# Biomass and Cellulose Dissolution--The Important Issue in Renewable Materials Treatment
###### Abstract  
Sustainable development strategies, as well as the shift toward a circular bioeconomy, has led to high interest in the development and implementation of technologies that efficiently utilize biomass as a raw material. Switching from fossil-based to bio-based resources requires the consideration of many new challenges and problems. One of the crucial issues is the solubility of lignocellulosic or at least its ingredients. According to the trends and legislation, the selected chemicals and methods of dissolution/treatment should also be environmentally friendly. The pretreatment processes prepare biomass for further transformations (e.g., chemical, thermal including pyrolysis, or biological) to valuable products such as biofuels, bio- oils, Fine Chemicals, solvents, plastics, and many others. This review discusses the latest findings on the dissolution of biomass and its ingredients. The application of novel, green solvents such as ionic liquids or deep eutectic solvents is discussed in detail. The impact of the composition and structure of these solvents on the biomass/cellulose dissolution process, as well as the mechanism of cellulose-ionic liquid interaction, is presented. Some novel achievements in the usage of inorganic salts and specific metal complexes are also overviewed.  
lignocellulose; dissolution; inorganic salts; ionic liquids; deep eutectic solvents; delignification +
Footnote †: journal: Medical  
into valuable bioproducts. This includes the production of _Fine Chemicals_ and solvents (e.g., lactic acid, furfural, levulinic acid, 5-hydroxymethylfurfural), biofuels (e.g., bioethanol), or energy (Figure 1).  
The interest in biomass treatment is growing each year, which is reflected in the number of publications, e.g., in ScienceDirect (Figure 2).  
Biomass pretreatment is an important part of its further conversion and can be classified as physical, physicochemical, chemical, and biological. In many cases, the combination of several methods is used. Selection of the appropriate pretreatment method depends on many factors, e.g., the type of biomass, further conversion methods, or desired products. The goal of this step is to obtain more homogeneous raw materials and overcome all handling difficulties. After pretreatment. the biomass is more susceptible to further transformations (chemical, enzymatic, chemoenzymatic, or thermal) into desired products. When the production of biofuels is considered, many thermal methods have been investigated (e.g., torrefaction, gasification, pyrolysis, and hydrothermal methods). One of the most promising methods is the pyrolysis of biomass (biomass degradation under elevated temperature, in the absence of oxygen), where biofuels, bio-oil, biogas, and biochar can be produced [3].  
The dissolution of lignocellulosic and/or extraction of its constituents is an important issue, prior to any further transformations to value-added chemicals. In this paper, we discuss novel, environmentally friendly methods and solvents for effective biomass and biomass constituent dissolution. Ionic liquids and deep eutectic solvents are discussed in detail.