Drywall, wallboard or gypsum are just a few of the many names this common building material is referred to. The big question surrounding this material is the reason why there is a need for it to be diverted from the landfill.
First, to understand why drywall is banned from the landfill, a look into what drywall is composed of is required. Gypsum is a naturally occurring mineral; it is composed of calcium sulphate (CaSO4) and water (H2O). Gypsum is mined from deposits formed by ancient seabeds.
If gypsum is a naturally occurring mineral then why can it not be sent to the landfill? The problem lies not with the calcium or hydrogen elements but primarily with the sulphur component.
Within a landfill or other construction and demolition dumping sites with drywall, rainwater will begin to dissolve the gypsum and concentrated areas of sulphate will occur that may contaminate groundwater. High concentrations of sulphate in ground water pose a significant risk to the environment.
Another serious problem that may occur is the result from the biological conversion of dissolved sulphate to hydrogen sulphide (H2S). H2S is a foul-smelling gas (rotten eggs). It is produced under wet, anaerobic conditions, such as those that often occur in landfills. The presence of high concentration pockets of hydrogen sulphide gas may be released by landfill workers and can be lethal if inhaled.
A remarkable characteristic of gypsum is its ability to be recycled again and again into usable products. Some examples include the production of new drywall, an ingredient for Portland cement, and as an additive for agricultural and composting operations. The drywall collected within the RDN is transported to New Westminster and recycled back into usable wallboard products. Even the paper is re-used in the process and converted to the brown backing on new gypsum products.