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Maritime Insights and Knowledge-hub How does the MARPOL Annex VI work?

How does the MARPOL Annex VI work?

IMO & MARPOL Oct. 21, 2024
How does the MARPOL Annex VI work?

MARPOL Annex VI imposes restrictions on the release of sulphur oxide (SOx) and nitrogen oxide (NOx) from ship exhausts. Limits on SOx content and NOx emissions vary depending on the sea area and the ship’s construction date.

To address the need for less pollution near coastal regions, Annex VI defines several Emission Control Areas (ECAs). In these areas, ships must meet stricter standards for NOx emissions and/or SOx content in fuels.

In ECAs, ships must meet the Tier III standards regarding NOx emissions and/or the limit on SOx is 0,10% [m/m].

MARPOL 3 Nox 739X739

Today there are six active ECAs:

> The Baltic Sea 
> The North Sea
> The North American Area West
> The North American Area East
> The Hawaii Area
> The U.S Caribbean Area

 

At the time of writing, all ECAs are both SOx- and NOx-constrained. As of 1 May 2025, the Mediterranean Sea will effectively become an ECA for SOx.

MARPOL 3 Sox 739X739

Arctic and Norway Join ECAs, New Zones Proposed Worldwide

The Canadian Arctic and the remaining Norwegian coast not already covered by the existing ECAs, were approved on the 81st session of the Marine Environment Protection Committee on March 24 2024 and will take effect in 2027.

 

There are several potential future ECAs, covering coastlines at the North-East Atlantic Ocean, in Mexico, Australia, Singapore, China, Korea and Japan.

 

In open waters outside the ECAs, the IMO 2020 regulation establishes a SOx cap of 0.5% [m/m] for all seagoing vessels. Outside the ECAs, ships must meet the Tier I and Tier II limits on NOx emissions.

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