IMO Convention
MARPOL Convention
International Convention for the Prevention of Pollution from Ships — 6 annexes covering oil, noxious liquid substances, packaged harmful substances, sewage, garbage and air pollution from all vessel types worldwide.
Overview
MARPOL was originally adopted in 1973 and was modified by the Protocol of 1978, which is why it is commonly referred to as MARPOL 73/78. It entered into force on 2 October 1983 when two annexes (Annexes I and II) came into force. Annexes III, IV and V followed later; Annex VI entered into force in 2005.
The convention applies to ships flying the flag of contracting states, as well as ships not entitled to fly the flag of contracting states but operating under the authority of a contracting state. Enforcement is carried out through port state control inspections, flag state surveys and class surveys.
Recent years have seen MARPOL Annex VI become the primary driver of maritime decarbonisation, with the EEDI (Energy Efficiency Design Index), EEXI (Energy Efficiency Existing Ship Index) and CII (Carbon Intensity Indicator) creating a regulatory framework for reducing greenhouse gas emissions from ships.
Annex Summary
| Annex | Title | Applies to | Key Requirements | Status |
|---|---|---|---|---|
| Annex I | Prevention of Pollution by Oil | Ships >400 GT; oil tankers >150 GT | Oil record book (ORB), oily water separator, MARPOL 15 ppm rule, oil discharge monitoring, slop tanks, crude oil washing | Mandatory |
| Annex II | Control of Pollution by Noxious Liquid Substances | Chemical tankers (NLS cargoes) | NLS categories X/Y/Z, cargo record book, prewash procedures, pump residue limits, approved ventilation | Mandatory |
| Annex III | Prevention of Pollution by Harmful Substances in Packaged Form | All ships carrying IMDG harmful substances | Proper packing, marking, labelling, stowage, quantity limitations per IMDG Code | Mandatory |
| Annex IV | Prevention of Pollution by Sewage from Ships | Ships >400 GT; ships certified for >15 persons | Sewage treatment plant, approved holding tank, comminuting/disinfecting system, discharge distance rules | Mandatory |
| Annex V | Prevention of Pollution by Garbage from Ships | All ships | Garbage management plan, garbage record book, plastics disposal ban (global), food waste restrictions by distance, port reception facilities | Mandatory |
| Annex VI | Prevention of Air Pollution from Ships | All ships with diesel engines >130 kW | SOx 0.5% global / 0.1% ECA, NOx Tier I/II/III, ODS prohibition, VOS monitoring, EEDI, EEXI, CII, SEEMP | Mandatory |
Emission Control Areas (ECA Zones)
Areas where stricter limits on SOx and NOx emissions from ships apply under MARPOL Annex VI.
| Zone | Designation | Controls | In Force | Notes |
|---|---|---|---|---|
| Baltic Sea | SECA (SOx ECA) | SOx 0.1% m/m | 2006 (SOx) | Covered under MARPOL Annex VI Reg. 14. Also Annex IV sewage special area. |
| North Sea (incl. English Channel) | SECA (SOx ECA) | SOx 0.1% m/m | 2007 (SOx) | Includes the English Channel. Annex V garbage special area. |
| North American ECA | SOx + NOx ECA | SOx 0.1% m/m; NOx Tier III | 2012 (SOx); 2016 (NOx) | Applies within 200 nm of US/Canadian coasts. NOx Tier III for ships built >=2016. |
| US Caribbean Sea ECA | SOx + NOx ECA | SOx 0.1% m/m; NOx Tier III | 2014 (SOx); 2016 (NOx) | Puerto Rico, US Virgin Islands area. Same NOx Tier III applicability as North American. |
| Mediterranean Sea | SECA (SOx ECA) | SOx 0.1% m/m | 1 May 2025 | Adopted by MEPC 80 (2023) — Mediterranean becomes 5th SECA from 1 May 2025. |
Carbon Intensity Indicator (CII)
The CII measures how efficiently a ship transports goods or passengers in relation to CO2 emissions. It is mandatory for ships of 5,000 GT and above under MARPOL Annex VI Regulation 28 (in force from 1 January 2023). Ships are rated annually from A (best) to E (worst) based on their operational CII value relative to the required CII for their ship type and size.
| Rating | Description | Regulatory Implication |
|---|---|---|
| A | Major superior | No action required. Recognised as best practice. |
| B | Minor superior | No action required. Target for improvement encouraged. |
| C | Moderate | Plan of corrective actions required in SEEMP Part III. |
| D | Minor inferior | Three consecutive D ratings = mandatory corrective action plan. |
| E | Inferior | One E rating requires immediate corrective action plan in SEEMP. |
Recent MEPC Amendments
| Year | Session | Resolution | Subject | In Force |
|---|---|---|---|---|
| 2023 | MEPC 80 | MEPC.377(80) | Mediterranean Sea SECA — Annex VI | 1 May 2025 |
| 2023 | MEPC 80 | MEPC.378(80) | Revised CII reduction factors 2026–2030 | 1 Jan 2024 |
| 2022 | MEPC 79 | MEPC.366(79) | EEXI and CII — operational carbon intensity | 1 Nov 2022 |
| 2021 | MEPC 76 | MEPC.328(76) | SEEMP Part III mandatory for CII compliance | 1 Nov 2022 |
| 2021 | MEPC 76 | MEPC.333(76) | Revised NOx Technical Code — Tier III | 1 Nov 2022 |
| 2018 | MEPC 73 | MEPC.305(73) | Initial IMO GHG Strategy adopted | Strategy (not binding) |
| 2016 | MEPC 70 | MEPC.278(70) | EEDI Phase 2 extension and new ship types | 1 Mar 2018 |