SEA-LNG Disputes Methodology of LNG Bunker Methane Emissions Study

The use of fossil LNG as a bunker fuel remains a contentious issue. File Image / Pixabay

LNG bunker industry body SEA-LNG has criticised a recent study that suggested methane emissions from ships running on fossil gas were higher than regulators assumed.

As Ship & Bunker reported on Tuesday, the International Council on Clean Transportation released a new report last month analysing methane emissions from LNG-fuelled ships in Europe and Australia.

The report found methane slip in the plumes of 18 ships with LPDF 4-stroke engines at 6.4% on average, compared to the 3.1% assumed in EU regulations and 3.5% assumed by the IMO.

Methane emissions have a significant impact on global warming, and industries around the world are working on ways of minimising them.

SEA-LNG released a press statement on Thursday saying the study 'suffers from a range of significant methodological limitations'.

The release makes the following objections to the methodology used:

• The use of an experimental airborne measurement methodology which is not verified against industry standards, nor calibrated against on board measurements.
• The fact that the analysis is based on a limited number of vessels, using older low-pressure engine technologies, in particular low-pressure 4-stroke engines. There are very few measurements from the high-pressure dual fuel technologies which have virtually eliminated methane slip and which account for more than half the LNG-fueled vessels in the new build order book.
• The inability to distinguish between individual onboard emissions sources which makes it impossible to quantify levels of methane slip associated with specific engine technologies.
• Measurements were focused on atypical vessel operating conditions and engine load factors. The study focuses on exhaust emissions from ships during port stays and manoeuvring in and out of ports, representing less than 10% of ships' operational conditions. Related to this, the majority of observations were taken with engine loads of around 0-30%. Main engines are designed to run at loads of between 60% and 100%, the range at which they operate for the majority of voyage time. At these loads, engines show the lowest levels of methane slip.

"The ICCT FUMES work highlights emissions challenges that have long been known and are being actively addressed by the maritime industry and equipment manufacturers of all types," SEA-LNG said in the statement.

"It is essential to view the findings of studies like the FUMES project in the broader context of the full-scale operational conditions of the ships, not just in ports and near-shore operations.

"The advancement of technologies for both low- and high-pressure combustion should be recognised, and analysis should encompass both legacy and new technologies."

The use of fossil LNG as a bunker fuel remains a contentious issue, with opponents characterising it as just another fossil fuel that distracts from better means of decarbonising shipping, while supporters see it as an early stage towards using lower-carbon bio- or synthetic LNG in future.