Optimizing Circular Economy Choices: The Role of the Analytic Hierarchy Process

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript fully employs and embraces a 'hierarchical' portion of the AHP by successfully tackling a multilevel and multicriteria problem.

The structure of the paper and the sequence of sections is mostly appropriate. However, the "SYNERGIES BETWEEN AHP AND CIRCULAR ECONOMY" section seems more fitted to follow the "INTRODUCTION", as it deals with notions of AHP uses in circular economy environment. Although the topic seems to justify its current position, it is more natural to provide these considerations immediately after, or as a second part of the introduction.

Methodology is used consistently and explained suitably for a well-known method such as AHP, namely without unnecessary details. The reasoning used in setting up the case study is well founded and presented.

The results are presented accurately, with sufficient details, particularly regarding the pairwise comparison. In technical terms, the tables and graphs/figures show what is necessary to be seen.

The discussion and the conclusion are reasonable, sound and a logical extension of the results presented.

The language is adequate, without notable grammatical errors or typos. There are a few technical omissions, listed in the attached pdf, as well as few unexplained terms.

A list of references needs to be attended. Namely, reference no. 5 is incomplete, reference 13 has the wrong position of authors names/surnames (i.e, initials first), and reference 31 contains an unnecessary country name behind the title of the journal (Switzerland). However, more important are the duplicate references 21 and 24 (Ramanathan R.) and 25 and 26 (Gulum P., et. al.). The duplicates should be erased, the list of references changed accordingly, and the reference calls (from page 15 onward) should be brought in order according to new reference numbers. All these cases are marked in the attached file.

Comments for author File: Comments.pdf

Author Response

We appreciate the positive assessment of the manuscript’s structure and methodology, particularly the recognition of how the hierarchical nature of AHP has been successfully implemented in a multilevel and multicriteria setting. In line with your suggestion, we have repositioned the section originally titled “Synergies between AHP and Circular Economy” so that it now follows the introduction.

Regarding the technical omissions noted, we have carefully revised the manuscript to ensure that all key concepts and acronyms are introduced and defined upon first use within the main text. The reference list has also been carefully reviewed and corrected. Duplicated entries were removed (e.g., Ramanathan and Gulum), inconsistencies in author name formatting have been addressed (e.g., references 5 and 13), and unnecessary elements (e.g., country names in journal titles such as in reference 31) were deleted. These corrections are now reflected in the final bibliography and citation calls throughout the text.

Reviewer 2 Report

Comments and Suggestions for Authors

Abstract section: paper examines the application of the Analytical Hierarchical Process (AHP) in the context of the circular economy, focusing on both theoretical and practical perspectives. It’s not clear about the goal, hypotheses, scientific novelty, authors’ position and contribution for the research.

«Effective problem formulation requires the collection and analysis of reliable data». The authors need to clearly list the sources of the data and describe the steps for data collection and validation. Reference source not found

The initial data for 10 scenarios is required in Attachment section. What is the source of the data?

The results for each scenario Figure 2-4 needs to be explained.

LIMITATIONS OF CLASSICAL AHP AND THE NEED FOR ALTERNATIVES should be moved to Literature review or Introduction section.

Reference list needs extension.

Comments on the Quality of English Language

The English could be improved to more clearly express the research, please, double checj the content of the article.

Author Response

We are grateful for your feedback on the abstract and methodological clarity. In response, the abstract has been rewritten to explicitly include the study’s objective, conceptual premise, applied approach, and contribution. It now integrates both theoretical framing and empirical relevance in a more structured manner, while maintaining a natural and fluid tone.
To address your concern about data sourcing and validation, we have revised the methodology section to provide a clearer and more structured account of how the data were obtained, processed, and used. We also detail the procedure by which data were standardized and validated using LCA and LCC models, ensuring internal consistency across all scenarios. While confidentiality agreements prevent disclosure of raw datasets, we have thoroughly documented the generation logic, the assumptions, and the performance indicators used in the analysis.
Regarding the results, we have expanded the discussion accompanying Figures 2 through 4, providing clearer interpretations of what each scenario represents and how the different performance indicators evolve across configurations. Your recommendation to relocate the discussion of AHP limitations was also followed: this content has been integrated into the methodological reflection and conclusion sections, where it now fits more coherently.
Finally, the reference list has been extended to include recent literature on AHP applications in circular economy contexts, including comparative industry.

Reviewer 3 Report

Comments and Suggestions for Authors

The article explores  how the Analytic Hierarchy Process (AHP) can aid decision-making in the context of the circular economy. The paper has  a clear objective for using AHP as a tool to manage multi-criteria decisions in sustainability-oriented projects. The case study focuses on optimizing the must cooling process in a brewery, developed under the EU ECOFACT project.

This application includes environmental, economic, and technical criteria. The use of real-world data, supported by life cycle assessment (LCA) and life cycle costing (LCC), proves the practical relevance of the AHP framework.

Advanced variants such as fuzzy AHP, Analytic Network Process (ANP), and hybrid methods are introduced.

There are some limitations of the manuscript.

1.The inclusion of comparative cases could enhance the relevance of the findings for different industries.

2.The limited stakeholder sample size consists of only 12 individuals who were surveyed. The paper does not offer  details on their expertise or background, raising questions about the  potential bias of the inputs used in the pairwise comparisons.

