The effect of woody biomass components on air-steam gasification was investigated using the downdraft fixed-bed gasifier at 1173 K and at atmospheric pressure. Cellulose, xylan, and lignin as model compounds of woody biomass components, and Japanese oak and Japanese red pine bark as woody biomass were employed as feedstock. The gasification conversions in cellulose, xylan, and lignin were 97.9%, 92.2%, and 52.8% on a carbon basis, respectively. In each run, the main components of the gas phase were CO, CO2, H-2, and CH4. The product gas composition in cellulose was 35.5 mol% CO, 27.0 mol% CO2, and 28.7 mol% H-2, and the CO composition was higher than the CO2 or H-2 compositions, which was similar to that in the Japanese oak, of which the main component was cellulose. In contrast, the product gas compositions in xylan and lignin were approximately 25 mol% CO, 36 mol% CO2, and 32 mol% H-2, and the CO composition was lower than the CO2 or H-2 compositions, which were similar to those in Japanese red pine bark, of which the main component was lignin. These results suggest that the fundamental information obtained in the gasification of each component could possibly be used to predict the composition of product gas generated in air-steam gasification of woody biomass. (C) 2004 Elsevier Ltd All rights reserved.