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. Read more about the regulations on NOx emissions.

When the chapter on air pollution from ships (chapter VI) of the MARPOL Convention was revised in 2008, new sulphur requirements were introduced and, at the same time, the NOx requirements were amended. This means that, from 2016, new ships must meet requirements that will result in an 80 per cent reduction of NOx emissions from ships, but only in NECAs (NOx Emission Control Areas).

Right now, there are NECAs only along the coasts of the USA and Canada and around a few American areas in the Caribbean. In the longer term the North Sea and the Baltic Sea are also expected to become NECAs.

At its recent session, the Marine Environment Protection Committee (MEPC) of the IMO approved the North Sea, the Baltic Sea and the English Channel as NECAs from 2021.

NOx regulations in detail

The regulations on the discharge of nitrogen oxides (NOx) are laid down in MARPOL Annex VI and the technical NOx Code.

The regulations, which apply to engines with an output of more than 130 kW, are as follows:

TIER I (Global regulations)

  • The use of marine diesel engines installed on ships constructed between 1 January 2000 and 1 January 2011 is prohibited unless the emission of nitrogen oxide from the engine follows the upper curve on the graph (see below).

TIER II (Global regulations)

  • The use of marine diesel engines installed on ships constructed on or after 1 January 2011 is prohibited unless the emission of nitrogen oxide follows the TIER II curve on the graph (see below). This corresponds to approx. a 15-20 per cent reduction compared to TIER I.

TIER III (NECA regulations)

  • The use of marine diesel engines installed on board ships constructed on or after 1 January 2016 and operating in a NECA must reduce NOx emissions by approx. 80 per cent compared to TIER I. See the lower curve on the graph (see below).

In addition, regulations apply to engines installed between 1 January 1990 and 1 January 2000 if they have an output of more than 5,000 kW. They must meet the TIER I requirements.

 NOx graf ny.jpg

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 Contact

Maritime Regulation and Legal Affairs
Clea Henrichsen, Special Adviser, M.Sc.(Eng)
+45 72 19 63 69