Plastic Management and Sustainability: A Data-Driven Study

Round 1

Reviewer 1 Report

The article deals with a topic of high interest. It aims at presenting data and trends on the plastic waste crisis useful for guiding the choices of companies and policy makers. Many data and suggestions are offered. Nevertheless in its present form the article is not as clear and readable as to inform about key tendencies and opportunities in the field of plastic waste management.

The following changes are suggested in order to improve the meaningfulness of the study:

1.      Since analysis of collected data is said to be made in order to reproduce and/or compare with the analysis of three previous studies, an effort should be made to better explain what indicators and information from such studies the authors are reproducing. The statements explaining such a point (see page 4 lines 152-154: “ After the data collection, the data are cleaned and prepared to put the raw data in a structure to extend the analysis made by [24][32][42], where the measures evaluated in these previous studies are re-run in our study with recent data to examine the change and status of the plastic crisis over time.:”) should receive more space and be better clarified

2.       Some clarification should be also offered in the section “6.2. Qualitative analysis methodology”. Figure 1 does not communicate clear information and partially overlaps with table 2.  Titles of columns in figure 2 are not easily readable; for example in the third column data refer to the number of key words or to the number of keywords present in  the abstracts? Also the titles of the fourth and fifth column( “Keywords fulfilling threshold”, “Keywords included Network Diagram”) would benefit from some explanation in the main text.

3.      Some statements such as “This large dataset was collected from various perspectives for this study and future studies related to plastic management and sustainability” are not clear.

4.      A few words should be spent to present the tool used (VOS viewer) to ensure that even the reader who is not fully familiar with it can understand the type of results it allows to obtain. The presentation of the algorithm is made without mentioning how it is developed within VOS viewer. The usual names given to indicators produced by the software (such for example the indicator in step 1 named association strength) are not mentioned.

5.      The article is more a traditional (although using data mining techniques) literature review than a study able to offer updated data and indicators for building policy frameworks. Such a feature should be highlighted.

6.      The discussion of the results and conclusions are disproportionately focused on Industry 4.0 technologies and blockchain technology with too vague clues on how such technologies would help to tackle plastic waste problems. Figure 3, 4 and 5 are partially overlapping and are not useful (at least not all three) to better summarize the results or offer further analysis insights.

7.      Furthermore, the following changes should be made: 1) the goals of the study should be restated consistently with the potential of the methodology used; 2) the presentation of the research plan and methodology should be rewritten in a clearer way; 3) discussion and conclusion should clearly refer to the research’s results and limitations of the study (with respect to the stated objectives) should be discussed. 

Author Response

Dear Esteemed Editor and Reviewers:

We greatly appreciate the instructive and valuable comments raised by the review team and the opportunity for us to revise our paper. Following the review team’s comments and suggestions, we have carefully addressed all the comments and suggestions through this revision. We hope we have revised the manuscript to your satisfaction and hope you will find the revised manuscript acceptable for publication in the Sustainability Journal.

In this response letter, our responses to the review team’s comments are highlighted in BLUE.

For ease of reviewing, the main changes in the manuscript are tracked in BLUE.

Our response to the review team's comments has been provides as follows, which has also been attached in PDF with this submission. 

Authors’ Responses to Reviewer 1’s Comments

We greatly appreciate the time and effort that you have invested in providing us with excellent feedback. We have carefully addressed the comments appropriately in this version as elaborated in our point-to-point response below. We believe that our manuscript has been improved significantly and hope that you could find this revision satisfactory.

The article deals with a topic of high interest. It aims at presenting data and trends on the plastic waste crisis useful for guiding the choices of companies and policy makers. Many data and suggestions are offered. Nevertheless in its present form the article is not as clear and readable as to inform about key tendencies and opportunities in the field of plastic waste management.

The following changes are suggested in order to improve the meaningfulness of the study:

1. Since analysis of collected data is said to be made in order to reproduce and/or compare with the analysis of three previous studies, an effort should be made to better explain what indicators and information from such studies the authors are reproducing. The statements explaining such a point (see page 4 lines 152-154: “ After the data collection, the data are cleaned and prepared to put the raw data in a structure to extend the analysis made by [24][32][42], where the measures evaluated in these previous studies are re-run in our study with recent data to examine the change and status of the plastic crisis over time.:”) should receive more space and be better clarified

Authors’ Response: Thank you very much for this comment. In the revision, more details and discussions are added (lines 179-188 on Page 4) to illustrate more on the measures repeated from these sources. For your review, the following has been added.

To illustrate, considering that the measures of plastic waste were reported in [25] primarily based on data collected in the year 2016, we extend that study with the most recent data to represent plastic waste on the global level until the year 2020 and the plastic waste and combustion in the U.S. until the year 2018 (see Section 7.2.2). In addition, we examine the recycling status in the U.S. following the same method as [35]. Furthermore, [45] presented analysis on plastic generation and production until the year 2015, while further analysis was conducted in Section 7.2.1 to cover the time span until the year 2019; in addition, we enrich the study with projections until the year 2025 following the business as usual scenario, ceteris paribus (i.e., assuming no change in plastic management methods).

