What is Flue Gas Desulfurization (FGD) Gypsum? Flue Gas Desulfurization (FGD) gypsum is a synthetic byproduct generated from flue gas desulfurization systems in coal-fired power plants and other industrial facilities. These systems use scrubbers to remove sulfur dioxide (SO₂) from combustion gases by reacting it with limestone or lime slurry, producing calcium sulfate dihydrate (gypsum). This...