Navigating the Sustainability Conundrum of Construction Sand

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors, please find revision of your manuscript submitted to Sustainability. This manuscript gives some good insight about management of sand industries worldwide, from the environmental, geopolitics and sustainability aspects. Using MFA, Authors clearly presented available data on global scale. Written language of manuscript is on high level. However, some weaknesses of manuscript are detected.

Abstract:

Great, summarized presentation of your paper. Think to include some percentage of China’s consumption of sand compare to global share, to boost quality and visibility of your Abstract.

Keywords: It is not common to use same word (in this case sand) from title in keywords. Please consider to make changes.

Introduction:

Very well written chapter. Good introduction to your manuscript.

Line 64: Put space between last word in sentence and reference bracket.

Lines 107-109: The sentence is too informal to be used in this kind of publication.

Lines 133-134: Add the reference at the end of sentence.

In the last chapter (1.4. Significance and objectives of this study, lines 129-150), please consider to add one or two sentence about methodology used in this paper. It is not common to include references in the last chapter of introduction. Please consider to move/remove references from this part of paper.

Methodology:

This chapter provides everything that this part of paper needs to possess.

Lines 155-156: Give some insights of PRISMA guidelines or some reference at the end of sentence where is briefly explained.

Line 174: Please provide the better quality of Figure 1. Same for Figure 2 (line 196).

Lines 270-272: Add the reference at the end of sentence.

Global sustainability of sand through the lens of MFA:

This chapter needs improvements since there aren’t any statistical results. Some indices could be calculated and presented in this part of manuscript.

Line 315: Reduce the number of significant number of presented values on Figure 3, to improve visibility of columns.

Line 353: Transfer Figure 5 before line 344, since you mentioned Figure 5 firstly in line 342.

Lines 344-352: Add missing references about usage of recycled aggregates per countries.

Act II: The unseen impact of the sand industry on the environment:

Line 361: Please provide better quality of Figure 6.

Geopolitics, conflicts, and the global sand crisis:

This chapter needs restructuration. There is not any numerical values about trades between countries.

Sustainable Development Goals, policies, and possible solutions:

This part of manuscript does not need any improvements. Good summary and recommendations for national and global policies. Well written!

Conclusion:

Good conclusions from your manuscript. However, please here one sentence about used methodology. Also, which SDGs are mostly affected by sand industry?

Lines 600 and 601: Consider to change one of sentences that begin in mentioned lines: This study …

Author Response

Reviewer 1

Dear Authors, please find revision of your manuscript submitted to Sustainability. This manuscript gives some good insight about management of sand industries worldwide, from the environmental, geopolitics and sustainability aspects. Using MFA, Authors clearly presented available data on global scale. Written language of manuscript is on high level. However, some weaknesses of manuscript are detected.

Respected reviewer, we sincerely thank you for your encouraging words and invaluable inputs to the manuscript. We are grateful that the methodology we have utilized to incorporate global sand management, environmental externalities, and geopolitics, has been acknowledged for its relevance, despite the severe challenges we faced regarding the data availability and reliability. We understand the need to maintain consistency and quality and thus have carefully revised the manuscript addressing your comments. Below, each of the comments have been addressed and revised in detail.

Abstract:

Great, summarized presentation of your paper. Think to include some percentage of China’s consumption of sand compare to global share, to boost quality and visibility of your Abstract.

Keywords: It is not common to use same word (in this case sand) from title in keywords. Please consider to make changes.

Thank you for your comment!

Based on the given feedback, the first keyword has been changed to “sustainability” in the manuscript.

China’s consumption perspective has been addressed in the revised abstract which was also recommended by other two reviewers.

 

Introduction:

Very well written chapter. Good introduction to your manuscript.

Line 64: Put space between last word in sentence and reference bracket.

Lines 107-109: The sentence is too informal to be used in this kind of publication.

Lines 133-134: Add the reference at the end of sentence.

