Abstract: A rotary friction dryer or gasifier and a method of using the same is provided. The rotary friction dryer generally comprises an entrance stage, an exit stage, a decompression zone located such that it separates the entrance and exit stages, a multi-stage compression screw, a mixing means coupled to the screw, at least one exhaust vent located in the decompression zone, and at least one discharge outlet located in the exit stage. The entrance stage includes an intake throat and the temperature of each stage (entrance and exit) is controllable.