METHOD FOR PRODUCING ALCOHOLS AND/OR SOLVENTS FROM LIGNOCELLULOSIC BIOMASS WITH ACID RECYCLING OF SOLID RESIDUES

The present invention describes a process for the production of alcohols and/or solvents from a cellulosic or lignocellulosic substrate, comprising at least the following steps: a step A for alkaline pre-treatment of said substrate, comprising a step for heating in the presence of an alkaline chemical reagent and an optional washing step; a step B constituted by a step for adjusting the pH and a step for enzymatic hydrolysis of the pre-treated substrate, at the end of which a hydrolysate is obtained constituted by a liquid phase containing sugars and a solid residue; a step for alcoholic fermentation of the hydrolysate obtained; a step for separation/purification (step C2) at the end of which one or more purified alcohols and/or solvents are obtained; a step for extracting the solid residue; a step D for acid digestion of at least a fraction of the extracted solid residue, at the end of which a portion or all of the product obtained is recycled to step B.