Friday, June 01, 2007

Digging-up the Family Silver (...Platinum etc).

We live on a planet with finite resources, and yet use them up with alacrity in the false assumption of limitless growth. I read a recent statistic that "if all the world's 500 million vehicles in use today were re-equipped with fuel cells, operating losses would mean that all the world's platinum would be exhausted within 15 years." In a previous posting, I estimated that there were probably around 35,500 tonnes of platinum available as a reserve on Earth, 90% of it in two mines in South Africa and most of the rest in Russia. Hence, each vehicle would account for 35,500 tonnes x 1000 kg/tonne x 1000 g/kg /500,000,000 = 71 grams of platinum. For 700 million of them, as I understood the figure to be, this amounts to 51 grammes each.

In my article "Platinum Barrier to Fuel Cells", I worked-out, assuming that pledged technology (here we go again!) would come to our rescue, that there is enough platinum at a putative 12 g per "highly improved" fuel cell to supply 3 billion cars, but the real problem is that only relatively limited quantities of platinum can be produced each year, and so other resources (principally oil) will have run-out long before we might replace our oil-fuelled fleet by fuel-cell driven cars. This ignores the likely prohibitive difficulty in inaugurating the infrastructure for the hydrogen to run them with. Either way platinum is a scarce and precious resource and cannot be counted upon to match current and continuing demands for it. Contemporary fuel-cells contain around 50 - 100 g of platinum each, which is close to the above estimates.

Currently, even in the absence of fuel-cells, around 40% of the world's platinum is used in catalytic-convertors (CC's) to keep levels of exhaust gases such as NOx down, which is coincidently the same amount as is used to make jewelry. It is fascinating that the "dust" and litter routinely swept off the streets may contain of the order of parts per million (ppm) of platinum, emitted into the air from the platinum-based catalysts that are the heart of CC's, similar to the 3 ppm typical of the ores in the South African platinum mines. It may therefore be feasible to "mine" the dust from road-sweeping machines to recover its platinum.

Platinum is only one of the elements likely to run-short in a few decades or so. Indium, used for solar cells and LCD's may run-out in 10 years, impending a further need to develop alternative photo-voltaic (PV) technology, beyond the difficulty in providing enough pure-silicon to fabricate silicon-based cells on the grand scale. Dye-cells (e.g. Gratzel-cells) begin to look particularly attractive, even if the "dyes" will be made from oil, emphasising the terrible waste of simply burning oil as a fuel, when we also need it as a chemical feedstock. In my opinion, it would be more to the point to preserve as much conventional crude oil as possible as a raw material for chemical manufacture, because what will our industries use otherwise once it has gone, or is absurdly too expensive to use?

Some salient points are made by the following list of elements, world total reserve of each, their time of exhaustion based on current rates of production and main uses for them:

Aluminium, 32,350 million tonnes, 1027 years (transport, electrical, consumer durables)
Arsenic, 1 million tonnes, 20 years (semiconductors, solar cells)
Antimony, 3.86 million tonnes, 30 years (some pharmaceuticals and catalysts)
Cadmium, 1.6 million tonnes, 70 years (Ni-Cd batteries)
Chromium, 779 million tonnes, 143 years (chrome plating)
Copper, 937 million tonnes, 61 years (wires, coins, plumbing)
Germanium, 500,000 tonnes (US reserve base), 5 years (semiconductors, solar cells)
Gold, 89,700 tonnes, 45 years (jewelry, "gold-teeth")
Hafnium, 1124 tonnes, 20 years? (computer chips, power stations)
Indium, 6000 tonnes, 13 years? (solar-cells and LCD's)
Lead, 144 million tonnes, 42 years (pipes and lead-acid batteries)
Nickel, 143 million tonnes, 90 years (batteries, turbine-blades)
Phosphorus, 49,750 million tonnes, 345 years ( fertilizer, animal feed)
Platinum/Rhodium, 79,840 tonnes, 360 years for Pt (jewellery, catalysts, fuel-cells, cat-convs.)
Selenium, 170,000 tonnes, 120 years (semiconductors, solar cells)
Silver, 569,000 tonnes, 29 years (jewellery, cat.-convs.)
Tantalum, 153,000 tonnes, 116 years, (cell-phones, camera-lenses)
Thallium, 650,000 tonnes, 65 years (High Temperature Superconductors, Organic Reagents)
Tin, 11.2 million tonnes, 40 years, (cans, solder)
Uranium, 3.3 million tonnes, 59 years (nuclear power stations and weapons)
Zinc, 460 million tonnes, 46 years (galvanizing).

