Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article provides a bibliographic analysis of scientific papers that explore the concept of Digital Product Passport. It examines the journals in which these papers appear, their authors, countries of origin, counts of citations, and the frequency of certain words within the articles. At this stage, the main contribution of this article lies in demonstrating the intensity of research in this field, as well as its geographical distribution. The article would have been of greater value if it had analyzed the content of the papers, including the theories used, the methodological approaches adopted, and the main conclusions drawn.

To enhance the paper’s contribution the authors could consider the following amendments:

• Add a section to analyze the content, methodological approach and main conclusions of the examined papers.
• Strengthen section 5 (Discussion) by incorporating insights related to the above analysis.
• Improve the conclusions section accordingly.
• Consider erasing the Digital Product Passport keyword from section 4.2.1 (keyword synchronicity), as it is the main search term used by the authors to identify relevant papers.

Author Response

Comment 1:
The article would have been more valuable if it had analyzed the content of the articles, including the theories used, the methodological approaches adopted, and the main conclusions drawn.

Response 1:
Thank you for this valuable comment. We fully agree with this observation. Accordingly, we have added a new subsection (Section 4.3, page 21, shown in red in the revised manuscript) presenting a systematic content analysis of the 81 articles in the dataset. This section summarizes the research methods, theoretical frameworks, and key findings. Figures 15–17 and Table 8 have also been added and are marked in red to visually present these results, thereby providing a deeper understanding of the knowledge base of DPP research.

Comment 2:
Strengthen Section 5 (Discussion) by including comments related to the analysis above.

Response 2:
We agree and have accordingly revised Section 5 (Discussion, page 26, paragraph 1, highlighted in red) to incorporate the results of the content analysis. The revised section elaborates on the predominance of conceptual studies, the theoretical focus on circular economy and lifecycle thinking, and the underrepresentation of technology-specific research, highlighting the need for empirical validation. 

Comment 3:
Improve the Results section accordingly.

Response 3:
Thank you for this suggestion. We have revised Section 6 (Conclusions, page 26, paragraph 2, marked in red) to integrate the insights gained from the content analysis, highlight the interdisciplinary nature of DPP research, and present a structured agenda for future studies. The revised section now provides specific recommendations on sectoral architectures, user-centered design, technology integration, governance models, and impact assessment metrics.

Comment 4:
Consider deleting the keyword “Digital Product Passport” from Section 4.2.1 (keyword concurrency).

Response 4:
For reasons of methodological transparency, we respectfully decided to retain the keyword “Digital Product Passport” in Section 4.2.1 (page 17, paragraph 3), as this was the primary search term used for constructing the dataset. However, we have added a clarifying note (highlighted in red in the revised manuscript) indicating that its high frequency is expected and should be interpreted with caution to avoid overstating its novelty.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study provides a timely bibliometric analysis of Digital Product Passport (DPP) research (2021–2025) and effectively maps core trends. However, several areas require refinement to enhance rigor, comprehensiveness, and practical relevance.  

1. The study relies solely on Scopus for data collection but fails to justify excluding other core databases (e.g., Web of Science, IEEE Xplore) that cover technical DPP-related research (e.g., IoT, blockchain). This may introduce selection bias. Clarify Scopus’s exclusivity or expand data sources to 1–2 complementary databases for holistic field representation.  
2. The “limited technology-specific keywords” gap (4.2.1) is noted but not explained. Address why terms like “blockchain” are underrepresented and supplement Figure 11 with metrics to identify latent thematic clusters.  
3. The call for interdisciplinary DPP research lacks empirical support. Analyze author disciplinary backgrounds or quantify cross-disciplinary collaboration to ground this claim in data.  
4. The Twin Transition Framework (Figure 15) lacks operational detail. Add 1–2 sector-specific use cases to show how DPP design adapts to industry differences, enhancing practical relevance.  
5. The country collaboration analysis (4.2.3) does not quantify Germany’s “leading collaboration”, g., co-authored article counts or citation impact of cross-country work. Also, contextualize non-European underrepresentation to enrich global dynamics.

Author Response

Comment 1:
The study relies solely on Scopus for data collection, but this does not justify excluding other primary databases (e.g., Web of Science, IEEE Xplore) that cover technical DPP-related research (e.g., IoT, blockchain). This could lead to selection bias. Clarify the exclusivity of Scopus or expand the data sources to 1–2 complementary databases for holistic field representation.

Response 1:
Thank you for this important comment. To ensure broader coverage and minimize selection bias, we expanded our dataset to include publications from both Scopus and Web of Science, applying this update to all analyses. This change is explained in Section 3 (Materials and Methods, page 7, paragraph 2, marked in red), where we describe the inclusion of WoS data and the careful removal of duplicate records prior to analysis, and in Section 4 (Results, page 8), where the updated analyses are presented.

Comment 2:
The "limited technology-specific keywords" gap (4.2.1) is noted but not explained. Explain why terms like "blockchain" are underrepresented and support Figure 11 with metrics to identify latent thematic clusters.

Response 2:
We agree and have revised Section 4.2.1 (page 18, paragraph 1, highlighted in red) to provide a more detailed explanation of the underrepresentation of technology-specific keywords. To support this, we have added Table 6 (page 18) with keyword frequencies and strengthened the interpretation of Figure 11 by describing the latent thematic clusters. These revisions clarify that the technology gap reflects the conceptual and policy-focused nature of most existing studies, with relatively few technical implementation articles published to date.

Comment 3:
The call for interdisciplinary DPP research lacks empirical support. To support this claim with data, analyze the authors' interdisciplinary backgrounds or measure interdisciplinary collaboration.

Response 3:
Thank you for this constructive suggestion. We have added Table 8 (page 21, highlighted in red), which summarizes the disciplinary backgrounds of the 10 most productive authors, using information from their institutional profiles, ORCID records, and academic biographies. This addition provides empirical evidence of the cross-sectoral and interdisciplinary nature of DPP research and supports our argument for further interdisciplinary collaboration.

Comment 4:
The Twin Transitions Framework (Figure 15) lacks operational details. Include one or two sector-specific use cases to illustrate how the DPP design adapts to sector differences and enhances its practical relevance.

Response 4:
We agree and have enriched Section 5 (Discussion, page 25, paragraphs 3–4, highlighted in red) by adding sector-specific use cases from real-world DPP pilot projects (textiles, electronics, and construction) based on recent sectoral reports (e.g., Sitra, 2024). Figure 18 and its accompanying text have been updated to illustrate how the twin transition framework can be operationalized across multiple industries, thereby enhancing the practical relevance of our findings.

Comment 5:
The country collaboration analysis (4.2.3) does not quantify Germany's "leading collaboration," such as the number of co-authored articles or the citation impact of cross-country studies. Furthermore, contextualize the underrepresentation of non-European countries to enrich global dynamics.

Response 5:
We have revised Section 4.2.3 (pages 19–20, paragraph 1, highlighted in red) to include a table presenting co-authorship counts and citation impact data for German collaborations. We also added a contextual explanation for the relatively low participation of non-European countries, noting that this reflects the European policy-driven origin of the DPP concept and that participation is expected to grow as global adoption accelerates.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The paper has been significantly improved, and all comments from the initial review have been addressed.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript has been sufficiently improved.