In the last chapter (1.4. Significance and objectives of this study, lines 129-150), please consider to add one or two sentence about methodology used in this paper. It is not common to include references in the last chapter of introduction. Please consider to move/remove references from this part of paper.

Thank you for your encouraging words.

The issues regarding the space, informal tone and the reference in specific sentences have been addressed. We have also mentioned about methodology in the revised manuscript.  

However, as a team, we believe that the references mentioned in Section 1.4 (addressed for other three reviewers as well) add to the novelty of the study by highlighting the existing body of literature, which in turn led us to concretely address the identified research gap.

Methodology:

This chapter provides everything that this part of paper needs to possess.

Lines 155-156: Give some insights of PRISMA guidelines or some reference at the end of sentence where is briefly explained.

Line 174: Please provide the better quality of Figure 1. Same for Figure 2 (line 196).

Lines 270-272: Add the reference at the end of sentence.

Thanks for appreciating the approach we followed in this section.

In the revised manuscript, a brief statement has been added to elucidate the PRISMA guidelines along with the proper reference (Page 5, Line205-207). Higher-quality versions of Figures 1 and 2 have also been included. We apologize for having previously omitted the reference for this particular sentence, which has now been added in the revised manuscript.

Global sustainability of sand through the lens of MFA:

This chapter needs improvements since there aren’t any statistical results. Some indices could be calculated and presented in this part of manuscript.

Line 315: Reduce the number of significant number of presented values on Figure 3, to improve visibility of columns.

Line 353: Transfer Figure 5 before line 344, since you mentioned Figure 5 firstly in line 342.

Lines 344-352: Add missing references about usage of recycled aggregates per countries.

Thank you for your comments. We have revised the values in Figure 3 and have added the missing reference. We have to omit Figure 5 (of the previous version of our manuscript) to address another reviewers comment.  

We have tried to capture the input features, consumption patterns, and recycled aggregates—three of the most important indices of material flow analysis for the studied countries. Since these indices are highly statistics-heavy, we opted to present them through Figures 3, and 4 to avoid confusion and prevent monotonous reading. Instead, we explained the indices in the narratives of three separate sections of this chapter so that readers may find it interesting and can follow easily. While we agree that the manuscript would benefit from the use of relevant indices, there were major limitations due to the lack of data and reliability of the data we found. Since we had to rely on a big portion of gray literature for these values, the reliability of the data remains questionable as many sources simply state the mass of sand demanded at a certain year, with no way follow up on how much sand was used. Therefore, the simplified approach to look at input, consumption patterns, and recycled aggregate use was used to compensate for these issues.  

Act II: The unseen impact of the sand industry on the environment:

Line 361: Please provide better quality of Figure 6.

The better quality of figure has been added (now Figure 5 in the revised manuscript)  

Geopolitics, conflicts, and the global sand crisis:

This chapter needs restructuration. There is not any numerical values about trades between countries.

Thank you for your comment!

Much of the trade mentioned here is illicit by nature thus it has been challenging to cite values for the trade. However, the issue with trade data discrepancy has been highlighted using the case of Singapore and Myanmar with the appropriate source referenced. Unfortunately, the research referenced in our study regarding this discrepancy was recorded for a period of 2007–2016, rather than for any singular year, as well as the years preceding the timeline set for the literature search for the MFA indicators. Such discrepancies further meant that quoting values reported by UNCOMTRADE would be insufficient because there is no available method to cross-check on the authenticity of the value reported.

 Sustainable Development Goals, policies, and possible solutions:

This part of manuscript does not need any improvements. Good summary and recommendations for national and global policies. Well written!

Thank you for your comment!

 

Conclusion:

Good conclusions from your manuscript. However, please here one sentence about used methodology. Also, which SDGs are mostly affected by sand industry?

 

Thank you for your comment!

From the study we can conclude all the SDGs are at conflict with the sand industry as explained in section 6.1. In doing so, SDGs 1, 3, 4, 8, 10, and 16 can be improved for the people involved with the industry as well as SDGs 13, 14, and 15 allow better protection of the environment. We have reiterated that in the conclusion, separating them into the SDGs that human beings are involved with and the SDGs that the environment is affected by due to sand mining (Page 19, Line 717-719).

