MINE WASTE
Pros and cons Adopting a dr y tailings approach mitigates the risk of catastrophic dam failure, especially in seismic areas. In addition, Rose notes that one of the biggest benefits is the opportunity for water reuse. Some mines are able to achieve water recover y upwards of 90% – water that would typically have been evaporated on a tailings dam. This is especially useful in water-scarce areas. Another benefit is a smaller footprint. Typically, around 95% of what is mined goes to a tailings storage facility, meaning tailings dams require vast amounts of space. Facilities that adopt dr y tailings procedures are also easier to close and rehabilitate because they are smaller, and the tailings are easier to reconstitute. On the downside, the dr y tailings process is more expensive due to higher capital and operating costs. However, Rose stresses that it is always dependent on the context. For example, in instances where tailings need to be pumped over a long distance, dr y tailings may be more cost-effective. Some sites may also require additional infrastructure, such as
stormwater drainage, to keep the tailings storage facilities dr y. In ver y wet environments, it could create a management problem around haulage and compaction. Dust generation can also make it unattractive for mines with surrounding areas of high habitation. “At the moment, it is economical for smaller mines – operations of 20 000 to 30 000 tonnes per day. That is fundamentally because of the size of the filtration plant. However, we are seeing new technology with higher efficiency being brought into the market ever y day, which increases the attractiveness of the dr y tailings solution,” says Rose. “When it comes to the pros and cons, one size doesn’t fit all – it is purely context dependent.”
Current adoption Globally, 5% to 8% of mines use a dr y stacking process. This is expected to increase as water scarcity becomes a greater concern. It is often adopted in colder climates, such as Canada and Alaska, but closer to home, Eskom presents a good example. “It is a good option for most mines. It may not be the
most capital-efficient way of doing it, but it certainly reduces your water footprint, which is absolutely a good thing. We’ve even seen Anglo American publicly state that its long-term goal is to move towards dr y tailings worldwide, with an eventual goal of reusing over 80% of the water from operations – that’s huge,” says Rose. Encouragingly, he notes that feasibility studies are now exploring options such as dr y tailings rather than only the traditional process flow. This is largely enabled through tools such as global benchmarks and equipment prices reaching parity. Rose concludes: “In almost ever y case, we now conduct trade-off studies to determine the most economically viable option, the best technical option, and the solution that best meets the sustainability needs of the mine and surrounding communities. This provides the opportunity to select the best-fit option for the mine, in its specific operating environment, while staying true to the principles of good environmental practice, longevity and value creation.”
Specialist Waste Management Consultants • • • • • •
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Telephone:+27 (0)21 982 6570 Fax:+27 (0)21 981 0868
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www.jpce.co.za AUGUST 2020
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