Coal mining has been a mainstay of the South African economy for well over a century, driving economic growth, generating export income and providing a reliable, affordable source of energy. As conversations about responsible mining gain traction, innovations in responsible mine closure could be pivotal.
Thashni Chetty, African Mining Lead for WSP in Africa, says: “While coal mining generates valuable resources, it also produces substantial solid discard that can contribute to environmental pollution. Once mining operations cease, the mine site can still impact the environment if the site has not been properly closed and rehabilitated. The consequences of ineffective mine closure in South Africa are evident from the prevalence of abandoned mines and operations that remain in prolonged care-and-maintenance. The transfer of mines to companies with fewer resources for closure, along with the rise in illegal mining activities, further highlights this issue.”
There are approximately 108 operational coal mines in South Africa, according to GlobalData’s mines and projects database (2023). Coal beneficiation – processing raw coal to meet certain quality standards – generates significant discard, traditionally managed through surface disposal, which poses long-term environmental liabilities. These liabilities remain even after mining operations cease, so that abandoned or ineffectively closed mines can continue to pose risks to the environment and surrounding communities.
As the mining industry grapples with environmental challenges, planning for responsible mine closure is key. Gloria Dube, Geoscientist at WSP in Africa, urges that mine operators should start thinking about mine closure strategies in the initial planning stages. “Ideally, plans for mine closure should form part of every mining stage to avoid the historic trend of mines being abandoned without adequate rehabilitation measures.”
In-pit disposal of coal discard is increasingly recognised as a viable solution for responsible mine closure in South Africa. A recent study by WSP in Africa – presented by Dube at the South African Institute of Mining and Metallurgy (SAIMM) Mine Closure Conference in February 2025 – explored this method as an alternative to traditional surface disposal. The study highlights in-pit disposal’s potential to mitigate/minimise Acid Rock Drainage (ARD) and Metal Leaching (ML) impact on the environment while aligning with regulatory compliance.
“In-pit disposal, where discard is placed into mined-out pits, offers a controlled environment that reduces oxygen exposure, a key driver of acid generation,” Dube explains. “The study evaluated the geochemical behaviour of old and fresh coal discard – and revealed that old discard is highly acid-generating, with minimal buffering capacity, while fresh discard initially maintains a neutral pH but risks acidification under extreme oxidation.”
Overall, the risk assessment indicates that in-pit disposal of coal discard is a viable option if the discard is disposed below the final pit water level (selective placement) where no or little oxidation of pyrite will take place, minimising ARD generation. Compared to surface disposal, it significantly prevents secondary mineral formation such as gypsum and jarosite (acid-storing sulphate) and eliminates the need for additional land use – making it a more responsible alternative.
This study was aligned with the South African Best Practice Guidelines which advocates risk-based source-pathway-receptor approach and emphasis of the use of geochemical and geohydrological models to assess contaminant transport and risks. It further demonstrates that strategic in-pit disposal, coupled with timely backfilling, compaction, and rehabilitation can enhance environmental stability, safeguard groundwater resources, and contribute to responsible mine closure strategies.
As approaches and technologies advance, plans may change, Dube admits. “Yet planning for and implementing in-pit disposal allows mine operators to mitigate their impacts as they go and keep future issues from becoming major obstacles at closure stage.”
Integrating closure from the beginning is better from a profitability point of view as well. Implementing responsible solutions during operations reduces end-of-life remediation costs. “These costs can accumulate to millions of Rands by the time a mine reaches closure, if impacts are left to accumulates over the years,” Dube says. “And while mineral right holders await closure certificates, environmental impacts and legal liabilities remains their responsibilities.”
“It doesn’t matter how big or small the mining operation is, effective and responsible mine closure is a critical conversation for South Africa,” Dube says. “The studies we do now examine responsible practices that can be implemented during operations – helping our clients to meet changing regulatory requirements. But ultimately, address environmental issues throughout the mine's lifecycle to ensure proper rehabilitation and repurposing that is safe for the environment and the communities living in the area.”
“As the industry shifts towards responsible mining practices, adopting in-pit disposal – selective placement - for coal discard offers a pragmatic solution to reducing environmental footprints while ensuring compliance with evolving regulatory frameworks. Our study underscores the importance of innovative discard and waste management solutions in shaping the future of responsible mining in South Africa,” concludes Chetty.
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