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Review

Towards Circularity and Sustainability: Phytoremediation Approaches, Legislative Challenges, and Bioenergy Potential in South African Mine Tailings Remediation

by
Nkanyiso Mlalazi
1,*,
Charles Mbohwa
2,
Shumani Ramuhaheli
1 and
Ngonidzashe Chimwani
3
1
Department of Mechanical, Bioresources & Biomedical Engineering, School of Engineering, University of South Africa, Johannesburg 1709, South Africa
2
Department of Industrial Engineering, School of Engineering, University of South Africa, Johannesburg 1709, South Africa
3
Department of Mining, Minerals and Geomatics Engineering, School of Engineering, University of South Africa, Johannesburg 1709, South Africa
*
Author to whom correspondence should be addressed.
Processes 2025, 13(11), 3400; https://doi.org/10.3390/pr13113400
Submission received: 30 July 2025 / Revised: 14 October 2025 / Accepted: 17 October 2025 / Published: 23 October 2025
(This article belongs to the Special Issue Biogas Technologies: Converting Waste to Energy)
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Abstract

The growing global demand for mined commodities has intensified the environmental challenges associated with mine tailings. Currently, an estimated 62,381 mining properties impact approximately 50 million square kilometers of the Earth’s land surface. Annual tailings production exceeds 10 billion tonnes and is projected to reach 19 billion tonnes by 2025. This review examines phytoremediation strategies and the associated legal framework in South Africa, highlighting a critical disconnect between existing remediation approaches, environmental legislation, and the broader sustainable development agenda. To address these gaps, a fundamental shift towards a circular economy paradigm is essential—one that aligns research, policy, and practice to foster innovative, sustainable solutions. Phytoremediation using bioenergy crops such as Vetiver grass (Chrysopogon zizanioides) offers a holistic approach that integrates environmental restoration with circularity and economic viability, while avoiding competition with food crops for arable land.

1. Introduction

Mining is a major driver of global economic growth, but it significantly disrupts the natural landscape, generates substantial amounts of waste, and poses severe environmental, health, and agricultural pollution risks [1]. The waste generated includes solid waste such as waste rock, dust, sludges, and slags; liquid waste in the form of wastewater and effluents; and gaseous emissions [2]. A global study by Ref. [3] identified approximately 62,381 mining properties that potentially impact around 50 million square kilometers of the Earth’s land surface. One of the most critical issues is the enormous volume of mine tailings left after ore beneficiation [4,5]. Annual global mine tailings production is estimated at over 10 billion tonnes [6,7]. China has over 12,000 mine areas, with 30% of these being tailings ponds, which account for approximately 70% of the country’s total solid waste. Specifically, China’s 5189 tailings ponds cover approximately 1884 square kilometers, with this area expanding by around 20 square kilometers each year, and store more than 4 billion tons of tailings [8,9]. In Australia, more than 80,000 inactive mines pose substantial risks to surrounding areas [10], while active sites generate over 1.75 billion tons of mine waste annually [11]. In Zambia’s Copperbelt Province, significant land areas are burdened with mining waste: approximately 9125 hectares contain 791 million tons of tailings, 20,646 hectares are covered by 1.9 billion tons of overburden, 388 hectares hold 77 million tons of waste rock, and 279 hectares are occupied by 40 million tons of slag [12]. By 2007, mining operations in South Africa had already converted 200,000 hectares of land and allocated another 47,000 hectares to waste dumps [13]. According to Ref. [14], South Africa has approximately 6150 officially listed abandoned mines, with areas in Gauteng province contaminated by toxic and radioactive mine residues covering around 321 km2. By 2025, it is estimated that 19 billion tons of solid tailings will accumulate, with around 20% being unrecyclable due to their complex chemical and physical structure [15]. These tailings, stored in TSFs, are considered marginal land because of their poor fertility and high levels of toxic pollutants [16]. The impact of mining and its residues is summarized in Figure 1 below.
The rapid and unprecedented surge in metal and mineral extraction over the past two decades and the projected rise in material demand are concerning indicators that associated environmental impacts will likely escalate in the future, worsening existing problems such as land degradation, energy demand, agricultural disruption, and climate change [18,19,20]. Land degradation undermines Africa’s sustainable economic development and climate resilience. The African continent, however, offers vast opportunities for restoration, with over 700 million hectares of degraded land available for rehabilitation [21]. Recently, numerous researchers have proposed the recyclability, recycling, and reuse of mine wastes, recognizing their potential benefits in reducing tailings, alleviating environmental pressures, and adding value to previously discarded materials [20]. Despite growing interest in phytoremediation for tailings management in South Africa and Africa as a whole, post-mining restoration research and practice in Africa lags behind other parts of the Global South [1].
This review aims to synthesize the existing research on tailings management and remediation in South Africa, identifying opportunities for future development and exploring opportunities for bioenergy production from TSFs to promote sustainability and circularity.

