Measuring methane emissions from LNG engine utilizing different devices

Liquified natural gas (LNG) is considered as one fuel pathway in decarbonization of the maritime industry and meeting emission targets. Lower sulphur and nitrogen oxides, together with lower particulate emissions are reported with LNG use compared to diesel use. Moreover, CO2 emissions are lower as well but there is an issue with the methane slip with the most popular LNG use in low-pressure dual fuel engines. The methane being a strong greenhouse gas its minimization is needed.
Globally, methane is considered by the International Maritime Organization (IMO) in the draft guidelines on life cycle GHG intensity of marine fuels (IMO 2023). European Union has introduced two regulations to mitigate the methane emitted from marine engines. Maritime transport will be part of the EU Emissions Trading Scheme (ETS) from the beginning of 2024. In the beginning, ETS will consider emitted CO2 but in 2026, methane will be included in the emission calculation and operators need to buy the allowances for all GHG emissions emitted (European Commission, 2024). Moreover, FuelEU Maritime requires ship owners to report their methane emissions and include it in fuel GHG intensity calculation. In the regulation, a predefined methane slip value as percentage of consumed fuel is assigned for each LNG engine technology. Alternatively, the ship owners have a possibility to utilize methane slip value verified by a direct measurement from the engines. There will be a significant financial incentive to reduce GHG emissions via ETS allowance costs and compliance balance penalty of FuelEU maritime.
So far, there are no specific guidelines for methane slip measurement and there is quite a variety of devices for methane measurement with different methodologies. In present study we use five different devices to study the methane emission of a state-of-the-art LNG-fueled marine engine as a representative of a near future methane emission levels. Moreover, we also report measurements with a methane abatement catalyst developed to decrease methane levels further and to study the performance of the methane measurement equipment at lowest methane levels expected in the future.