Prioritizing hydrogen deployment across hard-to-electrify sectors based on system-level environmental performance

Hydrogen is widely considered as a key option for decarbonizing hard-to-electrify sectors; however, identifying where and how it should be deployed requires system-level, multi-impact assessment to avoid environmental burden shifting. This study aims to determine environmentally optimal hydrogen deployment pathways and sectoral priorities for Finland’s energy transition using a scenario-based, system-level LCA. The analysis integrates multiple hydrogen production pathways and their conversion into hydrogen-derived fuels and chemicals, which are deployed across steel, shipping, aviation, heavy-duty transport, chemical production, and oil refining sectors under alternative transition scenarios. Environmental performance is evaluated across five midpoint impact categories: climate change, acidification, fine particulate matter formation, marine eutrophication, and ozone depletion, calculated by using the ReCiPe method. Results show that 100 % wind-powered electrolysis-based hydrogen delivers the highest overall environmental performance, reducing national climate change impacts by 80 % (from 30.8 to 6.2 Mt CO 2 ,eq./a) and decreasing other environmental impacts by 47–76 %. Beyond conventional LCA results, this study introduces two novel deployment priority indices (DPIs) to translate multi-impact outcomes into decision-relevant guidance. The system-weighted DPI identifies sectors where hydrogen deployment yields the greatest reduction in national environmental impacts, while the sector-intrinsic DPI ranks transitions based on their internal multi-impact environmental efficiency, independent of sector size. By jointly applying these two DPIs within a unified system-level LCA framework, this study provides a novel, transparent basis for prioritizing hydrogen deployment across sectors, enabling strategic, impact-driven decision-making and efficient allocation of renewable energy resources.