The Triple-Level Proposal of the Circular Economy: Circular Performance, Case Studies and a Design Workshop

Response to Reviewer 1 Comments

1. Summary

Dear Reviewer,

Thank you very much for taking the time to review this manuscript and for offering us an opportunity to improve the quality of our submitted manuscript (3627917). We would like to express our sincere gratitude for your meticulous review of our manuscript, and appreciate your constructive and insightful comments and advice.

We have given top priority to addressing the comments you raised, carefully responded to each of your feedback and made corresponding revisions. Your constructive feedbacks enable us to provide a highly improved manuscript. We hope that the revised manuscript could meet the publication standard of this journal.

In the revised manuscript, all the changes have been highlighted in red.

Below is a point-by-point response to your comments.

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1:

Originality:

(Page 2, Lines 15–17) — The "triple-level model" concept is a meaningful contribution, but a deeper comparison with existing multi-level CE frameworks (e.g., Korhonen et al., 2018) would better highlight the novelty.

Response 1:

Thank you for recognizing the contribution of our “triple-level model” concept and providing more in-depth constructive feedback on the emphasis on model novelty. We fully agree that there is a need to strengthen the comparison between our “triple-level model” and existing multilayered CE frameworks, especially the one proposed by Korhonen et al. (2018). Based on your clear and constructive suggestions, we have made some revisions to effectively highlight the novelty and contribution of our proposal.

According to your comment, the research of Korhonen et al. (2018) (https://doi.org/10.1016/j.jclepro.2017.12.111) provide an early methodological model by defining complexity and organizational width in the CE papers reviewed. The aim of their research is to cope with the issue of the complexity of the CE concept, constructing a framework to help scholars clarify different research questions and categorize research themes. Their conceptual model is built for academic research in the CE literature, helping researchers to better organize the actual study issues, topics, themes and research questions related to the CE. In contrast, our study aims to develop theoretical models to guide CE practices in different sectors, particularly in terms of clarifying priorities to promote circular performance. By identifying three escalating levels of circular performance in the CE: materials, products and services, our triple-level model provides a novel insight into understanding and implementing the CE from a design perspective.

We have now fully recognized the significance of highlighting the novelty of our model to enhance the clarity and persuasiveness of the manuscript. In response to your comments, not only have we already revised our sentences to explicitly refer to the literature you point to, but we have also repeatedly highlighted the features and contributions of the triple-level model at various points in the manuscript. In the revised manuscript, we have emphasized the complexity of the CE concept, the importance of design interventions, and the need for theoretical integration. The revisions can be seen as follows.

“As Korhonen et al. argue, the CE is a complex concept that aims to improve resource efficiency and effectiveness by narrowing, slowing, closing, and regenerating resource flows”, which can be seen in the revised manuscript on Page 1, Paragraph 1, Lines 39-41.

Reference:

Korhonen, J.; Honkasalo, A.; Seppälä, J. Circular Economy: The Concept and Its Limitations. Ecological Economics 2018, 143, 37–46. https://doi.org/10.1016/j.ecolecon.2017.06.041.

“However, few studies have clearly articulated the focus and priorities of the CE from a design perspective”, which can be seen in the revised manuscript on Page 2, Paragraph 2, Lines 44-45.

“Unlike previous frameworks, the triple-level proposal combines the CE with sustainable design to support efficient CE transformation. By emphasizing the escalating circular performance from materials to products and services, this study provides a transformative perspective for understanding and implementing the CE. The triple-level proposal clarifies the priority of sustainable design and enriches the theoretical foundations of both disciplines. It highlights the different resource efficiency and value creation of each level and evokes awareness of the hierarchical nature of the CE”, which can be seen in the revised manuscript on Page 3, Paragraph 2, Lines 107-114.

“This study aims to construct a CE hierarchical proposal with a transformative perspective of design and circular performance”, which can be seen in the revised manuscript on Page 13, the last paragraph, Lines 419-420.

“The triple-level proposal offers a practical instruction for clarifying priorities in complex design scenarios and helps to align diverse strategies to maximize circular performance”, which can be seen in the revised manuscript on Page 15, Paragraph 2, Lines 485-487.

“Although receiving increasing attention, research on the integration of the CE and sustainable design is still in its infancy, particularly with regard to circular performance. The triple-level proposal offers a novel insight for understanding the CE from a design perspective, revealing the priority of the CE to maximize circular performance”, which can be seen in the revised manuscript on Page 15, Paragraph 3, Lines 493-496.

Comments 2:

Methodology Detail:
(Page 3, Line 96) — The mixed methodology claim is underdeveloped. More precise explanation of the inductive-deductive steps (sample size, case selection criteria) is required to validate rigor.

Response 2:

Thank you for your comments on the inadequacies of our description of the research methods and some detailed explanations have been added.

We fully agree that the mixed methodology with inductive-deductive steps should be explained in more detail, especially the statements about sample size and case selection criteria. They are key elements of the study and are essential in determining the rigor of our workshop experiments. In response to your valuable suggestions, we have added explanations of the research methodology to enhance the rigor of the manuscript. The revision can be seen as follows.

