Chile's mine tailings: Problems and solutions

Chile's abundant mine tailings constitute a serious risk for the population and the environment, and partnerships between the public and private sectors are considered crucial to promote secondary processing that can exploit this waste and curb the problem.

There are 764 tailings dumps dotted across the country, of which 473 are inactive and 173 abandoned, according to a survey by national geology and mining service Sernageomin.

Proper management of old and new tailings is considered essential for sustainable mining, since they are rich in toxic minerals such as arsenic, cyanide, chromium and lead, among others, which can produce serious impacts on human health and ecosystems.

That necessitates coordination between the public and private sectors, as well as academia, according to a study by Universidad de Chile, presented during a webinar organized by Fundación Chilena del Pacífico to address the industrialization of mining resources.

Development plans for new mining projects must also include measures to mitigate their impacts and they must clearly address the management and monitoring of mine tailings, the webinar was told.

Chile’s national mining policy, published by the mining ministry, states that the goal is to reduce the production of tailings and ensure that 100% of tailings dumps are authorized deposits by 2044, eliminating all such dumps by 2050, in addition to producing and following a comprehensive monitoring plan that involves reporting to Sernageomin on their physical and chemical stability in the meantime.

However, "a large proportion of tailings dumps are currently in an inactive or abandoned state, although there are specific concession opportunities for national and international companies that are interested," said Andrés Bórquez, academic coordinator at Universidad de Chile.

There is the possibility of creating concessions to process the minerals present in abandoned tailings, which means that "Chile has concrete opportunities in rare earths," since many of these elements, crucial to renewable energy or technological applications, are present in mine waste, Bórquez said.

This opportunity to recover rare earth elements from tailings is something that EcoMetales, a subsidiary of state-owned miner Codelco, is looking to tap in a project being co-financed by development agency Corfo and slated to be carried out using waste from iron ore mining in the Atacama and Coquimbo regions.

"There is a potential business involving recovering value from [mine] waste that requires further technological development, which is a challenge for the country, its professionals and the mining industry if we want to move towards more sustainable mining," Carlos Rebolledo, business development manager at EcoMetales, said in a statement issued earlier this year.

"Developing studies and policies for the extraction, refinement and transformation of mine tailings will allow more minerals to be extracted and will be in line with a more sustainable circular economy," said Dorotea López, director of international studies at Universidad de Chile, speaking to BNamericas last month.

Another approach to deal with tailings is being investigated by Chile’s center for advanced studies in arid zones (Ceaza). Ceaza researchers are examining the possibilities of treating mine tailings through phytoremediation, an approach that entails using plants such as quinoa to remove pollutants or reduce their bioavailability in the soil, air, water or sediments by absorption, accumulation, metabolization, volatilization or stabilization, the center said in a statement.

“Tailings cannot be decontaminated (unless they are moved elsewhere), they can only be stabilized, said Teodoro Coba, lead researcher of the biotechnology initiative. “The utility of growing plants and creating vegetation cover on mine tailings is to stabilize those tailings, since the roots and rhizospheres of plants can absorb and/or immobilize heavy metals, minimizing the mobilization and diffusion of these pollutants into the surrounding environment," he added.

“We already have some preliminary results. I think that by the end of March 2023 we will have some interesting results that could be disseminated and sent to a scientific conference. At the end of the project, in March 2025, we should have all the results required," said Coba.