Abstract: A process for reduced energy consumption while comminuting waste materials includes delivering the materials to a comminuting chamber having a longitudinally extending comminuting zone. A plurality of actuable series of comminuting units are provided and are operable in said chamber. The comminuting units are arranged in series and are successively staggered in an inclined relation adjacent the comminuting zone. Each of the series is successively staggered one behind the other so that the last unit of the first series is positioned for impaction before the first unit of the next succeeding series. The units of the second series are interdigitated for impaction between the units of the first series. The series are successively actuated so that the comminuting units impact certain areas of the waste material by causing the series to successively impact the material so as to avoid simultaneous impaction of immediately adjacent areas of the material.