There are some practical reasons why a mass-produced technology cannot depend critically on the metal tellurium:
- There is very little new tellurium produced annually, certainly less than 1000 metric tons (t),
- There is very little likelihood that additional tellurium production. based mainly on increased total recovery of tellurium byproducts from base metal ores. can more than double present production in even the most optimistic scenario, and
- Thin film devices have a lower limit of effectiveness both practically and economically, because they have a threshold of thickness below which they do not work.
Where does the idea that there are as yet undiscovered new sources of minable tellurium come from?
The first and most often repeated error is that tellurium is “earth fundamental,” which is supposed to mean that its proportion in the composition of the earth’s crust indicates that there is plenty of it available. This is not true.
In a 2002 paper included in a book called “The Life Cycle of Copper, Its Co-products and Byproducts ” it is pointed out that
“Tellurium is the scarcest of all the byproduct metals, except for gold . Crustal abundance is 0.005 ppm. It is mainly recovered from copper ores (1.5-3 ppm), where it is considerably enriched. There are two known deposits where tellurium is found at much higher concentrations, one in Mexico (0.2%) and one in China. Tellurium has a significant potential use in thin-film cadmium telluride (CdTe) photovoltaic cells.”
When I read press releases such as the one from Unico, on its “In-house Evaluation of Historical Data Regarding Tellurium Levels at the Deer Trail Mine “, I see only an analytical result from a small sample, which tells me nothing about the size, composition, accessibility, or minability of the ore body.
Last year I was asked by a major global investment bank, to comment on a “bismuth” mine in China which was “also rich in tellurium.” I pointed out to the bank’s mining analyst, that it was probably a small deposit of bismuth telluride and that it would be played out long before any capital investment could be recovered. I was told later on that my analysis was exactly correct; the “mine” could have produced a few tons of bismuth and of tellurium for a few years with a grand total production of perhaps 30 t, and was simply therefore not financible as it would have required millions of dollars of infrastructure beforehand.
Unfortunately announcements of this type of “tellurium” mine are now becoming a common occurrence.
Notwithstanding that, I would estimate that if every instance of contained-tellurium in copper, lead, bismuth, and gold were 100% recovered, the total would be less than 2000 t per year.
In fact the general movement of copper mining to lower grades is causing the electrowinning process for refining copper, which brings the tellurium out with gold, silver, platinum, and selenium, to be used less and less, and the increasing use of solvent exchange-leaching hydrometallurgy has decreased the recovery of tellurium (and the other byproduct metals).
The decline of new lead mining in the US. and the increased use of recycling. has also decreased the recovery of byproduct metals such as tellurium from that source.
Total world production of new copper in 2008 was at an all time high of 16,000,000 t. Theoretically that would have produced a maximum of around 50 t of new tellurium were it all recovered. In fact, the global production of tellurium in 2008 was more than 200 t, according to the USGS, and was probably less than 800 t in total from all sources.
Clearly any increase in total tellurium production from base metals, can only be at the margin, since large increases in new global production are not to be expected. It is likely, in fact, that any new additional production would be achieved by increasing the recovery from existing ores rather than by adding recovery from additional production.
There is little likelihood that the global copper and lead industry can maintain 2008 levels, even if the economy should recover, so we may have already seen a peak of tellurium production, since no one will now mine any copper or lead merely to recover some tellurium traces. The economics of that do not and cannot ever work.
There is also no hope of thinning down “thin films” in order to increase the production of photovoltaic cells. The point has already been reached where just enough substance is maintained in current films, to avoid internal resistance build up by just barely maintaining bulk effects.
I believe that the capacity for manufacturing thin-film photovoltaic solar cells from cadmium telluride already exceeds the maximum supply of tellurium available, or that may become available,
Thus, with time, such cells will become uneconomical to manufacture if the enormous capex already in place has to be recovered.
In fact I believe that this has already taken place, and that the only hope for maintaining such an industry is taxpayer subsidies for which I do not see a point or an end.