MSc in Environmental Systems Engineering Aländji BOUORAKIMA Supervisor: Julia STEGEMANN Rare earth oxide production: Assessment of the environmental impacts in two Chinese mines UCL Department of Civil, Environmental and Geomatic Engineering, Gower St, London ,WC1E 6BT What are rare earths? Rare earth elements are a group of 17 metals which, contrary to their name, are not all very rare Life Cycle Assessment methodology Modelling of Modelling of the the processes processes (beneficiation, (beneficiation, hydrometallurgy and and refining) refining) hydrometallurgy Inventory of Inventory of every every input input and and output output (energy, (energy, chemicals, wastes) wastes) chemicals, Assessment of Assessment of the the environmental environmentalimpacts impactsaccording based on to six different categories: six different categories: Relative abundance of rare earths elements in Earth’s crust (Haxel 2002) • Global warming • Radioactive waste generation • Acidification • Land use • Eutrophication • Toxicity in wastewater Why are rare earths important? They are used in several technological applications and particularly environmental friendly applications such as:Electric motors for hybrid Ni-MH batteries and electric vehicles Generators in wind turbine Computer hard disks Automotive catalysts (reduction of NOx and CO) Hydrogen storage devices Energy saving light bulbs LEDs and OLEDs Solid Oxide Fuel Cells Rare earth oxide production In 2010, 97% of the world production came from China Midpoint indicators Category Unit Bayan Obo Maoniuping CO2 emissions kg of CO2 6,450 5,940 Atmosphere acidification kg of SO2eq 124 779 Wastewater acidification kg of SO2eq 559 444 Wastewater eutrophication kg of H3PO4eq 428 n/a Radioactivity discharge Bq 5.3 10 7 3.7 10 7 Volume used m 95.4 n/a Oxalic acid C2H2O4 35 kg 35 kg Ammonium bicarbonate NH4HCO3 61 kg - Ammonium sulphates (NH4)2SO4 861 kg - - 327 kg Toxicity discharge in wastewater In China, only Bayan Obo and Maoniuping deposits produce light rare earth elements (La, Ce, Nd, Pr, Sm) They account for 70% of the world rare earth oxide production Question: What are the environmental impacts of producing rare earth oxides in Bayan Obo and Maoniuping? 3 Sodium sulphates Na2SO4 Conclusion The midpoint indicators show that considerable environmental impacts are related to the rare earth oxide production Rare earth production requires a strict waste management to avoid radioactive or toxic run-offs The processes of rare earth oxide production are very energy-intensive Reference: Haxel, G. B., Hedrick, J.B., Orris, G.J. (2002). "Rare earth elements: Critical resources for high technology", U.S. Geological Survey, available at: http://www.rareelementresources.com/i/pdf/fs087-02.pdf Last access: 31/08/2011.
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