Life cycle assessment of large-scale underground hydrogen storages: Salt caverns, aquifers and depleted gas reservoirs

Large-scale underground hydrogen storage is essential for enabling high shares of renewable energy by providing long-duration and seasonal storage. This study presents a comparative life cycle assessment of three storage options: salt caverns, saline aquifers, and depleted gas reservoirs. The analysis follows ISO 14040/14044 standards, using SimaPro with the ReCiPe 2016 endpoint method. Twelve scenarios are evaluated, considering grey and green hydrogen alongside different cushion gases. Results are reported per 1 kg of hydrogen over a 40-year lifetime. Salt caverns show the lowest environmental impacts across all categories, outperforming aquifers and depleted reservoirs. Switching from grey to green hydrogen reduces global warming impacts by ∼40% and fossil resource use by up to 50%, though some toxicity impacts increase due to renewable infrastructure. The novelty of this work lies in its integrated comparison of multiple storage types, hydrogen pathways, and cushion gas options within a consistent LCA framework. • Comparative LCA of salt caverns, aquifers, and depleted reservoirs for H 2 storage. • Salt caverns show lowest impacts due to low leakage and high cycling capability. • Green hydrogen cuts climate impacts by ∼40% across all storage options. • Cushion gas choice and hydrogen losses strongly influence UHS environmental performance.