Microwave‐Assisted Subcritical Water Extraction Method for the Optimized Isolation of Cellulose From Residual Soybean Hulls

Agro-industrial lignocellulosic wastes represent a huge source of biopolymers, proteins, carbohydrates, and active compounds. Their fractionation through eco-friendly routes is a challenge in accessing the components of interest while minimizing environmental impacts. In this study, a 20-min microwave-assisted subcritical water extraction (MASWE) was selected to isolate cellulose from soybean hulls. This emerging green hydrothermal process, coupled with a microwave-assisted alkaline (MW-NaOH) treatment, enabled the reduction of harsh chemical employment compared to classical biomass fractionation, ensuring, at the same time, a high cellulose enrichment of up to 91.5% in the best procedure. The environmental impacts of the up-scaled optimized strategy were compared to those of the multi-hydrolysis treatment through a life-cycle assessment analysis. The MW-based cellulose extraction provides clear advantages in toxicity-related categories, but it is still necessary to reduce the energy-driven impacts.