Supporting Information. Behind the scenes of clean energy the. environmental footprint of rare earth products

Transcription

1 Supporting Information Behind the scenes of clean energy the environmental footprint of rare earth products Praneet S. Arshi 1,2, Ehsan Vahidi 2, 3 and Fu Zhao 1,2,3, * 1 School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907, United States 2 Ecological Sciences and Engineering Interdisciplinary Graduate Program, Purdue University, Young Hall, Room B-40, 155 South Grant Street, West Lafayette, IN 47907, United States 3 Environmental & Ecological Engineering, Purdue University, 500 Central Dr, West Lafayette, IN 47907, United States Number of pages: 33 Number of figures: 12 Number of tables: 17 Appendix: CMLCAT 1.0 User Manual S1

2 Literature Review Summary Table S - 1. Literature Review Summary Ecoinvent Database 1 GaBi database 2 Zaimes et al. 3 (2015) Vahidi et al. 4 (2016) Lee and Wen 5 (2016) Sprecher et al. 6 (2014) (v2.0 and subsequent v3.0) Rare Earth Source Bayan Obo Bayan Obo & Sichuan Bayan Obo South China clays Bayan Obo, South China, Sichuan Bayan Obo Processes Covered Oxide production Metal production Oxide production Mixed oxide production Metal production RE magnet production Rare Earths Considered 70% RE concentrate, 94% rare-earth oxide, 60% cerium oxide, neodymium oxide, lanthanum oxide, praseodymium oxide, samarium europium gadolinium concentrate 20 datasets including cerium and oxides, samarium and oxides, europium and oxides, gadolinium, terbium, holmium, erbium, thulium, ytterbium, lutetium, and yttrium Light, medium, and heavy rare earth oxides 92% mixed REO 15 pure rare earth metals Seven separated REOs, neodymium metal production, NdFeB magnets, RE recycling S2

3 Limitations REO composition is different from actual Bayan Obo composition; emission numbers from Mountain Pass reports; process data not updated since 2004 Process data based on a 2009 Chinese Rare Earth Industry Report; LCI data is highly aggregated reducing transparency, documentation of the processinventory data is confusing in terms of the processes and source deposits considered, for example, documentation says monazite is predominant in China which is not true; Mountain Pass is brought into the picture for several processes which complicates things further Emission numbers come from environmental standards which are not necessarily followed in China; the quantity of REEs lost during the mining process was neglected; the comparison with other metals is not valid as the final product in this study is rare earth oxide and not rare earth metal. Downstream processes of solvent extraction is not included in the study limiting the comparison with other sources in terms of pure rare earth oxides Inventory data Excel file has discrepancies in terms of energy consumption; a range was provided with low/high scenarios, in certain situations when a low value for one material input is taken, it causes an increased consumption for another material/energy input Use of surrogates in the production process, for example, chemical organics instead of P204/P507 in the SX process. S3

4 How the current study moves beyond the limitations of Sprecher et al. (2014) study: For magnets, two production pathways are considered based on two Chinese facility reports to evaluate the environmental impacts of producing NdFeB magnets of varying coercivity. In Sprecher s study, different facility reports for NdFeB magnets are not considered. The input rare earths in this study come from two different sources (Bayan Obo mines as well as ion-adsorption clays) while in Sprecher s study all rare earth elements are from Bayan Obo mines. In terms of limitations, the life cycle inventory for solvent extraction step used to separate rare earth elements is largely based on Ecoinvent process neodymium oxide, at plant in Sprecher s study. Unfortunately, in this Ecoinvent process, surrogates like chemicals organic, at plan [GLO] are used. Also, the organic solvent and energy consumption is based on rough estimation. The data on solvent extraction (Vahidi et al. 2017) used in this investigation better represents the current practice in China. For Neodymium metal production, Sprecher s study develops inventory by modifying the Hall-Héroult process for aluminum production in the Ecoinvent processes i.e. aluminium, primary, at plant. In the current research, actual production data is used. For NdFeB alloying and strip casting, which is an energy intensive process, Sprecher s study estimate electricity consumption based on lab scale experiments. In this study, actual production data is used. Allocation In a multi-output process, the environmental impact can be assigned to each output in several ways. Mass based allocation or economic value based allocation are the two common methods. The chosen allocation factors help assign the share of environmental burden to different outputs. S4

5 Extraction of REE produces several commercially usable byproducts at various stages of the production process. Allocation factors for such processes are based on the economic value and mass of the output. Solvent extraction process is the best example where allocation factors are essential to allocate the share of environmental burden. Assuming the price of individual rare earth oxide REOi with concentration Ci as Pi, the cost ratio Xi is: XX ii = PP ii CC ii (PP ii CC ii ) (1) The cost ratio Xi is for the REOi with mass output Mi. As we are looking at a unit processes (per kg output basis), the environmental impact associated with 1 kg of REOi can be calculated using the allocation factor A.Fi, where A.Fi is: AA. FF ii = XX ii MM ii (2) Hence, the environmental impact in a multi-output process can be mathematically calculated in the Excel file. IIIIIIIIIIII ii = AA. FF ii IIIIIIIIIIII pppppppppppppp (3) The allocation factors are included in the interlinked Excel tool in the AllocationFactors file located in C:\RE_LCA\0.Allocation_CFs. S5

