TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The crops expressly cultivated for energy use are Miscanthus, foxtail millet or common cane. The process is carried out at: a temperature of 160-230 degrees C, preferably 180-210 degrees C; and a reaction time of 1-8 hours. The product is subjected to separation to remove the solid lignin phase, then evaporated until a biphasic system is formed, consisting of an alcohol phase containing the concentrated acid catalyst, which is recycled, and a second organic phase comprising the ester of levulinic acid. Preferred Components: At least one polysaccharide contained in the biomass comprises hexose saccharide units. The polysaccharides comprise hexose saccharide units, which are cellulose, hemicellulose, and/or starch. The biomass is a lignin-cellulose biomass. The lignin-cellulose biomass is products of crops expressly cultivated for energy use, including waste products, residues and scraps of the crops or their processing, products of agricultural and forest cultivations, comprising wood, plants, residues and waste products of agricultural processing and forestry, waste of agro-food products destined for human nutrition or zootechnics, residues, not treated chemically, of the paper industry, waste products coming from the differentiated collection of solid urban waste e.g. urban waste of a vegetable origin, paper. The organic acid is an alkylsulfonic or arylsulfonic acid. The acid is 2-naphthalenesulfonic acid (preferred), 1-naphthalenesulfonic acid, or 1,5-naphthalenedisulfonic acid. The organic acid catalyst is used in a concentration of 0.1-5 wt.% with respect to the weight of the alcohol solution consisting of the alcohol and organic acid. The concentration of the acid is 0.5-2 wt.% with respect to the weight of the alcohol solution consisting of the alcohol and organic acid. The concentration of the biomass is 5-30 wt.%, preferably 10-20 wt.%, with respect to the total weight of the reaction mixture.R = aliphatic chain, preferably ethyl, isopropyl, or n-butyl. EXAMPLE - Ground coniferous wood (10 g) was added to a solution of 2-naphthalenesulfonic acid (2 g) in ethanol (100 ml). The mixture was kept under stirring in an autoclave at 200 degrees C for 4 hours. After cooling, the solid phase was separated by filtration and dried to obtain lignin (2.5 g). The solution in ethanol was evaporated at reduced pressure until a biphasic system was formed, consisting of an alcohol phase (5 ml) containing 2-naphthalenesulfonic acid and a second organic phase (6 ml) containing ethyl levulinate. After the separation, the phase containing the acid catalyst was recycled in a subsequent alcoholysis cycle. The phase containing the ester of levulinic acid was distilled at reduced pressure to give ethanol and ethyl levulinate (97 %).