LCA-Based Carbon Footprint Accounting of Mixed Rare Earth Oxides Production from Ionic Rare Earths

Abstract

At present, there are significant knowledge gaps in the research on the resource and environmental effects of rare earth exploitation, especially the carbon emission coefficient. This study applies the life cycle assessment approach to calculate the carbon footprint of producing mixed oxide rare earths using ionic rare earth resources and analyze the sources and influencing factors of the carbon footprint. The results show that the carbon footprint of producing 1 kg of mixed oxide rare earths using ionic rare earths is 17.8~24.3 kg CO2 eq, but its uncertainty is 15.54%; the total carbon footprint from 2012 to 2017 reaches 1.6 × 108~2.19 × 108 kg CO2 eq/year, and after 2018, the carbon footprint decreases to 1.51 × 108~2.07 × 108 kg CO2 eq /year. The total carbon footprint of illegal mining is around 1.50 × 108~1.59 × 108 kg CO2 eq/ year. In principle, the higher the recovery rate, the lower the carbon footprint of 1 kg REO production, but with the increase in the recovery rate, the carbon footprint reduction benefit brought by the increase in the unit recovery rate shows a downward trend. Finally, the new generation of magnesium salt leaching technology, while alleviating ammonia nitrogen pollution in ionic rare earth mines, will increase the carbon footprint of the product.