A one-dimensional steady state model for biomass-steam gasification has been developed. The reactor is a bubbling fluidized bed. With respect to hydrodynamics the model distinguishes two zones namely: dense zone and freeboard zone. The gasification process is modelled in three steps: drying, devolatilization and gasification of biomass char. The model assumes that solids are well mixed while the gases are in plug flow regime. Mass and energy balance is solved globally across the entire gasifier. The gas composition and temperatures predicted by the model for wood chips as fuel agree well with values measured at an 8 MW (fuel power) commercial plant. (C) 2011 Elsevier Ltd. All rights reserved.