Drywall is the principal wall material used in the United States for interior purposes. It is made of a sheet of gypsum covered on both sides with a paper facing and a paperboard backing. Drywall can be recycled into new products, thereby:
- Creating business opportunities.
- Saving money for builders, contractors, and home renovators.
- Helping local governments meet their goal of reducing disposal by 50 percent.
Drywall is also referred to as gypsum board, wallboard, plasterboard, gypboard, and rock. Gypsum is calcium sulfate dihydrate (CaSO4·2H2O), a naturally occurring mineral that is mined in dried ancient sea beds. Some commonly heard names for drywall are actually brand names: Sheetrock® is a registered trademark of U.S. Gypsum Company; Gyproc® is a registered trademark of Domtar Gypsum.
The Construction Materials Recycling Association has developed an on-line resource for those interested in recycling gypsum drywall using a grent from US EPA Region 5.
Problems of Traditional Handling Methods
Landfill: Hydrogen sulfide gas may be produced when landfilling gypsum, particularly in a wet climate. Several conditions are required, including a moist, anaerobic environment and a low pH. Hydrogen sulfide gas is toxic at high concentrations (~1,000 parts per million) and has a foul, rotten-egg odor. Several communities in Canada do not accept drywall at landfills for this reason.
Incineration: Incineration may produce toxic sulfur dioxide gas. (Drywall is not incinerated in California.)
New Drywall: The U.S. produces approximately 15 million tons of new drywall per year. California’s annual usage is estimated to be 1.8 million tons.
New Drywall Scrap: Approximately 12 percent of new construction drywall is wasted during installation. Therefore, over 200,000 tons of new drywall scrap may be generated in California per year. The amount fluctuates with the construction industry, and with natural disasters such as floods and earthquakes.
Drywall Scrap Generators: Most drywall waste is generated from new construction (64 percent), followed by demolition (14 percent), manufacturing (12 percent), and renovation (10 percent).
The economic viability of gypsum recycling depends on a variety of factors, including:
- Landfill tipping fees.
- The cost of transportation, collection and processing.
- The value that secondary markets place on recycled gypsum.
Sizes Available: Drywall sheets come in sizes from 4 x 8 ft to 4 x 16 ft, and in thicknesses from 1/4 to 1 in. As 9-ft ceilings are becoming more popular, drywall is also now available in 4 1/2-ft widths.
Techniques: Drywall waste can be reduced by:
- Constructing standard-sized walls and flat ceilings.
- Ordering custom-sized sheets for nonstandard walls.
- Finding substitutes that are reusable, such as modular "demountable partitions" for commercial buildings.
Gunite Support: Gunite is concrete sprayed on at high pressure. Cutoff pieces of new construction drywall can be used as forms to support gunite as it is being sprayed. A swimming pool construction company uses new cutoffs for this purpose, in sizes from 4 x 2 ft to 4 x10 ft, and thickness of 1/2 to 3/8 in. The pieces are then discarded.
Construction Site Reuse: Drywall scraps can be placed in the interior wall cavities during new construction. This will eliminate the disposal and transportation costs. For guidelines, see Appendix C of A Builder’s Field Guide from the National Association of Home Builders (NAHB) Research Center at 1-800-368-5242 or (202) 266-8200. Or check their Web site www.nahb.com.
Donation: Habitat for Humanity is a nonprofit organization that builds affordable homes with donated materials. Several local chapters accept new drywall sheets of half size or larger.
Existing Markets for Drywall Waste
New drywall: Drywall gypsum can be recycled back into new drywall if most of the paper is removed. The paper limits the amount of recycled gypsum allowed in new drywall, because the paper content affects its fire rating. One company outside California produces drywall that is 15 to 20 percent recycled; it is working on technology to decrease the paper content so that it can further increase the recycled amount.
Soil Amendment: New construction drywall is currently being recycled into soil amendment in California. Although its use is controversial due to various additives, this use has shown promise in preliminary research. (CalRecycle does not recommend that demolition drywall scraps be used for agriculture.)
Markets: The soil amendment market includes:
- General agriculture.
- Mushroom growing.
- Forestry and mine reclamation.
- City parks and recreation areas.
- Residential lawns (sod).
- Golf courses.
- Compost (additive).
Benefits of gypsum: Gypsum provides the following benefits to soils:
- Improves water penetration and workability of an impermeable sodic (alkali) soil.
- Softens soil with a high clay content.
- Helps neutralize soil acidity.
- Adds plant nutrients calcium and sulfur.
Boron: Boron is a natural element that is added to drywall as a fire retardant. Although too much boron can be toxic to plants, it is a plant nutrient, and its addition may be beneficial where the boron content in the soil is low. Soils derived from volcanic materials tend to be boron deficient, such as in Shasta and Lassen Counties and the Tule Lake area. If uncertain, or if using on sensitive plants, check soil levels for boron.
Research: There are currently three studies, to CalRecycle staff's knowledge, that investigate the use of recycled drywall as a soil amendment. (See the reports by Korcak, Burger, and Dixon listed in "Publications".) The results seem promising; however, before solid conclusions can be reached, more data is needed.
