Critical Minerals Alliances 2022 - September 12, 2022
The rising popularity of thin-film solar cells as a highly effective means of converting sunlight into electricity is creating increased demand for tellurium, amongst the rarest of the stable elements on the periodic table.
Tellurium is a metalloid, one of seven elements with properties that fall between metals like aluminum and tin and non-metals like carbon and phosphorus. These semimetals, which also include silicon and germanium, have natural semiconductive qualities that make them ideal ingredients for photovoltaic solar cells.
While silicon remains the dominant metalloid used in the production of photovoltaic solar cells, cadmium-telluride (CdTe) thin-film cells are a rising star when it comes to harnessing sunlight to fill the world's growing needs for low-carbon electricity.
"Cadmium telluride solar cells have the characteristics of strong power generation capacity, high conversion rate, low temperature coefficient, good weak light effect and high stability," 360 Research Reports penned in a CdTe thin-film solar cell market report.
These characteristics have piqued the interest of the U.S. Department of Energy, which is supporting research focused on overcoming the current technological and commercial barriers for CdTe cells.
According to the 360 Research report, the CdTe solar cell market is expected to top $10 billion in 2027, which is more than double the roughly $4 billion of these thin-film PV cells installed in 2021.
This growth is expected to power up demand for the extremely rare tellurium.
"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," according to the United States Geological Survey.
While tellurium may be one of the scarcest of the elements, this solar-absorbing metalloid often hitches a ride with concentrates produced at copper mines and can be recovered at the refinery.
This has global production of the thin-film solar metalloid closely tied to copper.
"The main concern surrounding tellurium supply is the question of whether or not global copper production can meet the growth in tellurium demand," USGS penned in a 2014 tellurium brochure.
Fortunately, the same low-carbon energy push that is increasing the demand for more solar panels, and the tellurium that goes into the thin-film versions, is also powering the demand for the copper that links the solar panels together and then to the grid, creating the potential for tandem increase in production of these green energy elements.
Traditionally, tellurium was used as an additive to improve the strength and pliability of steel, copper, and lead alloys. In recent years, solar and other technological applications have dominated the demand for this uncommon metalloid.
USGS estimates about 40% of the tellurium consumed in the U.S. during 2021 went into the production of cadmium-tellurium photovoltaic cells and 30% went into the production of bismuth-telluride thermoelectric devices for cooling and energy generation. The balance of this rare metalloid used in America went into alloying additives to improve the machining characteristics of steel and as a vulcanizing agent and accelerator in the processing of rubber.
While one refinery in Texas ships copper anode slimes to Mexico to recover the tellurium, the U.S. is dependent on imports for 95% of this critical metalloid.
Like many of the critical metals (and metalloids), China dominates tellurium production, accounting for nearly 60% of the roughly 580 metric tons of tellurium recovered globally during 2021.
The U.S., however, was able to source about 57% of its 2021 tellurium needs from Canada, with most of the remaining balance coming from Germany, China, and the Philippines.
Driven largely by Ohio-based First Solar Inc., the world's largest CdTe solar panel manufacturer, the popularity of thin-film solar panels and the tellurium that goes into them is expected to grow as the technology matures.
"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.
In early April, First Solar landed three contracts for the installation of 5 gigawatts of its CdTe solar modules to be installed by 2025.
All three companies touted First Solar's U.S. production, cutting-edge solar technology, and leadership in sustainability.
"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 Gold and Newmont joint venture ordered solar panels for the largest gold-producing complex in the world.
This environmental profile includes a recycling program that recovers approximately 90% of the cadmium and tellurium material from old thin-film solar panels, which can then be used to manufacture new modules. Aluminum, glass, and laminates are also recycled for other products.
Considering that First Solar's latest series of thin-film cells are expected to retain at least 92% of original performance at the end of their 30-year warranty, recycling these panels may not be a significant source of tellurium in the near term.
To date, First Solar has invested over $2 billion in its U.S. manufacturing footprint and, when its third factory is fully operational, will directly employ approximately 2,500 people in Ohio, while supporting an estimated 7,000 indirect jobs through its American supply chain.
A supply chain that is going to need increasing quantities of tellurium fed into it.
Seeing the growing need for domestic supplies of tellurium, Rio Tinto invested approximately $2.9 million to build a plant capable of recovering roughly 20 metric tons of this semiconductive metalloid as a byproduct of the copper produced at its Kennecott Mine 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," Rio Tinto Copper Chief Operating Officer Clayton Walker said upon the start up of this facility earlier this year.
The tellurium recovered 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 world-class copper mine in Utah.
"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 accounting for nearly 15% of the mined copper in the U.S., this Utah operation recovers gold, silver, lead carbonate, platinum, palladium, and selenium.
"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."
First Solar said tellurium from Kennecott will likely supplement its current supplies coming from the U.S., Canada, and Europe.
If copper refineries and recycling cannot keep pace with tellurium's solar-powered demand, there is another option – gold mines.
"Recycling solar cells may help, but tellurium-rich films have long lifespans and to date have not been extensively reused. It might become an economic necessity to extract tellurium directly from telluride minerals during gold mining in locations such as Cripple Creek, Colorado; the Sierra Foothills of California; and southeastern Alaska," USGS wrote.
About a decade ago, First Solar considered mining its own tellurium from the Klondike gold-silver project about 100 miles northeast of Durango, Colorado. When the company decided to forego its own tellurium mining venture, First Tellurium Corp. picked up this property where samples with as much as 3.3% tellurium, along with 33.7 grams per metric ton gold, and 364.8 g/t silver, were collected.
"The Klondike property has by far the highest tellurium grades in rock samples of the hundreds of prospects and mines we examined in the U.S. and Canada from 2006 to 2011," said John Keller, the previous mineral exploration manager for First Solar and a current consultant to First Tellurium. "Some samples at Klondike were an order of magnitude higher in tellurium grade than any others we collected in the U.S. or in Canada."
Early in 2022, Keller collected additional samples in preparation for a drill program at Klondike. One of the rocks collected during this sampling contained 1.1% tellurium, 3.76 g/t gold, and 130 g/t silver, along with copper, zinc, and lead.
"We knew from First Solar's work that Klondike was a prime tellurium property," said First Tellurium CEO Tyrone Docherty. "These results provide a solid launch point for further exploration in 2022."
The Juneau Gold Belt of Southeast Alaska, the Kirkland Lake and Red Lake districts of Ontario, and the Yellowknife Mining District in Northwest Territories are other gold mining areas in North America particularly enriched in tellurium.
Recovering this solar metalloid from precious metals deposits, however, would require new processes.
"Tellurium concentrations are highest in precious-metal-bearing deposits that contain abundant telluride minerals; these deposits, however, currently are not significant sources of tellurium because the ore-processing method to extract gold and silver is not amenable to tellurium recovery," the USGS reported in a 2018 report.
As thin-film CdTe solar panels gain in popularity, precious metal miners might join the ranks of copper refineries in providing byproduct supplies of this critical metalloid that efficiently converts sunlight into electricity.