TECHNOLOGY FOCUS - BIOLOGY - Preferred Method: The aerobic hydrolysis step is inoculated by microorganisms in a continuous or discontinuous manner using an inoculum comprising: strains of aerobic bacteria and/or yeasts; a carbon and nitrogen substrate comprising preferably carbohydrates and amino acids; mineral salts optionally containing growth factors of bacteria and/or yeasts or in low concentration in the organic material to be treated. The inoculated aerobic hydrolysis step: is carried out on organic material rectified by supplying specific carbonaceous constituents; comprises supplying of enzymes obtained from fermentation preferably lipid, protein and sugar enzymes; requires a carbon/nitrogen ratio of 15-40, preferably 20-30; and is performed at a temperature of 25-40 degrees C, preferably 30-37 degrees C and at a pH of 6.5-7. The pH of acidogenesis-acetogenesis step is controlled by adding acid, preferably orthophosphoric acid. The acidogenesis-acetogenesis step: comprises controlling the formed acetic acid and formic acid; maintains a high concentration of active anaerobic bacteria and/or yeasts by bio-fixation on the periphery of the acidogenesis-acetogenesis digester; and takes place at a pH of 6.5-8 and at a temperature of 40-50 degrees C. The surfactant is added to the acidogenesis-acetogenesis step. The pH is maintained throughout the methanogenesis step is 7-7.5. The methanogenesis step is performed at a temperature of 30-55 degrees C. The methanogenesis step: takes place in a redox potential controlled at a level of 300 to -330 mV; and maintains a high concentration of active anaerobic bacteria and/or yeasts by biofixing at the periphery of the methanogenesis digester. The concentrate obtained from the methanogenesis is separated from liquid effluents then partly recycled in methanogenesis step. The homogeneity and the mixing of organic material during methanogenesis step are operated by a biogas recirculation system. Preferred Components: The aerobic microorganisms are bacteria and/or yeasts for nitrification and hydrolytic bacteria and/or yeasts. The specific carbonaceous constituents are amino acids, yeast extracts and/or vitamins. The organic material entering in the aerobic hydrolysis phase has a dryness of 12-40 wt.%, preferably 18-22 wt.% of humidity.