Ionic liquids: A milestone on the pathway to greener recycling of cellulose from biomass

The capacity to consider more environmentally benign fiber processing schemes should consider ionic liquids (ILs) and their potential for biomass recapture. Ionic liquids are observed to have excellent properties for use as industrial solvents for biomass with cellulose solubilities ranging from 10-20 wt%, negligible vapor pressures, and melting points as low as - 20 degrees C. Here we consider the thermophysical properties of ILs in the context of the extraction of cellulose from biomass and compost residues that contain impurities including sugars, inorganic residues, water, and lignin among other constituents. The rationale to consider biomass and compost for fibrous isolation is due to the potential for value added sourcing of raw materials from conventional waste streams, and the environmental benefit of reducing the volume of standing agriculture wastes. Recent endeavors have shown great promise in the direct spinning of biomass derived fibers and isolates from select IL mediums. This review includes details on IL structure and thermophysical properties, efforts to consider what is known about cellulose interaction and dissolution within ILs, details on the theology of cellulose bearing ILs, and comments on potential gaps in knowledge worth pursuing to gauge the value proposition of extracting cellulose directly from compost. With so many different types of structures that can form ILs, further optimization is required to gauge the nexus of IL synthesis costs, IL solubility of cellulose both dry and wet, and the ability to easily perform these extractions and purifications robustly at the compost source.