Oxidative Fast Pyrolysis Enabling Autothermal Production of Porous Functionalized Biochar and Anhydrosugar/Phenol‐Rich Bio‐Oil From Biomass

ABSTRACT Oxidative fast pyrolysis can potentially overcome the heat‐supply bottleneck of conventional fast pyrolysis by enabling autothermal operation while also tailoring product quality through controlled oxygen addition. Here, pine sawdust was continuously fed (300 mg/min) into a fluidized‐bed reactor at 500°C under oxygen equivalence ratios (ER) of 0%–11.15% (O ₂ concentration: 0–2.35 vol.%). Compared with nonoxidative fast pyrolysis, introducing oxygen primarily oxidized biochar, reducing its yield while promoting micropore development and surface functionality (e.g., −OH and C=O groups), especially at ER above 7.17%. Increasing ER did not decrease but instead increased bio‐oil yield across the tested ER range (0%–11.15%), attributed to enhanced holocellulose depolymerization and additional water formation through oxidation reactions. Light oxygenated compounds (e.g., furans and cyclopentanones) underwent partial oxidation, whereas phenols/aromatics and anhydrosugars were retained in bio‐oil. Furthermore, O ₂ introduction markedly boosted non‐condensable gas production via the formation of additional CO and CO ₂ , with CO ₂ surpassing CO at ER > 8%. A combined techno‐economic analysis and life‐cycle assessment, including sensitivity analysis for product substitution quality, demonstrated that oxidative fast pyrolysis exhibited favorable economic and environmental performance, benefiting from reduced heat demand and improved process integration. Overall, oxidative fast pyrolysis presents a promising pathway for scalable, energy‐efficient production of bio‐oil and functional biochar while demonstrating the necessity of balancing oxygen ER against bio‐oil water formation and product‐quality constraints.