## 1 Introduction  
It is essential to find new alternatives to the current energy model based on the use of fossil resources to avoid the environmental problems that the use of these fossil resources entails. In a global scenario characterized by the scarcity of raw materials, lignocellulosic biomass residues are considered a sustainable natural resource for the efficient production of high-value-added products [1; 2] and biofuels [3] and are sustainable within the framework of biorefineries. Integration into a biorefinery strategy will enable an evolution towards an economy based on natural resources, which will replace the current economy based on raw fossil materials [4; 5]. In fact, in the near future, the chemical industry could rely solely on biomass as an alternative source [6; 7], and biorefineries will then be able to compete with fossil fuel resources [4; 8; 9]. However, for effective use of these biomass residues, pretreatments are key to alter the inherent recalcitrance of these residues and improve the reactivity of the biomass for further transformations and to obtain high-value-added products [9; 10; 11; 12; 13]. The composition of the raw materials varies according to the different biomasses presenting different proportions of components. Due to their complex structure, fragmentation is required to achieve a better utilization of the biomass and to improve the porosity of the cellulosic matrix that facilitates chemical hydrolysis [14; 15; 16; 17; 18; 19].  
In previous studies, the dissolution of cellulose and barley straw in ionic liquids (ILs) has been investigated [10; 14; 20; 21; 22; 23]. However, despite being effective in dissolving lignocellulosic biomass and fractionating it into cellulose, hemicellulose, and lignin using selective antisolvents, if a low-priced ionic liquid is not used as solvent [20; 24] or the expensive ionic liquid cannot be recovered, it is essential to find another solvent as an alternative [25; 26; 27; 28].  
Inorganic salt hydrates are an attractive alternative to ILs because they are cheaper, recyclable, non-toxic, and usually require lower temperatures for lignocellulosic biomass dissolution. Hydrated inorganic salt is inserted between the fibers of the lignocellulosic residues, breaking the hydrogen bonds and allowing their dissolution [29; 30; 31; 32]. In a previous study, an inorganic salt hydrate (ZnCl\({}_{2}\cdot\)4H\({}_{2}\)O) was subsequently precipitated by adding water [18]. Salt hydrates can dissolve structural carbohydrates (cellulose and hemicellulose), leaving lignin in the solid [33], so the pretreatment of biomass will consist of partial dissolution of the polymeric carbohydrates of the biomass and its regeneration with water.  
In the present work, three different types of lignocellulosic biomass residues (LB) will be studied, barley straw, pruning waste, and vine shoots, and treated with the inorganic salt hydrate ZnCl\({}_{2}\cdot\)4H\({}_{2}\)O. The treatment yields the fractionation of the biomass. The different solids obtained were analyzed by different characterization techniques and those with structural carbohydrates were tested in acid hydrolysis. The obtained results are compared with the results for untreated lignocellulosic biomass to check the effectiveness of the treatment. To the best of our knowledge, an inorganic salt has never before been used for fractionation of full lignocellulosic biomass.