Polystyrene (PS) pyrolysis and gasification have been examined in a semi-batch reactor at temperatures of 700, 800 and 900 degrees C. Characteristic differences between pyrolysis and gasification of polystyrene (PS) have been evaluated with specific performance focus on the evolution of syngas flow rate, evolution of hydrogen flow rate, evolution of output power, syngas yield, hydrogen yield, energy yield, apparent thermal efficiency and syngas quality. Behavior of PS under either pyrolysis or gasification processes is compared to that of char based sample, such as paper and cardboard. In contrast to char based materials, PS gasification yielded less syngas, hydrogen and energy than pyrolysis at 700 degrees C. However, the gasification of PS yielded more syngas, hydrogen and energy than pyrolysis at 900 degrees C temperature. Gasification of PS is affected by reactor temperature more than PS pyrolysis. Syngas, hydrogen and energy yield increased exponentially with temperature in case of gasification. However, syngas and energy yield increased linearly with temperature having rather a mild slope in the case of pyrolysis. Pyrolysis resulted in higher syngas quality at all temperatures. Kinetics of hydrogen evolution from the PS pyrolysis is introduced. The Coats and Redfern method was used to determine the kinetic parameters, activation energy (E(act)), pre-exponential factor (A) and reaction order (n). The model used is the nth order chemical reaction model. Kinetic parameters have been determined for three slow heating rates, namely 8, 10 and 12 degrees C/min. The average values obtained from the three heating rate experiments were used to compare the model with the experimental data. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.