“In the first stage of our top-down literature review, we systematically reviewed 205 academic articles published from Scopus and Web of Science over the last decades and used Google as a supplement. These articles were screened from an initial pool of 4784 articles. We paid particular attention to 23 of these review articles to ensure comprehensive coverage of theories in the field of the CE and sustainable design. By screening and analyzing article titles, abstracts, and keywords, we integrated three dimensions of the CE from a design perspective: materials, products and services. Second, to assess the validity of the hypothesis, we conduct bottom-up case studies to construct deductive arguments. Examples from different industries were included based on three key criteria: (1) thematic relevance to the proposed hypothesis; (2) the degree of CE practice maturity; and (3) openness and accessibility of the data. Finally, we organized a ten-member workshop comprising seven volunteers and three assistants to apply theory in practice. Driven by the structure of design thinking, the workshop incorporates CE heuristics and canvas to guide inspiration, ideation, and implementation. The three-step approach develops and vali-dates the theoretical and practical feasibility of the triple-level proposal. Figure 1 illustrates the framework of the mixed methodology and the pathway of inductive-deductive approach to establish the proposal”, which can be seen in the revised manuscript on Page 2, the last paragraph, Lines 87-104.

Comments 3:

Workshop Sample Size:
(Page 11, Line 395) — The design workshop includes only seven students. This is too small to generalize results. Authors should acknowledge this as a limitation.

Response 3:

Thank you very much for your insightful comment regarding the small sample size of our workshop experiment. We greatly appreciate your pointing out this important limitation and some corrections have been made.

In light of your comments, we fully acknowledge that the limited number of participants may pose a challenge to the generalizability of our findings and pointing out this important aspect. We fully agree with your assessment that the sample of only seven student volunteers in the circular design workshop was too small. In fact, a total of ten members have followed the whole process of this design workshop, including seven recruited university student volunteers and three professional assistants with knowledge background. We greatly apologize for the omission of descriptions of the three professional assistants and have made additional notes to enhance the rigor of the manuscript. In the revised manuscript, we have added this explanation.

“Finally, we organized a ten-member workshop comprising seven volunteers and three assistants to apply theory in practice”, which can be seen in the revised manuscript on Page 3, Paragraph 1, Lines 98-99.

In any case, we must recognize that this is still a very small sample size. This is not only due to our desire to obtain more reliable first-hand observation and more detailed one-to-one user feedback, but also because of the unavoidable realities of volunteer recruitment. On the one hand, our circular design workshop requires participants to have some background knowledge or relevant experience about the CE. This has somewhat increased the threshold of participants and screened out some of the volunteers who were willing to sign up but did not meet the requirements. On the other hand, in accordance with the formal workshop process, our experiments strictly followed the three phases of design thinking: inspiration, ideation and implementation. During our workshop, a total of six offline activities were organized. These included an introduction to the background knowledge of the CE and the triple-level model, a presentation on the overall project process and requirements, three hands-on activities with specific operation guidelines, and a final session for presentation and feedback collection. The multi-tasking nature and highly intensive schedule of the activities can significantly undermine people’s willingness to participate, whereas the exacting task requirements may further erode their enthusiasm and sap their motivation. Owing to the above critical factors, compounded by time and location limitations, we were obliged to conduct a small-scale design workshop as a first attempt. Despite the limitations of the small sample size, we believe that this workshop experiment makes an important contribution. It not only provides first-hand qualitative data for model validation, but also provides practical insights into the application of the triple-level model. Although lacking in solid persuasiveness, these findings can serve as an initial exploration and lay the groundwork for future research.

Nevertheless, as you pointed out in the comment, we fully acknowledge a critical limitation of our study that the sample size is too small to generalize results. In order to fully respond to your comments about the limitation of too small a sample size, we have made two key revisions to the manuscript. First, a limitation statement has been inserted into the final paragraph of the “Introduction” section. Furthermore, in the “Conclusion” section, we have not only re-emphasized this limitation but also made a decision for future studies to expand the sample size and get more reliable results. The specific revisions can be seen as follows.

“Finally, Section 6 draws conclusions, acknowledges key limitations and looks to the future”, which can be seen in the revised manuscript on Page 3, the last paragraph, Lines 123-124.

“In addition, the small sample size of the workshop experiments can diminish the generalizability of the results, which should be further expanded in future studies”, which can be seen in the revised manuscript on Page 15, the last paragraph, Lines 513-515.

“To further validate the effectiveness of the proposal in different scenarios, long-term observations with more extensive experimental data should be included in future research”, which can be seen in the revised manuscript on Page 15, the last paragraph, Lines 517-519.

Comments 4:

Data Presentation:
(Page 8, Line 278) — The case study on BASF is interesting, but lacks quantified comparison against control groups or baseline data. It appears anecdotal rather than robust.

Response 4:

Thank you for your detailed and insightful comments on our manuscript. We are very honored and grateful for your interest in our case study on BASF’s CE practices. In response to your feedback, we have made some revisions to address your concerns and questions.

