Chile is seeking to rescue the critical minerals from its mountains of mining waste, amid concerns this re-exploitation could damage communities and environments.
Tailings are the mixtures of ground rock and water left behind after extraction at a mine, their deposits resembling giant piles of scree. There are now 836 such deposits throughout Chile. These are mainly concentrated in desert regions, like Atacama in the north, where vast mineral reserves have helped Chile become the world’s leading copper exporter.
Communities have lived beside these deposits for decades but in recent years, their potential value has changed radically: they could be packed with critical minerals, such as cobalt and rare earth elements. These minerals are essential to the energy transition, for electric vehicles and renewable energy technologies. An analysis of a 1.7 million-tonne deposit in Spain last year, for example, suggested it could yield 168 tonnes of rare earth elements alone.
This has led to hopes that circular mining (reincorporating waste into the production cycle) could repurpose the world’s growing collection of tailings. On the other hand, environmentalists argue, this recycling could cause pollution and affect water supplies.
Luis Cisternas is a lecturer at the University of Antofagasta in the north, and a researcher for the Chilean capital’s Advanced Mining Technology Center (AMTC). He says reprocessing waste requires large amounts of energy and water – the latter being a particularly critical and scarce resource in the Chilean desert: “The major challenge will indeed be significant water consumption.” If not rigorously managed, Cisternas says, this consumption could compete with the water needs of local communities and fragile ecosystems.
‘Hidden gold’ in mining waste
Last year, the VTT Technical Research Centre of Finland published an evaluation of various secondary sources of rare earth elements, such as recycled electronic waste and red mud (bauxite residue). It deemed mining tailings to have the highest potential.
China currently dominates both the mining and processing of rare earth elements globally, accounting for around 60% of production and close to 90% of processing capacity. Aside from energy transition technologies and electric vehicles, critical minerals are integral to modern military equipment. A coalition of governments led by the US and Europe has moved to diversify critical mineral supply chains, elevating countries like Chile to strategic importance.
These are 17 varieties of heavy metal chemical elements distributed throughout Earth’s crust. Worldwide, there are 110 million tonnes of rare earths reserves, the US Geological Survey estimated in 2024.
The rare earths all have similar but unusual chemical and physical properties that make them critical for many modern technologies. For example, gadolinium is used in nuclear power reactors, while scandium finds use in vehicle fuel cells.
Rare earth elements fall under the broader term of critical minerals, which are key ingredients for modern technology. For example, the critical mineral lithium is vital for electric vehicle batteries, while nickel is used in stainless steel.
Humberto Estay Cuenca, director of the AMTC, says there is a unique opportunity for Chile to further solidify its status as a supplier of minerals – “if this is combined with a strategy for value extraction and socio-environmental solutions”. However, he warns that the economic viability of tailings’ “low concentrations” of minerals will prove a challenge.
Nevertheless, Chile’s National Geology and Mining Service (Sernageomin) is putting more resources into tailings deposits; it launched a National Observatory of Geological and Mining Hazards in October. The Sernageomin geographer, Silvia Arce, is this project’s technical director. “We want to establish a monitoring system that allows us as a state to have operational control, or a mirror of what is happening in each mine,” she explains to Dialogue Earth.
Each tailings deposit has a particular mineralogy. That means there is no one-size-fits-all solutionLuis Cisternas, researcher, Advanced Mining Technology Center
One example of successful tailings extraction is Minera Valle Central, in central Chile. High-pressure hoses are being used to convert deposits back into slurry, enabling mineral recovery. Those include copper and molybdenum, the latter used in steel alloys.
“This is then reprocessed and sold on the market,” explains Cristóbal Carrasco, a Sernageomin engineer. He says this hydraulic method reduces risks for workers by avoiding direct contact with unstable mountains of waste.
However, rolling out this technique is a “major challenge”, according to Cisternas: “Each tailings deposit has a particular mineralogy. That means there is no one-size-fits-all solution.”
The researcher warns the process must be extremely rigorous if it is to control and contain any potential chemical impacts: “Sometimes, rare earth elements are accompanied by radioactive isotopes that could be released into the environment, if the resumption of operations is not backed by dedicated studies.”
