Treatment and Disposal of Gypsum Board Waste -- Industry Position Paper

Background Gypsum, or calcium sulfate dihydrate, (CaSO4 l 2H2O) is the major component of drywall, or gypsum board, core. It is a naturally occurring mineral, deposited largely as a result of the evaporation of water in ancient inland seas, which contained large amounts of dissolved gypsum. For example, the evaporation of a typical 20,000 gallon residential swimming pool filled with seawater will generate about 250 pounds of gypsum. In the White Sands National Park in New Mexico, over the years the action of the wind has caused a physical change to surface deposits of natural gypsum rock, converting them into gypsum sand which covers an area of 270 square miles. Yellowstone National Park, on the other hand, provides several good examples of chemical changes of naturally occurring gypsum within the sulfur hot springs, whereby bacterial action changes the gypsum into other sulfur-containing materials, including elemental sulfur. The well-known large deposits of sulfur in the salt domes of Texas and Louisiana are believed to be derived from the action of sulfate reducing bacteria (SRB) on large deposits of gypsum previously formed by the evaporation of ancient seas. However, such natural chemical changes of gypsum into other sulfurcontaining compounds require very specific conditions, including the presence of other chemical species. gypsum alone is a very stable material which will not decompose in air, as