About Urea

What is it?

Urea occurs in nature as the end product of protein metabolism by mammals, including humans, which excrete urea as a waste product in their urine. It is highly soluble in water and is odourless in its purest state.

First isolated by G.F. Rouelle in 1773, urea was then produced synthetically for the first time in 1828 in Germany, by F. Wohler.

Manufactured urea is a harmless, non-toxic white crystalline solid made by combining synthetic ammonia and carbon dioxide (CO2). Its high nitrogen content (46.7 per cent) makes it an effective and popular fertiliser. Urea has the highest nitrogen content of all solid nitrogenous fertilisers in common use, and is used widely in agricultural food production. In fact, 90 per cent of the world's urea production is used for fertiliser.

How is it made?

Urea can be produced as prills, granules or as a liquid. Its high nitrogen content means growers need to use less process product creating storage and transportation efficiencies.

Given the high concentration of nitrogen, its even application to crops is essential and it is generally applied to the soil in granules or as a foliar spray.

Urea granules are made by cooling liquid urea while rolling it in layers to create a hard, even sized granule. Granulated urea has the advantage of creating less dust and waste when handled and transported.

What is it used for?

The demand for urea throughout the world is significant with organisations including the International Fertilizer Industry Association (IFA) estimating the need is in excess of 150 million tonnes per annum.

Australia's agricultural industry has a high demand for urea importing over one million tonnes annually.

Aside from the use of urea as a fertiliser, it also has other applications, including:

  • A raw material for the manufacture of plastics (urea-formaldehyde resin)
  • A raw material for the manufacture of various glues (urea-formaldehyde or urea-melamine-formaldehyde)
  • An alternative to rock salt in the de-icing of roadways and runways (it does not promote metal corrosion to the extent that salt does)
  • An ingredient in some hair conditioners, facial cleansers, bath oils, and lotions
  • A flame-proofing agent (commonly used in dry chemical fire extinguishers as urea-potassium bicarbonate).

Urea is also an effective additive in fuels with Selective Catalytic Reduction (SCR) to reduce NOx (Nitrogen Oxide) emissions from gas turbines and diesel engines. Diesel technology is now making the shift to higher pressure fuel injection in order to reduce particle emissions (PM). This has a side effect of increasing NOx during combustion. By adding urea solution to this process, it reduces the NOx to harmless nitrogen and water vapour.

Why is it important?

The need for fertilisers to boost crop yields has become more critical than ever given the world's increasing demand for food. Global demand for urea in fertiliser production is high particularly throughout Asia for the growth of staple foods such as rice and wheat.

As crops are harvested, a significant amount of nutrients are removed from the soil. While some of these nutrients can be returned to the soil from organic matter, fertilisers are required to restore nitrogen levels in order to ensure future crop yields.

Urea has a slow nitrogen release rate so it keeps supplying nitrogen into the soil over an extended period of time.

Globally, urea is the most popular nitrogen based fertiliser. Nitrogen is essential for crop growth as it is an element used by plants to produce protein as well as it being a component of their DNA. Every tonne of grain requires around 25 kilograms of nitrogen. Fertilisation of crops allows better use of existing farmland, and avoids further deforestation.

Sandy soils in particular (such as those in Western Australia) have low nutrient levels. Urea is used to promote establishment and growth of plantation reforestation, which is recognised as a substantial carbon 'sink', typically absorbing some 25 tonnes CO2-e/ha/year.