Circular Economy in the South African Mining Industry: A Sustainable Framework for Waste Prevention, Tailings Valorization, and Ecosystem Regeneration

Abstract

The transition of South Africa’s mining sector from a linear take–make–waste model to a circular economy is critical for environmental sustainability and resource security. While the existing literature heavily favors generic, theoretical solutions, this review paper bridges the gap by mapping validated circular technologies directly onto named local operations and specific regional waste profiles. By pairing engineering innovations such as automated sorting and geopolymer synthesis with site-level mineralogical realities and techno-economic limits, this work provides a realistic blueprint for sustainable resource management and holistic landscape restoration. However, widespread implementation is currently constrained by a lack of commercial-scale data, low data transparency regarding corporate waste inventories, static economic modeling, and ambiguous regulatory definitions that separate waste from by-products. To overcome these limitations, a phased, internationally benchmarked policy roadmap aligned with South Africa’s critical minerals strategies is proposed. Future research should focus on industrial field trials, blockchain-secured geospatial waste databases, dynamic life-cycle assessments, and cross-sector synergy mapping. Ultimately, aligning technological innovations with updated waste classification standards, specialized tax incentives, and carbon-credit structures will allow South Africa to mitigate its legacy environmental liabilities while safeguarding its position in the shifting global critical minerals market.

1. Introduction

The global demand for minerals continues to surge, not only driving economic growth but also intensifying critical environmental and social problems. Among the most crucial issues are the management of mining waste, environmental impacts, and the destruction caused by mining deforestation [1]. Mining is a process that involves activities that include metal extraction, smelting, and refining, which later result in waste and air pollution [2,3]. Waste generated from these activities has significant environmental and economic implications worldwide (Figure 1), including tons of waste rock, tailings, and contaminated water produced each year [4]. The mining sector in South Africa plays a vital role in the economy but faces issues related to pollution, legacy waste, and mine closures without rehabilitation [2,3]. According to the Mineral Council of South Africa, the country holds an estimated 6.1 billion tons of historical tailings deposits, and the anthropogenic effects of mining and metal extraction activities can result in irreversible damage to the environment and to humans if not managed properly [5].

Figure 1. The global estimate of production-related waste management in metal mining (2012–2021), comparing three disposal pathways: energy recovery, treatment/recycling, and direct disposal/releases [6].

Figure 1. The global estimate of production-related waste management in metal mining (2012–2021), comparing three disposal pathways: energy recovery, treatment/recycling, and direct disposal/releases [6].

Key observations on waste volumes vs. production are that total waste managed fluctuated between 1000 and 3000 million pounds annually, peaking around 2014–2015 [6]. Mine production remained stable at 1.2 M tons, indicating waste generation is decoupled from production volumes [6]. Regarding waste management trends, disposal/releases are likely landfills- or emissions-dominated but declined after 2015, suggesting improved practices [6]. Treatment or recycling of waste, such as tailings reprocessing, showed modest growth, reflecting the slow adoption of circular-economy methods, while energy recovery was minimal, highlighting untapped potential for valorization. The implications are that, despite stable production, waste management shifted slightly toward recycling, though disposal remains the primary route. Gaps persist in sustainable waste conversion, aligning with broader critiques of mining’s linear economy model, which also has major implications in wastewater management in South Africa’s mining sector, as shown in Figure 2.

According to the Department of Mineral and Petroleum Resources (DMPR), the South African mining sector in 2024 contributed 6.1% of nominal GDP, which is a direct contribution of R450.5 billion, down from 6.3% in 2023, while its gross added value of R203.7 billion represented 4.4% of GDP, behind manufacturing (11.2%) but ahead of agriculture (2.2%). This continues a long-term structural decline, with the mining sector’s share of national GDP falling from over 20% in the 1980s to about 8% in 2016 and to 6.1% by 2024, as presented by Statistics South Africa. The industry has fallen from second to sixth among the contributing sectors, and the gold-production index has dropped from 359.0 in 1980 to 48.4 in 2015, an 87% reduction [7]. Despite this, the sector remains economically significant, with the total mineral sales value rising by 9.1% to R865.8 billion in 2024, mineral exports reaching R585.6 billion, and direct employment standing at 474,736, 1.2% lower than in 2023 and accounting for under 3% of total formal employment (DMPR, 2025 [8]). Production declined across most commodities, with precious metals output falling by 2.1% to about 383.4 t and coal easing by 0.2% to 256.6 Mt; the precious metals sector still had a lead in both revenue (39%) and employment (59%), supported by a 22.6% rise in gold prices (DMPR, 2025 [8]).

These legacy operations also carry large waste liabilities that double as untapped secondary resources. The Witwatersrand basin alone holds 6 billion tons of tailings, which in situ mining analysis indicates an under-exploited residual gold endowment of up to 420 tons hosted in detrital sulfides [9]. Surface tailings retreatment is already commercialized by DRDGOLD’s Ergo and Far West Gold Recoveries operations, which have produced 96,000–155,000 ounces (2.9–4.8 tons) of gold per year in recent years from reprocessed dumps. At the same time, acid mine drainage (AMD) from these legacy systems threatens the water supply of Gauteng and its catchments and prompted a government long-term treatment program estimated at R10–12 billion [10,11]. As illustrated in Figure 2, mining accounts for roughly 3% of the nation’s water consumption; however, around 60% of mine waste is directed to tailings facilities, from which AMD return flows migrate into much larger regional basins, contaminating water sources. AMD from the Eastern and Central Basin gold mines increases the salt load of the Vaal Barrage by approximately 13%. In Mpumalanga, coal-derived AMD deteriorates the Olifants system, and gold–uranium seepage impacts the Crocodile River. Consequently, Figure 2 highlights the water-quality issue that even a small water abstraction can act as a pollution multiplier, leading to downstream remediation costs estimated at about R12 billion annually.

Figure 2. South Africa’s water consumption by sector [12].

Figure 2. South Africa’s water consumption by sector [12].

Gold and coal mining in South Africa have been associated with air pollution. Excavation, blasting, and transportation release fine particulate matter, which can travel long distances and affect respiratory health [13,14]. Fossil fuel combustion during mining activities, such as excavation, contributes to greenhouse gas emissions and results in poor air quality [15,16].

Blasting activities release not only dust but also gases such as nitrogen oxides (NOx) and sulfur dioxide (SO₂). Tailings, which are often dry and exposed, are major dust sources during windy conditions [17]. Studies show increased rates of asthma, bronchitis, and pneumonia among people living near mine dumps [15,16]. It is estimated that over 1.6 million South Africans live near mine dumps, often in informal settlements with limited access to healthcare. These communities are historically marginalized, making air pollution a social equity issue as well [18,19]. This shows how Environmental Management regulations on air quality control and air pollution (Figure 3) are poorly implemented.

The visibly burning coal dump confirms uncontrolled particulate matter emissions as documented in SA’s 2023 National Air Quality Report [20]. Sulfur dioxide (SO₂) and nitrogen oxide (NOx) release matches Eskom’s 2022 emissions inventory for the Hendrina Power Station [21,22]. In 2024, the Center for Scientific and Industrial Research (CSIR) reported that 12% of Gauteng’s ambient particulate matter (PM10) originates from coal mining [23]. This quantifies how coal handling (Figure 3) disproportionately degrades air quality in mining regions, aggravating the respiratory risks for nearby communities.

The proximity to water sources supports the 2022 Department of Water and Sanitation report on AMD from coal ash dumps, which found that 63% of Mpumalanga’s surface water samples showed coal-derived heavy metals [24,25]. Various mining companies have adopted air pollution control techniques such as spraying water or planting grass, which often fail during dry seasons [26]. Harmony Gold mine air pollution remediation initiatives include dust suppression systems, revegetation, and wind barriers to reduce particulate emissions. Companies are increasingly using air-quality monitoring systems and submitting reports to regulators. Other mining companies include Anglo Gold Ashanti, which uses water-monitoring systems at the Mponeng Mine and implements circular-economy principles in wastewater and air-pollution control [27,28].

The Gold Fields Mine participates in air-quality monitoring and reports on environmental performance in sustainability disclosures. Sibanye-Stillwater has implemented air-quality monitoring systems and uses wind barriers and revegetation to mitigate dust fallout [29]. These companies are aligning national regulations, such as the National Environmental Management: Air Quality Act, and submitting reports to the National Atmospheric Emission Inventory System (NAEIS). Their efforts reflect a growing commitment to transparency and sustainability in South Africa’s mining sector.

Existing literature on circular mining typically evaluates technologies in a generic, isolated manner, with little mapping to specific South African ore bodies, operations, or legacy-waste inventories. It also fails to address site-specific applicability and commercial feasibility, since the theoretical technical potential is rarely linked to site-level techno-economic and regulatory contexts. The literature is also currently missing clear policy mechanisms for South Africa, where key enabling frameworks, such as national standards for tailings valorization and carbon-credit structures, are not systematically articulated. This review bridges these gaps by mapping validated technologies directly to named local operations, linking them to specific regional waste profiles and to concrete policy roadmaps, and coupling them with techno-economic assessments. It also provides a contextualized feasibility analysis by pairing technical systems with site-level mineralogical constraints, such as jarosite encapsulation, economic limits, and water-licensing parameters. The review provides an actionable policy roadmap, proposing a phased, internationally benchmarked implementation aligned with South Africa’s 2025 Critical Minerals and Metals Strategy and the integrated circular framework, which connects diverse waste-to-value solutions, such as electronic sorting, geopolymer binders, and spekboom agroforestry, into a unified ecosystem recovery plan.

The scope of the review extends across the three circular-economy principles, Design Out Waste, Keep Products and Materials in Use, and Regenerate Natural Systems, applied to the Witwatersrand goldfields, the Bushveld Complex Platinum Group Metal (PGM) deposits, and the Mpumalanga coalfields.

2. Circular Economy in the Mining Sector

The circular economy (CE) offers a transformative approach by prioritizing waste prevention, resource recovery, and ecosystem regeneration [1]. This includes reprocessing tailings for construction materials and recovering metals from AMD, turning liabilities into revenue streams [1]. South Africa’s mineral diversity accounts for 88% of global PGM (Platinum Group Metal) production and 83% of global manganese, positioning it to lead CE adoption and align with global trends of decarbonization and resource efficiency [30]. Mitigating the effects of such mining, metallurgical, and metal manufacturing processes requires a holistic waste management approach that incorporates reducing waste production, in-process recycling, and finding new markets and applications in other sectors of the economy [31,32]. The circular economy (CE) model has three main principles. The first principle, Design Out Waste and Pollution, imposes waste management to intelligent material flow and system design [1,33]. The second principle, Keep Products and Materials in Use, prescribes maximizing resource utility and economic value by maintaining materials within a closed-loop cycle. The third principle, Regenerate Natural Systems, promotes economic activities that actively restore and enhance natural capital, including soil fertility, water quality, and biodiversity [1,33]. Collectively, these principles provide an integrated approach to sustainable development and a guide for transitioning from a linear economic model.

