IMO NOx regulation

NOx pollution standards have been set on every type of motor vehicle and on stationary industrial units. For the marine sector, at a global level, the Marine Environment Protection Committee (MEPC) of the International Maritime Organisation (IMO) agreed a three-tier structure for new engines in 2008, which would set progressively tighter NOx emission standards depending on their date of installation. The NOx control requirements of Annex VI apply to installed marine diesel engines of over 130 kW output power.

Tier Ship construction date on or after Total weighted cycle emission limit (g/kWh)

n = engine’s rated speed (rpm)

n < 130 n = 130 – 1999 n ≥ 2000
I 1 January 2000 17.0 45·n(-0.2)

e.g., 720 rpm – 12.1

II 1 January 2011 14.4 44·n(-0.23)

e.g., 720 rpm – 9.7

III 1 January 2016 3.4 9·n(-0.2)

e.g., 720 rpm – 2.4


Source: IMO

Under the Tier III standard, NOx emission levels for an engine installed on a ship constructed on or after 1 January 2016 must be reduced to 3.4 g/kWh on any such ship operating in a designated Emission Control Area (ECA). Outside a designated Emission Control Area, Tier II limits apply. This represents an 80% reduction from Tier I (same NOx limit as EURO IV for diesel and petrol vehicles), and would require the use of Selective Catalytic Reduction (SCR) technology, or an alternative emissions control technology. In addition, special certification  must be obtained that the engine system is compliant with the Tier III requirements.


NOx Emission Control Areas

At present there are two effective NOx ECAs: the North American and the U.S. Caribbean Sea Areas (indicated in green on the map), as designated under regulation 13 of MARPOL Annex VI. The North Sea and Baltic Sea Area (indicated in blue) will become the third NOx ECA and will apply to ships with engines installed on or after January 1st 2021. Among the shipping community it is actively speculated that China is preparing its application for an ECA to be submitted to the IMO in 2019 or 2020. The scope and exact boundaries are not public knowledge yet but such a development will significantly help reduce dangerous NOx emissions and positively impact the lives of nearly a third of the Chinese population, who live near along the coast.

Source: DNV GL
Source: DNV GL