AbstractRice husk and sawdust were selected as the raw materials for a study of biomass char yield in the range of 600 to 900 °C. It was found that temperature was the primary factor affecting the biomass char yield. The yield of the rice husk and sawdust chars decreased significantly with increasing temperature. As the residence time increased, the biomass char yield decreased. The smaller the size of the biomass particles, the higher the char yield. When the temperature exceeded 800 °C, the difference in the char yield was only slight. Given this finding, the surface morphologies of rice husk, sawdust, and their respective chars were investigated under various conditions via scanning electron microscopy. The effects of temperature on the pore structures were investigated by the Accelerated Surface Area and Porosimetry System. There were more holes in the biomass char, and the specific surface area was increased significantly as the temperature increased. The specific surface areas of rice husk and sawdust chars prepared at 900 °C were 320 and 1140 m2/g, respectively.