Operational Guide · Registers & Logbooks

# NOx Technical Code: Certification of Ammonia and Multi-Fuel Engines (MEPC 84)

An ammonia-fuelled or dual-fuel methanol engine doesn't enter the NOx regulatory framework by magic: MEPC 84 finalized the certification rules that were missing, ahead of formal adoption at MEPC 85.

NOx Technical Code MEPC 84 EIAPP ammonia dual-fuel

## Operational Explanation

The NOx Technical Code 2008, referenced by Regulation 13 of MARPOL Annex VI, sets out the test, survey and certification procedures (EIAPP – Engine International Air Pollution Prevention Certificate) for marine diesel engines subject to NOx limits. The Code, however, was historically designed for conventionally fuelled engines, leaving a procedural gap for new-generation engines fuelled by ammonia or in dual-fuel configuration on liquid fuels other than gas (methanol, ethanol).

MEPC 84 (27 April – 1 May 2026) finalized draft amendments to the NOx Technical Code that establish a clear regulatory basis for certifying NOx emissions from ammonia-fuelled engines, along with clarifications on engine test cycles and the use of Multiple Engine Operating Profiles. In parallel, amendments to the EEDI/survey guidelines were adopted to clarify the definition of "primary fuel" for dual-fuel engines running on two liquid fuels (typically methanol or ethanol), and new rows were provided for in the Supplement to the IAPP Certificate to denote the use of multiple engine operating profiles.

These amendments are expected to be formally adopted at MEPC 85 (October 2026), with entry into force anticipated in spring 2028: a Company evaluating or already planning ammonia-fuelled or non-gas dual-fuel engines should therefore follow the evolution of this framework closely, as it is still being finalized.

## Regulatory Reference

NOx Technical Code 2008 (referenced by MARPOL Annex VI, Regulation 13); amendments finalized at MEPC 84 (April-May 2026) for the NOx certification of ammonia-fuelled engines, multiple engine operating profiles and test cycles; related amendments to the EEDI/survey guidelines on the definition of primary fuel for non-gas dual-fuel engines (methanol, ethanol). Formal adoption expected at MEPC 85 (October 2026), entry into force anticipated in spring 2028.

## Scope of Application

Every Company that operates or plans to install ammonia-fuelled engines, or dual-fuel engines on liquid fuels other than gas (methanol, ethanol), subject to EIAPP certification under the NOx Technical Code.

## Procedure / How to Complete It

1. Monitor the formal adoption of the NOx Technical Code amendments expected at MEPC 85 (October 2026), ahead of the entry into force anticipated in spring 2028.
2. For ships with ammonia-fuelled or non-gas dual-fuel engines already at the design or construction stage, coordinate with the engine builder and the Classification Society on the applicable EIAPP certification procedure during the transitional phase.
3. For dual-fuel engines on liquid fuels (methanol/ethanol), verify the definition of primary fuel applied for EEDI calculation purposes, according to the updated guidelines.
4. Prepare the engine's technical documentation so it can accommodate the new Supplement to the IAPP rows relating to multiple engine operating profiles, once the amendments enter into force.
5. Do not assume that an ammonia-fuelled or non-gas dual-fuel engine is automatically excluded from NOx limits in the absence of a dedicated certification procedure: always check the applicable approach with the Classification Society in the meantime.

## Practical Example

Example: an owner ordering a newbuild with an ammonia/diesel dual-fuel engine asks the engine builder and the Classification Society for a preliminary assessment of the applicable EIAPP certification procedure, monitoring in parallel the outcome of the formal adoption at MEPC 85 before the ship's delivery.

## Real Cases

The transition to alternative fuels (ammonia, methanol, hydrogen) is in many cases outpacing the technical regulatory framework meant to certify their emissions: engines already ordered or under construction may find themselves having to apply certification procedures that are still being finalized, requiring close and continuous dialogue between the Company, the engine builder and the Classification Society to avoid delays in delivery or certification.

## Common Mistakes Mistake Library

Mistake | Consequence | How to avoid it
--- | --- | ---
No monitoring of the evolution of the NOx Technical Code amendments for an already-ordered ammonia-fuelled engine | Risk of finding, upon ship delivery, no clearly applicable EIAPP certification procedure | Actively monitor the adoption at MEPC 85 and coordinate in good time with the engine builder and Classification Society
Primary fuel definition for a methanol/diesel dual-fuel engine not verified against the updated EEDI guidelines | EEDI calculation potentially inconsistent with the current regulatory interpretation | Verify with the Classification Society the applicable primary fuel definition according to the most recent guidelines

## PSC Observations

The NOx Technical Code amendments are not yet adopted nor in force: they are therefore not subject to direct PSC verification. PSCOs continue to verify the validity of the existing EIAPP certificate and its consistency with the installed engine, under the rules currently in force.

## Operational Tips

- If you are evaluating an ammonia-fuelled or non-gas dual-fuel engine, don't wait for formal adoption at MEPC 85 to start the dialogue with the engine builder and Classification Society.
- Always distinguish between amendments 'finalized' at MEPC 84 and amendments 'adopted': formal adoption is expected only at MEPC 85 (October 2026).
- For dual-fuel engines on liquid fuels, check the updated definition of primary fuel for EEDI calculation purposes, as it can affect the ship's energy classification.

## Checklist

- Evolution of the NOx Technical Code amendments monitored toward adoption at MEPC 85
- EIAPP certification procedure for ammonia-fuelled/dual-fuel engines coordinated with the engine builder and Classification Society
- Primary fuel definition for liquid dual-fuel engines verified for EEDI purposes
- Engine technical documentation prepared for the future multiple engine operating profiles

## FAQ

Are the NOx Technical Code amendments for ammonia-fuelled engines already in force?
No: they were finalized at MEPC 84 (April-May 2026), but formal adoption is expected at MEPC 85 (October 2026), with entry into force anticipated in spring 2028.
What changes for dual-fuel engines on methanol or ethanol?
The amendments clarify the definition of 'primary fuel' for EEDI calculation and survey/certification guideline purposes, extending applicability to dual-fuel engines on liquid fuels other than gas.
What are Multiple Engine Operating Profiles?
A mechanism, introduced in the amendments, to recognise that an engine can operate under several distinct profiles (for example with different fuels), with new dedicated rows in the Supplement to the IAPP Certificate to document them.
🎬 Additional photos, videos and interactive diagrams for this topic will be available in a future version of the platform.

## Related Topics

MARPOL Annex VI Ammonia Engine Safety and Reliability

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