Mining waste is a global issue. Since it has no value and many mines are remote, transporting, burying, or treating it is not cost-effective. Although many recycling and reuse methods under consideration are not yet commercially viable, some innovative techniques are worth pursuing.
Mining waste can serve as a valuable resource
Mining waste can be crushed ore, wastewater, or slag. Today, mines generate approximately 14.3 billion t of tailings annually. By 2050, it will rise to an estimated 2.2 trillion t, making it one of the fastest-growing waste streams worldwide.
Recycling or reuse is challenging with conventional means, but it is necessary since many metallurgical wastes are toxic and harm the environment. Industry professionals should consider this waste an asset, not a problem. With the proper techniques and tools, they can transform it into a useful, sustainable product, supporting the circular economy.
Even if they discover a way to separate waste from valuable minerals, what should they do with the recovered materials? The construction industry is responsible for 42% of global greenhouse gas emissions, making it a prime candidate.
Making mining cleaner with innovative techniques
Experts estimate the world’s mines generate tens of billions of tonnes of tailings annually. Since they are so abundant, they are ideal for synthesising cost-effective cementitious items. Aluminium and silicon-rich waste byproducts can supplement raw materials.
Chemical activation works with nearly all kinds of tailings – an excellent discovery, given their complex composition. If scientists limit reagent types and concentrations, they can minimise the risk of secondary pollution from waste liquid, thereby keeping recovery environmentally friendly.
Masonry is an excellent alternative to cement because it can hold three times the weight, even though it is softer. Its compressive strength is three times higher, and it can last decades in a hardscape. Adding iron ore, granitic or gold tailings to the clay matrix as a degreaser improves the extrusion parameters and reduces shrinkage during firing, preventing cracks.
Industry professionals can even look downstream for inspiration. Coal ash contains an estimated 288 000 t of lithium, which is enough to supply the US market for 100 years. Extraction is more sustainable than mining these materials outright, which produces 1 t of radioactive residue, 12 000 cubic metres of waste gas, and 75 cubic metres of wastewater.
When will these methods be commercially viable?
Transforming mining waste into construction materials is possible today. However, many techniques are expensive or scale poorly, so they aren’t yet commercially viable. Due to their economic and environmental benefits, they are worth pursuing vigorously.
For reference, researchers at The University of Texas at Austin discovered America’s coal ash stock contains enough rare earth elements to bolster the national supply without new mining. It could contain up to 11 million t, almost eight times the amount in domestic reserves in 2025. This is crucial since most of the stores come from imports.
Mines guide the future of sustainable infrastructure
This is a relatively new area of interest, so it may be some time before mines can adopt innovative techniques – especially those in remote locations. However, since there is money in the venture, it will likely grow rapidly.