2. Methodology

Relevant articles were identified through searches on Google Scholar, Web of Science, Science Direct and Scopus using keywords such as mine tailings remediation, bioenergy production, phytoremediation, phytostabilization, phytoextraction and sustainable mining. The articles were chosen based on their relevance to the topic and the South African context. The findings were synthesized using a narrative approach, and critically evaluated for biases, limitations, and methodological flaws.

3. Mine Tailings Management in South Africa

Two crucial factors underpinning mine tailings management in South Africa are the legal framework and the technological aspects. A clear understanding of both is necessary for developing effective management strategies. Key terms of the technological aspects include remining, rehabilitation, revegetation, and remediation. Remining is the practice of extracting valuable resources from mine waste, such as tailings, to produce secondary materials of economic value [22]. Revegetation, rehabilitation, and phytoremediation are sometimes used interchangeably. Revegetation is the process of re-establishing vegetation in degraded or disturbed areas, using plant species adapted to the local conditions, to restore ecosystem stability and promote biodiversity [23]. Phytoremediation harnesses the power of specific plants and their associated soil microbes to clean up pollutants, restore degraded land, and revitalize ecosystems, enabling the land to be repurposed for productive uses [24]. Rehabilitation involves assessing the trade-offs between environmental quality and land use, optimizing management strategies to balance human needs and ecosystem services. This can include practices such as urbanization, forestry, and agriculture, or developing green spaces and infrastructure [25]. In the context of tailings storage facility (TSF) management in South Africa, the terms rehabilitation, revegetation, and remediation are often used interchangeably; however, as discussed earlier, they can have distinct meanings. While rehabilitation and revegetation may focus on stabilizing and restoring ecosystem function, remediation specifically targets the removal or mitigation of pollutants. In this discussion, the use of these terms may encompass one or multiple aspects of TSF management, and it is essential to understand the specific context and goals of each approach to appreciate the complexities of managing mine tailings in South Africa.

3.1. Evolution of the Legal Frameworks Governing Mine Tailings Management in South Africa

In 1996, the Constitution of South Africa was enacted, rendering all South Africans the right to an environment that is not harmful to their health or well-being (https://www.gov.za/sites/default/files/images/a108-96.pdf (accessed on 25 July 2025)). This constitutional provision mandates the protection of the environment for present and future generations through reasonable legislative measures. A set of laws and regulations governing mining in South Africa followed. However, Ref. [26] argue that mining legislation is not new to South Africa, as laws placing mining impact responsibilities on mine owners date back to 1903. In contrast, Refs. [27,28] contend that prior to the Minerals Act (www.gov.za/sites/default/files/gcis_document/201409/a501991.pdf (accessed on 25 July 2025)), there were no stringent guidelines, and the focus was primarily on the engineering aspects of tailings and economic gain. The negative impacts of mining were left for citizens to live with and for the state to deal with. Another attempt to address the issue of derelict and ownerless mines was the 1975 Farie Botha accord. This accord assumed 100% responsibility for mines closed before 1976, with a 50:50 responsibility between the state and mine owners for mines closed between 1976 and 1986. After 1986, mine owners were held fully responsible for mine closure [26]. Unfortunately, the Farie Botha accord did not achieve the desired results.
Currently, the reference for the obligations to rehabilitate mine sites is to a greater extent contained in the Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDA) (www.gov.za/sites/default/files/gcis_document/201409/a28-02ocr.pdf (accessed on 25 July 2025)) administered by the Department of Mineral Resources (DMR). However, mine-related activities invariably trigger other pieces of legislation. This includes the National Water Act 36 of 1998 (NWA) (https://www.gov.za/sites/default/files/gcis_document/201409/a36-98.pdf (accessed on 25 July 2025)) regulated by the Department of Water and Sanitation, the National Environmental Management Act 107 of 1998 (NEMA) (https://www.gov.za/sites/default/files/gcis_document/201409/a107-98.pdf (accessed on 25 July 2025)), National Environmental Management: Biodiversity Act 10 of 2004 (NEMBA) (www.gov.za/sites/default/files/gcis_document/201409/a10-04.pdf (accessed on 25 July 2025)) and National Environmental Management: Waste Act 59 of 2008 (NEMWA) (https://www.dffe.gov.za/sites/default/files/legislations/nema_amendment_act59.pdf (accessed on 25 July 2025)) enforced by the Department of Environment, Fisheries and Forestry (DEFF). Waste legislation is a crucial component of environmental law [29]. The Mine Health and Safety Act (MHSA) places safety and occupational obligations on mine rehabilitation and the Spatial Planning and Land Use Management Act (SPLUMA) provides a framework for organizing and regulating land use through spatial planning.
Section 43 (1), and Section 38 (1) (d) of MPRDA, 2002, Section 2 (4) (p) of NEMA, 1998 and Section 28 (1) of NEMA (https://cer.org.za/wp-content/uploads/2014/02/NEMA-107-of-1998.pdf (accessed on 25 July 2025)) all echo the same sentiment that the person responsible for the damage to the environment remain liable and is responsible for minimizing and rectifying all the damage done to the environment. The MPRDA requires mines to develop an Environmental Management Programme Report (EMPR), containing adequate provision for financial guarantees for rehabilitation, and arrangements for monitoring and auditing. Effective pollution control and rehabilitation measures on TSFs and impacted sites can be demonstrated before a mine closure certificate can be issued.
Plant species used for phytoremediation are governed by the Conservation of Agricultural Resources Act 43 of 1983 (CARA) (https://water.cer.org.za/wp-content/uploads/2018/01/CARA-43-of-1983.pdf (accessed on 25 July 2025)) and the NEMBA. CARA lays out the South African natural agricultural resources to promote soil, water, and vegetation conservation and fight invasive plants and weeds. NEMBA reverberates the same inclination as CARA, providing for (among other things) the management and conservation of South Africa’s biodiversity within the NEMA framework. For instance, the use of some alien species traditionally used in TSF vegetation has been prohibited. The CARA and NEMBA state that to ensure lasting reductions in TSF emissions and achieve site closure, ecologically meaningful rehabilitation with native vegetation that minimizes site emissions to air, water, soil, and biota is required. The act’s goal is to conserve biodiversity by controlling invasive and endangered species and encouraging the use of indigenous plants, thereby safeguarding ecosystem integrity. Selecting non-invasive species is essential to avoid unintended ecological damage [30].

