Carrying Fertiliser Cargoes: Self-Heating, Ammonium Nitrate, and What MV CHESHIRE Actually Taught the Industry

Not All Fertiliser Cargoes Behave the Same Way

UK P&I Club's Carefully to Carry — the industry's standard cargo reference, now in its 2023 Consolidation Edition — devotes Chapter 11 specifically to fertilisers, and for good reason: this is a cargo category where the wrong assumption about one shipment, based on how a similar-sounding cargo behaved last time, has caused real casualties. The critical distinction isn't fertiliser versus fertiliser — it's whether the specific cargo is liable to self-sustaining decomposition (SSD), a process where decomposition, once started, continues generating heat and toxic gas even after any external heat source is removed.

The Incident That Forced the IMSBC Code to Change

In August 2017, the bulk carrier MV CHESHIRE was en route from Norway to Thailand, fully loaded with cargo the shipper had declared as "Ammonium Nitrate Based Fertilizer (Non-Hazardous)" — specifically not liable to SSD, per its declared classification. During the voyage, cargo hold temperatures began rising and toxic gases were detected. The investigation found apparent self-sustaining decomposition had occurred, suspected to be triggered by a constant external heat source applied to the cargo during passage — despite the cargo's own declared classification saying this shouldn't have been possible.

The consequence was structural, not just procedural: the existing IMSBC Code schedule for "Ammonium Nitrate Based Fertilizer (Non-Hazardous)" was removed entirely from the 2022 edition of the Code. It was replaced with two separate, more specific schedules — Ammonium Nitrate Based Fertilizer – Group C and Ammonium Nitrate Based Fertilizer (MHB) – Group B — reflecting the fact that a single blanket "non-hazardous" classification had let cargo onto ships that shouldn't have been treated that way.

What This Means for Loading and Passage

• Never rely on the cargo name alone. "Fertiliser" and even "ammonium nitrate based fertiliser" cover cargoes with meaningfully different decomposition risk profiles under the current IMSBC Code. Check the specific schedule the shipper's declaration actually cites, not just the general product description.
• Group B cargoes (MHB — materials hazardous only in bulk) carry a chemical hazard and need specific precautions per their IMSBC schedule, potentially including SSD risk.
• Group C cargoes are not subject to any special IMSBC precautions on the basis of chemical hazard, but that classification depends entirely on the cargo actually meeting the criteria of its declared schedule — the MV CHESHIRE lesson is that a declaration can be wrong, and the consequences of trusting it uncritically are severe.
• Temperature monitoring during passage is the practical early-warning tool for any cargo with SSD potential — a rising trend, not just a single reading, is what should trigger escalation.
• Ventilation and stowage requirements differ by schedule — check the applicable schedule's specific requirements rather than applying a generic "dry bulk cargo" approach.

Related Ground: Coal's Self-Heating Risk

Fertiliser isn't the only bulk cargo where self-heating is the core hazard — coal cargoes carry a related but chemically distinct self-heating risk, already covered in Crew Connect's existing coal cargo Knowledge Checker content. The underlying discipline is the same across both: don't trust a declared classification as the end of the risk assessment, and treat a rising temperature trend as an early warning that demands escalation, not a number to note and move on from.

Test Your Knowledge

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Related Reading

• Berge Mawson — a bulk cargo hazard that killed three, and never showed up on a routine check