Advancing pulping-based biorefining of sugarcane bagasse via sequential microwave-assisted strategies for co-production of hemicellulose and pulp

The conventional soda-anthraquinone (soda-AQ) pulping process, though effective for delignification and fibre separation, is energy- and alkali-intensive and results in poor hemicellulose recovery. This study proposes an improved strategy: microwave-assisted sequential fibre expansion and alkaline extraction pretreatment integrated with soda-AQ pulping, enabling co-production of high-quality hemicellulose and cellulose pulp from sugarcane bagasse. Fibre expansion parameters were optimized to enhance hemicellulose yield during subsequent alkaline extraction. Physicochemical changes in the biomass were systematically investigated, and mechanistic analysis revealed that the synergistic thermal and mechanical effects of fibre expansion significantly improved hemicellulose dissolution by lowering the activation energy for exfoliation. Compared to the conventional soda-AQ process, this method reduced pulping time from 90 to 30 min, processing temperature from 155 °C to 130 °C, and alkali consumption from 22 % to 20 %. Importantly, it preserved hemicellulose integrity and yielded up to 60 % screened pulp with a satisfactory Kappa number of 15. Kinetic models describing delignification were developed and validated. The recovered high-molecular-weight hemicellulose shows strong potential for biodegradable films and biomedical applications. Preliminary economic analysis supports the feasibility of this integrated process. Overall, the microwave-assisted sequential fibre expansion and alkaline extraction pretreatment offers a promising, energy-efficient biorefinery approach for the sustainable valorisation of sugarcane bagasse.