Geology Reference
In-Depth Information
reaching heights of 100 meters”. This rubble may be overburden or consist of sterile
waste rock, low grade ores or solid leached residues. Some of which (substances
such as asbestos, arsenic, crystalline silica, lead mercury, heavy metals and/or ra-
dioactive materials) may be dangerous to human health and could under certain
conditions migrate out of the assigned site and find their way into ecosystems, where
a whole host of organisms are then exposed to their detrimental and even deadly
effect 9 .
Gold mining is a typical example of where huge, even excessive, amounts of
rock and toxic substances are released into the environment in order to obtain ever
decreasing amounts of metal “scraps”. Indeed one gold ring may have an environ-
mental “rucksack” containing between 20 and 70 tonnes of waste rock. Moreover
the environmental impact is likely to increase gradually into the future - in terms
of energy, water, chemicals and GHG emission costs. According to Mudd (2007b),
the average environmental costs of gold production per kg of Au extracted are 143
GJ, 691,000 litres of water, 11.5 tonnes CO 2 -eq and 141 kg of cyanide, in addition
to lead, arsenic and mercury emissions. Mudd (2010b) also states that “Given the
growing scale of modern mine waste, even if only 1% of wastes continued to cause
pollution (i.e. rehabilitation is 99% perfect), this amounts to tens to hundreds of
millions of tonnes leaving a lasting environmental legacy”.
7.6.1.3 Energy consumption
According to the Worldwatch Institute, mining consumes 4-7% of all energy used
worldwide (Miranda et al., 2005). TheInternational Energy Agency estimates it to
be at 7-10%. Almost 40% of this energy consumption is used in milling operations
(DOE, 2007), although the exact figure varies greatly with the grinding material
and the amount of rock to be ground (the energy used in milling is inversely pro-
portional to the particle size). Transportation and material handling in open pits
meanwhile consume on average 17% of total energy in the form of diesel oil, whilst
any operations such as ventilation and dewatering in underground mining consume
significant amounts of energy too (DOE, 2007). As explained previously, the energy
consumed in mining relates heavily to the ore grade with declining ones demanding
additional resource consumption 10 . Therefore, energy availability is a key factor in
mining. Minerals and energy are very closely related, since there are no minerals
without energy but equally no energy without minerals.
This important issue is described in detail in Chap. 8, where the energy consump-
tion associated with the mining and metallurgy of selected minerals is analysed.
9 As such, special disposal sites with liners are absolutely necessary so to avoid the contamination
of groundwaters and the surrounding landscape.
10 Moreover, the energy consumption rises even more with increases in water use, wastewater
treatment, GHG emissions and stricter environmental regulations.
 
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