The Exergy of the Earth and its Mineral Resources - Thanatia: The Destiny of the Earth's Mineral Resources - page 349

amounts of energy are available on Earth, much more than humans could ever hope
to exploit. The depletion of fossil fuels should thus not present a problem at least
in the medium term, as there are many energy alternatives, albeit that the way of
recovering them needs to be developed, so as to be economically competitive.
In the same way, vast amounts of minerals are available since the whole crust
is composed of minerals. However, there is a limited amount of concentrated (and
subsequently readily extractable) mineral deposits which are irreversibly being lost.
In the short term, substitution among minerals will be possible with technological
development but this can only occur when other mineral resources are available.
Unfortunately, non-fuel minerals cannot be easily replaced by renewable resources,
although there are some promising experiences that substitute inorganic with or-
ganic materials (such as conductive nanomaterials and graphene).
Furthermore, the mines with the highest ore grades have been already exhausted.
Those remaining require greater energy inputs which grow exponentially as grade
deposits decline. Theoretically, should enough energy be introduced to an extraction
process, any substance could be taken from the crust. However, even if technolog-
ically possible, converting bare rock into an inexhaustible mine would imply an
immense economic and energy input coupled with a devastating cost to the envi-
ronment. In short, to turn over virgin forests, mountains, oceans and landscapes
in order to salvage (or even scavenge) the last concentrated tonnes of strategic mi-
nerals (a current practice which is common within the gold, diamonds and coltan
industries) is surely not the best planetary scenario. To avoid this situation, reuse,
recycling and especially, the search for a dematerialised society becomes essential
in the true path towards sustainability. This issue will be addressed in Part 4.
11.4 Summary of the chapter
In the first part of this chapter, the standard thermodynamic properties i.e. stan-
dard enthalpy, Gibbs free energy and chemical exergy of the main constituents
(more than 300 natural substances) of the outer Earth's spheres have been pro-
vided. The absolute chemical exergy of the atmosphere, hydrosphere and upper
continental crust have been estimated at 4:410 2 , 1:010 6 and 6:010 6 , respec-
tively. These approximations provide an order of magnitude of the huge planetary
chemical wealth.
The second part of this chapter provided an inventory of the most important
resources on Earth (including energy and non-fuel mineral resources), expressed
through a single unit of measure: exergy. There is an enormous amount of energy
sources on Earth, both renewable and non-renewable. There are also many energy
alternatives that could replace conventional fossil fuels should they become depleted.
But before this occurs the technology for the recovery of these potential alternatives
needs to be further developed.