Life cycle assessment of hydrogen from proton exchange membrane water electrolysis in future energy systems

Abstract This study discusses the potential of H 2 production by proton exchange membrane water electrolysis as an effective option to reduce greenhouse gas emissions in the hydrogen sector. To address this topic, a life cycle assessment is conducted to compare proton exchange membrane water electrolysis versus the reference process - steam methane reforming. As a relevant result we show that hydrogen production via proton exchange membrane water electrolysis is a promising technology to reduce CO 2 emissions of the hydrogen sector by up to 75%, if the electrolysis system runs exclusively on electricity generated from renewable energy sources. In a future (2050) base-load operation mode emissions are comparable to the reference system. The results for the global warming potential show a strong reduction of greenhouse gas emissions by 2050. The thoroughly and in-depth modeled components of the electrolyser have negligible influence on impact categories; thus, emissions are mainly determined by the electricity mix. With 2017 electricity mix of Germany, the global warming potential corresponds to 29.5 kg CO 2 eq. for each kg of produced hydrogen. Referring to the electricity mix we received from an energy model emissions can be reduced to 11.5 kg CO 2 eq. in base-load operation by the year 2050. Using only the 3000 h of excess power from renewables in a year will allow for the reduction of the global warming potential to 3.3 kg CO 2 eq. From this result we see that an environmentally friendly electricity mix is crucial for reducing the global warming impact of electrolytic hydrogen.