LNG and Cruise Ships, an Easy Way to Fulfil Regulations—Versus the Need for Reducing GHG Emissions

Elizabeth Lindstad,Agathe Rialland

doi:10.3390/su12052080

Abstract

Liquified natural gas (LNG), with its low sulphur content, its favorable hydrogen-to-carbon ratio, and the lower nitrogen oxide emission when combusted compared to conventional fuels, fulfils all International Maritime Organization (IMO) air emission regulations. For the cruise industry, with their large number of customers and their high public visibility, LNG has therefore become a tempting option for new cruise ships. However, larger well-to-tank (WTT) emissions for the LNG supply chain as well as un-combusted methane (CH4) from the ship’s engine might more than nullify any greenhouse gas (GHG) gains. Previous studies have shown very different GHG impacts from the use of LNG as a ship fuel. With climate change potentially being the largest threat to mankind, it is important that decisions with an impact on future GHG emissions are based on the best available knowledge within a sector and across sectors. The motivation for this study has therefore been to establish comparable GHG estimates for well-to-wake (WTW) emissions for LNG and traditional fuels in a transparent way. The results show that there is a need for adopting policies that can reduce the broader GHG emissions of shipping instead of CO2 only, including the well-to-tank emissions of ship fuels. If not, we might end up with a large number of ships with GHG savings on paper only, while the real GHG emissions increases.

Highlights

Due to its favorable hydrogen-to-carbon ratio, liquified natural gas (LNG) is often seen as a tempting option to reduce maritime greenhouse gas (GHG) emissions
With climate change potentially being the largest threat to mankind, as stated in the Paris agreement adopted at the COP21 in 2015 [10], it is important that decisions with impact on future GHG emissions are based on best available knowledge within a sector and across sectors
For a 100 year time horizon, the figures from DNV-GL (2019) [35] and Thinkstep (2019) [31] indicate a small GHG reduction with LNG, i.e., 0–10%. This contrasts with ICCT (2020) [9], which indicates that GHG emissions with LNG could increase by 16%, with this study indicating an increase of up to 10%, and with Lindstad (2019) reporting a GHG emission increase of 6%

Summary

Introduction

Due to its favorable hydrogen-to-carbon ratio, liquified natural gas (LNG) is often seen as a tempting option to reduce maritime greenhouse gas (GHG) emissions. The advantage of LNG was its very low sulphur content and the reduction in nitrogen oxide and particles emitted when combusted, compared to conventional fuels. The first regulation of sulphur oxides (SOx) and nitrogen oxides (NOx) emissions came in 1997, when the International Maritime Organization (IMO) added Annex VI to the International Convention for the Prevention of Pollution from Ships [1]. The same year, GHG emissions came on the IMO agenda as a result of the Kyoto Protocol [2]. It took IMO another 14 years before the regulation of GHG through the Energy Efficiency Design Index (EEDI) was adopted as part of the MARPOL Convention by the Resolution MEPC.203 (62) [3]. The EEDI sets ship-specific limits for CO2 emissions for ships built from 2013 and onwards

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Results

Conclusion