Prospective sustainability assessment of water electrolyzer green hydrogen process systems: a monetization-based approach

Hydrogen (H2) is considered a key future energy carrier in supporting a carbon-neutral society. Among various H2 production methods, water electrolyzers are recognized as a potentially low-carbon H2 production pathway when powered by renewable energy sources. This study evaluates the prospective environmental and economic sustainability of water electrolysis-based hydrogen process systems, considering technological advancements and electricity decarbonization. Four electrolyzer technologies, namely alkaline electrolyzers (AEL), proton exchange membrane electrolyzers (PEM), solid oxide electrolyzers (SOE), and anion exchange membrane electrolyzers (AEM), are assessed under varying energy sources: wind, solar, and grid electricity. For the prospective life cycle assessment (LCA), the REMIND integrated assessment model is employed, while techno-economic analysis (TEA) is conducted using the learning curve approach based on energy scenarios from the International Energy Agency (IEA). The relative performance of hydrogen process systems across different energy sources was assessed by calculating the total cost of hydrogen, defined as the sum of future levelized costs and environmental external costs. Results of total cost of hydrogen indicate that at present, all hydrogen process systems operated with grid electricity perform worse in environmental and economic terms (23.06–27.46 USD per kg H2) than grey (7.26 USD per kg H2) and blue H2 (2.98 USD per kg H2). In contrast, systems operated with renewable wind energy (3.10–6.79 USD per kg H2) outperform grey H2. In 2050, AEM operated with wind energy exhibits both low environmental impacts (climate change: 0.3 kg CO2 eq., human health: 2.22E-01 DALYs, ecosystem quality: 2.63E-09 species-years, and resource availability: 0.05 USD per kg H2) and low levelized costs (1.38 USD per kg H2).