Abstract: Separation of a product of digestion of cellulosic biomass solids may be challenging due to the various components contained therein. Methods and systems for processing cellulosic biomass, particularly a reaction product of a hydrothermal reaction containing lignin-derived products, such as phenolics, comprise providing the reaction product of a further processing (such as condensation reaction) to a non-aqueous stream to at least part precipitate the lignin and removing the precipitated lignin.