Reducing Atmospheric Pollution as the Basis of a Regional Circular Economy: Evidence from Kazakhstan

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Clearly, I find necessary to send to authors the article in the present form to be rewritten with major changes. The basis for this recommendation are the following: 

I) Lines 15 and 17: the mention of "KPO"  is at least premature here, and the reader can not imagine what KPO means... But if these highlights are translocated after the abstract, in which a first, genuine mention and specification of what means "KPO" the problem would be easily corrected... This first, kinda childish evidence of a lack of organization was a first warn about the general redaction of this article, and I have found many confirmations of it throughout the further reading of the article: in many cases there are evident lack of formality, order and/or internal coherence in the article, which are unacceptable to me.

II) When I find the first evidence of the above mentioned problems in a manuscript, I usually jump directly to a revision of the references part... And I find the treatment of references in this article difficult to be accepted: Authors have chosen to list references in a (sort of) alphabetical order, which is never practical to me, nor editorially mandatory as well.  And, subsequently, the calls of references in the manuscript are defective... For example, in line 56, the first call is naming "Asrar G.R.", but this reference does not exist on the list. To me this error is fatal, and the biunivocal correspondence between calls and the references list is, at least, in jeopardy. Then, the correspondence is not reliable: and one can not be sure if all the called references are in the list, and if all the listed references are properly called! Then I strongly suggest authors: 

i) To list references in the usual numerical way, ordering them                             in the strict order of appearance in the manuscript.

ii) To call the references in the text in the usual, numeric way                                => [X, Y, R-Z], etc.

iii) To write all references obeying the mandatory format for a                              MDPI publication: with a correct use of separators, of signs                              of punctuation, italics and proper abbreviations in the                                      journals part, proper localization of the year after the                                        volume/issue, pagination... Well, I feel authors hardly know                              how to put a reference into proper format for sure, but this                              was not made here in almost any case.

iv) In references, if DOIs (not all active here!) and links refers                            to  a same place in the web, then I find links redundant, then                                 links can be erased in order to avoid more "inflation" in                                    this, yet huge article.

Made these tasks with references, all the pertaining information should be checked as well, making a revision on the surnames of some authors (for example Paretti in line 206, and Turbina in lines 1228-1229) and the general redaction full of mistakes easy to be corrected... Check please, additionally, the proper transliteration of russian texts which shows some inacuracies also...

III) The format of the text should be revised in all the manuscript: for example from line 63 to line 74, the usual format is not respected.

IV) The general, english redaction should be revised because in some cases auxiliary verbs are lacking.

V) As mentioned, the use of italics are lacking... For example, expressions like "et al.", of "per capita" and the journals (in complete or abbreviated form) in references are never written in the proper, mandatory italics... But rarely, italics appear in unexpected parts without purpose (as in line 237, for example).

VI) In figures 1, 5 and 10, there is evident that some I N C O M P L E T E information is displayed, which is the first time I have ever seen in an article in general and in a MDPI article in particular. Obviously unacceptable, these figures should be corrected immediately. In the axis of the rest of the figures are  always lacking the labels and units... Figure 7 is overloaded of information an it is really difficult to discerne the essential info there: to afford a proper presentation of this huge amount of information/results it might be used more tables with specific and explicit information to be orderly discussed.

VII) In table I the independent variables should be assigned to more easily, manageable parameters and not to capitalized names.

In table 2 the units should be revised avoiding the use of periods.

Referring to tables 2 and 3, it is desirable a better, more expliocit mention of the statistical base for these econometric calculations, to justify these large, decimal parts informed as numerical output.

VIII) About results... From lines 710 to 762, and lines 769 to 800, the information of the output is presented, in my opinion, lacking order and organization: even if the formal aspects of the redaction were forgiven (which should not be...) the conceptual aspects are difficult to be followed and rationalized even for a trained reader... As it is involved in this research a doctoral thesis, at least it is mandatory for a posgraduate student to have this critical part properly managed... Many tables have to be included here and all that hanging info written in red might be rationalized and informed in a more proper manner.

Then, I find that a more proper organization of the results, a more clear explanation (beyond some redundant declamation) about the necessary, statistically basis of these econometric studies, and a proper, simpler, spécific and neat formal presentation of observations and research results would base better these raised conclusions of the end of the article. 

