Economy-Wide Material Flow Accounting: Application in the Italian Glass Industry

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study presents a comprehensive application of Economy-Wide Material Flow Accounting (EW-MFA) in the Italian glass industry, utilizing the STAN software to analyze material flows from raw material extraction to end-of-life stages. The research is well-structured and aligns with current sustainability goals, providing valuable insights into resource efficiency and environmental impacts. However, some areas require clarification, methodological refinement, and additional context to enhance the study's robustness and applicability.

 

Detailed Comments

 

1. Methodological Transparency

1.1 Data Sources: While Assovetro and EUROSTAT are cited, clarify how data gaps (e.g., 2021 emissions estimated from 2020) were addressed. Provide sensitivity analysis to justify assumptions.

1.2 STAN Software: Elaborate on how STAN handles data inconsistencies or uncertainties (e.g., error margins, confidence intervals). The mention of "normal distribution" assumptions needs justification.

1.3 Temporal Data Misalignment: Address how using 2020 data for 2021 projections might skew results. Recommend future studies prioritize concurrent data collection.

 

2. Results and Discussion

2.1 Contextualize Findings: Compare the Italian glass industry's material flows/emissions with other EU nations or global benchmarks to highlight relative performance.

2.2 Recycling Rates: The 30-35% recycling rate for container glass seems low compared to EU averages (e.g., 74% in 2020). Discuss reasons for this disparity and potential improvements.

2.3 Emission Reduction: The suggestion to "develop new glass compositions" is vague. Cite specific innovations (e.g., low-melting-point glass) or ongoing research.

2.4 Social/Health Impacts: Acknowledge the lack of social dimensions (e.g., labor conditions in mining/recycling) as a limitation, per the conclusion’s self-identified gap.

 

Minor Revisions

Figure 1: Ensure all labels (e.g., "23.1 Fabrication of flat glass") are legible and axes are clearly described.

Table 1: Clarify units (e.g., "DE eq." vs. "IM eq.") and reconcile discrepancies (e.g., "negligible" imports for limestone vs. detailed calculations elsewhere).

Ensure all citations (e.g., "Solvay (2022)") are in the reference list.

 

Comments on the Quality of English Language

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

Author Response

Reviewer 1

This study presents a comprehensive application of Economy-Wide Material Flow Accounting (EW-MFA) in the Italian glass industry, utilizing the STAN software to analyze material flows from raw material extraction to end-of-life stages. The research is well-structured and aligns with current sustainability goals, providing valuable insights into resource efficiency and environmental impacts. However, some areas require clarification, methodological refinement, and additional context to enhance the study's robustness and applicability.

Detailed Comments

1. Methodological Transparency

• Data Sources: While Assovetro and EUROSTAT are cited, clarify how data gaps (e.g., 2021 emissions estimated from 2020) were addressed. Provide sensitivity analysis to justify assumptions.

RESPONSE: Unfortunately, comprehensive data from 2021 were not always available. We filled the gaps with data from 2020 as now stated in the text. We would like to underline that the paper experiment the EW-MFA on the glass sector in Italy and it is one of the first of its kind, while we also want to express with the research the need for more data to enrich transparency not only of our results but also of the sector itself.

• STAN Software: Elaborate on how STAN handles data inconsistencies or uncertainties (e.g., error margins, confidence intervals). The mention of "normal distribution" assumptions needs justification.

RESPONSE: Done

• Temporal Data Misalignment: Address how using 2020 data for 2021 projections might skew results. Recommend future studies prioritize concurrent data collection.

RESPONSE: We recommended for future studies to prioritize current data, even if we tried to do so and we evidence lack of data

 

1. Results and Discussion

2.1 Contextualize Findings: Compare the Italian glass industry's material flows/emissions with other EU nations or global benchmarks to highlight relative performance.

RESPONSE: Data from EU and global context added across the text

2.2 Recycling Rates: The 30-35% recycling rate for container glass seems low compared to EU averages (e.g., 74% in 2020). Discuss reasons for this disparity and potential improvements.

RESPONSE: The percentage is referred to the global level of recycling. We added this room for improvement again in the conclusions.

2.3 Emission Reduction: The suggestion to "develop new glass compositions" is vague. Cite specific innovations (e.g., low-melting-point glass) or ongoing research.

RESPONSE: done

2.4 Social/Health Impacts: Acknowledge the lack of social dimensions (e.g., labor conditions in mining/recycling) as a limitation, per the conclusion’s self-identified gap.

