Embedding Circular Operations in Manufacturing: A Conceptual Model for Operational Sustainability and Resource Efficiency

No

Reviewer Comment

Revision Response

1

Several paragraphs are dedicated to explaining general concepts of the linear and circular models, without clearly synthesizing how these background elements specifically lead to the proposed model. It is recommended to integrate a more direct summary of previous advances and gaps, using explicit transitions between key authors or approaches.

This has been revised at the end of Subsection 1.1 by adding explicit transitional sentences between key references and clearly articulating the theoretical gap. These lead directly to the rationale for the proposed model.

2

The manuscript does not articulate specific research questions or hypotheses. This limits the logical structure of rigorous scientific inquiry and complicates the future empirical validation that the article itself suggests in Section 6 (Future Research Agenda). Section to improve: End of Section 1 (1.4 Structure of the Paper), or as a new subsection at the end of the introduction (e.g., 1.5 Research Questions and Assumptions).

A new Subsection 1.4 “Research Questions and Assumptions” has been added before the structure section. Two explicit research questions have been formulated to guide the development of the conceptual model.

3

To strengthen the coherence and credibility of the arguments, it is recommended to incorporate explicit comparisons with similar models in the literature on circular or sustainable operations.

Revisions were made in Subsection 5.1 (Theoretical Implications) by incorporating direct comparisons with models such as Geissdoerfer et al (2023), Skalli et al. (2022) and Samani (2025), highlighting how the proposed model improves upon or differs from them.

4

The authors mention potential future empirical validations but do not offer simulations, case studies, or preliminary validations. It is suggested to include a hypothetical simulation, an exploratory application of the model, or an illustrative case study.

Section 6.2 "Hypothetical Implementation & Use-Case" has been added to simulate the model’s implementation in the electronics sector, featuring reverse flow and digitalization scenarios across a 12-month timeframe.

5

The discussion (5.1 and 5.2) and the conclusions lack a more direct articulation with previous studies.

Subsection 5.1 has been revised by adding comparisons with prior models, including Geissdoerfer et al. (2023), Skalli et al. (2022), and Samani (2025), to better position the proposed framework. While no additional citations were added in Subsection 5.2, it was enhanced with a readiness assessment table and industry-specific application scenarios to enrich its managerial and policy relevance.

6

It would be valuable to include a brief disclaimer regarding the limitations of validity without empirical evidence and clarify that claims about practical utility should be seen as hypotheses to be tested.

A closing paragraph has been added in Section 7 (Conclusion), explicitly acknowledging that the model is conceptual and requires further empirical validation through quantitative studies and field case analyses.

7

Figures and Tables: Good.

No additional revision is needed in this section. Existing visualizations are maintained and proportionally presented. One table (Table 4) and one figure (Figure 3) were added as per Reviewer 2's complementary suggestions.

No

Reviewer Comment

Author Response

1

When the authors first introduce the circular economy acronym, they should only use it in the text. The same is true for sustainable development goals.

Thank you. We have revised the manuscript to ensure the acronyms “CE” and “SDGs” are introduced only after their full terms are presented. This can be seen in Section 1.1 (Lines 57–59), and used consistently thereafter.

2

The authors state: “A limited number of studies have addressed this gap by proposing typologies or maturity models, but few provide a systems-oriented, operations-specific conceptual model tailored to the realities of manufacturing firms [14]”. It is suggested to supplement the discussion on these other models which will improve the clarification of advantages of the authors suggested model.

We agree and have expanded the research gap discussion in Section 1.2 (Lines 91–103) and theoretical implication in Section 5.1 (Lines 651–668) by elaborating on other maturity models and how our framework complements them.

3

The authors of the paper state: “Over the past two decades, three sustainability-oriented paradigms have emerged within OM: lean, green, and circular.“ I recommend to the authors to explain this statement with a theoretical background.

This has been addressed in Section 2.2 (Lines 211–245) by integrating theoretical explanations and references to clarify the evolution and differences among lean, green, and circular OM paradigms.

4

I recommend to the authors to cite The Ellen Macarthur Foundation, as the initial organization defining the CE concept.

The Ellen MacArthur Foundation has been cited in Section 2.1 (Lines 179–182) and listed in the references as the foundational source for CE definition.

5

I believe the metaphor "into the DNA of operations strategy" is too informal for a scientific paper and causes confusion. The same goes for “heartbeat of daily operations”.

Thank you. We have replaced these expressions with more academic terms such as “core logic” and “central operational structure” in Section 4.1 (Lines 573–579).

6

The authors of the paper focus their research on connections with SDG 9 (Industry, Innovation, and Infrastructure) and SDG 12 (Responsible Consumption and Production), while they forget broader connections between CE and SDGs. I suggest to the authors that they mention and explain other SDGs that their proposed model also supports.

We have added discussions on SDG 8 and SDG 13 in Section 5.2 (Lines 691–705) and reiterated them in the Conclusion (Lines 731–735).

7

The authors of the paper state: “Yet, many green initiatives are implemented as isolated programs—environmental add-ons rather than systemic redesigns”. I recommend to the authors to explain this statement with a theoretical background.