The linear economy model in South African mining (Figure 4) perpetuates uncontrolled waste accumulation, as seen in tailings dams and AMD pollution. Mitigating these impacts requires a comprehensive approach integrating waste reduction, in-process recycling, and cross-sectoral valorization. According to the Department of Mineral Resources and Energy, 60% of SA mine waste ends up in tailings dams, with less than 5% tailings recycled. AMD generation from abandoned gold mines affects 1.6 M people [34]. According to the Department of Water and Sanitation, remediation costs for legacy mines amount to R12bn/year [35]. The linear economy model also exacerbates water scarcity, with 3% of national water use dedicated to mining activities, as shown in Figure 4.

The 3% water use appears minor, but under the linear economy, this small input accounts for 60% of water waste, resulting in toxic tailings that pollute water sources [12,36]. This mismatch reveals the linear model’s flaw; therefore, transitioning to the circular economy model, which incorporates the recycling process and treating AMD for reuse, would align that 3% with sustainability, turning waste into value.

The key findings in Figure 5a depict toxic water pollution, showing mine void water (Central Basin) with extreme metal concentrations of 200+ units for some elements, confirming that unremediated mining sites become localized pollution hotspots [37]. Kilp River and Klipspruit retain dangerous levels of 50–150 metal units, demonstrating how linear models export contamination to ecosystems.

Tailings storage facilities (TSFs) in Figure 5b show enrichment factors of up to 80× for metals such as uranium (U) and lead (Pb), validating our earlier findings that 60% of waste ends up in tailings dams [37]. Wetland EF values of 20–60× indicate that metals migrate, affecting the water sources of nearby communities, aligning with the 1.6 M people impacted by AMD [37]. These graphs illustrate the cost-shifting inherent in linear systems: mining consumes 3% of water, enabling pollution multipliers (Figure 5a,b), with cleanup costs of R12bn/year.

Therefore, the broad objective of a circular economy model is to reduce the linear flow of materials through recycling and reuse, thereby extending their life-cycles. This makes the recycling of mine waste a practice that extracts new valuable resource ingredients, or uses the waste as feedstock, and converts the entire waste stream into a new valuable product [1,32]. In this context, a sustainable circular economy is defined as a transition in which the value of products, materials, and resources is maintained in the economy for as long as possible, and waste generation is minimized [1,32]. Figure 6 emphasizes resource efficiency, water recovery, waste reduction, and economic growth. It also illustrates how mining and metal extraction generate waste streams that can be recycled into secondary sources, supporting sustainability.

According to Statistics South Africa, the mining sector is at a critical stage, facing economic and environmental pressures that require an urgent strategy. Economically, the industry’s share of the national Gross Domestic Product (GDP) has declined from over 20% in the 1980s to just 8% in 2016, as shown in Figure 7.

Mining ranked 2nd in 1980 and 6th in 2016. This decline underscores an urgent imperative to unlock new, sustainable revenue streams and revitalize the sector’s economic relevance. Figure 8 shows the trend of gold production in South Africa from 1980 to 2015.

As shown in this figure, South Africa’s gold production index has declined steadily from January 1980 to January 2015. The index plummeted from 359.0 in 1980 to 48.4 in 2015, representing an 87% decrease in monthly production volume over the 35-year period. This fall visually summarizes the importance of gold mining to the national economy, which saw gold’s contribution to GDP dropping from 3.8% in 1993 to 1.7% by 2013, causing South Africa to fall from the world’s top gold producer to sixth place in 2014.

Yet, this declining production also represents an untapped economic reservoir. The quantification of over 400 tons of residual gold locked in Witwatersrand tailings dams indicates that the sustainability burden of legacy waste is also a recoverable resource [9]. The proven profitability of surface-retreatment operations such as DRDGOLD’s Ergo, which recovers gold from reprocessed tailings on a commercial scale, provides a tangible model for how the sector can generate new revenue and employment. Therefore, this historical production data validates the regenerative solution that leverages circular economy principles to unlock value from legacy waste, thereby creating a new, sustainable economic pillar for the mining industry and mitigating the long-term liabilities left by the linear model.

The mining and metal extraction industries can be integrated to form a circular economy model that promotes zero waste by reusing and recycling these waste materials. The different waste streams can be considered secondary sources of valuable metals and other resources [1,39,40]. The recyclability of waste materials depends on the availability of methods and technologies, as well as the existence of markets for recycled products [41]. Aligned with global shifts toward circular-economy principles and in response to the need for sustainable mining practices, this framework aims to reduce reliance on primary metal extraction by transforming mining and metallurgical wastes into valuable resources through recycling and reuse [41,42]. It seeks to transform environmental liabilities such as AMD and wastewater into valuable resources through advanced recycling and reuse strategies, focusing on South Africa’s mining sector, where AMD contaminates water sources [11,43].

Building on emerging innovations like sensor-based extraction, cyanide-free gold processing, and modular mine design, a critical assessment of waste valorization strategies that address key challenges such as land remediation, toxic by-products, water overconsumption, and post-closure liabilities that are currently prevalent in South Africa’s linear economy model is possible [31]. Furthermore, actionable approaches to unlock the economic potential of these waste streams, integrating sustainability drivers to foster systemic adoption of closed-loop systems that simultaneously recover resources, mitigate water pollution, and regenerate mining-affected ecosystems, can be proposed.

3. The Circular Economy Framework

This circular economy framework calls for a sustainable, integrated approach to waste management, emphasizing waste reduction and resource-oriented remediation over traditional ecological restoration. Successful implementation will require regulatory reform to distinguish between these approaches [44,45]. The South African mining sector can fully transition from a linear model to a circular economy by embedding waste prevention, valorization, and ecosystem regeneration into its operations [45]. Research shows that technologies based on closed-loop water recovery, thiosulfate gold leaching, sensor-based ore sorting, and re-mining of tailings can reduce environmental liabilities while unlocking new revenue streams [46,47,48]. The framework discusses the transition of the South African mining sector from a linear model to a circular economy, focusing on waste prevention, valorization, and ecosystem regeneration. Key strategies include the following: Design Out Waste: this covers implementation of closed-loop water systems for reuse and exploring alternative leaching methods, such as thiosulfate leaching, to mitigate environmental impacts [49,50]. Keep Materials in Use: Enhancing value through re-mining tailings and employing sensor-based ore-sorting technologies to optimize resource recovery [1,51]. Regenerate Systems: Integrating ecological rehabilitation, renewable energy solutions, and supportive policy frameworks to reduce environmental liabilities while improving economic resilience. These initiatives collectively aim to align South African mining practices with global best practices in the circular economy and fulfill emerging policy requirements.

3.1. Design Out Waste—Waste Prevention Through Smart Design

3.1.1. Water Recovery

The South African mining industry and power generation sectors consume close to 7% of the nation’s water. According to the National State of Water Report 2024 on water security, water use for power generation is much higher regionally, accounting for up to 37% of water use in the upper Olifants region in Mpumalanga province [52,53]. Based on total national water use of roughly 15 billion cubic meters (15 trillion liters) per year, about 3–5%, which equates to 450–750 billion liters per year, is used by the mining sector alone. The gold and platinum sectors are major consumers, with gold mining accounting for about 45% of total water consumption in the mining sector, or approximately 200–340 billion liters per year [52,53]. Gold mining is particularly resource-intensive; operations generate significant quantities of contaminated wastewater, with reports indicating 36 million cubic meters per year [54]. These contaminants include heavy metals, acids, and other toxic substances, posing risks to the environment and local communities.

Effective water management is essential for sustainable operations in the mining industry, with innovative technologies significantly contributing to reducing freshwater intake and waste [28]. The Council for Scientific and Industrial Research (CSIR) has developed advanced technologies for enhancing water recovery in mining processes. One such technology is the High-Density Sludge (HDS) process, as shown in Figure 9, which treats mine water to generate a thick sludge [53,55]. This process effectively concentrates metals and contaminants, improving water quality and enabling the recovery of valuable materials. Another key technology is Reverse Osmosis (RO), which uses a semi-permeable membrane to remove impurities from water [56]. By integrating RO systems, mining operations can reduce freshwater intake by 80–90%, conserving crucial water resources and diminishing the ecological impact of water extraction [57]. Anglo American has adopted the HDS process at one of its South African mining sites, which involves treating mine water to precipitate heavy metals and form a dense sludge that is either processed further or safely disposed of [52].

The procedure consists of several key steps: first, contaminated mine water is collected; chemicals are then added to facilitate the formation of metal hydroxides; subsequently, the precipitated sludge is thickened to enhance water recovery; and finally, the treated water is reused in mining operations, thereby further reducing reliance on freshwater sources [57,59].

Additionally, Anglo American’s platinum operations in Rustenburg can implement a zero-liquid discharge (ZLD) system shown in Figure 10, which relies on evaporation–crystallization, achieving a recovery rate of up to 95% [60,61]. This could reclaim around 5.2 million cubic meters of water each year with an initial investment of $10 million, resulting in a payback period of 3–5 years due to reduced sourcing costs. To further enhance the water treatment process, the installation of Reverse Osmosis (RO) units can be implemented to treat specific wastewater streams, such as cooling tower blowdown and concentrator process water [49,62]. These units can achieve a 90% recovery rate, amounting to approximately 3 million cubic meters.

Technologies such as Reverse Osmosis (RO) are utilized internationally, especially in Australia and Canada, where they achieve up to 90% water recovery [64,65]. Constructed wetlands from the UK and the USA provide a cost-effective natural filtration method [64,65]. These can be enhanced with advanced strategies such as zero-liquid discharge (ZLD) systems, which are highly effective in Chilean copper mines and achieve up to 95% water recovery, and bioremediation techniques used in Brazil that effectively reduce heavy metals [66]. A case study at Gold Fields’ South Deep mine in South Africa, which requires approximately 3 million cubic meters of water annually, indicates that implementing RO and bioremediation could potentially recover about 2.7 million cubic meters per year.

This could be initiated with a $2 million investment and a payback period of just 3 years, driven by savings from reduced water purchases. In addition, Anglo American’s platinum operations, which consume about 5.5 million cubic meters of water annually, could implement a ZLD system that would allow recovery of up to 5.2 million cubic meters, requiring a capital investment of $10 million but yielding annual savings of $1.5 million. Another technology is engineered systems that enhance detoxification efficiency using biofilm reactors and genetically engineered microorganisms (GEMs). This is where targeted bioremediation using microorganisms can also be used to detoxify heavy metals in mining water [67,68]. This process effectively detoxifies heavy metals from mining water by using bacteria, fungi, algae, and yeast. Key mechanisms include biosorption, in which metal ions bind to functional groups on biomass, such as algae or fungi, and bioaccumulation, which enables cells to actively transport metals into the cells using specialized proteins. Then, biomineralization follows, in which microbes induce the formation of insoluble minerals that trap metals and alter their oxidation state, making them less toxic or mobile through biotransformation. Extracellular polymeric substances (EPSs), which are polymers secreted by microbes, then bind metal cations, providing a protective barrier [69].

The main application of this process in mining water recovery focuses on the treatment of AMD using acidophilic microorganisms, such as Acidithiobacillus spp., in bioleaching processes to extract metals from ore. The key advantages of bioremediation over traditional physicochemical methods include lower operating costs due to the use of natural biomass, higher efficiency in removing metals from dilute solutions, and the generation of less secondary waste, resulting in smaller volumes of hazardous sludge [70]. Implementing these innovative water recovery technologies can demonstrate a commitment to sustainable practices in South Africa, which is increasingly important for stakeholders and communities affected by mining operations. By reducing operational costs associated with water procurement, mining companies can improve their economic viability in a competitive market. As regulations on water use and waste management become more stringent, these technologies facilitate compliance with environmental laws. In addition to economic benefits, implementing these technologies yields significant social, environmental, and regulatory benefits.