RESPONSE: Done

 

Minor Revisions

Figure 1: Ensure all labels (e.g., "23.1 Fabrication of flat glass") are legible and axes are clearly described.

RESPONSE: L 119 - 123 axis is described plus High resolution Figure 1 has been uploaded to ensure all the labels are legible

Table 1: Clarify units (e.g., "DE eq." vs. "IM eq.") and reconcile discrepancies (e.g., "negligible" imports for limestone vs. detailed calculations elsewhere).

RESPONSE: Units clarified. Negligible is referred to the low rate of import for limestone, so it is considered 100% internal.

Ensure all citations (e.g., "Solvay (2022)") are in the reference list.

RESPONSE: Done, it was a footnote

Reviewer 2 Report

Comments and Suggestions for Authors

This study aims to assess the material flow and environmental impact of the Italian glass industry using Economy-Wide Material Flow Accounting (EW-MFA) through the STAN software. It seeks to identify key stages in glass production, quantify resource use and waste generation, and evaluate recycling performance, ultimately supporting sustainable resource management and informing policymakers and industry leaders in enhancing sustainability practices. We recommend a major revision to address several critical areas:

1. Please make the abstract clearer (explain the results in form of percentages and numbers).
2. Sorry, the introduction section did not adequately support or clearly explain the framework of the glass industry.
3. The study mentions the use of the EW-MFA framework and STAN software for material flow analysis, yet it does not clearly justify the choice of this method over other potential tools or frameworks. Could the authors elaborate on why EW-MFA and STAN were selected and how their use ensures reliability and replicability in the context of the Italian glass industry?
4. Revise “To figure out the yield of the calcination process, considerations about the molecular weights, lead to a 56,03% as the yield of the process. Finally, considering the dual yields from limestone extraction through to the final production of calcium oxide (CaO) and focusing on the calcium oxide required for the 2021 production, while considering the imported quantity of limestone irrelevant, makes possible to decide the desired value of limestone extraction and import.” On page 12 (too general and long).
5. Move all links and its citations for the last of the manuscript.
6. Sorry, the caption of figure 4 is incorrect.
7. The manuscript contains excessive abbreviations. Only the necessary ones should be retained.
8. Sorry revise the captions of all figures.
9. The conversion of energy units from Tons of Oil Equivalent (TOE) to tons of electricity is central to the MF.4 calculations. Could the authors clarify and justify the specific conversion factors used in these transformations, particularly in Table 1? How do these factors reflect Italy’s actual energy mix in 2021, and how sensitive are the results to variations in these conversion rates?
10. Compare the results to contemporary work in a separate section, namely, comparison to contemporary work.
11. The methodology assumes that emissions to air, water, and waste disposal from the glass industry are proportionally estimated from national figures. Could the authors provide more detail on how the proportion attributable to the glass sector was calculated (e.g., for the 637,330.8 tons of water emissions)? What were the allocation principles or coefficients, and how do they reflect sector-specific processes?
12. The conclusion is too general; please indicate the role of each additive and curing condition for the prepared samples.

Author Response

This study aims to assess the material flow and environmental impact of the Italian glass industry using Economy-Wide Material Flow Accounting (EW-MFA) through the STAN software. It seeks to identify key stages in glass production, quantify resource use and waste generation, and evaluate recycling performance, ultimately supporting sustainable resource management and informing policymakers and industry leaders in enhancing sustainability practices. We recommend a major revision to address several critical areas:

Please make the abstract clearer (explain the results in form of percentages and numbers).

RESPONSE:    L 24- 31 findings has been mentioned

Sorry, the introduction section did not adequately support or clearly explain the framework of the glass industry.

RESPONSE: L 53-56, L 79-83 the revised Introduction now gives a fully referenced snapshot of the Italian glass value-chain production volumes, corporate structure, energy and emission intensity, and circularity status before we introduce the OECD/Eurostat EW-MFA methodology.

The study mentions the use of the EW-MFA framework and STAN software for material flow analysis, yet it does not clearly justify the choice of this method over other potential tools or frameworks. Could the authors elaborate on why EW-MFA and STAN were selected and how their use ensures reliability and replicability in the context of the Italian glass industry?

RESPONSE: Done in the text: EW-MFA was chosen as the EU’s standard framework for tracking material flows, ensuring policy relevance and comparability across sectors. STAN was used for its robust data reconciliation and uncertainty handling, allowing mass balance consistency and replicable results despite data gaps.

