The goal of this study is to evaluate the life cycle performance of two alternative pathways to biofuels in the shipping industry: the 'diesel route' and the 'gas route'. The diesel route comprises of a shift from heavy fuel oil to marine gas oil and then a gradual shift to biodiesel, whereas the gas route comprises of a shift to liquefied natural gas and then a gradual shift to liquefied biogas. The two routes are assessed in a case study for the ferry traffic between the Swedish mainland and the island Gotland. Life cycle assessment (LCA) is used to evaluate the environmental performance with the functional unit chosen to be one year of ro-pax ferry service, including both passenger and goods transportation. The gas route is indicated to have better overall environmental performance than the diesel route. Furthermore, use of biofuels is illustrated as one possible measure to decrease the global warming impact from shipping, but to the expense of greater environmental impact for some other impact categories. As an example, the global warming potential (GWP(100)) was shown to decrease with the use of biofuels in this study, while the eutrophication potential and the primary energy use increased. (C) 2012 Elsevier Ltd. All rights reserved.