 

Comments on the Quality of English Language

English is fine, but some russian transliterations should be revised, anyway. And please make proper use of the auxiliary verbs, some of which are lacking in the text.

Author Response

Comments: The English could be improved to more clearly express the research.

Response: Thank you for your comment. We have sent a letter to the journal's editorial board requesting that the cost of editing the text be included in the article price.

Comments (in table):

Is the content succinctly described and contextualized with respect to previous and present theoretical background and empirical research (if applicable) on the topic? Must be improved

Are the research design, questions, hypotheses and methods clearly stated? Must be improved.

Are the arguments and discussion of findings coherent, balanced and compelling? Must be improved.

For empirical research, are the results clearly presented? Must be improved.

Is the article adequately referenced? Must be improved.

Are the conclusions thoroughly supported by the results presented in the article or referenced in secondary literature? Must be improved.

Response: Your comments regarding the mandatory review questions have been taken into account. The content succinctly described and contextualized with respect to previous and present theoretical background and empirical research on the topic. The main points of the study are systematized. The research questions, hypothesis and research methods have been clarified. The research results have been clarified, references to sources have been checked, and formatted in accordance with recommendations and current requirements.

Comments I: Lines 15 and 17: the mention of "KPO" is at least premature here, and the reader can not imagine what KPO means... But if these highlights are translocated after the abstract, in which a first, genuine mention and specification of what means "KPO" the problem would be easily corrected... This first, kinda childish evidence of a lack of organization was a first warning about the general redaction of this article. I have found many confirmations of it throughout the further reading of the article. In many cases there are evident lack of formality, order and/or internal coherence in the article, which are unacceptable to me.

Response I: We agree with your comment. Accordingly, Highlights are placed after the abstract.

Comments II: When I find the first evidence of the above-mentioned problems in a manuscript, I usually jump directly to a revision of the references part... And I find the treatment of references in this article difficult to be accepted: Authors have chosen to list references in a (sort of) alphabetical order, which is never practical to me, nor editorially mandatory as well.  And, subsequently, the calls of references in the manuscript are defective... For example, in line 56, the first call is naming "Asrar G.R.", but this reference does not exist on the list. To me this error is fatal, and the biunivocal correspondence between calls and the references list is, at least, in jeopardy. Then, the correspondence is not reliable: and one can not be sure if all the called references are in the list, and if all the listed references are properly called! Then I strongly suggest authors: 

1. i) To list references in the usual numerical way, ordering them in the strict order of appearance in the manuscript.
2. ii) To call the references in the text in the usual, numeric way  => [X, Y, R-Z], etc.

 iii) To write all references obeying the mandatory format for a MDPI publication: with a correct use of separators, of signs of punctuation, italics and proper abbreviations in the journals part, proper localization of the year after the volume/issue, pagination... Well, I feel authors hardly know how to put a reference into proper format for sure, but this was not made here in almost any case.

1. iv) In references, if DOIs (not all active here!) and links refers to a same place in the web, then I find links redundant, then links can be erased in order to avoid more "inflation" in this, yet huge article.

Made these tasks with references, all the pertaining information should be checked as well, making a revision on the surnames of some authors (for example Paretti in line 206, and Turbina in lines 1228-1229) and the general redaction full of mistakes easy to be corrected... Check please, additionally, the proper transliteration of russian texts which shows some inacuracies also...

Response II: i),ii) Thank you very much for all the recommendations. We agree with these comments. In accordance with your recommendations, we re-examined the MDPI reference formatting requirements. As a result, all references were edited according to the bibliography and, according to your recommendations, the usual numbering order was used to format the sources, arranging them in the strict order of their appearance in the manuscript.

iii) All references were written in accordance with the mandatory MDPI publication format: with the correct use of separators, punctuation marks, italics and correct abbreviations in the journal part, correct localization of the year after the volume/issue, page numbering.

1. iv) In the references, all DOI pointers were checked for their correctness, and now all are active. Redundant electronic links referring to the same place on the network were removed. The surnames of some authors were revised, for example Papetti, A. [27]. (highlighted in green) [27]. in lines 203-204 (now), Turbina, K.E.; Yurgens, I.Yu, Eds. (highlighted in green) (in lines 1089-1090) (now). In addition, the transliteration of Russian-language texts was carefully checked, in which some inaccuracies were found.