Revise “To figure out the yield of the calcination process, considerations about the molecular weights, lead to a 56,03% as the yield of the process. Finally, considering the dual yields from limestone extraction through to the final production of calcium oxide (CaO) and focusing on the calcium oxide required for the 2021 production, while considering the imported quantity of limestone irrelevant, makes possible to decide the desired value of limestone extraction and import.” On page 12 (too general and long).

RESPONSE: This part has been revised with more clarity L 349-352

Move all links and its citations for the last of the manuscript.

RESPONSE: Done

Sorry, the caption of figure 4 is incorrect.

RESPONSE: Done

The manuscript contains excessive abbreviations. Only the necessary ones should be retained.

RESPONSE: EEA, TMI, TMC, TMR from have been removed.

Sorry revise the captions of all figures.

RESPONSE: Done

The conversion of energy units from Tons of Oil Equivalent (TOE) to tons of electricity is central to the MF.4 calculations. Could the authors clarify and justify the specific conversion factors used in these transformations, particularly in Table 1? How do these factors reflect Italy’s actual energy mix in 2021, and how sensitive are the results to variations in these conversion rates?

RESPONSE: That was a mistake in terms of words used, we meant just tons (mass) equivalent to produce the same amount of electricity. The source used for conversion has been now cited.

Compare the results to contemporary work in a separate section, namely, comparison to contemporary work.

RESPONSE: To the best of the author knowledge, there are no other contributions that analyse the Italian glass sector using the EW-MFA

The methodology assumes that emissions to air, water, and waste disposal from the glass industry are proportionally estimated from national figures. Could the authors provide more detail on how the proportion attributable to the glass sector was calculated (e.g., for the 637,330.8 tons of water emissions)? What were the allocation principles or coefficients, and how do they reflect sector-specific processes?

RESPONSE: We relied on data form Assovetro for the estimation of Glass industry emissions, and Ispra for the total emissions at national level. It is now mentioned in the text.

 

The conclusion is too general; please indicate the role of each additive and curing condition for the prepared samples.

RESPONSE: Can you please clarify your suggestion, as we did not prepared samples. We restructured the conclusion as for the other reviewers, too. We hope they are better now

Reviewer 3 Report

Comments and Suggestions for Authors

The abstract is incomplete and should not begin with the word "with," which is technically incorrect. Additionally, the background of the study is missing from the abstract.

The quality of the figure captions and the visuals is quite poor; improvements are needed in both areas.

The results and discussion sections are insufficient and do not meet the journal's quality standards.

The English language used in this article is weak and fails to meet the necessary standards for publication.

Additionally, the conclusion is poorly written and does not effectively summarize the main findings and overview of the study.

The complete article needs to be rewritten to align with journal standards while incorporating all feedback provided.

Comments on the Quality of English Language

Requires strong improvement

Author Response

The abstract is incomplete and should not begin with the word "with," which is technically incorrect. Additionally, the background of the study is missing from the abstract.

RESPONSE: Now the abstract no longer starts with “With”. We inserted a concise background sentence that frames the study’s importance in the European context L 12-13

The quality of the figure captions and the visuals is quite poor; improvements are needed in both areas.

RESPONSE: Done

The results and discussion sections are insufficient and do not meet the journal's quality standards.

RESPONSE: Results and Discussion sections have been revised. Additionally, it has been added a benchmarking paragraph in the Results section that compares Italy’s NAS/DMI and DPO/DMI ratios with 2021 EU-27 medians, complete with a new Eurostat citation.

The English language used in this article is weak and fails to meet the necessary standards for publication.

RESPONSE: Manuscript has been edited correcting grammar, coherency etc.

Additionally, the conclusion is poorly written and does not effectively summarize the main findings and overview of the study.

RESPONSE: Conclusions have been revised.

The complete article needs to be rewritten to align with journal standards while incorporating all feedback provided.

RESPONSE: Done

Reviewer 4 Report

Comments and Suggestions for Authors

The manuscript entitled "Economy-Wide Material Flow Accounting: Application in the Italian Glass Industry" provides a thorough analysis of material flows within Italy’s glass sector, utilizing the Economy-Wide Material Flow Accounting (EW-MFA) methodology with STAN software. I wholeheartedly believe the study has potential significance in offering valuable insights into sustainability practices, resource efficiency, and environmental impacts, which align with the journal's scope. However, several important points require attention before the paper can be considered suitable for publication. As they are not in deep, I recommend minor revisions.

