IMO NOx Tier III emission standards for NECA areas

By: Jeroen Berger, September 11, 2017

The IMO NOx Tier III emission standards will take effect in the NECA areas from January 1st 2016. The Tier 3 requirements are applicable to all new build vessels (500 GT and above) with a length of  ≥24 metres and sailing within a NECA zone with keel-laying on or after January 1st 2016 with an engine output of ≥130 kW. The IMO Tier III legislation also applies to a retrofit project by installing an engine with an output of more than 130 kW.


Which are NECA areas?


At the moment, the IMO NOx Tier III emission standards will take effect in the North American and US Caribbean Nitrogen Emission Control Areas (NECAs) from 1 January 2016. Besides that, the IMO has adopted the designation of the Baltic Sea and the North Sea as an emission control area for nitrogen oxides (NECA) for ships with keel-laying on or after 1 January 2021; this is decided during the 71th session of the IMO Marine Environment Protection Committee (MEPC 71).


What are the IMO NOx Tier III emission standards exactly?


Tier III controls only apply in the specific areas where the NOx emission are more seriously controlled (NECAs) and apply to the ships constructed after January 1st of 2016 or 2021.


As per Marpol Annex VI the IMO NOx Tier III emission standards are:


·         for engine speed less than 130 rpm – 3.4 gNOx/kwh;

·         for engine speed 130 and above but less 2000 rpm – 9*n-0.2 gNOx/kwh;

·         for engine speed above 2000 rpm – 2 gNOx/kwh.


The IMO NOx Tier 3 emission standards are 80% less than NOx Tier 1 emission requirements. Outside NECA, Tier 2 limits are applicable. Have a look at Table 1 and Figure 1 for more information.



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


1 January 2000



e.g., 720 rpm – 12.1



1 January 2011



e.g., 720 rpm – 9.7



1 January 2016



e.g., 720 rpm – 2.4


 Table 1: IMO Tier 1, IMO Tier 2 and IMO Tier 3 emission standards


Figure 1: IMO NOx Tier III emission standards in relation to IMO Tier II and IMO Tier I.


What are the solutions to meet the IMO NOx Tier III emission standards?


There are two promising solutions to meet the IMO NOx Tier III limits. The first example of this is LNG fuel. With LNG you can reduce 80 to 90% NOx, have almost no emission of particulate matter and are able to reduce the emission of CO2 with 20 to 25% in relation to a diesel engine used by ships.


The second option is the use of a SCR catalyst. The Selective Catalytic Reduction (SCR) method has the capabilities of reducing the concentration of polluting nitrogen oxide (NOx) in the exhaust gases of diesel engines, to below the emission regulations set by IMO Tier 3.


Don’t you know which Tier III solution is the most profitable in your situation? We from Berger Maritiem will be pleased to advice you for making the right sustainable decision.


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