2. Some clarification should be also offered in the section “6.2. Qualitative analysis methodology”. Figure 1 does not communicate clear information and partially overlaps with table 2.  Titles of columns in figure 2 are not easily readable; for example in the third column data refer to the number of key words or to the number of keywords present in  the abstracts? Also the titles of the fourth and fifth column( “Keywords fulfilling threshold”, “Keywords included Network Diagram”)would benefit from some explanation in the main text.

Authors’ Response: Following your suggestion, Table. 2 was excluded, and the additional information from the table was stated within the paragraph proceeding Fig. 1, to clarify the methodology followed. We hope the explanation in the text makes it much easier and more precise.

3. Some statements such as “This large dataset was collected from various perspectives for this study and future studies related to plastic management and sustainability” are not clear.

Authors’ Response: This part is related to Table 2 and the comment above. was removed as Table 2 was excluded. In addition,  the lines in the previous manuscript that included that part (Lines 195 to 203), were re-constructed and re-written to increase the clarity. Please check the revised manuscript lines 197 to 218.

4. A few words should be spent to present the tool used (VOS viewer) to ensure that even the reader who is not fully familiar with it can understand the type of results it allows to obtain. The presentation of the algorithm is made without mentioning how it is developed within VOS viewer. The usual names given to indicators produced by the software (such for example the indicator in step 1 named association strength) are not mentioned.

Authors’ Response: In this revision, more details are added under Section 6.2. to illustrate the process with more details about VOSviewer tool and development. Please see the added explanation in Lines 197-209. For your review, the following explanation has been added. In particular, we have also added other explanation on pages 5 - 7.

“  The literature on the plastic crisis was evaluated based on the collection of thousands of abstracts and keywords of 5,267 publications from the Scopus database and then analyzed using the text mining tool VOSviewer (VOS - Visualization of Similarities), which is a two-dimensional visualization software[1]. VOSviewer is an open Natural Language Processing (NLP) library for creating scientific landscape visualizations. The tool enables the development of distance-based maps based on network data on scientific publications from various dimensions (citation, co-occurrence, co-authorship…etc.). The technique upon which the tool is based is composed of the following steps. (a) ‘copy right’ statements in the abstract are removed. (b) sentence detection algorithm splits the abstract into sentences. (c) The ‘part-of-speech’ tagging algorithm is applied to break down the sentence by the verb, adjective, preposition, noun, etc., convert plural to singular terms, and remove the stop words.  Algorithm 1 delineates the process with further details on the clustering technique. For example, in step 1, the similarity matrix is developed based on the co-occurrence matrix, which reflects the association strength. Fig 4 is generated in accordance with Algorithm 1”.

5. The article is more a traditional (although using data mining techniques) literature review than a study able to offer updated data and indicators for building policy frameworks. Such a feature should be highlighted.

Authors’ Response: Thank you very much for your comment. In the revision, we have tried to highlight such features. For example, in Section 6.1. (Quantitative analysis methodology), we claim that “this study is featured with rich data-driven results and interpretation,” which has also been highlighted in the abstract.

6. The discussion of the results and conclusions are disproportionately focused on Industry 4.0 technologies and blockchain technology with too vague clues on how such technologies would help to tackle plastic waste problems. Figure 3, 4 and 5 are partially overlapping and are not useful (at least not all three) to better summarize the results or offer further analysis insights.

 Authors’ Response: Thank you very much for raising the concern. We agree with you. In the revision, we tried our best to make a smooth transition in the discussion. The main reason for us to focus on Industry 4.0 and Blockchain technology is that those are disruptive technology to address the issue of the plastic crisis, and they are promising tools for scholars to bridge the research gap.

For the three figures, thank you for raising this good point. Combining your comment with the opinion suggested by Reviewer 3, in the revision, Fig. 3 was removed, and its insights were added verbally (please see lines 408-411). While Fig 4. (currently Fig 3) was re-designed and adjusted to enhance the readability. Fig 4. (previously Fig 5.) was adjusted and re-developed and re-designed to increase the font size and reflect the main significant clusters instead of displaying the terms over time. In VOSviewer, there is a restriction/limitation on the upper limit of the font size. Accordingly, more insights are added to reflect the takeaway from Fig 4 on pages 8 and 9 (lines 286-317).

7. Furthermore, the following changes should be made: 1) the goals of the study should be restated consistently with the potential of the methodology used; 2) the presentation of the research plan and methodology should be rewritten in a clearer way; 3) discussion and conclusion should clearly refer to the research’s results and limitations of the study (with respect to the stated objectives) should be discussed. 