3.2. Re-Mining of Mine Tailings

Legacy tailings dams are now viewed as valuable resources, containing significant amounts of gold and uranium that can be extracted using advanced technologies [31,32]. The re-mining of tailings dams in the Witwatersrand area began in the 1970s, with 77 TSFs reworked by around 1990 [33]. The re-mined tailings are redeposited as new TSF elsewhere. Although re-mining is not considered remediation, the process extracts 70–75% of pyrite, significantly reducing the potential for acid mine drainage (AMD) and release of potentially toxic elements [31]. However, some risk remains, as potential toxic elements are not removed, leaving potential for future pollution [33].
After remining, the original TSF sites, known as the footprint areas, are revegetated, primarily to restore surface stability [34]. However, studies have shown that these sites remain contaminated due to incomplete removal of tailings materials, posing ongoing pollution risks [32,33]. In the absence of specific guidelines, rehabilitation efforts for tailings and revegetation/restoration of the footprint areas are done based on “best practice technology” outlined in the guidelines for the rehabilitation of mined land [35]. Potential remediation options vary based on cost and may include several approaches such as removal of contaminated layer, capping, immobilization of the potential toxic area within the remaining layer of the tailings or topsoil by liming, clay application, sesquioxides, hydroxides, carbonates and phosphates containing minerals application [27,33], and paddocking [32].

