This report is a background report to the MarE-Fuel project financed by the Maritime Fund and the Lauritzen Fund. Partners of the project has been DTU, Anker Invest, Mærsk Line, Copenhagen Economics, OMT and DFDS. In the report, potential decarbonization roadmaps or pathways for the maritime industry are presented, as well as the methodology of deriving them. Different future fuels and their emissions are highlighted. In addition, biomass availability plays an essential role in climate mitigation efforts towards net-zero by 2050, and thus we examined different biomass availability scenarios alongside greenhouse-gas emissions cap scenarios. The assumptions related to the underlying emissions can be found in the first chapter of the report. Besides the underlying emissions for a decarbonized maritime industry, the ship stock and the underlying transport demand play an essential role for a future decarbonized maritime industry. In the second chapter of the report, we address this issue by explaining how ship stock and shipping demand have been incorporated into the model. Finally, we present the optimization ship stock model developed to generate roadmap scenarios. We show the objective function and the underlying constraints of the model. The results of this work are presented and discussed. We also show some sensitivity analysis, which will shed light on the relevant parameters for the futureof the maritime industry. Our main findings can be found in the end of the report.