A comparative life cycle assessment of marine fuels: liquefied natural gas and three other fossil fuels

Air emissions from shipping have received attention in recent years and the shippingindustry is striving for solutions to reduce their emissions and to comply with stricter regulations.Strategies to reduce emissions can consist of a fuel switch, engine changes, or end-ofpipetechnologies, but they do not necessarily imply reduced life cycle emissions. The presentpaper assesses the environmental performance of marine fuels from well-to-propeller using lifecycle assessment (LCA). Four fossil fuels are compared: heavy fuel oil (HFO), marine gas oil,gas-to-liquid (GTL) fuel, and liquefied natural gas (LNG), combined with two exhaust abatementtechniques: open-loop scrubber and selective catalytic reduction. LNG and other alternativesthat comply with the SECA 2015 and Tier III NOx requirements give decreased acidification andeutrophication potentials with 78–90 per cent in a life cycle perspective compared with HFO. Incontrast, the use of LNG does not decrease the global warming potential by more than 8–20 percent, the amount depending mainly on the magnitude of the methane slip from the gas engine.None of the fossil fuels scrutinized here would decrease the greenhouse gas emissions significantlyfrom a life cycle perspective. The study supports the need for LCA when evaluating theenvironmental impact of a fuel change, e.g. it is found that the highest global warming potentialduring the whole life cycle is connected to the alternatives with GTL fuel