Fertiliser is a low-value, high-bulk commodity, and for low-value high-bulk commodities the cost of moving the goods can rival or exceed the cost of making them. Ammonium sulphate sits at the extreme end of this, and the reason is arithmetic.
The density arithmetic
Ammonium sulphate contains 21 % nitrogen. Urea contains 46 %. Moving one tonne of nitrogen therefore requires about 4.8 tonnes of ammonium sulphate against about 2.2 tonnes of urea — more than double the freight, handling, storage and bagging cost per unit of nitrogen.
That ratio has one enormous mitigation: ammonium sulphate is not only a nitrogen product. Those same 4.8 tonnes carry roughly 1.15 tonnes of sulphur. If the buyer needs both nutrients, the correct comparison is not against urea alone but against urea plus a separate sulphur source, plus the cost of a second application pass. Where sulphur is genuinely required, ammonium sulphate’s density penalty narrows sharply or disappears. Where sulphur is not required, the penalty is real and unavoidable.
This produces the market’s defining geographic pattern: ammonium sulphate is competitive close to where it is produced and where sulphur is agronomically needed, and loses competitiveness with distance.
Where the freight cost actually sits
Delivered cost is a chain, and the ocean leg is often not the dominant link.
Ocean freight is the most visible component. It benefits from scale, so vessel size and the ability to load and discharge quickly matter, and it is exposed to bunker fuel costs and to general dry-bulk market conditions that have nothing to do with fertiliser.
Port handling covers discharge, storage and reclaim. Fertiliser is hygroscopic and corrosive to steel and concrete, and requires covered storage; berth availability and shed capacity are frequently the binding constraint on how much product a market can absorb in a season.
Inland distribution is regularly the largest single element, especially where product must move by road to dispersed rural destinations. Cost per tonne-kilometre by road is a large multiple of the cost by bulk vessel, so the last few hundred kilometres can outweigh several thousand kilometres at sea.
Bagging, where the market requires it, adds material cost, labour and a further handling step.
Physical properties that translate into money
Moisture. Water shipped as free moisture is freight paid for nothing, and it drives caking. Moisture specifications are commercial terms, not pedantry.
Caking. A cargo that consolidates in the hold or the shed must be broken out, which costs time, damages the product and generates fines. Anti-caking treatment and dry storage are cheaper than remediation.
Bulk density. Vessels and trucks are limited by weight or by volume, whichever binds first. A denser product uses cubic capacity more efficiently — one of the reasons compacted and granular grades handle better through the chain even before blending is considered.
Dust and attrition. Every transfer point degrades particles. Fines are lost to the wind, foul equipment, worsen spreading uniformity and can create dust hazards.
Corrosivity. Sulphate salts attack unprotected steel in the presence of moisture, so equipment and structures need protection and cleaning regimes — a real cost carried by handlers.
The purchasing implication
The only sound basis for comparing nitrogen sources is delivered cost per unit of nutrient actually required, at the point of use, counting every nutrient the product supplies and every application pass avoided or added. Comparisons made at the loading port, or on a per-tonne-of-product basis, systematically flatter the higher-analysis product and systematically penalise the dual-nutrient one.
The corollary is that ammonium sulphate’s natural market is regional. Long-haul movement happens, but it requires either a genuine sulphur requirement at the destination, an unusually favourable freight position, or supply that must find a home regardless — the situation described in the article on by-product economics.