As the shipping industry embraces liquefied natural gas (LNG) as a transitional fuel on the road to the 2050 net-zero emissions target set by the International Maritime Organisation (IMO), understanding and mitigating methane slip—the unintended release of unburned methane during the combustion process—becomes imperative for vessel owners and operators. According to Clarksons Research, in the first half of 2024, alternative fuel investments accounted for about one-third of all newbuild orders and 41% of the tonnage ordered. Key orders included LNG (109 orders, 51 excluding LNG carriers), methanol (49 orders), ammonia (15 orders), LPG (42 orders), and hydrogen (4 orders).
This surge in LNG adoption is partly driven by uncertainty surrounding the availability and pricing of more sustainable future fuels, which has supported continued interest and investment in LNG as a viable bridging fuel for the maritime sector.
Methane, the primary component of LNG, is a potent greenhouse gas with a global warming potential (GWP) approximately 28-34 times greater than carbon dioxide (CO2) over a 100-year period. Although methane slip occurs in relatively small percentages, its substantial GWP makes it a significant environmental concern, particularly in the context of maritime decarbonization.
Juha Kytölä, Director of R&D and Engineering at Wärtsilä, emphasizes the critical nature of addressing methane slip: “Methane has a much higher global warming potential than CO2. Reducing methane emissions is not just an environmental necessity but also a strategic move to enhance the overall sustainability and efficiency of maritime operations. By tackling methane slip, we assist with decarbonization efforts while also improving the economic performance of shipping fleets.”
Methane slip in the maritime industry
Compared to traditional marine fuels, LNG offers notable environmental benefits, including lower CO2 emissions, virtually zero sulfur emissions, and a significant reduction in nitrogen oxides (NOx) by approximately 85%. Additionally, LNG infrastructure continues to expand with little sign of this slowing in the immediate future, providing a strong argument for ship owners weighing up the practicalities of potential emissions reduction pathways for vessels.
However, the long-term viability of LNG as a marine fuel is contingent upon effectively addressing methane slip. Elevated methane emissions undermine the environmental advantages of LNG, posing a challenge to the industry's decarbonization objectives. Consequently, reducing methane slip is not only an environmental imperative but also a matter of operational efficiency and cost-effectiveness for ship owners.
Addressing methane slip requires an approach that encompasses advancements in engine technology, combustion efficiency, and fuel management. Leading the charge is Wärtsilä, a prominent player in marine engine manufacturing, which has developed innovative solutions to minimize methane emissions.
Wärtsilä’s NextDF technology enhances combustion efficiency, ensuring more complete fuel burn and thereby reducing methane slip and NOx emissions significantly. “By optimizing fuel distribution within the combustion chamber, NextDF ensures that each cylinder operates at peak efficiency, drastically minimizing the chances of unburned methane escaping into the atmosphere. This not only helps in meeting regulatory standards but also significantly enhances the economic viability of using LNG as a marine fuel,” Kytölä explains.
The role of bio-LNG in future fuels
While LNG serves as an effective transitional fuel, the maritime industry is also exploring the potential of Bio-LNG to further mitigate its carbon footprint. Bio-LNG, derived from sustainable biomass sources, offers a drop-in solution compatible with existing LNG infrastructure and engines. This compatibility facilitates a seamless transition to lower-carbon operations without necessitating significant retrofits or additional investments.
Kytölä continues: “Ship engines that use LNG can later transition to biofuels, such as biogas, without needing major retrofits. This flexibility is crucial for the maritime industry’s long-term decarbonization strategy, as it allows for incremental improvements and the integration of more sustainable fuel options as they become available – and available in the quantities and locations required.”
The adoption of Bio-LNG is projected to grow, with estimates suggesting it could meet up to 3.1% of the shipping sector’s energy demand by 2030, increasing to 12.6% by 2050. When blended with fossil LNG, Bio-LNG’s contribution to energy demand coverage expands substantially, enhancing its viability as a sustainable fuel option. The flexibility of LNG engines to switch to Bio-LNG without major modifications positions Bio-LNG as a critical component in the long-term decarbonization strategy of the maritime industry.
Adding methane slip into the equation
The development of accurate methane emissions measurement and reporting protocols is crucial for establishing transparent and reliable emissions inventories. Enhanced measurement techniques will enable more precise monitoring and management of methane slip, facilitating better regulatory compliance and informed decision-making.
“Looking ahead, the maritime industry is likely to embrace a multi-faceted approach to reducing greenhouse gas emissions – not just focus on carbon emissions. This requires not only advancing engine technologies and adopting cleaner fuels but also implementing operational strategies that optimize vessel performance and fuel efficiency. Hybrid solutions, retrofittable engine upgrades, and the integration of emerging fuel technologies like ammonia and methanol further diversify the toolkit available to ship operators striving for sustainability and all contribute towards achieving net zero,” Kytölä concludes.
