Cradle-to-Grave LCA of In-Person Conferences: Hotspots, Trade-Offs and Mitigation Pathways

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I thank the authors for their thoughtful conceptualization of the studies and the work reported, which can be improved by the following suggestions.

1. The authors should provide the descriptive meaning of each term at first mention in the abstract, highlight, and main manuscript.
2. The authors may consider changing the word ‘gain’ to a less ambiguous word for quick understanding. Lines 23 - 24: ‘Further gains require harmonised functional units, improved digital-infrastructure inventories and integration of social impact metrics.’
3. Lines 65 – 67 need a verifiable reference.
4. The authors need to rewrite this section of their manuscript to ensure that the right research problem has been addressed in their studies as the heterogeneity of the two case studies are not satisfactory enough for the comparison that answers the question of the identified research gap….lines 96 – 108 ‘.. a robust comparative analyses between different events remain limited, mainly due to differences in system boundaries, functional units and data quality between studies. The present work responds to this gap. A harmonized cradle-to-grave LCA was conducted on two conferences that differ markedly in geographical scope: the RE-TECH national meeting in Pisa, Italy, and the YES-Europe Annual Conference in Athens, which attracts delegates from across the continents...’
5. On lines 121 – 125, the functional unit's definition is unclear.
6. The authors may consider including a section or incorporation within section 3.4 in their manuscript that discusses enabling policy that sets a threshold of environmental footprints for local, national, and international conferences.
7. The authors should try to harmonize terms like ‘global’ or ‘international’ and other applicable terms throughout the manuscript.
8. The authors need to provide relevant equations on the impact assessment with categorization factors, normalization, and weightings.

 

Author Response

The author thanks the reviewer for the time and the attention put into our manuscript revision. For all the comments raised, we provided a "response to reviewer" document, where we included a specific response for each of your comments. The document is attached.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1.Although the article highlights the advantages of hybrid meetings, it lacks a systematic comparative analysis of different meeting models. For instance, the impact of factors such as different meeting sizes, durations, and participant numbers is not analyzed in depth. The research data mainly come from individual cases, with a small sample size, which may affect the generalizability of the study. 3. Provide detailed steps and parameter settings for the LCA method to enhance the reproducibility of the research 4. Add more case data and incorporate 10.1109/JIOT.2025.3566952

Comments on the Quality of English Language

Could be improved

Author Response

The author thanks the reviewer for the time and the attention put into our manuscript revision. For all the comments raised, we provided a "response to reviewer" document, where we included a specific response for each of your comments. The document is attached.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This study conducts a systematic LCA comparing the environmental impacts of national and international scientific conferences. The research question is timely, the methodology is robust, and the conclusions are well-supported. The topic is very interesting and may be bound to elicit more profound social contemplation on the green planet. While there may be some improvement in analysis methodology, policy relevance etc.

1. That would be much better if virtual/hybrid conference could be a comparison, missing an opportunity to evaluate digital alternatives.
2. If the paper could generate some policy recommendations for EU decarb commissions, such as carbon offsetting, green transportation incentives etc. specific mitigation measures, that would be better.
3. It would be helpful or convincing if some social dimensions evaluation could be added, such as balance of green conference vs economy stimulation etc.

Looking forward to your feedback. Thanks.

Author Response

The author thanks the reviewer for the time and the attention put into our manuscript revision. For all the comments raised, we provided a "response to reviewer" document, where we included a specific response for each of your comments. The document is attached.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Authors, 

the topic your paper addressed is both interesting and important as it holds importance for both academic researchers and practitioners in the field of sustainability. The reviewed paper presents a comparative Life Cycle Assessment (LCA) of two scientific conferences, one national (RE-TECH in Pisa, Italy) and one international (YES-Europe Annual Conference in Athens, Greece), with the aim of quantifying their environmental impacts and identifying hotspots. The study employs a harmonized cradle-to-grave LCA approach, adhering to ISO 14040/44 standards and utilizing the Environmental Footprint 3.1 method for impact assessment. 
The title is well worded and corresponds to the content of the paper. The keywords are proper. The paper follows a logical and widely accepted academic structure. 

The paper, despite the undoubted value derived from the provided survey, has some shortcomings. Below you can find my comments and suggestions that can help to refine several aspects, what can be beneficial to elevate the paper's overall scientific rigor and clarity.

1.    While the paper justifies the exclusion of impacts associated with food consumed, use of toilets, and overnight accommodation by arguing comparability with participants' activities outside the event, these are often significant contributors to the environmental footprint of large events. Their exclusion, even with justification, might lead to an underestimation of the total environmental impact and limit the comprehensiveness of the "cradle-to-grave" claim. The argument that these impacts would be comparable outside the event might not hold true for all scenarios (e.g., specialized catering for the event could have a significantly different impact than an individual's typical meals). This exclusion limits the comprehensiveness of the "cradle-to-grave" assessment and should be properly discussed and justified.
2.    The reliance on external catering services making it "impractical to quantify accurately" food amounts consumed is a notable limitation. While single-use packaging and dish-washing operations were included (according to information on page 4 line 155-156), the primary impact of food production and consumption itself is missed. 
3.    Inferring waste generation from the mass of resources consumed, "under the assumption of correct source-segregation for every fraction," introduces a potential source of inaccuracy. Real-world sorting and recycling rates can vary significantly.
4.    The statement on page 11, lines 303-305 that "the end-of-life stage is negligible (0%) across all three categories [for IC], likely reflecting data gaps or the application of a cut-off modelling approach" indicates a potential weakness in the data for the international conference, which could affect the overall accuracy of its impact assessment. 
5.    While the exclusions have been justified, the paper does not present a sensitivity analysis to show how the inclusion of these excluded categories (food, accommodation, toilets) might alter the overall results or the identified hotspots. This would strengthen the argument for their exclusion or highlight the magnitude of the omitted impacts.
6.    While the comparison between national and international conferences is valuable, the study only includes two specific events. Generalizing these findings to all national and international conferences might be challenging without a broader range of case studies. The specific logistical and operational practices of these two conferences might not be representative of all events.
7.    The use of structured questionnaires for participant travel data (origin, destination, distance, modes) relies on self-reporting, which can be subject to recall bias or inaccuracies. The paper acknowledges this as a general bottleneck in section 3.4 ("Incomplete activity data"), but its specific impact on the results of this study is not quantified.
I believe that addressing these points will significantly elevate the impact and utility of your research. Good luck!

Author Response

The author thanks the reviewer for the time and the attention put into our manuscript revision. For all the comments raised, we provided a "response to reviewer" document, where we included a specific response for each of your comments. The document is attached.

Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

If you had compared an online conference with those in person, that would make sense. Also, meetings on "climate changes" by politicians and their usage of jet charters and the calculation of it's impact on pollution of the environment, that would be really great.

Also, if you'd have data on real reasons for attending conferences (acquired by survey) that would be great.

Data presented in your paper are interesting but also expected.

Comments for author File: Comments.pdf

Author Response

The author thanks the reviewer for the time and the attention put into our manuscript revision. For all the comments raised, we provided a "response to reviewer" document, where we included a specific response for each of your comments. The document is attached.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors are really appreciated for the revision made and the uniqueness of contributions of their study in the current paradigm.