Here, "calcium nitrate residue" refers to a solid or semi-solid by-product generated and remaining from reaction, crystallization or separation steps during calcium nitrate production, compound fertilizer manufacturing or related chemical processes, with calcium nitrate as the main constituent and possibly containing unreacted raw materials, other inorganic salts and small amounts of impurities. After such calcium nitrate residue has lost its original function in use or been discarded, following collection, re-dissolution, purification or comprehensive utilization it can be used as a fertilizer raw material, chemical raw material or enter other resource recovery routes.