3.3. Rehabilitation/Remediation/Revegetation of TSF

Over the past 40 years, South Africa’s mine rehabilitation strategies have undergone a significant shift, evolving through three phases: from initial land stabilization to creating monotonous grasslands, and finally, to establishing diverse landscapes, habitats, or ecotopes primarily for environmental purposes such as dust control and hydrological containment [36]. According to Ref. [27], there are two aspects that must be addressed regarding environmental pollution: containment of pollutants at the source and cleanup of the already impacted area/s. Early attempts at revegetation (prior to 1980) involved introducing species such as Australian acacias, eucalypts, and tamarisk, as well as herbaceous legumes and pasture grasses [37].
A comprehensive survey for remediation study was conducted by [38] from July 1996 until 2003 on gold and uranium TSF and adjacent polluted soils in South Africa’s deep-level mining regions (Carletonville, Klerksdorp, and Welkom). A total of 462 plant species tolerant of the harsh conditions were identified. Notably, 76–85% of these species were indigenous, perennial, and woody plants that had naturally colonized or persisted on the tailings. Species such as Cynodon dactylon and local ecotypes of Hyparrhenia hirta were being used in rehabilitation efforts, while others like Tamarix spp., Acacia spp., and perennial Eragrostis spp. showed promise due to their lack of physiological stress on tailings. The survey highlighted the potential benefits of using indigenous plant species for sustainable cover, dust control, and hydrological containment, contrasting with the costly and often ineffective practice of establishing rapid green cover using non-native pasture species that were adopted during early attempts.
In 2007, the Chamber of Mines and Coaltech produced a guideline for the rehabilitation of mined land. Species including Eragrostis curvula (Weeping Love Grass), Digitaria eriantha (Smuts finger grass) and Chloris gayana (Rhodes grass), Eragrostis tef (Teff grass), Cenchrus ciliaris, Cynodon dactylon (Kweek, Puerto Rico), Digitaria decumbens (Pongola or lowveld finger grass), Desmodium uncinatum, D. intortum and Glycine wightii, Medicago sativa (lucerne), American Sweetclover, Arlington lespedeza (Lespedeza cuneata), Lolium multiflorum (Italian ryegrass) and Avena spp. (oats), Fagopyrum sagittatum (buckwheat), Vigna spp. (cowpeas), Pennisetum typhoides (babala) and Sorghum bicolor (forage sorghums), Medicago sativa, Paspalum notatum, Hyparrhenia hirta and Cenchrus clandestinus previously Pennisetum clandestinum (Kikuyu) are listed for utilization. Plant species with dense root systems that enable them to penetrate compact subsoils and thrive in challenging soil conditions and, species found to produce exceptionally dense and penetrating root systems, such as Chrysopogon zizanioides and Pennisetum purpureum (Napier fodder), have been included [35]. This guideline continues to influence the remediation industry to date. The increased interest in using native and non-invasive plants towards conservation of natural habitat, as well as to render phytoremediation, has been reported by [39]. The approach is consistent in the rest of Africa, where research on post-mining landscape restoration primarily focuses on identifying native plant species suitable for rehabilitating metalliferous sites [1]
Although the use of indigenous species has been recommended by Ref. [35]; and Ref. [38] and further supported by the legislation, a bibliometric analysis of phytoremediation research in South Africa, conducted using Web of Science data from 1997 to 2022, identified species listed in Table 1 as some of the species used in the restoration of contaminated land in South Africa. The list includes Eichhornia crassipes (water hyacinth), Chrysopogon zizanioides (vetiver grass), and Phragmites australis, which are non-native [40].
Successful restoration, particularly through phytostabilization, depends on planting pioneer and nitrogen-fixing native species after applying site amendments to immobilize heavy metal migration, enhance nutrient availability, and improve soil structure. This approach has shown potential in a case study in the Zululand region. Coastal dune mining for heavy minerals like rutile, ilmenite, and zircon has been ongoing since 1977. The mining process involves dredging sand, separating the minerals, and returning the tailings. Restoration efforts began by respreading salvaged topsoil over the tailings to a depth of approximately 10 cm, followed by seeding fast-germinating species such as Helianthus annuus (sunflower), Sorghum spp., Pennisetum americanum, and Crotalaria juncea to aid natural colonization. As these nurse crops died, pioneer species like Acacia karoo dominated, progressing towards indigenous dune forests. This method has successfully reclaimed over 400 hectares since 1978 [55].
The application of topsoil to create a more hospitable environment for plant growth has been the norm on unfavorable gold mine tailings [56]. In South Africa, topsoil, a non-renewable resource crucial for food security, is often used in mine rehabilitation to construct store-and-release covers on TSFs, promoting grass cover, stability, and reduced erosion [56]. However, its value and scarcity, particularly in South Africa with its limited arable land, suggest it shouldn’t be the default solution. Stripping topsoil can permanently degrade it or lose its productive capacity. Furthermore, this method is costly, making it less appealing to mining companies. Therefore, alternatives for stabilizing TSFs and creating stable structures within them are worth exploring [56]. Figure 2 shows a revegetated TSF in the Witwatersrand goldfields. Ameliorants such as lime, fertilizers, and compost were applied before and during planting.
Several grass species commonly used for revegetation on mine tailings in South Africa, such as Chloris gayana and Eragrostis curvula, have limited studies on their effectiveness in phytoremediation. Instead, vast research has primarily focused on their potential as forage or pasture grasses. For example, C. gayana has been investigated for grazing land restoration [57,58], while Eragrostis curvula and Cenchrus ciliaris have been evaluated for their forage characteristics [59,60]. However, in a few studies conducted, some species such as Cynodon dactylon [61,62], Hyparrhenia hirta [63], and Pennisetum clandestinum [64], have shown promise for phytoremediation of metals, warranting further exploration.
While revegetation and rehabilitation efforts can successfully stabilize mine tailings and restore ecosystem function, these processes may not necessarily address the underlying issues of contamination issues. In some cases, tailings may be revegetated and appear functional, with lush vegetation and reduced erosion, yet still harbor pollutants that pose environmental and health risks. The effectiveness of these efforts depends on careful consideration of the plant species used and the processes followed, as some species may be better suited to specific contaminants or environmental conditions. Phytoremediation, on the other hand, offers a targeted approach to mitigating these contaminants, leveraging the unique capabilities of certain plants and microorganisms to clean up pollutants and restore land quality.

