Abstract: An apparatus and method for sterilizing and/or dehydrating organic materials. The apparatus comprises a microwave chamber, at least one microwave generator for irradiating material within the drum, and a vacuum system coupled to the microwave chamber to evacuate the microwave chamber to a desired pressure below atmospheric pressure. In one embodiment the microwave chamber contains a microwave-permeable rotatable drum having an access opening and a helical vane disposed along an inner wall of the drum, the vane being oriented so that when the drum is rotating in a loading direction the material is tossed and driven away from the access opening, and upon a reversal of the rotation of the drum to an unloading direction, the material is driven toward the access opening to be discharged from the drum.