NOVELTY - Method for processing organic materials for biogas plants with a fermenter comprises: filling the organic material in a mixing tank, which is intended for a fermenter; crushing and mixing the organic materials in the mixing tank with sufficient liquid to form a pumpable substrate and pumping the substrate in the fermenter.    USE - The method, the device and the mixing and cutting tool are useful for processing organic materials for biogas plants (all claimed), where the organic material is chopped corn or other cereals.    ADVANTAGE - The method employs the optimal utilization of raw materials in the biogas plant and improves the performance of the fermenter. The knife chops the coarse portion, of e.g. chopped corn, within short time period of 3-5 minutes. The method provides faster availability of the biogas and high gas volume in less time and due to improved biogas formation, addition of the substrate is reduced after few days.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a device, for processing organic materials, for biogas plants, that are stored in a mixing tank, where the biogas plant works with a fermenter, comprising at least one shaft that extends vertically in the mixing tank and rotated by a drive; a mixing tool that is attached to the shaft and the boundary area and/or surface area of the tool is formed such that both the function of the mixing and that of the chopping of the organic materials results in form i.e. a homogenous, pumpable pulp that is pumped in the fermenter; and    (2) a mixing and cutting tool for fastening at a shaft, for processing the organic materials for biogas plants, operated through a mixer, comprising a disc-shaped base body that is fixable at the shaft, at least one cutter that is arranged in the brim of the base body so that both the function of mixing and that of chopping of the organic materials result in form i.e. a homogenous, pumpable pulp.    DESCRIPTION OF DRAWING(S) - The diagram shows the schematic flow in a biogas plant with a mixer.