Comments III:  The format of the text should be revised in all the manuscript: for example, from line 63 to line 74, the usual format is not respected.

Response III: Thank you for your comment. We agree with your comment. Therefore, the text format from line 63 to line 76 (now) has been brought into line with the format of the entire article.

Comments IV: The general, english redaction should be revised because in some cases auxiliary verbs are lacking.

Response IV: Thank you for your comment. We have sent a letter to the journal's editorial board requesting that the cost of editing the text be included in the article price.

Comments V: As mentioned, the use of italics are lacking... For example, expressions like "et al.", of "per capita" and the journals (in complete or abbreviated form) in references are never written in the proper, mandatory italics... But rarely, italics appear in unexpected parts without purpose (as in line 237, for example).

Response V: Thank you for your comment, which we agree with. Since all references that comply with the mandatory MDPI publication format have been converted to regular serial numbers, there is no longer any need to use italics such as "et al." Regarding the remaining italics per capita, per unit of GDR, used in the text of the article earlier, for example, lines 137, 406-407,421,435 - the italic format has been changed. This was a technical error, we apologize.

Comments VI: In figures 1, 5 and 10, there is evident that some I N C O M P L E T E information is displayed, which is the first time I have ever seen in an article in general and in a MDPI article in particular. Obviously unacceptable, these figures should be corrected immediately. In the axis of the rest of the figures are  always lacking the labels and units... Figure 7 is overloaded of information an it is really difficult to discerne the essential info there: to afford a proper presentation of this huge amount of information/results it might be used more tables with specific and explicit information to be orderly discussed.

Response VI: Thank you for your comment. We agree with this comment. When forming the diagrams, the figures overlapped each other. Therefore, we made adjustments. Below are figures 1.5. in a corrected form. In addition, in Figure 10 (figure numbering in the previous version), we changed the presentation of the "Matrix" and presented the findings of our study in tabular form, which simplifies its perception and understanding - in the new version of the article, this figure (Figure 10) is reformatted and presented as Table 4 (highlighted in green). All legends to the figures were checked, the description of the indicators was expanded and available for viewing (Figure 1).

Comments VII: In table I the independent variables should be assigned to more easily, manageable parameters and not to capitalized names. In table 2 the units should be revised avoiding the use of periods. Referring to tables 2 and 3, it is desirable a better, more explicit mention of the statistical base for these econometric calculations, to justify these large, decimal parts informed as numerical output.

Response VII: Thank you for your comment. We agree with this comment, all your comments have been taken into account, all variables have been assigned the classical designations generally accepted in econometrics, in particular EMISSIONS 1 =Y1 and so on. Tables 2 and 3 (given below) have also been transformed and presented in the format of econometric calculations (highlighted in green).

Table 2. – Correlation dependence (basic result for Y3).

	Y3	X1	X2	X3	X4	X5	X6
Y3	1
X1	0,381727	1
X2	0,904194	0,029387	1
X3	-0,7176	-0,45938	-0,5966	1
X4	0,131856	0,450074	-0,07479	-0,38974	1
X5	0,303915	0,365131	0,340601	-0,34042	0,060849	1
X6	-0,55713	-0,06261	-0,55508	0,731779	0,100638	-0,20968	1

 

Table 3. – Correlation dependence (accepted result for Y3).

	Y3	X1	X2	X3	X5	X6
Y3	1
X1	0,381727	1
X2	0,904194	0,029387	1
X3	-0,7176	-0,45938	-0,5966	1
X5	0,303915	0,365131	0,340601	-0,34042	1
X6	-0,55713	-0,06261	-0,55508	0,731779	-0,20968	1

Comments VIII: About results... From lines 710 to 762, and lines 769 to 800, the information of the output is presented, in my opinion, lacking order and organization: even if the formal aspects of the redaction were forgiven (which should not be...) the conceptual aspects are difficult to be followed and rationalized even for a trained reader... As it is involved in this research a doctoral thesis, at least it is mandatory for a postgraduate student to have this critical part properly managed... Many tables have to be included here and all that hanging info written in red might be rationalized and informed in a more proper manner. Then, I find that a more proper organization of the results, a more clear explanation (beyond some redundant declamation) about the necessary, statistically basis of these econometric studies, and a proper, simpler, spécific and neat formal presentation of observations and research results would base better these raised conclusions of the end of the article. 

