The thermodynamic study of beech wood gasification was performed in a pilot scaled flu-idized bed reactor at different operation conditions, including temperature range from 600 degrees C to 900 degrees C, using CO2 and steam as gasification agents and sand and biochar as bed materials. The particularity of this study was the evaluation of energy consumption of biomass gasifier based on energy balance comparison in the same experimental set-up for different experimental conditions. The comparison between pyrolysis and gasification with CO2 showed that pyrolysis required less heat input (4.4 and 5.0MJ/kg(biomass)) than gasification (6.7 and 7.8 MJ/kg(biomass)) at 800 and 900 degrees C respectively. Meanwhile the syngas CGE were higher for gasification (0.78) as the LHV values for syngas (12.2 MJ/kg). Temperature favoured CGE and syngas LHV increase, as it also increased process endothermicity. The presence of biochar as bed material increased the syngas LHV from 3.3 to 15.4 MJ/kg for CO2 gasification and from 3.3 to 15.1 MJ/kg for steam gasification. Both gasification agents provided similar values of CGE (>0.95) at 900 degrees C. From 600 to 900 degrees C the required heat input for steam gasification it was from 1.5 to 6.9 MJ/kg(biomass), meanwhile for CO2 gasification was from 4.1 to 7.1 MJ/kg(biomass). The results offer useful details that can help for future design of gasification experiments in fluidized bed reactors. (c) 2020 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.