These figures are based on known reserves and of course more might be found if it were explored for. However, new technologies are likely and the developing nations are aspiring to a "Western Lifestyle" so minerals are being exhausted at a relentlessly growing rate.

It is predicted that if new technologies do appear and with the growth in world population, some key resources will be used up quite rapidly, e.g.:

Antimony, 15 - 20 years.
Hafnium, 10 years.
Indium, 5 - 10 years.
Platinum, 15 years.
Silver, 15 - 20 years.
Tantalum, 20 - 30 years.
Uranium, 30 - 40 years.
Zinc, 20 - 30 years.

It is worth observing that the distribution of these minerals is of course uneven, as I noted above about platinum, and the US currently imports 90% of its "rare earth" metals from China. We know all too well also that most of the world's oil is in the Middle East. In concluding this posting I am left with a sense of living on borrowed-time.

Related Reading.
(1) David Cohen, "Earth Audit", New Scientist, 26th May 2007, p. 35.


Anonymous said...

Here is the reference link obviously the main article is behind pay-per-view.

Unknown said...

This is a dumb article that is more that a little off base.

Listing Aluminum among the elements that we're going to run short of for instance. Der.

Professor Chris Rhodes said...

Dear Dezakin,

please enlighten me, if you can, as to why it is "off-base"?

We have plenty of aluminium, so that is the yard-stick; in comparison, quite a few of the other elements, especially those that computers, solar panels, cell phones, HTC's etc, will rely on, are going to limit these technologies.

Now that scares me, I don't know about you?

Platinum is a real problem to extract in quantity, and so I doubt sufficient of it can be supplied and rapidly enough to implement the fuel-cell generation of cars before the oil runs-short. Hence it might be more appropriate, rather than investing huge resources into a "hydrogen economy", to instead begin coal-liquefaction etc. on the large scale.

Pushing technologies that will never amount to much because the resources to sustain them will run-out in a few decades really is "dumb".

And yet Bush is pushing "hydrogen" is he not, along with all its other many disadvantages? Der. (or is it ..."Doh" over there?).

Rael said...

The world's economically recoverable reserves of the main aluminum source, bauxite, will run out in ~70 years with 2%/yr growth in extraction. U.S.G.S data.

From: "(Lester Brown Plan B 2.0, 2006)

Professor Chris Rhodes said...

Thanks for the information Rael!

Just 70 years, not 1027 years as mentioned in the New Scientist article? That's pretty frightening especially as some people are talking about "Aluminium batteries", in terms of "limitless" Al supplies.

I guess recycling Al more efficiently might help to ease the shortfall your statistic implies, and I think this applies to most minerals and resources.

More efficient use/recycling and recovery, and processing poorer ores? However, a gearing-down to some extent of just how much we do consume, in terms of both raw energy and resources, seems inevitable.


Anonymous said...

Aluminum production is likely to be substantial long after bauxite peaks, though probably with increased energy, economic and environmental costs.

"[Aluminum is] the third most abundant of all elements in the Earth’s crust, making up 8% of the crust by weight. Only silicon and oxygen are more plentiful.
Alternative sources of aluminum might someday include kaolin clay, oil shales, the mineral anorthosite, and even coal waste. However, as long as bauxite reserves remain plentiful and production costs are low, the technologies to process these alternative sources into alumina or metallic aluminum will likely not progress beyond the experimental stage."

Professor Chris Rhodes said...

Fair point Rael: there is plenty of aluminium overall, but it is the economics of extracting it that determines the "reserve" in contrast to the large "resource" there is altogether.

This is true of other elements too, and sometimes people talk about how much there is of various metals in the oceans. For example, if you add-up all the uranium in seawater, it may be concluded that there is enough to run nuclear fission for 4.5 Billion years, but you would need to extract the whole volume of it to get that much!

I'm joking slightly, and I'm sure more of other metals will be found, but the costs of good will go-up, and so if a computer of a cellphone were to suddenly cost thousands of pounds, the market would fall.

The amount of a reserve that can be costed seems to be self-limiting when driven by such market-forces.

Cheers, Chris.