4. Solving the Conundrum: Achieving Sustainability Goals—Opportunities and Barriers

4.1. Inflexible Legal Framework

Worldwide, the mining industry is under increasing pressure to adopt sustainable practices, with recycling and waste reduction being key components of the 2030 Sustainable Development Goals framework [65]. Despite this emphasis, mining waste remains underutilized in South Africa [66]. A major obstacle to large-scale mineral waste recycling is the lack of supportive legislation and incentives [67]. The International Council on Mining and Metals (ICMM) advocates for a paradigm shift in the industry, recognizing waste materials as valuable resources rather than liabilities [68]. This perspective has evolved to promote an integrated approach to mine closure, adopting a circular economy mindset that focuses on restoration and cradle-to-cradle principles [69]. To achieve sustainability, South Africa’s mining industry must transition towards a circular economy model, which offers a compelling solution through the adoption of the hierarchy of waste management for minimizing waste, costs, and emissions, as shown in Figure 3.
Innovative approaches, such as utilizing contaminated substrates in cascading biorefineries, are emerging as a new frontier in the bioeconomy [70]. Mine waste can be repurposed for various applications, including construction materials [20], cement production [71,72], and brick manufacturing [73,74]. However, legislative challenges hinder the development of a secondary resource economy. The classification of mine waste as a residue and its designation as hazardous material create legal barriers to reuse. Furthermore, the environmental management process promotes a cradle-to-grave approach, discouraging waste reuse initiatives [75].
Embracing waste as a resource can yield substantial economic, social, and environmental benefits [76]. Fiber crops such as flax, bamboo, hemp, sisal, and kenaf, can mitigate mine-impacted environments while providing a range of products [77]. Plant species like vetiver grass, with both phytoremediation and bioenergy characteristics, can be ideal for use in phytoremediation [78,79]. However, legislative restrictions on non-native species limit the exploration of innovative approaches that could unlock the economic potential of TSFs [75,78,79]. By rethinking mine waste as a valuable resource and adopting a circular economy approach, South Africa’s mining industry can enhance its sustainability and reduce its environmental footprint.

