Mr. Torbert seems remarkably free to criticize research that he has evidently not read.   If he had read these papers he would realize that they consider all of the factors that he raises below. From the general tone of his response I suspect that he also thinks that global warming is a myth!

 

Consider the sunny optimism in his second paragraph – he cheerfully assumes that we can simply move to extract needed metals from materials of much lower grade. The problem with this scenario is that we would need vastly more energy and water to extract needed metals from these materials (called “backstop” ores in the literature) than even the most optimistic scenarios can provide. These needs are spelled out in great detail for copper in Towards a New Iron Age? (1987) – note that Gordon’s coauthors on this were Brian Skinner, the eminent ore geologist, and two economists (one of them a Nobel Prize winner). For copper, the average crustal concentration is 70 ppm, but the “backstop” is in certain basic igneous rocks that are enriched to about 0.05% Cu. Their model calculated the likely cost of producing a kilogram of copper from this resource (in 1987) at $121 per kilogram! But cost is not the killer factor. They suggest that without substitution, the likely annual need for newly mined copper in 2090, given their estimates of population size and patterns of consumption, would be 15 x 10 to the ninth power kg. Supplying this at a grade of 0,05% Cu would take 275 open cast pits the size of Bingham Canyon, and need 2.2 x 10 to the eleventh power liters of water per day – 20% of the average flow of the Mississippi. The energy required to extract this copper from 0.05% Cu rock (in which the copper is not present as copper minerals, but within silicate minerals like pyroxenes) would need an energy use rate of 0.48 x 10 to the thirteenth watts – almost half of the entire world’s use of electricity in 1987. Can we substitute for copper? As the new paper points out, the stock of copper employed for industrial purposes in the USA has declined in the last thirty years as American manufacturing heads to China (where soaring demand for copper has more than doubled the price in the last two years) but the total stock of copper  per capita in the US keeps steadily increasing – largely driven by wiring in buildings, cars, and telecommunication. It’s difficult to see copper being replaced by aluminum for these purposes, as the electrical conductivity is lower and the problem of making connections much greater.

 

The point here is that all of these factors have been considered quite carefully – one can argue about the actual figures used in the model, but the trend is quite clear.  Similar constraints – water, energy, cost – apply to the extraction of the tiny amounts of platinum in chromite sands, as proposed by Mr. Lifton.  But if there’s one thing we do know about America today is that most Americans just don’t want to be bothered with the details, or with long-range planning.  We just assume that everything will be fine in the long run; when the perfectly predictable crises arrive, we just proclaim our surprise and look for a scapegoat. The levees broke in New Orleans? But no-one could have predicted that!  American companies are way behind in the technologies for high-speed rail, high-efficiency motor vehicles, wind power? But how could we have known that there would be huge world markets emerging for these technologies!  And so it goes……..surely we’ll think of something on the fly!  

 

 

-----Original Message-----
From: Arch-Metals Group [mailto:[log in to unmask]] On Behalf Of Torbert, Barton
Sent: Tuesday, February 28, 2006 8:52 AM
To: [log in to unmask]
Subject: Re: When will we ru out of exploitable metal ores?

 

I make the following comments from my experience in the mining industry.  The point that most people miss is that mining is more about economics rather than processing of natural concentration of a useful elements.  It is all about the cost of concentrating an element from a source weighed against the price that element can be sold for.  The term “ore” has nothing to do with high geological concentrations of an element or compound.  It has to do with a material that today can be have present technology applied against to create a profitable business operation from what material you have on hand.

 

Gordon’s work does show that we are using up the easy to reach, higher concentration sources.   But that does not mean we are totally running out of

material to facilitate our technology.   Pick any type of rock, or material from a landfill, and you can find every element in the periodic table.  True the concentrations may be very small, but they are there.  The issue is do you have the technology to extract the element(s) of interest at a cost lower than you can sell the element(s) for.  As naturally occurring, highly concentrated, easy to reach (we are generally talking about shallow depth of burial) resources are exhausted, the price of these elements will rise making lower grade occurrences economically feasible.  Also as “necessity is the mother of invention”, the new technology will be brought into existence to more efficiently extract the desired element(s) from source with lower concentrations. 

 

The gloom-and-doom scenarios that are presented as the inference of the projections made by works like Gordon’s does not tell the whole picture.  It is true the loss of our traditional sources of metal will put a crimp on our life styles.  But we are not going to only be stuck with the recycling of already existing final product. 

 

Bart

 

 

 

All members of this list will be aware of Bob Gordon’s contribution’s to archaeometallurgy over the years, but many will not be aware of the fact that he has made profound contributions to many other areas of science. He has a long-standing interest in the potential exhaustion of the earth’s non-renewable resources – see in particular Towards a New Iron Age? Quantitative Modelling of Resource Exhaustion, co-authored with T.J. Koopmans, W.D, Nordhaus and B.J. Skinner (Harvard University Press, 1987).

 

For the latest update on this line of research, see R.B. Gordon, M. Bertram and T.E. Graedel, “Metal stocks and sustainability”, Proceedings of the National Academy of Sciences 103(5)1209-1214, 2006. In this Bob and coauthors examine when we might expect to exhaust the earth’s stocks of exploitable ores of copper, zinc, platinum, tin, silver and nickel, given prior assumptions about the size of the earth’s population by 2050, recycling, loss of metals to corrosion and landfills, and general standards of living (and thus consumption). They suggest that platinum ores will be the first to be exhausted, followed by zinc and copper. After that time all users of these metals will have to make do with what can be recycled.

 

David Killick
Associate Professor
Department of Anthropology
University of Arizona
Tucson, AZ 85721-0030
U.S.A.

phone (520) 621-8685

fax       (520) 621-2088