The Second Law and Mineral Extraction

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Various pessimists have cited the Second Law of Thermodynamics as a reason why civilization is doomed. The general idea is that the law shows that the system must run down. This is true of the universe as a whole, so far as we know, but the time-scale is billions of years. The earth is an open system, because it receives energy from the sun. Moreover, the uranium and thorium in the earth's crust can also supply us with energy for billions of years.

One of the particular claims is that the Second Law of Thermodynamics precludes the use of very low grade ores, because the Law imposes energy costs in connection with any separation. Barry Commoner is sometimes credited with this idea. The idea is wrong, because the energy costs imposed by the Second Law of Thermodynamics grow only as the negative logarithm of the concentration and are quite small for the processes of interest.

ECONOMICS OF SUSTAINABILITY: NEO-CLASSICAL VIEWPOINT by Jyrki Salmi quotes and cites some of these arguments.

Other costs, such as material handling and the energy associated with breaking chemical bonds are much larger.

If you accept this, you can stop reading here. However, the Second Law costs are computed directly in the following pages.

Here are are .dvi, Postscript and html versions.

Interesting educational material on thermodynamics is to be found at Chem130a, a UC Berkeley course by Professor K. H. Sauer.

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