Hydrogen could be the energy carrier of the next world scene provided that its production, transportation and storage are solved. In this work the production of an hydrogen-rich gas by air/steam and air gasification of olive oil waste was investigated. The study was carried out in a laboratory reactor at atmospheric pressure over a temperature range of 700-900 degrees C using a steam/biomass ratio of 1.2 w/w. The influence of the catalysts ZnCl2 and dolomite was also studied at 800 and 900 degrees C. The solid, energy and carbon yield (%), gas molar composition and high heating value of the gas (kJ NL-1), were determined for all cases and the differences between the gasification process with and without steam were established. Also, this work studies the different equilibria taking place, their predominance in each process and how the variables considered affect the final gas hydrogen concentration. The results obtained suggest that the operating conditions were optimized at 900 degrees C in steam gasification (a hydrogen molar fraction of 0.70 was obtained at a residence time of 7 min). The use of both catalysts resulted positive at 800 degrees C, especially in the case of ZnCl2 (attaining a H-2 molar fraction of 0.69 at a residence time of 5 min). (C) 2008 Elsevier B.V. All rights reserved.