A torrefaction reactor includes a preheater section and a torrefaction section arranged to receive the biomass material from the preheater section. The preheater section includes a plurality of preheater plates arranged to facilitate the flow of the biomass material between the preheater plates by the force of gravity, each of the preheater plates facilitates a flow of a preheater fluid through the preheater plate for heating the biomass material. The torrefaction section includes a plurality of torrefaction plates arranged to facilitate the flow of the biomass material between the torrefaction plates by the force of gravity, each the torrefaction plates facilitates a flow of a torrefaction fluid through the torrefaction plate for heating the biomass material to the torrefaction temperature, and a first and second torrefaction purge gas openings to facilitate a flow of a torrefaction purge gas for providing an oxygen-depleted environment within the torrefaction section.