Cleaner chlorine production using oxygen depolarized cathodes? A life cycle assessment

Chlorine and caustic soda are two indispensable chemical commodities co-produced in the so-called chlor-alkali electrolysis. Chlor-alkali electrolysis is today a target for cleaner production because of its large electricity demand causing considerable envitonmental impacts. The electricity demand of chloralkali electrolysis can be reduced by 30% using oxygen depolarized cathodes (ODCs) instead of the standard cathodes (STCs) used today. However, ODCs require additional resources and do not produce hydrogen in contrast to existing chlor-alkali plants. This work investigates if the reduction in electricity demand also contributes to cleaner production. For this purpose, environmental impacts from chloralkali electrolysis using ODCs are compared to the impacts from best available existing chlor-alkali plants using STCs. The life cycle assessment includes manufacturing, operation and disposal of the plants. To account for utilization of hydrogen from existing chlor-alkali plants, two alternative utilization scenarios are studied: energy recovery by combustion of hydrogen and use of hydrogen as chemical commodity. Seven environmental impact categories are studied in detail using the ReCiPe method. Chloralkali electrolysis using ODCs yields lower environmental impacts in up to six environmental impact categories. Plant operation contributes most in six out of seven impact categories. Chlor-alkali electrolysis using ODCs has thus potential to contribute to cleaner production in the chlor-alkali industry. (C) 2014 Elsevier Ltd. All rights reserved.