Abstract: The present invention relates, to a device for conditioning as granules a composition formulated from organic and mineral raw materials, characterized in that it comprises a rotary tank with a hyperbolic or exponential wall receiving the bulk raw materials in the upper portion, at least one set of blades ensuring the mixing and milling of said materials inside the tank and a helical groove borne by the wall of said tank and ensuring together delivery by centrifugation and guiding of the mixture from the low portion of the tank to its upper portion and gradual agglomeration of said materials in granules, on the one hand and, to a method for conditioning said composition by means of said device, on the other hand.