Response VIII: all your comments have been taken into account, all conclusions on econometric testing of the modeling results have been systematized and specified, the main resulting conclusions that are significant for the study have been included (the conclusions have been shortened by about 2 times). (Lines 681-738) (marked in green).

We are grateful to the reviewer for the great work done and valuable comments made to improve the quality of the presented article.

Sincerely, the authors.

 

 

Reviewer 2 Report

Comments and Suggestions for Authors

 

The manuscript explores the environmental impacts of the Karachaganak Petroleum Operating B.V. (KPO) consortium in the West Kazakhstan region. With climate change driving the need for emission reduction, the authors propose that a regional circular economy framework can serve as a model for achieving sustainability. By investigating KPO’s environmental strategies and economic activities, they aim to assess its impact on air quality, resource use, and the potential for a circular economy.

1, It would enhance the paper’s clarity if the authors could add a dedicated subsection or paragraph defining the circular economy within the specific context of the oil and gas industry. This section should not only outline key circular economy principles—such as resource efficiency, waste reduction, and closed-loop production—but also clearly connect these principles to sustainable development goals. By explaining how circular economy practices in oil and gas can contribute to long-term sustainability objectives, the authors would provide readers with a solid foundation for understanding the study’s framework and rationale.

2. The authors are encouraged to expand on their choice of independent and dependent variables, clarifying why certain pollutants and economic indicators were prioritized over others. Beyond presenting the co-variation among variables, it would be helpful to explain the underlying relationships between these indicators. This would guide readers through the logic linking each variable to circular economy goals, adding depth to the analysis and helping readers understand the significance of these variables in relation to sustainable development within the oil and gas sector.

 

3. The analysis would be more robust with comparisons to other developing countries, such as China or Gulf States in Asia, that are also working toward circular economy goals in resource-intensive sectors. Alternatively, the authors could compare KPO’s practices with best practices from similar enterprises in neighboring countries. Such comparisons could highlight regional challenges and opportunities, offering valuable context and insights into how Kazakhstan’s efforts align or differ from global and regional standards.

 

4. To improve the paper’s readability and focus, the authors might consider shortening sections to include only directly relevant evidence. Furthermore, addressing the limitations of the current study would provide a balanced perspective. This discussion could lead into specific recommendations for future research, suggesting areas such as renewable energy adoption, comparative studies across sectors, or longitudinal analyses of circular economy impacts on environmental sustainability.

 

5. To enhance clarity, the authors are advised to simplify complex diagrams and clearly label all figure components. For example, Figure 3 lacks a description of the brown bar, which should be addressed in the legend. Additionally, there is a figure on page 10 with a confusing legend and no caption. If this is intended as a subfigure of Figure 4, it should be clearly labeled and organized accordingly. Streamlining and clarifying visuals would allow readers to interpret data more easily and support the study’s findings more effectively.

Author Response

Comments (in table):

Is the content succinctly described and contextualized with respect to previous and present theoretical background and empirical research (if applicable) on the topic? Can  be improved

Are the research design, questions, hypotheses and methods clearly stated? Can be improved.

Are the arguments and discussion of findings coherent, balanced and compelling? Can be improved.

For empirical research, are the results clearly presented? Can be improved.

Is the article adequately referenced? Can  be improved.

Are the conclusions thoroughly supported by the results presented in the article or referenced in secondary literature? Can be improved.

Response: Your comments regarding the mandatory review questions have been taken into account. The content succinctly described and contextualized with respect to previous and present theoretical background and empirical research on the topic. The main points of the study are systematized. The research questions, hypothesis and research methods have been clarified. The research results have been clarified, references to sources have been checked, and formatted in accordance with the recommendations and current requirements.

In particular, when forming the diagrams, the figures overlapped each other, and therefore adjustments were made. According to your recommendations, to improve the article:

- all references have been checked and revised in accordance with the mandatory MDPI publication format, all DOI references have been checked for activity, and unnecessary references have been removed.