We agree with your comment that the initial analyses lacked more accurate data such as quantitative comparisons against control groups or baseline data, and relied on sources that may not be verifiable. The inaccurate statements may undermine the scientific and persuasive nature of our case studies and raises to your questions and concerns. In response, we have undertaken a comprehensive review, thoroughly revised the content about both the examples and references. The original citation of (Wang, 2021) has been removed due to its availability and the limited and ambiguity data. Instead, we have reassessed two sources of reliable and publicly available data to improve the credibility and accuracy of our analyses: one is the trade news published on BASF's official company website; the other is the FOC Group’s 2024 international briefing published in the Focus on Catalysts journal.

In more detail, the information on BASF’s ChemCycling technology and its impact on CO₂ emissions is sourced from their official sustainability page (https://www.basf.com/global/en/media/news-releases/2024/09/p-24-280). This page reports directly on the achievements of BASF’s recycled coatings in the automotive refinishing market, providing evidence of its initiatives to recycle to promote a CE. In addition, we have included a report from the Focus on Catalysts journal, entitled “Encina and BASF establish long-term partnership for supply of circular raw materials”, incorporating a co-operation agreement between BASF and recycled materials supplier Encina to further support its recycling initiatives (https://www.sciencedirect.com/science/article/pii/S1351418024002551). The original source of this information is BASF’s official release dated June 20, 2024 (http://www.basf.com), as noted in the journal’s citation. This peer-reviewed industry briefing offers an independent validation of BASF’s CE commitments. Moreover, we have replaced the corresponding figure to better explain the updated formulation, as detailed in Figure 3 and its caption. Here are the details about our revisions.

“As illustrated in Figure 3, BASF uses its unique ChemCycling technology for automotive coatings, which can reduce CO2 emissions by up to 50% through the use of varnish made from recycled waste tires. In addition, BASF signed an agreement with Encina, a manufacturer of ISCC PLUS certified circular chemicals, to declare its commitment to increasing the use of recycling-based raw materials to promote the CE”, which can be seen in the revised manuscript on Page 7, the last paragraph, Lines 283-287.

Figure 3. BASF’s ChemCycling® and its application in automotive coatings.

Source from: https://www.basf.com/global/en/media/news-releases/2024/09/p-24-280 (Accessed: May 10, 2025)

Reference:

United Nations Environment Programme. Global Resources Outlook 2024: Bend the Trend – Pathways to a Liveable Planet as Resource Use Spikes (R). International Resource Panel, Nairobi, 2024. https://www.resourcepanel.org/reports/global - resources - outlook - 2024 (accessed 2025 - 04 - 19).

Comments 5:

Literature Integration
(Page 5, Lines 69–71) — While many CE models are cited, there’s insufficient critical analysis of how the proposed model overcomes fragmentation.

Response 5:

Thank you for your valuable feedback on the need to clarify how our model addresses the fragmentation issue in existing CE frameworks. We fully agree that this clarification is crucial for demonstrating the novelty of our model and strengthening our contribution. Some revisions have been made to address your concerns.

First, in the “Introduction” section of the literature review, we have added some critical analyses to illustrate the strengths and weaknesses of each model. Furthermore, we have included comparative analyses and classifications of different models to further illustrate the limitations and shortcomings of the current research. For instance, we have pointed out that although the Ellen MacArthur Foundation’s “butterfly diagram” contributes to the theoretical framework of the CE, there is a lack of implementation pathways. The “TU Delft” model focuses mainly on the circular business model innovation, but ignores the basic materials and products. Second, we have further illustrated the path and basis of this theoretical integration in the following paragraphs. The revision can be seen as follows.

“Although CE models are gradually being proposed in various fields, their practice is still limited by unclear priorities and circular performance. The Ellen MacArthur Foundation's ‘butterfly diagram’ is conceptually groundbreaking but lacks practical guidance¹⁶. Delft University of Technology's ‘TU Delft’ model helps organizations integrate the CE into their business models but lacks systematic consideration of materials and products¹⁷. EU Horizon’s’R2π-the route’ highlights the recycling, reuse, and access in the CE but fails to clarify the interactions between the dimensions¹⁸. In terms of assessing circular performance, Baratsas et al. develop the Micro Circular Economy Index framework to assess the process of CE development, while Drofenik et al. extend it to micro-macro-micro systems to harmonize the overall performance^19,20. These approaches have facilitated the application of the CE in different industries, but systematic frame-works are still needed to generalize strategies and methods across dimensions”, which can be seen in the revised manuscript on Page 2, Paragraph 3, Lines 56-67.

“Current CE research exhibits extensive but fragmented characteristics, with a notable absence of a systematic model to clarify its priorities and focus. By analyzing the titles, abstracts and keywords of the literature, we classify the CE strategies into three dimensions: material recycling, product reuse, and service circulation^21,22,23. This integration reveals the hierarchical nature of circular performance from a design perspective, with roots that can be traced back to Stahel’s three stages of CE development: the ‘D’ (Re-duction) era, the ‘R’ (Reuse) era and the performance economy (products as services)²⁴”, which can be seen in the revised manuscript on Page 2, Paragraph 4, Lines 68-74.

Reference:

17.       Howard, K. TU Delft Library. In Encyclopedia of Libraries, Librarianship, and Information Science (First Edition); Baker, D., Ellis, L., Eds.; Academic Press: Oxford, 2025; pp 256–261. https://doi.org/10.1016/B978-0-323-95689-5.00202-9.