6 Within the model, the allocation factors can be altered based on change in price, concentration or output. Table S - 2 shows the REO prices 7 considered in the Excel-based model. Table S - 2. Rare earth oxide prices in Rare Earth Oxide Price ($/kg) Cerium Oxide 4.4 Dysprosium oxide 340 Erbium oxide 77 Europium oxide 680 Gadolinium Oxide 39 Holmium oxide 60 Lanthanum Oxide 4.8 Lutetium oxide 1250 Neodymium oxide 59 Praseodymium Oxide 105 Samarium oxide 23 Samarium-Europium- Gadolinium oxide 39 Terbium oxide 600 Thulium oxide 7500 Ytterbium oxide 69 Yttrium oxide 50 Life Cycle Impact Assessment For TRACI 2.1, the impact categories are: Acidification (kg SO2-Equiv.), Ecotoxicity (CTUe), Eutrophication (kg N-Equiv.), Global Warming Air, excl. biogenic carbon (kg CO2-Equiv.), Global Warming Air, incl. biogenic carbon (kg CO2-Equiv.), Human Health Particulate Air (kg PM2,5-Equiv.), Human toxicity, cancer (CTUh), Human toxicity, non-canc. (CTUh), Ozone S6

7 Depletion Air (kg CFC 11-Equiv.), Resources, Fossil fuels (MJ surplus energy), Smog Air (kg O3- Equiv.). 8,9 The midpoint ILCD (v 1.06) impact categories are: Acidification (Mole of H+ eq.), Climate change, excl biogenic carbon (kg CO2-Equiv.), Climate change, incl biogenic carbon (kg CO2-Equiv.), Ecotoxicity freshwater (CTUe), Eutrophication freshwater (kg P eq), Eutrophication marine (kg N-Equiv.), Eutrophication terrestrial (Mole of N eq.), Human toxicity, cancer effects (CTUh), Human toxicity, non-cancer effects (CTUh), Ionizing radiation, human health (kbq U235 eq), Ozone depletion midpoint (kg CFC-11 eq), Particulate matter/respiratory inorganics (kg PM2,5-Equiv.), Photochemical ozone formation, human health (kg NMVOC), Resource depletion water (m³ eq.), Resource depletion, mineral, fossils and renewables (kg Sb-Equiv.). 9,10 Data Documentation and Format EcoSpold1, an Ecoinvent data format is used to document the process, its products and relevant life cycle inventory. 11 It lists all the data fields for documentation of the unit process such as LCI and meta information. Furthermore, it follows the international technical specification ISO/TS The Excel version of the data format is used to document the process. EcoSpold1 access macro 11 can be used to convert XLS file format to XML and vice versa. To convert the XLS file format to XML, the workbook had the following sheets: X-Exchange, X-Process, X-Source and X-Person. 11 The XML file format helps with the flexibility and data sharing of the Excel based package by allowing various institutions to exchange the data and import it into an LCA software in an organized manner. For the software package to be harmonious, all the files are named as per a common convention. Three data fields define a process: name, unit, location. However, the following order was used to create the file name: 1. The code of country location is used first such as CN for China, GLO for global, etc. S7

8 2. Name of the process/material/service 3. Any additional description of some importance such as location of mine or deposits is added at the end. For example, the Chinese calcination process used for Bayan Obo deposits is: CN_Calcination_BayanObo S8

9 Package Use The package is available as a.zip file and should be extracted directly to the C drive. This is required to maintain the absolute links between the Excel files. Once extracted, the file path should look like C:\RE_LCA... The package is subsequently arranged into interconnected folders: 0. Allocation and characterization factors (C:\RE_LCA\0.Allocation_CFs) 1. Materials and energy base processes (C:\RE_LCA\1.Materials_Energy) 2. Mining and processing (C:\RE_LCA\2.Mining_Processing) 3. Metals and alloys (C:\RE_LCA\3.Metals_Alloys) 4. Products (C:\RE_LCA\4.Products) 5. Recycling (C:\RE_LCA\5.Recycling) (Note no recycling of REE exist now. Two processes are included under Recycling but those only serve as template for future updates). Within each Excel file, the environmental impact of the process is calculated and displayed below the LCI on the X-Exchange sheet. The Excel file can be converted into XML file format or vice-versa using the ecospold Excel macro. The user also has the option of choosing mass based allocation, however, when a mass based allocation is used, all the REO will have the same impact as they are normalized on per kg basis. More detail on the structure and linkage of the Excel based package is available in the Manual word file, available in C:\RE_LCA. As the Excel files are linked in absolute terms, the file location needs to stay in the C drive. Such absolute links (a problem of using simple Excel files) does not allow the environmental impact calculation mechanism to work on other systems like Mac or Linux. However, one can still use the life cycle inventory as a valuable source of process information. A detailed manual document is also available within the.zip file. S9

10 The software tool Critical Materials Life Cycle Assessment Tool (CMLCAT) can be obtained free of charge by contacting Dr. Fu Zhao: The software tool will be updated annually. The current version is 1.0. S10

11 Life Cycle Analysis Results The two facilities that segregate and purify mixed REO to pure individual REOs have annual REO production as shown in Figure S - 1 and Figure S - 2. Figure S - 1 shows the various metal oxides produced by a separation facility using ion-adsorption clays. 13 Quantity (tons/year) Lanthanum Oxide Cerium Oxide Praseodymium Oxide Neodymium oxide Samarium oxide Europium oxide Gadolinium Oxide Terbium oxide Dysprosium oxide Holmium oxide Erbium oxide Thulium oxide Ytterbium oxide Lutetium oxide Yttrium oxide Figure S - 1. Annual REO output from facility in Fujian S11

12 Figure S - 2 on the other hand shows the REOs obtained from a separation facility using the Bayan Obo sourced rare earth minerals. 14 Quantity (REO equivalent tons/year) Lanthanum Carbonate Cerium Carbonate Praseodymium Carbonate Neodymium Carbonate 4000 Samarium-Europium- Gadolinium Carbonate Figure S - 2. Annual REO equivalent output from facility in Baotou S12

