Pressurized gas produced from biomass is a renewable resource that is an a great cleat of attention due to its wide range of industrial applications, such as the production of hydrogen, chemicals or high grade fuels. Therefore, the Vienna University of Technology in cooperation with BioEnergy 2020+ is operating a bubbling pressurized gasification plant. The pressurized research unit (PRU) is able to perform the gasification of wood chips, wood pellets, coal and other solid fuels with gasification agents air, steam, oxygen or carbon dioxide. This paper gives the results of parameter variation at this plant with regard to he producer gas composition. The feedstock was wood pellets and as bed material olivine was used with an average particle size of 0.5 mm. The parameters varied were temperature (720-900 degrees C), pressure (1-5 bar), air ratio (0.2-0.4), gasification agent (air, steam, oxygen). biomass feed input (4.5-8 kg/h) and the fluidization conditions of the reactor fluidized bed (fluidization number (3-7)). (c) 2010 Elsevier B.V. All rights reserved.