NOVELTY - Producing ethanol from biomass, comprises (a) pretreating the biomass in a pretreatment reactor (4) by steam explosion, (b) performing an enzymatic hydrolysis of a pre-treated substrate contained in the effluent in the presence of cellulolytic and/or hemicellulolytic enzymes, (c) performing an alcoholic fermentation of solubilized sugars contained in hydrolyzate in the presence of alcohol-producing microorganism, (d) performing extraction of ethanol from fermented effluent, and (e) recycling, upstream of or in the reactor, aqueous internal flow containing ethanol.    USE - The method is useful for producing ethanol from biomass (claimed) such as lignocellulosic biomass (such as hardwood and softwood) obtained from food industries and paper mills.    ADVANTAGE - The method ensures efficient and economical production of ethanol from biomass with high yield (99%) and without formation of degradation products.    DETAILED DESCRIPTION - Producing ethanol from biomass, comprises (a) pretreating the biomass in a pretreatment reactor (4) by steam explosion so as to provide an effluent containing a pre-treated substrate, (b) performing an enzymatic hydrolysis of the pre-treated substrate contained in the effluent in the presence of cellulolytic and/or hemicellulolytic enzymes so as to produce hydrolyzate containing the solubilized sugars, (c) performing an ethyl fermentation of solubilized sugars contained in hydrolyzate in the presence of alcohol-producing microorganism so as to produce a fermented effluent containing the ethanol, (d) performing extraction of ethanol from the fermented effluent, and (e) recycling, upstream of or in the pre-treatment reactor, at least one aqueous internal flow comprising at least one ethanol so as to recover the output of a vapor effluent containing ethanol in the pre-treatment reactor.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a process for producing ethanol.    Conduit (1)    Charge preparation unit (2)    Line (3)    Pretreating reactor (4)    Extraction/purification unit. (12)