In H-2 production from woody biomass by steam gasification using CaO as a CO2 sorbent, the effect of reaction parameters such as the molar ratio of CaO to carbon in the woody biomass ([Ca]/[C]), reaction pressure, and reaction temperature was investigated on H-2 yield and conversion to gas. In the absence of CaO, the product gas contained CO2. On the other hand, in the presence of CaO ([Ca]/[C] = 1, 2, and 4), no CO2 was detected in the product gas. At a (Ca]/[C] of 2, the maximum yield of H was obtained. The H2 yield and conversion to gas were largely dependent on the reaction pressure, and exhibited the maximum value at 0.6 MPa. It is noteworthy that H-2 was obtained from woody biomass at a much lower pressure compared to other carbonaceous materials such as coal (> 12 MPa) and heavy oil (> 4.2 MPa) in steam gasification using a CO2 sorbent. H-2 yield increased with increasing reaction temperature. Woody biomass is the one of the most appropriate carbonaceous materials in H-2 production by steam gasification using CaO as a CO2 sorbent, taking the reaction pressure into account. (C) 2004 Elsevier Ltd All rights reserved.