Critical solar metal now produced in US
Tellurium being recovered at Kennecott copper mine in Utah Metal Tech News - May 13, 2022
Last updated 5/13/2022 at 1:17pm
As part of a wider initiative to recover critical minerals as byproducts at its current mining operations, Rio Tinto is now producing the tellurium used in thin-film photovoltaic solar panels at its Kennecott copper operation in Utah.
"We are proud to deliver a new domestic supply of tellurium to support the manufacturing of solar panels and other critical equipment here in the United States," said Rio Tinto Copper Chief Operating Officer Clayton Walker.
This key ingredient in cadmium telluride (CdTe) thin-film solar cells happens to be one of the rarest of the stable elements on the periodic table.
"Most rocks contain an average of about 3 parts per billion tellurium, making it rarer than the rare earth elements and eight times less abundant than gold," the United States Geological Survey wrote in a 2015 report on tellurium. "Grains of native tellurium appear in rocks as a brittle, silvery-white material, but tellurium more commonly occurs in telluride minerals that include varied quantities of gold, silver, or platinum."
While deposits with high enough concentrations of tellurium to be economically mined are scarce, small quantities of telluride minerals are often found in copper deposits.
Recovering this copper byproduct accounted for nearly all the 580 metric tons of tellurium produced globally during 2021, roughly 58% of which was recovered at refineries in China.
Traditionally, tellurium was used as an additive to improve the strength and pliability of steel, copper, and lead alloys. In recent years, however, solar and other technological applications have created a new market for this rare element.
USGS estimates about 40% of the tellurium consumed in the U.S. during 2021 went into the production of CdTe solar cells, and 30% went into bismuth-telluride thermoelectric devices for cooling and energy generation. The balance of the tellurium used in America went into alloys and in the processing of rubber.
Solar demand for tellurium is expected to grow substantially with the increased efficiency and growing popularity of thin-film CdTe cells.
"While already enjoying great success in the marketplace, recent scientific developments make it clear that CdTe PV has significantly more potential for dramatically higher module efficiency, lower cost, increased lifetime energy, and more rapid production," said Martin Keller, lab director at DOE's National Renewable Energy Laboratory.
This success and the increased demand for tellurium that comes with it have largely been driven by Ohio-based First Solar Inc., the world's largest manufacturer of thin-film CdTe solar panels.
In early April, First Solar landed three contracts for the installation of 5 gigawatts of its CdTe solar modules by 2025. This includes a solar farm that will deliver electricity to Barrick Gold Corp. and Newmont Corp.'s Nevada Gold Mines, the largest gold-producing complex in the world.
"By partnering with First Solar we also found an innovator that can deliver high performance solar panels with the lowest carbon footprint and the best environmental profile available today," Nevada Gold Mines Executive Managing Director Greg Walker said when the Barrick-Newmont joint venture ordered solar panels for the largest gold-producing complex in the world.
Further details on Nevada Gold Mines' partnership with First Solar can be read at American solar for largest gold complex in the April 14, 2022 edition of Metal Tech News.
Given the growing popularity of CdTe solar panels being produced in the U.S., Rio Tinto invested $2.9 million to build a facility capable of recovering approximately 20 metric tons of tellurium per year as a byproduct of smelting copper at Kennecott.
The recovered tellurium from Kennecott will be refined by 5N Plus, a leading global producer of specialty semiconductors and performance materials.
Rio Tinto says First Solar will be the primary customer for the tellurium now being produced at its famed Kennecott copper mine.
"Rio Tinto's decision to invest in tellurium is a win for responsibly-produced, American solar," said First Solar Chief Manufacturing Operations Officer Mike Koralewski. "We're thrilled that tellurium from Kennecott will play a role in powering our country's transition to a sustainable energy future."
5N Plus will also use Kennecott tellurium to manufacture ultra-high purity semiconductor materials at its facility in Utah.
With the addition of tellurium, Rio Tinto now produces 10 mined commodities at Kennecott. In addition to producing nearly 15% of U.S. copper with the country's lowest carbon footprint, this Utah operation recovers gold, silver, lead carbonate, platinum, palladium, selenium, and now tellurium.
"Utah continues to play a key role in domestic production of critical minerals," said Utah Governor Spencer Cox. "With operations in our state like Rio Tinto Kennecott, we are able to demonstrate to the world how to responsibly make use of our natural resources to move toward a sustainable future."
The recovery of tellurium at Kennecott is part of a larger Rio Tinto initiative to recover more value from its current operations by recovering the small amounts of critical minerals found alongside the primary commodities mined at its operations.
To help accomplish this, the global mining company has partnered with the U.S. Department of Energy's Critical Materials Institute to discover further ways to economically recover critical minerals such as tellurium and lithium.
Last year, the company began producing battery-grade lithium from waste rock left behind from nearly a century of mining borates used in cleaning products at its Boron operation at the western edge of California's Mojave Desert.
Further details can be found at Rio Tinto recovering lithium from Boron in the April 8, 2021 edition of Metal Tech News.
In addition to green energy minerals, Rio Tinto recently installed a facility to recover high-quality scandium oxide – a critical metal used by the aerospace, defense, and high-tech sectors – from waste streams at its metallurgical complex in Quebec, Canada.
More information can be read at Rio Tinto moves into scandium market in the January 20, 2021 edition of Metal Tech News.
By recovering critical minerals at its existing operations, Rio Tinto is reducing the amount of mining waste that needs to be stored while providing a supply of these high-tech materials without the need for new mining – a win-win scenario for industry and the environment.
"Rio Tinto is committed to using innovation to reduce waste in our production process and extract as much value as possible from the material that we mine and process," said Rio Tinto Managing Director Gaby Poirier.