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1
Introduction
The term
mining waste itself is
elastic with threshold values changing with realities
and innovations. Waste handling did not get its due
importance in earlier days with importance to
segregation and separate piling for future reclamation
not getting priority. Dumps from
selective mining, using
only higher end quality could still offer scope for
reclamation and need identification. However, backfilled
material may have been lost forever.
Nobody likes the generation of waste. First, it is
adding to the costs, with additional problems associated
with disposal and of course more the waste less the
recovery. Yet it is inevitable, and arming oneself with
data of the deposit in totality and working according to
the merits of the structure can result in unnecessary
production of
waste. “NO WASTE
MINING” is still a utopian thought since not all the Run
off Mine (ROM) is useable all the time, and the issue of
containing the generated waste calls for serious
attention.
This paper attempts to touch the tip of the
issues and to provide an outline of what the issues
currently at stake are. The paper attempts to bring out
importance attached to the legacy of the mining waste
and its generation. It further looks at beneficiation as
well as constraints in containment of
toxic wastes and
recycling. The paper also looks at the larger issues
arising out stoppage, closure and abandonment of mines
and the need to form a strategy to tackle the legacy of
waste left by earlier mining for the urgent need to form
special task forces to address the issue of clean up.
The author has been
tracking mining issues over the past few years; the
primary source of information being the World Wide Web.
Hyper-links to the sources are provided in the
Appendix. While care
has been taken to derive material from creditable web
sources, the author can-not vouch for the exactness of
the data and welcomes the reporting of any
discrepancies/ deviations from the readers.
2 Mining Waste
Generation
Mining waste generation
has been going on all the time and when the impact is
directly on the community and the effects visible, the
issue becomes contentious. The awareness on
environmental and after effects of mining is very high
than ever before and this can be seen in the resistance
to mining projects around the globe and calls for
re-viewing past mining activities and cumulative
effects.
States find handling the inheritance difficult to manage
when adequate finance and technology is not available
and when the mining agency had left the place long back
after discontinuance or abandonment. The legacy
threatens the future generations and funding these clean
up projects is beyond many agencies.
“Superfund
sites”
attempt to ad-dress this problem to a certain extent in
the USA while the issue is assuming bigger proportions
in the rest of the world.
The waste generating activities from mines are from:
s Current mines continuing waste generation
s Recycling and reclamation of dumps already in
existence
s Sites of abandoned mines and closed mines
2.1.1 Generation
The waste generation resulting out of beneficiation is
limited to point of source when the priority was export
and processing at a different location. The current
tendency and policy, processing and value addition
insistence at point of production or at least locally
and it has be-come necessary to consider the hitherto
unknown factor of waste generation out of processing.
The amount of run-off-mine and processing required is
nearly one ton of raw ore for a 3 grams platinum ring
and China alone consumes 560000 ounces per annum.
Large-scale mining
also
generates proportionately larger volumes of waste. The
waste generation could be still higher than the
proportion-ate consideration when large volumes of
overburden and “contacts” considered below threshold
value mined.
The awareness that the large-scale mining not only
increases the waste but actually reduces job
opportunities is causing concern among local community
and the opposition to mining is visible.
With technology aiding the exploration like never
before, estimation of mineral inventory is getting more
and more precise. There is a need for regular updates of
the mineral inventory in line with the data generated by
various exploration activities.
Since the awareness and knowledge of waste management is
gradually evolving and unfortunately, the time lag has
left legacies to deal with, new ventures should get the
focus right at the initiating stage itself.
2.2 Need
to focus on the mining waste
Before planning any project or venture, the entire life
cycle of the mine need to critical analysis particularly
with reference to the waste generation at
a. in-situ,
b. during
beneficiation and
c. Post industrial.
Since the waste needs handling at the point of
generation, transport, processing as well as storage or
disposal, and the impact is slowly emerging into
reality, any new venture can consider the following:
To plan for segregation of waste generated and form
separate dumps with a view of possible reclamation in
future
Team of experts deal the hazardous and
toxic waste at point of
generation, processing and recycling, transportation,
piling and containment
Maintaining the environmental balance
The project should also include the cost of treating,
handing containing the generated mining wastes and not
leave another legacy to the national exchequer.
Today, cyanide leaching is the method of choice for the
recovery of most of the world’s gold production. Cyanide
leaching will provide a more technologically effective
and cost efficient method. Where amalgamation plants
could recover about 60% of the gold present, cyanide
could recover about *90%. Because of the improved
recovery, cyanide leaching is resorted to many old
piles. (*source from the net Reference to sites provided
in the annexure 1)
2.2.1
Acid mine drainage
The most preferred control of acid mine drainage is
prevention at source and since this develops over a
time, eliminating chances of development preferably at
source. Mine waste management calls for critical
attention in this aspect wherever necessary.
Of this total volume, approximately *85 percent
attributed to copper, iron ore, uranium, and phosphate
mining and related activities. Approximately one-half of
the waste generated is mining waste and one-third is
tailings, with the balance consisting of dump/heap
leaching wastes and mine water. (*source from the net
Reference to sites pro-vided in the annexure 1)
2.2.2 Toxic mining waste
Toxic mining waste is causing concern around the globe
and instances of dam failure,
polluted rivers, water
bodies, leakages below surface occur in spite of all
precautions and pollution can even be caused by heavy
rainfall or flooding or earth tremors. Links to a few
examples are in the Annexure 2.
