The verification work was conducted on the vessels including SALAMANCA , SANTONA, SAINT-MALO, and GUILLAUME DE NORMANDIE. For the SALAMANCA, the methane emissions monitoring campaign was conducted over a twelve-month period on the Rosslare–Bilbao and Rosslare–Cherbourg routes. The results of an atmospheric emissions study were published in the Journal of Marine Science and Engineering.

The findings demonstrate that the vessel’s average annual methane slip rate is largely reduced compared to the default values of up to 3.1% currently referenced in European regulatory frameworks and international guidelines issued by the International Maritime Organization (IMO). These results underline the importance of basing regulatory reporting on measured and verifiable data reflecting real operating conditions.

In accordance with IMO Resolution MEPC.402(83) and the FuelEU Maritime Guidelines, the use of actual methane slip values requires the development of a comprehensive methane emissions documentation package. This documentation package, prepared by the company intending to use actual tank-to-wake methane slip emissions, includes a methane emissions file for each relevant engine, a methane record book, and additional methane-slip-related information such as the Engine Load Monitoring (ELM) procedure used for the FuelEU Maritime report. The documentation must be supported by onboard exhaust gas measurements and robust monitoring methodologies. 

BV reviewed the documentation required under IMO Resolution MEPC.402(83) and the FuelEU Maritime Guidelines. Following this process, the methane files were approved by the French Flag Administration, which issued a Form of Statement confirming the engine-weighted verified methane emissions values. This approval enables Brittany Ferries, together with the implementation of the ELM procedure, to report measured methane emissions within the MRV and FuelEU Maritime frameworks.

With maritime transport now included in the European Union Emissions Trading System (EU ETS), and with FuelEU Maritime progressively entering into force, methane slip has become a material parameter in greenhouse gas intensity calculations and associated compliance exposure. The ability to substitute conservative default values with verified measured data provides LNG-fueled ship operators with a transparent and technically robust basis for demonstrating their actual environmental performance.

David Barrow, SVP for Western Europe and Americas at Bureau Veritas Marine & Offshore, said: “This collaboration demonstrates how independent measurement and verification can enhance the accuracy of regulatory reporting while reinforcing transparency and accountability in greenhouse gas emissions. By supporting the recognition of measured methane performance, we are helping ensure that the real environmental gains achieved by LNG-fueled vessels are properly reflected within evolving regulatory frameworks.”

Bertrand Crispils, Head of Energy Transition at Brittany Ferries, said: “The achievement of this work is another key step on our energy transition journey as we look to the future and introduce greener, more energy-efficient vessels and fuels. It clearly shows how technical expertise can allow us to unlock improvements in environmental performance and how flexibility in regulations provides shipowners with the means to find innovative, creative and pragmatic solutions that are beneficial to all. This project was the fruit of great teamwork between scientist, shipowner, certifier, and manufacturer and we thank ESTACA, Bureau Veritas and Wartsilä for their expertise and active support.”

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