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Methane and N2O reporting

Methane slip and N2O measured onboard, following MEPC.414(84) and in support of EU reporting.

The rules behind it What we measure Actual methane slip instead of default values From measurement to documents How a campaign works

The rules behind it

IMO and EU are moving at the same time.

For owners and operators of LNG dual-fuel vessels, methane slip is no longer a side issue. It has to be understood, measured and documented.

IMO

MEPC.414(84), the 2026 IMO Guidelines for test-bed and onboard measurement of CH4 and N2O, replaces the earlier guidelines MEPC.402(83) and sets the method for measuring, calculating and reporting.

MEPC.414(84): IMO guidelines for CH4 and N2O measurement
Replaces MEPC.402(83)

EU

In the EU, the ETS has covered CH4 and N2O in CO2 equivalents since 1 January 2026, FuelEU Maritime has applied since 2025, and the EU MRV regulation governs monitoring and reporting.

EU ETS: CH4 and N2O included since 1 January 2026
FuelEU Maritime and EU MRV

Official sources

Methane and N2O reporting

What we measure

Methane slip, N2O and the rest of the exhaust.

Onboard, with the reference method

Onboard we measure total hydrocarbons (THC) and methane slip with a heated FID and a non-methane cutter, the reference method in MEPC.414(84), N2O by FTIR, and the usual gases alongside: NOx, CO, CO2 and O2.

Total hydrocarbons (THC)
Methane slip (heated FID with non-methane cutter)
N2O by FTIR
NOx, CO, CO2 and O2 at the same time

Real operating conditions

Everything is measured under real operating conditions, with calibration gases that come with certificates from accredited gas suppliers.

Real operating conditions onboard
Calibration gases with certificates from accredited suppliers

Actual methane slip instead of default values

FuelEU Maritime allows certified measured values, subject to the applicable requirements.

Default or actual value

Without measurements, a default methane slip value is used, for example 3.1% of the fuel mass for medium-speed Otto-cycle dual-fuel engines in FuelEU Maritime. Article 10.5 of FuelEU Maritime allows the company to use an actual value instead, certified by direct emission measurements. The European Commission set out how in its guidelines for actual methane slip from October 2025.

Actual value instead of the FuelEU default

Engine Load Monitoring

The measured values are combined with Engine Load Monitoring: the emission is measured at several loads, the engine load is logged through the year, and the result reflects how the vessel is actually operated. A vessel that runs at very low loads can come out higher than expected. Either way, the result is documented, and the Methane File is approved by the flag administration or a recognised organisation.

Measurements at several loads, including the lowest gas mode point
Engine Load Monitoring of the actual load profile
Methane File for approval by flag or recognised organisation

Official sources

Methane and N2O reporting

From measurement to documents

One measurement, one file.

The measurement is only the start. The results go into one file, and the same file serves the IMO guidelines and FuelEU Maritime.

The measurement

The results come from a measurement onboard following MEPC.414(84), with the load points agreed in the test plan.

Reference method: heated FID with non-methane cutter
Load points agreed in the test plan

One file, two names

MEPC.414(84) calls it the CH4 and/or N2O file. The European Commission calls it the Methane File and refers to the earlier guidelines, MEPC.402(83), which MEPC.414(84) replaces. The Commission asks for some additional information, for example allowable ranges for settings and the influence of ambient conditions.

CH4 and/or N2O file following MEPC.414(84)
Methane File with the additional EU information
Record book of changes to settings and components

Approval and Statement

The file is submitted to the Administration for verification. Under the Commission guidelines it is approved by the flag administration or an organisation recognised by it. After satisfactory verification, the Administration issues a Statement of emission values.

Submitted to the Administration for verification
Approved by the flag administration or a recognised organisation
Statement of emission values after approval

FuelEU Maritime and your verifier

The approved Methane File is referenced in the FuelEU Monitoring Plan, and the FuelEU verifier checks it together with Engine Load Monitoring of how the engine is loaded in service. The verifier verifies the shipping company, not ME-Tech. Use in EU MRV and ETS reporting should be agreed with your verifier.

Approved Methane File referenced in the Monitoring Plan
Engine Load Monitoring of the actual load profile
Verified by your FuelEU verifier

Methane and N2O reporting

How a campaign works

Simple for you, thorough for the vessel.

We plan with you

We plan the campaign with you, agree the test plan, bring the equipment onboard and measure at the agreed loads, including the lowest load at which gas fuel is used.

Test plan and load points agreed with you
Measurement onboard at several loads

Report and documentation

We deliver a clear report and the measurement documentation for the Methane File. Load logging and other steps towards the verifier can be added as an extra. It can be an add-on to a retrofit or class measurement, or a campaign on its own.

Report and documentation for the Methane File
Load logging and other steps as an extra

Want to know your real methane slip?

We plan the campaign around the vessel and its schedule.