Unrecovered byproducts from US mines could meet national demand for all but two critical minerals and rare earth elements, a new report has found.
A team from the Colorado School of Mines built a database of annual production from metal mines in the US. The researchers used a statistical resampling technique to pair the data with the geochemical concentrations of 70 critical minerals in ores, recently compiled by geologic surveys. This allowed them to estimate the quantities of critical minerals that are mined and processed every year but not recovered. They conclude that unrecovered byproducts could meet the demand for 68 of the minerals, but not for platinum and palladium.
Metals such as cobalt, lithium, gallium and rare-earth elements like neodymium and yttrium are currently being discarded as tailings of other mineral streams like gold and zinc, says Elizabeth Holley, a mining engineer at Colorado School of Mines, who led the work. The tailings must be stored and monitored to prevent environmental contamination.
‘The challenge lies in recovery,’ Holley says. ‘We need to do a lot more research, development and policy to make the recovery of these critical minerals economically feasible.’
‘We show where each critical mineral exists and the sites at which even 1% recovery of a particular critical mineral could make a huge difference, in many cases dramatically reducing or even eliminating the need to import that mineral,’ she adds.
One example is cobalt – a key component in electric car batteries, and a byproduct of nickel and copper mining. According to Holley’s team, recovering less than 10% of discarded cobalt from US mines would be more than enough to fuel the entire country’s battery market. And recovering less than 1% of discarded germanium would meet all industry’s needs; it is used in electronics and infrared optics, and is present in zinc and molybdenum mines.
It’s surprising how little extra production would be needed to satisfy current raw material requirements
Frances Wall, University of Exeter
However, Holley notes that mine operators will need incentives to incorporate additional processing infrastructure. ‘Although these elements are needed, their market value may not be sufficient to motivate operators to invest in new equipment and processes without the right policies in place.’
‘The novelty of this [report] is in its mathematical treatment of new data sets to compare the potential of US metal mines with the raw material imports of critical minerals into the US,’ says Frances Wall, an applied mineralogist at the University of Exeter. ‘It was surprising to see how little extra production would be needed to satisfy current raw material requirements for some elements.’
However, Wall points out finding and processing the by-product elements may not be easy. For example, the elements’ distribution may be uneven through the rocks in the ore deposit, and some rarer elements might be distributed in multiple minerals at very low quantities, making their recovery less financially viable.
Even when all these issues have been overcome, mining companies may need a lot of persuasion to risk changing their processes and business models, she adds. ‘It is well known, for example, that there are rare earths in phosphate deposits, but phosphate mines do not yet produce rare-earth byproducts.’
This view is shared by Colin Church, chief executive of the Institute of Materials, Minerals & Mining in London. ‘This research suggests there could be significant value in metals mining waste in the US, though of course the commercial, environmental and chemical practicalities in getting hold of it are going to remain significant barriers,’ he notes.
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