NOx emissions from vessels are regulated through the International Maritime Organization’s International Convention for the Prevention of Pollution from Ships (MARPOL).

MARPOL is the main international convention aimed at preventing pollution from ships.

MARPOL sets out tiered limits (Tiers I, II, and III) to progressively reduce NOx emissions globally, from marine diesel engines with a power output above 130kW. 

The Tier II limit applies in Australian waters.

Tier III-compliant engines are only a requirement for vessels built after specific dates operating in IMO agreed NOx Emissions Control Areas (NECAs). There are currently no plans to establish a NECA in Australian waters.

Further details can be found in MARPOL Annex VI and the NOx Technical Code 2008, as amended.

The Tier II limit applies in Australian waters