Comparative cradle-to-application life cycle assessment of hydrogen pathways: Role of ethanol purity and end-use efficiency in SOFCs and hydrogen engines

This study presents a cradle-to-application life cycle assessment (LCA) of hydrogen energy systems, evaluating ethanol as a renewable hydrogen carrier and solid oxide fuel cells (SOFCs) as high-efficiency end-use technologies. Fossil-based pathways (grey and blue hydrogen via steam methane reforming, and coal gasification) are compared with renewable ethanol-derived pathways using corn and municipal solid waste (MSW), including an integrated ethanol-fed SOFC configuration. Environmental impacts are quantified across seven midpoint categories using OpenLCA, Ecoinvent v3.12, and ReCiPe 2016 Midpoint (H), with results normalized to both hydrogen production and useful energy delivered in SOFCs and hydrogen internal combustion engines (H 2 -ICE). Results show that end-use efficiency is a dominant driver of life cycle performance, with SOFCs reducing global warming potential (GWP) by 35–45 % compared with H 2 -ICE across all pathways. Among renewable options, MSW-derived ethanol exhibits the lowest impacts, achieving 0.89 kg CO 2 -eq/MJ in SOFC systems and 0.72 kg CO 2 -eq/MJ in integrated ethanol-fed SOFC configurations. Ethanol purity shows a non-linear effect, where moderate dilution (50–75 vol %) minimizes impacts by reducing dehydration energy demand while maintaining reforming efficiency, whereas excessive dilution (25 vol %) introduces additional thermal penalties. Integrated ethanol-fed SOFC systems further reduce GWP by 9–13 % by eliminating hydrogen purification, compression, and transport stages. These results highlight the importance of jointly optimizing feedstock selection, ethanol purity, and end-use efficiency. Waste-derived ethanol and integrated SOFC systems offer a promising pathway for low-emission and resource-efficient hydrogen energy applications, particularly in emerging distributed energy contexts such as data centers and AI-driven electricity demand, where high-efficiency and low-emission systems are increasingly required.