3.1.2. Sensor-Based Extraction

Modern mining innovations, such as sensor-based extraction, can significantly reduce waste generation and energy use while enabling cleaner mine closure and site repurposing [1,71]. Traditional mining involves blasting, crushing, and processing vast amounts of ore with little precision, resulting in excessive waste and energy consumption. Sensor-based ore sorting changes this by using X-ray fluorescence (XRF) and near-infrared (NIR) sensors to identify and separate valuable minerals from waste rock in real time [72].

Figure 11 depicts a logarithmic scale chart categorizing analytical techniques for materials characterization by sample size: nano (0.1 ppm to 10 ppm), micro (10 ppm to 100 ppm), and bulk (100 ppm to 100%). Techniques are color-coded by scale: green for nano (e.g., APT, TEM), blue for micro (e.g., SEM, SIMS), and red for bulk (e.g., PGNAA and PFTNA, XRF); insets detail electron microscopy methods (EDS, EELS). It shows how each tool probes material composition [73,74]. PGNAA shines in the bulk category, using neutron activation to instantly identify ore quality in large truckloads, rejecting waste before energy-intensive crushing, demonstrating its suitability for bulk ore sorting. Sensor-based ore sorting technology, such as Anglo American’s bulk ore sorting (BOS), represented in the Anglo American 2023 Annual Sustainability report, uses Prompt Gamma Neutron Activation Analysis (PGNAA) at the Mogalakwena platinum mine, and it has gained traction globally to preconcentrate heterogeneous ores, reducing energy and water demands early in processing [73,74].

In Australia, TOMRA’s XRT sorters at gold operations reject 30–50% waste, boosting grades by 20–40%, and BHP employs similar technology at copper sites for 15–25% throughput gains, while Newmont integrates XRF/XRT at Nevada gold mines, cutting milling energy by 15–20% [76,77]. These align with circular economy goals by minimizing tailings and emissions, as detailed in Coalition for Eco-Efficient Comminution (CEEC) studies on PGNAA heterogeneity analysis. The Witwatersrand goldfields and the Bushveld PGM deposits present significant opportunities for BOS adoption due to their low-grade (1–5 g/t gold) and geologically variable ore bodies [78,79]. These characteristics are comparable to those successfully addressed at Anglo American’s Mogalakwena platinum mine, where BOS using Prompt Gamma Neutron Activation Analysis (PGNAA) achieved a 20% reduction in energy use and a 17% reduction in water consumption [78,79]. By rejecting barren or low-density waste rock early in the process, BOS reduces the volume of material entering downstream grinding circuits. Such improvements are particularly relevant in South Africa’s resource-constrained environment.

Mining and energy account for approximately 7% of national water consumption, and operations face increasing scrutiny under the National State of Water Report 2024. Technologies such as PGNAA and X-ray Transmission (XRT) allow for dry, sensor-based separation, thereby avoiding water-intensive comminution processes [80]. In addition to reducing processing costs, this approach contributes to dust management and lowers tailings volumes. At an operational level, Harmony Gold’s Moab Khotsong could apply BOS in tailings retreatment circuits to upgrade residual gold resources historically estimated at over 400 tons, while reducing energy demand by approximately 20%, a meaningful advantage under Eskom load-shedding conditions [79,81]. Similarly, Sibanye-Stillwater’s Driefontein operation could benefit from early-stage rejection of PGM-gold waste, resulting in up to 17% water savings amid ongoing pressures on the Vaal River. Gold Fields’ South Deep may also extend mine life through a 15–25% uplift in grade on deep-level reefs, consistent with performance metrics reported for Mogalakwena [78,79]. Beyond cost reductions, BOS contributes to reducing the 60% tailings burden, supports the South African Circular Minerals and Metals Initiative (SACMMI) sustainability targets, and aligns with Anglo American’s Future Smart Mining™ strategy, which is aimed at long-term decarbonization and skills development.

Sensor-based ore sorting can be situated within the broader transition from Industry 4.0 to Industry 5.0. Industry 4.0 is characterized by fixed, automated sensing and separation, such as the Prompt Gamma Neutron Activation Analysis (PGNAA) and X-ray transmission (XRT) systems deployed at Mogalakwena and in Australian gold operations, whereas Industry 5.0 introduces adaptive, artificial-intelligence and machine learning decision systems that optimize sorting in real time across heterogeneous ore. AI-enabled Industry 5.0 configurations can improve resource utilization by around 30% and reduce carbon emissions by around 25% relative to Industry 4.0 automation. For South Africa’s low-grade, geologically variable ore bodies of 1–5 g/t gold in the Witwatersrand and complex PGM reefs in the Bushveld, a shift from fixed PGNAA/XRT sorting toward AI-adaptive, human-supervised sorting could further raise resource recovery and reduce upstream mineral waste, reinforcing the Design Out Waste principle while aligning with national decarbonization and skills-development objectives.

3.1.3. Modular Infrastructure Design

Modular infrastructure design complements BOS by enabling flexible, relocatable processing systems that reduce stranded assets and long-term closure liabilities. At Mogalakwena, Anglo American’s bulk ore sorting technology has reportedly improved recovery while reducing energy use by 30%, resulting in less waste reporting to tailings dams and higher-grade ore feed to concentrators [76]. Unlike fixed processing plants, modular units can be deployed closer to extraction points, reducing haulage, lowering energy consumption, and enabling phased expansion or relocation [82,83]. This is particularly relevant for South Africa’s PGM sector, where smaller or satellite deposits require cost-effective development pathways [84,85].

Technologies such as Coarse Particle Recovery (CPR) further enhance this approach by maintaining larger particle sizes during flotation, thereby reducing grinding requirements and water use by up to 40% [86]. In South Africa, where tailings management and water scarcity remain critical challenges, such reductions could significantly reduce both processing waste and slurry volumes [87]. From a circular economy perspective, modular design prevents the creation of stranded post-closure infrastructure. Prefabricated and transportable plants, developed by firms such as SENET and Appropriate Process Technologies (APT), enable rapid assembly, disassembly, and resale, reducing capital expenditure by 30–50% compared to permanent facilities [88,89]. These systems are particularly suited to short-life or satellite deposits and phased project expansions.

Sedibelo Platinum Mines provides a practical example through its Pilanesberg Platinum Mines (PPM) operations on the Bushveld’s western limb. Modular concentrators evaluated for satellite pits such as Tuschenkomst and Wilgespruit have enabled production scaling to approximately 120,000 (3402 kg) 4E PGM ounces annually, without R4–6 billion in greenfield capital expenditure [86]. The ability to relocate units to prospects such as the Mphahlele PGM project further demonstrates adaptability, while halving construction timelines (6–12 months) and lowering environmental footprints, thereby reducing long-term liabilities [90,91].

If replicated in operations such as Harmony Gold, Sibanye-Stillwater, and Gold Fields, modular systems could reduce capital costs by 20–30% for 1–5 Mt/a modules, particularly in tailings retreatment and deep-level reef projects [79]. In broader economic terms, modular circular infrastructure supports SACMMI’s 2040 sustainability objectives and aligns with Department of Science, Innovation, and Technology priorities, and the circular economy literature indicates potential waste reductions of up to 40% under adaptive, modular frameworks [92,93].

3.1.4. Coarse Particle Mining and In Situ Recovery

In situ mining dissolves minerals in place and pumps them to the surface rather than using open pits or underground tunnels [94]. A global example of this is Kazakhstan’s uranium mines, which use in situ mining to eliminate waste rock and reduce water use by 70% [95]. This drives the mining sector to adopt a Circular Economy approach within its system. Coarse Particle Flotation (CPF) technology has been deployed commercially at Newcrest Mining’s Cadia Valley operations in Australia, where it enabled 20% higher throughput and approximately 20% lower energy consumption by processing particles up to 600 µm, reducing the need for fine grinding while maintaining high gold and copper recoveries. This approach, utilizing fluidized bed reactors such as Eriez HydroFloat or FLSmidth’s coarseAIR™ (FLSmidth & Co. A/S, Copenhagen, Denmark) as shown in Figure 12, rejects gangue early, cutting comminution energy by 15–30% and reagent use by 10–25%, as demonstrated across global base metal and gold circuits. The HydroFloat Separator (Eriez Manufacturing Co., Erie, PA, USA) also rejects coarse tailings, thereby reducing the circulating load and increasing mill throughput.

Coarse Particle Flotation (CPF), particularly through technologies such as the HydroFloat system, represents a significant departure from conventional fine-particle flotation practices. Traditional flotation circuits typically require extensive grinding to liberate minerals to fine particle sizes before separation can occur [97,98]. In contrast, the HydroFloat system enables the recovery of valuable minerals at much coarser particle sizes, requiring only minimal hydrophobic surface expression to initiate separation. This capability allows valuable minerals to be recovered earlier in the comminution process, thereby avoiding unnecessary overgrinding. As a result, maximum recovery can be achieved at the coarsest technically feasible size, while a larger proportion of gangue material is rejected earlier in the circuit [97,98].

One of the principal operational implications of this approach is increased mill throughput. By rejecting coarse (+150 microns) tailings and recovering coarse-value particles, Coarse Particle Flotation (CPF) provides an opportunity to increase the flotation feed top particle size without compromising recovery [99,100]. This reduces the load on downstream grinding circuits, which are typically the most energy-intensive components of mineral processing plants. In practical terms, the implementation of HydroFloat systems allows only a smaller fraction of the feed to undergo fine grinding, thereby reducing overall energy consumption while simultaneously increasing milling capacity.

From a sustainability perspective, the ability to float coarse particles translates directly into lower electricity demand and improved tailings management. Reduced grinding intensity lowers power requirements and associated greenhouse gas emissions, while generating coarser reject material simplifies tailings management and deposition [101,102]. Coarser tailings are generally more stable, less prone to dust generation, and easier to dewater, contributing to improved environmental risk management. Comparable outcomes have been observed internationally; for example, Glencore’s Mount Isa zinc mine in Queensland, Australia, adopted CPF to enable coarser liberation, resulting in a reported 5–15% recovery uplift alongside reduced processing footprints, consistent with broader sustainability mandates [103,104].

In the South African context, CPF is particularly relevant given the geological and economic characteristics of the country’s ore bodies. The Witwatersrand goldfields are characterized by relatively low-grade ores, typically ranging between 1 and5 g/t, while the Bushveld Complex hosts extensive but energy-intensive Platinum Group Metal (PGM) deposits [26,105]. Under such conditions, maximizing recovery efficiency while minimizing processing costs is critical. CPF mirrors international successes such as the Cadia operation, where coarser grinding regimes (P80 150–600 µm) have reduced energy demand without compromising recovery on complex ores [79,106]. This is especially significant in South Africa, where electricity supply constraints from Eskom and the fact that mining and energy industries account for approximately 7% of national water use place pressure on resource-intensive processing systems [52].

