In this study, carbon conversion was calculated from the data obtained with a real-time gas analyzer. In a lab-scale furnace, each biomass sample was pyrolyzed in a nitrogen environment and became biomass char. For preparation of the char, the furnace was electrically heated over 40 min up to the wall temperature of 850 degrees C, and maintained at the same temperature over 17 min. The furnace was again heated over 3 min to a temperature higher than 850 degrees C and then CO2 was injected. The biomass char was then gasified with CO2 under isothermal conditions. The reactivity of biomass char was investigated at various temperatures and CO2 concentrations. The VRM (volume reaction model), SCM (shrinking core model), and RPM (random pore model) were used to interpret the experimental data. For each model, the activation energy (E) and pre-exponential factor (A) of the biomass char-CO2 reaction were determined from gas-analysis data by using the Arrhenius equation. For the RPM, the apparent reaction order was determined. According to this study,it was found that the experimental data agreed better with the RPM than with the other two models. Through BET analyses, it was found that the structural parameter (psi) of the surface area for the RPM was obtained as 4.22. (C) 2010 Elsevier Ltd. All rights reserved.