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

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

A comprehensive literature-based framework for transitioning South Africa's mining sector from a linear to a circular economy and other technologies. The manuscript lacks to elucidate its distinctive contributions.  The manuscript must distinguish its distinctive contributions to the literature on mining circular economy. I recommend a major revision before its acceptance. 

The review examines mining in South Africa. Figure 1 ("Production-Related Waste Managed: Metal Mining") employs global, generic data expressed in pounds (lbs) and metric tons, omitting any reference to South Africa. If possible, develop a concise section about the South African market with more details.

Figure 2 illustrates South Africa's water consumption by sector: agriculture 62%, domestic use 27%, and mining 3%. This weakens the author's principal argument regarding the catastrophic repercussions of water scarcity resulting from mining. The phrasing should transition from quantity to quality (e.g., how that 3% significantly contaminates larger regional basins via Acid Mine Drainage) or substitute this statistic with information on water usage and recycling at mine sites.
The manuscript has numerous captioned figures (1–17). Figures may consist of schematic schematics or photographs lacking scale or attribution. Figure 3, incorrectly labeled, depicts Figure 2. Kindly make this change.

Waste prevention strategies, such as advanced sensor-based ore sorting and Coarse Particle Flotation (CPF), are extensively detailed in Section 3.1. The authors ought to investigate how contemporary industrial revolutions facilitate sustainable transitions to enhance this section academically. The architectural differences between automation and human-centric systems in 'Artificial Intelligence in Sustainable Industrial Transformation: A Comparative Study of Industry 4.0 and Industry 5.0' provide a robust framework. This paper will demonstrate how the South African mining sector may transition from fundamental automated machinery (Industry 4.0) to intelligent, adaptive, and human-in-the-loop AI sorting systems (Industry 5.0) to improve resource recovery and reduce upstream mineral waste. Please explain in detail with reference to this paper.

Kindly improve all figures, with particular emphasis on Figure 15.

The authors claim that this substantiates the safety of food for consumption in proximity to South African mining wastes. Coal fly ash from South Africa contains highly volatile toxic heavy metals and radioactive nuclides, including variations of thorium and uranium characteristic of Karoo basin coal, rendering it hazardous and scientifically flawed. A peer-reviewed study should refrain from endorsing the cultivation of edible maize on fly-ash-amended tailings without evaluating bioaccumulation factors, biomagnification within the food chain, or regulatory health thresholds in South Africa. Please comment on this.

In Section 3.2 (Tailings Valorization), the authors project extensive theoretical yields for the extraction of secondary crucial raw materials (CRMs) from copper and gold mine tailings, disregarding mineralogical partitioning. Semi-arid tailings in South Africa form complex secondary mineral phases, such as jarosite or iron oxyhydroxides, which sequester target metals. The paper should elucidate how mineralogical encapsulation influences leaching kinetics and the economic feasibility of recovery cycles, rather than treating tailings as a singular resource.

Section 3.3 (Regenerate Natural Systems) presents land rehabilitation strategies that integrate mining waste management with local socio-economic agriculture, including the amalgamation of fly ash and biochar to enhance crop development. This agro-industrial link is logistically and structurally precarious. The authors are suggested to cite 'Fintech as a Catalyst for Sustainable Development in Food Systems' to enhance the feasibility of local community food security and industrial land restoration. 

The authors concentrate on the technical potential for tailings valorisation and reprocessing within the circular economy framework, although they overlook the macroeconomic and regulatory incentives essential for rendering these frameworks feasible for private mining companies. The auhors ar recommended to analyze international environmental trading baselines to substantiate these initiatives within the business. Incorporating structural perspectives from dynamic macroeconomic modeling, as demonstrated in a paper 'Dynamic Rollout Plan of China National Carbon Emissions Trading Scheme: A CGE-Based Analysis', will significantly enhance the research.

Please rewrite the conlusion based on these comments or future modifications

Author Response

Dear Reviewer

Thank you for your useful technical comments and suggestions on our manuscript. We have modified the manuscript accordingly.