Lines 600 and 601: Consider to change one of sentences that begin in mentioned lines: This study …

Thanks for your suggestions and it has been addressed in the revised manuscript.

Reviewer 2 Report

Comments and Suggestions for Authors

This study was conducted on navigating the sustainability problem in the construction sand industry. During the review of this study, I found that the authors have done a great job, and the findings of this study have the potential to be published. However, I also found some weaknesses that need to be considered at the revision stage.

1. The abstract of this study does not reflect the entire picture of the article. Authors should emphasize the research method and key findings.
2. In the introduction section, it is important to disclose how the authors identified the research gap and how this study will contribute to scholarly knowledge.
3. Figure 2 background color can be white for better visibility.
4. Lack of practical implications and policy relevance.
5. What is the theoretical contribution of this study? Research limitations and future research work should be disclosed in a separate subsection in the conclusion.
6. Overall, this study has several insightful findings but a few flaws that need to be improved upon at revision time.

Author Response

Reviewer 2

This study was conducted on navigating the sustainability problem in the construction sand industry. During the review of this study, I found that the authors have done a great job, and the findings of this study have the potential to be published. However, I also found some weaknesses that need to be considered at the revision stage.

Respected reviewer, we sincerely thank you for your inputs to the manuscript. We are grateful that the methods we have utilized have been acknowledged for its relevance, despite struggling with the reliability of the data. We understand the need to maintain consistency and thus have carefully revised the manuscript addressing your comments. Below, each of the comments have been addressed and revised in detail.

1. The abstract of this study does not reflect the entire picture of the article. Authors should emphasize the research method and key findings.

Thank you for your comment!

The use of the combination of material flow analysis indicators, environmental externalities, and geopolitics by using a systematic review has been incorporated in the revised manuscript.

(Page 1, Line 17-19, 24-28 and 30-32).

2. In the introduction section, it is important to disclose how the authors identified the research gap and how this study will contribute to scholarly knowledge.

Thank you for your comment!

In the revised manuscript we have added insight into how examining the cement industry led to the identification of the research gap. The use of sand is crucial to making clinker for cement and concrete, and all existing stock and flow-based research is done by estimating the ratios of sand used. The scattered nature of studies considering environmental externalities, and the extensive coverage of the geopolitical concerns with sand have also been included. This led to realizing the lack of literature that combines these elements to provide one big picture through which researchers could understand the state of the existing sand industry on a global scale (Page 4, Line 178-189).

3. Figure 2 background color can be white for better visibility.

Thanks for your suggestion and we have amended the figure accordingly.

4. Lack of practical implications and policy relevance.

Thank you for your comment. In fact, we consider this an invaluable comment, as it allows us to explain a few more important issues that were integral to conceiving the idea of this research. When discussing the sustainability and circularity of construction materials—given their massive consumption and the often-limited availability of stocks—sand remains particularly challenging due to the severe lack of data. At the same time, from a policy perspective, resource circularity warrants data-intensive methodologies such as MFA. However, in the case of sand, very few studies have addressed this critical resource, largely because of the unavailability and unreliability of data, as well as the prevailing skepticism surrounding it across the globe. These challenges have discouraged many researchers from advancing further, which could otherwise create a fundamental basis for policy and practice. Our endeavor, therefore, was a deliberate move in this direction, aiming to establish a basic platform for further exploration.

Regarding the flow of the narratives in our article, despite all the challenges associated with data in this field, we have sought to establish and frame the discourse on global sand sustainability through the lens of MFA—addressing not only the environmental externalities of the sand industry, but also the ongoing complexities of geopolitics, conflicts, and the global sand crisis. We sincerely believe that this contribution will support research enthusiasts and relevant stakeholders in adopting or retrofitting policies, as further articulated in Chapter 6: ‘Sustainable Development Goals, Policies, and Possible Solutions’.

