Abstract: A method and apparatus for reducing material, such as trash, refuse, garbage and the like, to a specified size of particles. The apparatus is directed to a single comminuting chamber means as well as to a combination of first and second comminuting chamber means. The first comminuting chamber means includes in the lower portion of said chamber means a flow passage means of varying volume through which the particles pass thereby preventing wedging or packing of the particles in the first comminuting chamber means during the comminution of the material therein. The second comminuting chamber means includes a screenless hammer mill means having holding bars or means for holding pieces of material that exceed a predetermined length until said pieces are reduced to a length equal to or less than said predetermined length.