Why most tailings repurposing projects start in the wrong place

Every tonne of ore produces more than the commodity a mine attempts to extract. It also produces tailings, the finely ground material left behind after processing, most of which ends up in long-term storage facilities. But tailings are not uniform waste. Together with waste rock, they often contain minerals and aggregates that may have value beyond the mine site.

A typical metallic fraction might account for only 10 to 20 percent of the material but the larger non-metallic fraction — dominated by silicates, with carbonates or phosphates present in some deposits — can be just as important if they can support markets for aggregates, bricks, tiles or precast concrete.

Mines are always under pressure to reduce what ends up in long-term storage, while other industries are looking for mineral feedstocks, and this is where tailings can become a commodity. This changes tailings from being a storage and processing problem to being a market resource.

A tailings storage facility can look uniform from the surface but prove different once you start investigating it. Material deposited decades apart may have nothing in common, or a sample taken from one location may reveal little, if anything, about the mineral composition that sits elsewhere. This is a problem when the goal is a repeatable product because customers buy to a specification, not a one-off test result.

Before choosing a product, operators need to identify the material in the mining facility. X-ray techniques like fluorescence and diffraction, as well as mineral electron scanning, can reveal which minerals are present and whether they can realistically be separated. Older facilities that maintain poor records may find it difficult to pinpoint where different materials have ended up, but a 3D model can help fill those gaps and show operators how to mine and what materials to blend, recover or repurpose.

After identifying the materials in the plant, operators can then separate material using various means, such as gravity or magnetic flotation, depending on what the testing has found, to isolate the useful fraction.

Though useful doesn’t always mean usable. This process is only successful if the customer finds the output satisfactory. Otherwise, the project only creates another material to store – arguably with less potential use than it had before.

A tailings stream only becomes a product when someone is willing to use it. That sounds obvious, but many repurposing projects spend months testing material before speaking to the people who might buy it.

Quarry operators and other manufacturers already work with mineral feedstocks every day. They know which materials can be turned into products and which are likely to become another stockpile. Bringing them in early can save months of testing on an idea that was never commercially viable in the first place.

Concrete manufacturers, for example, can’t use just any finely ground material. They require particles that behave in predictable ways and meet strict specifications. They might prefer angular particles rather than the rounded grains found in some natural sands because they help create a stronger, more stable product. Crushed mine material can sometimes meet that requirement; sometimes it can’t. The point is whether the material performs the way the customer needs it to perform.

Satisfying a specification is only part of the job. Someone still needs to process or distribute the final product. For example, a mine owner might process and manufacture the product itself, or it could partner with a quarry operator. Alternatively, some mines might simply supply material under an offtake agreement. Whatever the arrangement, the outcome should prioritise the material landing in the hands of the people best placed to turn it into a product.

Still, a technically viable product can fail for surprisingly practical reasons. Perhaps the volume is inconsistent, or the supply chain is too complex. Some certification costs in certain jurisdictions may outweigh the commercial benefit. Any one of those issues can turn a promising material into a product nobody wants, which is why potential buyers need to be part of the assessment instead of the handover.

The entire process of repurposing tailings shouldn’t end when the facility or the operator finds a buyer. Instead, the real test is whether the project reduces the amount of material or long-term obligation left in the facility.

That might mean reducing the volume of material that requires long-term storage or changing the closure challenge altogether by reducing the amount of material that needs to be monitored and managed over time. In many cases, this might also mean recovering water that would otherwise remain tied up in the facility.

Since removing material from a tailings facility is not the same as removing material from a stockpile, every tonne removed from tailings storage changes the facility around it. Excavation can affect embankment stability, altering how water moves through the system. The remaining material may behave differently once part of the deposit has been removed. If the project instead made the facility harder to manage, then the project itself has failed.

Finding a use for tailings is good. Leaving less tailings behind is better. But the strongest projects achieve both.

• Tailings can only become a resource when there is a market for the outcome. Processing capability alone does not create value if the material can’t be used.
• Technical feasibility and commercial viability need to be tested together. Successful laboratory results and a recoverable resource may not mean much if buyers can’t use the product or the economics don’t stack up.
• The biggest opportunity may sit outside the metallic fraction. Silicates, carbonates and other non-metallic materials can represent the majority of the resource and support applications ranging from aggregates to construction products.
• Consistency matters as much as quality. If material cannot be recovered and supplied to specification across the facility, there is no reliable product to take to market.
• The ultimate measure of success is whether repurposing reduces the long-term liability. A product that leaves the facility harder to manage or simply creates another material to store has not solved the problem.

Want to explore whether your tailings could support a viable market? Contact our tailings and resource recovery specialists to assess the technical, commercial and closure implications of repurposing opportunities.