Tier III emission limit for NOx

The Tier III emission limit for NOx will take effect for marine diesel engines installed in ships whose keels are laid on or after January 1st 2016 if operating within the North American and US Caribbean Sea ECA-NOx areas. This emission limit is equivalent to approximately an 80% reduction of NOx emissions from marine diesel engines and currently can only be achieved by using NOx reducing techniques such as selective catalytic reduction (SCR), exhaust gas recirculation (EGR) or fuel treatment is operating with oil. Some gas engines (particularly those operating on the Otto cycle and using spark ignition) can meet the Tier III emission limit however not all gas engines (particular those operating on the Diesel cycle with oil pilot fuel) offer Tier III compliance. This means that Tier III engine installations will be very different to existing Tier II engines, these differences may take the form of alternative fuels such as natural gas, may take the form of engines fitted with NOx reducing devices such as SCR or EGR or may take the form of fuel oil treatment systems using emulsifiers. Marine diesel engines installed in yachts and other small ships are not exempt from the Tier III emission limit unless one of the following applies:

1. The length of the ship (as defined in Regulation 1.19 of Annex I of the MARPOL Convention) is less than 24m and it has been specifically designed, and is used solely, for recreational purposes

Or

2. The combined nameplate engine propulsion power is less than 750KW and the Flag Administration agrees that the ship cannot meet the Tier III standard because of design or construction limitations

Or 

3. The engine is installed in a ship constructed prior to January 1st 2021 of less than 500 gross tonnage with a length (as defined in Regulation 1.19 of Annex I of the MARPOL Convention) of 24m or over which has been specifically designed, and is used solely, for recreational purposes.

Yacht owners should be aware that where a NOx reducing device is to be used then for the purposes of NOx emissions certification then the engine and NOx reducing device are to be certificated as a single entity. The applicant for certification may be the engine builder however it does not have to be the engine builder and third parties such as ship yards, NOx reducing device manufacturers and engine packages may make the application for certification. The certification process will be carried out in accordance with the NOx Technical Code 2008 and applicable IMO and Flag Administration guidelines.