Beyond Decarbonization: A Comparative Life Cycle Assessment of the Water-Energy Nexus in Green Hydrogen Production

Green hydrogen is pivotal for the global energy transition; however, its environmental footprint extends beyond carbon emissions, particularly concerning water consumption in water-scarce regions. This study presents a cradle-to-gate Life Cycle Assessment (LCA) of green hydrogen production via Polymer Electrolyte Membrane (PEM) electrolysis, focusing on the trade-offs between Global Warming Potential (GWP) and Water Scarcity Footprint (WSF).We modeled three scenarios based on different renewable energy sources (solar PV, wind, and hybrid systems) and water supply methods (freshwater vs. seawater desalination) in Taiwan. The inventory data were analyzed using SimaPro method.Our results indicate that while solar-driven electrolysis achieves the lowest GWP, it significantly exacerbates regional water stress due to high cooling requirements and panel cleaning, unless coupled with desalination. The study highlights that ignoring the water footprint in hydrogen roadmaps may lead to burden shifting—solving the carbon problem while creating a water crisis. We conclude by proposing site-specific environmental management strategies to optimize the location of hydrogen hubs.