Furthermore, with approximately 60% of mining waste currently disposed of in landfills and annual AMD remediation costs estimated at R12 billion, reducing the generation of fine slimes and unstable tailings is a strategic priority [34]. CPF contributes to this objective by decreasing the volume of finely ground material requiring long-term storage while improving concentrate grades. This is particularly relevant for heterogeneous historical dumps, which have experienced an 87% decline in gold production over time, where improving processing efficiency is essential for economic viability [29].

The integration of CPF in gold mining in South Africa represents a strategic opportunity to improve recovery efficiency while simultaneously reducing energy intensity and tailings generation. It enables the recovery of valuable minerals at particle sizes up to approximately 600 µm, reducing the need for energy-intensive fine grinding. CPF systems, including technologies such as HydroFloat and FLSmidth’s coarseAIR™, enable earlier-stage recovery and reduced overgrinding, translating into measurable operational savings [107]. In this context, operations such as Harmony Gold’s Moab Khotsong and Sibanye-Stillwater’s Driefontein can potentially deploy CPF technologies within their tailings retreatment or concentrator circuits. HydroFloat trials have demonstrated energy savings of approximately 20% through coarser particle processing, primarily due to reduced milling requirements [100,108].

For mature, deep-level South African gold mines, where energy costs constitute a significant share of operating expenditure, such reductions are relevant given ongoing electricity constraints and tariff increases [109]. Similarly, Gold Fields’ South Deep operation presents a strong case for CPF integration. The mine has already reported improved metallurgical performance through enhanced gravity concentration systems, resulting in a 24% quarter-on-quarter increase in production to 2246 kg (2.25 tons) of gold, based on their Q1 2025 operational updates. With annual production guidance of 8710 kg (8.71 tons) to 9488 kg (9.49 tons) and a reported 10% reduction in all-in sustaining costs (AISC) to approximately US$55.85 per gram, incremental efficiency gains through CPF could further consolidate operational improvements. CPF may complement existing centrifugal gravity recovery by enabling improved liberation control and minimizing losses in ultrafine or partially liberated fractions [79]. Benchmark data from FLSmidth’s coarseAIR™ technology indicate potential throughput increases and energy reductions of 15–30%, depending on ore characteristics and circuit configuration [110,111]. When extrapolated to the scale of South Africa’s mining industry, valued at approximately R470 billion, such efficiency improvements could translate into operational expenditure savings of R1–2 billion annually across large-scale operations [112,113]. While such estimates are indicative rather than site-specific, they highlight the macroeconomic relevance of processing innovation.

Beyond direct cost benefits, CPF adoption may also yield environmental advantages. Reduced grinding intensity lowers electricity demand and associated greenhouse gas emissions, aligning with national decarbonization objectives under South Africa’s science, innovation, and Technology frameworks. Additionally, improved recovery at coarser sizes can decrease the volume of fine tailings generated, potentially reducing tailings deposition by up to 30% under optimized conditions. This is particularly significant in regions such as the Vaal River basin, where legacy tailings and seepage continue to pose water-quality risks [114,115]. Overall, CPF should be viewed not merely as a processing upgrade but as part of a broader transition toward energy-efficient, water-conscious, and lower-waste mineral processing systems within South Africa’s gold industry. Its relevance lies in its ability to simultaneously support cost competitiveness, environmental compliance, and decarbonization objectives within a resource-constrained operating environment.

3.2. Keep Products and Materials in Use—Valorization of Mining Waste

3.2.1. AMD–AMD

Globally, coal mines are adopting advanced water management strategies such as membrane filtration in China, zero-liquid discharge systems in India, and passive treatment wetlands in the US and Europe. In South Africa, waste from gold, platinum, and coal mining has led to AMD (Figure 13), land degradation, and health hazards for surrounding communities, and AMD is considered one of the major environmental challenges facing the global mining industry [40,98].

The dots represent active mines producing AMD from coal, gold and platinum. The clusters show where AMD contamination is worst on the Eastern, Central and Western basins [87,116,117]. The eastern basin hosts gold mines (Witwatersrand Basin) and high-sulfide coal/platinum deposits, which generate extreme acidity when exposed to water [57,118].

The western basin, which is west of Johannesburg, hosts Anglo Gold Ashanti’s Savuka and Mponeng mines, and the Central Basin in the Johannesburg area, where legacy gold mines are located [2]. Other mines include Anglo Platinum mines in Northwest Rustenburg [119]. AMD from Eastern/Central Basin gold mines flows into the Klip River and into the Vaal Barrage, increasing the river’s salt load by 13% and contaminating urban water supplies [43]. In Northwest and Mpumalanga provinces, which cover the western basin, gold-uranium AMD from Randfontein seeps into the Crocodile River, while coal AMD in Mpumalanga pollutes the Olifants River, both threatening agriculture and cross-border water quality [87,120]. And lastly, gold, due to its pyrite-rich ores, is generated by abandoned gold mines that leak uncontrolled acidic drainage into critical rivers such as the Vaal River [121,122]. Gold is the most important precious metal in the world, with estimated reserves of 54,000 tons. After extraction, the raw material is processed [123]. The extraction and processing of gold are also associated with the generation of toxic substances and extensive water use. Chemical processing, or hydrometallurgy, is used to dissolve gold from ores [124].

Cyanide is the most widely used reagent in gold production processes, and it is highly toxic, posing safety hazards during transportation and use [125]. Though cyanide solutions are efficient, their toxicity makes the development of alternative reagents such as thiosulfate, halides, thiocyanide, and thiourea imperative [126,127]. If made commercially viable, these alternatives could ensure efficient gold dissolution, but without environmental risks, such as water pollution [128,129]. With the increasing number of water issues in South Africa, the current economic model (Linear Economy) used in mining needs revision [130,131]. These materials are processed and converted into products, and the waste generated in these processes is often poorly managed, leading to the environmental issues discussed. The key issues in mining using linear models are AMD, a major by-product of gold mining that pollutes water sources with toxic metals and sulfates, as well as mines shutting down, leaving behind unsafe land, contaminated water, and overconsumption of water without sufficient plans for recycling or remediation [132,133].

These sudden closures strain local economies and infrastructure and create long-term environmental liabilities that are unaccounted for, impacting future land development. The lack of incentives for waste management impedes innovation and sustainability. This model prioritizes profit and resource extraction over environmental stewardship [1]. The management of AMD has historically focused on neutralization and containment, typically through lime dosing and sludge disposal liabilities. While such approaches stabilize pH and reduce immediate toxicity, they do not recover value from contaminated water streams nor prevent long-term environmental liabilities [134,135]. In recent decades, mining jurisdictions have shifted toward resource recovery-based AMD management, aligning water treatment with circular economy principles. Instead of treating AMD solely as waste, advanced systems extract usable water and saleable by-products, thereby reducing environmental burdens while creating economic value [136].

In China’s Shanxi coalfields, Reverse Osmosis (RO) membrane filtration systems are deployed to treat mine-impacted water [137,138]. These systems use semi-permeable membranes under pressure to separate dissolved salts and contaminants from water molecules. As a result, approximately 85% of process water is recovered for reuse, while concentrated brines enable gypsum precipitation, which is subsequently used in cement production [137,138]. This approach demonstrates how AMD streams can be converted into secondary raw materials within industrial value chains. Similarly, in India, Coal India Limited has implemented zero-liquid discharge (ZLD) systems across multiple coal operations in Jharkhand [139,140] as presented in Table 1. This integrates membrane filtration, evaporation, and crystallization units to ensure that no liquid effluent is released into surrounding water bodies. Treated water is fully recycled back into operations, while sodium sulfate and other crystallized salts are recovered as by-products for commercial sale. By achieving water reuse rates approaching 95%, these plants illustrate how AMD treatment can transition from a compliance-driven cost center to a revenue-generating, water-secure system.

In the United States and Europe, nature-based and metallurgical recovery systems further exemplify this paradigm shift. At Colorado’s Summitville Mine, the U.S. Environmental Protection Agency has operated passive treatment wetlands that use sulfate-reducing bacteria to biologically precipitate heavy metals and increase pH levels. Over time, these constructed ecosystems gradually restore water quality without continuous chemical dosing, demonstrating long-term sustainability [141]. In Europe, the NEMO Horizon 2020 project advanced technologies for extracting metals and recovering sulfate salts from sulfidic tailings, achieving substantial reductions in tailings volume while recovering valuable materials [142,143,144]. These projects collectively illustrate the global evolution of AMD management toward circular resource recovery. The relevance of these approaches to South Africa is significant. The country’s 6.1 billion tons of tailings and extensive coal and gold mining legacy have resulted in AMD impacts affecting approximately 1.6 million people, particularly across Mpumalanga and Gauteng, with annual remediation costs estimated at R12 billion, placing considerable strain on public resources [43,117]. In Mpumalanga alone, where 63 collieries produce roughly 80% of national coal output, AMD contributes to high water stress in the upper Olifants catchment, a region already under severe hydrological pressure [87,120].

Adopting ZLD systems similar to those implemented in India could substantially reduce regional water withdrawals and limit contaminated discharge into sensitive river systems. Membrane-based treatment is also relevant for Limpopo’s Platinum Group Metal (PGM) operations, where AMD streams may contain recoverable metal fractions and the construction of wetlands and high-density sludge (HDS) systems [145,146]. These examples indicate that both engineered and nature-based AMD recovery solutions are technically feasible under South African conditions. The Mpumalanga AMD Management Framework and evolving water-use licensing directives emphasize stricter discharge standards and promote sulfate recovery for high-priority sites impacting the Vaal and Olifants river systems [147,148]. Such regulatory instruments create an enabling environment for circular AMD technologies by linking environmental compliance to resource efficiency. Furthermore, rehabilitated wetlands and restored catchments improve ecological resilience and community relations in regions heavily affected by legacy mining [133].

Table 1. International practices in coal mine water waste management.