Heap leaching involves piling the crushed material on an
impervious base and allowing the cyanide solution to
percolate the heap, leaching out the gold. Several
parameters that could go wrong like rainfall, flash
floods, earthquakes or unstable base, clayey substance
preventing effective percolation and most importantly,
where the heap is formed proximity to water bodies and
necessary to treat the process water.
The prolonged time for the leaching process to complete
the process also is a concern. Since “heap
leaching” is able to process low-yielding ore
and ore that could have gone into the waste itself is
finding a solution, is preferred. Economical
considerations and environmental considerations do not
match all the time and there is increasing resistance
for cyanide leaching with some states bringing
legislation banning the process.
A rough estimate mentions that one third of all wastes
is generated out of leaching wastes and water, and the
balance shared by mining wastes and tailings.
2.3
Recycling
Recycling gets a favorable look since it handles some of
the issues arising out proportionate waste in processing
cycle. When recycling comes into focus major, segments
occupying priority are PGM, copper, gold, silver, and
uranium. Of these PGM and gold are in the news these
days since the emergence of catalytic converters for
automobiles and mobile phones in everyday life corners
prime place. PGM recycling from the catalytic converters
is now established and electronic waste recycling
yielding gold has begun to emerge. The article outlines
a few segments currently getting the focus.
2.3.1 PGM
Recycling results in the direct reduction of waste
generation and to the conservation to some extent.
However, this is constantly evolving.
Recycling for PGM from the
catalytic converters
in
the automotive industry is already a major factor. This
sector is likely to grow, as the life cycle of
automobiles is getting shorter and shorter with
increasing buying capacity and frequent changing models.
Palladium is increasingly replacing platinum in the
jewelry sector as well because of the cost advantage
2.3.2 Gold in electronics
The growth in the electronic industry and constant up
gradation of the personal computers and mobile phones is
already drawing enough attention in the recycling and
recovery of gold. How far this will pool back will
reflect is to be seen over the coming years.
2.3.3 Coal
Coal washing has always been a point of focus and recent
success in reducing the water content in the coal sludge
and re use of sediments is most encouraging.
2.3.4 Caution from Coal bed methane
Coal bed methane is getting its attention as the energy
source with more players coming in to tap the source.
This energy resource depends upon the formation and
accumulated extractable quantity. The thickness,
inter-bedding and permeability control the source for
tapping.
While much focus in this new energy source, the amount
of water required as well as the disposal of the process
water and effects on land has not reached the public
attention to the desired level. These aspects need a
very careful study.
2.4
MINE CLOSURES
Mine closures need attention since when a mine is closed
or abandoned, a legacy is left and the state is left
with the task of clean up.
Mine closures can be permanent or temporary. Set
procedures are al-ready in place for the closure to take
place and in South Africa, separate institutional
authority is in place to address this issue.
Stoppage of mining, abandonment or closure can be due to
various reasons like:
Operational restrictions
Constraints beyond the operators control like political,
economical or environmental.
Alternate operations becoming more attractive
Project becoming economically unsustainable
Situations arising out of labor strife and lockouts
Accidents and related issues attended for ensuring
safety for work
2.4.1 Key factors
Some of the key factors in dealing with the mining waste
are:
Waste management of by-products
Cost of smelting for recycling
Pollution and environmental issues associated with
disposal
Discharge into water bodies
How far the contamination penetrate below surface
Control on emissions on a broader perspective.
2.5 Some points for the future
In the light of the contentions, issues and opposition
in various parts of the globe for large-scale mining
future mining projects need to focus on the totality of
working the deposit as well as keep the eco-balance for
the future. Some important points for consideration are:
Administrating mining and mineral regime confirming to
the emerging ground realities
Initiating survey and estimation of determining residual
resources and also nature and quantities of waste
already generated.
Substituting hazardous substances wherever possible and
thrust on research on waste management.
Present laws provide for these important considerations
but in the light of the experience of the legacy now
left to handle, it appears advantageous to have educated
and trained specialized task forces to handle hazardous
wastes.
2.5.1 Some immediate actions under implementation and
research
The following is a general list of segments that are
being addressed and with a thrust on research:
Possibilities of using partially spent cyanide
solutions
Separation technology in Floatation
Alternatives to toxic and hazardous substances in
processing
Giving due importance for waste generation, treatment
and containment.
Research towards changes to chemical composition of
tailings
Bio leaching
Building up inventory of national mining waste
Building data base of inactive and abandoned mines
2.6
Conclusion
The ideal would be for “NO WASTE MINING” but this is
controlled by the geological structure and how far the
run of mine is saleable or otherwise disposable. However
with the aim to reduce the waste generation by looking
into possibilities like recycling, in-depth study on the
properties of the waste (at present available knowledge)
generated and taking steps for future reclamation would
go a long way towards responsible mining. Involving
local community is almost becoming in-evitable and when
there is awareness and involvement in the mining
activities from all quarters, there would be serious
reflections on the activities and steps to follow.
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