MARPOL Annex VI – Approved Method

Further to Lloyd’s Register’s Classification News No. 22/2010, dated June 3, 2010, the following frequently asked questions have been prepared in order to assist shipowners, and other interested parties, in understanding the issues associated with the retrospective Approved Method requirements as given in regulation 13.7 of MARPOL Annex VI as revised in 2008.

These frequently asked questions represent Lloyd’s Register’s understanding of the Approved Method requirements and hence do not supersede any relevant flag State instructions. These notes will be retained under review and will be amended as necessary in the light of developing experience and the issuance of any general IMO, or other, guidance on this matter. 

1. How does this requirement affect shipowners?

Owners of ships which are required to comply with MARPOL Annex VI, either by virtue of their flag State being a signatory or those ships operating in the waters of a signatory State, and which have installed engines which fall within the scope of this regulation will need to monitor the availability of an Approved Method for those engines and to fit such an Approved Method, or arrange for the required certification – see note 23 – within the given timescale following it becoming available.

2. To which diesel engines does this regulation apply?

Marine diesel engines, as defined in regulation 2.14, with a power output of more than 5000 kW and with an individual cylinder displacement at or above 90 litres which are installed on ships constructed on or after January 1, 1990, but prior to January 1, 2000.

3. Does this requirement apply to all such engines?

No, only to those engines for which there are commercially available Approved Methods as notified by the International Maritime Organization (IMO).

4. Which engine power value should be used as the criteria?

The maximum continuous rating as given on the engine’s nameplate. Where this is given in metric horsepower (PS) the conversion factor of 1 PS = 0.7355 kW should be used.

5. What if the engine has been derated from the nameplate value?

Such derating would need to be of a permanent nature to be so accepted. The revised value should be duly documented by the ship’s flag State, classification society or another authorised party.

6. What engines are represented by the ‘at or above 90 litre per cylinder’ criteria?

As general guidance, given the usual bore / stroke relationships of marine diesel engines, this typically represents trunk piston (medium speed) engines of 46 cm bore and above together with all crosshead (slow speed) engines other than those of the smallest bore – 26 cm. Shipowners however would be advised to assess for themselves the per cylinder displacement of the specific engines installed on their ships particularly in the case of those on the borderline.

7. What is the ‘ship construction’ date? 

This is defined in regulation 2.19 of MARPOL Annex VI. Further detail is provided in regulation 2.2 in respect of the term ‘similar stage of construction’.

8. What is an Approved Method?

An Approved Method is a means by which the NOx emissions from an engine, previously outside the NOx Technical Code certification requirements, will be controlled to not exceed the relevant limit value which in turn corresponds to that given for a Tier I engine (9.8 – 17.0 g/kWh depending on engine rated speed).

9. What in practice will constitute an Approved Method?

There is no prescribed Approved Method. It will however be certain redesigned engine components rather than being solely changes to engine operating values. In view of the limitations given within the regulation on the cost and impact on engine performance of an Approved Method it is expected to represent only certain components within the fuel injection system – most likely the fuel injection nozzles and fuel cam profile since these are the most influential components on NOx emissions. In addition there will, in all cases, be an Approved Method File which must be retained with the engine over its service life. This Approved Method File will detail the components and, if applicable, any related settings which constitute a particular Approved Method and how the engine so fitted is to be surveyed for compliance.

10. Will an Approved Method be engine specific? 

While it is possible for an Approved Method to be specific to a particular engine model, rating and duty (i.e. propeller law main engine) it is expected that in practice that an Approved Method will be certified as applying to a range of ratings (i.e. kW/cylinder and speed) for a given model and duty. In determining whether an Approved Method applies to a particular engine the power and speed values as given on the engine nameplate should be used – except as given in note 5.

11. Who will be developing these Approved Methods? 

It is expected that typically these Approved Methods will be developed by the relevant engine designers. However, there is no restriction as to the particular nature of an organisation which could develop an Approved Method and therefore it is equally open to others should they see this as an opportunity.

12. Is a shipowner with engines which fall within the given criteria required to develop an Approved Method if the engine builder or other party does not?

No, there is no such requirement.

13. How, and by whom, is an Approved Method certified?

An Approved Method is to be certified in accordance with Chapter 7 of the NOx Technical Code 20081. Certain definitions relating to the Approved Method requirements are given in Chapter 2 of the Code. In addition further clarification of certain aspects is given by Circular MEPC.1/Circ.678 . Unusually, for such requirements, the certification can be undertaken by the Administration of any signatory to MARPOL Annex VI and hence this will not necessarily be a particular ship’s flag State. In practice it is probable that, as with much of the NOx Technical Code certification, the actual approval will be undertaken by one of the Recognised Organisations acting on behalf of an Administration.

14. Are there any constraints on the cost of an Approved Method? 

Regulation limits the cost of an Approved Method to not exceed 375 Special Drawing Rights (SDR) per metric tonne of NOx calculated in accordance with the given formula taking into account the guidance given in Circular MEPC.1./Circ.6782. This will be confirmed as part of the certification process. SDR is an international reserve asset calculated daily on a weighted average of four currencies (US $, UK £, EU € and Japanese ¥) – for guidance, October 15, 2010, 1 SDR = 0.6320 US$.

