A mathematical model describing a gasification process composed of a dryer section and of a gasification section is presented in this work. This model is based on the equilibrium assumption within both sections. The whole set of assumptions used in the model are presented in the paper as well as the derivation of the corresponding equations. The temperature of both sections is computed using energy balances. The numerical predictions of the model are compared to available data describing the gasification of coal, wood and grass. The influence of two operating parameters of the system is investigated in the study. The first one is the ratio of air supplied to the dryer to the biomass fed to this section. Our computation clearly shows the existence of an optimal value for this parameter. In the same manner, the influence of the ratio of air supplied to the gasifying section to the incoming biomass is investigated. Once again, this parameter shows an optimal value. (C) 2010 Elsevier Ltd. All rights reserved.