A study of one potential use for wastes from dry desulfurization of flue gas, namely removal of CO2 from natural gas, is reported. The CO2 absorption capacity was evaluated at atmospheric temperature for FGD wastes from four utility boilers, a coal-fired demonstration plant and four pilot-plant runs. These samples were examined as both hydrated solids and aqueous slurries. Capacities ranging up to similar to 55 m(3) Mg-1 were measured for the hydrated samples and up to similar to 120 m(3) Mg-1 for the slurries. The effect of hydration, absorption of CH4 and H2S, dissolution of metals in the slurry waters and mineralogical changes in the exposed wastes were examined.