Abstract: Apparatus for high-efficiency drying of material includes a vacuum drying chamber (40) maintained at a low pressure by a vacuum pump (56). Material to be dried is introduced to the drying chamber through an air lock valve (36) and is transported through the drying chamber by an auger (45). In the preferred embodiment a second interconnected drying chamber (50) includes a further auger (52), and material that has been dried is removed from the drying chamber by another air lock valve (55). Microwave energy sources (30) apply energy to vaporize liquid from the material, and air inlets (72, 73) are provided at the processed ends to introduce air for sweeping generally across the material to the outlet (55) to the vacuum pump. The sweep of cool air causes an aerosol mixture to form, which is removed by the vacuum pump.