Detailed corrections are listed below, point by point. Points raised by the reviewers are in italics, and changes made or our responses to those points are in normal text.

Reviewer #1

A comprehensive literature-based framework for transitioning South Africa's mining sector from a linear to a circular economy and other technologies. The manuscript lacks to elucidate its distinctive contributions.  The manuscript must distinguish its distinctive contributions to the literature on mining circular economy. I recommend a major revision before its acceptance:

• Thank you, the contributions of the review were presented in the last two paragraphs of the introduction, with the distinct contribution distinguished.

The review examines mining in South Africa. Figure 1 ("Production-Related Waste Managed: Metal Mining") employs global, generic data expressed in pounds (lbs) and metric tons, omitting any reference to South Africa. If possible, develop a concise section about the South African market with more details.

• Two paragraphs were added in the introduction and highlighted in red.

Figure 2 illustrates South Africa's water consumption by sector: agriculture 62%, domestic use 27%, and mining 3%. This weakens the author's principal argument regarding the catastrophic repercussions of water scarcity resulting from mining. The phrasing should transition from quantity to quality (e.g., how that 3% significantly contaminates larger regional basins via Acid Mine Drainage) or substitute this statistic with information on water usage and recycling at mine sites.

• Information was provided in the paragraph above Figure 2 on water usage and how it significantly contaminates larger regional basins via acid mine drainage.

The manuscript has numerous captioned figures (1–17). Figures may consist of schematic schematics or photographs lacking scale or attribution. Figure 3, incorrectly labeled, depicts Figure 2. Kindly make this change.

• The mislabelled figure is corrected, and the sequence renumbered

Waste prevention strategies, such as advanced sensor-based ore sorting and Coarse Particle Flotation (CPF), are extensively detailed in Section 3.1. The authors ought to investigate how contemporary industrial revolutions facilitate sustainable transitions to enhance this section academically. The architectural differences between automation and human-centric systems in 'Artificial Intelligence in Sustainable Industrial Transformation: A Comparative Study of Industry 4.0 and Industry 5.0' provide a robust framework. This paper will demonstrate how the South African mining sector may transition from fundamental automated machinery (Industry 4.0) to intelligent, adaptive, and human-in-the-loop AI sorting systems (Industry 5.0) to improve resource recovery and reduce upstream mineral waste. Please explain in detail with reference to this paper.

• A paragraph has been added before Section 3.1.3 addressing the reviewer’s concern

Kindly improve all figures, with particular emphasis on Figure 15.

• All figures have been improved and replaced with higher resolution

The authors claim that this substantiates the safety of food for consumption in proximity to South African mining wastes. Coal fly ash from South Africa contains highly volatile toxic heavy metals and radioactive nuclides, including variations of thorium and uranium characteristic of Karoo basin coal, rendering it hazardous and scientifically flawed. A peer-reviewed study should refrain from endorsing the cultivation of edible maize on fly-ash-amended tailings without evaluating bioaccumulation factors, biomagnification within the food chain, or regulatory health thresholds in South Africa. Please comment on this.

• The reviewer’s concern is noted and valid. The authors have corrected that in the last 2 paragraphs before Section 4.

In Section 3.2 (Tailings Valorization), the authors project extensive theoretical yields for the extraction of secondary crucial raw materials (CRMs) from copper and gold mine tailings, disregarding mineralogical partitioning. Semi-arid tailings in South Africa form complex secondary mineral phases, such as jarosite or iron oxyhydroxides, which sequester target metals. The paper should elucidate how mineralogical encapsulation influences leaching kinetics and the economic feasibility of recovery cycles, rather than treating tailings as a singular resource.

• A paragraph was inserted before Section 3.3 explaining how mineralogical encapsulation influences leaching kinetics and the economic feasibility of recovery cycles, as suggested by the reviewer.