15. Are there any constraints on the effect of an Approved Method on engine performance?

Regulation requires that in order to be certified it is to be verified by the engine designer that the Approved Method will not decrease the power by more than 1%, increase the fuel consumption by more than 2% or adversely affect engine durability or reliability.

16. By when does an Approved Method need to be installed?

Provided that an Approved Method is commercially available it is to be fitted no later than the first IAPP Certificate Renewal Survey (5 year survey) which occurs 12 months or later after the date of deposition with IMO of the notification by the Administration of the certification of a particular Approved Method.

17. How will IMO advise of the ‘date of deposition’? 

IMO will issue a MEPC Circular informing Administrations and the shipping community in general of the date of deposition of a particular Approved Method. As advised by Lloyd’s Register’s Class News 22/2010, further Class News will be issued repeating that advice. MEPC Circulars may be freely accessed from the IMO website ( In addition it is understood that in due course this information will also be posted within the Pollution Prevention Equipment section of IMO’s Global Integrated Shipping Information Service (GISIS).

18. How is GISIS accessed?

Access is freely available via the IMO website ( although it does require users to register.

19. What is the case if an Approved Method is not commercially available at the required Renewal Survey?

In those instances the Approved Method is to be fitted no later than the first IAPP Certificate Annual Survey after it has become so available.

20. What constitutes ‘not commercially available’? 

The regulation gives that the deferment in case of ‘not commercially’ available is only possible where despite the shipowners best efforts it has not been possible to have the Approved Method fitted as required. In this it should be noted that the reference to the Renewal Survey is in the context of ‘…no later than…’ rather than at the Renewal Survey. Furthermore, depending on the nature of the Approved Method, it may be that fitting can be undertaken by the ship’s engineers rather than requiring specialist shipyard or engine service personnel to undertake the work. Consequently, it would be recommended that as soon as the availability of an Approved Method is notified by IMO then the ordering and fitting planning should commence. Ultimately, it will be for the flag State to decide whether the shipowner has used their best efforts to obtain and have fitted a notified Approved Method.

21. Will there be more than one option as to the Approved Method to be installed? 

Since the timeline for the engines for which an Approved Method applies commences following the first notification of certification to IMO it is unlikely that there would be concurrent options. Of course, in the light of in-service experience a particular Approved Method may be further refined following its initial introduction. Therefore, it would be recommended that shipowners should not defer implementation plans awaiting other options to appear.

22. Will all engines which fall within the power and cylinder displacement criteria installed on ships constructed within the given dates be required to be fitted with Approved Methods?

It is quite probable that for those engines where there are only a very limited number of examples in service or which would require extensive modification in order to comply that no Approved Method will be developed and hence no requirement to fit. However, shipowners with such engines will need to monitor the availability of Approved Methods over the service life of those engines in case, at some time in the future, a relevant Approved Method is certified.

23. Is there any alternative to fitting an Approved Method? 

As given in regulation for those engines for which an Approved Method is available the alternative to fitting the Approved Method would be for the engine to be certified in accordance with the conventional NOx Technical Code procedures. In reality this would most likely only be possible for engines installed on ships which form part of a series whose construction dates overlapped the January 1, 2000 implementation date of the Tier I requirements. If this option is to be considered it would be recommended that dialogue as to this possibility be commenced with the certifier of the later engines at the earliest opportunity.

24. What is the status of an engine which falls within the power and cylinder displacement criteria installed on a ship constructed within the given dates but which has been certified to Tier I as a result of a ‘major conversion’ as defined in the Annex?

Since such an engine is already certified to Tier I no further action is required and no monitoring of Approved Method availability is necessary.

25. For those ships to which this Approved Method requirement potentially applies, how will this be handled at MARPOL Annex VI surveys prior to fitting? 

In the first instance it will need to be verified whether there is a notified and applicable Approved Method. If there is not - that is duly marked (-) in the relevant column of 2.2 of the Supplement to the IAPP Certificate – no further action at that time. If on the other hand there is such an Approved Method that will be duly marked (x) in the Supplement, additionally it will need to be assessed whether it is still within the time allowed for the fitting of that Approved Method. If it is within that time period then the survey can be completed, if not the survey cannot be completed and the ship would be without a necessary trading certificate. The exception being that where the Approved Method, although notified and it being outside the time allowed, was, to the satisfaction of the flag State, not commercially available despite the shipowner’s best efforts then that entry on the Supplement would be duly completed.

26. In those instances where an Approved Method has been fitted how would this be handled as part of a MARPOL Annex VI survey? 

The fitting of an Approved Method is to be verified on completion by, or on behalf of, the flag State. Guided by the Approved Method File, which is to be retained with the engine throughout its service life, it would be established that the Approved Method has been duly and correctly installed. If that is the case the ‘Approved Method installed’ entry in relevant column of 2.2 of the Supplement to the IAPP Certificate would be completed (x). Thereafter verification that the Approved Method continued to be applied would be an inherent part of each MARPOL Annex VI survey.

27. What are the implications in terms of port State control?

As part of the initial inspection which may be undertaken by port State control would be an assessment of whether any installed engines were required to be fitted with an Approved Method and, if so, whether such means had been installed within the time period allowed. In those instances where a commercially available Approved Method had not been installed as required that could be considered as a detainable deficiency and in accordance with regulation 10.2 of MARPOL Annex VI the ship prevented from sailing until the situation had been resolved.