Urea

Urea is the most-traded fertilizer on earth and the densest solid source of nitrogen there is, at 46% N — which is exactly why it moves between continents while weaker nitrogen products stay regional. It is made by reacting ammonia with carbon dioxide under pressure, so its cost follows natural gas and its plants sit beside ammonia plants. Two technical points determine the grade. The first is biuret, a condensation by-product that forms when the melt runs too hot: a field crop tolerates 1% of it, a sprayed leaf does not, and diesel exhaust fluid allows 0.3% under ISO 22241 — so biuret content defines the grade. The second is what happens after spreading. Urea has to be hydrolysed by soil urease before a plant can take the nitrogen up, and when that happens on the surface a substantial share leaves as ammonia gas; a urease inhibitor such as NBPT is the standard answer, which is why the two products are so often bought together. Ehlinar supplies fertilizer, technical, low-biuret and feed grades, prilled or granular.

Appearance: White hygroscopic prills or granules, odourless when fresh and faintly ammoniacal as it ages; prills run about 1–2.4 mm and granules about 2–4 mm. Melts near 133 °C and dissolves readily — around 545 g per litre of water at 25 °C — taking heat out of the solution as it goes, so a concentrated batch cools noticeably while it mixes.

Applications

How we supply

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Also known as

Carbamide · Carbonyldiamide · Urea 46 · Urea 46-0-0 · Prilled urea · Granular urea · Automotive-grade urea (DEF / AdBlue feedstock)

Frequently asked questions

What does 46% nitrogen actually mean?

It is the mass fraction of nitrogen in the product: 100 kg of urea carries 46 kg of nitrogen. Pure urea is 46.6% nitrogen by formula, so a 46% specification is essentially the pure material with a little moisture and biuret allowed for. Nothing solid carries more, and that is the commercial point — freight, bagging and storage are charged on the tonne of product, not on the nitrogen in it, so the densest source travels furthest. It is also why urea dominates long-haul trade while a 27% product like CAN tends to be bought closer to where it is made.

Why does biuret matter so much?

Biuret forms when urea melt is held too hot for too long, and it is phytotoxic to leaves. At 1% in a soil application it is harmless and normal. A foliar spray or a fertigation line wants 0.25% or lower, because the damage shows as leaf scorch on exactly the crops that get sprayed. Diesel exhaust fluid is stricter again at 0.3%, for an unrelated reason: biuret decomposes to deposits in the SCR catalyst. The grades are not interchangeable, so state the end use in the enquiry rather than the biuret figure alone.

Can fertilizer urea be used to make AdBlue?

No. ISO 22241 caps biuret at 0.3% and controls aldehydes, insolubles, phosphate and a list of metals — calcium, iron, copper, zinc, chromium, nickel, sodium, potassium, magnesium, aluminium — at parts-per-million levels, because the SCR catalyst and the injector are sensitive to all of them. Fertilizer urea meets none of those limits and additionally carries an anti-caking coating that has no business in a dosing system. Automotive-grade urea is a separate purchase, and the saving from substituting it is smaller than one replaced catalyst.

Why is spread urea losing nitrogen into the air?

Because it is being hydrolysed on the surface. Soil urease converts urea to ammonium carbonate within a day or two, and if that happens where there is no soil water to hold the ammonium, it leaves as ammonia gas. Reported losses run from a few per cent to a third or more of the applied nitrogen, worst on warm days, on high-pH or calcareous soils, on crop residue, and when no rain or irrigation follows. The three practical answers are incorporation, applying before rain, and a urease inhibitor such as NBPT, which delays the hydrolysis long enough for the urea to move into the soil.

Prilled or granular urea?

Prills are smaller, about 1–2.4 mm, and made by dropping melt down a tower; granules are larger, about 2–4 mm, harder, and built up in layers. Granular urea survives bulk handling, long conveyor runs and spreading at wide bout widths without breaking down, so it dominates the international trade and any application that involves a spreader. Prilled urea dissolves faster and suits markets and processes set up for it, including material that is going to be dissolved anyway. Where either will be blended with other fertilizers, match particle size and density to the blend partners or the mix separates in transit.

How should urea be stored?

Dry, and that is close to the whole answer. Urea is not a dangerous good for transport and is not an oxidiser, but it is strongly hygroscopic: above roughly 70–75% relative humidity it draws water out of the air, and as conditions dry again it sets into a cake. Keep bags closed, keep bulk under cover on a dry floor, and do not store it alongside ammonium-nitrate-based fertilizer, because a dry mixture of the two goes damp at a humidity neither would survive alone. Most commercial grades carry an anti-caking coating — ask what it is, since the conditioner used on fertilizer urea is not always acceptable in a feed or technical application.