Section 3.3 (Regenerate Natural Systems) presents land rehabilitation strategies that integrate mining waste management with local socio-economic agriculture, including the amalgamation of fly ash and biochar to enhance crop development. This agro-industrial link is logistically and structurally precarious. The authors are suggested to cite 'Fintech as a Catalyst for Sustainable Development in Food Systems' to enhance the feasibility of local community food security and industrial land restoration.

• The authors did as suggested by the reviewer in a paragraph before Section 4.

The authors concentrate on the technical potential for tailings valorisation and reprocessing within the circular economy framework, although they overlook the macroeconomic and regulatory incentives essential for rendering these frameworks feasible for private mining companies. The authors are recommended to analyze international environmental trading baselines to substantiate these initiatives within the business. Incorporating structural perspectives from dynamic macroeconomic modeling, as demonstrated in a paper, 'Dynamic Rollout Plan of China National Carbon Emissions Trading Scheme: A CGE-Based Analysis', will significantly enhance the research.

• Two paragraphs were added before Section 7, addressing the reviewer’s request.

Please rewrite the conclusion based on these comments or future modifications.

• The conclusion was rewritten to accommodate all the added information.

Reviewer 2 Report

Comments and Suggestions for Authors

This paper constructs a circular economy framework for South African mining around three core principles, integrating technologies from water recovery to phytoremediation. Its innovation lies in redefining waste as economic assets and coupling remediation with resource recovery for a scalable transition.

1. While the three principles listed in the abstract are reflected in the main text, it is recommended that the corresponding chapter subheadings be explicitly labelled as "Design Out Waste," "Keep in Use," and "Regenerate Systems" to enhance logical hierarchy and readability.
2. The AMD treatment technologies from countries such as China and India cited on pages 17–18 should be followed by a brief summary paragraph analysing their compatibility with South Africa's regulatory framework, particularly the National Water Act and Section 21 requirements.
3. The technical parameters of international case studies (e.g., from China, India, Australia, and the USA) vary considerably. It is recommended that an assessment matrix be constructed to enable quantitative comparisons across a single dimension, thereby improving the comparability and robustness of the conclusions.
4. Although multiple circular technologies are introduced, there is a lack of critical evaluation regarding their capital expenditure, operating costs, compatibility with existing processing circuits, and market acceptance. This weakens the demonstration of practical feasibility for full-scale commercial deployment in the South African mining context.
5. The proposed "sustainable framework" lacks a clear delineation of roles and responsibilities among government, mining companies, local communities, and research institutions. A phased roadmap with defined milestones and governance mechanisms should be added to enhance policy operability and stakeholder accountability.
6. While the conclusion summarises the economic and environmental value, it is recommended to include a specific policy recommendation urging the government to develop national standards for tailings valorisation and/or establish a regulatory framework for carbon credits generated through spekboom reforestation and phytoremediation, thereby enhancing practical policy guidance for the circular economy transition in South Africa's mining sector.
7. Most of the figures in this paper have low resolution and are not sufficiently clear.

 

 

 

 

 

 

 

 

 

Author Response

Dear Reviewer

Thank you for your useful technical comments and suggestions on our manuscript. We have modified the manuscript accordingly.

Detailed corrections are listed below, point by point. Points raised by the reviewers are in italics, and changes made or our responses to those points are in normal text.

This paper constructs a circular economy framework for South African mining around three core principles, integrating technologies from water recovery to phytoremediation. Its innovation lies in redefining waste as economic assets and coupling remediation with resource recovery for a scalable transition.

• Thank you

While the three principles listed in the abstract are reflected in the main text, it is recommended that the corresponding chapter subheadings be explicitly labelled as "Design Out Waste," "Keep in Use," and "Regenerate Systems" to enhance logical hierarchy and readability.

• Subheadings relabelled

The AMD treatment technologies from countries such as China and India cited on pages 17–18 should be followed by a brief summary paragraph analysing their compatibility with South Africa's regulatory framework, particularly the National Water Act and Section 21 requirements.

• The brief summary paragraphs analysing their compatibility with South Africa's regulatory framework, particularly the National Water Act and Section 21 requirements, were added (third paragraph before Section 3.2.2) as requested by the reviewer.

