Abstract: Waste solidification compositions and methods of using them repurpose calcium-containing industrial by-products. The compositions comprise either 1) a) auto shred residue; and b) a particulate wood-based product, or 2) a) a solid, particulate calcium-containing compound; and b) a superabsorbent material. The method of repurposing a solid, particulate calcium-containing industrial by-product comprises a) blending the by-product with a superabsorbent material to form a waste solidification composition; b) adding the waste solidification composition to a liquid industrial waste stream; and c) allowing the waste solidification composition to absorb at least 1 times its weight of the liquid industrial waste stream to form a solid waste product. The solid waste product passes Paint Filter Liquids Test Method 9095B.