In recent years, the International Maritime Organization agreed on aiming to reduce shipping’s greenhouse gas emissions by 50% with respect to 2009 levels. Meanwhile, cruise ship tourism is growing at a fast pace, making the challenge of achieving this goal even harder. The complexity of the energy system of these ships makes them of particular interest from an energy systems perspective. To illustrate this, we analyzed the energy and exergy flow rates of a cruise ship sailing in the Baltic Sea based on measurements from one year of the ship’s operations. The energy analysis allows identifying propulsion as the main energy user (46% of the total) followed by heat (27%) and electric power (27%) generation; the exergy analysis allowed instead identifying the main inefficiencies of the system: while exergy is primarily destroyed in all processes involving combustion (76% of the total), the other main causes of exergy destruction are the turbochargers, the heat recovery steam generators, the steam heaters, the preheater in the accommodation heating systems, the sea water coolers, and the electric generators; the main exergy losses take place in the exhaust gas of the engines not equipped with heat recovery devices. The application of clustering of the ship’s operations based on the concept of typical operational days suggests that the use of five typical days provides a good approximation of the yearly ship’s operations and can hence be used for the design and optimization of the energy systems of the ship.

Air emissions from shipping have received attention in recent years and the shipping industry 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-of-pipe technologies, but they do not necessarily imply reduced life cycle emissions. The present paper assesses the environmental performance of marine fuels from well-to-propeller using life cycle 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 abatement techniques: open-loop scrubber and selective catalytic reduction. LNG and other alternatives that comply with the SECA 2015 and Tier III NO _x requirements give decreased acidification and eutrophication potentials with 78–90 per cent in a life cycle perspective compared with HFO. In contrast, the use of LNG does not decrease the global warming potential by more than 8–20 per cent, 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 significantly from a life cycle perspective. The study supports the need for LCA when evaluating the environmental impact of a fuel change, e.g. it is found that the highest global warming potential during the whole life cycle is connected to the alternatives with GTL fuel.