Byproduct Gypsum

The United States was the world's leading consumer of crude gypsum in 1982, with a demand of 16 million metric tons in the manufacturing of gypsum wallboard as a set retarder in cement, and some demand for its uses in agriculture. Only about 4% of this was byproduct gypsum sold for agricultural land plaster. Byproduct gypsum is the chemical end product of industrial processing plants, consisting primarily of calcium sulfate dihydrate, CaSO4·2H2O. The oldest byproduct-gypsum-producing industry is that of the phosphate rock chemical processing in Florida. Large sludge ponds and retaining stockpiles are accumulating, and total tonnage may approach 1 billion metric tons by year 2000. The United States has no firm plans for recycling and utilization of this and other forms of byproduct gypsum. Environmental pressures because of solid pollution and the increasing cost of land may influence the United States to develop better utilization within the next ten years. Projected production of byproduct gypsum from coal burning power plant fluegas desulfurization systems may be equal to the production tonnage of 30 million metric tons per year of phosphogypsum by 1990, thus adding more social and economic pressures for utilization. Japan phased out natural gypsum production in 1976, and now is recycling 6 million metric tons per year of byproduct gypsum for wallboard, cement, and plaster. She is now leading the world in the technology of utilization of byproduct gypsum, with a balance established between supply and demand. European countries have active research and development projects but are still dumping many million tons per year into the sea. It is suggested that the United States use more of the increasing tonnages of byproduct gypsum for its traditional uses of wallboard, plaster, and as a set retarder in cement. Other high-tonnage uses are offered, such as cellular foamed gypsum for insulation, road construction, gateway supports in coal mines, and its potential as the largest sulfur resource in the world.