Authors’ Response:  Thanks for the comments.  Following your comment, we have carefully streamlined the flow in the following sections: Following the Literature Review in Section 2, we provide Problem Statement in section 3; then Section 4 describes the “Objectives, Novelty and Contributions of the Study,” and Section 5 deliberates on the Research Questions. For the research process, we describe the Methodology in Section 6. Our methodology includes quantitative and qualitative analysis, elaborated in Sections 6.1 and 6.2, respectively. For example, on pages 4-6, we describe the data collection and preparation process.

In addressing your comments, more details are added across almost all the sections to follow a smooth flow. For example, the literature review and introduction were enriched and rephrased. Likewise, the discussion and conclusion were adjusted as much as possible. We hope you could find all the revisions satisfactory.   

[1] www.vosviewer.com

Author Response File: Author Response.pdf

Reviewer 2 Report

There are many researches about theoretical evaluation of plastic management and sustainability, especially the the inherent supply chain sustainability. This investigation brings novel and interesting results, but some major adjustments are necessary. Please, find my comments to improve the quality of the manuscript.

1. The novelty and significance of the current study should be given obviously in this paper.

2. In Section 6.2, P6, methods should have complete details about the matrix in eq.1-3, especially the date source. The details of the date are not mentioned detailed.

3. P6. step 3.2 and step 3.3, σ² is not found again, how the calculation result is reflected in the following figure or table, in the results and discuss.

4. The author also need to verify the accuracy of calculation results in this matter, no matter using references or reports.

Author Response

Dear Esteemed Editor and Reviewers:

We greatly appreciate the instructive and valuable comments raised by the review team and the opportunity for us to revise our paper. Following the review team’s comments and suggestions, we have carefully addressed all the comments and suggestions through this revision. We hope we have revised the manuscript to your satisfaction and hope you will find the revised manuscript acceptable for publication in the Sustainability Journal.

In this response letter, our responses to the review team’s comments are highlighted in BLUE.

For ease of reviewing, the main changes in the manuscript are tracked in BLUE.

Our response to the review team's comments has been provides as follows, which has also been attached in PDF with this submission. 

Authors’ Responses to Reviewer 2’s Comments

Thank you for your careful reading of our manuscript. We truly appreciate your valuable feedback and constructive comments. Your professional comments gave us a chance to improve our paper significantly. We have followed your feedback to make this revision accordingly. We hope you are satisfied with our effort and find the revised version acceptable.

There are many researches about theoretical evaluation of plastic management and sustainability, especially the the inherent supply chain sustainability. This investigation brings novel and interesting results, but some major adjustments are necessary. Please, find my comments to improve the quality of the manuscript.

1. The novelty and significance of the current studyshould be given obviously in this paper.

Authors’ Response:  Thanks for the comments.  Following your suggestions, we have carefully addressed the issues in the following sections: Methodology, Objectives, Novelty, and Contributions of the study. In addition, more details are added across almost all the sections. The literature review and introduction were enriched and rephrased. The discussion and conclusion were adjusted as much as possible.

2. In Section 6.2, P6, methods should have complete details about the matrix in eq.1-3, especially the date source. The details of the date are not mentioned detailed.
3. P6. step 3.2 and step 3.3, σ²is not found again, how the calculation result is reflected in the following figure or table, in the results and discuss.

Authors’ Response on the 2^nd and 3^rd comments: Thank you for your comments. σ² is used to explain the algorithm developed by VOSviewer to develop the clustering on the abstracts collected. The primary purpose is to provide a glimpse to readers behind the algorithm used to develop Fig. 4. More details were added on pages 5 and page 7 to increase the clarity for readers. In addition, a reference is added under the algorithm for readers interested in exploring the algorithm behind the tool used.

4. The author also need to verify the accuracy of calculation results in this matter, no matter using references or reports.

Authors’ Response: Thank you for your comment. Per your suggestion, we have double-checked the data sets, resources, and references. The main technical accuracy issue related to this study is the regression report as presented in Figure 5-Global Plastic Production (2015-2019) and Prediction (2020-2025). For this part, we have carefully checked the data used and included the Coefficient of determination to reflect the strength of the model.

Author Response File: Author Response.pdf

Reviewer 3 Report

El-Rayes et al conducted a data-driven study regarding plastic crisis from multiple realistic datasets. I appreciate the authors’ efforts in sorting out tons of data regarding plastic crisis. Overall, the manuscript is well-organized and easy to follow, and some results could have good implications. However, I do have some questions that need to be addressed before publication. Please see my comments below.

Major comments:

1.     In Line 166-168, several publication themes were selected: 'Plastic Business Models,’ 'Plastic and Circular Economy, 'Plastic and Consumers,' ‘Plastic and Closed Loop,’ 'Plastic and Value Chain,’ 'Plastic and Technology.' – it should be six themes, not five, which I believe is a typo. After reading the manuscript, however, it’s not very clear why these themes are chosen and what the connections are between each. In Line 44-61, it looks like that the authors aim to build a connection between different themes, if so, then it would be great to rewrite them (and explain the themes if necessary) to make the connection more closely. Please clarify otherwise.

