Digestion of cellulosic biomass solids can be enhanced in the presence of a phenolic solvent. Methods for digesting cellulosic biomass solids can comprise providing cellulosic biomass solids in a digestion medium comprising water and an organic solvent; heating the cellulosic biomass solids and the digestion medium in a digestion unit in the presence of molecular hydrogen and a slurry catalyst capable of activating molecular hydrogen, thereby forming an alcoholic component and liberating lignin, the lignin forming a phenolics liquid phase partitioned from the digestion medium and at least a portion of the slurry catalyst accumulating in the phenolics liquid phase; removing at least a portion of the phenolics liquid phase and accumulated slurry catalyst from the digestion unit; converting at least a portion of the phenolics liquid phase into a phenolic solvent; and returning at least a portion of the phenolic solvent and the slurry catalyst to the digestion unit.