Processing: New Construction Waste
Drywall waste from new construction sites is freer of contaminants than demolition drywall, and it is the most commonly recycled.
Equipment: Grinding equipment can range from a large plant to a small mobile chipper. A hammer mill is often used. The machinery grinds the drywall, producing about 93 percent gypsum powder and 7 percent shredded paper, by weight.
Gypsum: The gypsum can be sold as a powder, with or without paper, or molded into pellets.
Paper: The paper can remain for some uses, such as soil amendment, though it may be removed for aesthetic reasons. Most of the paper can be screened out and recycled into paperboard, new wallboard paper, packaging, etc., or composted.
Air Emissions: Drywall recycling produces dust, which can be handled with a baghouse or air vacuum system.
Processing: Demolition Waste
Drywall waste from demolition sites may be recyclable for nonagricultural markets. The following contaminants should be considered:
- Nails should be removed before processing.
- Tape breaks down in compost, or can be screened out.
- Joint compound is made primarily of limestone or gypsum. However, if the structure was built before the mid-1970s, asbestos may be found in the joint compound. For questions regarding asbestos, call your local air district, which can be located by calling the Air Resources Board's main number at (916) 322-2990, or visit their Web site at www.arb.ca.gov.
- Paint usually covers demolition drywall. Structures built before 1978 may contain lead-based paint. Lead can be detected with an inexpensive lead paint test kit. Drywall with lead-based paint should be disposed of properly. Mercury may also be a concern. For questions regarding paint containing lead or mercury, call the duty officer at the regional office of the Department of Toxic Substances Control (DTSC). The office can be located by calling the DTSC main number, (916) 324-1826, or by visiting their Web site at www.dtsc.ca.gov.
Drywall Processors and Collectors in California
There are approximately 44 drywall pickup sites and/or processors in California. (Fifteen of these are local Habitat for Humanity chapters, which take large reusable sheets as mentioned under Reuse.) Most processors take clean construction drywall only.
Siting a drywall recycling plant may require certain State and local permits, such as air, water, zoning, and possibly solid waste.
Where Can I Get Help?
Businesses starting or expanding into recycling activities may get financial, technical, marketing, business and permitting assistance from the "R-Team " at CalRecycle, by calling (916) 341-6526.
The local air districts may be concerned about nuisance odors and various emissions and may require processors to install equipment to control dust. Locate your local air district by calling the Air Resources Board at (916) 322-2990 or by checking their Web site at www.arb.ca.gov.
Your Regional Water Quality Control District may need to permit the facility depending on location. Look up your district in a local phone book under State Government, Water Quality Control Board, or check their Web site at www.swrcb.ca.gov.
Solid Waste Permits
The CalRecycle is currently developing a tiered permitting system. Contact your Local Enforcement Agency (LEA) for updates. To find your project area LEA, search the directory at "LEA Central" or call the CalRecycle LEA/EA Branch at (916) 341-6400.
Premier Gear & Machine Works
1700 N. W. Thurman
Portland, OR 97209
810 First St., NE, Suite 510
Washington, D.C. 20002
Publications And Resources
- "Gypsum Recycling in the Northwest." BioCycle, July 1991, p. 22.
- Harker, Byron. "A Technique to Recycle Gypsum." C&D Debris Recycling, Fall 1995, p. 8.
- Musick, Mark. "Recycling Gypsum from C&D Debris." BioCycle, March 1992, p. 34.
- Burger, Mark. Potential of Pulverized Construction Drywall Waste as a Soil Amendment, M.S. thesis, University of New York, December 1993. Contact Dr. Edwin H. White, Dean of Research, University of New York, College of Environmental Science and Forestry, 200 Bray Hall, Syracuse, N.Y., 13210 or call (315) 470-6606.
- Dixon, Robert C., Suitability of Ground Gypsum Board as a Source of Agricultural Gypsum for Application to Croplands. Certified Professional Agronomist, Stockton, California.
- Hardy Assoc's Ltd. Investigation of Means to Control Sulphide Production in Drywall Landfill Disposal Operations. 4052 Graveley St., Burnaby, British Columbia, 1984. Prepared for Gypsum Subcommittee of the Lower Mainland Refuse Project.
- Korcak, Ronald. Scrap Construction Gypsum Utilization, Plant Sciences Institute, USDA-Agricultural Research Service, Beltsville, Maryland 20705, July 1996. (301) 504-6591, firstname.lastname@example.org. Discusses placement of ground new drywall scraps into soil at new construction sites.
- Matrix Management Group. Gypsum Waste—A Progress Report with Recommendations for Best Available Technologies. Olympia, Wash.: Washington State Department of Ecology, 1990.
- Van Seter, D. and K. Hill. A Strategic Analysis of Waste Gypsum Wallboard Reprocessing in British Columbia. Vancouver, B.C.: Municipal Solid and Biomedical Waste Branch, Environmental Protection Division, Ministry of Environment, British Columbia, Canada, 1991.