Safety Evaluation of Polyethylene Terephthalate Chemical Recycling Processes
Round 1
Reviewer 1 Report
The article concerns the current issue related to the safety of chemical recycling and the discussion of the balance between mechanical and chemical recycling. The presented research show at the problem from the legal, technical and chemical point of view, and it contains an interesting experimental part. A very high substantive level means that I do not make any comments on the content and the article can be published in this form.
Author Response
Dear reviewer, thanks for your review.
Reviewer 2 Report
It is clear that the work to be done in the field of recycling and reuse of PET packaging, which is one of the most used packaging materials, is very important for recycling and sustainability. The results of your study clearly show the productivity increase in PET recycling, which is of great importance in terms of sustainability.
Within the scope of this study, chemical recycling offers a new solution to increase PET recycling. For post-consumer recycling products in packaging applications, it is essential to ensure the safety of what is recycled and protect the health of consumers. Evaluation criteria for mechanical recycling processes have already been established. This study evaluates the safety of the chemical recycling process, similar to the approach of the European Food Safety Authority (EFSA). The results of the study clearly show the productivity increase in PET recycling, which is of great importance in terms of sustainability.
Author Response
Dear reviewer, thanks for your review.
Reviewer 3 Report
The submitted manuscript is original and it does expand the knowledge in the area of Environmental Sustainability and Applications. I believe it significantly build on (the author's) previous work and fits the scope of the journal. The methodology presented in the manuscript and analysis provided are accurate and properly conducted, however the writing style of the article needs to be significantly improved. Let us give you a couple of examples:
The introduction section comprises the first portion of the manuscript, and it should be written using the simple present tense. The author uses a mix of simple and past tenses like: “The aim of this study is to determine the cleaning efficiency of the investigated polyethylene terephthalate chemical recycling process based on the depolymerisation of PET and the repolymerisation to PET. Based on these cleaning efficiency data, the safety of chemical recycling processes was evaluated.
The first important conclusion of the research is: “the overall cleaning efficiency of a chemical PET recycling process are such high, that the cleaning efficiency can hardly be tested within one challenge test. The process steps, depolymerisation and repolymerisation, need to be tested in two separate challenge tests in order to determine the cleaning efficiencies of each of these two parts. Considering only the second part of the recycling process, the repolymerisation of PET, the cleaning efficiencies are >99.9% for all applied model substances.” However, what follows it is most definetly a part of discussion of the results and not the conclusion: “Such a high cleaning efficiency is enough to show, that the overall chemical recycling process can be considered as safe. This is in agreement with the preampel of the Recycling Regulation 282/2008, where it is mentioned that "monomers and oligomers resulting from chemical depolymerisation should not be treated differently from monomers manufactured by chemical synthesis. Therefore, they are covered by the authorisation of monomers and additives in Directive 2002/72/EC [remark, now Regulation 10/2011] and they should comply with the specifications and purity criteria established therein." This means that the same purity requirements apply as for virgin polymers without recyclate content. In addition, the US Food and Drug Administration eliminated all recommendations for chemical recycling processes in the actual Guidance document and FDA no longer recommends that such recyclers submit data for agency evaluation [23]. The FDA concludes, that "recycling of PET or PEN by methanolysis or glycolysis results in the production of monomers or oligomers that are readily purified to produce a finished polymer that is suitable for food-contact use."
Also, the author uses Automatic hyphenation mode throughout the manuscript inserting hyphens for words at the end of the line (de-rived, recol-lected, migra-tion, res-idues ….) making it very hard to follow and understand.
There are also spelling errors like “definetly”, “preampel”…etc.
Finally, it is most admirable (but also very unusual) to see that a single researcher was able to singlehandedly carry out all the tasks necessary to conduct and publish this complex research.
Author Response
The submitted manuscript is original and it does expand the knowledge in the area of Environmental Sustainability and Applications. I believe it significantly build on (the author's) previous work and fits the scope of the journal. The methodology presented in the manuscript and analysis provided are accurate and properly conducted, however the writing style of the article needs to be significantly improved. Let us give you a couple of examples:
The introduction section comprises the first portion of the manuscript, and it should be written using the simple present tense. The author uses a mix of simple and past tenses like: “The aim of this study is to determine the cleaning efficiency of the investigated polyethylene terephthalate chemical recycling process based on the depolymerisation of PET and the repolymerisation to PET. Based on these cleaning efficiency data, the safety of chemical recycling processes was evaluated.
The first important conclusion of the research is: “the overall cleaning efficiency of a chemical PET recycling process are such high, that the cleaning efficiency can hardly be tested within one challenge test. The process steps, depolymerisation and repolymerisation, need to be tested in two separate challenge tests in order to determine the cleaning efficiencies of each of these two parts. Considering only the second part of the recycling process, the repolymerisation of PET, the cleaning efficiencies are >99.9% for all applied model substances.” However, what follows it is most definetly a part of discussion of the results and not the conclusion: “Such a high cleaning efficiency is enough to show, that the overall chemical recycling process can be considered as safe. This is in agreement with the preampel of the Recycling Regulation 282/2008, where it is mentioned that "monomers and oligomers resulting from chemical depolymerisation should not be treated differently from monomers manufactured by chemical synthesis. Therefore, they are covered by the authorisation of monomers and additives in Directive 2002/72/EC [remark, now Regulation 10/2011] and they should comply with the specifications and purity criteria established therein." This means that the same purity requirements apply as for virgin polymers without recyclate content. In addition, the US Food and Drug Administration eliminated all recommendations for chemical recycling processes in the actual Guidance document and FDA no longer recommends that such recyclers submit data for agency evaluation [23]. The FDA concludes, that "recycling of PET or PEN by methanolysis or glycolysis results in the production of monomers or oligomers that are readily purified to produce a finished polymer that is suitable for food-contact use."
FW: Dear reviewer, I revised the manuscript to the points mentioned above.
Also, the author uses Automatic hyphenation mode throughout the manuscript inserting hyphens for words at the end of the line (de-rived, recol-lected, migra-tion, res-idues ….) making it very hard to follow and understand.
FW: Dear Reviewer, I used the Journals template for the manuscript. Automatic hyphenation is set as default. I will check this in the final proof.
There are also spelling errors like “definetly”, “preampel”…etc.
Finally, it is most admirable (but also very unusual) to see that a single researcher was able to singlehandedly carry out all the tasks necessary to conduct and publish this complex research.
FW: Dear reviewer, thanks for this very complimentary comment. I confirm that I solely worked on this manuscript at the conceptualization, methodology, data curation and writing of the manuscript. However, I introduced an acknowledgement section to thank two of my colleagues for experimental support of this study.