The following issues need addressing:

1. Abstract (Page 1, lines 13-26): The abstract is informative but lacks specific numerical results. It would significantly benefit from including key quantitative findings (e.g., amounts of resource extraction, waste generated, or recycling rates) to highlight the study's practical impact clearly.

2. Introduction (Page 2, lines 31-40): While the introduction adequately situates the paper, the authors should clearly articulate the novelty of their work compared to prior studies, particularly mentioning gaps this study aims to fill explicitly.

3. Literature Review (Pages 3-5, lines 74-114): This section is comprehensive but predominantly descriptive. More critical analysis comparing approaches or highlighting limitations of previous studies would strengthen the rationale for selecting EW-MFA and STAN software.

4. Methodology (Pages 7-10, lines 134-196): The explanation of EW-MFA and STAN software is clear. However, the authors should justify the choice of this specific software over alternatives in greater depth. Furthermore, it would help the reader to have a clearer description of how uncertainties and inconsistencies were specifically handled within this research context.

5. Data Quality and Sources (Pages 24, lines 431-436): Authors recognize data limitations but should clearly articulate how these limitations affect their findings’ robustness. Specific reference to sensitivity analysis or confidence intervals regarding data uncertainties would enhance reliability.

6. Calculation Steps (Pages 11-18):

   • On Page 12 (lines 226-242), the assumptions regarding limestone imports as "irrelevant" need clearer justification or data support to avoid potentially oversimplifying a crucial input.

   • On Page 13 (lines 245-255), the calculation of sodium oxide production via the Solvay process needs clarity. Clearly state the rationale behind selecting yield factors (75-85%) and justify their selection rigorously with data or references.

7. Results Section (Pages 20-23):

   • Page 20 (lines 384-385): The estimation of water emissions, critical in environmental assessments, appears overly simplified. Greater detail or rationale is needed for the applied proportionality method and its potential implications for accuracy.

   • Figures 4 and 5 (Pages 22-23): These Sankey diagrams are essential. However, more detailed annotations are required to clearly convey all input-output relationships, particularly clarifying less intuitive connections and flows for readers unfamiliar with these diagrams.

8. Discussion (Pages 23-26):

   • The discussion extensively summarizes the results but lacks sufficient critical analysis comparing the findings with existing literature. There should be explicit reference to previous research findings, noting agreements or deviations clearly.

   • On Page 25 (lines 461-469), the cited benefits of recycling cullet are well documented but lack practical discussion on the feasibility or current Italian practices. More contextual depth about local recycling infrastructure and policy context would improve practical relevance.

9. Conclusions (Pages 26-28):

   • The conclusions summarize findings effectively. However, concrete recommendations for policymakers or industry stakeholders are too general. Providing specific, actionable policy recommendations grounded directly in study findings would enhance applicability.

10. Technical and Language Improvements:

• Throughout the manuscript, minor grammatical errors and unclear sentence constructions (e.g., Page 24, line 431: "most data pertain to 2021") reduce readability. A thorough proofreading by a native English speaker is advised to enhance readability and precision.

• Several citations appear inconsistently formatted (e.g., Page 3 line 59 and Page 3 line 72). Ensure consistent citation formatting according to MDPI guidelines.

In summary, while the paper offers valuable insights into EW-MFA application in the Italian glass sector, significant revisions are needed to enhance methodological rigor, clarify key assumptions, provide a critical comparative discussion, and improve clarity and presentation. After addressing these issues comprehensively, the paper would be suitable for publication in MDPI's Sustainability.