In order to concretely address reviewers’ comment, we have added a completely new section 6.4 Policy implications (Page 18, Line 672-684).

5. What is the theoretical contribution of this study? Research limitations and future research work should be disclosed in a separate subsection in the conclusion.

Thank you for your comment!

The theoretical contribution of this study lies in the contextualization of sand flows through the lens of social metabolism. Sand extraction depicts the classical case of stock-flow dynamics, and when extracted and used, it has implications on local resource depletion, setting the scene up for geopolitics in a time where the demand for sand is only increasing. The study also sheds light on the limits of circularity as sand’s nature as a non-renewable, intermediate resource to the construction sector can be a major challenge to circular economy frameworks.  The use of environmental externalities clearly displayed the socioeconomic inequalities caused by sand extraction and consumption, tying in with the nature of geopolitics, illicit trading, and informality of the sector regulating the flow of sand. The use of MFA in this study further highlights its importance as a science-policy link to reveal hidden flows that are currently present due to lock-ins of the existing construction landscape.

(addressed in the revised version of the manuscript specially in Abstract, Introduction and Conclusion).

The concerns regarding the research limitations and future research work have been addressed in the conclusion. It should be noted that they were addressed by further linking them with the implications of the SDGs, emphasizing the need for monitoring and better governance. Furthermore, future research endeavors utilizing local materials for eco-construction and improving transparency for sand data has been highlighted in the conclusion.   

6. Overall, this study has several insightful findings but a few flaws that need to be improved upon at revision time.

Thank you for your encouraging words. We have tried to revise the entire manuscript based on the comments of all five reviewers. 

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript addresses an important and under-studied topic: the sustainability of the construction sand industry, using a light-weight material flow analysis (MFA) framework assembled from trade statistics, grey literature, and a PRISMA-guided review. The scope—to connect quantitative MFA indicators with environmental externalities and geopolitical context—is timely and potentially impactful. However, in its current form the paper’s methodological rigor is insufficient for reproducibility and for supporting several prominent claims.

1. You list the MFA indicators (DE, I, E, DMI = I+DE, DMC = DMI–E, and “recycling rates if available”), but the paper does not show explicit, per-country equations, data sources, and reconciliation steps (e.g., mirror statistics, unit harmonization) used to compute each indicator.
2. You acknowledge that countries often report sand together with gravel or construction vs industrial sands differently, which can bias DE/I/E and hence DMI/DMC.
3. Clarify whether recycled aggregates used in place of natural sand were treated as additional “I” or as a separate “recycling input,” and how you prevented double counting between demolition outputs and inputs. The claim that China’s recycling input is 200 Mt and that Europe balances virgin and recycled inputs (20–30% of total aggregate consumption) needs a uniform definition and country-specific source notes.
4. Provide a supplementary table listing the raw DE/I/E values, the computation from DMI to DMC, and checksums for each country producing the values shown.
5. Data years across sources appear inconsistent.
6. You assert a novel combination of quantitative masses with trade indicators, environmental impacts, and geopolitics. Strengthen the literature map to clearly demarcate where your quantitative pipeline extends prior China-focused MFA work and global SDG mappings.
7. I recommend that the authors strengthen the Introduction by situating their work within the broader context of sustainable construction materials, circular economy approaches, and sediment transport modeling, and to this end it would be highly beneficial to cite the following relevant studies together: “In-situ investigation on dynamic response of highway transition section with foamed concrete”; “Modulation of initial CaO/Al2O3 and SiO2/Al2O3 ratios on the properties of slag/fly ash-based geopolymer stabilized clay: Synergistic effects and stabilization mechanism”; “Performance and geocell-soil interaction of sand subgrade reinforced with high-density polyethylene, polyester, and polymer-blend geocells: 3D numerical studies”; “Assessment of the impacts of the life cycle of construction waste on human health: lessons from developing countries”; “Randomly generating realistic calcareous sand for directional seepage simulation using deep convolutional generative adversarial networks”. Including these references in a single, well-integrated discussion would not only highlight the relevance of engineered substitutes and circular practices but also underscore the importance of robust transport modeling and health impact assessment for a comprehensive understanding of sand sustainability.