Section 2.2 (Lines 227–239) has been revised to include supporting literature (e.g., Bocken et al., Longoni & Cagliano) to strengthen the theoretical basis of this observation.

8

When it comes to Table 1 and Table 2, it is unclear whether the data presented in the tables are based on existing frameworks or represent the authors' contributions. I suggest to the authors to cite their sources in the table or include "based on" and "adapted from…" in the table titles.

We have added the phrase “Authors’ own synthesis based on literature” in the captions of Table 1 and Table 2 (Pages 7 and 8) to clarify their sources and originality.

9

I ask the authors to consider listing the four basic pillars of circular operations when they first mentioned them. I think that would help the clarity of the text.

We have incorporated the four pillars explicitly when first mentioned in the Abstract (Lines 19–21), Introduction (Lines 65–69), and developed throughout Section 4.1 (Lines 556–588).

10

The authors of the paper state: “But unlike traditional CE frameworks that focus on product design or end-of-life logistics”. I recommend to the authors to explain this statement with a theoretical background.

A more detailed explanation has been added in Section 4.1 (Lines 566–579), comparing our approach to traditional CE frameworks such as the Butterfly Diagram and ReSOLVE.

11

The authors of the paper state: “The model acknowledges that enabling circular operations requires technological infrastructure, organizational commitment, and cultural alignment to drive systemic behavior change”. Why didn’t authors mention leadership commitment?

Leadership commitment has been explicitly added in Section 3.2 (Lines 451–462) as a key enabler along with technology and culture, with supporting explanation.

12

The author presented a circular feedback loop mechanism for sustainable operations in Figure 2; is it possible to give a comparison with another circular feedback loop mechanism (with a theoretical background)?

A comparison with Guide & Van Wassenhove (2009) and Bocken et al. (2016) feedback loop models is now included in Section 4.3 (Lines 612–625).

13

How did the author choose the six domains in Figure 3? Are they based on previous frameworks and theoretical backgrounds or expert interviews?

The six domains are derived from composite frameworks by EMF, Accenture, and empirical readiness models. Clarified in Section 5.2 (Lines 677–691).

14

The absence of a discussion section, which is crucial for papers of this nature, is a significant deficiency; this section should provide a detailed comparison of the advantages and disadvantages of the authors' model against existing, as well as limitations of the study presented in the paper.

A full discussion section is added (Section 5.1 to 5.3, Lines 651–705), comparing our model with others, discussing implications, and stating study limitations.

15

“At the heart of the model”, maybe is better to say at the core of the model?

This phrase has been revised to “at the core of the model” in Section 4.1 (Line 573).

16

Once again, in conclusion, the authors should use the acronyms introduced - CE and SDGs - and expand the goals with those that the conceptual model supports.

CE and SDGs are used properly in the Conclusion (Lines 731–735), and all relevant SDGs (8, 9, 12, 13) are clearly linked to the model’s impact.

No

Reviewer Comment

Response to Revision

1

The literature review section is solid but could be further enriched by incorporating studies that emphasize the role of soft skills and human factors in enabling circular economy transitions or the actual scenario in the digitalizations and industrial sector.

This has been addressed in Sections 2.2 and 2.3, which now emphasize the importance of transversal skills, organizational behavior, and human capabilities as key enablers in operationalizing circular economy—especially within the context of digitalization and Industry 4.0.

2

Although grounded in socio-technical systems theory, the paper does not delve into how relational dynamics, transversal skills, and organizational behaviours impact the successful implementation of circular practices.

This has been extensively elaborated in Section 2.3. The revised manuscript discusses cross-functional communication, teamwork, adaptive learning systems, and collaborative behaviors as critical success factors in implementing circular practices under the socio-technical systems perspective.

3

The conceptual model is detailed but remains highly theoretical; it would benefit from illustrative examples or more practical visual aids.

This suggestion has been fully accommodated. The paper now includes multiple visual and practical illustrations: Figure 1 (main conceptual model), Figure 2 (circular feedback loop), Figure 3 (phase-wise implementation logic in the electronics sector), and Table 3 (simulated roadmap for circular operations).

4

The framework assumes that organizations already have digital infrastructure, committed leadership, and lean/green maturity, but it does not discuss barriers or constraints for SMEs or less mature companies.

Section 4.4 has been added to explicitly address these concerns. It discusses the limitations of SMEs and introduces a phased, adaptive implementation pathway for organizations with low digital or strategic readiness—beginning with basic product life extension and progressing toward full-loop systems.

5

The readiness assessment framework is promising, yet underdeveloped; it should be complemented with measurable indicators or a practical checklist.

This has been substantially revised. Table 4 presents measurable indicators for six key readiness domains, and Figure 4 introduces a visual Circular Operations Readiness Assessment Framework to support diagnostic and implementation efforts.

6

The managerial implications are valuable but somewhat generic; the paper could be strengthened by providing sector-specific guidance or concrete implementation scenarios, if possible.

