TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The cellulase enzymes are produced by a microorganism comprising fungi belonging to genus Trichoderma, Aspergillus, Penicillium or Schizophyllum, and anaerobic bacteria belonging to the genus Clostridium. The microorganism used in step (e) comprises Saccharomyces, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Saccharomyces uvarum, Saccharomyces diastaticus, Kluyveromyces fragilis, Candida shehatae, Pichia stipitis, Pachysolen tannophilus, Zymomonas mobilis, Clostridium, and Escherichia coli.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: Before performing the step (b), the wash liquid stream obtained in step (d) is subjected to a second alcoholic fermentation step using an organism. The second alcoholic fermentation step is carried out under operating conditions different from the operating conditions of the alcoholic fermentation of the step (e). The step (d) comprises contacting the enriched solid material stream with the liquid stream and then separating the liquid stream from the solid material. In the step (a), the steam explosion of biomass is carried out by compressing and then performing relaxation of the biomass with mixture of water and an acid compound. Preferred Components: The liquid stream in step (d) comprises: fresh water; and at least a portion of the stillage stream obtained in step (f). The wash liquid stream has a flow rate of 50-1500 wt.%. The solid material enriched stream comprises 15-55 wt.% of solid material. The solid material depleted hydrolyzate comprises less than 15 wt.% of solid material. The biomass feedstock comprises at least one of wood, crops, agricultural lignocellulosic wastes, and residues from lignocellulosic materials processing industry. EXAMPLE - Straw was milled into 50 mm particles and then impregnated with 0.7 g/l of diluted sulfuric acid. The solid/liquid separation process was performed and the impregnation liquor was recycled. The pretreatment with steam explosion was carried out at 200 degrees C in a continuous configuration using a short residence time. The pretreated substrate was sent to the enzymatic hydrolysis reactor. The solid concentration at the inlet of the enzymatic hydrolysis reactor unit was 14%. The water was mixed to the pretreated substrate. The enzymatic hydrolysis reaction was performed in the reactor. The solid material was separated. The clarified liquid was sent to the fermentation unit. The microorganism such as Saccharomyces cerevisiae was added to the fermentation unit. The fermentation reaction was performed in the fermentation unit to produce ethanol.