2.     Line 328-330, suggest using a more constructive sentence and avoid the statement that sounds generic and commonplace. And the same sentence shows in Line 363-365, which seems like a copy and paste – Suggest rewriting them.  Also, why use ‘first’ if there is only one sentence? In addition, in Line 360, the same sentence appears at least twice – it would be great to rewrite it as well.

Minor comments:

1.     Suggest adding some references regarding the relationship between plastic and carbon. For instance, refer to “Stubbins et al (2021). Plastics in the Earth system. Science. DOI: 10.1126/science.abb0354” for plastic-carbon cycle. Also, as mentioned in the abstract “global plastic production is expected to fluctuate between 500-600 18 million metric tons by 2025”, it would be very nice to have some comments on what this means to the future global carbon budget from the management and sustainability perspective in the discussion section.

2.     Line 55 and 61, suggest using consistent quotes, either ‘’ or “”.

3.     Suggest expanding the literature review to include the most recent researches on tackling plastic crisis, including either in laboratory experiments or numerical modeling efforts in Line 84-85. Below are only a few examples.

I.               Refer to “DiBenedetto et al (2023). Microplastics segregation by rise velocity at the ocean surface. Environmental Research Letter. DOI: 10.1088/1748-9326/acb505” for laboratory experiment of microplastic segregation depending on rising velocity. 

II.              Refer to “Liang et al (2021). Including the effects of subsurface currents on buoyant particles in Lagrangian particle tracking models: Model development and its application to the study of riverborne plastics over the Louisiana/Texas shelf. Ocean Modelling. DOI: 10.1016/j.ocemod.2021.101879” for the numerical modeling efforts on prediction of microplastic transport in the US coast.

4.     Line 75 – 76: It’s a bit confusing here by the abbreviation. For instance, what does letter “S” represent in Collect and Dispose (CDS)? What about the last “S” in System Change (SCS)?

5.     Step 3 in Algorithm 1, what is “w.r.t”?

6.     Suggest increasing the font size in Figure 3, 4, and 5. It’s too small to read. 

7.     Line 273-277, suggest give an evidence or reference to support.

8.     In figure 6, it looks like the plastic production projection is based on regression, what is the R value? 

Author Response

Dear Esteemed Editor and Reviewers:

We greatly appreciate the instructive and valuable comments raised by the review team and the opportunity for us to revise our paper. Following the review team’s comments and suggestions, we have carefully addressed all the comments and suggestions through this revision. We hope we have revised the manuscript to your satisfaction and hope you will find the revised manuscript acceptable for publication in the Sustainability Journal.

In this response letter, our responses to the review team’s comments are highlighted in BLUE.

For ease of reviewing, the main changes in the manuscript are tracked in BLUE.

Our response to the review team's comments has been provides as follows, which has also been attached in PDF with this submission. 

Authors’ Responses to Reviewer 3’s Comments

Thank you for your careful reading of our resubmission. We truly appreciate your valuable feedback and constructive comments, in addition to the suggested studies to check. Your professional comments gave us a chance to improve our paper significantly. Thank you for taking the time and effort out of your busy schedule to review the manuscript. As elaborated in our point-to-point response below, we have carefully addressed the comments appropriately in this version. We hope that you find the revised manuscript satisfactory and up to your expectations.

El-Rayes et al conducted a data-driven study regarding plastic crisis from multiple realistic datasets. I appreciate the authors’ efforts in sorting out tons of data regarding plastic crisis. Overall, the manuscript is well-organized and easy to follow, and some results could have good implications. However, I do have some questions that need to be addressed before publication. Please see my comments below.

Major comments:

1. In Line 166-168, several publication themes were selected: ‘Plastic Business Models,’ ‘Plastic and Circular Economy, ‘Plastic and Consumers,’ ‘Plastic and Closed Loop,’ ‘Plastic and Value Chain,’ ‘Plastic and Technology.’ – it should be six themes, not five, which I believe is a typo. After reading the manuscript, however, it’s not very clear why these themes are chosen and what the connections are between each. In Line 44-61, it looks like that the authors aim to build a connection between different themes, if so, then it would be great to rewrite them (and explain the themes if necessary) to make the connection more closely. Please clarify otherwise.

Authors’ Response : Thank you for raising this good point. Actually, six themes were reduced to five after deciding to evaluate the ‘Technology’ theme through the lens of the other themes since the publications retrieved based on ‘plastic’ & ’technology’ returned very generic publications. Accordingly, in the revised manuscript, this part was rewritten to merge the lines that state five out of six themes are included to avoid confusion.  This explanation has been added in Lines 216-218. Thank you for pointing that part out.