4.2. TSF as a Resource for Bioenergy Production

The integration of bioenergy production into phytoremediation can foster sustainable land use, optimize resource utilization, and mitigate environmental impacts while promoting food and fuel security and reducing greenhouse gas emissions [16,80,81,82,83,84]. Bioenergy, a promising alternative to fossil fuels, is recovered from organic matter or lignocellulosic biomass through conversion to bioethanol or other energy sources [85]. Bioenergy development has been met with challenges, including concerns over potential competition with food crops for arable land [86,87] and competition with natural climate change mitigation processes, such as habitat conservation and afforestation [88,89,90,91]. This has hindered the widespread adoption of bioenergy solutions. Furthermore, bioenergy production on TSFs also presents opportunities for mining communities to revitalize their local economies, foster energy self-sufficiency, and stimulate economic growth. Figure 4 is an illustration of different mechanisms for bioenergy (biodiesel, biogas, bioethanol, syngas) production from post phytoremediation biomass.
Species that have been successfully utilized for phytoremediation and bioenergy production on contaminated lands include Arundo donax in Italy [93]; Helianthus annuus and Silybum marianum in Spain [94]; Jatropha curcas in Mexico [95]; Salix alba in Poland [96]; Zea mays, Brassica juncea, and Brassica napus in Mahd AD’Dahab [97] and Vetiveria zizanioides (Chrysopogon zizanioides) in China [98]. Some plant species with dual benefits for phytoremediation and bioenergy production include: Ricinus communis (castor bean); Leucaena leucocephala; Millettia pinnata; Cannabis sativa; Azadirachta indica; Acacia nilotica; Populus and Salix species (willows); Miscanthus × giganteus (elephant grass); Panicum virgatum (switch grass) [84,99].
Helianthus annuus (Sunflower) is a versatile and environmentally friendly crop, possessing desirable agronomic traits such as temperature resilience, adaptability to diverse soil conditions, rapid growth rate, high biomass production, and capacity to accumulate heavy metals, making it an excellent choice for various applications, including phytoremediation, sustainable agriculture, and bioenergy production [94,100]
Plants such as sunflower, maize, and Indian mustard have shown promise in phytoremediation and bioenergy production; however, as first-generation energy crops, they pose a risk to humans and animals [101]. These plants can introduce contaminants into the food chain, where they may accumulate in the tissues and organs of animals and humans. Contaminated lands such as TSFs pose risks to food production due to the potential accumulation of toxic substances in the food chain. However, repurposing these lands for non-food biomass production offers a viable solution. This approach can revitalize degraded lands, mitigate environmental, social, and economic impacts on local communities, and promote sustainable land use [20].
Arundo donax (giant reed) is a highly promising crop for biomass production and bioenergy conversion, with the added benefit of being adaptable to a wide range of environments. However, its high invasive potential necessitates careful ecological control measures to prevent unintended environmental impacts [93,102] because it is a highly invasive species in South Africa. It forms dense stands in riparian zones, outcompeting native plants, disrupting water flow, and increasing fire risk. As a Category 1 noxious weed under the NEMBA, the sale and planting of Arundo donax are prohibited, and control measures are mandatory to mitigate its detrimental environmental impacts.
Ricinus communis (castor bean), a member of the Euphorbiaceae family, has gained significance for biodiesel production due to its adaptability and resilience [103,104]. This fast-growing C3 plant thrives in arid and semi-arid regions as a non-edible oilseed crop. Its ability to produce high biomass under stress conditions makes it an ideal candidate for phytoremediation and bioproduct generation on contaminated sites, positioning it as a valuable feedstock for biorefineries [103,105,106,107,108]. However, this plant is considered an invasive alien species in South Africa. Its presence poses a threat to native plants due to its toxic seeds, which contain ricin, and its competitive nature. As a result, it has been declared an invasive species, requiring eradication.
Cannabis sativa L. has emerged as a versatile crop for phytoremediation, effectively cleaning soils contaminated with toxic metals. Additionally, it has been identified as a promising feedstock for bioenergy production. Recent studies have explored the integration of C. sativa L.-based phytoremediation with bioenergy processes, including concept designs for biodiesel, bioethanol, biogas, and combined heat and power production [109]. Because of Cannabis sativa’s utilization in the production of textile fiber, seed oil, medicinal applications, and potential abuse as a recreational drug, its cultivation on tailings may be problematic for South Africa.
Miscanthus × giganteus, a fast-growing grass, has also been found to be a suitable crop for bioenergy production, demonstrating relatively good growth on contaminated soils. Notably, it exhibits a low uptake of contaminants, allowing the produced biomass to be safely utilized as a biofuel [110,111]. However, it is a non-native species and not much research has been done on its use in South Africa.
Although the above plant species exhibit excellent characteristics for both phytoremediation and bioenergy production, South African legislation imposes specific regulations on the use of plants for phytoremediation of TSF. For instance, non-native plants can have devastating effects on local ecosystems, leading to significant economic losses and environmental degradation [112]. Non-native invasive species can outcompete native vegetation, disrupt delicate soil relationships, and undermine the ecosystem’s natural resilience [113,114]. Ironically, many plants with desirable traits for cleaning pollutants from soil also exhibit characteristics of invasive species [115]. One of the plant species that has not shown any proof of invasiveness in many decades since its introduction in South Africa is Chrysopogon zizanioides (vetiver grass).

