Alternative Marine Fuels: A Comparative Analysis of Lower Heating Value, Specific Fuel Consumption, and Emission Performance in Relation to IMO 2050 Targets

Although maritime transport constitutes the backbone of global trade, the conventional fossil fuels used contradict the sector's sustainability goals regarding greenhouse gas emissions. This study provides a comparison of the energy content, the specific fuel consumption (SFC) values, and the carbon dioxide equivalent (CO₂e) emissions associated with the use of heavy fuel oil (HFO) and other alternative marine fuels including liquefied natural gas (LNG), methanol, ammonia and hydrogen. For each alternative fuel option this study will utilize a Triple-E class ultra-large container vessel as an example ship, and it will also include results of calculations using a 24-hour operational cycle. The findings indicate that HFO produces the highest daily CO₂e emissions in current operations. Conversely, while LNG significantly reduces total emissions due to its SFC advantage, it cannot completely eliminate potential climate impacts due to methane slip (CH₄ slip). Due to methanol's lower carbon content, methanol achieves around a 50% reduction in emissions as compared to HFO. Both ammonia and hydrogen are chemically carbon-free, therefore they will have no CO2 emissions generated at the tank-to-wake stage, but a life cycle assessment based on their production processes would be needed to provide an accurate comparison. In this study, hydrogen and ammonia are treated as zero-carbon fuels only from a tank-to-wake perspective because they do not generate direct CO₂ emissions during onboard use. However, their overall climate performance depends strongly on how they are produced. Fossil-based production pathways may result in substantial upstream emissions, whereas renewable pathways such as green hydrogen and green ammonia can provide significantly lower life-cycle emissions. The results indicate that shifting to transition fuels such as LNG and methanol are logical for the sector for the short term, but the technological, economic, and safety aspects of carbon-free fuels (NH3 and H2) need to be rapidly developed for the medium to long term. Therefore, this study provides a numerical reference that compares the energy and emission performance of alternative fuels within a holistic framework.