18.       Lin, Q.; Zhang, K.; Giguet-Covex, C.; Arnaud, F.; McGowan, S.; Gielly, L.; Capo, E.; Huang, S.; Ficetola, G. F.; Shen, J.; Dearing, J. A.; Meadows, M. E. Transient Social-Ecological Dynamics Reveal Signals of Decoupling in a Highly Dis-turbed Anthropocene Landscape. Proc. Natl. Acad. Sci. U. S. A. 2024, 121 (17), e2321303121. https://doi.org/10.1073/pnas.2321303121.

19.       Baratsas, S. G.; Pistikopoulos, E. N.; Avraamidou, S. A Quantitative and Holistic Circular Economy Assessment Frame-work at the Micro Level. Computers & Chemical Engineering 2022, 160, 107697. https://doi.org/10.1016/j.compchemeng.2022.107697.

20.       Drofenik, J.; Seljak, T.; Novak Pintarič, Z. A Multi-Level Approach to Circular Economy Progress: Linking National Targets with Corporate Implementation. Journal of Cleaner Production 2025, 493, 144902. https://doi.org/10.1016/j.jclepro.2025.144902.21. Feng, J.; Liu, W.; Chen, F. Moving towards a Circular Economy: A Systematic Review of Barriers to Electric Vehicle Battery Recycling. Sustainable Production and Consumption 2025, 54, 241–260. https://doi.org/10.1016/j.spc.2025.01.006.

21.       Feng, J.; Liu, W.; Chen, F. Moving towards a Circular Economy: A Systematic Review of Barriers to Electric Vehicle Battery Recycling. Sustainable Production and Consumption 2025, 54, 241–260. https://doi.org/10.1016/j.spc.2025.01.006.

22. D’Urzo, M.; Campagnaro, C. Design-Led Repair & Reuse: An Approach for an Equitable, Bottom-up, Innovation-Driven Circular Economy. Journal of Cleaner Production 2023, 387, 135724. https://doi.org/10.1016/j.jclepro.2022.135724

23. Metic, J.; Guzzo, D.; Kopainsky, B.; McAloone, T. C.; Pigosso, D. C. A. A. Simulation-Based Approach for Investigating the Dynamics of Rebound Effects in the Circular Economy: A Case of Use-Oriented Product/Service System. Journal of En-vironmental Management 2024, 365, 121627. https://doi.org/10.1016/j.jenvman.2024.121627

24. Stahel, W. The Performance Economy, 2nd Edition; 2010; https://doi.org/10.1057/9780230274907

Comments 6:

Language Quality:

(Page 1, Line 12) — There are multiple minor grammatical errors ("Currently. research" should be "Currently, research"). A thorough proofreading is necessary to enhance clarity and professionalism.

Response 6:

Thank you for your meticulous review of our manuscript and for pointing out the subtle but critical punctuation error. We sincerely appreciate your attention to the details and some revisions have been made.

We deeply apologize for our negligence in checking on a simple issue. These errors may seem minor, but they do seriously affect the clarity and professionalism of the manuscript. We have taken this issue very seriously and immediately conducted a thorough inspection of the entire manuscript. In order to further improve the quality of the language, we have corrected not only the punctuation problem you explicitly mentioned, but also examined similar writing errors in other sentences, including word spelling, grammar, and sentence structure. The revisions can be seen as follows.

“Currently, research generally segregates materials, products and services within the CE, overlooking their hierarchy and interactions in circular performance”, which can be seen in the revised manuscript on Page 1, Abstract, Lines 12-14.

“Employing a mixed methodology of induction and deduction, this study constructs a triple-level proposal of the CE from a design perspective”, which can be seen in the revised manuscript on Page 1, Abstract, Lines 14-15.

“The proposal integrates material recycling, product reuse, and service circulation into a multi-hierarchical progression, clarifying the priorities of the CE and sustainable design”, which can be seen in the revised manuscript on Page 1, Abstract, Lines 15-17.

“The CE is initially formulated as a closed-loop system designed to recycle waste across the entire lifecycle of resource extraction, production, and consumption”, which can be seen in the revised manuscript on Page 2, Paragraph 2, Lines 45-47.

“Although CE models are gradually being proposed in various fields, their practice is still limited by unclear priorities and circular performance”, which can be seen in the revised manuscript on Page 2, Paragraph 3, Lines 56-57.

“Delft University of Technology's ‘TU Delft’ model helps organizations integrate the CE into their business models but lacks systematic consideration of materials and products”, which can be seen in the revised manuscript on Page 2, Paragraph 3, Lines 59-60.

“EU Horizon’s ‘R2π-the route’ highlights the recycling, reuse, and access in the CE but fails to clarify the interactions between the dimensions”, which can be seen in the revised manuscript on Page 2, Paragraph 3, Lines 61-62.

“In terms of assessing circular performance, Baratsas et al. develop the Micro Circular Economy Index framework to assess the process of CE development, while Drofenik et al. extend it to micro-macro-micro systems to harmonize the overall performance”, which can be seen in the revised manuscript on Page 2, Paragraph 3, Lines 62-65.

