Life cycle assessment of a renewable-powered floating storage and regasification unit for ammonia and hydrogen fuels: Decarbonizing the maritime sector

Ammonia and hydrogen are increasingly considered promising low-carbon maritime fuels, yet their environmental performance within integrated offshore infrastructure remains insufficiently quantified. The novelty of this research lies in the subsystem-integrated life-cycle assessment of a renewable-powered Floating Storage and Regasification Unit (FSRU) that integrates offshore ammonia and hydrogen storage, regasification, onboard power generation, seawater desalination, and hydrogen production within a unified framework. Unlike previous studies that assess these subsystems separately, the present study evaluates their combined operation on a single offshore platform, capturing subsystem interactions and cross-system energy dependencies. An ISO-compliant cradle-to-gate life cycle assessment was conducted using the ReCiPe 2016 v1.1 Midpoint method to evaluate climate change, freshwater consumption, marine ecotoxicity, marine eutrophication, and stratospheric ozone depletion across three configurations, namely, conventional regasification, renewable-assisted power generation, and an integrated auxiliary subsystem. The results show that ammonia regasification is dominated by operational energy demand, with a climate change impact of 1.27 g CO₂-eq/kg NH₃. In contrast, hydrogen regasification is driven mainly by material production, with an impact of 5.68 g CO₂-eq/kg H₂. For renewable power generation, high seawater pumping requirements increase the climate change impact to 101.9 g CO₂-eq/kWh for the ocean-based subsystem, while thermal energy storage contributes 16.6 g CO₂-eq/kWh in the solar-based subsystem. Hydrogen production via electrolysis remains highly electricity-intensive, resulting in climate change impacts of 17.5–26.9 kg CO₂-eq/kg H₂ under grid-supported operation. Sensitivity analysis further indicates that onboard renewable operation reduces climate change impacts by 20.7% for the solar-based subsystem and 76.3% for the ocean-based subsystem. The main contribution of this work is the establishment of an integrated environmental benchmark for renewable-powered FSRUs, highlighting subsystem-level trade-offs and design pathways to reduce life-cycle impacts in offshore ammonia and hydrogen supply chains.