Geology Reference
In-Depth Information
The authors have presented in this chapter the Physical Geonomics methodol-
ogy, which is aimed at measuring the costs that Man saves (avoided costs) thanks
to having minerals concentrated in mines and not dispersed throughout the crust.
The exergy replacement cost provide a measure of the “natural bonus” lost through
extraction. It quantifies value, as it relates to concentration, chemical composition
and cohesion, key aspects that determine whether a mine is exploitable. Together
with mining, beneficiation, smelting and refining costs, it is a measure of the ther-
modynamic rarity of mineral resources, understood as the amount of exergy needed
to obtain a mineral from bare rock (from Thanatia).
Exergy replacement costs allow for a more comprehensive LCA by including a
new stage in the analysis: the grave-to-cradle path, thereby closing the material's
cycle: cradle-grave-cradle. This path is based on quantifying the exergy costs re-
quired to replace the extracted minerals with current available technologies, from
a completely degraded state (Thanatia), to the conditions currently found in Na-
ture. Thanatia is a conceptual crepuscular planet which is quantitatively analysed
through an estimated reference model of the Earth's commercial end, where all
resources have been extracted and dispersed, and all fossil fuels have been burnt.
However, before one is able to construct any theoretical planet, one must un-
derstand the reality in which it is based, i.e. the geochemistry of the Earth (atmos-
phere, hydrosphere and crust). Subsequently, one must evaluate the resources and
the way and speed at which society exploits them. Technology plays an important
part in this and it is therefore imperative that its current state is determined, so
that a comprehensive calculation of exergy costs may be undertaken. This will be
seen in Part 2 of this topic.
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