Geology Reference
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sion of exergy replacement costs into monetary costs through conventional energy
prices. According to the results obtained, Australia would have lost the equivalent
of between A$74.3 and A$141.9 billion of its mineral wealth (considering fuels and
non-fuel minerals). This corresponds to between 6.3 and 12% of the nation's GDP
registered in 2007. If, then, 2008 energy prices are considered, the same amount
of physical stock extracted would correspond to between 9.7 and 12% of the 2007
GDP. This difference serves to indicate that monetary costs might not be the most
suitable indicator for an assessment of mineral wealth, given that price volatility and
its arbitrariness distorts the real physical value. Nevertheless, this indicator does
usefully provide an order of magnitude as to the important role mineral extraction
has on the economy.
In the second part of this chapter, an analysis of the exergy degradation of
mineral reserves has been extended from a national level to a planetary one. Due
to lack of information, this had to be undertaken with many assumptions at the
expense of an important loss of accuracy. Yet, the authors have still been able to
provide a crude estimate of loss in mineral wealth on Earth since the beginning
of the 20th century, the degradation velocity, the degree of reserve depletion, the
years remaining until the depletion of commodities and the year where the peak of
production is expected for the principal minerals considered.
According to the calculations presented, the natural exergy bonus loss associated
with the extraction and further dispersion of the 54 non-fuel mineral commodities
analysed is at least 100 Gtoe, consumed at an average exergy degradation velocity
of 0.9 Gtoe/yr (based on activity in the last decade). This means if one were to
replace all of the depleted non-fuel commodities using current technology, one would
require more than half of all current world oil reserves (178 Gtoe).
The exergy degradation of the non-fuel mineral reserves on Earth is clearly
dominated by the extraction of iron, aluminium and to a lesser extent copper. Yet
these three minerals are not the most depleted commodities. Instead they are the
reserves of mercury, silver, gold, tin, arsenic, antimony and lead which suffer the
greatest scarcity. On the other hand, the minerals of cesium, thorium, REE, iodine,
vanadium, PGM, tantalum, aluminium, cobalt and niobium are the least depleted.
That said, this situation may change, especially for minerals such as PGM, REE,
Ta, Nb or Co with the boom of ICTs and renewable energy technologies.
For the majority of the non-fuel minerals extracted on Earth, the authors have
applied the Hubbert bell-shaped curve, assuming a minimum value, corresponding
to the published reserves and a maximum one, corresponding to world resources.
The model applied using reserves data reveals that the theoretical peaks have been
reached for the following mineral commodities: mercury (1960), arsenic (1971), tin
(1979), lead (1989), gold (1994), silver (1995), cadmium (1996), antimony (1998),
zinc (1999), zirconium (2003), manganese and wolfram (2007) and copper (2012).
Considering world resources, the theoretical peak might have been reached for mer-
cury (1965), tin (1986) and gold (2001).
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