Climate NGOs call for regulators to rethink LNG emissions rules

As NGOs push regulators for more stringent pollution measuring capabilities for LNG-powered ships, at least one prominent naval architect has argued that the complex the issues involved require careful consideration.

Currently the EU and IMO use methane slip emission factors that are provided by a few studies that used a mix of lab tests, engine manufacturers data and a limited amount of onboard testing, according to the International Council on Clean Transportation (ICCT).

LNG powered vessels suffer from unburnt methane emissions from the exhausts of both main and auxiliary engines. Actual operational emissions for some low pressure four-stroke LNG engines have been found to be around double the figures published by engine manufacturers.

Korean NGO Solutions For Our Climate (SFOC) lead on the energy supply chain Rachel Eunbi Shin, said: “Engine manufacturers and classification societies claimed in 2014 that methane slip was 'practically eliminated' in modern engines”, yet slip rates continue to rise, “raising serious credibility concerns”.

According to Shin it is crucial to monitor individual ships to get a clearer picture of their operational emissions.

“We've discovered significant discrepancies between manufacturer-claimed emissions and real-world performance - much like the automotive sector's emissions scandal. Operational profiles vary dramatically between vessels, particularly with slow steaming becoming more common to meet CII regulations,” she explained.

Related:Methane emissions measurement standards needed as penalties loom

NGOs, including SFOC, are calling for reformed certification testing that includes low-load operations, onboard continuous monitoring systems for accurate real-time data, load-based calculations as a simplified but acceptable alternative, and drone-based spot checks for verification.

ICCT director of marine Bryan Comer pointed out that there are few continuous emissions monitoring programmes that give long term data, sensitive to engine loads, “with lower loads causing higher methane slip emissions”.

Variations in loads will significantly change the actual emissions from vessels which would see the GHG costs increase significantly and could alter the decision-making for shipowners that see LNG as a transitional fuel.

ICCT conducted what it said is the largest study of its kind so far, though Comer admits it is not a large data sample, in co-operation with the measurement data service provider Explicit ApS, and the Netherlands Organization for Applied Scientific Research (TNO).

The study highlights the deficiencies in the current calculations of methane emissions from shipping, while also offering an alternative, more accurate methodology.

In what Comer described as a “simplified approach,” the ICCT proposes the use of engine monitoring data which is already collected by each vessel.

ICCT has approached both the EU and IMO with its findings and its solutions: “There are no guidelines for FuelEU as yet, but we are hopeful that we can get guidelines for 2026, when FuelEU payments for LNG are introduced,” said Comer.

The same methodology is being discussed at IMO.

In its report on the study, based on 22 measurements from 18 vessels, the group’s findings showed that low-pressure, dual-fuel, four-stroke (LPDF 4-stroke) engines, had methane slip at an average 6.42% and a median of 6.05%, “more than twice as much methane slip than assumed by the EU and over 80% more than assumed by the IMO.”

Six measurements at or above a combined engine load of 50%, registered 6.07% average and 6.59% median emissions.

“Methane slip was greater than the EU assumption of 3.1% in 77% of the measurements. These same 77% of measurements were also greater than the IMO assumption of 3.5% methane slip,” said the joint report.

However, vessels with LPDF 2-stroke main engines and LPDF 4-stroke auxiliary engines (L2L4) emitted the least methane slip, averaging of 2.50% methane slip across all engine loads and 1.58% at more than 10% engine load; Median values were 1.47% and 1.35%, respectively.

Measurements on 2-stroke high pressure dual fuel engines (HPDF) main engines combined with LPDF 4-stroke auxiliaries were limited to two readings with a ship operating at below 10% load, “when we assume that only the LPDF 4-stroke auxiliary engines were operating on LNG,” which recorded 3.47% and 6.12% methane slip.

Other measurements were performed at 36% main engine load, when both the HPDF main engine and LPDF 4-stroke auxiliary engines were expected to be operating on LNG, resulting in 2.69% methane slip.

For ships with lean-burn spark-ignited (LBSI) engines, that do not have LNG-fuelled auxiliary engines, measurements from two ships were calculated at 2.41% and 1.85% at 36% and 55% main engine load.

“This is lower than the EU and IMO assumption of 2.6% methane slip, but we do not have enough data to determine whether the default factor for LBSI engines is reasonable,” said the report.

One naval architect, who preferred to remain anonymous but who is closely watching the discussions, told Seatrade Maritime News: “You have to be careful with percentages, 6% of a low load means that you are burning far less fuel, while 2% of a high load would be a percentage of a much higher fuel burn,” she said.

Moreover, newer vessels would be designed to operate at lower speeds, so the engine choice would be different, if that engine was then optimised to operate at a lower load it could encourage regulators to stipulate a minimum engine load to reduce methane emissions, manufacturers could then optimise their designs for that lower load, so if higher speeds are required the emissions would increase again.

According to the naval architect, there is a need for a large data sample in order that regulators can stipulate the most appropriate optimisation point. While there is not enough data from engine monitoring, which she said only measures the length of time an engine is operating and not the load at which it is set.