13 Rare Earth Oxide Bayan Obo mines Table S - 3. Life cycle impacts for REOs from Bayan Obo mines using TRACI v2.1 TRACI Cerium Oxide Samarium- Europium- Gadolinium Oxide Lanthanum Oxide Neodymium oxide Praseodymium Oxide Acidification [kg SO2-Equiv.] 5.52E E E E E+00 Ecotoxicity [CTUe] 1.64E E E E E+02 Eutrophication [kg N-Equiv.] 1.08E E E E E-01 Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] 6.67E E E E E+02 Global Warming Air, incl. biogenic carbon [kg CO2-Equiv.] 6.66E E E E E+02 Human Health Particulate Air [kg PM2,5-Equiv.] 3.51E E E E E-01 Human toxicity, cancer [CTUh] 3.29E E E E E-06 Human toxicity, non-canc. [CTUh] 1.17E E E E E-05 Ozone Depletion Air [kg CFC 11-Equiv.] 1.31E E E E E-05 Resources, Fossil fuels [MJ surplus energy] 1.10E E E E E+02 Smog Air [kg O3-Equiv.] 9.89E E E E E+01 S13

14 Table S - 4. Life cycle impacts for REOs from Bayan Obo mines using ILCD v1.06 ILCD Cerium Oxide Samarium- Europium- Gadolinium Oxide Lanthanum Oxide Neodymium Oxide Praseodymium Oxide Acidification [Mole of H+ eq.] 6.41E E E E E+00 Climate change, excl biogenic carbon [kg CO2-Equiv.] 6.67E E E E E+02 Climate change, incl biogenic carbon [kg CO2-Equiv.] 6.66E E E E E+02 Ecotoxicity freshwater [CTUe] 2.07E E E E E+02 Eutrophication freshwater [kg P eq] 9.25E E E E E-02 Eutrophication marine [kg N-Equiv.] 7.37E E E E E-02 Eutrophication terrestrial [Mole of N eq.] 1.72E E E E E+00 Human toxicity, cancer effects [CTUh] 3.44E E E E E-06 Human toxicity, non-cancer effects [CTUh] 1.09E E E E E-05 Ionizing radiation, human health [kbq U235 eq] 4.90E E E E E+01 Ozone depletion [kg CFC-11 eq] 1.11E E E E E-05 Particulate matter/respiratory inorganics [kg PM2,5-Equiv.] 1.33E E E E E-01 Photochemical ozone formation, human health [kg NMVOC] 4.55E E E E E+00 Resource depletion water [m³ eq.] 5.54E E E E E+00 Resource depletion, mineral, fossils and renewables [kg Sb-Equiv.] 4.58E E E E E-02 S14

15 Rare Earth Oxide Ion Adsorption Clays Table S - 5. Life cycle impacts for REOs from ion-adsorption clays using TRACI v2.1 TRACI CeO DyO ErO EuO GdO HoO LaO LuO NdO PrO SmO TrO TmO YbO YO Acidification [kg SO2-4.82E E E E E E E E E E E E E E E+00 Equiv.] Ecotoxicity [CTUe] 2.27E E E E E E E E E E E E E E E+02 Eutrophication [kg N- Equiv.] Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] Global Warming Air, incl. biogenic carbon [kg CO2-Equiv.] Human Health Particulate Air [kg PM2,5-Equiv.] Human toxicity, cancer [CTUh] Human toxicity, noncanc. [CTUh] Ozone Depletion Air [kg CFC 11-Equiv.] Resources, Fossil fuels [MJ surplus energy] 1.99E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E+01 Smog Air [kg O3- Equiv.] 3.04E E E E E E E E E E E E E E E+00 S15

16 Table S - 6. Life cycle impacts for REOs from ion-adsorption clays using ILCD v1.06 ILCD CeO DyO ErO EuO GdO HoO LaO LuO NdO PrO SmO TrO TmO YbO YO Acidification [Mole of H+ eq.] Climate change, excl biogenic carbon [kg CO2- Equiv.] Climate change, incl biogenic carbon [kg CO2- Equiv.] Ecotoxicity freshwater [CTUe] Eutrophication freshwater [kg P eq] Eutrophication marine [kg N-Equiv.] Eutrophication terrestrial [Mole of N eq.] Human toxicity, cancer effects [CTUh] Human toxicity, non-cancer effects [CTUh] Ionizing radiation, human health [kbq U235 eq] Ozone depletion [kg CFC- 11 eq] Particulate matter/respiratory inorganics [kg PM2,5- Equiv.] Photochemical ozone formation, human health [kg NMVOC] Resource depletion water [m³ eq.] Resource depletion, mineral, fossils and renewables [kg Sb-Equiv.] 4.02E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E-03 S16

17 Rare Earth Metals and Alloys The metal production process of molten salt electrolysis used at Jiangxi Taihe Changwei New Materials Limited produces praseodymium, dysprosium-iron alloy, gadolinium-iron alloy, neodymium-praseodymium alloy along with certain rare earth fluorides like gadolinium fluoride, neodymium-praseodymium fluoride and hydrogen fluoride annualy. 15 Assuming neodymium, cerium and dysprosium to be produced in the same way, Table S - 7 and show the TRACI v2.1 and ILCD v1.06 environmental impacts from two possible sources to produce these pure metals. Table S - 7. Life cycle impacts for rare earth metals using TRACI v2.1 TRACI Bayan Obo deposit Cerium Neodymium Praseodymium Dysprosium South China Clay Bayan Obo deposit South China Clay Bayan Obo deposit South China Clay South China Clay Acidification [kg SO2-Equiv.] 1.64E E E E E E E+01 Ecotoxicity [CTUe] 6.34E E E E E E E+03 Eutrophication [kg N-Equiv.] 3.37E E E E E E E+01 Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] 1.86E E E E E E E+02 Global Warming Air, incl. biogenic carbon [kg CO2-Equiv.] 1.85E E E E E E E+02 Human Health Particulate Air [kg PM2,5-Equiv.] 5.90E E E E E E E-01 Human toxicity, cancer [CTUh] 6.47E E E E E E E-05 Human toxicity, non-canc. [CTUh] 4.18E E E E E E E-04 Ozone Depletion Air [kg CFC 11-Equiv.] 1.73E E E E E E E-05 Resources, Fossil fuels [MJ surplus energy] 1.54E E E E E E E+02 Smog Air [kg O3-Equiv.] 2.03E E E E E E E+01 S17

