Overlooked source of hydrogen: The environmental potential of chlor-alkali by-product

Hydrogen created as a by-product of chlor-alkali electrolysis is the second largest contributor to total hydrogen production in Europe. Nevertheless, it is commonly overlooked in hydrogen production pathway classifications. This study applies life-cycle assessment to shed light on the environmental impacts of chlor-alkali hydrogen based on diverse production and methodological aspects, and compares the most appropriate utilization scenarios in terms of GHG savings. The results demonstrate a broad range of carbon footprint from 0.01 to 7.14 kg CO2 eq./kg with a high dependance on consumed energy sources and adopted allocation method. When analyzing the scenarios of utilization, the most favorable scenario in terms of potential savings is the substitution of high-emission grey hydrogen. According to our results, chlor-alkali hydrogen could be considered renewable or low-emission following the standards set by the EU, and thus can facilitate the transition to carbon neutrality.