 To
obtain green standard recycled content credits a building material
generally must incorporate either post-consumer recycled
material, or pre-consumer recycled material (also known as
post-industrial recycled material) or both.
The definitions found in contemporary green
building documents differentiate between post-consumer and
pre-consumer material. LEED documents, for example, define
post-consumer material as “waste
material generated by households or by commercial, industrial
and institutional facilities in their role as end-users of
the product, which can no longer be used for its intended purpose” and
pre-consumer material as “material diverted from the
waste stream during the manufacturing process.”* Other
green standards contain similar, if not identical, definitions.
 The
gypsum board manufacturing industry has long been a leader
in the use of post-consumer recycled material. More than 50
years ago, long before recycling became popular, the gypsum
industry began recycling newsprint and other paper to manufacture
the paper facing for gypsum board. Today, nearly 100% of the
paper used in the manufacture of gypsum board face and back
paper comes from newsprint and consumer waste materials.
In 2010, the gypsum board manufacturing
industry produced or purchased approximately 700 thousand short
tons of recycled paper for use as facing and backing material
in the manufacture of gypsum board.** The gypsum industry’s
use of recycled paper diverted more than 1.9 million cubic
yards of material destined for landfills, enough to fill
more than 9,500 railroad cars.†
Gypsum board manufacturers also rely increasingly
on “synthetic” gypsum as an effective alternative
to natural gypsum. Synthetic gypsum is a byproduct primarily
from the desulfurization of flue gases in fossil-fueled power
plants. This material, too, would otherwise be disposed of
in landfills were it not used to manufacture gypsum panel products.
Synthetic gypsum and natural gypsum have the same general chemical compositions (CaSO4 ·2H20). Various types of synthetic gypsum are usually associated with their production processes. Synthetic gypsum that is suitable for use in wallboard includes flue-gas desulfurization (FGD) gypsum, fluorogypsum, citrogypsum, and titanogypsum.
The principal origin of synthetic gypsum in North America is the FGD process as power-generating or similar plants remove polluting gases from the stacks to reduce the emission of harmful materials into the atmosphere. Titanogypsum is a by-product from manufacturing titanium dioxide.
Some types of synthetic gypsum are generally considered unsuitable for use in gypsum board due to potential environmental hazards; for example, phosphogypsum may contain radon and radio nuclides. Synthetic gypsum with potentially harmful materials is not used to manufacture gypsum board. Members of the Gypsum Association do not use phosphogypsum to manufacture any gypsum-based product.
By using synthetic gypsum in its manufacturing process, the gypsum industry contributes to a cleaner environment in at least two ways. The majority of synthetic gypsum used by the industry is generated to keep the air clean; it is also an otherwise useless material that would take up valuable space in landfills if not used in the manufacture of wallboard. Both natural and synthetic gypsum are considered to be non-toxic and safe (except for phosphogypsum).
Certain impurities occasionally occur with natural as well as synthetic gypsum. The impurities are generally inert and harmless and typically consist of clay, anhydrite, or limestone in natural gypsum and fly ash in synthetic gypsum. Each individual source must be analyzed separately to assess its particular suitability which may vary depending on purity levels of the specific materials that have mixed with the gypsum at that source. Traditionally, most plants that incorporated synthetic gypsum into their board products relied on a mixture of synthetic and natural ore; however, modern plants can manufacture wallboard without using any natural gypsum.
In 2010, the United States gypsum board manufacturing
industry utilized approximately 7.6 million short tons of synthetic
gypsum. By conservative calculations, approximately 45% of
the gypsum used by U.S. manufacturers in 2010 was of the synthetic
variety.††
According to the most recent available statistics
published by the American Coal Ash Association, gypsum panel
manufacturing consumes approximately 40 percent of all the
flue gas desulfurization gypsum created in the United States.†††
In 2009, more than 7 million tons of material
that might otherwise be hauled to landfills, were used to make
gypsum panels and other gypsum products.
In addition to utilizing synthetic gypsum,
modern manufacturing techniques increasingly allow panel manufacturers
to use “re-grind” or production overrun material.
In specific instances, some manufacturers are also able to
use clean construction waste that has been inspected and sorted
for contaminants and transported directly from a job site.
Adherence to strict manufacturing criteria generally limits
the amount of re-grind or re-use material that can be incorporated
into new panels. Each manufacturing plant must assess its own
capability for introducing clean waste into its manufacturing
process.
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