Method for producing ethanol using cellulosic biomass as raw material

A method for producing ethanol using cellulosic biomass as a raw material, the method comprising:

• a first hydrolytic saccharification step of hydrothermally treating a slurry of cellulosic biomass whose solid concentration is 1% by mass or higher but 5% by mass or lower at a temperature of 140° C. or higher but 200° C. or lower and a pressure of 1 MPa or higher but 5 MPa or lower to saccharify/decompose hemicellulose contained in the cellulosic biomass into C5 sugars;
• a first solid-liquid separation step of subjecting the slurry after the first hydrolytic saccharification step to solid-liquid separation;
• a reslurrying step of adding water to a dewatered cake obtained in the first solid-liquid separation step to prepare a slurry having a solid concentration of 1% by mass or higher but 5% by mass or lower;
• a second hydrolytic saccharification step of hydrothermally treating the slurry obtained in the reslurrying step at a temperature of 240° C. or higher but 300° C. or lower and a pressure of 4 MPa or higher but 10 MPa or lower to saccharify/decompose cellulose contained in the cellulosic biomass into C6 sugars;
• a second solid-liquid separation step of subjecting the slurry after the second hydrolytic saccharification step to solid-liquid separation;
• a concentration step of concentrating a C5 saccharified solution obtained in the first solid-liquid separation step and a C6 saccharified solution obtained in the second solid-liquid separation step so that the concentration of sugars is 10% by mass or higher;
• a fermentation step of subjecting a concentrated saccharified solution after the concentration step to alcoholic fermentation;
• and
• a distillation step of distilling a fermented liquid obtained in the fermentation step to concentrate ethanol.