MARPOL Annex VI — Air Pollution Prevention
MARPOL Annex VI is the chapter of the MARPOL Convention (International Convention for the Prevention of Pollution from Ships) that regulates air pollution from ships. It sets limits on sulphur oxides (SOx), nitrogen oxides (NOx), ozone-depleting substances, and greenhouse gas emissions.
Answer in Brief
MARPOL Annex VI controls what ships burn as fuel and what they emit. The most impactful provision for daily operations: ships must use fuel with maximum 0.50% sulphur globally (since 2020), and 0.10% sulphur in Emission Control Areas (ECAs).
Key Regulations in Annex VI
Regulation 14 — Sulphur Oxides (SOx)
Global sulphur cap (IMO 2020): From 1 January 2020, all ships must use fuel with sulphur content ≤ 0.50% m/m (mass by mass). This replaced the previous 3.5% global limit.
In Emission Control Areas (ECAs): Ships must use fuel with sulphur content ≤ 0.10% m/m. This has been in force since 2015 for SOx ECAs.
Current SOx ECAs:
- North Sea and Baltic Sea
- North American ECA (US and Canadian coastal waters)
- US Caribbean ECA
- (China has its own coastal ECA under domestic regulations)
Compliance methods:
- Use low-sulphur fuel (VLSFO — Very Low Sulphur Fuel Oil, 0.5%; LSMGO — Low Sulphur Marine Gas Oil, 0.1% in ECAs)
- Fit an exhaust gas cleaning system (scrubber) — allows continued use of HFO but cleans exhaust to equivalent levels
- Use alternative fuel (LNG, methanol, ammonia — no sulphur)
Ship’s obligation: Maintain a Bunker Delivery Note (BDN) for all fuel received — shows sulphur content. Oil Record Book Part II records fuel management. FONAR (Fuel Oil Non-Availability Report) filed if compliant fuel genuinely unavailable at a port.
Regulation 13 — Nitrogen Oxides (NOx)
NOx from marine diesel engines is regulated in three tiers:
- Tier I: Applies to engines built 2000–2010 — basic emission limit
- Tier II: Applies to engines built after January 2011 — stricter limit (global)
- Tier III: Applies to engines built after January 2016 operating in NOx ECAs — significantly stricter (requires SCR or EGR technology)
NOx ECAs: North American ECA and US Caribbean ECA have NOx Tier III requirements.
Regulation 12 — Ozone-Depleting Substances
Prohibition on deliberate emissions of ozone-depleting substances (CFCs, HCFCs). Ships must not use refrigeration systems using banned refrigerants. Records maintained in Ozone-Depleting Substances Record Book.
Energy Efficiency Measures (Regulations 20–28)
EEDI (Energy Efficiency Design Index) — mandatory for new ships, requiring minimum efficiency standards.
SEEMP (Ship Energy Efficiency Management Plan) — required on all ships. Documents how the ship manages fuel efficiency.
CII (Carbon Intensity Indicator) — since 2023, ships are rated A–E annually on carbon intensity. Ships rated D or E for 3 consecutive years must prepare corrective plans.
Seafarer Responsibilities for MARPOL Annex VI
Chief Engineer:
- Ensure bunkers received meet sulphur requirements for current trading area
- Maintain Bunker Delivery Notes and fuel sample records
- Manage fuel changeover when entering/exiting ECAs (documented in ORB and engine log)
- ECA fuel changeover procedure: start changeover well before ECA entry, complete changeover before ECA boundary
Chief Officer:
- Maintain awareness of ECA boundaries for voyage planning
- Ensure SOPEP includes reference to air pollution incidents
All Officers:
- Know when the ship is entering an ECA and the applicable fuel requirement
- Engine log must record ECA entry/exit and fuel in use
Frequently Asked Questions
Q: What happens if a ship uses high-sulphur fuel in an ECA? This is a serious violation — subject to port state control detention, large fines (up to millions of dollars in some jurisdictions, e.g., US USCG enforcement), and prosecution. Evidence is checked via fuel sample testing in port.
Q: What is a scrubber? An exhaust gas cleaning system (EGCS) that removes SOx from engine exhaust using water washing. Ships with scrubbers can burn high-sulphur HFO while meeting emission limits. Scrubbers have their own washwater discharge regulations.
Q: What is VLSFO? Very Low Sulphur Fuel Oil — marine fuel with ≤ 0.5% sulphur, developed to meet the IMO 2020 global sulphur cap. Different from LSMGO (0.1% sulphur) used in ECAs.
Questions about ECA compliance, fuel changeover procedures, or MARPOL Annex VI requirements? Chat with SailorGPT