Drywall can be specified with synthetic gypsum, which is a byproduct or removing sulfur from the smokestacks of coal-fired power plants, and counts as pre-consumer recycled content. Before using it, however, check to see if it made in your region because the environmental impact of trucking it long distances is likely far greater than any benefit of using it instead of natural gypsum. Either way, the paper facing on drywall is almost always entirely post-consumer recycled.