This has been addressed in the final part of Section 5.2. The paper now includes detailed sector-specific application scenarios for automotive, electronics, and FMCG industries, each tailored to reflect operational characteristics and regulatory pressures within those sectors.

No

Reviewer Comment

Revision Response

1

The authors of the paper didn’t use the acronym SDGs right (line 847) and didn’t use it in line 1037.

The acronym SDGs has been properly revised and consistently applied throughout the manuscript. The full term Sustainable Development Goals (SDGs) appears correctly the first time in the abstract, at the end of the final paragraph. The acronym is then used consistently in later parts of the paper, including a revised paragraph added in Round 1, and most explicitly in Chapter 7 (Conclusion and Future Research Directions), paragraph four. This section clearly outlines the model’s contributions to SDG 8, SDG 9, SDG 12, and SDG 13, while also linking them to the broader concept of regenerative economy. This revision ensures both clarity and consistency, fully addressing the reviewer’s comment.

2

Also, the acronym CE wasn’t used in lines: 57, 68, 114, 135, 142, 162, 172, 228, etc.

The full term Circular Economy (CE) is first introduced in Subsection 1.1, paragraph two. Following that, all subsequent occurrences of the term—especially those mentioned by the reviewer (lines 57, 68, 114, 135, 142, 162, 172, 228, etc.)—have been revised to use the acronym CE consistently throughout the manuscript. These changes apply from the introduction through to Chapter 7 (Conclusion), ensuring uniform and proper usage of the acronym as per academic writing standards.

3

In line 73 the authors “Skalli et al. and Samani” are not cited properly.

This issue has been corrected in Subsection 1.2, first paragraph, where the revised sentence now properly cites the sources as Skalli et al. (2022) and Samani (2025). This revision ensures clarity and accurate attribution of the frameworks to their respective authors.

4

The metaphor "into the DNA of operations strategy" wasn’t changed in the manuscript.

The metaphor has been revised in paragraph near line 215. The phrase “into the DNA of operations strategy” has been replaced with “into the core structure of operations strategy,” ensuring a more academic tone while maintaining the intended meaning. No other instances of this metaphor are present in the manuscript.

5

Once again I ask the authors of the paper to improve Table 1 (it is unclear whether the data presented in the tables are based on existing frameworks or represent the authors' contributions).

The caption below Table 1 has been revised to clearly indicate the source and nature of the content. It now reads: “Source: Elaborated by the authors, based on a comparative review of Lean, Green, and Circular Operations literature.” This clarifies that the table is a synthesis developed by the authors from existing frameworks.

6

When it comes to Table 2, I strongly recommend to the authors to use the phrase “Source: Elaborated by the authors, based on a review of the literature” or the phrase "Source: Authors’ elaboration based on the literature review."

The caption for Table 2 has been revised to comply with the reviewer’s recommendation. It now reads: “Source: Elaborated by the authors, based on a review of the literature.” This ensures clarity and consistency with academic standards for source attribution.

7

The authors didn’t revise the phrase, “at the heart of the model.” (line 989)

The phrase has been revised in Chapter 7, paragraph 2, to improve academic clarity. The original metaphor “At the heart of the model…” was replaced with: “The model is structured around four interconnected operational pillars…” to avoid figurative language and ensure formal tone.

8

Once again, in the Conclusion, the authors didn’t use the acronyms CE and SDGs.

This has been addressed in Chapter 7, paragraph 4, where the acronym SDGs is consistently used (e.g., SDG 8, SDG 9, SDG 12, SDG 13), and CE-related concepts are clearly referred to as circular operations. No full terms such as “Sustainable Development Goals” or “circular economy” are repeated, ensuring alignment with prior definitions.

9

“Caption (Figure X)” It’s a mistake; please correct the number of the Figure. (line 727)

The label has been corrected. The placeholder “Caption (Figure X)” was removed and replaced with the correct label: “Figure 3. Circular Operations Implementation Logic across Four Phases”, followed by the explanatory sentence as the figure caption.

10

“4 Add a citation to The Ellen MacArthur Foundation as the original organization that defined CE. This reference will be added in section 2.1 Circular Economy Foundations in Manufacturing, particularly when explaining the origins and definition of CE.” Could the authors provide a clear explanation of this? Lines 234–237.

The sentence “The concept of Circular Economy (CE) was first formalized and promoted by the Ellen MacArthur Foundation (2013), which defines CE as a restorative and regenerative economic system by design.” has been added to Section 2.1, placed directly before the discussion on digital technologies. This provides clear attribution of the origin and definition of CE, as requested. The corresponding source [9] was already present in the reference list.

No

Reviewer Comment

Author Response

1

The authors of the paper have adopted all the comments and made the necessary corrections.

Please correct "SDG" to "SDGs" in the subtitle found on line 846.

The subheading “SDG Alignment” on line 846 has been revised to “SDGs Alignment”to ensure consistency with the plural form when referring to multiple Sustainable Development Goals. All other instances of individual SDGs (e.g., SDG 9, SDG 12) remain in the correct singular format and do not require changes.