This study investigates bed material aging in industrial-scale fast pyrolysis of biomass, focusing on the roles of particle morphology, ash accumulation, and alkali release in bio-oil yield and composition. Fresh and used bed materials from a commercial pyrolysis reactor were characterized by particle size analysis and SEM/EDS, revealing fragmentation and the development of AAEM-rich ash layers. Alkali release and migration were assessed using a TGA–Surface Ionization Detector (SID) setup, while lab-scale fluidized-bed pyrolysis experiments tested fresh, aged, and different size fractions of the aged bed. GC/MS analysis showed consistent suppression of oxygenated functions in all used bed samples. A bio-oil yield reduction of 8.3% was observed for the fine fraction ('140 μm), compared with only 1% for the coarse fraction ('220 μm), indicating the combined influence of ash accumulation and particle morphology. These findings underscore the catalytic role of AAEM species and offer guidance for ash-management strategies in fast pyrolysis processes.

Red mud is a hazardous waste of the alumina refining process, with 1–1.5 tons generated per ton of alumina produced. This study presents a first-of-its-kind understanding of a biomass-based pathway for recovering iron from red mud. Simultaneous red mud reduction and biomass gasification (SRG) is proposed as a viable pathway to produce zero-valent iron. This metallic iron can potentially be recovered by weak magnetic separation and integrated into the iron-making industry. The steps of the red mud-biomass phenomena were investigated through thermogravimetric analysis followed by XRD characterization. Complete reduction from Fe³⁺ to Fe⁰ was achieved at temperatures near 900 °C and verified by XRD, XPS, and FTIR. Bench-scale SGR experiments were also performed to survey the compositions of gaseous and tar products. Bench-scale SRG experiments confirmed increased syngas (CO and H₂) production and demonstrated the tar-cracking catalytic activity of red mud.