Phosphogypsum (PG) is a byproduct of phosphate fertilizer production. It is produced when phosphate rock is treated with sulphuric acid during the manufacture of phosphoric acid, and is composed mostly of gypsum (CaSO₄^.2H₂O). Phosphogypsum is acidic, and contains residual P and F, as well as trace components contained in the apatite rock. Approximately 1.5 tonnes of PG are produced per tonne of phosphate rock consumed. In North America, traditionally the gypsum is stockpiled in stacks that can cover hundreds of acres and be over 100 feet high. Reclamation of PG stacks generally involves covering the stacks with soil or a synthetic liner and seeding with a grass mixture. The depth of soil required for reclamation success and environmental protection is a topic of much discussion in Alberta, with regulators contending that the default scenario of 1 meter of soil cover is appropriate. Preliminary research indicates that vegetation can be easily established on a closed gypsum stack with a minimal amount of soil. Results also indicate that there is minimal water infiltration and run-off and that trace element uptake by plant roots growing in gypsum is not a concern.