A synthetic cover for bulk material piles and loads in transit may be formed from a slurry mixture of liquid and powder made from recycled gypsum wallboard. These constituents may be mixed and applied to cover a bulk material pile and/or waste pile, and/or to control erosion. The cover will harden to minimize water infiltration, wind blown dust, odor and affinity to birds, flies and other insects. The liquid may include water, landfill leachate and wastewater; the powder from heated recycled gypsum wallboard may include alpha-hemihydrate and shredded paper, beta-hemihydrate and shredded paper or anhydrate and shredded paper. When clean water is used, the cover is non-toxic, non-combustible and harmless to fish, birds, plants and animals.