For your comment on building a connection between different themes, we have tried to add some discussions in the revision. Please see the added discussion in Lines 211-216. 

2. Line 328-330, suggest using a more constructive sentence and avoid the statement that sounds generic and commonplace. And the same sentence shows in Line 363-365, which seems like a copy and paste – Suggest rewriting them.  Also, why use ‘first’ if there is only one sentence? In addition, in Line 360, the same sentence appears at least twice – it would be great to rewrite it as well.

 Authors’ Response:  Done. Both parts are updated.

Minor comments:

1. Suggest adding some references regarding the relationship between plastic and carbon. For instance, refer to “Stubbins et al (2021). Plastics in the Earth system. Science. DOI: 10.1126/science.abb0354” for plastic-carbon cycle. Also, as mentioned in the abstract “global plastic production is expected to fluctuate between 500-600 18 million metric tons by 2025”, it would be very nice to have some comments on what this means to the future global carbon budget from the management and sustainability perspective in the discussion section.
2. Line 55 and 61, suggest using consistent quotes, either ‘’ or “”.

Authors’ Response: done, thank you for pointing that out.

3. Suggest expanding the literature review to include the most recent researches on tackling plastic crisis, including either in laboratory experiments or numerical modeling efforts in Line 84-85. Below are only a few examples.
4. Refer to “DiBenedetto et al (2023). Microplastics segregation by rise velocity at the ocean surface. Environmental Research Letter. DOI: 10.1088/1748-9326/acb505” for laboratory experiment of microplastic segregation depending on rising velocity. 
5. Refer to “Liang et al (2021). Including the effects of subsurface currents on buoyant particles in Lagrangian particle tracking models: Model development and its application to the study of riverborne plastics over the Louisiana/Texas shelf. Ocean Modelling. DOI: 10.1016/j.ocemod.2021.101879” for the numerical modeling efforts on prediction of microplastic transport in the US coast.

Authors’ Response: Thank you so much for suggesting and recommending the three interesting studies by Stubbins et al., DiBenedetto et al., and Lian et al. The three studies were checked carefully and included in our study under the introduction and literature review to enrich and support the other references included.

4. Line 75 – 76: It’s a bit confusing here by the abbreviation. For instance, what does letter “S” represent in Collect and Dispose (CDS)? What about the last “S” in System Change (SCS)?

Authors’ Response: Thank you for raising that comment. In the literature review, we used the same abbreviations used by the authors Lau et al. since we are referring to their results. But since the abbreviations are confusing, we replaced them with the whole term, as reflected in lines 82-90.

2020. W. Lau et al., “Evaluating scenarios toward zero plastic pollution,” Science, vol. 369, no. 6510, pp. 1455–1461, 2020.
2021. Step 3 in Algorithm 1, what is “w.r.t”?

Authors’ Response: done; the abbreviation is replaced with the complete statement (with respect to).

6. Suggest increasing the font size in Figure 3, 4, and 5. It’s too small to read. 

Authors’ Response: Thank you for raising this good point. Combining your comment with the opinion of the other reviewer. Fig 3. was removed, and the insights from it were added. While fig 4 (currently Fig 3) was redesigned and adjusted to enhance readability. Fig 4. (previously Fig 5.) was adjusted to increase the font size. There is a restriction/limitation on the upper limit of the font size as it is created using VOSViewer Tool; but we did our best to increase the clarity of the chart.

7. Line 273-277, suggest give an evidence or reference to support.

Authors’ Response: Thank you for your comment; that part was addressed with relevant references added to support it.

8. In figure 6, it looks like the plastic production projection is based on regression, what is the R value? 

Authors’ Response: Thank for bringing up the issue. The Coefficient of determination is now added on the chart. Its value is .96

Author Response File: Author Response.pdf

Reviewer 4 Report

The paper can be accepted in current form. 

Round 2

Reviewer 1 Report

The scant changes provided do not correct the weaknesses previously highlighted.

Author Response

Authors’ Responses to Reviewer 1’s Comments

We apologize that our previous revision had not made it acceptable to you. We have revisited your comments carefully and tried our best with this revision. We would be happy to reflect on any changes needed if more comments or suggestions are provided.

Authors’ Responses to Reviewer 1’s Comments

We greatly appreciate the time and effort that you have invested in providing us with excellent feedback. We have carefully addressed the comments appropriately in this version as elaborated in our point-to-point response below. We believe that our manuscript has been improved significantly and hope that you could find this revision satisfactory.

The article deals with a topic of high interest. It aims at presenting data and trends on the plastic waste crisis useful for guiding the choices of companies and policy makers. Many data and suggestions are offered. Nevertheless in its present form the article is not as clear and readable as to inform about key tendencies and opportunities in the field of plastic waste management.

