NOVELTY - Biomass or waste material treatment comprises heating a material that contains residual moisture in a torrefaction reactor (10) to a torrefying temperature in a low-oxygen atmosphere. The reactor comprises a drying chamber (54) and a torrefying chamber (55). The drying of the material in the drying chamber is carried out by introducing into it a hot drying gas. The torrefaction of the material in the torrefying chamber is carried out by introducing into it a hot torrefying gas that flows in counter-current to the material.    USE - Used for the treatment of biomass or waste material.    ADVANTAGE - A relatively small amount of energy needs to be introduced into the torrefying chamber, allowing an improved dosing and/or fine tuning of energy input, thus the torrefying temperature in the torrefying chamber can be set and controlled accurately.    DETAILED DESCRIPTION - Biomass or waste material treatment comprises heating the material that contains residual moisture in a torrefaction reactor to a torrefying temperature in a low-oxygen atmosphere, where the material is converted into a torrefied material. The torrefaction reactor comprises a drying chamber and a torrefying chamber. The material is fully dried in the drying chamber by evaporation of the residual moisture. The torrefaction of the dried material is carried out in the torrefying chamber. The material is conveyed through the torrefaction reactor in a transport direction. The drying of the material in the drying chamber is carried out by introducing into it a hot drying gas that flows through the drying chamber in co-current flow with the material. The torrefaction of the material in the torrefying chamber is carried out by introducing into it a hot torrefying gas that flows in counter-current flow to the material.    An INDEPENDENT CLAIM is included for a device for treating a material comprising a torrefaction reactor having an inlet (11), a heater, an air-treating mechanism for creating a low-oxygen atmosphere in the torrefaction reactor where the material can be converted into torrefied material during operation, and an outlet (13) for removing torrefied material.    DESCRIPTION OF DRAWING(S) - The figure shows a cross section of the torrefaction reactor.    Torrefaction reactor (10)    Inlet (11)    Outlet (13)    Drying chamber (54)    Torrefying chamber (55)