the addition of woody biomass to coal gasification can not only reduce CO2 emissions but also the problems caused by sulfur and ash contained in coal; this is because the woody biomass has almost no sulfur and low ash content. However, biomass gasification is relatively high-cost and produces relatively the large amount of tar. Therefore, the co-gasification can not only reduce the cost of the feedstock but also reduce the problems that occur in plant operation due to the production of tar.