- for a better understanding of the article, figures 4a,b, and 6a,b (in the previous version), which contain a large amount of data, have been divided and presented separately as figures 4, 5, 7, 8 (marked in green).

- according to your recommendations, all variables have been assigned the classical designations generally accepted in econometrics, in particular EMISSIONS 1 = Y1 and further, tables 2 and 3 have also been transformed and presented in the format of econometric calculations. (lines 692-693,704-705). (marked in green).

- all conclusions on the econometric verification of the modeling results are systematized and specified, the main resulting conclusions significant for the study are included (the conclusions are reduced by about 2 times (marked in green).

- in accordance with the recommendations, the conclusions were supplemented with a review of current circular economy practices using the example of China and the Gulf countries in Asia, which are also working to achieve the goals of a circular economy in resource-intensive sectors (marked in green). Lines (58,124-128,238-244)

- to specify the arguments confirming the connection between the principles of a circular economy and the goals of sustainable development, some additional sources are included, for example: lines (259-268,1021-1023,1112-1113) (marked in green).

- the resulting conclusions are added to the conclusion (lines 972-974) (marked in green).

Comments 1: It would enhance the paper’s clarity if the authors could add a dedicated subsection or paragraph defining the circular economy within the specific context of the oil and gas industry. This section should not only outline key circular economy principles—such as resource efficiency, waste reduction, and closed-loop production—but also clearly connect these principles to sustainable development goals. By explaining how circular economy practices in oil and gas can contribute to long-term sustainability objectives, the authors would provide readers with a solid foundation for understanding the study’s framework and rationale.

Response 1: Thank you for your comment. We partially agree with this comment. In response to the reviewer's suggestion to add a special subsection or paragraph defining the circular economy in the specific context of the oil and gas industry, we would like to note the following:

- When developing the study itself, it is supposed to consider the above in interconnection. Thus, in 2.2. Information database (lines 161-162) it is noted that KPO sustainability reports were used;

- on line 152, we added ESG strategies... for greater specificity. (marked in green)

- throughout the text, key principles of the circular economy, such as resource efficiency, waste reduction and closed-loop production are presented in interconnection with the principles of the sustainable development goals, in particular ESG. For example: lines 75-77, 232-236,840-849 (marked in green).

- The work has a special subsection (lines 664-775) 3.5.1. Dependence of pollutant emissions into the atmosphere on "sustainable" measures in KPO for 2012-2022, where specific KPO measures for sustainable development are considered in the context of the formation of a circular economy.

• Along with this, a special column has been added to Table 5 explaining the relationship between the circular economy and sustainable development using the example of key indicators for enterprises in the oil and gas industry. 

  Comments 2: The authors are encouraged to expand on their choice of independent and dependent variables, clarifying why certain pollutants and economic indicators were prioritized over others. Beyond presenting the co-variation among variables, it would be helpful to explain the underlying relationships between these indicators. This would guide readers through the logic linking each variable to circular economy goals, adding depth to the analysis and helping readers understand the significance of these variables in relation to sustainable development within the oil and gas sector.

  Response 2: Thank you for your comment. We agree with this comment, all your comments have been taken into account, all variables have been assigned the classical designations generally accepted in econometrics, in particular EMISSIONS 1 =Y1 and so on. Tables 2 and 3 (given below) have also been transformed and presented in the format of econometric calculations (highlighted in green).

  Table 2.  Correlation dependence (basic result for Y3).

  	Y3	X1	X2	X3	X4	X5	X6
  Y3	1
  X1	0,381727	1
  X2	0,904194	0,029387	1
  X3	-0,7176	-0,45938	-0,5966	1
  X4	0,131856	0,450074	-0,07479	-0,38974	1
  X5	0,303915	0,365131	0,340601	-0,34042	0,060849	1
  X6	-0,55713	-0,06261	-0,55508	0,731779	0,100638	-0,20968	1

   

  Table 3.  Correlation dependence (accepted result for Y3).

