Waste comminuting apparatus

A grass mowing machine having grass collection means and comminuting apparatus mounted on the machine such that grass clippings may be fed to the comminuting apparatus, said apparatus comprising an elongate cylindrical barrel, an extrusion screw mounted for rotation within said barrel, means for rotating said screw within said barrel, inlet opening means at one end of said barrel through which grass clippings to be comminuted may be presented to the extrusion screw, and means for closing the other end of said barrel having openings through which comminuted material is forced by said extrusion screw, said extrusion screw having a generally helical flight extending from one end of the screw to the other and having a substantially constant pitch and a flight depth which reduces towards the closed end of the barrel whereby the material to be comminuted is increasingly compressed and comminuted, said extrusion screw also having a shaped end portion housed within said closed end of said barrel, said shaped end portion and said closed end of said barrel being shaped to provide a space therebetween;

• and recirculation means for recirculating partly comminuted material into said space, said recirulating means comprising edge means formed in said end portion of said extrusion screw at an acute angle to the longitudinal axis of said screw.