A method and apparatus for an anaerobic digestion of biomasses with generation of biogas and sludge, wherein a hydrolyzation phase and a following fermentation of the biomass are included, wherein a hydrolyzation phase (5) and at least two following fermentation phases (7,8,9) are included and wherein the hydrolyzation (5) as well as the following fermentations (7,8,9) are performed in separate containers with specific measurement and control of the temperature, of the mixing degree, of the pH value and of the pressure.