Urea is a white, crystalline, solid nitrogen compound with the chemical formula CO(NH2)2, made industrially from ammonia and carbon dioxide. It contains 46% nitrogen by weight, the highest nitrogen content of the solid nitrogen fertilisers in common use, and more than 90% of the urea produced in the world is used as fertiliser. The rest goes into animal feed, resins, melamine and the urea solution used to clean diesel exhaust.
What is the chemical formula of urea?
The formula is CO(NH2)2, sometimes written CH4N2O. The molecule is a carbonyl group (C=O) joined to two amino groups (NH2). The same compound is called carbamide in some standards and customs documents.
Urea occurs in nature. Mammals make it in the liver to dispose of surplus nitrogen and excrete it in urine, which is where the name comes from. In 1828 the German chemist Friedrich Wöhler prepared it in the laboratory from silver cyanate and ammonium chloride, the first time a compound known from living organisms had been made from inorganic materials. The urea traded today is all synthetic. How it is made, and where, is covered in our guide to how urea is made and where it is produced.
Two physical properties matter in handling. Urea melts at 132.4°C, and it is very soluble: about 1,200 grams dissolve in a litre of water at 25°C. That solubility makes it easy to apply as a solution and easy to damage with moisture in store.
What does urea mean on a fertiliser label?
On a fertiliser bag "urea" means a straight nitrogen fertiliser with the grade 46-0-0. The three numbers are the percentages of nitrogen (N), phosphate (P2O5) and potash (K2O). Urea carries 46% nitrogen and no phosphate or potash.
A sales specification for fertiliser-grade urea is short. The lines below are those on our granular urea page.
| Property | Typical limit | Why it is there |
|---|---|---|
| Total nitrogen | 46.0% min | The nutrient being bought |
| Biuret | 1.0% max | A by-product of manufacture that harms plants, most of all in foliar sprays |
| Moisture | 0.5% max | Wet urea cakes in the bag and in the hold |
| Particle size 2 to 4 mm (granular) | 90% min | Spreading width and blending with other granular fertilisers |
Biuret forms when two urea molecules combine during production. Most commercial urea contains only a small amount because the process is tightly controlled, and a low-biuret grade is sold for foliar use.
Granular or prilled
Solid urea is finished in one of two ways, and the two products are quoted separately.
- Prilled urea. Molten urea is sprayed from the top of a tower and solidifies into small beads as it falls. Prills are limited in size, up to about 2.1 mm in diameter. They dissolve fast and suit solutions, industrial use and markets that apply by hand. See prilled urea.
- Granular urea. Granules are built up by layering molten urea onto seed particles in a granulator. They are larger and harder than prills, stand up better to bulk handling and long voyages, and match the particle size of other granular fertilisers in a bulk blend. See granular urea.
The chemistry is the same. The choice follows the spreading equipment, the blend and what the destination market is used to.
What is urea used for?
Fertiliser
More than 90% of world urea production is applied to crops. Its high nitrogen content makes it the cheapest solid nitrogen to move per unit of nutrient, which is why it is the most widely used solid nitrogen fertiliser. It is spread on the surface, worked into the soil, dissolved in irrigation water or sprayed on leaves. It is also mixed with ammonium nitrate solution to make UAN, a liquid nitrogen fertiliser.
Animal feed
Feed-grade urea is added to rations as a low-cost source of non-protein nitrogen. Microbes in the rumen of cattle and sheep convert it to protein. It is a separate grade with its own specification and is not interchangeable with fertiliser-grade material.
Technical and industrial uses
- Resins. Urea is a raw material for formaldehyde-based resins, the adhesives in particleboard, MDF and plywood.
- Melamine. Melamine, used in laminates and tableware, is manufactured from urea.
- Diesel exhaust fluid. The fluid sold as DEF or AdBlue is 32.5% urea and 67.5% de-ionised water. It is injected into the exhaust of diesel engines fitted with selective catalytic reduction, where it breaks nitrogen oxides down. It needs a pure, low-biuret technical grade. See DEF / AUS 32.
How urea behaves in soil
Urea is not taken up by the crop in the form in which it is applied. Once it dissolves, the enzyme urease, which is present in nearly all soils, converts it to ammonium within a few days. During that conversion the pH around the granule rises for a time and part of the nitrogen can escape to the air as ammonia gas. This loss is called volatilisation.
According to the International Plant Nutrition Institute, the loss can range from nil to over 50% of the nitrogen applied. The conditions that favour it are surface application, less than 10 mm of rain or irrigation in the first few days, crop residues on the surface, high temperatures, high soil pH and soils with low cation exchange capacity. Working the urea into the soil, or rain soon after spreading, largely prevents it.
Urease inhibitors are the other answer. They are coated onto the granule and slow the enzyme for up to 7 to 14 days, which gives rain time to carry the urea into the soil. The most widely used is NBPT. The Institute cites research in which NBPT-treated urea cut ammonia loss by 50% to 90% against untreated urea. Treated urea is sold as a separate product at a premium, and the inhibitor has a shelf life, so the treatment date belongs on the documents.
How urea is traded
Urea moves in two ways: in bulk in the holds of dry cargo vessels, and in bags, either 50 kg woven polypropylene bags or 1 tonne jumbo bags, usually in containers. It is sold FOB the load port or CFR the discharge port, and prices change week to week with the large import tenders. We publish a dated urea price page and do not quote figures in guides. Buyers new to importing can start with our guide to buying urea in bulk.
CBIL brokers urea between a named producer or seller and a named buyer. Quality and weight are certified by an independent inspector such as SGS or Intertek from samples drawn at loading, and the producing plant is named on the certificate of origin.
Request a urea quote with the grade, quantity, packing and destination port.