When is tailings repurposing commercially viable?

The first step is profiling the tailing’s composition and make-up. Chemistry is part of it, but you also need to define the mineralogy, particle size and how the material varies throughout the facility. Tailings deposited in one part of a facility may differ from material deposited elsewhere. Older sections may also reflect different ore sources or processing conditions.

Once that work is complete, a number of dominant material streams usually begin to emerge. There may be a metallic fraction that still contains recoverable value, but other non-metallic fractions, often made up of silicates, aluminosilicates or carbonates, could be suitable for other industrial applications. Where waste rock is available and suitable, it should also be considered, as its coarser fractions can complement finer tailings materials and expand the range of potential repurposing opportunities.

The focus then turns to how those streams can be separated and recovered. This enables the operator to assess each stream as potential feedstock rather than waste.

A material may contain value, but there still needs to be a market for the products that materialise. That is one of the key questions a business case needs to answer.

Potential end users will ultimately determine whether you have commercially viable products, which is why early market engagement is so important. Once you know your main material streams and key characteristics, you can start discussing opportunities and define the specifications that any product would need to meet in order to be useful.

A concrete manufacturer or a ceramics producer, for example, is not looking at the tailings itself but whether the materials derived from it can meet their feedstock requirements. That might include particle size, mineralogy, chemistry, moisture content, consistency or volume.

The material may already have significant advantages, having been mined and processed. However, the market opportunity will also depend on location, logistics and scale. Bulk, low-value products generally need to be consumed locally, whereas larger inventories may justify higher-value manufacturing pathways that can support transport to more distant markets.

Quarry operators and manufacturers can become valuable partners early on. They have a sharper and more intimate view of what their industry needs and can quickly identify whether a material has promising use.

Before industry can use a non-metallic fraction, the mine owner must demonstrate that it meets environmental standards. This usually means confirming the material is suitable for its intended use and does not present an unacceptable risk to human health or the environment. Depending on the jurisdiction and application, this may involve trace-element analysis, leachability testing and environmental classification.

At this stage, it’s worthwhile bringing regulators into the discussion as they can help clarify what evidence is necessary and how the material will be assessed. In our experience, that conversation is more productive when it runs alongside the technical assessment rather than after it. Ignoring approval requirements until later can quickly derail an otherwise promising project.

One of the mistakes we often see is judging the economics of a tailings project through product revenue alone. Recovering metals has value; and so does selling a non-metallic fraction as feedstock. But they’re not the only things that contribute to the business case.

Repurposing can reduce the amount of material reporting to a tailings storage facility. That can change the way a mining company thinks about future storage requirements and, ultimately, closure. Those benefits are not always easy to quantify, but they still contribute to the project’s outcome.

There are other considerations as well, such as a jurisdiction’s royalty rules. The way regulators classify the recovered material often determines how those rules apply. For example, regulators may treat a metallic concentrate differently from a non-metallic material that a manufacturer later turns into a construction product.

The strongest business cases tend to look at the whole picture. Revenue matters, but the value often extends beyond product sales to reduced storage requirements and lower closure liabilities.

An initial screening study answers several practical questions:

• Is there a resource worth developing?
• Can you separate it into product streams?
• Is there a market for those products?
• Is there a realistic pathway to approval?
• What are the benefits of reducing reliance on TSFs and WRDs?
• Does the overall value justify further investment?

For an operating mine with representative samples and good existing data, a screening study can often provide those answers early in the assessment process. By the end of the study, you should know whether the project deserves more investment.

Apart from leaving you with a more comprehensive view of the resource and how to process it, any study should also tell you whether industry is interested in the resulting products as well as their approval and regulatory procedures.

Some opportunities move into proof-of-concept testing and further development. Others stop because a key constraint has been identified early. Both outcomes are useful, but the study should help you decide whether a project warrants proof-of-concept testing or whether you should focus your efforts elsewhere.