Evaluation of Biodegradability of Polylactic Acid and Compostable Bags from Food Waste under Industrial Composting

Round 1

Reviewer 1 Report

This study evaluated the biodegradability of polylactic acid and compostable plastic bags under industrial composting conditions. I think the overall framework of the paper is clear, the content is relatively complete, the research methods are scientific, and the results analysis is adequate. The study has certain innovations and practical values. However, further revisions and improvements are still needed. I would recommend major revisions before considering acceptance.

1. Abstract (Lines 12-29)

(1) Lines 12-15: The results description should directly state the specific data, such as the biodegradation percentage of PLLA.

(2) Lines 16-18: The specific mathematical model for the release kinetics could be provided.

(3) Lines 19-23: The functional groups involved in the mechanisms could be clarified.

(4) Lines 24-27: A conclusive statement highlighting the innovations should be added.

2. Discussion (Lines 492-512)

(1) Lines 499-501: Comparisons with other research results should be included.

(2) Lines 504-506: The discussion on the mechanisms needs to be expanded in detail.

(3) Lines 509-512: The research significance requires further elaboration.

3. Experiments (Lines 102-153)

(1) Lines 127-129: The synthesis methods need elaborate descriptions.

(2) Lines 131-134: More details are required for the extraction and purification steps.

(3) Lines 173-178: The testing methods need to be elucidated clearly.

4. Conclusions should concisely summarize the core innovations.

5. The reference formats need to be checked for compliance.

6. Some language expressions require further polishing.

Some language expressions require further polishing.

Author Response

We would like to thank the reviewers for their thoughtful comments. We have revised the manuscript based on their feedback. Please see the attachment. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Authors Names: corresponding author mark (*) missing

Line 48 - 52: Authors state: “Because petroleum-based polymers are non-biodegradable”, and “petroleum-based plastics, which are practically unbreakable, “ that is not true!  Polyemrs like PBS, polycaprolactone (PCL), polyvinyl alcohol (PVA) and polybutylene adipate terephthalate (PBAT), are fossil based and biodegradable, see Di Bartolo, A.; Infurna, G.; Dintcheva, N.T. A review of bioplastics and their adoption in the circular economy. Polymers 2021, 13, 1229

Line 96: should add FW abbreviation in line  15

Line 104, which is the difference between FW and FW1?  You already give the abbreviation of Food Waste in line 15 (see comment for line 96)

Line 111: “Com- 111 postable bag (CBB2B), produced using FW gathered from the Municipality of Heraklion in 112 the context of the B2B Project, was produced of ΡΒΑΤ with MFI=4-5 gr/10 min, 12% pol- 113 ylactic acid (PLLAB2B), produced using FW in the context of B2B, and various other active 114 ingredients.” Did the Authours published something about this process? Informations about this new materials are fundamental for the understanding of this paper and are not reported here. Authors even claimed “This study reports on the use of food waste in the creation of bioplastics” in conclusions sections, but there aren’t any informations about this.

Line 137: figure caption and caption should be in the same page

Line 156: did you monitored Methane as well? For PLA could be important

Line 165: Grammar correction neede: was consist = consisted

Line 218 What is PLLA B2Bp? Too many abbreviations, difficult to follow

Line 497: This study reports on the use of food waste in the creation of bioplastics: not clear, isn’t the manuscript about the decomposition of bioplastics? otherwise the manuscript is not clear about the creation of bioplastic. If you referred on the CBs  made by FW see comments on line 111

In general, English can be improved, difficult to follow, I strongly reccomend an English speaking native to revise the manuscript

Author Response

We would like to thank the reviewers for their thoughtful comments. We have revised the manuscript based on their feedback. Please see the attachment. 

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear authors,

Stating your project in the abstract has no value for the reader, which is not interested in your funding source, but in your results. Therefore, please revise and take out "Biowaste to Bioplastic (B2B) Project framework" from the abstract, which has to be concise and pinpoint the essential of the work.

Introduction is lacking citations. 

"Plastic waste accounts for global emissions in the range from 9 to 23 million metric tons annually in fresh and sea water" Citation

"These quantities are expected to double by 2025." Citation

“green” Citation

"petroleum-based plastics, which are practically unbreakable" Citation

"Polymer mineralization happens under aerobic microbial biodegradation conditions" Citation

Materials and Methods

Line 120: "was used with pretreatment" what was the pre treatment consisted of?

A basic microbiology assay should have been performed. Atleast an Community-Level physiological profile via Biolog Ecoplates or other basic means...

Please describe clearly and in a step by step manner the methods used for "Determination of Arsenic (As), Cadmium (Cd), Chrome (Cr), Mercury (Hg), Nickel  (Ni), Lead (Pb), Copper (Cu), Selenium (Se), Zinc (Zn) and Molybdenum (Mo) were carried out according to UNI EN 15411:2011 [27]. Determination of Fluorine (F) were carried out according to EPA 9056A (2007) [28]." as the citation are vaguely stating some methods suitable for the purpose.

Thank you

Author Response

We would like to thank the reviewers for their thoughtful comments. We have revised the manuscript based on their feedback. Please see the attachment. 

Author Response File: Author Response.pdf

Reviewer 4 Report

The manuscript “Evaluation of biodegradability of Polylactic Acid and Compostable Bags from Food Waste under Industrial Composting" is interesting and well written. The experiments are well designed and performed. Results are convincing and publication is recommended. I have some minor comments in order to improve the manuscript before to be published:

1.      Abstract section. the Abstract section seems to be a bit awkward. Some of the statements made are very subjective and unclear. For example, L 13-14, L 15-17.

2.      Did the authors test the optical changes of the compost in this study?

3.      The introductory part is lengthy and non-informative and the logic is muddled, in my opinion. It should be corrected carefully.

4.      L 43, “the first limitation …”, so is there the second and other limitation?

5.      L 48-52, the whole paragraph was muddled, and I did not see the causal relationship between the two sentences.

6.      L 86-88, “According to several studies,” cite these studies.

7.      L 95, the abbreviation of PLLA_B2B need to write the full name for the first time in the manuscript.

8.      L116-124, why the authors used two kinds of PLLA for the biodegradability tests and the disintegration test, respectively?

9.      “Table 4 provides weight of reactors at 0 and 91 days of test”. So what does that tell us?

10.   It seems that Figure 4 and 5 could be merged into one.

11.   Table 5 and 6, PLLAB2B1 and PLLAB2B2, they were not explained in the method section.

12.   Figure 6, can the authors tell the control and treatment group in the photo?

Extensive editing of English language required

Author Response

We would like to thank the reviewers for their thoughtful comments. We have revised the manuscript based on their feedback. Please see the attachment. 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I would like to thank the authors for the kind comments and revisions. The manuscript has been improved and can be accepted in the present form.