“Section 5 makes a discussion and provides clear policy recommendations for stakeholders”, which can be seen in the revised manuscript on Page 3, the last paragraph, Lines 122-123.

“This study proposes a progressive triple-level proposal of the CE to explore the priority and focus in circular systems”, which can be seen in the revised manuscript on Page 4, Paragraph 1, Lines 126-127.

“As illustrated in Figure 2, each tightening of the circle represents an escalation in resource efficiency and circular performance, with varying degrees of impact on the economy, society, and the environment.”, which can be seen in the revised manuscript on Page 4, Paragraph 1, Lines 128-131.

“In all, the triple-level proposal points to the direction and focus of the CE and sustainable design, revealing the interactions across materials, products, and services to enhance economic, social, and environmental performance”, which can be seen in the revised manuscript on Page 4, Paragraph 2, Lines 141-144.

“The CE requires a systemic shift in which all materials within economic processes are fully utilized or reintegrated into closed-loop systems”, which can be seen in the revised manuscript on Page 4, the last paragraph, Lines 152-153.

“The key to recycling is the non-toxicity of biomaterials and ability of non-biomaterials to retain maximum utility value with minimum energy consumption, focusing on the reprocessing of end-of-life materials into renewable resources”, which can be seen in the revised manuscript on Page 5, Paragraph 2, Lines 169-171.

“Material recycling mitigates pollution by managing the entire process of resource use”, which can be seen in the revised manuscript on Page 5, Paragraph 3, Line 173.

“Material recycling is the first step in a multi-level process, which must be followed by more efficient reuse and service cycles to realize its full potential”, which can be seen in the revised manuscript on Page 5, Paragraph 3, Lines 177-179.

“It is the practice of refurbishing or reselling products to keep a product in use for as long as possible”, which can be seen in the revised manuscript on Page 5, Paragraph 4, Lines 182-183.

“Compared to producing new products, redistribution and reuse are effective in reducing environmental impact and promise improved CE”, which can be seen in the revised manuscript on Page 5, Paragraph 4, Lines 182-190.

“To increase product durability, companies can adopt after-sales services to sustain product use and second-hand trading platforms to promote resale. The reuse and resale of old items avoid resource inputs by extending the product life cycle to reduce the need for new products. It extends the useful life of products and components to avoid the need for new products”, which can be seen in the revised manuscript on Page 5, Paragraph 4, Lines 200-204.

“It not only enhances the intensity of resource use to reduce environmental footprint, but also delivers significant cost savings and creates social value”, which can be seen in the revised manuscript on Page 6, Paragraph 4, Lines 200-204.

“By offering more flexible and diversified options, the rent-to-own model avoids the desire to keep multiple products”, which can be seen in the revised manuscript on Page 6, Paragraph 4, Lines 237-239.

“Both theoretical research and practices on circular business model innovation are still in their infancy”, which can be seen in the revised manuscript on Page 6, the second last paragraph, Lines 245-246.

“Each level builds on the previous level of evolution, with continuous improvements in ecological benefits and economic and social value”, which can be seen in the revised manuscript on Page 7, Paragraph 1, Lines 260-261.

“As a result, to truly improve the performance in CE systems, the focus must be shifted from materials to a more advanced level of products and services”, which can be seen in the revised manuscript on Page 8, Paragraph 2, Lines 315-317.

“Nowadays, Apple actively participates in the trade-in policy, which offers repair, replacement, and upgrade services to maintain product use”, which can be seen in the revised manuscript on Page 9, Paragraph 1, Lines 328-329.

“Inspired by the success of Google, IBM and Intel, the likes of Nestlé, Unilever and Walmart have all benefited from a PSS innovation”, which can be seen in the revised manuscript on Page 10, Paragraph 2, Lines 361-362.

“By replacing the sale of products with flexible usages, services in circulation enable the fulfilment of consumer needs without additional resource consumption”, which can be seen in the revised manuscript on Page 10, the last paragraph, Lines 376-377.

“Figure 9 shows the heuristic cards applied in our circular design workshop, which include classic CE strategies, principles and examples related to design”, which can be seen in the revised manuscript on Page 11, Paragraph 2, Lines 398-400.

“The triple-level proposal of material recycling, product reuse, and service circulation exposes the hierarchy of the CE in terms of circular performance”, which can be seen in the revised manuscript on Page 13, Paragraph 1, Lines 422-423.

“It not only presents an innovative perspective on identifying the focus and priorities of the CE as well as sustainable design, but also identifies the breakthrough point for maximizing circular performance”, which can be seen in the revised manuscript on Page 14, Paragraph 2, Lines 439-442.

“They are so focused on materials and products that they miss the huge advantage of value creation in non-physical services”, which can be seen in the revised manuscript on Page 13, Paragraph 1, Lines 452-453.

“Despite the use of literature reviews, case studies, and a design workshop to qualitatively demonstrate its theoretical and practical feasibility, methodological refinement is indispensable to strengthen its credibility. Future research could implement quantitative methods such as Life Cycle Assessment to provide reliable datasets for a scientific model”, which can be seen in the revised manuscript on Page 15, the last paragraph, Lines 509-513.

5. Additional clarifications

Thank you again for your rigorous review and constructive suggestions. We firmly believe that, with your guidance, the quality of our manuscript has been significantly improved.

