Review Reports - Hazop Analysis of a Bioprocess for Polyhydroxyalkanoate (PHA) Production from Organic Waste: Part A

Round 1

Reviewer 1 Report

The manuscript is well organized and provides the results of a HAZOP analysis applied to the first process step (acidogenic fermentation) aimed at volatile fatty acids production.

I propose to publish this manuscript with minor revision in typos and text formatting.

Author Response

Response to Reviewer 1 Comments – Lauri R.

Point 1: The manuscript is well organized and provides the results of a HAZOP analysis applied to the first process step (acidogenic fermentation) aimed at volatile fatty acids production.

I propose to publish this manuscript with minor revision in typos and text formatting.

Response 1: Dear Reviewer 1, thank you for the good manuscript assessment. Typos and text formatting have been controlled and improved.

Best regards.

Reviewer 2 Report

The authors applied HAZOP, a tool that is commonly used in standardized operations, to assess a PHA production process. The manuscript is more like a technical report. There are some critical problems in the manuscript.

1. BioHazOp has been introduced by many studies but the authors did not cite any.

2. Only 1 node was performed. what was the deviation?

Author Response

Response to Reviewer 2 Comments – Lauri R.

Point 1: The authors applied HAZOP, a tool that is commonly used in standardized operations, to assess a PHA production process. The manuscript is more like a technical report. There are some critical problems in the manuscript.

BioHazOp has been introduced by many studies but the authors did not cite any.

Response 1: A specific paper is cited in the manuscript and reported in the References (number 10). Reference 10 is focused on BioHazOp application to biogas production process.

Point 2: 2. Only 1 node was performed. what was the deviation?

Response 2: The results of BioHazOp analysis, applied to the second step of PHA production process, are reported in another paper (Hazop analysis of a bioprocess for polyhydroxyalkanoate (PHA) production from organic waste: part B) submitted to the same special issue (lines from 118 to 121).

For the examined node, the process parameters (flow, temperature, HRT, pH, etc.) deviations (more, less, reverse, higher, lower, shorter, longer, etc.) from normal operating condition have been analyzed from an engineering standpoint, looking for causes, consequences and countermeasures.

The list of relevant deviations for the first node has been reported in Appendix A. Indeed, Table A2 minutely shows all the deviations and the HAZOP analysis results.

Author Response File: Author Response.pdf

Reviewer 3 Report

Article entitled Hazop analysis of a bioprocess for polyhydroxyalkanoate (PHA) production from organic waste: part A written by Roberto Lauri, Emma Incocciati, Biancamaria Pietrangeli, Lionel Nguemna Tayou, Francesco Valentino, Marco Gottardo, Mauro Majone and submitted to fermentation journal as a draft no 2093714 deals with an important issue of organic wastes reuse.

The article is in journal’s scope. Therefore, it could be considered for publication in Fermentation journal.

As English is not my native language, I am not able to assess language correctness.

However, while reading, I found some statements missing, confusing or unclear. Below I enclose the list of my comments.

HAZOP analysis general description (lines 85 – 199) should transferred to introduction. The article is about the use of a specific method for a specific purpose. The description of the method should be in the introduction, while in Materials and Methods there should be information on how in detail the Authors followed the general guidelines of the method, what specific actions were taken.

If the general information is properly moved into the introduction, it will be about 200 lines long, while the entire article is about 450 lines long. The proportions between the size of chapters, which are appropriate for a scientific article, are not maintained.

Tables 1 and 2 do not contribute much to the article and can be safely transferred to the supplementary material. On the other hand, almost all the work actually done by the Authors has been placed as Appendix A.

Figures A1 and A2 are of poor quality - poorly legible. It is worth adding a description of what exactly is in the drawing, not everything is clear.

The title of the article containing “part A” suggests that there will be more parts. The Authors do not specify what they will concern. I suggest either removing “part A” from the title, or at least mentioning somewhere in the article what exactly the next part will be about and where it will be published.

