MARPOL Annex II Explained: A Practical Guide to Noxious Liquid Substances

They therefore justify less stringent restrictions than Categories X and Y, but their handling and discharge remain regulated.

Other Substances (OS)

Annex II also recognizes Other Substances (OS). These are substances evaluated as falling outside Categories X, Y and Z because they are considered not to present harm within the Annex II criteria when discharged from tank-cleaning or deballasting operations.

This gives seafarers a simple conceptual framework:

X → Major Hazard
Y → Hazard
Z → Minor Hazard
OS → Outside Categories X, Y and Z

Key MARPOL Annex II Requirements

Ships carrying Noxious Liquid Substances (NLS) in bulk must comply with requirements covering certification, cargo handling, residue disposal and record keeping.

1. NLS Certificate
Applicable ships must be surveyed and certified for carrying NLS in bulk. The substances carried and the tanks used must correspond with the ship’s approved certification and arrangements.

2. Procedures and Arrangements (P&A) Manual
The approved P&A Manual provides ship-specific procedures for cargo handling, tank cleaning, residue disposal, ballasting and deballasting. It should be treated as an operational guide, not simply as a required document.

3. Cargo Record Book
Relevant NLS cargo and residue operations must be properly recorded. The records should accurately reflect what actually occurred onboard.

4. Stripping Requirements
Efficient stripping minimizes cargo residues remaining in tanks and piping after unloading. For ships constructed on or after 1 January 2007, the maximum permitted residue is 75 litres per tank and associated piping for Categories X, Y and Z.

5. Prewash Requirements
A prewash is required in specified circumstances depending on factors such as the cargo category, substance characteristics and unloading performance. The resulting washings may need to be delivered to a port reception facility.

6. Discharge of NLS Residues
There is no universal permission to discharge NLS residues overboard. Regulation 13 establishes different requirements according to the substance and its pollution category. A useful sequence is:

Identify the cargo → Check its category → Consult the P&A Manual → Follow the required procedure → Record the operation.

7. Reception Facilities
When residues or tank washings cannot be discharged at sea, they must be delivered to an appropriate reception facility.

8. Antarctic Area
Discharge of NLS or mixtures containing them is prohibited in the Antarctic area, providing additional protection for this sensitive environment.

Port State Control

PSC officers may examine the ship’s certification, Cargo Record Book and approved cargo arrangements and verify that the substances carried are permitted in the tanks being used. The key principle is simple:

Compliance must exist both on paper and in actual shipboard operations.

Key Takeaways

For seafarers, Annex II compliance can be summarized as:

Cargo Classification + Certification + Procedures + Records

Know the substance and its category, confirm the ship is approved to carry it, follow the P&A Manual, and accurately record the operation.

Conclusion

MARPOL Annex II controls pollution from noxious liquid substances carried in bulk through the X, Y and Z classification system, certification, operational procedures and record keeping.

For seafarers, the practical principle is:

Know the substance. Know its category. Follow the approved procedure. Record what actually happened.

References

1. International Maritime Organization (IMO). (2022). MARPOL: Consolidated Edition 2022 – Annex II: Regulations for the Control of Pollution by Noxious Liquid Substances in Bulk.
2. International Maritime Organization (IMO). (2004). Resolution MEPC.118(52): Revised MARPOL Annex II – Regulations for the Control of Pollution by Noxious Liquid Substances in Bulk.
3. International Maritime Organization (IMO). International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (IBC Code).
4. International Maritime Organization (IMO). Chemical Pollution – MARPOL Annex II: Noxious Liquid Substances Carried in Bulk.
5. International Maritime Organization (IMO). Special Areas under MARPOL.