A model for steam gasification of biomass was developed by applying thermodynamic equilibrium calculations. With this model, the simulation of a decentralized combined heat and power station based on a dual fluidized-bed steam gasifier was carried out. Fuel composition (ultimate analysis and moisture content) and the operating parameters, temperature and amount of gasification agent, were varied over a wide range. Their influences on amount, composition, and heating value of product gas and process efficiencies were evaluated. It was shown that the accuracy of an equilibrium model for the gas composition is sufficient for thermodynamic considerations. Net electric efficiency of about 20% can be expected with a rather simple process. Sensitivity analysis showed that gasification temperature and fuel oxygen content were the most significant parameters determining the chemical efficiency of the gasification. (C) 2001 Elsevier Science Ltd. All rights reserved.