NOVELTY - The method for the conversion of biomass to a biogas in anaerobic fermenters useful in a biogas production plant, comprises introducing renewable raw materials with liquid and further necessary base materials into a first anaerobic fermenter for the methanogenesis and then subjecting to a fermentation process and to a solid-liquid separation process, which is carried out by pressing, centrifugating or sieving. The separated solid phase is subjected to a thermal pressure hydrolysis at a temperature of 170-250 degrees C and a pressure of 1-4 MPa.    USE - Method for the conversion of biomass to a biogas in anaerobic fermenters useful in a biogas production plant.    ADVANTAGE - The method ensures effective and economical conversion of the biomass to the biogas with high quantity and quality, high operational stability, high flexibility and less energy consumption in less time-consuming manner.    DETAILED DESCRIPTION - The method for the conversion of biomass to a biogas in anaerobic fermenters useful in a biogas production plant, comprises introducing renewable raw materials with liquid and further necessary base materials into a first anaerobic fermenter for the methanogenesis and then subjecting to a fermentation process and to a solid-liquid separation process, which is carried out by pressing, centrifugating or sieving. The separated solid phase is subjected to a thermal pressure hydrolysis at 170-250 degrees C and a pressure of 1-4 MPa. The treated solid phase is reconducted into the first anaerobic fermenter or supplied to a second anaerobic fermenter and then subjected to a further fermentation process. Liquid manure, sludge and/or process water are added as the base materials. The thermal pressure hydrolysis is carried out by mechanical processing-step or by chemical and/or enzymatic processing-step of the solid phase before or during the thermal pressure hydrolysis. The solid-phase is supplied to the second anaerobic fermenter after the thermal pressure hydrolysis. The second anaerobic fermenter supplies a portion of liquid phase after the solid-liquid phase separation. The thermal pressure hydrolysis is carried out by using the waste heat of other processes.    DESCRIPTION OF DRAWING(S) - The diagram shows a process scheme with two fermenters (Drawing includes non-English language text).