Nitrogen oxide (NOx)


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The purpose of NOx regulations is to reduce the emission of nitrogen oxide (NOx) from ships since it contributes to air pollution ashore and to algal bloom in the sea.

The NOx regulations includes three levels Tier I, Tier II and Tier III.  

Tier I entered into force on the 1 January 2000;

Tier II entered into force on the 1 January 2011;

Tier III entered into force on the 1 January 2016 in the North American and the United States Caribbean ECA areas; and

enters into force on the 1 January 2021 in the ECA areas covering the North Sea and the Baltic Sea. These ECA areas includes the Baltic Sea, the Danish waters, Kattegat, Skagerrak, the Channel and the North Sea south of 62° north latitude and east of 4° west longitude.

Tabel
TierShip constructed on or after

Total weighted cycle emission limit (g/kWh)

n = engine's rated speed (rpm)

n < 130n = 130 – 1999n ≥ 2000
I1. Januar 200017.0

45·n(-0.2)

e.g., 720 rpm – 12.1

9.8
II1. Januar 201114.4

44·n(-0.23)

e.g., 720 rpm – 9.7

7.7

III

In the North American and the United States Caribbean sea area

1. Januar 20163.4

9·n(-0.2)

e.g., 720 rpm – 2.4

2.0

III

In the North Sea and the Baltic sea

1. Januar 20213.4

9·n(-0.2)

e.g., 720 rpm – 2.4

2.0


The requirement apply to each marine diesel engine with a power output of more than 130 kW installed on a ship and each marine diesel engine with a power output of more than 130 kW which has undergone a major conversion.

The requirement do apply also to marine diesel engines which is installed in existing ships on the dates specified in the table as well as for major conversions of engines e.g. if the output of the engine is changed outside the limits in the NOx approval or if the fuel injection system is changed. Replacement of an engine with an identical engine are exempted from the new requirements.

What does this mean?

For ships with trade permission covering the North American and the United States Caribbean ECA areas the tier III  requirements apply for marine diesel engines with an output of 130 kW or higher for ships constructed on or after the 1 January 2016 as well as for new engines installed in all ships on or after the 1. January 2016.

For ships trading in the North Sea and the Baltic Sea ECA areas the tier III  requirements apply for marine diesel engines with an output of 130 kW or higher for ships constructed on or after the 1 January 2021 as well as for new engines installed in all ships on or after the 1. January 2021. The requirements further apply to major conversions e.g. if the output of the engine is changed outside the limits in the NOx approval or if the fuel injection system is changed. Replacement of an engine with an identical engine are exempted from the new requirements.

How to do

For Danish ships sailing to ports outside Denmark, the tier III requirements must be documented by the ships EIAPP certificate, IAPP certificate, the technical file as required in MARPOL Annex VI and the NOx Technical Code Chapter 2 part 2.2.5.

For Danish ships exclusively sailing to and from Danish ports the tier III requirements can be documented by the engines type approval certificate (International IMO certificates is not necessary).

Frequently asked questions

What if the ship is trading in both tier II and tier III areas?

Tier III engines are normally also certified to tier II mode and the mode must be switched to tier III when entering an ECA area. It is also possible to have dedicated tier II and tier III engines used in the respective areas.  Such switch or dedicated operations must be recorded in a dedicated logbook.

Is it possible to install a cheaper tier II approved engine and then build in a selective catalytic reduction system (SCR system) in order to fulfill the requirement?

Basically NO – the NOx Technical Code require that engine and the after treatment system must be approved as a single entity (one single unit). However the other alternative solutions are available, and for ships with a combined engine power of less than 750 kW special considerations are possible, such alternative solutions must be assessed in each special case and must be forwarded to cfa@dma.dk.

What if a new engine is installed in an existing ship immediately before 1 January 2021?  

If the engine is installed in an existing ship before the 1 January 2021 the tier II requirement will apply even if the installation will not be surveyed and approved after the 1 January 2021. The date of installation of the engine on the actual engine placing in the ship.

What if a ship owner have an old ship with tier I or tier II engines and would like to meet the higher tier III requirements for environmental reasons can an after treatment  system then be installed?

Yes – if the engines meets the original approvals an after treatment system can me retrofitted to further clean the exhaust without being approved as a one single unit.

 NOx graph

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Maritime Regulation and Legal Affairs
Maritim regulering og jura
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