Assessment of suitable hydrogen carriers for maritime transport based on energy, environmental, geopolitical and cost implications

This study evaluates the energy, environmental, and economic performance of transporting hydrogen by different carriers, namely fossil natural gas (used as reference), substitute natural gas, hydrogen, and ammonia. Potential trade routes between renewable energy-rich exporting countries (such as Morocco, Norway, Brazil, and Australia) and Italy have been considered and geopolitical implications have been addressed by multicriteria analysis. The supply chain analysis encompasses carrier production, preparation, transportation and reconversion to hydrogen. In terms of energy efficiency, H2 is strongly affected by the travel distance, reaching a maximum efficiency of 46% and a minimum of 28% for shorter and longer voyages, respectively. On the contrary, ammonia and fossil natural gas keep a steadier efficiency range (38–45% for ammonia and 30–34% for fossil natural gas) in all routes. No emissions are produced by the hydrogen and ammonia pathways, while substitute natural gas presents negative values (􀀀 7.46 kgCO2/kgH2) that enable carbon credits. As for the costs, ammonia and fossil natural gas show comparable product costs (4.5–6.2 €/kgH2), whereas the substitute natural gas is the most expensive carrier on most routes (up to 10.5 €/kgH2). Sensitivity analyses highlight that the choice of hydrogen carrier and exporting country is strongly influenced by the renewable energy costs, while forecast analysis using multicriteria evaluation suggests that transporting ammonia or natural gas from Norway and Australia represent the most profitable scenario.