The Exergy of the Earth and its Mineral Resources - Thanatia: The Destiny of the Earth's Mineral Resources - page 348

According to Table 11.20, the available renewable resources on Earth, which
are the sum of solar, tidal and geothermal energy is huge: around 34,884 Gtoe/yr.
Of course this value is only theoretical, since currently and into the near future,
technological limitations mean that it is impossible to recover so much energy.
Potential exergy use is significant too: 97 Gtoe/yr. This means that with a
feasible improvement of renewable energy technology, it could supply nine times
the energy consumption of the entire world (12 Gtoe in 2010). The RW use indica-
tor, shows that with the exception of hydropower, with some 57% of its potential
being exploited, most renewables are still very much untapped: 8.6% of the electric
potential of geothermal 15 , 3% of biomass, 1.3% of wind and 0.2% of tidal. Current
energy use for solar power and ocean waves is negligible in respect to their capac-
ities. Evidently, there is enormous potential in the further use of renewables with
Man's technological limitations (rather than the planet's) the reason why only a
very small proportion can be utilised.
In the case of non-renewable resources, including nuclear energy, fossil fuels
and non-fuel minerals, the minimum quantity of available exergy is approximately
131,000 Gtoe, from which 56% comes from the undeveloped fusion of deuterium
and tritium. The potential exergy use of non-renewable resources is at least 7,600
Gtoe. In fact, with the exception of the different types of nuclear energies and
unconventional fossil fuels, the current state of technology is su ciently developed
to support the extraction of the majority of the available non-renewable resources.
Indeed, the R/P ratios show that there is enough fission energy for more than
8,000 years if one uses fast spectrum reactors in a closed fuel cycle. Coal meanwhile
could last for another 120 years, oil for 52, natural gas for 70 and non-fuel minerals
for 126, on average, if the consumption rates of these commodities remain as they
were in the reference year of 2010. The collective sum of non-renewable energy
resources, should last for at least 664 years.
Non-renewable resources represent a stock of concentrated chemical exergy with
available resources contributing to a very small fraction of the Earth's total chemical
exergy - only around 0.1%. Furthermore, the exergy of conventional fossil fuels and
non-energy mineral resources, constitute only 0.01% of the upper continental crust's
chemical exergy which is in the same order of magnitude as that of the atmosphere
(the layer with the least chemical exergy content). Thus indicating that the use
of chemical exergy of dispersed substances is practically impossible. Therefore, the
Earth's 7 10 6 Gtoe of chemical exergy currently constitutes a useless reservoir of
exergy with Man only able to exploit 0.01% of that amount.
These results, even if rather crude, lead the authors to conclude that the chal-
lenge of “sustainable development” is not a matter of energy scarcity or even material
scarcity. Instead any such issue is related (even if not readily associated with) to
that of concentrated mineral resources (both of fuel and non-fuel origin). Vast
15 The potential thermal use of geothermal energy is not yet quantified, but is presumably much
higher than its potential for electricity generation.