http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=104&topic_id=2322889&mesg_id=2322987I posted this:
http://www.ciwmb.ca.gov/condemo/wallboard/default.htmDrywall 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.
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.)
Not good if not properly disposed of either.
Another poster said Fla. gypsum used for fertilizer too radioactive (though low) to be used for drywall.