Methane slip from ships measured at double that assumed by EU regulations

As we have discussed in the past, in converting their fleets to liquified natural gas (LNG), the shipping industry are reducing their NOx and S02 emissions but at the expense of pumping methane into the atmosphere.

LNG consists primarily of methane, an extremely powerful greenhouse gas, responsible for about 30% of the heating effect of climate change. It leaks into the atmosphere through the entire lifecycle of fossil LNG, and the leakage is particularly bad from the type of engines used by cruise ships. 

The FUMES (Fugitive and Unburned Methane Emissions from Ships) project has now published what they believe to be the  most comprehensive dataset of real-world methane emissions from LNG-fueled ships to date.

The research was led by the International Council on Clean Transportation (ICCT) who measured emissions using three different approaches: plume, onboard, and fugitive. 

In the plume campaign, drones and helicopters were used to sample methane in exhaust plumes of 34 ships fuelled with LNG sailing near the coasts of the Netherlands, Denmark, Belgium, and Australia over the course of 2022.

The onboard campaign, involved measuring methane in the exhaust stack, as well as in the plume, from an LNG-fueled ferry sailing between Finland and Sweden in Spring 2023.

The fugitive campaign involved measuring emissions from three LNG tankers while they were unloading cargo at a European LNG terminal in 2022.

The research found that real-world methane slip measured in the plumes of 18 ships using the most common type of LNG marine engine (LPDF 4-stroke) averaged 6.4%, more than twice as much methane slip as assumed by the EU (3.1%) and over 80% more than assumed by the UN International Maritime Organization (3.5%).

The report’s recommendations include:

  • EU and IMO policymakers should consider increasing the default methane slip value for LPDF 4-stroke engines to at least 6%.
  • Ship owners that do not wish to take the default values can certify that the engines used on their ships emit less
    than the default methane slip values.
  • EU policymakers should consider requiring LNG-fueled ships to plug into shore power or otherwise eliminate their at-berth emissions to avoid using LPDF 4-stroke auxiliary engines.
  • EU policymakers should consider requiring monitoring, reporting, and verification of methane emissions at LNG storage and refueling points
  •  IMO policymakers should consider adjusting how emissions at each engine load test point are weighted to more accurately reflect real-world operations.





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