A direct drive material volume reduction apparatus having a frame, a motor supported by the frame, a drum supported by the frame and having an interior and an exterior, a drive shaft operably connected to the motor, a comminuting wheel assembly including a disk like body portion having an axis and a geared axle assembly operably interpositioned between and connected to the drive shaft and the comminuting wheel assembly to operably support the comminuting wheel assembly within the interior of the drum and to transmit the rotational torque of the motor imparted to the drive shaft and transfer it to the comminuter wheel assembly enabling the comminuter wheel to rotate within the interior of the drum. The geared axle assembly is preferably that of a motorized vehicle of the type found in an over-the-road type diesel truck. The drum may include a substantially cylindrical wall with an open first end and an open second end and a closure member to at least partially close the second end of the drum. The closure member may further comprise a grate, or a plurality of grate segments, mounted adjacent the second end of the drum. A hub supported by a distal end of an axle portion wherein the hub is configured to enable the comminuter wheel to be attached to it. At least one toothed bracket is secured to the wheel. A modular cutting system and tooth assembly including a holder portion and tooth element cooperatively configured for frictional interengagement such that the tooth element is rigidly attached to the holder during use and removable. The removable teeth are preferably formed of a unitary body construction wherein the unitary body is rigidly secured to the bracket and preferably also include a supplemental material contact portion.