In a major study conducted by the Transport Emission Control Team at VTT Technical Research Centre of Finland, significant insights were gained relating to methane slip and other emissions from LNG-powered marine engines utilising the actual operation of a cruise ship.
The published study ‘Methane slip and other emissions from newbuild LNG engine under real-world operation of a state-of-the art cruise ship’, sheds light on the environmental impact of LNG as a shipping fuel, particularly focusing on its methane emissions together with other climate warming agents, including black carbon.
LNG has emerged as a promising fuel in the maritime industry, due to its lower CO2 emissions and reduced air pollutants, compared to conventional fuels.
However, concerns have been raised regarding the slip of unburned methane, a potent greenhouse gas, which can offset some of the environmental benefits of its use.
This study, utilising a cruise ship equipped with a low-pressure dual-fuel engine, provides valuable data on methane slip under real-world operating conditions, the authors claimed.
The investigation showed that methane slip varies significantly according to engine load and presented methane emission based on the actual engine load profile of the ship.
Some key findings from the study included:
- Lower Methane Emissions: The methane slip from the newly built engine was found to vary according to engine load, from 2.3-3.0 g/kWh high engine loads of 50-80% to 21 g/kWh at 12% load, positioning it at the lower end of values reported in the literature.
- CO2 Reduction: At load conditions of 50% and above, low methane slip values resulted in a 13-15% lower total CO2 equivalent emissions with LNG, compared to MGO. However, at lower load conditions, the situation is reversed.
- Real-world Load Profile: Analysis of the vessel’s engine load profile over eight months revealed that the majority of the vessel’s operation time (about 90%) occurred at engine loads higher than 40%. This indicates that the operational pattern of the engine can contribute to methane reduction efforts.
- Real-world methane slip: Based on the real-world load profile, the study developed a weighted emission factor for methane, resulting in 2.8 g/kWh for the specific ship. This represents 45% lower methane slip, compared to the default value from FuelEU Maritime regulation.
These findings underscore the potential for reducing methane emissions from LNG engines in marine operations. By optimising engine development and operational strategies, significant progress can be made toward achieving emissions reduction targets in the maritime sector, research co-operative Green Ray claimed.
Furthermore, the study highlights the importance of ongoing research and innovation in the maritime industry to address environmental challenges and promote sustainable practices.
With the maritime industry facing increasing pressure to meet emission targets, studies like this play a crucial role in advancing the understanding of the environmental implications of alternative fuels.
Green Ray said it aims to minimise methane slip from marine fuel. Three technologies will be developed to install on LNG engines of both existing and new ships.
The project is co-ordinated by VTT together with partners Chantiers de l’Atlantique, CMA Ships, Wärtsilä, Shell, DNV, the Finnish Meteorological Institute, MSC Cruises Management, and REVOLVE.
The five-year project, which began in June, 2022, has received a total grant of €7 mill from the European Commission within the new Horizon Europe research and innovation programme, addressing the topic of ‘Assessing and preventing methane slip from LNG engines in all conditions within both existing and new vessels (ZEWT Partnership)’.