Country/Region	Technology/Practices	Findings and Outcomes	Applicability to South Africa	References
China (Shanxi Province)	Membrane Bioreactor (MBR) + Reverse Osmosis (RO)	Hybrid MBR-RO systems achieve up to 90% mine water recycling, treating high-sulfate AMD (5000–15,000 mg/L). This indicates that most wastewater is cleaned and reused, even when it contains very high sulfate levels. NF-MBR + RO yields permeate conductivity <200 μS/cm from a feed of 10,000 μS/cm, with 3.3× lower RO fouling than UF-MBR. Indicates that the treated water is nearly free of salts, starting from very salty feedwater (10,000 μS/cm), and that the system clogs much less than older ultrafiltration methods, reducing maintenance and improving efficiency. The leftover gypsum mineral from treatment can be reused in making cement, turning waste into a useful material.	For Mpumalanga coalfields (63 collieries, 200 ML/d AMD to the Olifants River), hybrid MBR-RO could cut DWS compliance costs from R450/m3 to R250/m3 while recovering 85% of process water, directly mitigating priority pollution hotspots.	[127,149,150,151]
India (Jharkhand, Coal India Limited)	Zero Liquid Discharge (ZLD) with Evaporation–Crystallization	12 ZLD plants process 150 ML/d, achieving 100% wastewater reuse. Multi-effect evaporators recover sodium sulfate and achieve 95% volume reduction, 75% OPEX savings, and salt purity >98% in the chemical industries. The findings show that this process reuses all wastewater, recovers salts (sodium sulfate) as valuable by-products, reduces treatment costs, and minimizes discharge. Recovered salt is of high purity and can be sold to chemical industries.	Limpopo platinum mines could adopt ZLD to comply with the National Water Act Section 21 requirements. Recovery of MgSO4 from PGM-rich AMD demonstrated at Anglo Platinum Polokwane plant (90% recirculation). Supports equitable water allocation and revenue generation from by-products.	[53,152,153]
United States (Pennsylvania)	Constructed Wetlands and Passive Treatment	Vertical flow wetlands achieve 70% iron removal (>100 mg/L → <30 mg/L) and 60% acidity neutralization (pH 3.5 → 6.8) using sulfate-reducing bacteria over 25 years. Metal retention 85–95%. Costs $0.50–1.50/m3 versus $5–10/m3 for active treatment. Generates biodiversity corridors. It uses plants and bacteria to remove metals and reduce acidity, is low-cost, and creates a habitat suitable for abandoned mines. Magnesium sulfate (MgSO4), a by-product of PGM-rich AMD, can be sold, creating revenue and supporting water reuse.	Mpumalanga abandoned eMalahleni collieries (1200 sites) could implement wetlands 15 ML/d per site, creating ~200 low-skill jobs/ha. Supports DWS Priority 2 rehabilitation mandates and passive AMD remediation.	[154,155,156,157]
Australia (Mt Arthur, BHP)	Real-Time Sensor-Based Water Monitoring (IoT + SCADA)	Real-time pH/ORP/heavy metal monitoring ensures 98% regulatory compliance and 25% water reuse optimization. Predictive modeling reduced environmental incidents by 40%. These findings indicate that sensors track water quality in real time, ensure compliance, reduce spills, optimize water reuse, and lower fines.	Vaal River catchment mines could integrate DWS NAEIS with sensors to monitor AMD discharge, prevent fines (~R2 billion annually), and improve Minerals Council ESG reporting. Enhances compliance and proactive water management.	[158,159,160]
Europe (Germany–Ruhr Valley/Poland–Upper Silesia)	Mine Water District Heating and Industrial Reuse/ZLD-Crystallization	Germany: 50 ML/d neutralized mine water (15–20 °C) used for district heating (15 power plants), displacing 20,000 m3 municipal supply/day with 30% energy efficiency gains. Poland: ZLD-crystallization produces 25,000 tpa of NaCl, with a 95% volume reduction. The findings show that the treated mine water can be used for heating, cooling, and salt production, reducing freshwater use and cutting operational costs.	Mpumalanga’s 12 GW coal fleet could use treated AMD for cooling water, reducing regional water consumption (currently 37%) and cutting Eskom operating costs by ~R500 million/year. Enables industrial valorization of AMD while reducing freshwater abstraction.	[65,161,162,163]

Table 1. International practices in coal mine water waste management.

Country/Region	Technology/Practices	Findings and Outcomes	Applicability to South Africa	References
China (Shanxi Province)	Membrane Bioreactor (MBR) + Reverse Osmosis (RO)	Hybrid MBR-RO systems achieve up to 90% mine water recycling, treating high-sulfate AMD (5000–15,000 mg/L). This indicates that most wastewater is cleaned and reused, even when it contains very high sulfate levels. NF-MBR + RO yields permeate conductivity <200 μS/cm from a feed of 10,000 μS/cm, with 3.3× lower RO fouling than UF-MBR. Indicates that the treated water is nearly free of salts, starting from very salty feedwater (10,000 μS/cm), and that the system clogs much less than older ultrafiltration methods, reducing maintenance and improving efficiency. The leftover gypsum mineral from treatment can be reused in making cement, turning waste into a useful material.	For Mpumalanga coalfields (63 collieries, 200 ML/d AMD to the Olifants River), hybrid MBR-RO could cut DWS compliance costs from R450/m3 to R250/m3 while recovering 85% of process water, directly mitigating priority pollution hotspots.	[127,149,150,151]
India (Jharkhand, Coal India Limited)	Zero Liquid Discharge (ZLD) with Evaporation–Crystallization	12 ZLD plants process 150 ML/d, achieving 100% wastewater reuse. Multi-effect evaporators recover sodium sulfate and achieve 95% volume reduction, 75% OPEX savings, and salt purity >98% in the chemical industries. The findings show that this process reuses all wastewater, recovers salts (sodium sulfate) as valuable by-products, reduces treatment costs, and minimizes discharge. Recovered salt is of high purity and can be sold to chemical industries.	Limpopo platinum mines could adopt ZLD to comply with the National Water Act Section 21 requirements. Recovery of MgSO4 from PGM-rich AMD demonstrated at Anglo Platinum Polokwane plant (90% recirculation). Supports equitable water allocation and revenue generation from by-products.	[53,152,153]
United States (Pennsylvania)	Constructed Wetlands and Passive Treatment	Vertical flow wetlands achieve 70% iron removal (>100 mg/L → <30 mg/L) and 60% acidity neutralization (pH 3.5 → 6.8) using sulfate-reducing bacteria over 25 years. Metal retention 85–95%. Costs $0.50–1.50/m3 versus $5–10/m3 for active treatment. Generates biodiversity corridors. It uses plants and bacteria to remove metals and reduce acidity, is low-cost, and creates a habitat suitable for abandoned mines. Magnesium sulfate (MgSO4), a by-product of PGM-rich AMD, can be sold, creating revenue and supporting water reuse.	Mpumalanga abandoned eMalahleni collieries (1200 sites) could implement wetlands 15 ML/d per site, creating ~200 low-skill jobs/ha. Supports DWS Priority 2 rehabilitation mandates and passive AMD remediation.	[154,155,156,157]
Australia (Mt Arthur, BHP)	Real-Time Sensor-Based Water Monitoring (IoT + SCADA)	Real-time pH/ORP/heavy metal monitoring ensures 98% regulatory compliance and 25% water reuse optimization. Predictive modeling reduced environmental incidents by 40%. These findings indicate that sensors track water quality in real time, ensure compliance, reduce spills, optimize water reuse, and lower fines.	Vaal River catchment mines could integrate DWS NAEIS with sensors to monitor AMD discharge, prevent fines (~R2 billion annually), and improve Minerals Council ESG reporting. Enhances compliance and proactive water management.	[158,159,160]
Europe (Germany–Ruhr Valley/Poland–Upper Silesia)	Mine Water District Heating and Industrial Reuse/ZLD-Crystallization	Germany: 50 ML/d neutralized mine water (15–20 °C) used for district heating (15 power plants), displacing 20,000 m3 municipal supply/day with 30% energy efficiency gains. Poland: ZLD-crystallization produces 25,000 tpa of NaCl, with a 95% volume reduction. The findings show that the treated mine water can be used for heating, cooling, and salt production, reducing freshwater use and cutting operational costs.	Mpumalanga’s 12 GW coal fleet could use treated AMD for cooling water, reducing regional water consumption (currently 37%) and cutting Eskom operating costs by ~R500 million/year. Enables industrial valorization of AMD while reducing freshwater abstraction.	[65,161,162,163]

The international cases differ in their technical parameters, and comparing them on a consistent set of criteria, such as water recovery, cost, by-product valorization, and suitability for South African conditions, clarifies which approaches transfer best. For water recovery, the engineered systems are strongest. The Indian Zero-liquid discharge plants achieve 95–100% reuse with 95% volume reduction [53,152,153], and the Chinese MBR–RO systems recover 90% of mine water while reducing brine conductivity from 10,000 to below 200 µS/cm [127,149,150,151]. Passive systems recover less but perform reliably, with the Pennsylvania wetlands achieving 70% iron removal and 85–95% metal retention [154,155,156,157]. The Australian case is not directly comparable on this axis, as it is a monitoring and compliance technology rather than a treatment process and is better assessed by its 98% regulatory compliance and 40% incident reduction outcomes [158,159,160].

For cost, the trade-off is between capital and operating expenditure. Passive wetlands are the cheapest to operate at $0.50–1.50/m³, compared with $5–10/m³ for active treatment, making them well suited to abandoned sites with no operating budget [154,155,156,157]. Zero-liquid discharge incurs the highest capital cost but becomes operating cost-positive through salt sales and avoided discharge penalties [53,152,153], whereas the Chinese membrane route is reported to have lower compliance costs of R450–R250/m³ [127,149,150,151]. By-product valorization reinforces this picture, where ZLD recovers sodium sulfate at over 98% purity [53,152,153]. The membrane systems convert brine into gypsum for cement [127,149,150,151], and the European model extracts both sodium chloride (25,000 tons per annum) and low-grade heat for district heating [65,161,162,163]. These recovered streams are what shift AMD treatment from a pure cost to a partial revenue source.

Translating this into South African conditions, no single approach dominates; suitability depends on site status. Membrane and ZLD systems are best matched to active, well-resourced operations such as the Mpumalanga coalfields and Limpopo platinum mines, where discharge can be eliminated, and by-products can be sold [53,127,149,150,151,152,153]. Passive wetlands are a realistic option for the large inventory of abandoned and ownerless collieries around eMalahleni, where low operating costs matter more than maximum recovery [154,155,156,157,158]. Real-time monitoring is a complementary layer rather than an alternative, applicable across active catchment operations such as the Vaal [158,159,160,161,162]. The European mine water reuse and district-heating model offers a route to valorizing treated AMD as cooling water for Mpumalanga’s coal fleet [65,161,162,163]. Therefore, the conclusion is that engineered recovery for active mines can occur with a responsible operator and passive treatment for legacy sites, with the choice driven by site ownership, water-quality targets, and the availability of a market for recovered by-products.

In South Africa, the adoption of these technologies is governed by the National Water Act 36 of 1998 (NWA), under which the abstraction, treatment, discharge, and disposal of mine-impacted water are licensable water uses. AMD management engages the following water uses defined in Section 21 at once: the taking of water (s21(a)), the discharge of waste or water containing waste (s21(f)), the disposal of waste in a manner that may detrimentally affect a water resource (s21(g)), and for dewatering operations, the removal of underground water for the safe continuation of mining (s21(j)). Each requires a Water Use License (WUL) and compliance with the prescribed discharge standards and with the mining-specific regulations under Government Notice R704, which set the reasonable measures required to protect water resources from mining activities.

Assessed against this framework, the four international approaches differ in how readily they can be licensed. The Indian zero-liquid discharge model offers the strongest alignment, because eliminating liquid effluent removes the Section 21(f) discharge trigger altogether and converts the regulated waste stream into saleable sodium sulfate, leaving only solid-residue handling to be authorized. The Chinese membrane and RO systems reduce discharge volumes by 85–90% and convert brine into gypsum for cement, supporting the duty-of-care and pollution-prevention provisions of Section 19 and the resource-recovery emphasis of recent South African water policy, although the residual brine and sludge still require licensed disposal [11]. Passive constructed wetlands are particularly suited to the country’s large inventory of derelict and ownerless collieries, where no responsible party exists, and the state carries the rehabilitation burden, since their low operating cost and self-sustaining operation fit unattended legacy sites; their limitation is the need for long-term monitoring to hold treated water within discharge limits [164]. The European mine water reuse and district-heating model aligns with the beneficial-use authorizations that South African licensing increasingly encourages for high-priority catchments such as the Vaal and Olifants. Across all four, regulatory compatibility ultimately rests on securing a WUL and meeting GN704 standards [165], so the technologies that internalize their waste streams, ZLD, and membrane recovery are the most readily authorized under current South African law.

