The notion that liquefied natural gas (LNG) can lessen the climate effects of the maritime shipping industry is predicated on the notion that ships will eventually be able to transition to bio and e-LNG (often known as “renewable” LNG), which would result in minimal greenhouse gas (GHG) emissions.
In order for this to occur, renewable LNG must be available in quantities sufficient to fulfil future demand and its use must result in a considerable reduction in GHG emissions over the course of its life compared to fossil LNG. Policymakers, particularly those in the European Union, who have promised to decrease their GHG emissions by at least 55% below 1990 levels by 2030 (which is comparable to a 41% decrease from 2019 levels), must understand whether these assumptions are achievable.
Based on trends in fuel consumption, this analysis, which focuses on ships dealing with the European Union, forecasts a tripling of the demand for LNG as marine fuel between 2019 and 2030.
Additionally, it predicts that renewable LNG will cost seven times more in 2030 than fossil LNG, necessitating subsidies or other policies to promote its usage.
The figure below displays the well-to-wake (WTW) carbon dioxide equivalent (CO2e) emissions related to three 2030 scenarios in the European Union. Compare the emissions from using 100% fossil fuels in 2019 to the scenario in which ships use 100% renewable LNG in 2030 (far right, reflecting a €50 per gigajoule subsidy) (far left). As demonstrated, the use of renewable LNG could reduce WTW CO2e emissions by 38% based on 100-year GWP (CO2e100), but increase emissions by 6% based on 20-year GWP (CO2e20) due to the substantial near-term warming effects of methane.
Concentrating on the orange areas of the bars, even with 100% renewable LNG, methane emissions are double what they were in 2019 due mostly to methane slip from naval engines.
Methane slip from maritime engines must be almost eliminated, and methane leaks upstream must be drastically reduced, if renewable LNG is to make a substantial difference in attaining climate targets. It would also be necessary for methane losses from onboard fuel tanks and cargo tanks, which scientists are currently trying to properly estimate, to be very low.
Policymakers and stakeholders need to be aware that alternate fuels, such as green methanol and synthetic diesel, may have low life-cycle emissions without the methane issue.
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