A modified dryer operates on a different principle from that used by the prior torrefaction plants. The subject invention utilizes thermal conduction to torrefy the biomass in a vibratory reactor in which a heated solid unperforated plate is sealed in the reactor to separate the biomass above from the gas used to heat the plate below. This permits using inert flue gas to heat the reactor which in turn permits the use of a cool air damping system to prevent thermal runaway. Also syngas evolved from the process is utilized to power a gas engine, the exhaust output of which is recirculated to heat the reactor plate. When the gas engine is coupled to an electric generator, waste energy is recovered for use in other parts of the plant or exported elsewhere.