18 Table S - 8. Life cycle impacts for rare earth metals using ILCD v1.06 ILCD Bayan Obo deposit Cerium Neodymium Praseodymium Dysprosium South China Clay Bayan Obo deposit South China Clay Bayan Obo deposit South China Clay South China Clay Acidification [Mole of H+ eq.] 1.95E E E E E E E+00 Climate change, excl biogenic carbon [kg CO2- Equiv.] 1.86E E E E E E E+02 Climate change, incl biogenic carbon [kg CO2- Equiv.] 1.85E E E E E E E+02 Ecotoxicity freshwater [CTUe] 7.64E E E E E E E+03 Eutrophication freshwater [kg P eq] 3.63E E E E E E E-01 Eutrophication marine [kg N-Equiv.] 1.58E E E E E E E+01 Eutrophication terrestrial [Mole of N eq.] 3.49E E E E E E E+00 Human toxicity, cancer effects [CTUh] 6.70E E E E E E E-05 Human toxicity, non-cancer effects [CTUh] 4.07E E E E E E E-04 Ionizing radiation, human health [kbq U235 eq] 9.06E E E E E E E+01 Ozone depletion [kg CFC-11 eq] 1.48E E E E E E E-05 Particulate matter/respiratory inorganics [kg PM2,5-Equiv.] 2.66E E E E E E E-01 Photochemical ozone formation, human health [kg NMVOC] 1.10E E E E E E E+00 Resource depletion water [m³ eq.] 1.43E E E E E E E+00 Resource depletion, mineral, fossils and renewables [kg Sb-Equiv.] 9.24E E E E E E E-02 S18

19 Table S - 9. Life cycle impacts for rare earth alloys using TRACI v2.1 Gadolinium-Iron Alloy Neodymium-Praseodymium Alloy Dysprosium-Iron Alloy TRACI Bayan Obo deposit South China Clay Bayan Obo deposit South China Clay South China Clay Acidification [kg SO2-Equiv.] 5.32E E E E E+01 Ecotoxicity [CTUe] 1.44E E E E E+03 Eutrophication [kg N-Equiv.] 9.99E E E E E+01 Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] 6.34E E E E E+02 Global Warming Air, incl. biogenic carbon [kg CO2-Equiv.] 6.33E E E E E+02 Human Health Particulate Air [kg PM2,5-Equiv.] 2.96E E E E E-01 Human toxicity, cancer [CTUh] 2.93E E E E E-05 Human toxicity, non-canc. [CTUh] 1.04E E E E E-04 Ozone Depletion Air [kg CFC 11-Equiv.] 1.05E E E E E-05 Resources, Fossil fuels [MJ surplus energy] 8.92E E E E E+02 Smog Air [kg O3-Equiv.] 8.63E E E E E+01 S19

20 Table S Life cycle impacts for rare earth alloys using ILCD v1.06 Gadolinium-Iron Alloy Neodymium-Praseodymium Alloy Dysprosium-Iron Alloy ILCD Bayan Obo deposit South China Clay Bayan Obo deposit South China Clay South China Clay Acidification [Mole of H+ eq.] 6.23E E E E E+00 Climate change, excl biogenic carbon [kg CO2-Equiv.] 6.34E E E E E+02 Climate change, incl biogenic carbon [kg CO2-Equiv.] 6.33E E E E E+02 Ecotoxicity freshwater [CTUe] 1.83E E E E E+03 Eutrophication freshwater [kg P eq] 9.02E E E E E-01 Eutrophication marine [kg N-Equiv.] 6.48E E E E E+01 Eutrophication terrestrial [Mole of N eq.] 1.50E E E E E+00 Human toxicity, cancer effects [CTUh] 3.05E E E E E-05 Human toxicity, non-cancer effects [CTUh] 9.77E E E E E-04 Ionizing radiation, human health [kbq U235 eq] 4.20E E E E E+01 Ozone depletion [kg CFC-11 eq] 8.96E E E E E-05 Particulate matter/respiratory inorganics [kg PM2,5- Equiv.] 1.16E E E E E-01 Photochemical ozone formation, human health [kg NMVOC] 4.02E E E E E+00 Resource depletion water [m³ eq.] 5.16E E E E E+00 Resource depletion, mineral, fossils and renewables [kg Sb-Equiv.] 3.96E E E E E-02 S20

21 Table S Environmental impacts comparison of neodymium with Lee and Wen (2016) Current Study Lee and Wen (2016) 5 Bayan Obo deposit South China Clay Bayan Obo Southern Provinces Sichuan Average Average Lower Average Upper Lower Average Upper Lower Average Upper Acidification [kg SO2-Equiv.] Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] Ozone Depletion Air [kg CFC 11-Equiv.] 1.00E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E-07 S21

22 Table S Environmental impacts comparison of cerium with Lee and Wen (2016) Current Study Lee and Wen (2016) 5 Bayan Obo deposit South China Clay Bayan Obo Southern Provinces Sichuan Average Average Lower Average Upper Lower Average Upper Lower Average Upper Acidification [kg SO2-Equiv.] Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] Ozone Depletion Air [kg CFC 11-Equiv.] 1.64E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E-07 S22

