FGD gypsum is produced in coal-fired power plants using a lime scrubbing process. Since 1983, flue gases from German power plants fired with fossil fuels must be desulphurised. This is carried out in a quality-controlled flue-gas desulphurisation process that produces FGD gypsum (flue-gas desulphurisation plant gypsum) as its end product. In a process known as flue-gas scrubbing, the sulphur is removed from the flue gas and is then transformed into FGD gypsum by reacting it with lime or limestone, water and air.