Urea contains 46% Nitrogen by weight [25% more than Ammonium Nitrate]. All the nitrogen is in the ammonium form. Urea is a white crystalline substance with the chemical formula CO(NH2)2; it is highly water soluble and contains 46% nitrogen. Urea is considered an organic compound because it contains carbon.

It was the first organic compound every synthesized by chemists; this was accomplished in the early 1800s by German chemists. Urea is made by reacting carbon dioxide (CO2) with anhydrous ammonia (NH3) under 3,000 psi pressure and at 350° F. The removal of water that occurs during the reaction is referred to as "dehydration." The resulting molten mixture is further processed into either prills or granules.

At Bunns we sell two types of urea

• Prilled Urea
• Granular Urea

Although Urea is nearly always cheaper than the Ammonium Nitrate alternative, it can lose some of its nitrogen as ammonia gas. A good rule-of-thumb it to assume that about 10% of the nitrogen can be lost by volatilisation, although this can be reduced by avoiding spreading on hot & windy days. So, Urea may not always be as cheap as it looks.

Urea is very light. The specific gravity [litre weight] is only about 750 grammes per litre, so each granule is too light to be spread at the widest bout widths. Consequently, it cannot be reliably spread over 20 metres and care should always be taken to spread on still days unless a boom 'air' spreader is used.

At Bunns, we have our own dedicated Urea processing plant so that

• The risk of contamination of Urea with other raw materials [particularly Ammonium Nitrate] is eliminated. This makes sure that the risk of the Urea 'going-hard' is reduced.
• For Urea-bagging, we use the thickest bag liners so that the risk of moisture getting into the bag is minimised.

For details of Urea Production, see the Keele University [UK] Chemistry Department's Urea Production Tutorial.

Product Safety

Product Safety Data Sheet Group 6