The present paper develops a simple but rigorous trigeneration plant model for designing, optimizing and simulating small-medium scale plants including a realistic biomass gasification model. The model provides five different configurations for the simultaneous production of heating, cooling and electricity. It includes modeled components as a gasifier, an internal combustion engine and different kinds of absorption chiller (single- and double-effect) modeled using the characteristic equation approach method. The model enables the outputs of the plant to be evaluated and calculated for different types of biomass, operating conditions and configurations. It has been applied in the case study of the ST-2 polygeneration plant to be built in Cerdanyola del Valles (Barcelona, Spain). The results demonstrate that it is a useful tool for assessing the performance of trigeneration plants using several types of biomass and enables meaningful comparisons to be made between configurations for real applications. (C) 2013 Elsevier Ltd. All rights reserved.