🚀 go-pugleaf

John Roland has to make a better case than that if he wants to show
that we cannot continue with our present methods of mineral extraction.

1. He gives no actual figures.  The Statistical Abstract of the United
States gives figures for the fraction of the GNP taken up by the
mineral extraction industries.  I won't post it in this message, hoping
Roland will look it up himself.  After all, if he were right that
extreme recycling will  eventually be required but not for 200 years,
then any efforts he puts into designing compact cities will be only
a historical curiosity when the time comes to build them.

2. The only reason for mentioning the negative logarithm of the
concentration is that some cultists, e.g. Paul Ehrlich and (I believe)
Barry Commoner, have used the second law of thermodynamics as an
incantation.  They say, quite correctly, that the second law tells us
that the cost of getting a kilogram of metal from an ore must go up as
the concentration goes down.  What they don't say is how extremely
slowly it goes up.

3. The cost of the energy required by the second law is certainly
a small fraction of the cost of getting metals from ores.  Shovelling
dirt is probably the main cost.  What it is now, and how it will go
up in the future depends on actual engineering practice.  There are
books on that in engineering libraries.

4. I offer one data point.  Chile still has lots of high concentration
copper ore.  The U.S. does not.  In fact the U.S. is mining some ores
whose concentration of copper is only ten times the concentration in
random rock.  It competes with imported Chilean copper in price.


--
John McCarthy, Computer Science Department, Stanford, CA 94305
*
He who refuses to do arithmetic is doomed to talk nonsense.