A.Alex Wilson, editor of Environmental Building News in Brattleboro, Vt., responds: You're right that it's not a good idea to simply bury scrap drywall in a hole. Under oxygen-depleted conditions, such as in a landfill or several feet underground in a covered hole, the gypsum (calcium sulfate) in drywall can decompose to release the noxious gas hydrogen sulfide. This gas is hazardous at high concentrations and an odor problem even at very low levels. Problems have sometimes arisen when builders have buried the scrap drywall from a house. The rotten egg smell is not at all popular with homeowners.

However, scrap drywall can safely be used as a soil amendment in the oxygen-rich, active top few inches of soil if it is properly pulverized and applied. Drywall is composed of paper facings and gypsum. Gypsum is often used as a fertilizer, adding both calcium and sulfur. Along with the benefits of the gypsum, the unbleached paper adds tilth to...

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