Hydrothermal treatment (HTT) is a promising way of upgrading biomass as a solid fuel and precursor of carbon materials by eliminating or transforming carbohydrates and also leaching alkali and alkaline earth metallic (AAEM) species. This study investigated steam gasification of a woody biomass that had been upgraded by HTT at 250 degrees C. HTT removed 8797% of AAEM species from the biomass. The char from the pyrolysis of the treated biomass underwent gasification, obeying first-order kinetics with respect to the mass of char over the entire range of conversion. This kinetics arose from non-catalytic gasification. AAEM species remaining in the char had no catalytic activity. The specific surface area of char increased monotonically with its conversion from 500 to well above 2000 m(2)/g. The non-catalytic nature of the gasification was responsible for such a significant surface area development. The surface area was, however, not a factor influencing the rate of gasification. The presence of the inherent AAEM catalyst and that of the extraneous potassium catalyst altered the kinetics of gasification to zeroth order while suppressing the surface-area development not only creating but also consuming micropores. The surface area was not a kinetic factor for the catalytic gasification.