A by-product of the burning of pulverized coal in electric power plants is sulfur dioxide (SO2) gas. To comply with the 1990 Clean Air Act, many plants have installed wet scrubber Flue Gas Desulfurization (FGD) systems to reduce their SO2 emissions. Due to its low-cost and availability, limestone is the most extensively used reagent. The limestone slurry reacts with the flue gas in the absorber, removing the SO2. The limestone in the slurry is converted into calcium sulfite, air is then introduced and oxidizes the sulfite into calcium sulfate which is then filtered and dewatered. This waste material is then either disposed of in ponds, landfills or sold as ingredients in the manufacturing of gypsum wallboard, cement or used as a fertilizer additive.