Hydrothermal digestion of cellulosic biomass solids may be conducted such that a glycol reaction product is formed for subsequent processing. Processing of a glycol reaction product may include a drying operation conducted prior to condensation of the glycol reaction product into higher molecular weight compounds. Methods for digesting cellulosic biomass solids to form a glycol reaction product can comprise: providing cellulosic biomass solids and a slurry catalyst in a hydrothermal digestion unit, the slurry catalyst being capable of activating molecular hydrogen; heating the cellulosic biomass solids in the hydrothermal digestion unit in the presence of the slurry catalyst, a digestion solvent, and molecular hydrogen, thereby forming a liquor phase comprising soluble carbohydrates; and performing a first catalytic reduction reaction on the soluble carbohydrates within the hydrothermal digestion unit, thereby at least partially converting the soluble carbohydrates into a reaction product comprising a glycol.