Definition
Annex VI is IMO's rulebook for ship emissions. Its main regulations cover ozone-depleting substances (reg. 12), nitrogen oxides from diesel engines (13), sulphur oxides and particulate matter (14), volatile organic compounds (15), fuel oil availability and quality including the bunker delivery note (18), and energy efficiency (chapter 4). Compliance is certified by an International Air Pollution Prevention (IAPP) certificate.[1]
The sulphur limit is 0.50% worldwide since 1 January 2020 and 0.10% in emission control areas (ECAs) since 1 January 2015. The ECAs are the Baltic, the North Sea, the North American and US Caribbean areas, and the Mediterranean, whose SOx ECA took effect on 1 May 2025. New ECAs for the Canadian Arctic and the Norwegian Sea were adopted with entry into force on 1 March 2026, with their SOx limits applying from 1 March 2027.[2,1,3,4]
For buyers it decides what fuel to order on a route: VLSFO or a scrubber outside ECAs, 0.10% fuel (usually MGO) inside them, with a change-over completed before the ship enters. There is no ECA in the Arabian Gulf or Red Sea, but ships trading onward to Europe must plan the change.[1]
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Sources
- [1] REMPEC — Introduction to MARPOL Annex VI (PDF) — https://www.rempec.org/en/knowledge-centre/online-catalogue/1-introduction-to-marpol-annex-vi.pdf
- [2] IMO — IMO 2020: cutting sulphur oxide emissions — https://www.imo.org/en/MediaCentre/HotTopics/Pages/Sulphur-2020.aspx
- [3] REMPEC — Effective application of the Med SOx Emission Control Area — https://www.rempec.org/en/news-media/rempec-news/effective-application-of-the-med-sox-emission-control-area-under-marpol-annex-vi
- [4] Bureau Veritas — New Emission Control Areas for NOx and SOx — https://marine-offshore.bureauveritas.com/newsroom/new-emission-control-areas-ecas-control-nitrogen-oxides-nox-sulphur-oxides-sox-and
A working definition for buyers, not legal advice — the contract, the convention text and your club or class have the last word.