Urea

Urea is a chemical compound typically composed of carbon, oxygen, nitrogen and hydrogen. It is a white, odorless solid that dissolves readily in water. It is one of the most important substances produced in the human body and other animals as a means of excreting excess nitrogen from protein breakdown.

In agriculture, urea is the most widely used nitrogen-containing fertilizer in the world, because its nitrogen content is very high relative to its weight. It is also used in chemical manufacturing, pharmaceuticals, and systems for reducing air pollution from vehicles.

How the body produces it

When the body metabolizes protein, ammonia is produced, a toxic substance if it accumulates in the blood. The liver converts ammonia to urea through a metabolic cycle known as the urea cycle. The kidneys then filter urea from the blood and excrete it in urine. For this reason, blood urea nitrogen is commonly used as a measure of kidney function.

History of science

Urea has played a major role in the history of chemistry. In the 19th century, urea was synthesized from non-living matter, which helped overturn the belief that living things required a special 'vital force' in order to be created. This opened the path to modern organic chemistry.

Industrial production

In factories, urea is made by combining ammonia and carbon dioxide under high pressure and temperature. Ammonia itself is produced by the Haber–Bosch process, which uses nitrogen from the air and hydrogen obtained mainly from natural gas. For this reason, the price of urea on global markets is directly linked to energy prices.

Environmental impact

When urea is applied to soil, some of it breaks down into ammonia which escapes into the air, and some dissolves in groundwater as nitrate. This can lead to water pollution and excessive algae growth. Additionally, urea decomposition in the soil releases nitrous oxide, a potent greenhouse gas.