Tailings repurposing and reuse: From risk management to value creation

Tailings reprocessing is generally associated with recovery of residual metals and therefore often fits more readily within established mining and mineral processing regulatory frameworks. Repurposing is potentially more complex because material leaves the traditional mining cycle and becomes a mineral feedstock for another industry and is more akin to an industrial process.

Recovering products or undertaking activities outside those contemplated by the original mine approval may therefore require modification of existing approvals or additional approvals.

The recommended approach is early engagement with the relevant environmental, mining/resources and planning authorities to establish the pathway from mine waste to an approved resource or product. There can be significant benefits for government: reduced mine-waste inventories and long-term liabilities, recovery of already mined and processed mineral resources, new industrial opportunities and potentially post-closure economic activity for mining communities.

From our experience, early collaboration with regulators is much more effective than developing the technical solution first and seeking approval afterwards.

A critical technical step is separating potentially contaminating metallic/sulphide fractions from the generally larger non-metallic fraction. The resulting streams then need to demonstrate compliance with the applicable environmental criteria and the specifications for their intended use.

Absolutely. It can potentially be considered throughout the mine life cycle, including within closure planning.

The greatest opportunity may actually be during mine planning, when waste-rock and tailings management can be designed around future recovery and reuse rather than only disposal. This could reduce future reliance on TSFs and WRDs and potentially reduce long-term closure liabilities.

The starting point is representative characterisation of chemistry, mineralogy, PSD, mineral associations and liberation, together with understanding spatial variability or orebody and process variability for a future mine.

Repurposing can then be incorporated into the mine plan and closure strategy as technically, environmentally and commercially viable pathways are demonstrated.

Yes. Worker, community safety and environmental exposure is paramount, non-negotiable and needs to be considered from the initial characterisation stage throughout the process to final closure.

Potential concerns can include fibrous/asbestiform minerals, arsenic, chromium - including Cr(VI) where relevant - lead, cadmium, mercury and other metals/metalloids, as well as sulphides, soluble salts and other site-specific contaminants.

This is why chemistry alone is insufficient. Mineralogy, mineral associations, liberation and leachability are also important. A contaminant may be structurally bound within a stable mineral or occur in a readily soluble/reactive form, resulting in very different risks.

Separating a sulphide/metal-rich fraction can substantially reduce contaminant concentrations in the larger non-metallic stream where those contaminants are associated with the separated minerals. Each resulting stream should then be independently characterised and assessed for its intended pathway.

Very good question. Transport can absolutely determine feasibility, particularly for low-value bulk materials. However, the comparison should not always be between transporting raw tailings and transporting local virgin aggregate.

For a sufficiently large and suitable mineral inventory, another model is to bring manufacturing closer to the resource. Tailings have already undergone mining, crushing and grinding, potentially avoiding significant upstream processing compared with manufactured sand or other processed mineral feedstocks.

Higher-value manufactured products - precast elements, for example - already travel substantial distances to markets. The business case therefore needs to compare the delivered cost of the finished product, including additional beneficiation, manufacturing and logistics, against conventional production.

Large inventories, clusters of nearby mines, existing transport corridors and regional-development opportunities can improve the case for remote sites. Smaller isolated inventories are more likely to favour local applications such as engineered fill, mine backfill or rehabilitation.

Remote does not automatically mean uneconomic - but logistics must be explicitly included in the business case.

Yes. Slimes should not automatically be considered waste. They can contain valuable metals and potentially useful ultrafine mineral fractions.

The first step is detailed chemical, mineralogical and quantitative characterisation. Very fine material can be challenging to characterise, particularly where poorly crystalline or amorphous phases are present, so complementary analytical methods may be required rather than relying on XRD alone.

Depending on mineralogy, ultrafines can be candidates for hydrometallurgy or bioleaching for metal recovery, while the cleaned residual fraction may have applications in ceramics, binders/cementitious systems, fillers, technosols, engineered soils or blended construction materials.

Bioleaching is particularly interesting for some low-grade sulphidic wastes, although kinetics, mineralogy, acid consumption and downstream solution treatment determine feasibility. The European NEMO project (Near-zero-waste recycling of low-grade sulphidic mining waste for critical-metal, mineral and construction raw-material production in a circular economy), for example, investigated bioleaching alongside recovery of metals and use of residual mineral fractions in cement and construction materials.

