The present invention relates to a method and system for torrefaction of biomass and combustion of generated torrefaction gases. The torrefaction gases released from the biomass during the torrefaction reaction are withdrawn from the reactor and into a first burning zone. A secondary stream of air is introduced to the first burning zone to combust the torrefaction gases whereupon hot flue gases are obtained. Part of the hot flue gases are directed to a mixing unit. The rest of the hot flue gas is directed to a second burning zone for complete combustion of the flue gases. The fully combusted flue gases obtained in the second burning zone are directed to a heat recovery unit where the temperature of the flue gas is decreased. Part of the cold flue gases are directed to the mixing unit where it is mixed with the hot flue gases such that a stream of cooled flue gases is obtained. The stream of the cooled flue gases are diverted into the torrefaction reactor for direct heating of the biomass.