Supplementary Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants

Description

Abstract

To support the hydrogen economy’s goal of reducing environmental pressures through renewable energy integration, environmental shepherding during scale-up is essential. While traditional LCA models upscale small plants, this study addresses the differing engineering of large-scale, gigawatt-range water electrolysis plants in a distinct bottom-up prospective LCA model. It presents a comparative cradle-to-grave prospective LCA of 1 GW alkaline (AWE) and proton exchange membrane (PEMWE) electrolysis plants, projecting technological advancements through 2050 under explorative middle-of-the-road background scenarios. Key performance indicators (KPIs) for both technologies were identified via comprehensive literature review and integrated into electrochemical process models for current (state-of-the-art) and future plants in 2030 and 2050, incorporating optimistic and pessimistic performance scenarios.

Mass and energy balances combined with construction KPIs enabled material demand estimation for all system components. End-of-life was modeled using a cut-off approach. The predictive foreground model was implemented in Brightway2 and linked with four background scenarios generated by premise v.2.2.6. Environmental impacts were assessed using the Environmental Footprint 3.1 method.

Results show significant reductions in global warming potential (GWP) for both AWE and PEMWE by 2050, accompanied by increased abiotic depletion potential of elements (ADPe), with AWE slightly outperforming PEMWE in both. Impacts were highly sensitive to background climate policies: stringent policies improved GWP but increased ADPe. Enhanced plant performance could not offset weak climate policies regarding GWP. Compared to conventional hydrogen, electrolytic hydrogen from renewables exhibits much lower GWP.

Construction impacts mainly derived from electrolyzer stacks, differing fundamentally between technologies, with AWE having higher initial impacts. Future construction impacts decline significantly and are dominated by power electronics. Pursuing strict climate policies and incorporating circularity and recycling are critical for minimizing environmental impacts. On the condition of complying with the planetary save and just operating space, technology choice should prioritize cost and operational flexibility.