The paper "Comparative analysis among different alternative fuels for ship propulsion in a well-to-wake perspective" by Giorgio Zamboni, Filippo Scamardella, Paola Gualeni, and Edward Canepa explores the potential of alternative fuels to reduce Green House Gas (GHG) emissions in the shipping sector. The study focuses on evaluating the Well-to-Wake (WtW) CO₂ equivalent emission factors for LNG, methanol, and ammonia, considering both fossil and renewable production pathways. The authors highlight the importance of a comprehensive approach that includes the entire lifecycle assessment (LCA) to effectively limit global warming. The paper begins with an overview of the maritime sector's contribution to GHG emissions and the International Maritime Organization's (IMO) ambitious goals for emission reduction. It discusses various technical measures and solutions to decarbonize the fleet, including hydrodynamics, logistics, digitalization, renewable energy sources, and carbon capture and storage (CCS). The selection of alternative fuels such as biofuels, LNG, methanol, ammonia, and hydrogen is discussed, along with their production pathways and environmental impacts. A case study of a cruise ship is presented to compare the performance of alternative fuels produced from fossil or renewable sources under two typical cruise profiles. The results, based on the Carbon Intensity Indicator (CII), confirm that the WtW approach highlights the significant potential of green fuels in reducing GHG emissions. The study concludes that while methanol and ammonia have higher GHG emission factors, especially for the fossil pathways, their use in green production paths can significantly reduce emissions. The paper also emphasizes the need for further research to reduce uncertainties and improve the reliability of emission factor data.The paper "Comparative analysis among different alternative fuels for ship propulsion in a well-to-wake perspective" by Giorgio Zamboni, Filippo Scamardella, Paola Gualeni, and Edward Canepa explores the potential of alternative fuels to reduce Green House Gas (GHG) emissions in the shipping sector. The study focuses on evaluating the Well-to-Wake (WtW) CO₂ equivalent emission factors for LNG, methanol, and ammonia, considering both fossil and renewable production pathways. The authors highlight the importance of a comprehensive approach that includes the entire lifecycle assessment (LCA) to effectively limit global warming. The paper begins with an overview of the maritime sector's contribution to GHG emissions and the International Maritime Organization's (IMO) ambitious goals for emission reduction. It discusses various technical measures and solutions to decarbonize the fleet, including hydrodynamics, logistics, digitalization, renewable energy sources, and carbon capture and storage (CCS). The selection of alternative fuels such as biofuels, LNG, methanol, ammonia, and hydrogen is discussed, along with their production pathways and environmental impacts. A case study of a cruise ship is presented to compare the performance of alternative fuels produced from fossil or renewable sources under two typical cruise profiles. The results, based on the Carbon Intensity Indicator (CII), confirm that the WtW approach highlights the significant potential of green fuels in reducing GHG emissions. The study concludes that while methanol and ammonia have higher GHG emission factors, especially for the fossil pathways, their use in green production paths can significantly reduce emissions. The paper also emphasizes the need for further research to reduce uncertainties and improve the reliability of emission factor data.