In summary, the global transition from passive AMD neutralization to integrated resource recovery provides a critical contextual foundation for South Africa’s circular mining strategy. Rather than treating AMD solely as an environmental burden, emerging technologies demonstrate that contaminated mine water can be converted into reusable water, saleable materials, and rehabilitated ecosystems. Within the broader framework of sustainable mine waste valorization, advanced AMD management is a core pillar of “Valorization of Mining Waste,” preventing long-term pollution while retaining resource value within the mining system.

3.2.2. Re-Mining of Tailings

South Africa’s mining legacy has generated vast quantities of tailings, waste rock, and scrap metal that can be repositioned from environmental liabilities to secondary resource streams within a circular economy framework, as shown in Figure 14. Recycling mine tailings offers transformative potential for the resource-intensive construction sector [157].

Figure 14 illustrates a closed-loop valorization framework for mine tailings, transforming environmental liabilities into high-value construction inputs representing a cornerstone of circular economy principles for South African mining waste management. Unprocessed mine tailings can be diversified into six primary streams through particle-size classification and chemical activation [157].

At the center of the diagram is mine tailings from the primary resource base. The inner ring illustrates how these tailings are separated into distinct fractions by particle-size classification and chemical activation, each suited to a specific construction application. Rather than treating tailings as homogeneous waste, this recognizes their mineralogical and granulometric diversity as an industrial advantage [166]. The coarse fraction (>4.75 mm) is repurposed as a coarse aggregate, suitable for concrete and road base applications in accordance with South African National Standard 1083 [167]. The medium sand fraction (0.425–4.75 mm) is used as a fine aggregate, compliant with SANS 1200 [168] for mortar and concrete works. The silt-sized fraction (75–425 µm) is redirected into clinker raw material, partially substituting for limestone and silica in Portland cement kilns at 15–25% replacement ratios, thereby reducing virgin quarry demand and kiln emissions [169]. The ultrafine powder (<75 µm) serves as a tailings powder precursor, chemically activated to function as a geopolymer binder, as validated in recent research by Zhang et al. [170]. Fine sands are further refined into tailings sand for masonry mortar and plaster applications, achieving water absorption levels below 12%. In parallel, specialized streams enable higher-value outputs such as lightweight aggregates for autoclaved cellular concrete blocks and iron oxide pigments derived from hematite-rich tailings for use in paints and ceramics.

The outer circular arrows in the diagram emphasize bidirectional material flows and industrial symbiosis. Waste rock can supplement clinker production, while construction activities may return process residues or leachate for further treatment, reinforcing total mass balance principles [157]. This cascading utilization approach enables up to 95% material recovery from South Africa’s estimated 6.1 billion tons of tailings, transforming disposal costs of approximately R120 per ton into product revenues of R450–R800 per ton.

The model is supported by emerging regulatory frameworks such as the South African Bureau of Standards (SABS) SANS 3001 [171], and is reinforced by commercial precedents, including Kumba Iron Ore’s aggregate repurposing program. This framework can also deliver multiple co-benefits, including a 70–80% reduction in embodied carbon compared to virgin materials, progressive land remediation across approximately 400 km² of tailings facilities, and the elimination of long-term AMD precursors through systematic material recovery [6,158]. Each tailings fraction suits a particular product, performance range, and end-use standard.

Table 2. Valorization pathways for mine tailings by particle fraction, with performance, applicable standards, and environmental benefit.

Tailings Fraction	Valorization Product	Typical Performance	Applicable Standard	Environmental Benefit	Ref
Coarse (>4.75 mm)	Coarse aggregate (concrete, road base, pavement layers)	Substitutes virgin aggregate in bound and unbound pavement layers	SANS 1083 [172]	Reduces virgin-stone quarrying	[169,173]
Medium sand (0.425–4.75 mm)	Fine aggregate (concrete, mortar)	~10–30% river-sand replacement without strength loss	SANS 1200	Reduces river-sand extraction	[158,169]
Silt (75–425 µm)	Clinker raw material (Portland cement)	15–25% limestone/silica substitution in the kiln	Blended-cement specifications	Lowers kiln emissions and virgin quarry demand	[169]
Ultrafine (<75 µm)	Geopolymer (alkali-activated) binder	Chemically activated binder; 10–80 MPa; ~80% lower embodied carbon	No dedicated SANS standard yet (standardization gap—see Section 5)	~70–80% lower embodied carbon vs. Portland cement	[158,170,173,174]
Fine sand	Masonry mortar and plaster	Water absorption below 12%	SANS 1215 [175] (masonry units)	Construction-grade reuse	[169]
Specialized streams	Lightweight aggregate; iron-oxide pigment	Autoclaved cellular concrete blocks; pigments from hematite-rich tailings	Product-specific	Higher-value outputs from waste	[169]

consolidates these valorization routes by particle fraction, summarizing the product, typical performance, applicable standard, and environmental benefit for each, and indicating whether a recognized standard already exists and where one is still absent.

The table shows that tailings are a graded resource whose value depends on matching each fraction to the appropriate product, such as coarser fractions to aggregates and finer fractions to cementitious and geopolymer binders. The one consistent gap is the standardization of higher-value geopolymer products, which currently lack a dedicated SANS specification and are addressed in the policy recommendations of Section 5. This fraction-dependent logic is examined in more detail in Figure 15.

Figure 15 shows a multi-scale framework for the classification and characterization of mine tailings for construction applications [157]. Figure 15a presents a hierarchical grain classification based on particle size, which impacts mechanical strength and chemical reactivity, suggesting that coarser fractions are suitable for road base and concrete, while finer fractions are better for binder replacement [157,176]. Figure 15b links particle size with specific surface area, showing that ultrafine tailings can be high-performing in concrete applications [177]. Figure 15c illustrates the compositional diversity of tailings from various ores, which affects bonding behavior in cementitious matrices [178]. Overall, the figures emphasize that mine tailings should be viewed as engineered mineral resources rather than waste, with their performance dependent on careful processing and suitability for specific construction uses, supporting circular economy strategies in the sector.

Researchers in South Africa demonstrated that gold and coal tailings can be alkali-activated to produce geopolymer bricks containing 70–90% waste material, achieving compressive strengths of 15–25 MPa, comparable to conventional clay bricks, while reducing embodied carbon emissions by approximately 80% due to the elimination of high-temperature kiln firing [179,180,181]. Parallel initiatives demonstrate that waste rock can be crushed and repurposed into construction aggregates, as evidenced by Kumba Iron Ore at Sishen Mine, which converts approximately 12 Mtpa into G1–G5 aggregates for road and rail infrastructure, generating substantial revenue while eliminating disposal costs and reducing reliance on virgin quarry materials [182,183]. At a national scale, an estimated 450 Mtpa of waste rock could significantly offset aggregate imports and support infrastructure expansion [113,183].

According to a report performed by the United States Geological Survey, the tailings dams of the Witwatersrand were estimated to contain over 400 tons of residual gold [87,184]. Companies like DRDGOLD and Sibanye-Stillwater have proven the profitability of tailings retreatment. DRDGOLD is a South African gold mining company specializing in the retreatment of surface gold tailings. The company’s Ergo operation processes old tailings to produce over 140,000 ounces (3968.93 kg) of gold annually with a significantly lower environmental footprint than conventional mining [2].

Figure 16 illustrates the process that DRDGOLDuses to extract value from historical mining waste. The operation begins with hydro-mining discarded tailings, creating a slurry that is pumped to a processing plant. In this method, gold is recovered through an automated process. The remaining tailings are then re-deposited in a modern, engineered facility designed to contemporary environmental standards, significantly reducing the long-term environmental liability compared to the original dumps. This process exemplifies a key circular economy principle in mining: transforming waste liabilities into resources while improving environmental outcomes.

South Africa’s coal fly ash and Platinum Group Metal (PGM) tailings are significant sources of Critical Raw Materials (CRMs) like vanadium, scandium, and rare earth elements (REEs). A 2022 Council for Scientific and Industrial Research (CSIR) study found that coal fly ash from Mpumalanga, as shown in Figure 17, contains REE concentrations of over 800 ppm, making extraction economically viable and strategically important for the global energy transition [186,187].

A study at the University of Western Cape on coal fly ash during enrichment processes demonstrated the potential of coal fly ash (CFA) as a viable alternative source of REEs through simple processing steps, such as wet magnetic separation and, in particular, zeolitization to selectively recover these REEs [189]. The study also demonstrated that countries that produce large quantities of CFA as a waste by-product of coal combustion may develop this processing technology for the recovery of REEs from alternative resources, as well as to produce REEs for the global market [189]. Collectively, these valorization pathways demonstrate that mine-derived wastes can be technologically validated, economically viable, and policy-aligned resources that can reduce environmental footprints, generate employment, and strengthen domestic industrial supply chains.

Theoretical recovery yields from tailings must be tempered by mineralogical partitioning. Weathered, semi-arid South African tailings commonly develop secondary mineral phases, notably jarosite and iron oxyhydroxides, that physically encapsulate target metals. Because these phases must first be decomposed before the sequestered metals become accessible, they impose a rate-limiting step that slows leaching kinetics and depresses recoverable yields relative to idealized projections. For jarosite-type compounds, the kinetics and ultimate extraction of the encapsulated metals depend strongly on prior decomposition and on the lixiviant selected [190], and the detoxification and reprocessing of the resulting residues impose additional treatment costs [158]. The economic feasibility of secondary critical-raw-material recovery from such tailings therefore depends on mineralogically informed flowsheets rather than on bulk-grade assumptions. Figures such as the residual gold in Witwatersrand tailings and the rare-earth grade of coal fly ash should therefore be read as mineral-constrained, upper-bound estimates.

3.3. Regenerate Natural Systems

The principle of regenerating natural systems in post-mining landscapes has evolved from basic rehabilitation compliance to multifunctional ecological restoration that delivers measurable environmental and economic value [191]. International benchmarks demonstrate that large-scale mine closure can successfully transition degraded land into productive ecosystems [191,192]. Ranger Mine Closure Plan 2023 reported that Australia’s Ranger Uranium Mine, which ceased operations in 2021, is currently undergoing a multi-billion-dollar rehabilitation to transform over 1000 ha of the site, including tailings areas, into a self-sustaining native savanna woodland [193]. This process involves revegetation with 95% native species to match the surrounding Kakadu National Park, heavily incorporating Indigenous knowledge to restore the ecosystem with a 12-year timeline. The key aspects of this rehabilitation include re-establishing a self-sustaining ecosystem like the surrounding environment by utilizing rock structures and specific plant species to create varied habitats.