23 Rare Earth Magnets Table S Life cycle impacts for 1 kg NdFeB magnets using TRACI v2.1 TRACI Guangdong TDK-Guangsheng Rare Earth New Materials Co. Limited Dongguan Longyue Limited Inc. Bayan Obo deposit South China Clay Bayan Obo deposit South China Clay Acidification [kg SO2-Equiv.] 2.41E E E E+00 Ecotoxicity [CTUe] 2.53E E E E+02 Eutrophication [kg N-Equiv.] 8.61E E E E+00 Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] 8.92E E E E+01 Global Warming Air, incl. biogenic carbon [kg CO2-Equiv.] 8.75E E E E+01 Human Health Particulate Air [kg PM2,5-Equiv.] 3.10E E E E-02 Human toxicity, cancer [CTUh] 3.94E E E E-06 Human toxicity, non-canc. [CTUh] 1.76E E E E-05 Ozone Depletion Air [kg CFC 11-Equiv.] 1.26E E E E-06 Resources, Fossil fuels [MJ surplus energy] 1.04E E E E+01 Smog Air [kg O3-Equiv.] 1.01E E E E+00 S23

24 Table S Life cycle impacts for 1 kg NdFeB magnets using ILCD v1.06 ILCD Guangdong TDK-Guangsheng Rare Earth New Materials Co. Limited Dongguan Longyue Limited Inc. South South China Bayan Obo deposit Bayan Obo deposit China Clay Clay Acidification [Mole of H+ eq.] 8.64E E E E-01 Climate change, excl biogenic carbon [kg CO2-Equiv.] 8.92E E E E+01 Climate change, incl biogenic carbon [kg CO2-Equiv.] 8.75E E E E+01 Ecotoxicity freshwater [CTUe] 3.20E E E E+02 Eutrophication freshwater [kg P eq] 1.63E E E E-03 Eutrophication marine [kg N-Equiv.] 7.12E E E E+00 Eutrophication terrestrial [Mole of N eq.] 1.75E E E E-01 Human toxicity, cancer effects [CTUh] 4.12E E E E-06 Human toxicity, non-cancer effects [CTUh] 1.69E E E E-06 Ionizing radiation, human health [kbq U235 eq] 5.66E E E E+00 Ozone depletion [kg CFC-11 eq] 1.09E E E E-06 Particulate matter/respiratory inorganics [kg PM2,5-Equiv.] 1.34E E E E-02 Photochemical ozone formation, human health [kg NMVOC] 4.83E E E E-01 Resource depletion water [m³ eq.] 9.05E E E E-01 Resource depletion, mineral, fossils and renewables [kg Sb- Equiv.] 6.17E E E E-03 S24

25 NdFeB Magnet Production (TDK) - Ion Adsorption Clays Smog Air [kg O3-Equiv.] Resources, Fossil fuels [MJ surplus energy] Ozone Depletion Air [kg CFC 11-Equiv.] Human toxicity, non-canc. [CTUh] Human toxicity, cancer [CTUh] Human Health Particulate Air [kg PM2,5-Equiv.] Global Warming Air, incl. biogenic carbon [kg CO2-Equiv.] Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] Eutrophication [kg N-Equiv.] Ecotoxicity [CTUe] Acidification [kg SO2-Equiv.] 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Mixed REO Production Solvent Extraction Electrorefining Magnet Production Figure S - 3. Percentage contribution of process stages for NdFeB magnet production using REOs sourced from ion-adsorption clays S25

26 NdFeB Magnet Production (TDK) - Mixed REO sources Smog Air [kg O3-Equiv.] Resources, Fossil fuels [MJ surplus energy] Ozone Depletion Air [kg CFC 11-Equiv.] Human toxicity, non-canc. [CTUh] Human toxicity, cancer [CTUh] Human Health Particulate Air [kg PM2,5-Equiv.] Global Warming Air, incl. biogenic carbon [kg CO2-Equiv.] Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] Eutrophication [kg N-Equiv.] Ecotoxicity [CTUe] Acidification [kg SO2-Equiv.] 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Mixed REO Production Solvent Extraction Electrorefining Magnet Production Figure S - 4. Percentage contribution of process stages for NdFeB magnet production using REOs sourced from ion-adsorption clays and Bayan Obo mines S26

27 Table S Environmental impacts comparison of NdFeB magnets with Sprecher et al. (2014) NdFeB Magnets Guangdong TDK- Guangsheng Rare Earth New Materials Co. Limited Dongguan Longyue Limited Inc. Sprecher et al. (2014) 6 Acidification [kg SO2- Equiv.] Eutrophication [kg N- Equiv.] Global Warming [kg CO2-Equiv.] Ozone Depletion [kg CFC 11-Equiv.] 2.41E E E-01 to 6.60E E E E-01 to 3.00E E E E+01 to 4.10E E E E-06 to 3.9E-06 S27

28 Rare Earth Phosphors Table S Life cycle impacts for 1 kg phosphors using TRACI v2.1 TRACI Blue phosphor Green Phosphor, CeO from south China clays Green Phosphor, CeO from Bayan Obo Red Phosphor Mixed Phosphor Acidification [kg SO2-Equiv.] 2.37E E E E E+01 Ecotoxicity [CTUe] 1.59E E E E E+03 Eutrophication [kg N-Equiv.] 9.46E E E E E+01 Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] 3.71E E E E E+02 Global Warming Air, incl. biogenic carbon [kg CO2-Equiv.] 3.53E E E E E+02 Human Health Particulate Air [kg PM2,5-Equiv.] 4.43E E E E E-01 Human toxicity, cancer [CTUh] 3.25E E E E E-05 Human toxicity, non-canc. [CTUh] 1.03E E E E E-05 Ozone Depletion Air [kg CFC 11-Equiv.] 3.84E E E E E-05 Resources, Fossil fuels [MJ surplus energy] 2.96E E E E E+02 Smog Air [kg O3-Equiv.] 2.56E E E E E+01 S28

