NOVELTY - Torrefaction of an optionally pre-dried biomass, comprises: (a) heating the optionally pre-dried biomass in at least one heating zone such that the temperature of the biomass reaches a torrefaction temperature range; and (b) torrefying the heated biomass from step (a) in a torrefaction zone by maintaining the temperature within the torrefaction temperature range.    USE - The method or system is useful for torrefaction of optionally pre-dried biomass (claimed).    ADVANTAGE - The invention provides method and system for efficient torrefaction of biomass. Since the dried and heated biomass is fed into the torrefaction zone at its top and the torrefied material is withdrawn from the torrefaction zone at its bottom, no moveable parts are needed in the torrefaction zone. Instead, the material moves through the torrefaction zone by gravity. This provides for a simple and thus cheap construction. Furthermore, such a construction provides for an energy-efficient torrefaction process: no heating means are needed at the torrefaction zone. It is sufficient that the torrefaction zone is insulated such that the temperature range reached during the heating step is maintained.    DETAILED DESCRIPTION - Torrefaction of an optionally pre-dried biomass, comprises: (a) heating the optionally pre-dried biomass in at least one heating zone such that the temperature of the biomass reaches a torrefaction temperature range; and (b) torrefying the heated biomass from step (a) in a torrefaction zone by maintaining the temperature within the torrefaction temperature range, where the heated biomass from step (a) is fed to the torrefaction zone at its top and torrefied material is withdrawn from the torrefaction zone at its bottom, such that the biomass moves downwards through the torrefaction zone by gravity, and where an oxygen-containing gas is supplied to the torrefaction zone. An INDEPENDENT CLAIM is a system for torrefaction of biomass, comprising a first zone for heating of an optionally pre-dried biomass; and an insulated second zone for torrefying the heated biomass, the second zone having an inlet being connected to an outlet of the first zone, means for withdrawing torrefied biomass arranged at the bottom of the second zone, such that the biomass can move downwards through the second zone by gravity, where means for heating are arranged at the first zone, but not at the second zone.