor: Product Yields and Quality Analysis under Varying Pyrolysis Temperatures

This study explored the pyrolytic conversion of beech wood residues in a fixed-bed reactor across temperatures from 370 ◦ C to 550 ◦ C to assess their potential for bioenergy production. Pyrolysis produced three main products: bio-oil, biogas, and biochar, with their yields varying according to temperature. The highest bio-oil yield (62.1 wt.%) was observed at 420 ◦ C, while biogas yield increased with temperature, reaching 30.4 wt.% at 550 ◦ C. Biochar yield decreased from 39.5 wt.% at 370 ◦ C to 21.5 wt.% at 550 ◦ C as a result of enhanced thermal cracking. Properties of biochar improved at higher temperatures, with increased carbon content (from 74.9 wt.% to 85.2 wt.%) and higher heating value (from 28.4 MJ/kg to 30.2 MJ/kg), indicating better fuel quality. Chemical analysis of bio-oil showed a shift from carboxylic acids to ketones, phenols, and aromatics as the temperature elevated. The biogas composition was enriched in methane and light hydrocarbons at elevated temperatures, boosting its heating value from 9.7 MJ/kg to 11.9 MJ/kg. These findings demonstrate that temperature plays a crucial role in determining product yield and quality, positioning beech wood residues as a promising feedstock for renewable bioenergy and carbon-based products.