Author Response

Reviewer 3

This manuscript addresses an important and under-studied topic: the sustainability of the construction sand industry, using a light-weight material flow analysis (MFA) framework assembled from trade statistics, grey literature, and a PRISMA-guided review. The scope—to connect quantitative MFA indicators with environmental externalities and geopolitical context—is timely and potentially impactful. However, in its current form the paper’s methodological rigor is insufficient for reproducibility and for supporting several prominent claims.

Respected reviewer, we sincerely thank you for your inputs to the manuscript. We are grateful that the methodology we have utilized has been acknowledged for its timely relevance, despite struggling with the reliability of the data. We understand the need to maintain methodological rigor and thus have carefully revised the manuscript addressing your comments. Below, each of the comments have been addressed and revised in detail.

1. You list the MFA indicators (DE, I, E, DMI = I+DE, DMC = DMI–E, and “recycling rates if available”), but the paper does not show explicit, per-country equations, data sources, and reconciliation steps (e.g., mirror statistics, unit harmonization) used to compute each indicator.

 

Thank you for your comment!

In the revised manuscript we have included a paragraph highlighting what the equations mean from this study’s point of view (Page 7, Line 255-270). Overall, they provide a general framework that was used to interpret the data we got from various sources. Owing to the issue with scanty data, we had little choice than simply assume that the value reported by the country for input refers to the DMIsand. Another issue we ran into was the overall heterogeneity of the way the data was reported. Since we had to rely on a big portion of gray literature for these values, the reliability of the data remains questionable as many sources simply state the mass of sand demanded at a certain year, with no way follow up on how much sand was used. Thus, no country specific models were built due to the data gap and reliability issues.

 

2. You acknowledge that countries often report sand together with gravel or construction vs industrial sands differently, which can bias DE/I/E and hence DMI/DMC.

 

Thank you so much for your comment!

In the revised manuscript this comment has been incorporated as a nuanced element for readers and reviewers to note (Page 7, Line 255-261).

 

3. Clarify whether recycled aggregates used in place of natural sand were treated as additional “I” or as a separate “recycling input,” and how you prevented double counting between demolition outputs and inputs. The claim that China’s recycling input is 200 Mt and that Europe balances virgin and recycled inputs (20–30% of total aggregate consumption) needs a uniform definition and country-specific source notes.

 

Thank you for your comment!

Sand and aggregates from previous DMC demolitions would have ended up in landfills because the recycling market for these materials is still very small (i.e. historical DE +I).  We are not at risk of double counting because the sources are from previous DMCs.  The same will apply to recycling in China and the EU.  One issue, though, is that many companies create aggregates, and during the process, waste is produced and recycled back into production as a continuous process. For this study, no such mentions were found in any of the sources.  To prevent the possibility of duplicate counting, the mass of recycled aggregates that contained such inputs would be subtracted.

 

The issue with the availability of data has been highlighted using the case of Canada. Since the data source for Canada was an online website, we noticed the data for 2021 had changed since the last time we worked on the calculations for this manuscript. On top of that, the source where the data was collected for the mass of recycled aggregates was sourced from is not available anymore. Such discrepancies add more difficulty to an already challenging task but the reality of this has been highlighted in the revised manuscript (Page 7, Line 255-270 and Page 10, 346-350).

 

4. Provide a supplementary table listing the raw DE/I/E values, the computation from DMI to DMC, and checksums for each country producing the values shown.

 

Thank you for the comment, the supplementary information will be provided along with the revised manuscript.

5. Data years across sources appear inconsistent.

 

Thank you for your comment!

This was the biggest challenge to address within this study due to the limited availability of data. However, as mentioned in Section 2.1, the years for this study were narrowed down between 2016 to 2021. In Table 1 of the study, the sources along with the years they are from have been specified.

