After industrial revolution, the increases of CO2 concentration in the atmosphere are resulted from the consumption of huge amounts of fossil fuels; hence causes global climate changes including temperature increasing and ocean level rising. Technologies on the mitigation of carbon dioxide emission have been developed, and CO2 removal from gas mixture by washing with solvent is one of the most widely practiced industrial gas-absorption processes. Wet scrubber requires large amount of water, resulting in decreasing the thermal efficiency of the system, hence the high temperature carbonation by dry techniques, such as adding sorbents of calcium and magnesium in the gasifier to react with carbon dioxide and form metal carbonate, is a trend for related fields. Therefore, reducing the cost of sorbents is of important in this technique. Consequently, two types of metal waste (slag and fly ash) are used to absorb carbon dioxide and identified their utilization under various conditions.