Review Reports

Round 1

Reviewer 1 Report

The manuscript presents a study of residual materials left in plastic recipients collected from a recycling facility.

The introduction is brief, but the scope of the study is clearly defined. This section could be improved by explaining the impact of residual goods on the recycling process and the quality of the recycled material.

2. Materials and methods

Lines 61-63 Please specify that Figures A1, A2, A3, A4 are included in the Appendix. Why is there an Appendix A "not applicable" and then pictures go to Appendix B? There should be only one appendix in this case.

Please include one more section 2.3 where you describe how data were processed and what software you used.

The results are clearly presented and they are highly relevant.

The discussion compares the results with data from other papers and highlights that actual values are lower than those from lab studies.

The conclusions are brief and could be expanded by suggesting solutions for improvement, maybe policy changes or even, in some cases reassessment of actual recycling potential. For instance in the case of toothpaste tubes the amount of residual material exceeds the package weight. Maybe consumers should be instructed to cut and wash the tubes or not put them in the recycling bin.

There are many spelling mistakes in the texts, so it should be thoroughly revised.

Author Response

“The manuscript presents a study of residual materials left in plastic recipients collected from a recycling facility.

The introduction is brief, but the scope of the study is clearly defined. This section could be improved by explaining the impact of residual goods on the recycling process and the quality of the recycled material.”

We added more information about the meaning of residues for recycling. Even though it is obvious that residues cause additional weight and organic contamination of waste water during washing we could not find more, relevant, citable information after evaluation of sources.

 

2. Materials and methods

“Lines 61-63 Please specify that Figures A1, A2, A3, A4 are included in the Appendix. Why is there an Appendix A "not applicable" and then pictures go to Appendix B? There should be only one appendix in this case.”

We amended this part.

 

“Please include one more section 2.3 where you describe how data were processed and what software you used.”

We added the required information.

“The results are clearly presented and they are highly relevant.”

“The discussion compares the results with data from other papers and highlights that actual values are lower than those from lab studies.”

“The conclusions are brief and could be expanded by suggesting solutions for improvement, maybe policy changes or even, in some cases reassessment of actual recycling potential. For instance in the case of toothpaste tubes the amount of residual material exceeds the package weight. Maybe consumers should be instructed to cut and wash the tubes or not put them in the recycling bin.”

We added a sentence. It is paradox that it is not recommended to clean packagings before disposal. Better, easy emptying solutions might be more relevant.

 

Reviewer 2 Report

Plastic packaging represents a large proportion of the plastic consumption throughout the world. The negative environmental impact associated with plastic packaging waste can be in part abated by recycling plastics. In this case, it is important to determine the size of the package for the product in plastic packaging. The reviewed paper (manuscript ID: waste-2569817, titled: Fill product residues in sorted plastic packaging fractions for recycling) presents results in the field plastic recycling. I have found the paper to be interesting. The authors of the manuscript focused on determining the content of residues of various commodities in plastic packaging intended for recycling. The obtained results can help to optimize the packaging of the commodity, which is the benefit of this manuscript. I appreciate the effort that the authors have put in performing this study. I have no objections against the work by essence, but in my opinion:

1. Please consider reviewing the abstract and highlighting novelty, as there are really few studies on this topic.

2. The conclusion perhaps considers using bullet points (2-3 bullet points) can be considered.

3.  In general, what is the reproducibility of those experiments?

Author Response

“Plastic packaging represents a large proportion of the plastic consumption throughout the world. The negative environmental impact associated with plastic packaging waste can be in part abated by recycling plastics. In this case, it is important to determine the size of the package for the product in plastic packaging. The reviewed paper (manuscript ID: waste-2569817, titled: Fill product residues in sorted plastic packaging fractions for recycling) presents results in the field plastic recycling. I have found the paper to be interesting. The authors of the manuscript focused on determining the content of residues of various commodities in plastic packaging intended for recycling. The obtained results can help to optimize the packaging of the commodity, which is the benefit of this manuscript. I appreciate the effort that the authors have put in performing this study. I have no objections against the work by essence, but in my opinion:”

“1. Please consider reviewing the abstract and highlighting novelty, as there are really few studies on this topic.”

We added a sentence.

“2. The conclusion perhaps considers using bullet points (2-3 bullet points) can be considered.”

Some reviewers criticise bullet points wherefore we decided not to use them.

“3.  In general, what is the reproducibility of those experiments?“

We added a part in the conclusions about the limitations of this study. The reviewer is right, the reproducibility is not clear and worth to be examined in further studies.

Reviewer 3 Report

I think the topic of this study is good and very meet the area of journal Waste. But I think the current manuscript cannot meet the publication requirement, especially for the language. I hope the authors could carefully revise their manuscript, and kindly considered and addressed my comments.

