Abstract: In a method for physical and thermochemical treatment of biomass, the biomass moisture content is reduced in a dryer and ammonia (NH3) is also released from the biomass during drying. The dried biomass is then either pyrolyzed in a pyrolysis reactor and the pyrolysis gas is forwarded to and combusted in a combustion device to form flue gas, or is combusted in a combustion facility unit to form flue gas. In either case the flue gas is fed to a mixer. Oxygen (O2) is metered to the flue gas in the mixer and is fed directly to the dryer as drying gas. As the drying gas passes through the dryer, the sulfur dioxide (SO2) contained in the drying gas and/or the sulfur trioxide (SO3) chemically reacts with the ammonia (NH3) to form ammonium sulfite ((NH4)2SO3) and/or ammonium sulfate ((NH4)2SO4). Also a treatment facility physically and thermochemically treats the biomass.