Classification society ClassNK has published updated guidance on European Union environmental regulations affecting shipping, including new information on the use of measured methane slip emission factors for LNG-fuelled vessels.

The organisation announced on 27 February the release of the third edition of its FAQ document on the EU Emissions Trading System (EU ETS) for Shipping and the fifth edition of its FAQ document covering FuelEU Maritime.

Both regulations apply to ships with a gross tonnage above 5,000 that call at EU ports. The EU ETS was expanded to include the maritime sector in 2023 and has been in force since 1 January 2024, while FuelEU Maritime entered into force in October 2023 and has been in force since 1 January 2025.

The updated FAQs explain how operators of LNG-fuelled vessels can apply measured methane slip emission factors instead of the default values currently used. The clarification follows guidance issued by the European Commission in October 2025 concerning the reporting and verification of actual tank-to-wake methane slip emission factors.

ClassNK explains that, depending on engine type, measured methane slip values may be lower than the default factors applied under the regulations, which could reduce calculated greenhouse gas emissions.

The classification society noted that certain aspects of FuelEU Maritime implementation remain unclear and said the information provided in the FAQs reflects the guidance available from the European Maritime Safety Agency and the EU as of February 2026.

The documents can be accessed on the ClassNK website under the certification services section for EU MRV, UK MRV, EU ETS, and FuelEU Maritime. Supporting materials explaining the application of measured methane slip values are also available on the same page.

ClassNK said the publications form part of its Transition Support Services, which aim to help maritime stakeholders understand and respond to evolving environmental regulations.