The following changes are suggested in order to improve the meaningfulness of the study:

1. Since analysis of collected data is said to be made in order to reproduce and/or compare with the analysis of three previous studies, an effort should be made to better explain what indicators and information from such studies the authors are reproducing. The statements explaining such a point (see page 4 lines 152-154: “ After the data collection, the data are cleaned and prepared to put the raw data in a structure to extend the analysis made by [24][32][42], where the measures evaluated in these previous studies are re-run in our study with recent data to examine the change and status of the plastic crisis over time.:”) should receive more space and be better clarified

Authors’ Response: Thank you very much for this comment. In the revision, we have almost rewritten the first paragraph of Section 6.1. In particular, more details and discussions are added to illustrate more on the measures repeated from these sources. For your review, the following has been added.

“To fulfill the objectives of the study and build on the previous analysis [26] [36] [46], most of the analyses on these sources return to the year 2016 and earlier. Secondary da-ta is collected from various sources to run the descriptive and predictive analysis (see Table 1 for the list of the dataset used). For the datasets that were not found publicly, we communicated with the State Department to gain access to the data collected be-tween 2016-2021 (approximately a total of one million records). After the data collec-tion, the datasets are cleaned and prepared to put the raw data in a structure to extend the analysis made by [26], [36], [46], where the measures evaluated in these previous studies are re-run in our study with recent data to examine the change and status of the plastic crisis over time. To illustrate, considering that the measures of plastic waste were reported in [26] primarily based on data collected in the year 2016, we extend that study with the most recent data to represent plastic waste on the global level until the year 2020 and the plastic waste and combustion in the U.S. until the year 2018 (see Sec-tion 7.2.2). In addition, we examine the recycling status in the U.S. following the same method as [36]. Furthermore, [46] presented analysis on plastic generation and produc-tion until the year 2015, while further analysis was conducted in Section 7.2.1 to cover the time span until the year 2019; in addition, we enrich the study with projections un-til the year 2025 following the business as usual scenario, ceteris paribus (i.e., assuming no change in plastic management methods).

2. Some clarification should be also offered in the section “6.2. Qualitative analysis methodology”. Figure 1 does not communicate clear information and partially overlaps with table 2.  Titles of columns in figure 2 are not easily readable; for example in the third column data refer to the number of key words or to the number of keywords present in  the abstracts? Also the titles of the fourth and fifth column( “Keywords fulfilling threshold”, “Keywords included Network Diagram”)would benefit from some explanation in the main text.

Authors’ Response: Following your suggestion, to make it more readable and crystal clear, we have revised Section 6.2 carefully. In particular, Table. 2 was excluded, and the additional information from the table was stated within the paragraph proceeding Fig. 1, to clarify the methodology followed. We hope the explanation in the text makes it much easier and more precise.

3. Some statements such as “This large dataset was collected from various perspectives for this study and future studies related to plastic management and sustainability” are not clear.

Authors’ Response: This part is related to Table 2 in the original version. Since Table 2 was excluded, such concern is vanished. In addition,  the lines in the previous manuscript that included that part (Lines 195 to 203), were re-constructed and re-written to increase the clarity. Please check the restructured content in the revised manuscript.

4. A few words should be spent to present the tool used (VOS viewer) to ensure that even the reader who is not fully familiar with it can understand the type of results it allows to obtain. The presentation of the algorithm is made without mentioning how it is developed within VOS viewer. The usual names given to indicators produced by the software (such for example the indicator in step 1 named association strength) are not mentioned.

Authors’ Response: In this revision, more details are added under Section 6.2. to illustrate the process with more details about VOSviewer tool and development. Please see the added explanation in Lines 199-213. For your review, the following explanation has been added. In particular, we have also added other explanation on pages 5 - 7.

  “The literature on the plastic crisis was evaluated based on the collection of thousands of abstracts and keywords of 5,267 publications from the Scopus database and then analyzed via VOSviewer tool (VOS - Visualization of Similarities), which is a two-dimensional visualization software . VOSviewer is an open Natural Language Processing (NLP) library for creating scientific landscape visualizations. The tool enables the development of distance-based maps based on network data on scientific publications from various dimensions (citation, co-occurrence, co-authorship…etc.). The technique upon which the tool is based is composed of the following steps. (a) ‘copy right’ statements in the abstract are eliminated. (b) sentence detection algorithm splits the abstract into sentences. (c) ‘part-of-speech’ tagging algorithm is applied to break down the sentence into fragments (i.e., verb, adjective, preposition, noun, etc.). (d) convert plural to singular terms. (e) finally, remove the stop words.  Our algorithm is presented after Fig. 1.  It delineates the process with further details on the clustering technique. For example, in Step 1, the similarity matrix is developed based on the co-occurrence matrix, which reflects the association strength. Fig 4 is generated in accordance with the clustering”.

5. The article is more a traditional (although using data mining techniques) literature review than a study able to offer updated data and indicators for building policy frameworks. Such a feature should be highlighted.