29 Table S Life cycle impacts for 1 kg phosphors using ILCD v1.06 ILCD Blue phosphor Green Phosphor, CeO from south China clays Green Phosphor, CeO from Bayan Obo Red Phosphor Mixed Phosphor Acidification [Mole of H+ eq.] 3.52E E E E E+00 Climate change, excl biogenic carbon [kg CO2-Equiv.] 3.71E E E E E+02 Climate change, incl biogenic carbon [kg CO2- Equiv.] 3.53E E E E E+02 Ecotoxicity freshwater [CTUe] 2.41E E E E E+03 Eutrophication freshwater [kg P eq] 9.34E E E E E-02 Eutrophication marine [kg N-Equiv.] 8.72E E E E E+01 Eutrophication terrestrial [Mole of N eq.] 4.39E E E E E+00 Human toxicity, cancer effects [CTUh] 3.34E E E E E-05 Human toxicity, non-cancer effects [CTUh] 1.02E E E E E-05 Ionizing radiation, human health [kbq U235 eq] 2.23E E E E E+01 Ozone depletion [kg CFC-11 eq] 3.52E E E E E-05 Particulate matter/respiratory inorganics [kg PM2,5-Equiv.] 3.18E E E E E-01 Photochemical ozone formation, human health [kg NMVOC] 1.26E E E E E-01 Resource depletion water [m³ eq.] 4.88E E E E E+00 Resource depletion, mineral, fossils and renewables [kg Sb-Equiv.] 2.86E E E E E-02 S29

30 Blue Phosphor Production - South China Clay REOs Smog Air [kg O3-Equiv.] Resources, Fossil fuels [MJ surplus energy] Ozone Depletion Air [kg CFC 11-Equiv.] Human toxicity, non-canc. [CTUh] Human toxicity, cancer [CTUh] Human Health Particulate Air [kg PM2,5-Equiv.] Global Warming Air, incl. biogenic carbon [kg CO2-Equiv.] Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] Eutrophication [kg N-Equiv.] Ecotoxicity [CTUe] Acidification [kg SO2-Equiv.] 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Mixed REO Production Solvent Extraction Phosphor Production Figure S - 5. Percentage contribution of process stages for blue phosphor production using REOs sourced from ion-adsorption clays S30

31 Green Phosphor Production - South China Clay REOs Smog Air [kg O3-Equiv.] Resources, Fossil fuels [MJ surplus energy] Ozone Depletion Air [kg CFC 11-Equiv.] Human toxicity, non-canc. [CTUh] Human toxicity, cancer [CTUh] Human Health Particulate Air [kg PM2,5-Equiv.] Global Warming Air, incl. biogenic carbon [kg CO2-Equiv.] Global Warming Air, excl. biogenic carbon [kg CO2-Equiv.] Eutrophication [kg N-Equiv.] Ecotoxicity [CTUe] Acidification [kg SO2-Equiv.] 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Mixed REO Production Solvent Extraction Phosphor Production Figure S - 6. Percentage contribution of process stages for green phosphor production using REOs sourced from ion-adsorption clays S31

32 Red Phosphor Production - South China Clay REOs Smog Air [kg O3-Equiv.] Resources, Fossil fuels [MJ surplus energy] Ozone Depletion Air [kg CFC 11-Equiv.] Human toxicity, non-canc. [CTUh] Human toxicity, cancer [CTUh] Human Health Particulate Air [kg PM2,5-Equiv.] Global Warming Air, incl. biogenic carbon [kg CO2-Equiv.] Global Warming Air, excl. biogenic carbon [kg CO2- Eutrophication [kg N-Equiv.] Ecotoxicity [CTUe] Acidification [kg SO2-Equiv.] 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Mixed REO Production Solvent Extraction Phosphor Production Figure S - 7. Percentage contribution of process stages for red phosphor production using REOs sourced from ion-adsorption clays S32

33 Sensitivity Analysis Electricity -3.50% 3.50% Ammonium Sulfate -2.16% 2.16% Citric Acid -1.62% 1.62% Hydrochloric Acid -0.54% 0.54% Aluminium Oxide -0.54% 0.54% Ammonium Bicarbonate -0.54% 0.54% -4.00% -3.00% -2.00% -1.00% 0.00% 1.00% 2.00% 3.00% 4.00% Figure S - 8. Global warming potential sensitivity to a 10% input deviation in blue phosphor using REOs sourced from ion-adsorption clays Ammonium Sulfate -2.64% 2.64% Electricity -2.35% 2.35% Citric Acid -2.05% 2.05% Hydrochloric Acid -0.59% 0.59% Ammonium Bicarbonate -0.59% 0.59% Aluminium Oxide -0.29% 0.29% -3.00% -2.00% -1.00% 0.00% 1.00% 2.00% 3.00% Figure S - 9. Global warming potential sensitivity to a 10% input deviation in green phosphor using REOs sourced from ion-adsorption clays S33

34 Ammonium Sulfate -3.37% 3.37% Citric Acid -2.77% 2.77% Ammonium Bicarbonate -0.99% 0.99% Electricity -0.99% 0.99% Hydrochloric Acid -0.79% 0.79% -4.00% -3.00% -2.00% -1.00% 0.00% 1.00% 2.00% 3.00% 4.00% Figure S Global warming potential sensitivity to a 10% input deviation in red phosphor using REOs sourced from ion-adsorption clays Electricity -3.19% 3.19% Ammonium Sulfate -2.26% 2.26% Citric Acid -1.73% 1.73% Hydrochloric Acid -0.53% 0.53% Ammonium Bicarbonate -0.53% 0.53% -4.00% -3.00% -2.00% -1.00% 0.00% 1.00% 2.00% 3.00% 4.00% Figure S Global warming potential sensitivity to a 10% input deviation in NdFeB magnets produced by TDK technology using REOs sourced from ion-adsorption clays S34

