Life cycle assessment of a polymer electrolyte membrane water electrolysis

In this study, the environmental burdens of polymer electrolyte membrane water electrolysis (PEMWE) producing hydrogen are analyzed with the help of a life cycle assessment (LCA). Three scenarios, which differ in the techniques applied for generating electricity for hydrogen production and the operation mode, are considered. Using electricity generated with the currently available generation structure leads to the GWP100 of 32.52 kg CO₂-eq per kilogram H₂, which leaves the plant with a purity of 99.9% at 35 bar and 333–335 K. These emissions are to a large extent caused throughout the plant’s operation but not during its production phase. Thus, currently a large proportion of the GWP100 results from electricity production. As electricity generation based on renewable energy continues to develop, the greenhouse gas emissions per kilowatt-hour electricity decrease. Consequently, the overall greenhouse gas emissions as well as those caused within the operation phase of PEMWE decline and the relative impact of the production phase grows. In case of operating the electrolysis plant exclusively with electricity originating from wind, the GWP100 of 0.93 kg CO₂-eq/kg H₂ results, of which more than one quarter is assigned to the production of the plant. Thus, the production phase of a PEMWE plant must be thoroughly considered when the share of renewable energy in electricity generation increases. Apart from the GWP100, other impact categories are analyzed. Comparing the three scenarios reveals that the application of renewable energy for electricity generation is beneficial for most impact categories. Nevertheless, ADP elements, FATEP inf., HTP inf. and ODP are negatively affected.