Urea

Urea, also known as carbamide, is an organic compound with the chemical formula CO(NH2)2. It is the simplest diamide of carbonic acid and is the principal nitrogen-containing waste product excreted by many terrestrial animals, including humans. It is widely produced for industrial and agricultural use.

In pure form, urea is a colorless, crystalline solid that melts at about 132.7°C and then decomposes rather than boiling. It is highly soluble in water, and is miscible with many polar solvents. Urea forms hydrogen-bonded networks in the solid state and in solution.

Biologically, urea is formed in the liver by the urea cycle to detoxify ammonia, a byproduct of protein metabolism. It is transported in the bloodstream to the kidneys and excreted in urine as a primary waste product.

Industrial production of urea occurs mainly via the Bosch–Meiser process. Ammonia reacts with carbon dioxide under high pressure to form ammonium carbamate, which dehydrates to yield urea. This route yields the large quantities required for global demand. The largest single use of urea is as a nitrogen fertilizer, provided as granules or prills and containing about 46% nitrogen. It is also used as a non-protein nitrogen source in animal feeds and as a chemical precursor for urethane-forming resins, adhesives, foams, plastics, cosmetics, and pharmaceuticals.

Safety and environmental considerations include relatively low acute toxicity, though urea can irritate skin or eyes at high exposure. Excessive application as fertilizer can contribute to nutrient runoff and eutrophication, impacting aquatic ecosystems.