Processing of lignocellulose in ionic liquids: A cleaner and sustainable approach

In the wake of developing a sustainable future, the valorization of abundant, eco-friendly, and renewable lignocellulose resources is of immense importance. The pretreatment of lignocellulose is inevitably an important step for getting value-added products as the complicated structure of biomass defies its effectual utilization. Compared to conventional pretreatment technologies that have negative impacts on the environment, ionic liquids have emerged as promising green solvents with a cutting-edge influence in lignocellulose processing. Ionic liquids have the capability of replacing conventional chemicals and solvents owing to their distinctive physical, biological, chemical, and thermal attributes. The tunable properties of ionic liquids have an impeccable impact on numerous applications, especially on the lignocellulose pretreatment and direct conversion into biochemicals and biofuels. The major motivation of this review is to provide a detailed discussion on the cleaner deconstruction and dissolution mechanism, the effect of different anions and cations, and the direct conversion of lignocellulose in valued chemicals (total reducing sugars, 5-Hydroxymethylfurfural, and levulinic acid). Based on this review, some identified research gaps, including the synthesis of low-cost ionic liquids, ionic liquids/co-solvent combinations, and ionic liquid pretreatment process integration, are needed to be further discussed in the future.