35 Electricity -2.80% 2.80% Diesel, Electricity Generating Set -1.23% 1.23% Hydrochloric Acid -0.90% 0.90% Ammonium Sulfate -0.67% 0.67% Heat, Heavy Fuel Oil -0.45% 0.45% Citric Acid -0.45% 0.45% -4.00% -3.00% -2.00% -1.00% 0.00% 1.00% 2.00% 3.00% 4.00% Figure S Global warming potential sensitivity to a 10% input deviation in NdFeB magnets produced by TDK technology using dysprosium obtained from ion-adsorptions clays and neodymium from monazite/bastnasite minerals S35

36 References (1) Althaus, H. J.; Chudacoff, M.; Hischier, R.; Jungbluth, N.; Primas, A.; Osses, M. Life cycle inventories of chemicals; (2) PE International. GaBi LCA Databases (accessed Jan 1, 2017). (3) Zaimes, G. G.; Hubler, B. J.; Wang, S.; Khanna, V. Environmental life cycle perspective on rare earth oxide production. ACS Sustain. Chem. Eng. 2015, 3 (2), (4) Vahidi, E.; Navarro, J.; Zhao, F. An initial life cycle assessment of rare earth oxides production from ion-adsorption clays. Resour. Conserv. Recycl. 2016, 113, (5) Lee, J. C. K.; Wen, Z. Rare Earths from Mines to Metals: Comparing Environmental Impacts from China s Main Production Pathways. J. Ind. Ecol. 2017, 21 (5), (6) Sprecher, B.; Xiao, Y.; Walton, A.; Speight, J.; Harris, R.; Kleijn, R.; Visser, G.; Kramer, G. J. Life cycle inventory of the production of rare earths and the subsequent production of NdFeB rare earth permanent magnets. Environ. Sci. Technol. 2014, 48 (7), (7) The Global Source for Metals Pricing (accessed Mar 1, 2016). (8) Bare, J. Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI): Traci Version 2.1 User s Manual; (9) Thinkstep AG. GaBi ts: Software and database contents for Life Cycle Engineering, Education Version. (10) Wolf, M. A.; Pant, R.; Chomkhamsri, K.; Sala, S.; Pennington, D. Characterisation factors of the ILCD recommended life cycle impact assessment methods; Publications Office of the European Union: Luxembourg, 2012; Vol. 10. (11) Hedemann, J.; Meinshausen, I.; Frischknecht, R. Documentation EcoSpold; S36

37 (12) Frischknecht, R.; Rebitzer, G. The ecoinvent database system: A comprehensive web-based LCA database. J. Clean. Prod. 2005, 13 (13 14), (13) Beijing Institute of Mining and Metallurgical Technology. Environmental impact assessment report of ton/year separation facility for ion adsorption clay at Fujian Sanming Jinming New Materials Co. Ltd.; (14) Baotou Environmental Science Research Institute. Environmental Impact Assessment Report for the Pollution Control Project at the East Facility of Baotou Huamei Rare Earth High Tech Co. Ltd; (15) Ruilin Engineering and Technology Co. Ltd. Environmental Impact Assessment Report for 2000 ton/year Rare Earth Metal production line at Jiangxi Taihe Changwei New Materials Co. Limited; S37

38 Appendix Critical Materials Life Cycle Assessment Tool (CMLCAT) USER S MANUAL Software Name and Version Number: CMLCAT version 1.0 Authors: Praneet S. Arshi 1,2 Ehsan Vahidi 2, 3 Fu Zhao 1,2,3,* 1 School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, United States 2 Ecological Sciences and Engineering Interdisciplinary Graduate Program, West Lafayette, IN 47907, United States 3 Environmental & Ecological Engineering, Purdue University, West Lafayette, IN 47907, United States *Tel: ; fzhao@purdue.edu S38

39 The Excel based software covers the life cycle of rare earth element production. The data obtained comes from existing research papers, data books, government reports and industry production data. The focus is on Chinese industries and hence the geography of the inputs from technosphere have been altered/ chosen to be close to China in terms of environmental impact, that is, similar processes that are used in China are considered. The purpose of the interconnected Excel sheets is to eliminate the need for a dedicated LCA software and database. All the RE excel files and newly created base process excel files are in ecospold v1 structure. The advantage of having them in ecospold structure is the ability to convert from.xls to.xml. 1 XML file formats can be imported into an LCA software if the researcher desires to do so. Our software is available as a.zip folder and the contents need to be extracted directly to the C drive. Once extracted, the file path should look like C:\RE_LCA... The software is subsequently arranged into interconnected folders: 0. Allocation_CFs (C:\RE_LCA\0.Allocation_CFs) 1. Materials_Energy (C:\RE_LCA\1.Materials_Energy) 2. Mining_Processing (C:\RE_LCA\2.Mining_Processing) 3. Metals_Alloys (C:\RE_LCA\3.Metals_Alloys) 4. Products (C:\RE_LCA\4.Products) 5. Recycling (C:\RE_LCA\5.Recycling) As the Excel files are linked in absolute terms, the file location needs to stay in the C drive. Such absolute links (a problem of using simple Excel files) does not allow the environmental impact calculation mechanism to work on other systems like Mac or Linux. However, one can still use the life cycle inventory as a valuable source of process information. S39

