Gypsum Source Manufacture speaks to sources of gypsum, gypsum product manufacturing, product on building site and gypsum disposal and recycling.
Sources of Gypsum
Naturally occurring gypsum is not renewable but it is plentiful and widely distributed geographically.
The majority of newly extracted gypsum is quarried in surface mines, with attendant risks of loss of wildlife habitat, surface erosion and water pollution, as well as the problem of disposing of overburden and mine tailings.
There is increasing use of synthetic gypsum, material recovered from power plant flue gases that would otherwise be sent to landfill sites, in the manufacture of gypsum construction materials.
According to the Gypsum Association approximately 1.5 tons of synthetic gypsum is used annually to produce about 7 percent of the US construction industry’s calcined gypsum. Some synthetic gypsums, however, contain toxic byproducts from the manufacturing processes in which they are produced and cannot be safely recycled into new construction materials.
Gypsum Product Manufacturing
The calcining of gypsum involves temperatures that are not much higher than the boiling point of water, which means that the embodied energy of gypsum is relatively low, about 1200 BTU per pound (2.8 ML/kg) for plaster and 2600 BTU per pound (6.0 MJ/kg) for gypsum board.
The calcining process emits particulates of calcium sulfate, an inert, benign chemical as dust.
The paper faces of gypsum board are composed primarily of recycled newspapers.
Some manufacturers produce gypsum board products made with as much as 95 percent recycled materials, including synthetic gypsum and recycled postconsumer waste paper.
Gypsum Products on the Building Site
Approximately 15 million tons of gypsum board are manufactured annually in the United States. On a typical construction site, about 10 to 12 percent of this material becomes waste.
Gypsum board waste generated during construction can be minimized by sizing walls and ceilings to make efficient use of whole boards or by ordering custom sized boards for nonstandard size surfaces.
Gypsum board scrap can be permanently stored in the hollow cavities of finished walls, eliminating disposal and transportation costs and reducing the amount of material destined for landfills.
Some dust is generated by the cutting and sanding of gypsum board and plaster. This dust has not been tied to any specific illnesses, but it is a nuisance and a source of discomfort until the work is done and all the dust has been swept up and removed from the building. Remodeling and demolition also create large quantities of gypsum dust.
Most installed gypsum products have extremely low emissions. Some joint compounds may also be sources of emissions.
Additives used in the manufacture of moisture resistant and fire resistant gypsum board are potential sources of volatile organic (VOC) emissions.
Paints, wallcovering adhesives and other products used to finish gypsum surfaces can be significant emitters of VOCs and thus require care in selection and specification.