Use of chars produced by carbonization of biomass (cypress chips) as molecular sieving carbon was examined. The possibility of separating binary mixtures of gases (CO2-CH4 and C3H8-C3H6) was investigated by measuring the amounts and rates of adsorption on the chars. With the CO2-CH4 mixture, both gases were adsorbed, and CO2 was adsorbed in greater amount than CH4. On the char prepared by carbonization at above 800 degrees C, the adsorption rate of CO2 was 30 180 times faster than that of CH4. With the C3H8-C3H6 mixture, only C3H6 was adsorbed on the char produced at 800 900 degrees C. On the char produced at 700 degrees C, the adsorption rate of C3H6 was 110 times faster than that of C3H8. Thus, it was concluded that the cypress char can be used for gas separation.