NOVELTY - Processing lignocellulosic biomass comprises: contacting a lignocellulosic biomass with acetic acid; heating the contacted biomass; separating lignocellulosic cake from obtained hydrolyzate liquid; contacting the lignocellulose cake with acetic acid and then 1-2C acid-miscible organic solvent to recover liquid separate; combining the liquid with at least one of hydrolyzate and acid wash liquid; and condensing obtained extract to form a concentrated hemicellulose and lignin aqueous phase, and then adding 1-2C acid-miscible organic solvent.    USE - The method is useful for processing lignocellulosic biomass (claimed) for producing sugar syrups and lignin fractions.    ADVANTAGE - The cost-effective method is capable of processing lignocellulosic biomass to recovery sugar syrups without any toxic byproducts, thus reducing the quantity of water and solvent used.    DETAILED DESCRIPTION - Processing lignocellulosic biomass comprises: (a) contacting a lignocellulosic biomass with a first amount of acetic acid; (b) heating the contacted lignocellulosic biomass to a temperature and for a time sufficient to hydrolytically release a first portion of hemicellulose and lignin, thus forming a hydrolyzate liquid and an acylated lignocellulose cake; (c) separating the acylated lignocellulosic cake from the hydrolyzate liquid; (d) contacting the acylated lignocellulose cake with a second amount of the acetic acid to wash hemicellulose and lignin from the acylated lignocellulosic cake and separating an acid wash liquid from the acid washed acylated lignocellulosic cake; (e) contacting the acid washed acylated lignocellulose cake with a first amount of 1-2C acid-miscible organic solvent to wash the acetic acid, hemicellulose and lignin from the acid washed acylated lignocellulosic cake to recover 1-2C acid-miscible solvent wash liquid separate from the solvent washed acylated lignocellulose cake; (f) combining the solvent wash liquid with at least one of the hydrolyzate and the acid wash liquid to form an acidic organic solvent extract; (g) condensing the acidic organic solvent extract to form a concentrated hemicellulose and lignin aqueous phase enriched with hemicellulose and lignin; and (h) adding to the concentrated hemicellulose and lignin aqueous phase, a second amount of 1-2C acid-miscible organic solvent sufficient to induce phase partitioning into a first phase comprising a washed heavy aqueous phase enriched in 5C and 6C sugars and organic-insoluble lignin and a second phase comprising an organic supernatant phase comprising organic-soluble lignin, acetate salts, 1-2C acid-miscible solvent, and acetic acid. INDEPENDENT CLAIMS are included for:    (1) a composition comprising an organic-insoluble lignin obtained by the method; and    (2) a composition comprising acetate salts obtained from cellulosic biomass, where the acetate salts are suitable for fertilizer.