Author Response

The manuscript entitled "Economy-Wide Material Flow Accounting: Application in the Italian Glass Industry" provides a thorough analysis of material flows within Italy’s glass sector, utilizing the Economy-Wide Material Flow Accounting (EW-MFA) methodology with STAN software. I wholeheartedly believe the study has potential significance in offering valuable insights into sustainability practices, resource efficiency, and environmental impacts, which align with the journal's scope. However, several important points require attention before the paper can be considered suitable for publication. As they are not in deep, I recommend minor revisions.
The following issues need addressing:
1.    Abstract (Page 1, lines 13-26): The abstract is informative but lacks specific numerical results. It would significantly benefit from including key quantitative findings (e.g., amounts of resource extraction, waste generated, or recycling rates) to highlight the study's practical impact clearly.
RESPONSE: Abstract has been revised with the results and quantitative findings for example Benchmarking against the 2021 EU-27 shows Italy’s NAS/DMI is 0.63 (vs 0.55 median) and its DPO/DMI is 0.28 (vs 0.31), signalling greater stock build-up but slightly lower waste per tonne of input.
2.    Introduction (Page 2, lines 31-40): While the introduction adequately situates the paper, the authors should clearly articulate the novelty of their work compared to prior studies, particularly mentioning gaps this study aims to fill explicitly.
RESPONSE: done
3.    Literature Review (Pages 3-5, lines 74-114): This section is comprehensive but predominantly descriptive. More critical analysis comparing approaches or highlighting limitations of previous studies would strengthen the rationale for selecting EW-MFA and STAN software.
RESPONSE: A new paragraph now critically compares prior LCA, IO, and corporate-report approaches, highlights their limitations, and explains why EW-MFA and STAN provide the required system
4.    Methodology (Pages 7-10, lines 134-196): The explanation of EW-MFA and STAN software is clear. However, the authors should justify the choice of this specific software over alternatives in greater depth. Furthermore, it would help the reader to have a clearer description of how uncertainties and inconsistencies were specifically handled within this research context.
RESPONSE: Done
5.    Data Quality and Sources (Pages 24, lines 431-436): Authors recognize data limitations but should clearly articulate how these limitations affect their findings’ robustness. Specific reference to sensitivity analysis or confidence intervals regarding data uncertainties would enhance reliability.
RESPONSE: Done
6.    Calculation Steps (Pages 11-18):
On Page 12 (lines 226-242), the assumptions regarding limestone imports as "irrelevant" need clearer justification or data support to avoid potentially oversimplifying a crucial input.
On Page 13 (lines 245-255), the calculation of sodium oxide production via the Solvay process needs clarity. Clearly state the rationale behind selecting yield factors (75-85%) and justify their selection rigorously with data or references.
RESPONSE: Calculation steps and sources revised.

7.    Results Section (Pages 20-23):
•    Page 20 (lines 384-385): The estimation of water emissions, critical in environmental assessments, appears overly simplified. Greater detail or rationale is needed for the applied proportionality method and its potential implications for accuracy.
RESPONSE: This section has been revised making it simpler and more proportional 
•    Figures 4 and 5 (Pages 22-23): These Sankey diagrams are essential. However, more detailed annotations are required to clearly convey all input-output relationships, particularly clarifying less intuitive connections and flows for readers unfamiliar with these diagrams.
RESPONSE: Figures  5 have been revised  colour keys, and call-out notes that explicitly describe every input-output connection, making the Sankey flows clear for non-specialist readers
8.    Discussion (Pages 23-26):
•    The discussion extensively summarizes the results but lacks sufficient critical analysis comparing the findings with existing literature. There should be explicit reference to previous research findings, noting agreements or deviations clearly.
RESPONSE: Despite we agree with that, the lack of precedent studies on the matter with the same approach make it difficult to address direct comparison. However, we encourage other researchers to build on this work and recognize the limitations of this study in the conclusions
•    On Page 25 (lines 461-469), the cited benefits of recycling cullet are well documented but lack practical discussion on the feasibility or current Italian practices. More contextual depth about local recycling infrastructure and policy context would improve practical relevance.
RESPONSE: done
9.    Conclusions (Pages 26-28):
•    The conclusions summarize findings effectively. However, concrete recommendations for policymakers or industry stakeholders are too general. Providing specific, actionable policy recommendations grounded directly in study findings would enhance applicability.
RESPONSE: done
10.    Technical and Language Improvements:
•    Throughout the manuscript, minor grammatical errors and unclear sentence constructions (e.g., Page 24, line 431: "most data pertain to 2021") reduce readability. A thorough proofreading by a native English speaker is advised to enhance readability and precision.
RESPONSE: Done
•    Several citations appear inconsistently formatted (e.g., Page 3 line 59 and Page 3 line 72). Ensure consistent citation formatting according to MDPI guidelines. 
RESPONSE: Done
In summary, while the paper offers valuable insights into EW-MFA application in the Italian glass sector, significant revisions are needed to enhance methodological rigor, clarify key assumptions, provide a critical comparative discussion, and improve clarity and presentation. After addressing these issues comprehensively, the paper would be suitable for publication in MDPI's Sustainability.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you for your thorough effort and careful attention to addressing all the comments. Upon reviewing the revised manuscript, I recommend its acceptance.