Water scarcity footprint and water saving potential for large-scale green hydrogen generation: Evidence from coal-to-hydrogen substitution in China.

Green hydrogen generated via water electrolysis using photovoltaics or wind has begun to scale up in the process of achieving the global net-zero goal, but there is a lack of research on its impact on the scarcity of water resources and water saving potential. A water resources impact assessment framework for green hydrogen scale-up development is established, integrating the product water footprint and regional water footprint scarcity impacts and advancing the study of the water resources impacts on green hydrogen from water conservation as well as from a sustainable context. The research framework specifies the cradle-to-gate life cycle water consumption of hydrogen production, establishes the water scarcity footprint based on the available water remaining (AWARE) model, quantifies the water saving intensity and potential of the green hydrogen alternative to traditional hydrogen production, and proposes quantitative indicators of the water saving benefit. Taking the regions of 31 provinces in China as a case study, the wind-to‑hydrogen scenario and the solar-to‑hydrogen scenario will generate approximately 68.86×10 m and 126.10×10 m water scarcity footprints, respectively. Under the coal-to‑hydrogen baseline scenario, approximately 1.68×10 m and - 0.57×10 m of water saving potential will be generated. In addition, the water saving intensity decreases from west to east. According to the adjusted quantitative indicators of water saving benefits, the wind-to‑hydrogen scenario in China can reach 40.22×10 meq and the water saving benefit is more obvious in northern regions such as Hebei, Ningxia and Inner Mongolia. The methodological framework can be applied to other countries or regions to assess the sustainable impacts of green hydrogen production on water resources in a given region.