The list of references is relatively short - 26 items. These items are mostly current (published in 2018 or later, but many relatively old items are present). The participation of legal regulations is important. The cited scientific literature is quite poor, about 20 items.

Based on my comments and general impression, I suggest major revision.

Author Response

Response to Reviewer 3 Comments – Lauri R.

Point 1:

Response 1: as suggested by the Reviewer 3, a general HAZOP description (lines from 55 to 58 and lines from 62 to 99 in the revised manuscript) has been transferred to the “Introduction”, while in “Materials and Methods” there is the detailed description of the analysis technique and tools (checklist and BioHazOp). It follows that “Introduction” lines are 84, whereas the overall manuscript is 472 lines. In this way, the paper size proportions are maintained.

Point 2: Tables 1 and 2 do not contribute much to the article and can be safely transferred to the supplementary material. On the other hand, almost all the work actually done by the Authors has been placed as Appendix A.

Response 2: Table 1 has been deleted, whereas Table 2 (it becomes Table 1 in the revised manuscript) has not been transferred to Appendix A, because it represents the HAZOP analysis core and therefore its placement is appropriate in “Materials and Methods”. Indeed, Table 2 gives an immediate results visualization and useful information, which makes the Table A2 understanding clearer.

Point 3: Figures A1 and A2 are of poor quality - poorly legible. It is worth adding a description of what exactly is in the drawing, not everything is clear.

Response 3: The figures quality has been improved and additional lines (from 354 to 364) have been included in the paragraph 4.2. These lines are aimed at explaining the meaning of the letters, which are associated with the control devices (instrumentation) reported in Figure A2.

Point 4: The title of the article containing “part A” suggests that there will be more parts. The Authors do not specify what they will concern. I suggest either removing “part A” from the title, or at least mentioning somewhere in the article what exactly the next part will be about and where it will be published.

Response 4: This paper is focused on the results of BioHazop analysis applied to the first step (acidogenic fermentation) of PHA production process. The results of BioHazOp analysis, applied to the second step of PHA production process, are reported in another paper (Hazop analysis of a bioprocess for polyhydroxyalkanoate (PHA) production from organic waste: part B) submitted to the same special issue.

This explanation has been reported in the “Introduction” (lines from 118 to 121).

Point 5: The list of references is relatively short - 26 items. These items are mostly current (published in 2018 or later, but many relatively old items are present). The participation of legal regulations is important. The cited scientific literature is quite poor, about 20 items.

Response 5: the references list has been increased (33 items). The new references are included between number 17 and number 23. They are related to HAZOP studies.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

First of all, the authors did not provide ANY citation when the term "BioHazOP" first appeared. It sent a message that the 'BioHazOP' method was the most significant scientific contribution in the manscript. The authors should clear demonstrate how the HAZOP analysis has been modified and to what degree the analysis tool has been improved.

Author Response

A specific paper is cited in the manuscript and reported in the References (number 10). With reference to BioHazOp, an only paper has been found in literature (Reference n°10). This paper was published in 2018 and focused on BioHazOp application to biogas production process. Indeed, the manuscript novelty is the BioHazOp application to a PHA production process from organic waste. BioHazOp has been derived from HAZOP and the main difference is that the BioHazOp considers both engineering and biotechnological aspects (and their interactions). This interaction is not studied in the usual HAZOP analysis, which is focused on conventional chemical hazards identification. Therefore, the modification is represented by the specific columns (they are indicated as biocauses and bioconsequences) insertion in Table 1 and in Table A2 reported in Appendix A. In particular, BioHazOp is a tool, which is able to take into account the biotechnological process aspects, highlighting causes and outcomes related to the microbial consortia and their behaviour. This approach can generate a significant improvement of biotechnological processes safety and operability, because the usual HAZOP analysis does not investigate the possible interactions between engineering and biotechnological aspects.

Author Response File: Author Response.pdf

Reviewer 3 Report

This is my second review of this article. The Authors answered all of my comments. Suggested corrections have been applied. I suggest to accept this article in its present form.

Author Response

Dear Reviewer, Thank you for your comments. Best regards