Process optimization for catalytic biomass supercritical water gasification process (SCWG) was performed. By catalysts screening using cellulose and lignin as biomass model compounds, K2CO3 and 20Ni-0.36Ce/Al2O3 were identified as the best catalysts. Then, an optimization study based on Taguchi experimental design was conducted, and waste biomass including wheat straw, canola meal, and timothy grass were used as feedstock. The effect of different parameters are studied. For these parameters, the order of relative importance for hydrogen production is: temperature > catalyst loading > catalyst type > biomass type. High temperature (similar to 650 degrees C), and high catalyst loading (similar to 100%) are favorable for hydrogen production. The average hydrogen yield using different waste biomass was in the order of: canola meal > wheat straw > timothy grass. Crown Copyright (C) 2016 Published by Elsevier Ltd. All rights reserved.