The important point is: desliming does not mean discarding the slimes- it can create another specialised feed stream.

A particularly relevant example is Vale's iron-ore operations in Brazil. Sustainable Sand production began at Brucutu in 2021, initially at approximately 250,000 t, and Vale reports that by the end of 2025 more than 3 million tonnes had been produced and distributed. The material is processed to achieve controlled chemistry and particle-size characteristics for construction applications. Vale also operates a block plant at its Pico mine, which produced more than 407,000 interlocking paving blocks in 2025.

Another particularly interesting industrial example is the Kasese Cobalt Company (KCCL) in Uganda. A cobalt-rich pyrite stockpile remaining from the former Kilembe copper operation was reprocessed using bioleaching to recover cobalt. The project demonstrated at industrial scale how a problematic sulphide-rich mine-waste stockpile could become a metal resource while also addressing an environmental liability.

Other important examples include the European NEMO project, which investigated near-zero-waste processing of sulphidic mine wastes to recover metals while producing construction raw materials, and initiatives such as the BHP Tailings Challenge.

There are also many established examples of mine waste being reused internally on the mines for backfill, roads, rehabilitation and construction.

The next development is likely to be greater integration of metal recovery + environmental improvement + multiple non-metallic products rather than single-product reuse.

Yes, although the emphasis in the Canadian oil sands has historically been on tailings management and reclamation rather than production of external construction products.

Coarse sand fractions are extensively managed in sand-placement and reclamation systems, while fine tailings present a much greater dewatering and reclamation challenge. Suncor/Syncrude continue to develop technologies for treatment and reclamation of these materials.

There may be opportunities for selected mineral fractions in construction, ceramics, engineered soils or other products, but these would require detailed characterisation, environmental assessment and product testing.

Given the enormous inventories involved, it is an interesting area for further resource-recovery investigation.

I agree - both additional processing and transport must be included in the business case and carbon assessment.

For conventional ready-mixed concrete, proximity to the concrete plant and construction site is particularly important because the fresh concrete itself has a limited delivery window.

Precast manufacturing creates a different equation. Finished precast products can travel much greater distances, so for a large remote mineral inventory it may be possible to locate manufacturing closer to the feedstock and transport the higher-value finished product.

Tailings will rarely emerge from a concentrator at exactly the specification required by a manufacturer. Classification, separation, blending, washing and potentially additional crushing using waste rock or other coarser material may still be required.

The potential advantage is that much of the mining, crushing and grinding energy has already been expended. Whether that advantage outweighs additional processing and logistics must be demonstrated through a site-specific techno-economic and life-cycle assessment.

Vale's Sustainable Sand provides a useful operating example: its Viga operation uses existing rail infrastructure to move the manufactured sand to customers in other regions.

Note: In many regions, suitable concrete sand is becoming increasingly difficult to access, and the construction industry is already responding through greater use of manufactured sand. Manufactured sand requires extraction, crushing, shaping and classification, whereas tailings have already undergone mining, crushing and grinding. After removal of metallic or deleterious fractions, classification and product qualification, suitable tailings fractions may therefore provide an alternative mineral feedstock. This becomes particularly relevant in sand-constrained regions and for large tailings inventories, where manufacturing can potentially be located closer to the resource rather than transporting low-value raw material over long distances - The relevant comparison is increasingly not “tailings versus free natural sand”, but “tailings-derived feedstock versus manufactured sand”.

Yes. This is a fundamental part of the feasibility assessment. Inventory and market need must be mapped together.

The opportunity varies greatly by region. Where suitable natural construction materials are abundant and inexpensive, tailings-derived material may struggle to compete on product price alone. Where quality sand, aggregate or other mineral feedstocks are constrained, the opportunity can be considerably stronger.

However, the mining business case is not necessarily based only on revenue from selling aggregate. It can also include avoided or deferred tailings-storage capacity, reduced waste inventory and potentially reduced closure liabilities.

Therefore the assessment should consider inventory size and quality, distance to markets, competing quarry resources, transport infrastructure, product value, regional mine clusters and the mine's avoided waste-management costs.

The “size of the prize” is consequently highly site-specific rather than simply the global tonnage of tailings multiplied by construction-material prices.