 

6. You assert a novel combination of quantitative masses with trade indicators, environmental impacts, and geopolitics. Strengthen the literature map to clearly demarcate where your quantitative pipeline extends prior China-focused MFA work and global SDG mappings.

 

Thank you for your comment!

Due to the extreme absence of data, sand continues to be particularly difficult to discuss when it comes to the sustainability and circularity of construction materials, given their enormous consumption and frequently limited stock availability. However, resource circularity justifies data-intensive approaches like MFA from a policy standpoint. However, because to the lack of data and its unreliability, as well as the widespread skepticism about it worldwide, relatively few researchers have examined this vital resource. To create a foundational framework for future research, our effort was a purposeful step in this direction by merging the use of quantitative factors with existing qualitative research. It should also be noted that prior to specific MFA work, much of the estimations on sand were simply based off estimates of cement production data.

 

Reviewers suggestion has been addressed in Page 4, Line 166-170 in the revised manuscript.

 

7. I recommend that the authors strengthen the Introduction by situating their work within the broader context of sustainable construction materials, circular economy approaches, and sediment transport modeling, and to this end it would be highly beneficial to cite the following relevant studies together: “In-situ investigation on dynamic response of highway transition section with foamed concrete”; “Modulation of initial CaO/Al2O3 and SiO2/Al2O3 ratios on the properties of slag/fly ash-based geopolymer stabilized clay: Synergistic effects and stabilization mechanism”; “Performance and geocell-soil interaction of sand subgrade reinforced with high-density polyethylene, polyester, and polymer-blend geocells: 3D numerical studies”; “Assessment of the impacts of the life cycle of construction waste on human health: lessons from developing countries”; “Randomly generating realistic calcareous sand for directional seepage simulation using deep convolutional generative adversarial networks”. Including these references in a single, well-integrated discussion would not only highlight the relevance of engineered substitutes and circular practices but also underscore the importance of robust transport modeling and health impact assessment for a comprehensive understanding of sand sustainability.

 

Thank you for your comment!

All the studies mentioned above have been added to our study and they are addressed in the manuscript by connecting them to section 1.2. The insights provided by the literature opened new avenues for discussion within the realm of eco-construction. We specifically integrated insights about the product innovation through using foamed concrete, design innovation through material optimization of geocells, and ratio optimization to make durable geopolymers to redirect fly ash and slag for better use. Additionally, we also mentioned the niche approach of using artificial intelligence to understand different types of sand, like calcareous sand to improve how foundations are simulated in coastal environments. Lastly, the importance of discussing health implications concerning construction and demolition waste has also been incorporated as better policies in addressing health concerns surrounding the construction industry can only ensure long term sustainability for those involved in the industry.

Reviewer 4 Report

Comments and Suggestions for Authors

The article offers an ambitious and comprehensive overview of the sustainability challenges in the global sand industry, but several areas could be improved for clarity, depth, and impact.

 

 In the Introduction, while the context and urgency of the sand crisis are well established, the section is lengthy and sometimes repetitive, which could be streamlined to maintain reader engagement; for instance, statistics on global sand use and desert sand limitations could be condensed.

The Sand industry and eco-construction subsection effectively introduces circular economy concepts, yet it would benefit from clearer connections between theory and practical policy examples from different regions.

The Global lack of research on sand is well framed, but the discussion could be strengthened by integrating more quantitative data to support claims about scarcity of research, possibly using bibliometric analysis.

In the Significance and objectives part, the novelty is clear but could be better emphasized by explicitly contrasting the proposed MFA–environment–geopolitics integration with previous fragmented approaches.

Moving into the Methodology, the selection of countries is justified, but the description of inclusion criteria and reliance on gray literature should include a more critical reflection on potential biases and data gaps; diagrams such as Figure 1 are useful, yet the conceptual framework could be more explicitly tied to the research questions.

