Several metals are increasingly being used in modern technologies either as essential part of the technologies or to enhance their efficiencies including indium, germanium, gallium, tellurium, selenium, cadmium, silver, lithium, cobalt, and a number of rare earth elements. These metals are mostly coexisting with other metals in nature in low concentrations, and often co-produced with their host metals, if not discarded without being processed, in a few number of countries. For example, indium, germanium, silver, cadmium, tellurium, and selenium required for PV solar technologies are mostly produced as companion metals to zinc and copper, neodymium, dysprosium, terbium, and praseodymium required for wind power (WP) and electric vehicles (EVs) technologies are produced with other rare earth elements (REEs) mainly from other metals deposits, and cobalt required for Li ion batteries (LIB) is mainly produced with nickel and copper.
Increasing demand for the metals required for emerging technologies may result in increasing companion and host metals production with several implications on the sustainability of these technologies, especially if companion and host metals demand does not increase at the same level as target metals. This is the so called supply-demand balance problem, which is the balance between metals demand and natural presence of metals in ores.
The research presented in our recent paper in communications Earth and Environment is part of an on-going project on material-energy-water-climate nexus. In our earlier work published in the International Journal Energy and Scientific Reports, we highlighted the impacts of energy transition minerals (ETM) availability and production capacity on the realization of global and national energy and transportation transition scenarios, and the impacts of ETM production on the energy and water demand and climate change. These studies show that several metals availability and/or production capacity may constrain the development of energy transition technologies on global and national levels, including neodymium and dysprosium for WP, cobalt, lithium, and natural graphite for EVs, and tellurium, indium, and germanium for PV solar, especially if no measures such as increasing material efficiency, increasing technologies life time, and increasing metals recycling have been taken. In addition, these studies show that the amounts of energy, water, and CO2 emissions associated with ETM production are significant and expected to increase unless energy and water efficiencies and the supply of energy from renewable technologies in materials production processes have been increased.
The impacts of ETM on emerging technologies however go beyond the minerals directly utilized in these technologies. Therefore, Our paper evaluates the implications of the increasing demand for neodymium, dysprosium, terbium, and praseodymium in WP and EVs technologies on the supply of other naturally coexisting REEs and consequently the environmental impacts associated with the two technologies and their long term sustainability. Several options for possible mitigation of the supply-demand balance problem, on demand and supply sides of metals, have been analysed including reducing WP and EVs shares in electricity production and vehicles market, reducing REEs content in the technologies, limiting target metals supply to their rich deposits, increasing target metals recycling, producing target metals from other sources including coal, bauxite, and phosphorus, and increasing other co-produced metals demand.
It has been found that the highest oversupply of all REEs is the result of dysprosium demand in the two technologies. Annual energy, water, and CO2 emissions (E-W-CO2) associated with the production of oversupplied REEs by 2050 is expected to be between 4.9 and 6.2 times those associated with neodymium and dysprosium production, and cumulative E-W-CO2 is expected to be between 5.5 and 6.4 times (Fig. 1). Annual CO2 emissions associated with REEs demand and oversupply by 2030 is expected to be between 22% and 29% of the CO2 emissions reduction expected in the IEA EV30@30 scenario due to EVs use without changing the electricity mix, between 19% and 26% of CO2 emissions reduction due to power grid decarbonisation, and between 10 % and 14% of CO2 emissions reduction due to EVs use and power grid decarbonisation. The impacts associated with the production of REEs are not limited to CO2 emissions but there are other impacts mainly related to the radioactivity of some ores. Dysprosium demand is expected to lead to the production of significant amounts of ThO2 and U3O8.
Fig. 1: Cumulative energy, water, and CO2 emissions associated with Nd and Dy production and oversupplied REEs in a high and low demand scenarios and an average energy, water, and CO2 intensities of metals production
Although the impacts associated with oversupplied REEs as a result of dysprosium demand are significant, the increase in resources efficiency, on the demand side, reduces CO2 emissions by 39%. On the supply side, supplying dysprosium from its rich deposits reduces CO2 emissions by 78%, while dysprosium recycling reduces CO2 emissions by 35%. CO2 emissions could be reduced by about 84.3% if dysprosium recycling and supply from dysprosium rich are combined, while could be reduced by 90% if dysprosium recycling, supply from dysprosium rich deposits, and resources efficiency are combined. REEs concentrations in coal, bauxite, and phosphate gypsum sources are relatively low although available in large quantities. In terms of supply-demand balance, coal and bauxite have lower ratios of other REEs to dysprosium production compared to traditional deposits, while phosphate gypsum has higher ratios (Fig. 2).
Fig. 2: Ratios of dysprosium production to other REEs production from coal, bauxite, phosphate gypsum and all traditional deposits
Supply-demand balance problem associated with metals required for emerging technologies is not limited to increasing demand for critical metals used in these technologies and the possible oversupply of other companion and host metals, but also to other metals in which increasing use of emerging technologies may result in reducing their demand. For example, LIBs are expected to replace nickel metal hybrid (NiMH) batteries and consequently reduce lanthanum, cerium and other REEs demand. The increasing use of light-emitting diode (LED) technology may reduce yttrium, lanthanum, and cerium demand. Both LIB and LED would increase supply-demand balance problem related to neodymium and dysprosium increasing demand. Increasing use of EVs is expected to reduce lead demand in conventional vehicles, consequently either its production from secondary sources or extraction from primary sources has to be reduced. Reducing lead production from secondary sources would have adverse environmental impacts, while reducing its production from primary sources would reduce the supply of its companion metals; bismuth, antimony, barium, tellurium, selenium, and indium, some of which are essential for emerging technologies. Moreover, EVs development is expected to reduce palladium and platinum use, which would make platinum available for fuel cells but could have negative impacts on palladium. Although palladium is produced mainly as companion metal to platinum and nickel, reducing its demand may reduce the profitability of mining operations in which palladium contribution is considerable and consequently impact the supply of other companion metals.
Therefore, it is important to study technologies together rather than independently, to include analyses of connections among metals, and to consider resources nexus to better evaluate the sustainability of emerging technologies.
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