The Diavik Diamond Mine in Canada’s Northwest Territories is implementing community-led reclamation, including filling kimberlite voids and revegetating containment areas. Operating a 9.2 MW wind farm since 2012, the site added a 6600-panel solar farm in 2024 to further reduce diesel reliance by 1 million liters annually [194]. The mine is undergoing progressive reclamation to close the site during the first half of 2026, including the disposal of processed kimberlite into mine workings (A418 and A154) and revegetation efforts. These initiatives aim to significantly reduce emissions and support sustainable closure, as highlighted in reports from Natural Resources Canada and Rio Tinto 2025 [195,196]. Reclamation plans involve collaborating with local communities, including the Yellowknives Dene First Nation, to ensure traditional knowledge is used in site monitoring.

In South Africa, similar regenerative transitions are emerging. The Kimberley Big Hole demonstrates post-mining land-use conversion into tourism and heritage infrastructure, while recent initiatives at Cullinan indicate a shift toward eco-tourism–based rehabilitation models [197,198]. Importantly, the 2024 Department of Forestry, Fisheries, and the Environment (DFFE) Mine Environmental Management Guidelines formalize this trajectory by mandating measurable biodiversity uplift, effectively creating a regulatory driver for large-scale tailings repurposing. This policy context signals the emergence of a structured land repurposing market aligned with national sustainability goals.

Agroforestry restoration using spekboom (Portulacaria afra) has emerged as a scientifically validated, nature-based solution for rehabilitating degraded land in semi-arid regions, particularly in the Eastern Cape. This approach is effective for repairing ecosystems damaged by overgrazing and agriculture and sequesters significant amounts of carbon, often rivaling tropical forests in efficiency [199,200]. Spekboom thrives in dry, hot climates and is highly effective at stabilizing soil, reducing water runoff, and preventing erosion, which are crucial for reclaiming arid, degraded landscapes. It is recognized as one of the best carbon-sequestering plants in the world, with the potential to store large amounts of CO₂ both in the plant and in the soil. Rehabilitation involves planting spekboom truncheons, creating an environment that allows other plant species to re-establish, thereby accelerating biodiversity recovery [201]. The Subtropical Thicket Restoration Program (STRP), initiated in 2004, has demonstrated the success of this method over thousands of hectares, and it is now recognized by the United Nations (UN) as a World Restoration Flagship.

The application of spekboom restoration is also suitable for semi-arid mining regions such as the Karoo, as it can rehabilitate degraded land by stabilizing mining spoils, dump sites, and tailings dams. The high rate of leaf litter from spekboom rapidly builds up soil organic carbon, and the massive scale of carbon storage enables the generation of carbon credits, providing a self-sustaining funding mechanism for long-term restoration projects [200,202]. The scalability of spekboom restoration across Bushveld PGM voids positions it as a strategic climate-mitigation and geotechnical stabilization tool; these can show that ecological rehabilitation can generate quantifiable carbon credits while reducing slope failure risk and restoring ecosystem services [203].

Phytoremediation further complements these strategies by enabling in situ remediation of heavy metal-contaminated soils. South African research institutions have validated indigenous hyperaccumulator species capable of reducing nickel, cadmium, arsenic, and particulate matter by significant amounts [204]. Some species demonstrate hyperaccumulation thresholds sufficient for seasonal soil cleanup, while biomass valorization pathways create additional economic streams [204]. This model exemplifies regenerative design by coupling ecological restoration with productive land use.

Munyengabe and other researchers [205] performed a study to evaluate Helichrysum splendidum, a native South African perennial, for the rehabilitation of coal fly ash dumps from Eskom’s Hendrina Power Station in Mpumalanga, where coal fly ash (CFA) has created barren landscapes contaminated with heavy metals in air, water, and soil. In 6-month pot trials, the species demonstrated strong growth in CFA substrates despite lower CO₂ assimilation, producing greater biomass than controls. Phytoremediation efficiency ranged between 18 and 57% trace metal removal from soil, with translocation factor (TF) > 1 for multiple metals, indicating active transport of contaminants to shoots, and Bioconcentration Factor (BCF) > 1, confirming hyperaccumulation capability. Mechanistically, roots immobilize pollutants while shoots enable harvest and removal [205]. The approach is scalable, with planting densities of 10,000/ha on eMalahleni dumps and harvested biomass valorized for bioenergy at 12 GJ/t. In practical terms, Helichrysum splendidum functions as a resilient native phytoremediator that extracts heavy metals from toxic coal ash into harvestable biomass, enabling cyclical removal and progressive land stabilization for eventual safe agricultural reuse.

In another study, Chrysopogon zizanioides (vetiver grass) was evaluated, amended with compost (0–60%) and Moringa leaf extract (MLE) biostimulant for rehabilitation of Witwatersrand gold tailings storage facilities (TSFs) and footprint areas contaminated with Arsenic (As), Chromium (Cr), Copper (Cu), Lead (Pb), and Nickel (Ni) exceeding soil screening values [197]. In 16-week greenhouse trials, 30% compost plus commercial MLE produced the highest biomass (roots/leaves/tillers), while 60% compost maximized vegetative growth but reduced metal uptake due to the immobilization effect; vetiver showed 0% survival without compost. Field trials at TSF 4 and adjacent footprint areas during the rainy season (2021) confirmed that 30% compost plus weekly MLE yielded the highest leaf length, tiller density, and biomass, with phytostabilization evidenced by roots binding metals and preventing leaching. Mechanistically, MLE (natural growth hormones) combined with compost (nutrients and microbial enhancement) stimulates vetiver’s 3–5 m deep root system, improving slope stabilization and metal binding. The findings offer a cost-effective solution that delivers a triple benefit of metal stabilization, erosion control, and biomass production for bioenergy. The model is scalable to 10,000 ha/year coverage across Harmony, Sibanye, and Gold Fields operations, with Witwatersrand field validation confirming real-world efficacy [206]. This study shows that adding 30% compost and moringa leaf spray to vetiver grass results in 3 times better growth on toxic gold mine tailings while locking heavy metals (As, Cr, Cu, Pb) in its deep roots. What this means is that mines can stabilize harmful tailings dumps cost-effectively (R100/ha vs. R450/m³ for chemical treatment), stop metal pollution from leaching into rivers, and harvest grass biomass for energy, all using local organic waste, thereby converting South Africa’s gold tailings inventory from an environmental liability into stable, productive land.

Researchers in Pakistan investigated the combined application of biochar (pyrolyzed biomass) and processed fly ash in coal mining-contaminated soils high in cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn), cultivated with maize, demonstrating a synergistic remediation effect [207,208]. The biochar and processed fly ash combination increased soil pH and reduced heavy metal bioavailability by 60–80%, shifting metals from bioavailable to stable fractions. Metal uptake in maize declined by 50–70%, rendering grain safe for consumption, while biomass yields increased by 25–40%. The synergistic mechanism showed that combined amendments outperformed individual treatments, with processed fly ash providing stabilization while biochar provided adsorption capacity [207,208]. Translating these findings to South Africa, the approach is directly applicable to Mpumalanga through the use of Eskom coal fly ash combined with biochar derived from mine wood waste, stabilizing As, Cr, and Pb across Witbank dumps and enabling maize cultivation to support 1.6 M people near the dumps [209]. The intervention is cost-competitive at R200/ha compared to R450/m³ chemical treatment, scalable to 10,000 ha/year, and circular in design by converting two waste streams, ash and biomass, into a functional soil amendment which provides a total circular remediation pathway capable of detoxifying tailings, supporting safe food production, and contributing toward the elimination of AMD liabilities. Overall, the convergence of ecological science, engineered treatment systems, policy mandates, and market-based incentives demonstrates that mine rehabilitation can transition from compliance-driven remediation toward integrated landscape regeneration.

While this stabilization mechanism is well demonstrated, there is a distinction to it in the South African context. The biochar-processed fly ash study reported by researchers demonstrates safety by immobilizing bioavailable heavy metals through pH adjustment, a mechanism that aligns with the metal-dominated contamination profile of the Pakistani soils studied (Munir et al., 2020 [209]). South African coal fly ash carries naturally occurring radionuclides, an additional contaminant class that immobilization does not resolve. Combustion does not destroy the uranium and thorium present in the parent coal; it concentrates them in the residual ash. Mpumalanga feed coal, with a uranium content of about 2.24 mg/kg and an ash yield near 25%, yields fly ash with a uranium concentration of approximately 9 mg/kg. The uranium and thorium in South African coals exceed the world averages of 1.9 and 3.2 mg/kg, respectively [210]. South African fly ash is therefore a Naturally Occurring Radioactive Material (NORM), with the elevated radon exposures documented near coal residues in eMalahleni [211].

The implication for food is that raising soil pH lowers the bioavailability of cationic metals such as Cd, Pb, and Zn, thereby reducing metal uptake in maize; however, the same chemistry does not neutralize radionuclides, which persist in the substrate and can remobilize if pH decreases over time. A “grain-safe” conclusion drawn from a Pakistani trial on chemically and radiologically different ash cannot, on this basis alone, be carried over. Demonstrating food safety on South African fly ash-amended land would require site-specific determination of bioconcentration and translocation factors for the actual ash used, together with a radiological dose assessment for the uranium and thorium nuclides against South African soil screening values and public dose limits. The defensible role for coal fly ash in South African land regeneration is non-food phytostabilization and the progressive rehabilitation of ash dumps using metal-tolerant indigenous species, as demonstrated for Helichrysum splendidum on the Hendrina and eMalahleni dumps [25,207], with harvested biomass directed to bioenergy rather than the food chain. This preserves the circular-economy gain of converting two waste streams into a functional, land-stabilizing amendment while removing the food-safety and radiological-exposure pathways that the Pakistani study does not account for. The viability of coupling land restoration with community food security depends not only on agronomic feasibility but also on the availability of enabling financial mechanisms. Improving access to credit, risk management, and market connectivity can strengthen the resilience of smallholders and agribusinesses, and such instruments may help finance and de-risk community participation in post-mining land-restoration schemes [212].

4. Techno-Economic Feasibility and Commercial Readiness

The technologies reviewed above are technically demonstrated, but their full implementation and adoption depend on whether they are commercially viable under prevailing South African economic conditions. As was presented by the Department of Mineral and Petroleum Resources, the sector operates on thin and contracting margins where mining contributed 6.1% of nominal GDP in 2024, down from 6.3% in 2023, and profitability remained constrained by subdued commodity prices and rising operating costs, even as the end of load-shedding from March 2024 eased. Against this backdrop, capital-intensive circular technologies will not be adopted on environmental merit alone; their capital expenditure (CAPEX), operating expenditure (OPEX), compatibility with existing processing circuits, and the market acceptance of their products must each be critically assessed.

For water recovery, the economic case is comparatively mature, as systems integrate with existing water circuits without disrupting the metallurgical flowsheet. Reverse Osmosis (RO) can reduce freshwater intake by 80–90%, and a modeled RO-plus-bioremediation configuration at Gold Fields’ South Deep (≈3 million m³/yr demand) recovers about 2.7 million m³/yr for an estimated US$2 million capital outlay with a three-year payback. Zero-liquid discharge (ZLD) reaches up to 95% recovery but is markedly more capital-intensive. An Anglo American platinum application (≈5.5 million m³/yr) is estimated to cost US$10 million in capital, against US$1.5 million/yr in savings, with a longer payback and a higher energy burden from evaporation–crystallization. The principal economic shift comes from converting AMD into saleable by-products, such as gypsum and sodium sulfate, which offsets operating costs when a by-product market exists [43].

