NOVELTY - A pre-hydrolysis liquid which arises in pulp manufacture is processed by carrying out ethanol fermentation of pre-hydrolysis liquid which arises according to pre-hydrolysis of timber in case of pulp manufacture, obtaining bioethanol and process liquid, and acid-treating the process liquid after ethanol fermentation and taking out furfural.    USE - Processing of pre-hydrolysis liquid which arises in pulp manufacture used for manufacturing bioethanol, furfural and methane gas (all claimed).    ADVANTAGE - Pre-hydrolysis liquid which cannot be discharged in environment can be processed stably, and chemical oxygen demand (COD) can be reduced.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) manufacture of bioethanol from pre-hydrolysis liquid which arises from pulp manufacture which involves carrying out ethanol fermentation of pre-hydrolysis liquid which arises according to pre-hydrolysis of timber in pulp manufacture, obtaining bioethanol and process liquid, acid-treating the process liquid after ethanol fermentation, taking out furfural, and methane-fermenting the process liquid and obtaining methane gas and methane fermentation drainage liquid;    (2) manufacture of furfural from pre-hydrolysis liquid which arises in pulp manufacture which involves carrying out ethanol fermentation of pre-hydrolysis liquid which arises according to pre-hydrolysis of timber in pulp manufacture, obtaining bioethanol and process liquid, acid-treating the process liquid after ethanol fermentation, taking out furfural, methane-fermenting the process liquid and obtaining methane gas and methane fermentation drainage liquid; and    (3) manufacture of methane gas from pre-hydrolysis liquid which arises in pulp manufacture which involves carrying out ethanol fermentation of pre-hydrolysis liquid which arises according to pre-hydrolysis of timber in pulp manufacture, obtaining bioethanol and process liquid, acid-treating the process liquid after ethanol fermentation, taking out furfural, methane-fermenting the process liquid and obtaining methane gas and methane fermentation drainage liquid.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the processing system of prehydrolysis liquid. (Drawing includes non-English language text).