Several impregnated metal ions (Fe (III), Co (II), Ni (II), and Ru (IV)) and a raw iron ore (natural limonite) were examined as catalysts for gasification of pine sawdust in air/CO2 at 700 and 800 degrees C. The yields of char and tar both increased with increasing CO2 content in the feed gas. All the impregnated metal ions, in particular Ni (II), Co (II) and Ru (IV), were very effective for promoting biomass gasification in CO2, leading to greatly reduced yields of tar and char accompanied by significantly enhanced formation of CO and H-2. At 800 degrees C, the impregnation of Fe (III), Ni (II), Co (II) or Ru (IV) led to almost complete conversion of the solid biomass into gas/liquid products, producing an extremely low char yield (<1-4 wt.%), and a very high yield of combustible gas (from 51.7 wt.% for Fe to 84 wt.% for Ru). The tar yield reduced from 32.1 wt.% without catalyst to 19-27 wt.% with the impregnated metal ions. (C) 2010 Elsevier Ltd. All rights reserved.