Haque, and three co-authors, reported in 2014 that rare earths are used in the renewable energy technologies such as wind turbines, batteries, catalysts and electric cars. Current mining, processing and sustainability aspects have been described in this paper. Rare earth availability is undergoing a temporary decline due mainly to quotas being imposed by the Chinese government on export and action taken against illegal mining operations. The reduction in availability coupled with increasing demand has led to increased prices for rare earths. Although the prices have come down recently, this situation is likely to be volatile until material becomes available from new sources or formerly closed mines are reopened. Although the number of identified deposits in the world is close to a thousand, there are only a handful of actual operating mines.
Prominent currently operating mines are Bayan Obo in China, Mountain Pass in the US and recently opened Mount Weld in Australia. The major contributor to the total greenhouse gas (GHG) footprint of rare earth processing is hydrochloric acid (ca. 38%), followed by steam use (32%) and electricity (12%). Life cycle based water and energy consumption is significantly higher compared with other metals.
The authors concluded that the availability of rare earths is in transition from a temporary decline due mainly to quotas being imposed by the Chinese government on export to becoming more available with production increasing elsewhere in the world. The reduction in availability coupled with increasing demand led to increased prices for rare earths in 2012 and 2013, but prices have fallen from their peak values. The increasing demand for rare earths in a range of applications means that the rare earth market is likely to be demand-driven for some time to come. This is particularly the case for rare earths used in high field strength magnets. Price fluctuations are therefore likely to vary until such time as new rare earth deposits supply the market or formerly closed mines are reopened.
The rare earths at greatest risk are those that have high volume, low reserves and significant dispersion. Essentially, rare earth elements are concentrated from very low grade in the ground and then dispersed into various equipment in small quantities. Thus, unless recovered, there is greater chance of these materials lost with the disposal of the equipment. Recycling and recovery of rare earth poses challenge in terms use of energy to collection, reprocessing and reproducing products at specification that can replace primary metals.
The major contributor to total GHG footprint of REE processing is hydrochloric acid (ca. 38%), followed by steam use (32%) and electricity (12%). Overall, 51% of GHG is due to use of energy in various forms (i.e., diesel, steam, fuel oil and electricity). The remaining minor elements are from other chemicals and transport. To reduce GHG impact of REE processing, the focus should be on how to reduce the acid and energy consumption during processing.
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