The technical parameters of international case studies (e.g., from China, India, Australia, and the USA) vary considerably. It is recommended that an assessment matrix be constructed to enable quantitative comparisons across a single dimension, thereby improving the comparability and robustness of the conclusions.

• An assessment was given in the paragraphs below Table 1.

Although multiple circular technologies are introduced, there is a lack of critical evaluation regarding their capital expenditure, operating costs, compatibility with existing processing circuits, and market acceptance. This weakens the demonstration of practical feasibility for full-scale commercial deployment in the South African mining context.

• The critical evaluation regarding their capital expenditure, operating costs, compatibility with existing processing circuits, and market acceptance was given in Section 4.

The proposed "sustainable framework" lacks a clear delineation of roles and responsibilities among government, mining companies, local communities, and research institutions. A phased roadmap with defined milestones and governance mechanisms should be added to enhance policy operability and stakeholder accountability.

 

• The policy recommendations and implementation roadmap were given in Section 5.

While the conclusion summarises the economic and environmental value, it is recommended to include a specific policy recommendation urging the government to develop national standards for tailings valorisation and/or establish a regulatory framework for carbon credits generated through spekboom reforestation and phytoremediation, thereby enhancing practical policy guidance for the circular economy transition in South Africa's mining sector.

• The policy recommendation was included in the conclusion.

Most of the figures in this paper have low resolution and are not sufficiently clear.

• Corrected

Reviewer 3 Report

Comments and Suggestions for Authors

I would like to thank the authors very much for their hard work on this article. The article is up-to date, well documented, based on many recent publications, and includes extensive technological examples. This is its strong point. I have a few comments and suggestions for the authors.
1. The abstract is too general. Please specify which review methods were used and what the key findings are, rather than merely describing the scope of the topic. I suggest clarifying this in the methodology section as well.
2. Please identify the research gaps that this article addresses.
3. Please ensure that all graphs include axis labels.
4. Please consider including summary tables, e.g., a comparison of tailings processing methods or emergency technologies. This will significantly improve readability and clarity.
5. Please ensure the use of scientific language throughout the article (e.g., “prevents the creation of ghost infrastructure”)

Author Response

Dear Reviewer

Thank you for your useful technical comments and suggestions on our manuscript. We have modified the manuscript accordingly.

Detailed corrections are listed below, point by point. Points raised by the reviewers are in italics, and changes made or our responses to those points are in normal text.

I would like to thank the authors very much for their hard work on this article. The article is up-to date, well documented, based on many recent publications, and includes extensive technological examples. This is its strong point. I have a few comments and suggestions for the authors.

• Thank you

The abstract is too general. Please specify which review methods were used and what the key findings are, rather than merely describing the scope of the topic. I suggest clarifying this in the methodology section as well.

• The abstract was rewritten with the review methods used and the key findings specified.

Please identify the research gaps that this article addresses.

• The research gaps were provided in the last paragraph of the introduction.

Please ensure that all graphs include axis labels.

• Labelled and corrected

Please consider including summary tables, e.g., a comparison of tailings processing methods or emergency technologies. This will significantly improve readability and clarity.

• Table 2 was provided as the summary Table

Please ensure the use of scientific language throughout the article (e.g., “prevents the creation of ghost infrastructure”).

• corrected

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for your efforts in preparing the article.

Please see the detailed comments on the manuscript.

I wish you success in the next stages of the publishing procedure.

 

Comments to Authors:

A brief summary

This review paper discusses the transformation of the South African mining sector from a linear model (which in its current state is no longer economically viable and degrades the environment) to a circular economy by incorporating waste prevention, waste valorisation and ecosystem regeneration. The article identifies several technologies that could be a driving force for this systemic change. In this particular context, it is a guide for implementing a sustainable circular economy in mining industry through the use of innovative solutions, focused on maintaining the value of resources, materials and products throughout their entire life cycle and minimizing waste generation. A holistic approach to implementing a circular economy assumes not only the sustainable use of resources and raw materials (including  their simultaneous regeneration) and effective waste management, but also the protection and restoration of ecosystems destroyed by mining activities, using advanced environmental technologies.

