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MINING WASTE-AN ISSUE GREATER THAN MINING ITSELF
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.
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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.
ANNEXURE 1
The following is a list of sites that are relevant to the topic of this
article and throw more light.
Recycling, technology and environment
Cyanide leaching Methods
Use of cyanide for gold recovery
Uranium recycling
all about uranium
Major environmental Laws
Action by community in clean up
Uranium processing flow chart
Copper waste
FAQ on cyanide
Mercury emission: Process concerns
Recovery ratios
Cyanide spill Ghana-River
Ankobra
Toxic River
Buyat bay, Indonesia
Problem of mercury
Ore processing waste-Basic
process of gold recovery
Awareness to pollution and environmental
degradation
Environmental clean up costs
Montana – Two sides to an issue
A firm NO to cyanide from Montana
Gypsum recycling
Coal bed methane
Recycling e-waste and mining
Waste reduction
Bio-remediation
Clean coal technology
ANNEXURE 2
Mine closures are always a painful affair and present day mining closure
has set policies laid for the smoother transition of all concerned. The
following links point to some of the issue that forced the mines to
either stop working, close temporarily or abandon the entire workings:
Examples:
Mines Closures, stoppage and abandonment
Restrictions on operations and working
parameters
Maple Creek (closeness to surface and
impact on water)
Relocation on economic grounds:
Giant Mine
Worsening financial situation:
East Rand Property
Also:
Strikes and labor situations:
Poland
Romania
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