  	Y3	X1	X2	X3	X5	X6
  Y3	1
  X1	0,381727	1
  X2	0,904194	0,029387	1
  X3	-0,7176	-0,45938	-0,5966	1
  X5	0,303915	0,365131	0,340601	-0,34042	1
  X6	-0,55713	-0,06261	-0,55508	0,731779	-0,20968	1

   

  Comments 3: The analysis would be more robust with comparisons to other developing countries, such as China or Gulf States in Asia, that are also working toward circular economy goals in resource-intensive sectors. Alternatively, the authors could compare KPO’s practices with best practices from similar enterprises in neighboring countries. Such comparisons could highlight regional challenges and opportunities, offering valuable context and insights into how Kazakhstan’s efforts align or differ from global and regional standards.

  Response 3: We agree with your comment. Initially, in the article we made a comparison with developing countries of Central Asia, which are closest to Kazakhstan in terms of economic structure and environmental conditions. Based on your recommendations, the conclusions of the review of China and the Gulf countries in Asia, which are also working to achieve the goals of a circular economy in resource-intensive sectors, were supplemented (marked in green). For example: Lines 58-59,124-127,238-244,259-268,972-974

  Comments 4:  To improve the paper’s readability and focus, the authors might consider shortening sections to include only directly relevant evidence. Furthermore, addressing the limitations of the current study would provide a balanced perspective. This discussion could lead into specific recommendations for future research, suggesting areas such as renewable energy adoption, comparative studies across sectors, or longitudinal analyses of circular economy impacts on environmental sustainability.

  Response 4: We agree with these comments. All your comments have been taken into account, all conclusions on the econometric verification of the modeling results have been systematized and specified, the main resulting conclusions that are significant for the study have been included (the conclusions have been reduced by about 2 times). (lines 734-751) (marked in green). The paper noted that it is too early to talk about the practical use of renewable energy sources (lines 600-601). In the future, the results of further research will make it possible to create a modern information database of pollutants using GIS technologies to predict the quality of atmospheric air. This study indicates the prospects for similar studies. Thus, comparative studies between sectors or longitudinal analysis of the impact of the closed-loop economy on environmental sustainability can become objects of further research.

  Comments 5: To enhance clarity, the authors are advised to simplify complex diagrams and clearly label all figure components. For example, Figure 3 lacks a description of the brown bar, which should be addressed in the legend. Additionally, there is a figure on page 10 with a confusing legend and no caption. If this is intended as a subfigure of Figure 4, it should be clearly labeled and organized accordingly. Streamlining and clarifying visuals would allow readers to interpret data more easily and support the study’s findings more effectively.

  Response 5: Thank you for your comment. We agree with this comment. When forming the diagrams, the drawings overlapped each other. Therefore, adjustments were made. Below is Figure 3 in an adjusted form.

  Figure 3.  KPO’s contribution to the development of West Kazakhstan Region: main indicators for 2012-2022 Note: compiled according to sources [21,22,23,45].

  In addition, in Fig. 10 (numbering of figures in the previous edition), we changed the presentation of the “Matrix” and presented the findings of our research in tabular form, which simplifies its perception and understanding - in the new edition of the article, this figure has been reformatted and presented in the form of Table 4 (lines 798-800) and some explanations (lines 803-808) (marked in green).

  It should be noted that for better understanding we have divided Figure 4a,b into two Figures 4,5 (lines 416-417,429-430) (marked in green).

  Volumes of pollutant emissions in the Republic of Kazakhstan per unit of GDP, kg/1000 dollars         RK: Gaseous and liquid emissions per unit of GDP, kg/1000 dollars       RK: PM per unit of GDP, kg/1000 dollars     Volumes of pollutants emissions in Western Kazakhstan, kg/1000 dollars         Gaseous and liquid emissions per unit of Western Kazakhstan’s GRP, kg/1000 dollars        PM per unit of Western Kazakhstan’s GRP, kg/1000 dollars      KPO emission level per unit of production, kg/ t        Gaseous and liquid emissions per unit of KPO production, kg/ t        PM per unit of KPO production, kg/ t

  Figure 4. Emissions of main pollutants into the atmosphere per unit of GDP for Kazakhstan, WKR and KPO*, kg/1000 US dollars. Note: compiled according to sources [21,22,44].  

   

   

   

   

  Figure 5.  Emissions of main pollutants into the atmosphere per capita for Kazakhstan, WKR and KPO*, kg/person [21,22,44]

   

   

  We are grateful to the reviewer for the great work done and valuable comments made to improve the quality of the article.

  Sincerely, the authors