REPROCESSING AND TAILINGS REDUCTION
Profits from the past
While tailings dam liabilities and falling water resources are
affecting the ability of miners to start new mines, or expand
existing ones, these issues are strengthening the case for
reprocessing and retreating ‘waste’ sites or streams. Dan
Gleeson explores an increasingly diverse market focused on
revenue generation and risk reduction
ith improved transparency around
tailings dams and waste stockpiles now
part and parcel of being a responsible
mining company, investors and the wider mining
world are becoming aware of the opportunities to
clean up legacy operations, while, at the same
time, generate extra revenue.
These opportunities are growing in value and
quantity as water scarcity in many major mining
hubs accelerates and the ability to expand
existing tailings impoundment areas diminishes.
The trend is further aided by the fact costs and
liabilities associated with these facilities continue
to increase.
At the same time as this, these opportunities
are becoming more feasible as the cost of
specialised equipment drops – making the upfront
capital expense more manageable – and the number
of large mining companies looking at removing
these ‘liabilities’ from their portfolios expands.
This has seen a new generation of ‘miners’
spring up intent on profiting from processing
material previously categorised as ‘waste’.
New Century Resources, for instance, emerged
in 2016 to restart the Century mine in
Queensland, Australia, through an initial tailings
reprocessing operation after the much larger
MMG had decided the asset had reached the end
of its profitable life earlier that year. The
Australia-based base metal producer is now
aiming to become one of the world’s top 10 zinc
producers through a ramp up of operations at
Century to 12 Mt/y.
GoGold Resources, in Mexico, is using the
proceeds from heap leaching the Parral tailings
operation, in Chihuahua, to progress with its
exploration projects in the country. The recent
addition of a sulphidisation, acidification,
W
10 International Mining | MAY 2020
recycling and thickening, or SART, plant from BQE
Water will only bolster cash reserves through the
recovery of a high-grade saleable copper sulphide
product, the re-generation of cyanide (a major
operating cost at Parral) and an improvement in
the leaching efficiency of the heap.
In Africa, the likes of Goldplat and Jubilee
Metals Group have been profitably processing
gold and platinum group and base metals from
waste streams for many years.
Central Asia Metals built its name on the
Kounrad asset, a copper dump leach operation in
Kazakhstan, which, through reprocessing and SX-
EW, has produced more than 100,000 t of copper
cathode since operations began in April 2012.
The list goes on.
Removing the ant heaps
“Reprocessing is one strategy, if it’s worthwhile
from an economic standpoint,” Theo Gerritsen,
Stantec’s Global Tailings Practice Lead, said in
response to a question about what strategies
miners were evaluating for legacy tailings
dams/waste stockpiles within their portfolios.
Speaking from his home office in Brisbane,
Australia, in April, he reflected on his time
working in South Africa to provide some
evidence: “For example, at one point, in the
middle of Johannesburg, there were these giant
‘ant heaps’, old tailings which were processed
100 years ago by gold mining companies.
“These ‘ant heaps’ had more gold in them than
most current day gold mines. Because the
technology at the time was not very sophisticated,
they could not recover as much as they can now.
Most of those historic tailings have now been
reprocessed.”
This reprocessing opportunity is one of the
In Colombia, AuVert's technology is being
combined with CDE's experience in dewatering
and tailings management to extract the
remaining precious metals existing in the
ground, while removing up to 93% of residual
mercury which has to date prevented this land
from being used by the local population
reasons why mining companies may be cautious
about using tailings as backfill material or
relocating current day ‘waste’ to an inaccessible
area of the mine, according to Gerritsen.
“As technology improves, the opportunity to
recover more of the metals/minerals increases,”
he said. “There are elements where that may not
be the case – coal ash, for example, cannot be
reprocessed but can be used to produce cement.
There are certainly opportunities with gold,
copper and even coal, for instance.”
The strategies companies ultimately pursue for
these ‘waste streams’ depend on the technology
available and the safety of the facilities, Gerritsen
remarked.
“For instance, it may not be economically
viable to reprocess the material currently in a
tailings storage facility and, therefore, the owner
may decide to close it or put it into a non-active
state,” he said.
One company looking to address the
availability and cost of specialised technology for
reprocessing tailings and other ‘waste’ is CDE.
An industry-leading manufacturer of wet
processing equipment for materials processors,
CDE has seen a significant rise in proposal
requests for dewatering and dry stacking
equipment over the previous 12 months,
according to Kate McCormick, Mining Sector
Executive at CDE Meta.
Most requests have focused on re-processing
existing tailings, recovering the valuable
fractions, and dewatering and dry stacking the
waste products, she explained.
“We are increasingly approached by clients
seeking to recover value from their waste
stockpiles, which have accumulated in times
where high-grade ore was abundant and lower
grades were set aside as waste, or processing
technologies were not sophisticated enough to
capture fines fractions or suitably upgrade the
ore deposit,” she told IM.
McCormick said CDE was receiving these
requests from smaller mining companies looking
to specialise in reprocessing brownfield sites.
“Increasingly we are seeing junior miners
adopting a strategy of purchasing waste dumps
or historic tails for re-processing as an economic
source of commodities,” she said. “This value is
easy to recover as the material has already been
mined and avoids the substantial extraction costs
of virgin mining, yet these tailings deposits
contain high recovery rates with existing projects,
for example, recovering 2 g/t Au and achieving
63% Fe grade at 50% yield.”