Overall, each section presents valuable information, but the manuscript would benefit from tighter synthesis, greater use of comparative visuals (maps, normalized graphs), and more explicit linkage between environmental, geopolitical, and economic findings to the proposed sustainability policies.

Author Response

Reviewer 4

The article offers an ambitious and comprehensive overview of the sustainability challenges in the global sand industry, but several areas could be improved for clarity, depth, and impact.

Respected reviewer, we sincerely thank you for your inputs to the manuscript. We understand the need to maintain consistency regarding clarity, depth, and impact and thus have carefully revised the manuscript addressing your comments. Below, each of the comments have been addressed and revised in detail.

In the Introduction, while the context and urgency of the sand crisis are well established, the section is lengthy and sometimes repetitive, which could be streamlined to maintain reader engagement; for instance, statistics on global sand use and desert sand limitations could be condensed.

Thank you for your comment!

We have addressed the issue and shortened the parts mentioned. While we understand that the section is lengthy, we consider it important to highlight the severity of the present state of literature, while also expanding on the ways sand is consumed with no recordkeeping. The problem with sand is rather complex, and we feel the need to elaborate it from as many angles as possible in the introduction as we are aware that not doing so can raise scrutiny over the rest of the manuscript. Additionally, on top of your comment, the section had to be further adjusted to accommodate the reviews given by four other reviewers.

The Sand industry and eco-construction subsection effectively introduces circular economy concepts, yet it would benefit from clearer connections between theory and practical policy examples from different regions.

Thank you for your comment!

In the revised manuscript (Page 19, Line 722-724), recent examples of the innovation in the use of engineered materials, and innovation in design has been highlighted to emphasize the need for more research in the circularity realm. In the conclusion, we have also mentioned that owing to the boom of infrastructure development in the Global South, there is great importance in studying the importance of local materials beyond concrete to improve circularity.

The Global lack of research on sand is well framed, but the discussion could be strengthened by integrating more quantitative data to support claims about scarcity of research, possibly using bibliometric analysis.

Due to the extreme absence of data, sand continues to be particularly difficult to discuss when it comes to the sustainability and circularity of construction materials, given their enormous consumption and frequently limited stock availability. However, resource circularity justifies data-intensive approaches like MFA from a policy standpoint. However, because to the lack of data and its unreliability, as well as the widespread skepticism about it worldwide, relatively few researchers have examined this vital resource. Many scholars have been deterred from continuing their work by these obstacles, which may have otherwise produced a solid foundation for practice and policy. To create a foundational framework for future research, our effort was a purposeful step in this direction by merging the use of quantitative factors with existing qualitative research.

The suggestion made for bibliometric analysis is insightful. However, within the narrative set for this study- which was to frame the discourse on global sand sustainability through the lens of MFA, the bibliometric analysis falls outside the scope of this study. Such an analysis will be suitable for further research done on sand in the future.

In the Significance and objectives part, the novelty is clear but could be better emphasized by explicitly contrasting the proposed MFA–environment–geopolitics integration with previous fragmented approaches.

Thank you for your comment!

In the revised manuscript the existing fragmented work has been supplemented with the understanding that the lack of a combined work that reviewed the global industry from an MFA, environmental issues, and geopolitics point of view that would provide a scholarly picture, albeit incomplete, over what the present sand industry looks like. To be specific, the revision has been reflected in section 1.4 of the revised manuscript.

Moving into the Methodology, the selection of countries is justified, but the description of inclusion criteria and reliance on gray literature should include a more critical reflection on potential biases and data gaps; diagrams such as Figure 1 are useful, yet the conceptual framework could be more explicitly tied to the research questions.

Thank you for your comment!

This concern has been covered with the additions made to sections 2.2.2, with further challenges elaborated in section 2.6. The issue with the availability of data has been highlighted using the case of Canada. Since the data source for Canada was an online website, we noticed the data for 2021 had changed since the last time we worked on the calculations for this manuscript. On top of that, the source where the data was collected for the mass of recycled aggregates was sourced from is not available anymore. Such discrepancies add more difficulty to an already challenging task but the reality of this has been highlighted in the revised manuscript. Please see Page 10, Line 346-350 to see the changes.

