Natural catalysts (dolomite and olivine) not only reduce the tar content, they also have a high potential to enhance hydrogen production during gasification process. In this study, a bubbling fluidized bed (BFB) was used to evaluate the effect of the operating parameters on co-gasification of pine sawdust and brown coal namely gasification temperature (T-g) in the range of 700-1000 degrees C, fuel particle size (d(p)) in the range of 2.0-3.5 mm, steam/fuel ratio (S/F) in the range of 0.5-0.8, equivalence ratio (ER) in the range of 0.1-0.4, biomass ratio (BR) in the range of 0.0-100%, and catalyst loading in the range of 3.0-12.0 wt%. With increase in catalyst loading from 3.0 to 12.0 (wt %), the hydrogen yield was increased from 52.9 to 55.5 (g/kg-fuel) for dolomite and from 47.5 to 52.1 (g/kg-fuel) for olivine, while the tar yield sharply decreased from 5.4 to 0.4 (g/Nm(3)) and from 7.0 to 0.8 (g/Nm(3)), respectively. Fuel particle size showed a negligible influence on the upgrading of hydrogen production and tar yield. (C) 2018 Elsevier Ltd. All rights reserved.