3.The article needs a sensitivity analysis to assess how variations in weights or input values might affect the outcome. AHP is known to be sensitive to small changes in data;  this omission weakens the confidence in the final scenario rankings.

4.Provide statistical validation or error margins for the weights and rankings.  Clearer labels and more concise visualizations could improve their interpretability.

5.The conclusion is somewhat repetitive. A more focused summary would improve the conclusion. To what extent might other methods produce better outcomes?

Comments on the Quality of English Language

It is fine.

Author Response

Thank you for your thoughtful suggestions. Based on your feedback, we’ve implemented several meaningful updates to the manuscript. First, we significantly expanded the discussion to include comparative cases and rewrote the section to improve focus and eliminate redundancy, particularly regarding repeated explanations of AHP's strengths and limitations.
We also addressed your comment regarding the stakeholder sample. Although the total number of participants remains twelve, we now clarify that all individuals consulted had direct involvement with the demonstration site and technical expertise in relevant domains.
To assess the robustness of the evaluation framework, a sensitivity analysis was conducted on both operational variables and the weighting structure of the AHP model. Four scenarios were explored, addressing variations in resource consumption, recycled content, energy mix, and market prices. These tests showed that environmental and economic indicators respond predictably to efficiency improvements and external changes, with Scenario 3 consistently showing the best performance.
Additionally, a focused sensitivity analysis was applied to the AHP weights, significantly increasing the environmental criterion from 8.52% to 25%. Despite this shift, Scenario 3 remained the top-ranked option, confirming the stability of the decision-making model even under substantial changes in expert priorities.

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Authors,

Your article is a comprehensive and well-structured contribution that effectively links the theoretical foundations of the analytical hierarchy process (AHP) with its practical application in the context of the circular economy (CE), using a case study from the beer industry.
The integration of AHP with sustainability assessment tools such as LCA and LCC, and the reflection on its limitations and potential synergies with AI and other MCDM methods, offers added value to both researchers and practitioners. The manuscript is well contextualized in the existing literature, with a thorough explanation of the AHP steps and solid references. The research design is transparent, and the methodological rigor in the case study, particularly in data normalization, consistency checks, and priority setting, is commendable. The discussion expands appropriately to broader CE challenges and policy implications, strengthening the article's relevance to the journal.

There are, however, some areas that could be improved:

1. While the paper is rich in content, some sections (especially the Discussion) could be more concise. Certain conceptual explanations are repeated (e.g., advantages and limits of AHP) and could be better synthesized.
2. Some figures (e.g., Figure 2 and Figure 6) suffer from poor resolution or unclear axis labels. Additionally, the placeholder "Error! Reference source not found" should be corrected. Improving figure clarity will enhance comprehension of the results.
3. While generally good, the English could benefit from minor stylistic revisions to improve flow and avoid redundancy (e.g., "in addition to" used repetitively at the beginning of paragraphs; excessive use of passive constructions).
4. Although the authors acknowledge the similarity of scenario rankings as a limitation of classical AHP, further reflection could be provided on how these limitations affect the reliability of the results for industrial decision-making, beyond suggesting hybrid methods.
5. The manuscript would benefit from a brief discussion on the extent to which the findings from the brewery case can be replicated in other industrial settings, particularly those with different resource-use dynamics.

Despite the concerns raised, the manuscript offers an important and well-structured contribution to the application of decision support tools in circular economy contexts. I encourage the authors to proceed with the revisions and am confident that the article will be of interest to readers of Sustainability.

Author Response

Thank you for your positive and detailed evaluation of our manuscript. 

In response to your suggestions, we have implemented the following revisions:

The Discussion section has been rewritten to improve focus and eliminate redundancies, particularly regarding repeated explanations of AHP's advantages and limitations.

Figures 2 and 6 have been updated for improved resolution, clearer axis labels, and overall visual clarity. The “Error! Reference source not found” placeholder has been corrected.

Minor stylistic improvements were made throughout the text to enhance readability, reduce redundancy, and minimize passive constructions.

We have expanded the reflection on the limitations of classical AHP, particularly on how low ranking variability can affect decision-making relevance in industrial contexts.

A brief discussion on transferability has been added, addressing how the findings could be adapted to other industries with different resource-use dynamics.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The article can be accepted after minor revisions. Please, double check the reference list.

Author Response

Thank you for your positive assessment. We have carefully reviewed and corrected the reference list to ensure consistency and accuracy.

Reviewer 3 Report

Comments and Suggestions for Authors

Ensure that all tables and figures are cited in numerical order.

Confirm that the repeated sections or paragraphs in the Discussion (on AHP limitations and material selection) are not accidental duplications.

I support the acceptance of this paper for publication after these minor clarifications.

 

Comments on the Quality of English Language

Language is OK>

Author Response

We appreciate your thorough review. We have ensured that all tables and figures are now cited in the correct numerical order. Additionally, we reviewed the Discussion section and confirm that the repeated elements were intentional for clarity

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for submitting the revised version of your manuscript. I appreciate the diligence with which you addressed the comments from the initial review. Overall, this revised version demonstrates both scientific rigor and conceptual maturity, aligning very well with the aims and scope of Sustainability. I have no further suggestions for revision, and I support the manuscript's progression toward publication.

Kind regards

Author Response

Thank you very much for your kind words and encouraging feedback. We truly appreciate your support and are pleased that the revised manuscript aligns well with the journal’s scope and expectations.