Comparative Life Cycle Assessment of Neodymium Oxide Electrolysis in Molten Salt

Abstract

Rare earth elements are used in renewable energy generation techniques like wind turbines as well as in various high-tech applications in the automobile industry, electrical engineering, optics, and catalyzers. Due to the environmentally harmful production of rare earths, they have been subject of life cycle assessment investigations in the past years. Most of these studies focus on rare earth oxide production. The subsequent reduction of rare earth oxides to the final metal in a molten salt electrolysis has significant environmental impacts especially on human toxicity. The main drivers are rare earth fluoride production and molten salt electrolysis. In this study, exemplarily a comparative life cycle assessment of neodymium oxide electrolysis in molten salt as well as various neodymium fluoride production processes is conducted. The different assumptions regarding inputs and outputs of the electrolysis process are discussed. Then, the impacts of the electrolysis processes modeled in different ways are analyzed in relation to the entire process chain to produce neodymium. The results show a share of the electrolysis process on the entire process chain varying from 9% to 82% depending on different assumptions. Based on this analysis, improvements for the electrolysis process are proposed.