Geology Reference
In-Depth Information
Exergoecology has been developed thus far for analysing inorganic substances 11
and can be divided into two distinct branches: Physical Hydronomics and Phy-
sical Geonomics 12 . The former investigates water resources through the exergy
assessment of ecological costs, i.e. those regarding the alteration of the physical
and biological aspects of water bodies due to human activities (Valero et al., 2007;
Martinez, 2009). The latter, which is the focus of this topic, is concerned with
mineral resources. Specifically, it quantifies the amount of exergy that one saves
when resources are extracted from a mine, instead of from a pool of materials con-
tained in a hypothetical Earth that has reached the maximum level of deterioration.
The authors coined this degraded state Thanatia, details of which can be found in
Chap. 10. The objective of Physical Geonomics is thus to determine the exergy
bonus that Nature provides by having minerals concentrated in mines instead of
having them dispersed throughout the Earth's crust. It can also be used alongside
extraction data, to assess how Nature's stock is being degraded and dispersed by
mankind and at which rate.
The authors will now proceed to outline, through an example, the difference
between Physical Geonomics and other cradle to grave exergy approaches (led by the
thermo-ecological method explained in Sec. 2.6.3.4). In primary copper production,
conventional exergy analysis accounts for the exergy input of all industrial processes
involved in the extraction, beneficiation, refining, manufacture, use and disposal of
copper, including emission and waste abatement in a cradle-to-grave approach (see
Fig. 3.2). In short, one calculates its exergy cost (or embodied exergy) by measuring
the whole exergy consumed from the initial to the final state.
Physical Geonomics, in contrast, closes the cycle of Fig. 3.2 in the opposite
direction via a “grave-to-cradle approach”. This is because it is concerned with the
amount of exergy needed to return copper from the depleted state of Thanatia to
the conditions of the mine where it was originally found. The exergy difference
between Thanatia and the mine increases with the mine's quality (i.e. with its
ore grade). This means that as the mineral deposits become exhausted, the exergy
difference between Thanatia and the mine reduces. At the threshold where all
natural resources have been extracted and dispersed, this difference is equal to zero
11 Jorgensen and Svirezhev (2004) and Jorgensen (2006) have also applied similar concepts to
ecosystems, introducing the term Eco-exergy as a measure of how far an ecosystem is from ther-
modynamic equilibrium, that is to say how developed an ecosystem is.
12 The term Geonomics was coined by Gregory Antipa (1909) and means land management. The
geonomist considers that land, water, climate, biosphere and humanity form a whole and depend
on each other. Learning to decipher the past allows for a better understanding of the present and
a better anticipation of the future. The Gaia hypothesis (Lovelock, 1972), as well as the topic
“Collapse” (Diamond, 2005) typically reveals a geonomic speech although these authors would not
have used that term. As explained by Diamond (2005), the recent global technological civilisation
and its six to eight billion people is a pulse that is essentially due to access and use of fossil fuels
and uranium. When depleted, which could be within half a century or five centuries, and no
matter the progress of technology by then, humanity will have to go back to less than one billion
people and use renewable energies. See http://fr.wikipedia.org/wiki/Géonomie. Accessed Aug.
2013.
 
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