In the revised manuscript, we have given top priority to addressing the questions you raised and have undertaken a comprehensive revision to improve the quality of our manuscript. In this way, we sincerely hope that our revised manuscript meets the publication standards of the journal. We are looking forward to the possibility of receiving your continued guidance and advice in the future.

Best regards,

Shuai Zhang, Yicheng Han, Dajian Zhu

Response to Reviewer 3 Comments

1. Summary

Dear Reviewer,                                       

Thank you very much for taking the time to review this manuscript and for offering us an opportunity to improve the quality of our submitted manuscript (3627917). We appreciate your constructive and insightful comments and advice. We have carefully addressed each concern and made the corresponding revisions. These comments enable us to provide a highly improved manuscript. We hope that the revised manuscript could meet the publication standard of this journal.

In the revised manuscript, all the changes have been highlighted in red. Below is a point-by-point response to your comments.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

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

Yes

We sincerely appreciate the time and expertise you have invested in reviewing our manuscript. Your feedback has been invaluable to our overall revision. thoughtful assessment of each item in our manuscript. We are extremely grateful for your overall recognition of the manuscript’s quality, which motivates us to further enhance the work.

We have made it a priority to address the questions you have raised, especially the reliability of references. In response to your thoughtful feedback, we have undertaken a comprehensive revision to improve the quality of our manuscript. In the next section, we have provided detailed explanations and revisions to your comments. It is our sincere hope that these efforts will bring our study up to the journal's publication standards.

Are the research design, questions, hypotheses and methods clearly stated?

Yes

Are the arguments and discussion of findings coherent, balanced and compelling?

Yes

For empirical research, are the results clearly presented?

Yes

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?

Yes

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1:

The article entitled "The Triple-Level Model of the Circular Economy: Circular Performance, Case Studies, and Design Workshop," by Shuai Zhang, Yicheng Han, and Dajian Zhu, aims to adopt a mixed methodology of inductive-deductive approach to establish a generic triple-level CE model. The model features three ascending cycles: material recycling, product reuse, and service circulation.

The manuscript is presented following the different hypotheses presented. The different examples of the three sectors into which the circular economy model is divided are very clear. The different diagrams help understand this model, and the examples complement each one: material recycling, product reuse, and service circulation.

The text presents a very good structure, and only the references should be reviewed: some were not found, others are not in the correct place.

In this situation, the article may be accepted with minor changes.

Response 1:

Thank you for your thorough review and the invaluable feedback provided on our manuscript. We are extremely grateful for your recognition of the structure, the clarity of the case illustrations, and the effectiveness of the diagrams in elucidating the CE model. We are pleased to hear that the article may be accepted with minor revisions. Your positive feedback not only validates our previous efforts but also greatly encourages us to delve deeper into this research area. Nonetheless, we are acutely aware that our manuscript still requires further revision to ensure the accuracy and accessibility of the references.

In response to your comments, we have conducted a comprehensive review of the references and made necessary adjustments. Our modifications have been implemented in three main dimensions. Our modifications have been implemented in three dimensions. First, for the references that is not available or could not be located, we have re-searched authoritative databases including Web of Science, Science Direct and Google Scholar in an attempt to supplement the missing information. If a valid and reliable source is still not available after confirmation, we have promptly removed the previous citation and replaced it with a new relevant article as a substitute. Instead, we have replaced them with full-text accessible and valid sources that fit the argument, in order to ensure the credibility and scientific validity of the manuscript. Second, as for the misplaced references, we have carefully rearranged all the citations in strict accordance with the formatting requirements of the journals as well as the logical flow of the articles, ensuring that each reference precisely matches the relevant discussions. Finally, in addition to the issues of accessibility and accuracy of the literature that you have clearly identified, we have thoroughly reviewed the formatting of the references, including spelling, punctuation, author information and citation formatting.

Guided by your constructive suggestions and recommendations, we firmly believe that the quality of our manuscript has been significantly improved to better meet the standards for journal publication. The revisions can be seen as follows.

Citations or references that have been removed or revised due to their invalidity or irrelevance:

“(IRP, 2024)” in the sentence “As global material consumption is expected to double by 2060, the conventional linear ‘take-make-dispose’ economic paradigm is accelerating an unparalleled rate of resource depletion and environmental degradation (IRP, 2024)”, which can be seen in the previous version on Page 1, Lines 31-33.

“(Xu and Tang, 2024)” in the sentence “With its potential to conserve resources and mitigate pollution, the CE is an alternative that can effectively reduce environmental impacts and minimize economic trade-offs (Magnano et al., 2024; Xu and Tang, 2024)”, which can be seen in the previous version on Page 1, Lines 38-40.

“(Chauhan et al., 2022)” in the sentence “The Ellen MacArthur Foundation draws a seminal ‘butterfly diagram’ to divide the material flow into biological and technological cycles (Chauhan et al., 2022)”, which can be seen in the previous version on Page 2, Lines 58-59.

“(Stahel, 1981)” in the sentence “As the initial stage towards circular supply chains, recycling merely closes loops between post-use waste and new production, without altering the speed of materials flows (Stahel, 1981)”, which can be seen in the previous version on Page 4, Lines 146-148.

