NOx Tiers
NOx Tiers dictate maximum allowable NOx emissions for a marine engine, pending ship age and location
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Frequently Asked Questions
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MARPOL Annex VI Regulation 13 - Nitrogen Oxides - applies to all vessels. Furthermore, the regulation shall 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 that undergoes a major conversion on or after 1 January 2000 except when demonstrated to the satisfaction of the Administration that such engine is an identical replacement to the engine that it is replacing and is otherwise not covered under paragraph 1.1.1 of the regulation.
The regulation does not apply to:
Marine diesel engine intended to be used solely for emergencies or solely to power any device or equipment intended to be used solely for emergencies on the ship on which it is installed, or a marine diesel engine installed in lifeboats intended to be used solely for emergencies; and
A marine diesel engine installed on a ship solely engaged in voyages within waters subject to the sovereignty or jurisdiction of the State the flag of which the ship is entitled to fly, provided that such engine is subject to an alternative NOx control measure established by the Administration.
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The standards set forth in of MARPOL Annex VI Regulation 14 shall not apply to:
A marine diesel engine installed on a ship with a length (L), as defined in regulation 1.19 of Annex I to the present Convention, of less than 24 metres when it has been specifically designed, and is used solely, for recreational purposes; or
A marine diesel engine installed on a ship with a combined nameplate diesel engine propulsion power of less than 750 kW if it is demonstrated, to the satisfaction of the Administration, that the ship cannot comply with the standards set forth in paragraph 5.1.1 of regulation 14 because of design or construction limitations of the ship; or
a marine diesel engine installed on a ship constructed prior to 1 January 2021 of less than 500 gross tonnage, with a length (L), as defined in regulation 1.19 of Annex I to the present Convention, of 24 metres or over when it has been specifically designed, and is used solely, for recreational purposes.
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2008 Annex VI Amendments (Tier II/III) adopted in October 2008 introduced not only new fuel quality requirements beginning from July 2010, Tier II and III NOx emission standards for new engines, but also Tier I NOx requirements for existing pre-2000 engines.
Any pre-2000 vessel thus has to comply with Tier I NOx limit.
Furthermore t applies retroactively to new engines greater than 130 kW installed on vessels constructed on or after January 1, 2000, or which undergo a major conversion after that date.
The regulation also applies to fixed and floating rigs and to drilling platforms (except for emissions associated directly with exploration and/or handling of sea-bed minerals).
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An Emission Control Area (ECA) is a general term that applies to SOx, PM and NOx emissions control. IMO NOx tiers apply to all areas and all ships constructed after a specific date. Special rules apply inside a NOx Emission Control Area (NECA).
A NECA is an area with stricter NOx emission regulations, as dictated by MARPOL Annex VI regulation 13. Within a NECA, so called Tier III NOx limits apply. Outside NECAs, the maximum applicable Tier is II. Compliance to Tier III control is also dependent on a vessel age.
In NECAs, only engines installed on a ship constructed on or after a specific date must comply with Tier III. The regulation applies globally to any installed diesel engine above 130 kW output power and sets limits [g/kWh] based on the rpm.
A marine diesel engine that is installed on a ship constructed on or after the following dates and operating in the following NECAs must comply with the below Tier III NOx standard. Outside these areas, Tier II or I applies pending vessel age.
1 January 2016 and operating in the North American ECA and the United States Caribbean Sea ECA; or
1 January 2021 and operating in the Baltic Sea ECA or the North Sea ECA.
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Sanctions are established by individual Parties to MARPOL, as flag and port States. There is no established fine or sanction set by IMO – it is down to the individual State Party.
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We are looking into it! Come back soon.
So far we found the following:
The NOx control requirements apply to installed marine diesel engine of over 130 kW output power other than those used solely for emergency purposes irrespective of the tonnage of the ship onto which such engines are installed.
Definitions of ‘installed’ and ‘marine diesel engine’ are given in regulations 2.12 and 2.14 respectively.
More to follow soon!
About IMO NOx Tiers
The NOx tiers are approved regulations by the International Maritime Organisation (IMO) to reduce the limits of NOx emissions. The NOx control requirements apply to installed diesel engines of over 130 KW output power other than those used solely for emergency purposes irrespective of the tonnage of the ship onto which the engine is installed.
Tier I applies for ships constructed date on or after 1 January 2000, and limits the engine NOx emission
Tier II requires a reduction in NOx emissions by 20% compared to the previous Tier I values. Tier II applies for ships construction date on or after 1 January 2011
Tier III requires a reduction of 80% in NOx emissions compared to the previous values. Tier III control only applies for specified ships while operating in Emission Controlled Area’s (ECA). Applicable vessels have to comply with an 80% reduction in NOx emissions compared to Tier II. Outside the ECAs Tier II applies for all engines.
NOx Environmental Control Area (NECA)
A marine diesel engine that is installed on a ship constructed on or after the following dates and operating in an Environmental Control Area shall comply with the Tier III NOx standard:
1st January 2016 and operating in the North American ECA and the United States Caribbean Sea ECA; or
1st January 2021 and operating in the Baltic Sea ECA or the North Sea ECA.
Learn more about ECAs here.
How to comply
Tier II standards are - in most cases - ensured by the engine manufacturers. Tier III standards however impose significant challenges for engine manufactures, ship operators and certifiers from a technical and operational point of view, as without specific treatment of the exhaust gases the emission limits for NOx are unlikely to be met.
Typical measures to reduce NOx emissions includes - among others - optimizing engine settings, water-injection, the use of selective catalytic reductors, or the use of electric energy storage. Below is an overview of technologies and their reduction potential to meet the Tier II and Tier III requirement by DNV. Naturally more solutions are available, such as full electric propulsion or the use of hydrogen in an electrolyser setup. These are however less practical and far from affordable in many retrofit cases and are this not shown here.