Vetiver Grass: A Multi-Faceted Solution

Chrysopogon zizanioides (L.) Roberty, formerly known as Vetiveria zizanioides (L.) Nash and commonly referred to as vetiver grass, belongs to the family Poaceae [116,117]. There are two vetiver grass species in South Africa: Vetiveria nigratana, an indigenous species, and Chrysopogon zizanioides, which was introduced to KwaZulu-Natal Province from Mauritius in the 18th century. Chrysopogon zizanioides, found all over South Africa, is genetically identical to vetiver from Australia, the USA, India, and Mauritius [118]. It is noteworthy that Chrysopogon zizanioides is a sterile cultivar, which means it does not produce flowers or mature seeds. This characteristic effectively eliminates the risk of invasiveness and potential environmental harm, making it a safer choice for cultivation [119].
Vetiver grass is a fast-growing, perennial grass species renowned for its exceptional characteristics, making it an exemplary crop for phytoremediation, carbon sequestration, and bioenergy production. This versatile grass can reach heights of 1–2 m, with an extensive root system that can extend 3–4 m deep within a year [120,121]. Vetiver grass boasts exceptional resilience and adaptability, making it an ideal crop for challenging environments. Its deep roots render it extremely drought-tolerant and resistant to displacement by strong winds or water currents. Additionally, vetiver grass is a sterile, non-invasive plant that propagates through the subdivision of root clumps, producing no stolons or rhizomes [122]. This remarkable grass thrives in extreme climatic conditions, tolerating high levels of soil acidity, alkalinity, salinity, sodicity, and heavy metals. Despite these challenging conditions, vetiver grass can produce substantial biomass yields, exceeding 100 tons per hectare per year [121].
Vetiver grass (Chrysopogon zizanioides) has demonstrated exceptional tolerance to metal-induced stress, with its metabolic and photosynthetic activities remaining relatively unaffected [123]. This remarkable adaptability enables vetiver grass to thrive in contaminated environments, making it an ideal candidate for phytoremediation. Studies have shown that vetiver grass can effectively uptake and accumulate heavy metals such as Zn, Cu, Ni, and Cd from contaminated tailings and soils [123,124,125,126]. Notably, vetiver grass tends to sequester these metals in its roots, limiting translocation to the shoots, which is desirable for phytostabilization. The threshold levels for metal accumulation in vetiver shoots have been established as follows: Cu (13–15 mg kg−1), Zn (880 mg kg−1), Ni (347 mg kg−1), Cd (45–48 mg kg−1), Pb (78 mg kg−1), and Cr (5–18 mg kg−1) [127]. Although vetiver grass may not be the most efficient accumulator of heavy metals, its remarkable tolerance to adverse climate and soil conditions makes it a promising candidate for phytostabilization.
The unique characteristics of vetiver grass make it an ideal candidate for: (i) Phytoremediation: Vetiver grass can accumulate high levels of toxic metals in its roots and shoots, making it an effective agent for cleaning polluted soils [120,121,122,128]. (ii) Carbon sequestration: Vetiver grass has a high carbon sequestration potential due to its extensive root system and high biomass production, making it a valuable tool for mitigating climate change. (iii) Bioenergy production: the high biomass yields of vetiver grass make it an attractive feedstock for bioenergy production, providing a sustainable alternative to fossil fuels. Overall, vetiver grass offers a unique combination of benefits, making it an ideal crop for integrated phytoremediation, carbon sequestration, and bioenergy production systems. (iv) Due to the multiple environmental stresses that plants grown on tailings undergo, they have elevated phytochemical production. Phytochemicals are increasingly becoming a revenue-generating industry. Over eight thousand phenolic compounds with various functions, such as biotic and abiotic stress tolerance, can be produced by plants. Species such as vetiver grass and lemon grass can provide essential oils after steam distillation [129].

5. Theoretical Contributions, Practical Contributions and Limitations of the Study

This study makes significant theoretical and practical contributions. It advances the understanding of environmental impacts of mining and phytoremediation processes, informed by South Africa’s policy and regulatory frameworks. The review identified plant species used in the remediation industry, highlighting their potential for phytoremediation and limitations in dual-use applications. Several non-native species, including Miscanthus × giganteus, vetiver grass (Chrysopogon zizanioides), and Jatropha, were identified as potential candidates for both phytoremediation and bioenergy production.
However, legislative pieces like CARA and NEMBA pose challenges to using non-indigenous species due to concerns over invasiveness and water usage. Notably, vetiver grass has been extensively used in South Africa, is non-invasive, and suitable for local climate and tailings conditions. This study provides insights for mining companies to improve environmental management practices, supporting sustainable development goals and circular economy principles through the utilization of species like vetiver grass.
Limitations include the focus only on South Africa, potential bias in plant species selection, and reliance on existing literature.

6. Conclusions and Recommendations

Transforming mine tailing dumps into bioenergy hotspots can support sustainable development in South Africa. However, several gaps need to be addressed. Research should focus on firstly identifying indigenous bioenergy grass species that can thrive in TSFs environments, thereby reducing competition with food crops and natural climate change mitigation processes. Additionally, non-invasive alien species such as vetiver grass, with remarkable traits for phytoremediation and bioenergy production, can be utilized to minimize ecological harm. Further research is necessary to investigate synergies between phytoremediation, bioenergy production, carbon sequestration and adding value products from phytoremediation plants. There is also a need to quantify ecosystem services related to phytoremediation, as well as to develop enabling legislation to support the adoption of innovative solutions. A paradigm shift is necessary, integrating circular economy principles, innovation, and sustainability. This approach can restore degraded land, promote environmentally friendly practices, reduce waste, and support the development of renewable energy.

