Gypsum is a major dry bulk cargo, with global seaborne trade of approximately 30 to 40 million tonnes per year. The cargo is calcium sulphate dihydrate (CaSO4·2H2O), used principally as a setting retarder additive in Portland cement (around 5 per cent of finished cement) and as the principal raw material for plasterboard, plaster of Paris, and various industrial applications. The IMSBC Code regulates gypsum shipments under a Group C schedule with no major hazards.
Schedule structure
The IMSBC Code includes the following gypsum-related schedule entries:
- Gypsum: natural mined gypsum and synthetic gypsum (flue-gas desulphurisation gypsum, phosphogypsum). Group C (not liquefiable, no chemical hazard).
- Calcium sulphate: a closely related entry covering anhydrous calcium sulphate and selected synthetic forms. Group C.
Both entries cover non-hazardous cargoes handled under standard bulk procedures.
Cargo sources
Gypsum is supplied from three principal sources:
- Natural mined gypsum: traditionally the dominant source, with major production in the United States, Mexico, Spain, Türkiye, Iran, Oman, Thailand, and Australia. Supplied as crushed mined product.
- FGD gypsum (flue-gas desulphurisation gypsum): synthetic gypsum produced as a by-product of coal-fired power plant scrubbers. Increasingly important in regions with coal-fired generation. Supplied as a fine moist powder.
- Phosphogypsum: synthetic gypsum produced as a by-product of phosphoric acid manufacture. Limited use due to residual phosphate content and trace radioactivity from natural uranium in phosphate rock.
Most marine seaborne trade is natural mined gypsum, with FGD gypsum as a secondary contribution and phosphogypsum largely confined to land transport.
Cargo properties
Natural gypsum is supplied as crushed mined material with particle sizes typically 5 to 100 millimetres. Bulk density is approximately 1.3 to 1.5 tonnes per cubic metre. Stowage factor is approximately 0.7 to 0.8 cubic metres per tonne.
The cargo is non-toxic, non-flammable, non-self-heating, and non-reactive with steel. Handling concerns are similar to limestone but with somewhat lower dust generation due to the cohesive nature of gypsum mineral.
Major routes
Gypsum seaborne trade flows include:
- Oman and Iran to India and Southeast Asia: the dominant trade flow, with Omani gypsum from Salalah, Sohar, and Mina al-Fahal, and Iranian gypsum from Bandar Abbas, supplying Indian, Bangladeshi, and Vietnamese cement plants.
- Mexico to US East Coast and Mediterranean: significant export.
- Türkiye to UK and Northern European markets.
- Spain to North African and Mediterranean markets.
- Thailand and Vietnam coastal trade.
Oman is the dominant single exporter of gypsum globally, with several major mines providing sustained supply to the Indian and Southeast Asian cement industries.
Loading and discharge
Loading is by shore conveyor and shiploader. Loading rates of 1,500 to 4,000 tonnes per hour are typical. Hold preparation requires standard cleanliness and bilge clearance.
Discharge is by grab-fitted shore cranes at receiving cement plant berths and aggregate terminals.