The Exergy Replacement Costs of Mineral Wealth - Thanatia: The Destiny of the Earth's Mineral Resources - page 366

Table 12.4 US recycling rates of selected metals in 2008
(USGS, 2010)

Aluminium 48% Iron 61% Tin 34%

Chromium 34% Lead 77% Titanium 41%

Copper 32% Nickel 43% Zinc 30%

For the calculations presented here, US recycling ratios have been extrapolated
globally 5 . This means that from the total mineral bonus extracted, only 72% is
lost theoretically (3.8 Gtoe), if stocks are not taken into account. If the exergy of
the fossil fuels used in the extraction and processing of minerals is added, the total
exergy loss due to mineral production in 2008 is equal to 4.9 Gtoe. It should also be
stated that only 37 minerals have been considered. Hence, the previously reported
value would increase, if all mineral commodities were to be included in the analysis.

12.7 The mineral exergy replacement costs of world mineral
reserves

In the same way that the authors have calculated the exergy replacement costs of
the annual production of minerals, one can apply the methodology to assess the
mineral exergy bonus of the world's mineral resources. As stated in Sec. 11.3.2, the
exergy property alone does not provide a fair value for non-fuel mineral resources.
Nevertheless, the exergy replacement costs indicate, from a human perspective, the
effort to re-establish the natural conditions of a deposit after it has been extracted.
Table 12.5 shows the exergy and exergy replacement costs of the world mineral
reserves and world resources.
As can be seen from Table 12.5, the exergy replacement costs of the studied
minerals are two orders of magnitude greater than their exergy values, which just
goes to highlight how far human technology is from reversibility.
From all minerals analysed, aluminium, potash and iron constitute the greatest
exergy bonus in the crust, with 29.9%, 53.6% and 14.5% respectively of the total
mineral wealth, corresponding to the great number of reserves found (copper for
instance, only represents 0.3% of the total wealth). Even if in mass terms iron
reserves are larger than those of aluminium, the greater concentration of aluminium
deposits with respect to Thanatia, make these latter deposits “more valuable” from
an exergy point of view.
The exergy replacement cost of the known non-fuel world mineral resources are
one order of magnitude greater than the exergy reserves of fossil fuels: over 8,000
Gtoe vs. 898 Gtoe of proved fossil fuel reserves. This demonstrates the better
applicability of the exergy costs for the assessment of the mineral capital on Earth,
with respect to the property exergy alone.

5 In Chap. 14, additional recycling data is shown.