Authors’ Response: Thank you very much for your comment. In the revision, we have tried to highlight such features. For example, in Section 6.1. (Quantitative analysis methodology), we claim that “this study is featured with rich data-driven results and interpretation,” which has also been highlighted in the abstract.

6. The discussion of the results and conclusions are disproportionately focused on Industry 4.0 technologies and blockchain technology with too vague clues on how such technologies would help to tackle plastic waste problems. Figure 3, 4 and 5 are partially overlapping and are not useful (at least not all three) to better summarize the results or offer further analysis insights.

 Authors’ Response: Thank you very much for raising the concern. We agree with you. In the revision, we tried our best to make a smooth transition in the discussion. The main reason for us to focus on Industry 4.0 and Blockchain technology is that those are disruptive technology to address the issue of the plastic crisis, and they are promising tools for scholars to bridge the research gap.

For the three figures, thank you for raising this good point. Combining your comment with the opinion suggested by Reviewer 3, in the latest revision, Fig. 3 was removed, and its insights were added with narratation. While Fig 4. (currently Fig 3) was re-designed and adjusted to enhance the readability. Fig 4. (previously Fig 5.) was adjusted and re-developed and re-designed to increase the font size and reflect the main significant clusters instead of displaying the terms over time. In VOSviewer, there is a restriction/limitation on the upper limit of the font size. Accordingly, more insights are added to reflect the takeaway from Fig 4 on pages 8 and 9. We hope you find this revision acceptable.

7. Furthermore, the following changes should be made: 1) the goals of the study should be restated consistently with the potential of the methodology used; 2) the presentation of the research plan and methodology should be rewritten in a clearer way; 3) discussion and conclusion should clearly refer to the research’s results and limitations of the study (with respect to the stated objectives) should be discussed. 

Authors’ Response:  Thanks for the comments.  Following your comment, we have carefully streamlined the flow in the following sections: Following the Literature Review in Section 2, we provide Problem Statement in Section 3; then in Section 4 we describe the “Objectives, Novelty and Contributions of the Study,” and Section 5 deliberates on the Research Questions. For the research process, we describe the Methodology in Section 6. Our methodology includes quantitative and qualitative analysis, elaborated in Sections 6.1 and 6.2, respectively. For example, on pages 4-6, we describe the data collection and preparation process.

In addressing your comments, more details are added across almost all the sections to follow a smooth flow. For example, the literature review and introduction were enriched and rephrased. Likewise, the discussion and conclusion were adjusted as much as possible.  Thank you again for helping us nesting the content flow. We hope you could find all the revisions satisfactory.   

Reviewer 2 Report

 I am satisfied with the author's response to my questions.

Author Response

We greatly appreciate the time and effort that you spent reviewing the modified manuscript. We are pleased to know the manuscript is a satisfactory and up to your expectations.

Reviewer 3 Report

I really appreciate the authors’ efforts to answer my questions. Overall, the majority of the comments have been addressed successfully, with only a few (listed below) that might need a little attention before publication.

1.     Line 19: Suggest removing the space after the first paragraph to merge both into one. There is no need to make two paragraphs in the abstract as the key points are connected in both. Also, I would suggest to avoid using the two “furthermore” in Line 20 and 21 to make the reading smoothly.

2.     Since this is a data-driven study, in particular, please use caution to check all the references and how they are referred to. For instance, the hyperlinks in reference (44), (49), (50), (52) are not working. Liang et al. (2021) is not shown in the reference list as mentioned in the response to previous comment.

Also, it might be useful to add both Stubbins et al. (2021) and Liang et al. (2021) to Line 35-36 ‘the low density of plastics lead to long-span transportation’, which are supported by both studies. In fact, the plastic pollution crisis in the U.S. is mentioned specifically in section 3 (Line 130-131), studies that focus on this topic (like where the plastics ended up in the US) are encouraged to cover.

Line 52-53: suggest to expand this sentence a little bit to highlight the necessity of studying microplastics in the marine environment, which also enhances the importance of this study and connects the key point in the next paragraph. Just as an example, “Microplastic degradation and their transport and fate in the marine environment, as part of their life-cycle, are still poorly understood”.

Liang et al. (2021) highlighted how the fates and destinations of river-borne microplastics are related to the rising speed of microplastics in the marine environment (such as beaching the US coast) from the modeling perspective, and DiBenedetto et al. (2023) also demonstrated the importance of rising speed of microplastic in their vertical distribution in the water column, which depends the density of microplastics, from the laboratory perspective.

3.     In Line 206, it’s a bit confusing at the first glance Algorithm “1” – it sounds like there are other algorithms but it turns out this is the only one.

