Hydrogen as a clean energy source has great potential to reducing the dependence on fossil fuels and environmental pollution. For this reason, the production of hydrogen from renewable source will decrease this dependence and pollution. In this study, production of hydrogen from olive pomace was investigated. The experiments were performed at batch autoclave between 300 degrees C and 600 degrees C temperatures and a pressure of 200 atm-425 atm range. In addition to these parameters, the effect of catalyst (Trona, K2CO3 and KOH) was also investigated. H-2, CO2, CH4, CO and small amount of C-2-C-4 hydrocarbons were identified in gaseous products. H-2 formation increased with increasing temperature and decreased with pressure increase. Hydrogen formation has the highest value as 16.80 mol/kg biomass at 600 degrees C in the presence of KOH catalyst. Besides the effect of KOH, the presence of K2CO3 and Trona catalysts also increased the formation of hydrogen. The pressure affected the gasification yield and hydrogen composition in gaseous product. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.