Gypsum is a soft mineral (2H2O∙CaSO4). It is hardened and pressed between 2 paper liners to form a panel of drywall. Naturally occurring mineral gypsum forms when a body of water slowly evaporates. Synthetic gypsum is derived from the by-products of electric power plants. Nearly half of America’s electricity is produced from coal, generating about 130 million tons of waste each year. Coal-fired power plants recycle some waste through “scrubbers,” or chemical reactions that can oxidize and reduce the amount of sulfur in by-products of the coal combustion process to produce flue gas desulphurization (FGD), or synthetic, gypsum. Sulfur may be present in both natural and synthetic gypsum.