Enhanced crosslinking via epoxidized soybean oil and tannin acid for producing metallurgical grade biomass-derived coke: From waste material to a carbon–neutral product

The steel industry is responsible for 30 % of global industrial greenhouse gas emissions, which is mainly dependent on metallurgical coke utilization. Although biochar represents a promising carbon–neutral alternative, its suboptimal mechanical properties have hindered its direct substitution for conventional coke. This work introduces an innovative hydrothermal carbonization-repolymerization strategy to synthesize high-performance biocoke from sustainable feedstocks of oak residues and waste soybean oil. Our approach is centered on a novel and bio-based polymerization agent, synthesized by blending epoxidized soybean oil from oxidized waste oil and tannic acid extracted from oak residues in a 3:1 mass ratio. The epoxidized soybean oil-tannic acid effectively undergoes cross-linking reactions with oak biochar and oak bio-oil that both in-situ generated from the hydrothermal carbonization, resulting in a highly cross-linked biocoke. The ESO undergoes epoxy ring-opening in the cross-polymerization reaction, providing more reaction sites for cross-linked reactions. Moreover, the resulting biocoke shows a significant aromatization and graphitization structure. Therefore, the biocoke displays superior mechanical and thermochemical properties, including crushing strength (86.0 % of M 40 ), abrasion resistance (6.6 % of M 10 ), coke strength after reaction (64.2 %), and higher heating value (40.79 MJ/kg), meeting the performance of first-grade metallurgical coke. A cradle-to-gate LCA indicates that substituting 50 % of metallurgical coke by biocoke results in a reduction of CO 2 emissions of 622.8 kg for per ton of iron production. This study not only provides a novel polymerization strategy for producing metallurgical-grade biocoke but also highlights its potential to significantly reduce the carbon footprint of the steel industry.