This depends strongly on what is meant by the filter cake.

If it is filtered process tailings or treated process water, the same characterisation and separation principles discussed in the masterclass apply, although reprocessing may require repulping.

If it is water-treatment sludge/filter cake i.e. from sewage treatment , the situation will be very different. These materials may deliberately concentrate metals, arsenic, iron/aluminium hydroxides, gypsum or other contaminants, including biological material such E. Coli removed from the water. They therefore require a different disposal pathway.

Depending on composition, opportunities could potentially include recovery of valuable metals or specialised material applications, but some water-treatment residues may be better managed as controlled waste.

The origin and treatment chemistry of the filter cake therefore need to be understood first.

The first step is comprehensive characterisation of the tailings and identification of the mineral phases hosting the metals of concern.

Separating sulphide/metal-rich minerals from the larger non-metallic fraction can substantially reduce contaminant concentrations where those contaminants are associated with the separated phases. The resulting non-metallic stream(s) must then be independently tested against the applicable environmental criteria for its intended reuse.

Total concentration alone is not sufficient. Leachability and mineral stability are also important, because the environmental behaviour depends on how the contaminant is hosted. Leachability and ABA testing is a pre-requisite for repurposing where any potential leaching could occur.

If a stream fails the required criteria, options include further separation, treatment, or selecting a different appropriate end use. It should not simply be assumed suitable or unsuitable for aggregate or other applications.

Once environmental suitability has been demonstrated, it must separately meet the relevant aggregate/product standards.

A practical model is to introduce quarry-style materials management alongside the mining operation.

This can include excavation/HME, conveyors where appropriate, dewatering, screening/classification, sorting, blending and dedicated stockpiles by material type and particle size. This provides end users with more consistent feedstocks and allows QA/QC to be incorporated into material handling.

For future mines, this could potentially influence the original design of tailings and waste-rock management, with selected streams separated before disposal.

The objective is not necessarily to replace the TSF immediately, but to progressively reduce the quantity of material requiring permanent storage while increasing the proportion managed as recoverable mineral feedstock.

GHD has substantial practical experience in this field. Some experienced personnel have up to seven years of focused experience developing and assessing tailings and mine-waste recovery, reuse and repurposing opportunities, supported by experienced specialists with GHD's broader mining, tailings, processing, environmental, materials, construction and circular-economy teams. This multidisciplinary capability is important because successful repurposing projects extend well beyond conventional tailings engineering.

Regulatory requirements vary considerably by jurisdiction. In general, two separate hurdles need to be addressed.

First is the environmental/resource-recovery pathway: demonstrating that the material is suitable for its intended beneficial use and does not create unacceptable environmental or human-health risks.

Second is product compliance: an environmentally acceptable material does not automatically meet the technical standards required for aggregate, concrete, ceramics or another product.

There may also be mining, planning and tenure implications if quarrying, manufacturing or another activity was not contemplated by the original mine approval.

Early collaboration between the environmental regulator, resources/mining authority, planning authorities, quarry/materials operator and intended end user is therefore extremely valuable. Quarry operators are particularly useful partners because sorting, grading, blending, QA/QC and supplying materials to specification are already core parts of their business.

Addendum: A mining lease is generally approved for mining and associated mining activities, not for operating a commercial quarry or construction-material manufacturing business. Therefore, even if tailings can technically become aggregates or other construction feedstocks, the commercial pathway needs to consider: Mine operation -> recovery/cleaning of material -> approved resource/feedstock -> quarry/materials operator -> manufacturer/end user.

If quarry-style sorting, beneficiation, stockpiling or manufacturing is proposed on the mine lease, the existing development consent, mining lease conditions, environmental approvals and planning permissions need to be checked. An amendment or separate approval may be required depending on jurisdiction and scale. The lack of a single, clear, integrated approval pathway is the greatest challenge that needs to be resolved given the lack of precedents.

Yes. We have experience in South America, including a copper-tailings repurposing study involving metal recovery through bioleaching, mineral carbonation and development of soil/technosol-type materials.

At proof-of-concept level, the work demonstrated the potential to create useful pathways for a very high proportion of the original material. As with all such studies, translation from laboratory results to industrial-scale reuse requires further pilot testing, regulatory approval and market validation.