Thermodynamics of Mineral Resources - Thanatia: The Destiny of the Earth's Mineral Resources - page 287

100%

Cu, $

90%

80%

Cu, B*

70%

60%

50%

40%

Au, B*

30%

20%

Au, $

10%

Ag, $
Ag, B*

0%

1900 1920 1940 1960 1980 2000 2020

Gold $ Copper $ Silver $ Gold B* Copper B* Silver B*

Fig. 9.6 Cost allocation of a mean porphrCuAu deposit as a function of price and exergy
replacement costs

and the external process of price formation. The former is dictated solely by Physics
and is bound by the process. In contrast, the latter occurs in the marketplace and
is not necessarily tied to the actual process.

9.7.4 Thermoeconomics and LCA

Considering the above, it follows that Thermoeconomics needs detailed Material
Flow Analyses, MFA, i.e. the tracking of material, of energy flows and stocks, so
as to calculate and subsequently add up their total exergy. In this way, exergy
and exergy cost analyses can take advantage of the Life Cycle Assessment (LCA)
databases, computer programmes and data management. Analysing life cycles is
key when it comes to identifying where and finding out why materials, water and
energy are lost. Adding exergy to an LCA allows for a better understanding of
actual expenditures and a more precise physical cost allocation. In very aggre-
gated studies, exergy cost is equal to embodied exergy or embodied energy analyses
and theoretically, conventional LCAs would su ce. However, exergy analyses do
differ from conventional ones, particularly in mixtures in which energy does not pro-
vide clear clues with regards to allocation problems. This is because typical LCA
databases consider regional averages of environmental impacts associated with mi-
neral processing, which might not distinguish among those operations using hydro,
gas, coal or nuclear generated electricity, or those occurring in different countries,
or even any variations from process to process. Indeed, even if they commonly dis-
criminate between heat and electricity sources, no clear distinction is made for each
and every chemical raw material used either. Thus conventional life cycle studies
are far from precise.