1. Title. I think the current title is confusing. What did the authors hope to recovery the filled product or sorted plastic waste?  Combining the research content, I suggest to use titles like “Situations of the recovery of sorted plastic package fractions with filled product in Germany ". I hope the authors could revise the title basing their research purpose.

2. I know that the authors are from Germany, and English was not their mother tongue. I suggest the authors seek the help from native speakers or the MDPI language service before they submit the revised version of manuscript.

3. The emphasis of the study is unclear. The authors should state why they take the filled products residues into consideration of sorted plastic waste recovery. How the filled products residues affect plastic waste recovery.

4. The current introduction doesn’t seem complete and serious.  The authors need to state the backgrounds of the relevant areas, the key issues need to be considered/solved, and their innovation solution for the issues/the benefits from their research. The current introduction is poor and need to be re-writed.

5. What is Post-consumer, I cannot understand. In addition, detailed information of the Dual System need to be given. In line38-39, I suggest not use the direct discourse in the text. Line 47, [...]?? In addition, line 53-54, the final purpose is to determine the unavoidable losses during waste recovery?

6. I think the result and discussion is relatively OK, but the introduction is not suitable for the result and discussion. I hope the revised introduction can explain why the author need to do such investigations. When submitting the revised version of this manuscript, better to cite https://doi.org/10.3390/polym15122741   into the article.

7. avoid using any citations in the conclusion.

 

I think the topic is important for practical waste plastic recovery. The quality of the manuscript is poor. The introduction did not match their results and discussion. I think the author should make a major revision on their manuscript.

Author Response

“I think the topic of this study is good and very meet the area of journal Waste. But I think the current manuscript cannot meet the publication requirement, especially for the language. I hope the authors could carefully revise their manuscript, and kindly considered and addressed my comments.”

“1. Title. I think the current title is confusing. What did the authors hope to recovery the filled product or sorted plastic waste?  Combining the research content, I suggest to use titles like “Situations of the recovery of sorted plastic package fractions with filled product in Germany ". I hope the authors could revise the title basing their research purpose.”

The title was changed.

“2. I know that the authors are from Germany, and English was not their mother tongue. I suggest the authors seek the help from native speakers or the MDPI language service before they submit the revised version of manuscript.”

We checked and improved the language.

“3. The emphasis of the study is unclear. The authors should state why they take the filled products residues into consideration of sorted plastic waste recovery. How the filled products residues affect plastic waste recovery.”

We amended the chapter “Intention of the study”. From discussion with industry, we know that residues are relevant for values about recycling efficiencies. However, such information cannot be found in peer-review publications.

“4. The current introduction doesn’t seem complete and serious.  The authors need to state the backgrounds of the relevant areas, the key issues need to be considered/solved, and their innovation solution for the issues/the benefits from their research. The current introduction is poor and need to be re-writed.”

The “Introduction” was amended. The focus in this study was on the residue content at certain packagings and products. The aim was to identify materials where the emptying behavior or formulation of the fill product should be improved to reduce residue contents. A limiting factor is that not much is published about residue contents and its influence on recycling. More research is needed for such topics.

“5. What is Post-consumer, I cannot understand. In addition, detailed information of the Dual System need to be given. In line38-39, I suggest not use the direct discourse in the text. Line 47, [...]?? In addition, line 53-54, the final purpose is to determine the unavoidable losses during waste recovery?”

We took the term “Post-consumer” out. “Dual System” is a generic term for the companies that collect and sort packaging waste and transfer them to recycling processes.

“6. I think the result and discussion is relatively OK, but the introduction is not suitable for the result and discussion. I hope the revised introduction can explain why the author need to do such investigations. When submitting the revised version of this manuscript, better to cite  https://doi.org/10.3390/polym15122741 into the article.”

The introduction was amended. An issue here is that not much information about residues is published in peer-review publications.

The reference was added.

“7. avoid using any citations in the conclusion.”

Citations were taken out from the conclusions.

“I think the topic is important for practical waste plastic recovery. The quality of the manuscript is poor. The introduction did not match their results and discussion. I think the author should make a major revision on their manuscript.”

The manuscript was amended.

Round 2

Reviewer 1 Report

The authors have integrated previous recommendations in the current version of the manuscript.

English editing still required.

Author Response

By using an English editing software tool  English language of the manuscript was edited.

Reviewer 3 Report

I think the quality of this manuscirpt is well improved.

But the quality/resolution of Figure 1-5 was poor, and it is difficult for me to clearly read it. 

I suguest the author to revise the current figure, and then this manuscript could be considered for publication.

Quality of English was improved. 

Author Response

We increased the size of the figures to improve their resolution.