Abstract: An improved waste disposer having shredding means in a comminution chamber and a rotor rotatable within the chamber. Freely rotating impellers are provided on the rotor which rotate as the rotor is rotated. Each impeller includes at least one main cutting blade adapted to cooperate with the shredding means to comminute waste in the chamber. Each impeller also includes one or more subsidiary cutting blades for assisting in grinding such waste. The blades on one impeller are mounted in a mirror image relationship to the blades on the other impeller to provide improved comminution of the waste.