Sensor-based and coarse-particle technologies present a different feasibility profile, in which compatibility with the existing comminution circuit is the binding constraint rather than capital cost. Bulk ore sorting (BOS) and X-ray transmission (XRT) are comparatively low-risk where ore heterogeneity is high, delivering 15–25% throughput or grade gains, but they must be installed upstream of the grinding circuit, requiring physical reconfiguration of the plant’s front end. Coarse Particle Flotation (CPF) using HydroFloat or coarseAIR units offers 15–30% energy savings by rejecting gangue at coarser sizes, but likewise demands flowsheet modification and, in Platinum Group Metal applications, remains at demonstration rather than full commercial scale. Retrofit cost and circuit disruption, rather than the technology itself, therefore govern uptake.

For tailings valorization, technical performance is established, but market acceptance is the decisive variable. Alkali-activated geopolymer products manufactured from gold and coal tailings achieve compressive strengths of 15–25 MPa with roughly 80% lower embodied carbon than Portland-cement equivalents. These figures are consistent with the wider mine-tailings geopolymer literature, which reports 10–80 MPa and 30–50% energy savings relative to ordinary Portland cement [173]. The barrier is commercial adoption; secondary construction products require certification to South African National Standards (such as SANS 1083 and SANS 3001) and secured offtake agreements before contractors and regulators will specify them, while recovered salts and critical metals similarly depend on an established buyer. Without standardization and guaranteed demand, valorized products remain stranded regardless of their technical merit.

5. Policy Recommendations and Implementation Roadmap

The preceding analysis shows that the technical and economic foundations for circular mining exist, but that uptake is constrained by the absence of an enabling policy and a clear implementation sequence. International practice indicates that targeted government intervention is the decisive lever in converting circular potential into commercial activity, and South Africa has already begun to move in this direction. The Critical Minerals and Metals Strategy approved by the cabinet in 2025 embraces circular-economy measures, including reclaiming tailings and extracting value from secondary sources such as rare earth-bearing coal fly ash, while the accompanying draft Mineral Resources Development Bill of 2025 proposes to regulate historic tailings. These instruments provide a domestic platform, and on top of more specific, internationally benchmarked measures, can be sequenced. Drawing on precedents from the European Union, the United States, and Australia, a phased roadmap is proposed in

Table 3. Phased implementation roadmap for a circular mining economy in South Africa, with lead actors and international policy precedent.

Phase (Horizon)	Key Actions, Milestones and Policy Instruments	Lead Actors	International Precedent and Policy Basis	References
1. Foundation (0–3 years)	Pilot BOS, RO/ZLD, and CPF units; baseline tailings and fly ash characterization (mineralogy, NORM); Water Use License applications under the National Water Act; begin drafting national tailings-valorization standards	Operators + research institutions (CSIR, universities) + SABS	EU Critical Raw Materials Act (2024) sets binding standardization and a 25% recycling target for strategic raw materials by 2030; SA Critical Minerals and Metals Strategy (2025) commits to tailings reclamation	[213,214]
2. Scale-up (3–7 years)	Full-scale water recovery and tailings reprocessing; finalize tailings-product standards (SANS 1083, 1200, 3001); introduce production incentives (tax credits, royalty relief) for secondary recovery; government offtake/procurement of certified tailings products; establish carbon-credit MRV system	Operators + SABS + DMRE + DFFE + National Treasury	US production tax credits and US$1.2 billion interior commitment to tailings valorization; Abandoned Hardrock Mines Act (2024) streamlines recovery permitting; Australian green procurement specifying recycled content	[214,215,216]
3. Regeneration (7–15 years)	Landscape-scale phytoremediation and Portulacaria afra (spekboom) reforestation; operationalize carbon-credit revenue; land repurposing (agriculture/eco-tourism); progressive mine closure	Communities + government + operators	The SA carbon-tax regime provides the fiscal basis for monetizing verified sequestration; the Critical Minerals and Metals Strategy (2025) embeds circular restoration	[214]

, assigning actions, lead actors, and the policy basis for each implementation horizon.

Two of these interventions directly address the certification and financing gaps identified. First, the Department of Mineral Resources and Energy, together with the South African Bureau of Standards, should develop national standards for tailings valorization extending SANS 1083, SANS 1200, and SANS 3001, so that secondary aggregates, geopolymer binders, and tailings-derived construction products achieve certified market acceptance rather than remaining technically sound but commercially unspecifiable. Second, the Department of Forestry, Fisheries, and the Environment, together with National Treasury, should establish a measurement, reporting, and verification (MRV) framework for carbon credits generated through Portulacaria afra (spekboom) reforestation and phytoremediation, so that ecological restoration can be monetized under the national carbon-tax and offset regime. Together, these instruments convert circular-economy activity from a compliance cost into a revenue-generating, investable proposition and provide policy backing for the macroeconomic incentives shown to be decisive in Section 4.

This roadmap converts circular mining from a voluntary, compliance-driven activity into an investable proposition with low-risk early-stage capital, certified products, guaranteed demand, and clear legal ownership of waste-derived resources. Critically, none of the measures requires South Africa to act without precedent; each extends a mechanism already operating in a comparable jurisdiction, adapted to existing domestic instruments such as the Critical Minerals and Metals Strategy, the National Water Act, and the carbon-tax regime. The binding risk is therefore not policy design but implementation capacity, and South Africa’s persistent challenges with licensing delays, inter-departmental coordination, and institutional capacity mean that success depends as much on administrative execution as on legislative intent. Beginning with the Foundation-phase standards and characterization work, which build directly on policy already drafted in 2025, offers the most realistic path to implementation.

6. Research Outlook

The adoption of a circular economy framework positions the South African mining industry as a regenerative, value-retaining system. While the sector’s contribution to the national GDP has declined from 20% to 8% over recent decades, the circular model provides a pathway to unlock new revenue streams, enhance resource security, and meet accelerating net-zero commitments. Successful implementation will require continued technological innovation, regulatory reform, and a shift in industrial mindset to ensure mining remains a sustainable pillar of the South African economy. However, the review identified gaps that need to be bridged to achieve circularity in the South African mining sector as well as critical directions for future research.

While technologies such as thiosulfate leaching, sensor-based ore sorting, and Coarse Particle Flotation show significant potential, further research is needed to determine their technological scalability and commercialization by advancing them from pilot trials to industry-wide commercial viability. This includes optimizing performance for South Africa’s specific low-grade and geologically variable ore bodies.

Future research should focus on advanced waste valorization pathways by expanding on the transformation of AMD and tailings into secondary resources. Key areas include the high-efficiency recovery of critical raw materials, such as vanadium, scandium, and rare-earth elements, from coal fly ash and PGM tailings. Additionally, further validation of tailings-based construction materials, such as geopolymer bricks, is required to meet national building standards. Future studies should also focus on optimizing regenerative ecological systems by refining nature-based solutions such as spekboom agroforestry and phytoremediation. Specifically, research should focus on the valorization of harvested biomass for bioenergy and the quantification of carbon credits to create self-sustaining funding models for long-term restoration.

The review has revealed a need for interdisciplinary research into regulatory frameworks that distinguish between traditional ecological restoration and resource-oriented remediation. Developing policies that provide financial incentives for waste management will be crucial for fostering systemic adoption of closed-loop systems. Furthermore, investigating how the shift to a circular model can mitigate the social equity issues related to mining pollution, particularly for the 1.6 million South Africans living near mine dumps, remains a priority. Research should also explore localized employment opportunities in new industries such as tailings re-mining and modular infrastructure maintenance.

According to the Department of Mineral and Petroleum Resources’ 2025 report [8], the macroeconomic and regulatory environment determines whether circular frameworks are profitable for private operators. The South African mining sector operates under tight margins; its contribution to nominal GDP decreased to 6.1% in 2024, and profitability remained constrained by subdued commodity prices and rising operating costs, even with the output of several critical minerals. Under these conditions, the additional capital required for tailings reprocessing, water recovery, and land regeneration is unlikely to be committed on environmental grounds alone, which makes explicit economic incentives decisive.

Carbon pricing and emissions-trading baselines are central among these enablers. International experience indicates that the way trading baselines and allocation schedules are phased in strongly shapes the economics of abatement and resource-recovery investment, and dynamic computable general equilibrium (CGE) modeling of a national emissions-trading rollout illustrates how baseline design can either accelerate or stall such investment at the sector level (Li and Jia, 2016; Jin et al., 2020 [217,218]). In the South African context, the existing carbon-tax regime, coupled with a verified carbon-credit framework for phytoremediation and Portulacaria afra (spekboom) reforestation, could convert ecological restoration into a self-sustaining revenue stream, aligning private incentives with the circular-economy transition and with the rising critical-mineral demand projected for the sector [8].

7. Conclusions

This review demonstrates that transitioning South Africa’s mining sector from a linear take–make–waste model to a circular economy is both technically viable and economically essential. It extends across the three circular-economy principles, Design Out Waste, Keep Products and Materials in Use, and Regenerate Natural Systems, applied to the Witwatersrand goldfields, the Bushveld Complex Platinum Group Metal (PGM) deposits, and the Mpumalanga coalfields. While the existing literature heavily favors generic, theoretical solutions, this review bridges the gap by mapping validated circular technologies directly onto named local operations and specific regional waste profiles. By pairing engineering innovations, such as automated sorting and geopolymer synthesis, with site-level mineralogical realities and techno-economic constraints, this work provides a realistic blueprint for sustainable resource management. Furthermore, integrating ecological initiatives, such as Portulacaria afra (Spekboom) agroforestry, underscores that true circularity extends beyond mineral extraction to encompass holistic landscape restoration.

Despite these promising frameworks, several inherent limitations in current research must be acknowledged to contextualize these findings. A primary barrier is the critical shortage of long-term, commercial-scale operational data for these technologies in the South African context, as most evidence remains confined to laboratory- or pilot-scale testing. This challenge is compounded by data transparency issues, where proprietary corporate policies restrict public access to precise, independent auditing of site-specific waste inventories. Furthermore, existing techno-economic assessments rely on static economic models that fail to account for highly volatile global commodity prices and shifting local inflation rates. From a technical perspective, simplistic mineralogical assumptions often overlook the highly complex and variable mineral matrices across different shafts, limiting the direct replication of laboratory successes. Finally, fragmented regulatory frameworks and ambiguous legal definitions distinguishing waste from by-product continue to stall immediate, widespread commercial deployment.

To overcome these barriers, future research must prioritize industrial-scale field trials to validate laboratory-proven co-disposal and valorization technologies under real-world, high-volume operational conditions. Establishing a public, blockchain-secured national geospatial database detailing the mineralogy and volume of all active and legacy tailings dams will be crucial for unlocking secondary resource extraction. Academics and practitioners should also develop dynamic life-cycle assessments (LCAs) that incorporate fluctuating carbon taxes and the evolving emissions profile of the national energy grid. Beyond the mining sector itself, comprehensive cross-sector synergy mapping is required to identify how mining by-products can be seamlessly integrated into local construction, agriculture, and chemical industries. Ultimately, future policy optimization studies must focus on designing specific, standardized legal frameworks that streamline environmental licensing, allowing South Africa to mitigate its legacy liabilities while safeguarding its position in the shifting global critical minerals market.