“(Cayzer et al. 2017)” in the sentence “Many companies adopt modularization, remanufacturing, and component reuse methods to promote repeated use (Cayzer et al. 2017)”, which can be seen in the previous version on Page 8, Lines 317-318.

Correct references that have been added as replacements:

“(UNEP, 2024)” in the sentence “Without an urgent paradigm shift in economic development, total extraction of raw materials, including metals, minerals, fossil fuels and biomass, could rise by 60% by 2060 compared to 2020 levels”, which can be seen in the previous version on Page 1, Paragraph 1, Lines 33-35.

“(Bocken et al., 2025)” with new formulation “It has the capacity to address environmental challenges and sustainable development in the industrial sector”, which can be seen in the revised manuscript on Page 2, Paragraph 1, Lines 41-42.

“(Velenturf et al.,2019)” with new formulation “The Ellen MacArthur Foundation's “butterfly diagram” is conceptually groundbreaking but lacks practical guidance”, which can be seen in the revised manuscript on Page 2, Paragraph 1, Lines 57-58.

“(Stahel, 1982)” in the sentence “As the initial stage towards circular supply chains, recycling merely closes loops between post-use waste and new production, without altering the speed of materials flows”, which can be seen in the revised manuscript on Page 4, Paragraph 3, Lines 156-158.

“(Griffiths, 2016)” in the sentence “Many companies adopt modularization, remanufacturing, and component reuse methods to promote repeated use”, which can be seen in the revised manuscript on Page 8, Paragraph 3, Lines 321-322.

Reference:

1.         United Nations Environment Programme. Global Resources Outlook 2024: Bend the Trend – Pathways to a Liveable Planet as Resource Use Spikes (R). International Resource Panel, Nairobi, 2024. https://www.resourcepanel.org/reports/global - resources - outlook - 2024 (accessed 2025 - 04 - 19).

6. Bocken, N. M. P.; Kimpimaki, J. P.; Ritala, P.; Konietzko, J. How Circular Are Large Corporations? Evidence from a Large-Scale Survey with Senior Leaders. Resources, Conservation and Recycling 2025, 215, 108151. https://doi.org/10.1016/j.resconrec.2025.108151.

16.       Velenturf, A. P. M.; Archer, S. A.; Gomes, H. I.; Christgen, B.; Lag-Brotons, A. J.; Purnell, P. Circular Economy and the Matter of Integrated Resources. Sci. Total Environ. 2019, 689, 963–969. https://doi.org/10.1016/j.scitotenv.2019.06.449.

29.       Stahel, W. R. Product of Life Factor. 1982. NARC.

57.       Griffiths, P.; Cayzer, S. Design of Indicators for Measuring Product Performance in the Circular Economy. In Sustainable Design and Manufacturing 2016; Setchi, R., Howlett, R. J., Liu, Y., Theobald, P., Eds.; Springer International Publishing: Cham, 2016; pp 307–321. https://doi.org/10.1007/978-3-319-32098-4_27.

4. Response to Comments on the Quality of English Language

Point 1:

(x) The English is fine and does not require any improvement.

Response 1:

Thank you for your objective assessment of the quality of our English writing. Although the quality of the English language is not explicitly stated, we have thoroughly checked and optimized the sentences in the manuscript.

In the reviewed manuscript, we have made comprehensive improvements to word spelling, punctuation, sentence structure and clarity. Our detailed revisions are shown below.

“Currently, research generally segregates materials, products and services within the CE, overlooking their hierarchy and interactions in circular performance”, which can be seen in the revised manuscript on Page 1, Abstract, Lines 12-14.

“Employing a mixed methodology of induction and deduction, this study constructs a triple-level proposal of the CE from a design perspective”, which can be seen in the revised manuscript on Page 1, Abstract, Lines 14-15.

“The proposal integrates material recycling, product reuse, and service circulation into a multi-hierarchical progression, clarifying the priorities of the CE and sustainable design”, which can be seen in the revised manuscript on Page 1, Abstract, Lines 15-17.

“The CE is initially formulated as a closed-loop system designed to recycle waste across the entire lifecycle of resource extraction, production, and consumption”, which can be seen in the revised manuscript on Page 2, Paragraph 2, Lines 45-47.

“Although CE models are gradually being proposed in various fields, their practice is still limited by unclear priorities and circular performance”, which can be seen in the revised manuscript on Page 2, Paragraph 3, Lines 56-57.

“Delft University of Technology's ‘TU Delft’ model helps organizations integrate the CE into their business models but lacks systematic consideration of materials and products”, which can be seen in the revised manuscript on Page 2, Paragraph 3, Lines 59-60.

“EU Horizon’s ‘R2π-the route’ highlights the recycling, reuse, and access in the CE but fails to clarify the interactions between the dimensions”, which can be seen in the revised manuscript on Page 2, Paragraph 3, Lines 61-62.

“In terms of assessing circular performance, Baratsas et al. develop the Micro Circular Economy Index framework to assess the process of CE development, while Drofenik et al. extend it to micro-macro-micro systems to harmonize the overall performance”, which can be seen in the revised manuscript on Page 2, Paragraph 3, Lines 62-65.

