Sustainability Assessment of the Rare-Earth-Oxide Production Process and Comparison of Environmental Performance Improvements Based on Emergy Analysis

Jing An,He Yang,Ang Tian,Aitian Tao

doi:10.3390/su132313205

Abstract

In recent years, the rapid development of the rare earth industry has had a serious impact on the environment. Some enterprises have taken measures to improve the production process. In order to explore the sustainability of this industry and these improvements’ environmental benefits, this paper combines emergy analysis and lifecycle assessment to evaluate and compare the production process of rare-earth oxides considering the three aspects of emergy flow, pollutant emissions, and emergy-based indicators. Changes in the emergy of pollutant emissions before and after improvement of the production process are discussed. The results show that the greatest inputs in the mining and beneficiation stage and smelting separation stage are labor force and service and non-renewable resources, respectively. These two production stages are highly dependent on external input and have weak competitiveness. Both stages place great pressure on the environment, so the bastnasite production process would be unsustainable in the long term. After the improvement, the environmental impact of the production process for bastnaesite changed significantly, indicating that the improvement effect of the wastewater treatment facilities and the change of fuel from coal to natural gas is remarkable.

Highlights

Bastnaesite is mined in an open pit, and 70% grade rare-earth concentrate is obtained by the magnetic–gravity–flotation process
This study aims to evaluate economic, environmental, and social sustainability based on emergy analysis and life-cycle assessment
We calculated the emergy of the production process of bastnaesite in Sichuan, China, using the method of EM-life-cycle assessment (LCA), and we analyzed the composition and main sources of emergy loss in the production process and evaluated the environmental impacts and sustainability

Summary

Introduction

Rare-earth elements (REEs) are considered to be “monosodium glutamate in industry”. Are classified as strategic resources due to their crucial uses in the production processes of several key industries. China has the largest known rare earth reserves worldwide. The data in [1] showed that China’s rare earth resource reserves totaled 44 million t at the end of 2018, which accounted for 38% of global rare earth reserves. Light rare-earth elements (LREEs) are mainly concentrated in the north of China, and heavy rare-earth elements (HREEs) are mainly concentrated in the south of China. The three major types of rare-earth minerals are mixed bastnaesite–monazite ore in Baotou, ion-absorbed rare earth deposits in the seven southern provinces, and bastnaesite in Sichuan.

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