Recent research by the Transport Emission Control Team at VTT Technical Research Centre of Finland has unveiled crucial insights into how engine load affects methane slip and other emissions from LNG engines aboard a modern cruise ship. This study highlights the importance of operational patterns in mitigating the environmental impact of LNG as a marine fuel.
The study focuses on the Wärtsilä 46DF engine installed on the MSC World Europa, a state-of-the-art cruise ship built in 2022. It documents real-world emissions during various operational phases, including steady cruising and port maneuvers. Notably, methane slip was found to vary significantly with engine load, underscoring the engine’s performance dynamics.
With LNG’s lower carbon emissions compared to traditional fuels, the study emphasizes that maintaining engine loads above 50% can lead to substantial reductions in total CO2 equivalent emissions. “Our findings indicate that at loads of 50% and above, the methane slip is minimized, resulting in 13-15% lower total emissions compared to MGO,” stated Dr. Kati Lehtoranta, a co-author of the study. In contrast, significantly lower loads tend to increase methane emissions, demonstrating the critical role of operational efficiency.
The researchers observed that the MSC World Europa operates primarily above 40% engine load—approximately 90% of the time—which maximizes the benefits of using LNG. They calculated a weighted methane emission factor of 2.8 g/kWh, significantly lower than regulatory defaults, showcasing the potential for optimizing engine operations to achieve better environmental outcomes.
Further, the study noted that while LNG operation produces negligible particle emissions, black carbon levels were markedly lower than those generated by MGO, reinforcing LNG’s advantages at higher loads. However, it cautioned that the environmental benefits diminish at lower loads, where unburned methane can counteract gains in CO2 and black carbon emissions.
These findings, part of the GREEN RAY project, stress the importance of operational profiles in reducing methane slip and enhancing the sustainability of LNG as a maritime fuel.
This article was originally published in The Motorship, October 2024.