4.     Line 251, ‘.’ Should appear at the end -> ‘Re-purpose’. Same as ‘re-design’. Just spend a little time checking all these would make the paper nice and neat :)

5.     Figure 3, use a different color for the topics like ‘Fintech’, ‘Environment’ to make it easy to distinguish. Otherwise, the readers need time to recognize that the outer circle indicates time, then inside for number of publications, and then topics. In fact, Figure 6 is a very nice example to follow, which is easy to read.

Author Response

Authors’ Responses to Reviewer 3’s Comments

We greatly appreciate the time and effort that you have invested in providing us with excellent feedback in the second round of reviews. Your professional comments gave us a chance to improve our paper. We have carefully addressed the comments appropriately in this version, as elaborated in our point-to-point response below. We believe that our manuscript has been improved and hope you can find this revision satisfactory and acceptable.

I really appreciate the authors’ efforts to answer my questions. Overall, the majority of the comments have been addressed successfully, with only a few (listed below) that might need a little attention before publication.

1. Line 19: Suggest removing the space after the first paragraph to merge both into one. There is no need to make two paragraphs in the abstract as the key points are connected in both. Also, I would suggest to avoid using the two “furthermore” in Line 20 and 21 to make the reading smoothly.

Authors’ Response: Thank you for raising this point. In the revision, the two paragraphs are merged into one paragraph, and the two ‘furthermore’ were removed as suggested to make the flow smooth.

2. Since this is a data-driven study, in particular, please use caution to check all the references and how they are referred to. For instance, the hyperlinks in reference (44), (49), (50), (52) are not working. Liang et al. (2021) is not shown in the reference list as mentioned in the response to previous comment.

Also, it might be useful to add both Stubbins et al. (2021) and Liang et al. (2021) to Line 35-36 ‘the low density of plastics lead to long-span transportation’, which are supported by both studies. In fact, the plastic pollution crisis in the U.S. is mentioned specifically in section 3 (Line 130-131), studies that focus on this topic (like where the plastics ended up in the US) are encouraged to cover.

Authors’ Response:  Done. We checked the hyperlinks in the footnote and the references. In addition, per your comment, both Stubbins et al. and Liang et al. have been added. We used that reference the last time, but most probably, Zotero did not update the final list to include it properly. So the whole list is checked manually.

In addition, All the links in the footnote would link the readers automatically. We added ‘www.’ Before each URL and tested, it is working.

However, the URL links in the references list must be copied and pasted by the readers in their browsers. Making the links interactive through the references will distort the references list as it is added automatically by Zotero references manager tool. Therefore, we copied and pasted each URL in the reference into another browser window to ensure it was working correctly.

Line 52-53: suggest to expand this sentence a little bit to highlight the necessity of studying microplastics in the marine environment, which also enhances the importance of this study and connects the key point in the next paragraph. Just as an example, “Microplastic degradation and their transport and fate in the marine environment, as part of their life-cycle, are still poorly understood”.

Liang et al. (2021) highlighted how the fates and destinations of river-borne microplastics are related to the rising speed of microplastics in the marine environment (such as beaching the US coast) from the modeling perspective, and DiBenedetto et al. (2023) also demonstrated the importance of rising speed of microplastic in their vertical distribution in the water column, which depends the density of microplastics, from the laboratory perspective.

Authors’ Response: Thank you so much for your addition! The lines you mentioned above were included in lines  54 to 59. For your reference, the following has been added.

“Until recently, Liang et al. highlighted how the fates and destinations of river-borne microplastics are related to the rising growth of microplastics in the marine environ-ment (such as the beaches across the U.S. coast) from the modeling perspective [13]. In addition, DiBenedetto et al. also demonstrated the importance of rising speed of micro-plastic in their vertical distribution in the water column, which depends on the density of micro-plastics, from the laboratory perspective [27].”

3. In Line 206, it’s a bit confusing at the first glance Algorithm “1” – it sounds like there are other algorithms but it turns out this is the only one.

Authors’ Response: Thank you for raising this point. Without the index, “Algorithm 1: Terms Clustering and Mapping” is changed to “Algorithm: Terms Clustering and Mapping”. We have also updated the reference to the algorithm accordingly.

4. Line 251, ‘.’ Should appear at the end -> ‘Re-purpose’. Same as ‘re-design’. Just spend a little time checking all these would make the paper nice and neat :)

Authors’ Response: done, thank you for pointing that out. The whole document was checked carefully to ensure consistency. Any term between single quotations was changed to italic. In addition, all the initial letters after a comma were re-written in lower case (except for technologies, which were kept in upper case). Finally, we also follow Grammarly app to make editorial corrections andchanges throughout the paper.

5. Figure 3, use a different color for the topics like ‘Fintech’, ‘Environment’ to make it easy to distinguish. Otherwise, the readers need time to recognize that the outer circle indicates time, then inside for number of publications, and then topics. In fact, Figure 6 is a very nice example to follow, which is easy to read.

 Authors’ Response: Thank you for the suggestion. Figure 3 colors are adjusted to make it easier to read.