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What causes tailings, and what can we do to reduce their impact on nature?

While mining uses less than 0.1 per cent of the world’s land, its impact can be considerable in ecologically and culturally sensitive areas.

ICMM members are committed to helping work towards a nature positive future, through large-scale environmental conservation and restoration, and a crucial part of this work is the responsible and innovative management of tailings.

Essential materials such as copper, gold, iron and aluminium are contained within underground ore deposits. When the minerals are extracted from the ore through mining and processing, this results in waste materials called tailings. In simple terms, tailings are a by-product of mining, a wet slurry that is made up of crushed rock, water, trace quantities of metal and in some cases chemical additives used during ore processing.

ICMM members are committed to implementing the mitigation hierarchy to manage their impacts on nature. This means following a sequential four-step process: Avoid, Minimise, Restore and Offset, which can be applied for all aspects of the mining and metals lifecycle, including tailings management.

Avoid

Avoiding impacts on nature from tailings can include avoiding disturbing habitat for new tailings storage facilities and avoiding pollution from stored tailings, in particular from spills.

If a tailings facility fails it can pose a threat to nearby communities, wildlife, aquatic life and plants. In January 2019, a dam retaining tailings failed, releasing 9 million cubic metres of tailings, and killing 270 people in the town of Brumadinho, Brazil. In November 2015, a tailings dam at the Samarco mine in Brazil collapsed, killing 19 people and impacting hundreds of kilometres of aquatic and riverine habitat. And in August 2014 a tailings spill in Canada caused major environmental damage. Other tailings facilities around the world have had issues over the years and the impact on lives and the environment can be catastrophic.

Responding to these disasters, ICMM, together with the UN Environment Programme (UNEP) and Principles for Responsible Investment (PRI), convened the Global Tailings Review, which established the Global Industry Standard on Tailings Management (GISTM). The Standard is an important milestone towards achieving the ambition of zero harm caused by tailings facilities to people and the environment.

Core to the work that members undertake on tailings is their conformance with the GISTM and you can find out more in ICMM’s latest progress update here.

Minimise

Minimising impacts to nature through tailings includes reducing contamination of the surrounding environment and reducing the amount of tailings produced, which in turn helps minimise water consumption for tailings.

At its Paragominas mine in Brazil, Hydro is using a Tailings Dry Backfill method, where tailings that have been dried for 60 days are deposited in areas that have already been mined.

This innovation reduces the environmental footprint and increases the safety of the operation by eliminating the need to expand existing storage facilities or build new ones in the future. The process also reduces potential sources of contamination to soil and groundwater as the inert tailings posess similar chemical and physical characteristics to the original ore extracted. 

In Chile, Anglo American has been testing Hydraulic Dewatered Stacking technology, where tailings are placed and compacted in a mound that naturally dries out, significantly reducing the overall volume of tailings that need to be stored.

Restore

Exciting new techniques and approaches to reclaiming and restoring old tailings storage facilities are also being implemented at sites around the world. Decommissioned in 2002, the South Tailings Facility (STSF) at Gold Fields’ Damang mine in Ghana has been rehabilitated into a self-sustaining ecosystem with pond areas restored into a healthy wetland and watershed. Various crops such as oil palm, cocoa, coconut, citrus, timber species, and multipurpose trees are now grown here. The restoration process encompassed effective stakeholder involvement, removal of ancillary facilities, earthworks, agroforestry systems, water management, soil protection and nutrient enhancement, as well as environmental monitoring, and testing. The mine has since applied the STSF restoration principles on another tailings facility, which was decommissioned in 2018 and stretches over 120 hectares. 

The heap leach operations and tailings storage facilities at the nearby Tarkwa mine (the largest gold mine in Ghana also managed by Gold Fields) have, since their closure in 2012 and 2019 respectively, also been successfully rehabilitated with multipurpose trees, food, cash and tree crops such as rubber, teak, and oil palm.  

The tailings restoration efforts and general rehabilitation programmes at Damang and Tarkwa have contributed to protecting and enhancing biodiversity and wildlife – including those of conservation significance (IUCN Red List of Threatened species) such as the Tree Pangolin, Dwarf Crocodile, Mona Monkey, Straw-coloured fruit bat, Copper-tailed glossy starling, Grey Parrot, Green-tailed Bristlebill, Rufous-winged Illadopsis and Red-fronted Antpecker. 

While Rio Tinto, thanks to research with the Sustainable Minerals Institute and the University of Queensland, is trialling a new solution that turns bauxite residue into a soil-like substance that can be replanted in just two years. It also reduces impact on the environment, as it doesn’t require a permanent pond location, and there’s no call for heavy machinery to dig and distribute a topsoil cap.

Offsetting

Offsetting is a last resort for all ICMM members, not a primary solution to impacts from tailings or other types of operations. Any necessary offsets must be developed in a robust, science-based and respectful manner to support communities, ecosystems and all impacted stakeholders.

Tailings continues to be an issue of significant concern for the mining and metals industry’s stakeholders, and responsible management of tailings is foundational to help rebuild the trust lost through disastrous failings in the past. Maintaining rigorous standards and pursuing innovation are central to this, and ICMM’s members are committed to leading the way to a safer, responsible future that protects both people and planet.