Fast Pyrolyzed Residue Assembled Into Carbon Spheres: Effect of Self‐Template on the Structure Behavior and Improved Hierarchical Pore Structures

Carbon residue is a waste by‐product produced during the rapid pyrolysis of biomass into bio‐oil, and the fragile nature and poor pore processability making it difficult to dispose. In this study, carbon residues obtained from various biomasses waste are self‐assembled into macroscopic porous carbon spheres (CSs), through interactions with cellulose nanofibrils (CNF) and in situ treatment by KOH to remove their high ash content. The micro‐ and meso‐pore structure of CSs can be influenced by the type of raw biomasses, pyrolysis heating rate and structure‐directing agent, through KOH removal of multiscale ashes and morphology controlling of CSs. Compared to fast pyrolyzed woody biomass, the resulting CSs derived from silicon‐rich biomass residue shows superior mesopore volume ranging from 0.3 cm 3 /g to 0.5 cm 3 /g, owing to the ash self‐templates (nonmetallic oxides). The optimized CS from fast pyrolyzed bamboo residue demonstrates the best shape factor (0.78), highest carbon oxide (CO 2 ) gravimetric adsorption capacity (1.8 mmol/g), and low regeneration energy (32 kJ/mol). The life cycle assessment shows the carbon reduction potential of fast pyrolysis residue derived CSs was most contributed by the global warming potential of produced fixed carbon and bio‐oil, which is −557.85 kg CO 2 eq/t wastes. This study highlights a cost‐effective and sustainable strategy for CO 2 capture by carbon residue.