Regulatory barriers
Chile’s regulatory procedures are playing catch up to this potential. Amendments to the regulations governing the design, construction and operation of tailings projects are currently under debate in congress. The new regulations seek to promote the reprocessing, reuse and relocation of tailings, as well as give Sernageomin more inspection and management tools.
“The idea is to give any individual or company the opportunity to intervene in a tailings deposit, safeguarding its physical and chemical stability,” explains Carrasco.
At present, assessing a tailings pile requires virtually the same complex and costly permits as opening a mine from scratch. The new regulations would introduce the concept of “extraction deposits”, thus distinguishing simple waste accumulation from the activity of recovering minerals. This would enable the streamlining of permit processes, reducing bureaucratic costs and making it easier for small businesses or local innovators to invest.
Up until now, says Carrasco, lengthy administrative procedures have slowed down many initiatives.
But this red tape has not prevented some pilot initiatives from emerging: in Tierra Amarilla, a mining community in the Atacama region, tests have been conducted to make bricks from tailings.
However, such initiatives still represent a tiny fraction of the millions of tonnes of waste generated by copper mining each year.
The threat of waste
The need to tackle these waste mountains was underlined in 2024, at a mine in Cabildo operated by Las Cenizas, in north-central Chile’s Valparaíso region. The mine’s tailings dam failed, causing a spill that contaminated nearby streams. Solid tailings material flowed through the streets of nearby towns, damaging homes and triggering an environmental alert. Chile’s environmental regulations office (the SMA) fined Las Cenizas in 2025.
Of Chile’s 836 tailings deposits, about 80% are inactive or abandoned. Through its latest tailings policy, the Ministry of Mining is attempting to identify owners by referencing mining property studies.
Many belong to companies that are inactive or no longer exist – their owners have disappeared or died, leaving the state responsible for managing the risks. This situation also limits the government’s ability to act to secure deposits and manage those risks, such as physical damage caused by earthquakes or acid drainage. (The latter is chemical contamination of groundwater, triggered by water meeting these minerals to produce acid.)
The private sector can also play a role in securing the safety of tailings dams. Mario Escobar specialises in digital tools at Chile’s Blue Mining, a company working to optimise water use at mines. He argues that, with copper prices currently at record highs, investment in safety is a must. But he also says the region’s main challenge is its “access gap” – the combination of high implementation costs and insufficient technological infrastructure that is holding back small- and medium-scale tailings enterprise.
Software companies have developed tools that use artificial intelligence algorithms to monitor the stability of tailings. This enables the prediction of potential failures in the event of earthquakes or torrential rain.
Digital monitoring is supplemented by satellite imagery, which can detect minute changes in moisture levels or deformations in abandoned tailings. This is helpful for remote areas that human inspectors are often unable to reach.
Environmental concerns
For communities close to tailings, the possibility of a failure – combined with the possibility of exploitation – can fuel a constant feeling of vulnerability.
Michael Lieberherr, a researcher for the Chilean environmental defence NGO Ecosistemas, warns that saturated waste sites have turned some localities into environmental “sacrifice zones”. He adds: “The fear is not just of collapse, but of the persistence of heavy metals in the ecosystem that have never been remediated.”
Dialogue Earth also talked to Manuel Cortés, president of Chadenatur. This environmental group represents the northern coastal city of Chañaral, which has been marked by decades of mining pollution. Cortés views the growing interest in tailings with caution: “Generally, the main interest is to exploit the minerals that companies are interested in.”
For many residents, there is a fear that any promises of environmental remediation will simply be used as an excuse to reopen old deposits, without fully addressing the potential health impacts. Because as well as leaching harmful substances into their surroundings, mining tailings have been linked to respiratory illnesses through the dust they release.
A study published by the journal Minerals in 2024 warned reprocessing tailings could lead to increased water consumption. It also said there was the potential for toxic substances to be released, which could have “negative environmental consequences”. It recommended the continued improvement of these technologies, with a focus on environmentally friendly methods.
Then there are the financial viability concerns: last year’s analysis of a Spanish tailings deposit suggests the costs involved in extracting the rare earths there were not offset by their value.
Circular mining promises to turn a historical environmental liability into a new source of strategic resources.
But, as scientists warn, viability depends on ensuring this reprocessing does not also recycle the environmental and social risks that litter northern Chile’s mining history.
