NOVELTY - Producing alcohol and/or solvent from a biomass feedstock, comprises (a) performing pretreatment step by contacting and heating the feedstock with water (W1, W2) and an acidic/basic compound (A), (b) contacting the pretreated substrate with cellulase enzymes and with a liquid stream enriched in fermentation products, (c) performing alcoholic fermentation of hydrolyzate using an alcohol microorganism, (d) extracting the solid material contained in the fermentation wine, (e) washing the stream enriched in solid material with a liquid stream, and (f) performing a separation step.    USE - The method is useful for producing alcohol e.g. ethanol and/or solvent from a biomass feedstock including wood, cultivated plants, agricultural lignocellulosic waste and residues of lignocellulosic materials processing industry (all claimed).    ADVANTAGE - The method ensures economical production of alcohol and solvent in an industrial scale with increased yield and without loss of fermentation product.    DETAILED DESCRIPTION - Producing alcohol and/or solvent from a biomass feedstock, comprises (a) performing pretreatment step by contacting and heating the biomass feedstock with water (W1, W2) and an acidic or basic compound (A) to obtain a pretreated substrate, (b) contacting the pretreated substrate with cellulase enzymes and with a liquid stream enriched in fermentation products to obtain a hydrolyzate comprising a solid residue and a liquid phase containing sugars, (c) performing alcoholic fermentation of hydrolyzate using an alcohol microorganism to produce fermentation wine comprising a solid material and a liquid phase containing fermentation products, (d) extracting a part of the solid material contained in the fermentation wine so as to obtain a stream enriched in solid material and wine, (e) washing the stream enriched in solid material with a liquid stream to obtain a liquid stream enriched in fermentation products, and (f) performing a separation step of fermentation wine depleted of solid to obtain at least one purified stream comprising an alcohol or a solvent and at least one vinasse stream.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a method for producing alcohol and/or solvent from a biomass feedstock.    Acidic or basic compound (A)    Mixture of biomass (C)    Reactor unit (H1)    Pretreatment unit (P)    Water. (W1, W2)