Overall, each section presents valuable information, but the manuscript would benefit from tighter synthesis, greater use of comparative visuals (maps, normalized graphs), and more explicit linkage between environmental, geopolitical, and economic findings to the proposed sustainability policies.

Thank you for your comment!

Based upon the insights provided by all five reviewers, the existing research found new avenues to be expanded upon in terms of clarity, and elaboration of challenges faced. The reviewer shall find designated sections that address concerns regarding the methodology, policy implications, and the significance of the study and shall see their comments addressed in these sections.

Reviewer 5 Report

Comments and Suggestions for Authors

Please address the following comments:

1. Please avoid using "we" or "our" in the academic writings.
2. Clear findings should be mentioned in the abstract.
3. The reference within text should be directly cited once mentioning the authors name.
4. Why only the range of the publishes work was 2016-2021?
5. Please change the light colors used in the figures to better ones.
6. Long figure captions should be shortened.
7. Figure 5 can be changed to more representative one.
8. The conclusion is too big and need re-structure.
9. 130 reference in one article is too much and not reasonable.

Author Response

Reviewer 5

Please address the following comments:

Respected reviewer, we thank you for your inputs to the manuscript. Below, each of the comments have been addressed and revised in detail.

1. Please avoid using "we" or "our" in the academic writings.

 

Thank you for your comment. This issue has been addressed across the manuscript and the language has been improved.

 

2. Clear findings should be mentioned in the abstract.

 

Thank you for your comment.

The revised manuscript mentions that the study revealed that China’s consumption of sand surpasses that of all the other countries studied, at 17700 million tonnes, and China has the highest mass of recycled aggregates in us e. Using gross domestic product as a proxy for size of the economy, it was found that China consumed 0.001251 million tonnes of sand per million US Dollars.

 

Please see Page 1, Line 24-28 in the revised manuscript which addressed reviewers comment.

 

3. The reference within text should be directly cited once mentioning the authors name.

 

Thank you for your comment.

We have checked the entire manuscript and have kept it consistent by following the format as stated in the journal guidelines.

 

4. Why only the range of the publishes work was 2016-2021?

 

Thank you for your comment!

This was a rather difficult compromise to come to simply because we were faced with multiple challenges. Firstly, there is no unified database for sand where the data is reported, especially for the extraction, and consumption. Secondly, there is no historical data or a consistent way that countries reported their data. Thirdly, literature preceding the time frame chosen for this study were more focused on the environmental impacts as opposed to how much sand was being extracted. Thus, we chose this time frame as the best compromise as this was the timeframe we could find data for.

 

5. Please change the light colors used in the figures to better ones.

 

Thank you for your comment.

The issue has been addressed for all the figures across the manuscript.

 

6. Long figure captions should be shortened.

Thank you for your comment.

The figure captions have been shortened for ease of reading.

 

7. Figure 5 can be changed to more representative one.

Thank you for your comment!

Upon analyzing the text and the message the authors want to convey, we have opted to remove the figure as we believe the text in the subsection coveys the message appropriately.

 

8. The conclusion is too big and need re-structure.

Thank you for your comment!

In the revised manuscript we have restructured the conclusion to reflect the methodology utilized in this study, key results, predominant research limitations, and future research in the realm of sand sustainability.

 

9. 130 reference in one article is too much and not reasonable.

 

Thank you for your comment! We would love to reduce the number of references.

However, the nature of the article is significantly different than any conventional study or literature review. The scattered nature of the literature as well as the reliance on grey literature to report highlights how fragmented the state of this field is. Thus, we believe the large number of references were necessary to ensure the comprehensiveness of the study since this was an attempt to bring three very different elements about the sand industry in one cohesive picture.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

Your manuscript is now improved and can be published after copy editing. 

Best regards!

Reviewer 3 Report

Comments and Suggestions for Authors

All technical problems have been well solved.