40 Note: Please make sure to add the C:\RE_LCA and its subfolders as a trusted location for Microsoft Excel. The exact procedure is as follows: i. Click File > Options. ii. Click Trust Center > Trust Center Settings > Trusted Locations. iii. Click Add new location. iv. Click Browse to find the folder, select a folder, check the option of subfolders are to be trusted as well, and then click OK. Details about these excel files are provided below: 0. Allocation_CFs Environmental impact is based on TRACI and ILCD characterization. To estimate the environmental impact of resource use and direct emissions of RE processes, we extracted the characterization factors for all impact categories in ILCD and TRACI as given by Thinkstep GaBi software. 2 We did this in order to link our direct emissions and resources use from RE processes to their respective characterization factors. Along with TRACI and ILCD characterization factors, we also have allocation factors calculated for the impact of processes with multi-product output. The user can choose to have mass based allocation or economic allocation and can also choose the percentage share of various REEs in an ore. 1. Materials_Energy The environmental impact of base processes required for various upstream processes are taken from Ecoinvent v3 and has been put in the folder named, 1. Materials_Energy. Within this folder, we have the environmental impact of Ecoinvent processes taken straight from the database (C:\RE_LCA\1.Materials_Energy\Ecoinvent processes). Within 1. Materials_Energy, we have the environmental impacts of altered ecoinvent processes which have been edited to closely S40

41 represent Chinese scenarios. These edited ecoinvent processes are (i) diesel burned in electrical generating set, (ii) heat production using hard coal, (iii) heat production using heavy fuel oil, (iv) hydrochloric acid direct synthesis, (iv) soda production by solway process, (v) steam production in chemical plant, and (vi) sulfuric acid production. There were base materials/energy processes that were required for RE production but were not present in the Ecoinvent database. We created these processes and have the LCI and environmental impact of these processes in their respective excel sheet. Figure 1. List of newly created base materials 2. Mining_Processing Once we have all the base processes required for rare earth element processing, we can call on these unit process excel sheets to identify the impact of processes like mining, beneficiation, acid S41

42 roasting, etc. The folder is sub categorized based on the type of ore used for rare earth extraction. Monazite and bastnasite ores are extracted at Bayan Obo. The process flows as follows: Mining Input: Mine, iron Output: Ore, 17-30% Fe, 5-6% REO Iron Separatation Input: Ore, 17-30% Fe, 5-6% REO Outputs: Iron Ore, 65% Fe & 4-6% REO Tailing Rare Earth Concentration Input: 4-6% REO Tailing Output: 50% REO concentrate from beneficiation Acid Roasting Input: 50% REO concentrate from beneficiation Output: 32% REO RE2(SO4)3 from acid roasting Water Leaching and Chlorine conversion Input: 32% REO RE2(SO4)3 from acid roasting Output: 92% REO RECl3 Solvent Extraction Input: 92% REO RECl3 Output: Individual RE Carbonates Calcination Input: Individual RE Carbonates Output: Individual RE Oxides The output of solvent extraction for monazite and bastnasite ore gives us separated rare earth carbonates. As per source, a certain quantity of individual RE carbonate is produced each year by S42

43 the company. The quantity of each RE carbonate obtained is different and hence the environmental impact of each RE carbonate needs to be allocated. The allocation can be done by mass or economic factors. In the SX process Excel file however, no allocation has been done. The output represents 1 kg of RE carbonates which has roughly 0.07 kg of Lanthanum Carbonate, 0.11 kg of Cerium Carbonate, 0.27 kg of Praseodymium Carbonate, 0.49 kg of Neodymium Carbonate and 0.04 kg of Samarium, Europium, Gadolinium Carbonate. Using this output, we convert the carbonates into oxides producing the same amount of REOs. The allocation factors have been applied after the calcination process and the allocated environmental impact of individual REOs based on mass/economic factors is provided in the subfolder named Compounds (Location C:\RE_LCA\2.Mining_Processing\Compounds). The allocation factors and the choice of mass/economic allocation can be found in the Excel file named AllocationFactors (Location C:\RE_LCA\0.Allocation_CFs). Similarly, we get REOs from Ion Adsorption Clays as well. The source paper provides an LCI to produce mixed RE carbonates. This LCI for RE Carbonate production covers mining, beneficiation, leaching, etc. Mixed REOs were obtained from RE carbonates through calcination process. Solvent Extraction process is required for REO separation. The process flows as follows: S43

44 Rare Earth Carbonate Production Input: Clays Output: Mixed Rare Earth Carbonates Calcination Input: Mixed Rare Earth Carbonates Output: 92% REO, mixed Solvent Extraction Input: 92% REO, mixed Output: Individual RE Oxides The SX file for Ion Adsorption Clay does not have allocated impact of individual RE Oxides. The output is 1 kg of RE Oxides with individual rare earth element oxides having a fixed amount of output. The individual REO environmental impact using pre-calculated allocation factors displayed in the subfolder named Compounds (Location C:\RE_LCA\2.Mining_Processing\Compounds). 3. Metals_Alloys Using REOs obtained from Monazite, Bastnasite and Ion Adsorption Clays, various industries further process it to obtain metals and alloys. Based on industry data by Jiangxi Taihe Changwei New Materials Limited, we were able to calculate the environmental impact of producing certain RE Metals/Alloys. S44

45 4. Products All the rare earth element related outputs we have obtained thus far can be used to produce RE products used in a multitude of industries. So far, we have looked at the production of NdFeB magnets and RE phosphors. 5. Recycling The possible rare earth recycling methods are included within this folder. Two processes, acid leaching of magnets and liquid metal extraction from magnets, show the plausible materials/energy consumed. However, the amount was not available. The LCA results of rare earth elements and its products from CMLCAT version 1.0 have been submitted to a journal. 3 References (1) Hedemann, J.; Meinshausen, I.; Frischknecht, R. Documentation EcoSpold; (2) Thinkstep AG. GaBi ts: Software and database contents for Life Cycle Engineering, Education Version. (3) Arshi, P. S.; Vahidi, E.; Zhao, F. Behind the Scenes of Clean Energy A Life Cycle Analysis of Rare Earth Magnets and Phosphors. ACS Sustain. Chem. Eng S45