Comparative life cycle assessment of liquid organic hydrogen carriers for green hydrogen transport

As Europe transitions towards a low-carbon energy system, the need for reliable, scalable, and sustainable hydrogen storage and transport solutions is increasing. Liquid organic hydrogen carriers (LOHCs) have emerged as a promising option due to their compatibility with existing energy infrastructures and favourable safety properties. A cradle-to-gate life cycle impact assessment was conducted to evaluate and compare the environmental impacts of six LOHCs: toluene, benzyltoluene, dibenzyltoluene, N-ethylcarbazole, 2-(n-methylbenzyl)pyridine, and naphthalene. Green hydrogen production and hydrogenation occur in Spain. The loaded carrier is transported by cargo ship to Germany, where dehydrogenation takes place. Midpoint results for 16 impact categories were assessed and interpreted. Dibenzyltoluene showed lower impacts in most categories, including global warming potential, while N-ethylcarbazole exhibited comparatively better performance in toxicity-related indicators. Sensitivity scenarios and Monte Carlo uncertainty analysis were implemented to evaluate the robustness of the results. Although the main comparative trend persisted across the scenarios, differences were generally moderate and influenced by system assumptions, indicating that the environmental performance of the LOHCs is largely driven by upstream processes and energy supply conditions.