Auto-thermal updraft gasification of biomass pellets in a packed bed reactor was conducted by using air and air-steam mixture. Air-steam gasification produced syngas with slightly improved lower heating value of 4.5 MJ/m(N)(3), in comparison to 4.4 MJ/M-N(3) produced during air gasification. The corresponding tar generation for air gasification and air-steam gasification was 212 g/m(N)(3) and 26.2 g/m(N)(3), respectively. Cold gas efficiency for air gasification and air-steam gasification was realized to be 91% and 91.4%, respectively. Carbon conversion during air-steam gasification reached about 91.5% while carbon conversion during air gasification was limited to 84.3%. (C) 2015 Elsevier B.V. All rights reserved.