An apparatus (20) for dehydrating organic material in batches has a processing unit (22) having a microwave-vacuum chamber (34), an input module (28) and an output module (30), with a conveyor (54) for moving the material through the chamber on a microwave-transparent window. A material reservoir (68) is arranged to receive the material exiting the output module. A conveyor (78) external to the vacuum chamber conveys material that exits the reservoir to the input module. The vacuum chamber (34), reservoir (68) and external conveyor (78) are in fluid communication to operate at a common, reduced pressure. The organic material passes through the vacuum chamber multiple times to equilibrate and dry to the desired degree.
