Project page updated 28 February 2023
The sand challenge
After water, sand is the second most exploited natural resource in the world. The demand for this material is growing exponentially around the world with urbanisation, development, population growth and sea-level rise. Yet, extraction of sand and gravel from rivers and the nearshore environment is already an environmental and resource problem.
Despite increased recognition of sand as a strategic resource for sustainable development, the issue remains largely unaddressed and unresolved in many places around the world. With the coming post-COVID recovery investment in infrastructure construction – the largest demand sector for sand by volume – this situation needs to change urgently.
Finding alternative sources of sand
The Development Minerals Strategic Program's work has demonstrated that by-products of metal mining can be used as a viable and sustainable ore-sand for construction (aggregate) or other industries (silica sand), displacing the need for sand extracted from the natural environment. Ore-sand is a type of manufactured sand resulting from the mining and processing of ores; its co-production implies the optimisation of these processes and the addition of processing stages to achieve the required specifications of sand.
Why now?
Attempts to give mining residues a second life have been made in the past, and suitability for certain applications has been proven. However, serious uptake has been impeded because these residues have not been specifically designed for their intended purpose, and there has been reluctance by the public to use mineral wastes in products. Instead, our approach is to use mineral processing techniques to extract and process clean sand by-products with desired physical and chemical properties, thus reducing the generation of wastes in the first place.
Now, awareness of the growing sand sustainability challenge is generating clear calls for alternatives at scale. At the same time, changes in mining, environmental and waste policy mean large volumes of mine tailings now need to be treated differently in many places in the world. The rising value of sand and the costs of storing mining residues may give new impetus to a circular economy synergy with a strong contribution to sustainable development.
Vale Ore-sand
Over the course of 2021, in collaboration with The University of Geneva, our team sampled, tested and evaluated sandy co-products of the iron ore operation in Brucutu (Minas Gerais, Brazil), developed potential resource substitution strategies, and interviewed stakeholders in the mining and construction sectors to understand the uptake and scalability of the innovation.
As we worked through technical testing, we engaged in constructive dialogue with major stakeholders including artisanal, large- and small-scale miners, construction and manufacturing industries, standard setting institutions and regulatory bodies.
In this project, we also mapped and matched mine tailings generation sites with sand consumption markets around the world. Furthermore, we demonstrated the potential environmental benefits of co-producing this alternative sand (i.e., ore-sand) in mineral processing circuits compared to conventional sands from a holistic Life Cycle Assessment perspective.
Newcrest Ore-sand
Newcrest Mining Limited is a member of the Julius Kruttschnitt Minerals Research Centre’s Collaborative Consortium for Coarse Particle Processing Research. As part of this, Newcrest has been pioneering work on installing and testing the HydroFloat technology for coarse particle flotation in their copper-gold operation. This technology has proven beneficial in reducing energy consumption during comminution and improving recovery of gold and copper in coarser size fractions compared to conventional flotation technologies. Simultaneously, the HydroFloat cell allows obtaining a reject stream consisting of a coarser, silica-rich material that can potentially become a sand substitute.
Newcrest engaged with us in 2022 to evaluate the potential for co-producing ore-sand at Cadia East operation (copper-gold ore) in New South Wales, Australia. In the initial phase of this project, we performed a comprehensive characterisation of the sandy material from the HydroFloat equipment, involving a suite of physical, chemical, mineralogical, environmental and geotechnical tests. We found that the HydroFloat reject may be a suitable substitute of fine aggregates in construction applications.
Impact
Vale’s ore-sand case study was profiled in UNEP’s sand and sustainability report as part of a series of recommendations to promote resource efficiency and circularity by substituting the use of naturally sourced sand with alternative products. The outcomes of this research were also presented at the United Nations Environment Assembly (UNEA) and received extensive international media coverage, reaching audiences worldwide. Here are a few examples of news pieces:
Eos VOL. 104, NO. 3 | Grains of Sand: Too Much and Never EnoughMining Magazine, 30 May 2022 | Vale on its 'ore-sands' revolutionAustralian Mining, 19 April 2022 | "Ore-sand” kills two birds with one grainInternational Mining, 30 April 2023 | Vale’s Sustainable Sand to impact tailings generation plansSustainable Minerals Institute, 15 November 2021 | New step in mineral processing could help prevent sand sustainability crisis
Our research explores if co-products of ores can provide just and responsible alternative sources of sand, which is a timely contribution to processes like the implementation of the UNEA-4 Resolution on Mineral Resource Governance. In the medium to long term, this project is expected to contribute to fundamental knowledge of methods and assessment procedures for testing the viability of sand alternatives.
If ore deposits emerge as viable sources of sand capable of meeting demand across a range of commodities and locations, the project may also produce cutting-edge applied knowledge and innovative insights into a convincing circular economy solution to the degradation of our natural environment from the huge scale of sand extraction and unsustainable management of mining waste.