“Section 5 makes a discussion and provides clear policy recommendations for stakeholders”, which can be seen in the revised manuscript on Page 3, the last paragraph, Lines 122-123.

“This study proposes a progressive triple-level proposal of the CE to explore the priority and focus in circular systems”, which can be seen in the revised manuscript on Page 4, Paragraph 1, Lines 126-127.

“As illustrated in Figure 2, each tightening of the circle represents an escalation in resource efficiency and circular performance, with varying degrees of impact on the economy, society, and the environment.”, which can be seen in the revised manuscript on Page 4, Paragraph 1, Lines 128-131.

“In all, the triple-level proposal points to the direction and focus of the CE and sustainable design, revealing the interactions across materials, products, and services to enhance economic, social, and environmental performance”, which can be seen in the revised manuscript on Page 4, Paragraph 2, Lines 141-144.

“The CE requires a systemic shift in which all materials within economic processes are fully utilized or reintegrated into closed-loop systems”, which can be seen in the revised manuscript on Page 4, the last paragraph, Lines 152-153.

“The key to recycling is the non-toxicity of biomaterials and ability of non-biomaterials to retain maximum utility value with minimum energy consumption, focusing on the reprocessing of end-of-life materials into renewable resources”, which can be seen in the revised manuscript on Page 5, Paragraph 2, Lines 169-171.

“Material recycling mitigates pollution by managing the entire process of resource use”, which can be seen in the revised manuscript on Page 5, Paragraph 3, Line 173.

“Material recycling is the first step in a multi-level process, which must be followed by more efficient reuse and service cycles to realize its full potential”, which can be seen in the revised manuscript on Page 5, Paragraph 3, Lines 177-179.

“It is the practice of refurbishing or reselling products to keep a product in use for as long as possible”, which can be seen in the revised manuscript on Page 5, Paragraph 4, Lines 182-183.

“Compared to producing new products, redistribution and reuse are effective in reducing environmental impact and promise improved CE”, which can be seen in the revised manuscript on Page 5, Paragraph 4, Lines 182-190.

“To increase product durability, companies can adopt after-sales services to sustain product use and second-hand trading platforms to promote resale. The reuse and resale of old items avoid resource inputs by extending the product life cycle to reduce the need for new products. It extends the useful life of products and components to avoid the need for new products”, which can be seen in the revised manuscript on Page 5, Paragraph 4, Lines 200-204.

“It not only enhances the intensity of resource use to reduce environmental footprint, but also delivers significant cost savings and creates social value”, which can be seen in the revised manuscript on Page 6, Paragraph 4, Lines 200-204.

“By offering more flexible and diversified options, the rent-to-own model avoids the desire to keep multiple products”, which can be seen in the revised manuscript on Page 6, Paragraph 4, Lines 237-239.

“Both theoretical research and practices on circular business model innovation are still in their infancy”, which can be seen in the revised manuscript on Page 6, the second last paragraph, Lines 245-246.

“Each level builds on the previous level of evolution, with continuous improvements in ecological benefits and economic and social value”, which can be seen in the revised manuscript on Page 7, Paragraph 1, Lines 260-261.

“As a result, to truly improve the performance in CE systems, the focus must be shifted from materials to a more advanced level of products and services”, which can be seen in the revised manuscript on Page 8, Paragraph 2, Lines 315-317.

“Nowadays, Apple actively participates in the trade-in policy, which offers repair, replacement, and upgrade services to maintain product use”, which can be seen in the revised manuscript on Page 9, Paragraph 1, Lines 328-329.

“Inspired by the success of Google, IBM and Intel, the likes of Nestlé, Unilever and Walmart have all benefited from a PSS innovation”, which can be seen in the revised manuscript on Page 10, Paragraph 2, Lines 361-362.

“By replacing the sale of products with flexible usages, services in circulation enable the fulfilment of consumer needs without additional resource consumption”, which can be seen in the revised manuscript on Page 10, the last paragraph, Lines 376-377.

“Figure 9 shows the heuristic cards applied in our circular design workshop, which include classic CE strategies, principles and examples related to design”, which can be seen in the revised manuscript on Page 11, Paragraph 2, Lines 398-400.

“The triple-level proposal of material recycling, product reuse, and service circulation exposes the hierarchy of the CE in terms of circular performance”, which can be seen in the revised manuscript on Page 13, Paragraph 1, Lines 422-423.

“It not only presents an innovative perspective on identifying the focus and priorities of the CE as well as sustainable design, but also identifies the breakthrough point for maximizing circular performance”, which can be seen in the revised manuscript on Page 14, Paragraph 2, Lines 439-442.

“They are so focused on materials and products that they miss the huge advantage of value creation in non-physical services”, which can be seen in the revised manuscript on Page 13, Paragraph 1, Lines 452-453.

“Despite the use of literature reviews, case studies, and a design workshop to qualitatively demonstrate its theoretical and practical feasibility, methodological refinement is indispensable to strengthen its credibility. Future research could implement quantitative methods such as Life Cycle Assessment to provide reliable datasets for a scientific model”, which can be seen in the revised manuscript on Page 15, the last paragraph, Lines 509-511.

5. Additional clarifications