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NOx emission limits

NOx emission limits

Shipping NOx emissions are regulated by mandatory limits on the emissions of new-build engines, defined according to engine speed. The limits for these different “Tiers” are shown in the table below.


The Tier III requirements apply to installed marine diesel engines operated in NOx Emission Control Areas (NECAs).  


Annex VI mandatory limits for NOx emissions of new-build engines
  Entry into force New diesel engines installed on ships NOx limit in g/kWh Relative reduction compared with Tier I
Tier I             2005 From 1 January 2000 to 1 January 2011 9.8-17.0 -
Tier II 2011 After 1 January 2011 7.7-14.4 15-25%
Tier III Flexible form, 2016 Flexible, but only when operating in NECAs 2.0-3.4 80%


Environmental legislation

LNG is a proven technology for complying with the upcoming MARPOL Annex VI regulations. At the moment, LNG is the only available option that is able to meet both the SECA and NECA requirements without the need for using marine gas oil.