Author Contributions

Conceptualization, N.M.; methodology, N.M.; validation, N.M. and N.C.; formal analysis, N.M. and N.C.; investigation, N.M.; resources, N.M.; data curation, N.M.; writing—N.M. and N.M.; visualization, N.M. and N.C.; supervision, C.M. and S.R. project administration, N.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding. The APC was funded by the University of South Africa.

Data Availability Statement

No new data were created or analyzed in this study.

Conflicts of Interest

The authors declare no conflict of interest.

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Processes 13 03400 g001
Figure 1. Summary of the impact of mining on the ecosystem and human health (adapted from Ref. [17]).
Figure 1. Summary of the impact of mining on the ecosystem and human health (adapted from Ref. [17]).
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Figure 2. A typical vegetated tailings dam in South Africa with a mixture of different grass species, including Cynodon dactylon, Chloris gayana, Eragrostis tef, and Medicago sativa. The water pipes sprinkle water to keep the grass alive during dry months.
Figure 2. A typical vegetated tailings dam in South Africa with a mixture of different grass species, including Cynodon dactylon, Chloris gayana, Eragrostis tef, and Medicago sativa. The water pipes sprinkle water to keep the grass alive during dry months.
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Figure 3. Hierarchy of Waste Management: Prevent, Reduce, Reuse, Recycle, Recover, Dispose.
Figure 3. Hierarchy of Waste Management: Prevent, Reduce, Reuse, Recycle, Recover, Dispose.
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Figure 4. Illustrates the pathways for valorizing post-phytoremediation biomass into various products, including biofuels, value-added products, and metal recovery (adapted from [92]).
Figure 4. Illustrates the pathways for valorizing post-phytoremediation biomass into various products, including biofuels, value-added products, and metal recovery (adapted from [92]).
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Table 1. Species identified for phytoremediation in South Africa (adapted from ref. [37]).
Table 1. Species identified for phytoremediation in South Africa (adapted from ref. [37]).
Phytoremediation Technology and Pollutants TargetedSpeciesReferences
Phytostabilization and Phytoextraction of Al, Fe, and MnCyperus haspan, Schoenoplectus corymbosus, Typha capensis, Phragmites australis, Cynodon dactylon, Cyperus marginatus, and Juncus effusus[41]
Phytostabilization and Phytoextraction of Cd, Cu, and PbSalix mucronata[42]
Phytostabilization and Phytoextraction of Pb and CuHelichrysum splendidum[43]
Phytoextraction of Cd, Cu, Fe, Mn, Ni, Pb, and ZnHelianthus annuus[44]
[45]
Phytoextraction of Fe, Mn, Pb, Mg, and CrPhragmites karka
and Veteveria nigritana		[46]
Phytoextraction of CrChrysopogon zizanioides[47]
Phytoextraction of NiBerkhya coddii[48]
Phytoextraction of B, Cd, Cr, Cu, Mg, Ni, and ZnPhragmites australis[49]
Phytoextraction of NiManihot esculenta[50]
Phytoextraction of PbCorchorus olitorius[51]
Phytoextraction of CdPennisetum clandestinum[52]
Phytoextraction of Crude oil, Cd, Ni, and ZnChromolaena odorata[53]
Phytostabilisation of CuHelianthus annuus[54]
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Mlalazi, N.; Mbohwa, C.; Ramuhaheli, S.; Chimwani, N. Towards Circularity and Sustainability: Phytoremediation Approaches, Legislative Challenges, and Bioenergy Potential in South African Mine Tailings Remediation. Processes 2025, 13, 3400. https://doi.org/10.3390/pr13113400

AMA Style

Mlalazi N, Mbohwa C, Ramuhaheli S, Chimwani N. Towards Circularity and Sustainability: Phytoremediation Approaches, Legislative Challenges, and Bioenergy Potential in South African Mine Tailings Remediation. Processes. 2025; 13(11):3400. https://doi.org/10.3390/pr13113400

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Mlalazi, Nkanyiso, Charles Mbohwa, Shumani Ramuhaheli, and Ngonidzashe Chimwani. 2025. "Towards Circularity and Sustainability: Phytoremediation Approaches, Legislative Challenges, and Bioenergy Potential in South African Mine Tailings Remediation" Processes 13, no. 11: 3400. https://doi.org/10.3390/pr13113400

APA Style

Mlalazi, N., Mbohwa, C., Ramuhaheli, S., & Chimwani, N. (2025). Towards Circularity and Sustainability: Phytoremediation Approaches, Legislative Challenges, and Bioenergy Potential in South African Mine Tailings Remediation. Processes, 13(11), 3400. https://doi.org/10.3390/pr13113400

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