 Comments regarding general concepts

This article demonstrates the need for a comprehensive analysis of regulatory frameworks that distinguish between traditional ecological restoration and resource-oriented remediation. The authors of the article show that the circular economy integration is a promising approach (scalable and at the same time economically justified), which can support the effective transformation of the linear mining industry into a regenerative system oriented towards environmental protection. It should be emphasized that all actions taken to implement sustainable solutions, especially in the case of an industry sector that significantly affects the natural environment, such as mining industry, is crucial for sustainable development. The concept presented in the article is an innovative strategy that should be promoted.

Although the concept of the work is logical, a certain dissonance can be noticed.  The manuscript gives an impression of  being assembled from separate parts prepared by different people (as indicated by different way of formulating thoughts or formatting the text). In the case of multi-authored manuscripts, this might be a common practice, but I propose its comprehensive unification to ensure that the text is coherent and harmonious.

Specific comments 

The article is well structured, generally sections and paragraphs are well organized. However, please clearly indicate the purpose and scope of the work in  the “Introduction” section.

The paper is written in the correct scientific language and in proper English. It is suggested to check the text for minor spelling errors (unnecessary use of capital letters, e.g. lines 58 or 63).

 

Figures and tables

All tables and figures are adequately selected and correspond to the text. Generally, the graphic elements (figures) are neat and legible. I suggest improving layout of the Table 1 to make it more visually attractive.

I would like to point out that there are errors in the numbering of the figures (Figure 2 is duplicated). Moreover, figure captions should meet standard requirements and constitute a separate element of the text. The caption should be a kind of title (a concise explanation of what the graphic shows), not an extended commentary/discussion. It is recommended to use sentence equivalents. This applies especially to figures from 3 to 5.

Please choose one way to provide the source of the graphic elements – numerical or full description.

References:

The references list consists of 199 literature items. The number of references is sufficient and their selection is appropriate. The list consists of the most important and latest literature items related to the subject of the article. The citation style used in the article is acceptable, however, it is recommended to verify the citations throughout the text – minor errors have been noted.

The description of literature item no.196 is different from the others - it should be unified. Furthermore, I would like to mention that the graphic layout of the list of literature is slightly disturbed from position 170.

Mistakes in the use of abbreviations/errors in nomenclature

An explanation of an acronym is only required the first time it is used in the text. In subsequent paragraphs, the acronym or the full name is used independently.

Line 138/333/556  – the term AMD was used earlier in the text. It was used for the first time in section 1 (line101) – it is advisable to explain the acronym when it is first used in the text.

Line 322 – full explanation of the abbreviation recommended; GEMs: genetically engineered microorganisms

Line 607 - the same applies to RO (and all other abbreviations in the text) – it is advisable to explain the acronym when it is first used in the text

Line 888: Incorrect use of the acronym PFA (pulverised fuel ash)

 

In scientific and natural science texts, Latin names of organisms are subject to strict formatting rules, i.e. Latin names of bacterial strains or plants are usually written in italics, e.g. Acidithiobacillus spp. (line 333), Helichrysum splendidum (Line 971; 860), Chrysopogon zizanioides (line 864)

 

Additional comments to the text:

Line 239-246: suggested reconstruction of a fragment of the text due to repetition

Author Response

Dear Reviewer

Thank you for your useful technical comments and suggestions on our manuscript. We have modified the manuscript accordingly.

Detailed corrections are listed below, point by point. Points raised by the reviewers are in italics, and changes made or our responses to those points are in normal text.

This review paper discusses the transformation of the South African mining sector from a linear model (which in its current state is no longer economically viable and degrades the environment) to a circular economy by incorporating waste prevention, waste valorisation and ecosystem regeneration. The article identifies several technologies that could be a driving force for this systemic change. In this particular context, it is a guide for implementing a sustainable circular economy in mining industry through the use of innovative solutions, focused on maintaining the value of resources, materials and products throughout their entire life cycle and minimizing waste generation. A holistic approach to implementing a circular economy assumes not only the sustainable use of resources and raw materials (including their simultaneous regeneration) and effective waste management, but also the protection and restoration of ecosystems destroyed by mining activities, using advanced environmental technologies.

