Abstract: Offal material, such as shrimp or crab shells, fish offal, etc, is dried to produce a fine-grained base material or additive for use in foodstuffs and animal fodder by subjecting a starting material in a chamber to a turbulent air current which accelerates the material lumps into various paths of movement. Hereby the material lumps continuously collide with each other, thereby constantly exposing new surfaces or rupture. The chamber is supplied with air, having a temperature which partly depends on the temperature of the starting material and partly depends on the comminution rate, in an amount adjusted according to the amount of starting material introduced per time unit. Hereby it is achieved that free water is immediately removed from the exposed surfaces of rupture by evaporation. By exerting a counter-pressure, the material is retained in the chamber until a desired particle size has been achieved.