NOVELTY - The device for extraction of granular materials from a tank (1), comprises a support grid (5) in its lower part mounted on a movable framework in connection with a fixed framework (3), and a destruction organ of vaulted base (8) to scavenge the surface of the grid positioned below the tank. The support grid is vertically moved in to and fro manner. The destruction organ is a flat bar equipped with a bevel on each of its perpendicular side to direction of displacement, a tight cable and a grid having a mesh higher than the support grid, and comprises a rest position.    USE - The device is useful for extraction of granular materials from a tank, and in a composter of organic wastes (claimed).    ADVANTAGE - The device is simple and easy to install and implement, ensures effective and complete extraction of granular materials from the tank, can able to position the material on the support grid and allows a free penetration of the destructive organ of vaulted base when the material is too compact, and avoids the destruction in the improved flow of the material.    DETAILED DESCRIPTION - The device for extraction of granular materials from a tank (1), comprises a support grid (5) in its lower part mounted on a movable framework in connection with a fixed framework (3), and a destruction organ of vaulted base (8) to scavenge the surface of the grid positioned below the tank. The support grid is vertically moved in to and fro manner. The destruction organ is a flat bar equipped with a bevel on each of its perpendicular side to direction of displacement, a tight cable and a grid having a mesh higher than the support grid, and comprises a rest position apart from a zone covered by the tank. The destruction organ is transversely moved according to its direction of principal displacement, and remains in a plane parallel to the support grid. An INDEPENDENT CLAIM is included for a composter of organic wastes.    DESCRIPTION OF DRAWING(S) - The figure shows a front view of a composter.    Tank (1)    Cover (2)    Fixed framework (3)    Support grid (5)    Vaulted base. (8)