• Thank you

This article demonstrates the need for a comprehensive analysis of regulatory frameworks that distinguish between traditional ecological restoration and resource-oriented remediation. The authors of the article show that the circular economy integration is a promising approach (scalable and at the same time economically justified), which can support the effective transformation of the linear mining industry into a regenerative system oriented towards environmental protection. It should be emphasized that all actions taken to implement sustainable solutions, especially in the case of an industry sector that significantly affects the natural environment, such as mining industry, is crucial for sustainable development. The concept presented in the article is an innovative strategy that should be promoted.

• Thank you

Although the concept of the work is logical, a certain dissonance can be noticed.  The manuscript gives an impression of  being assembled from separate parts prepared by different people (as indicated by different way of formulating thoughts or formatting the text). In the case of multi-authored manuscripts, this might be a common practice, but I propose its comprehensive unification to ensure that the text is coherent and harmonious.

• The different way of formatting might have occurred during the transfer of the original manuscript text to the journal template. However, the manuscript was unified as suggested.

The article is well-structured, and the sections and paragraphs are generally well organized. However, please clearly indicate the purpose and scope of the work in the “Introduction” section.

• The purpose and scope of the work were provided in the last paragraph of the introduction.

 

The paper is written in the correct scientific language and in proper English. It is suggested to check the text for minor spelling errors (unnecessary use of capital letters, e.g. lines 58 or 63).

• Corrected

All tables and figures are adequately selected and correspond to the text. Generally, the graphic elements (figures) are neat and legible. I suggest improving layout of the Table 1 to make it more visually attractive.

• The layout of Table 1 was improved.

I would like to point out that there are errors in the numbering of the figures (Figure 2 is duplicated). Moreover, figure captions should meet standard requirements and constitute a separate element of the text. The caption should be a kind of title (a concise explanation of what the graphic shows), not an extended commentary/discussion. It is recommended to use sentence equivalents. This applies especially to figures from 3 to 5.

•  

Please choose one way to provide the source of the graphic elements – numerical or full description.

• The authors are not sure if they understood what the reviewer requested, but they captioned all the figures as normally done.

The references list consists of 199 literature items. The number of references is sufficient and their selection is appropriate. The list consists of the most important and latest literature items related to the subject of the article. The citation style used in the article is acceptable, however, it is recommended to verify the citations throughout the text – minor errors have been noted.

• Thank you, they were verified.

The description of literature item no.196 is different from the others - it should be unified. Furthermore, I would like to mention that the graphic layout of the list of literature is slightly disturbed from position 170.

• Thank you, it has been fixed.

An explanation of an acronym is only required the first time it is used in the text. In subsequent paragraphs, the acronym or the full name is used independently.

• Thank you, it has been fixed

Line 138/333/556  – the term AMD was used earlier in the text. It was used for the first time in section 1 (line101) – it is advisable to explain the acronym when it is first used in the text.

• Corrected

Line 322 – full explanation of the abbreviation recommended; GEMs: genetically engineered microorganisms.

• Corrected

Line 607 - the same applies to RO (and all other abbreviations in the text) – it is advisable to explain the acronym when it is first used in the text.

• Thank you, it has been fixed

Line 888: Incorrect use of the acronym PFA (pulverised fuel ash).

• Corrected

In scientific and natural science texts, Latin names of organisms are subject to strict formatting rules, i.e. Latin names of bacterial strains or plants are usually written in italics, e.g. Acidithiobacillus spp. (line 333), Helichrysum splendidum (Line 971; 860), Chrysopogon zizanioides (line 864).

• Thank you, it has been corrected.

Line 239-246: suggested reconstruction of a fragment of the text due to repetition.

• Corrected

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The paper can be accepted now