Methane Biofiltration Processes: A Summary of Biotic and Abiotic Factors

Round 1

Reviewer 1 Report (Previous Reviewer 1)

The addition of bibliometric analysis is good, but it is still not there as a clearly written element of the manuscript. It already shows how it can strengthen the storyline of the paper, but more materials must be added to clearly show what happened. Suggestion 1: Add a figure, say the new Figure 1, that schematically shows the workflow of the bibliometric analysis leading to the narrowed set of references used for inclusion in the discussion and data references of the paper. Show in this figure how the various selection criteria grouped and split various references. Such graphical presentation of the references analysis will significantly complement the textual explanation added in the methodology for the bibliometric analysis. Such figure would enhance the section 2. Methodology.

Another element of the paper relating to bibliometric analysis is missing. This is the summary of bibliometric analysis that will answer the objective “This review summarizes recent information on methane biofiltration processes”. The current materials in the paper cover by-topic results of the review. They do not cover the aspect of “recent information”. To accomplish this, there should be a show of how topics of the field has evolved in the time-period of the review. This can be presented as another figure. Such tool is now available in some online databases such as Web of Sciences. But you can also perform such time-series analysis of topics using the R Software-based module “Bibliometrix”, which has been suggested since the Round 1 of reviews.

Need for significant language improvement. The writing style is not technical in some portions of the manuscript. Please maintain technical rigor by favoring simple words over flowery words. For example, instead of “amalgamating”, why not simply say “integrating”, etc.? Or instead of “Grasping the processes of methanogenesis”, why not simply say “Understanding…” There are other examples like this all throughout the manuscript. Such “flavors” of statements just get in the way of delivering the meaning. Use direct words and simple sentences.

The in-text citation numbering is incorrect. Why is the first citation for reference #4, i.e., [4], when references [1], [2], and [3] have not been cited yet? Please use a bibliographic citation software such as the free Mendeley software (or the by-subscription EndNote software) to correctly format citations.

Given that the review paper is very long, a Conclusions section is imperative to summarize the findings of the review.

Moderate English language improvement needed.

Author Response

Dear reviewers, attached you can find our comments to your remarks, which have helped us to improve the paper, thanks for your diligent studying of our manuscript! Best regards, Maximilian Lackner

Author Response File: Author Response.pdf

Reviewer 2 Report (Previous Reviewer 2)

Dear Authors,

thank you for the implemtation and upgrade of the quality manuscript.

Best regards

Author Response

Dear reviewers, attached you can find our comments to your remarks, which have helped us to improve the paper, thanks for your diligent studying of our manuscript! Best regards, Maximilian Lackner

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report (Previous Reviewer 1)

The inclusion of results of bibliometric analysis as shown in Figure 1 and 2 is a significant improvement in the flow of the paper. However, additional information on how specifically these were done, specially Figure 1 results, must be provided so this figure material is not a mystery. Mentioning “The keywords and topics that are trending in each specific review section were identified using Bibliometrix” in lines 73-74 is not enough. This is usually addressed by providing as supplemental materials the following: (1) a copy (perhaps as CSV file or TEXT file) of the dataset used as input to Bibliometrix, and (2) the R-code used to run the data analytics and produce the graph in Figure 1. Also, please include proper citation of Bibliometrix (reviewer has nothing to do with this R package, so this suggestion is not for citation number purposes) to give credit to the creators of the tool. When these are done, then the paper is in good shape.

Minor revision/addition for clarity.

Author Response

Dear reviewer, thank you for your valuable comments, which we have all addressed.

Best regards, Maximilian Lackner

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report (Previous Reviewer 1)

Manuscript: methane-2740784-peer-review-v4

Title: Methane Biofiltration Processes: Methanotrophs and Abiotic Factors - A Comprehensive Review

Review:

The paper is almost complete now. To facilitate the sharing of the bibliometrics data and R-code to the readers of the paper, this paper must include a Data Availability statement that states and shows how to access the input bibliography data and the R-code associated with the Bibliometrix analysis. This can be done using a GitHub repo (https://github.com/) or by having the journal provide an online link to these supplementary materials. 

Minor editing of English language required

Author Response

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Manuscript Number: methane-2684537-peer-review-v1

Title: Methane Biofiltration Processes: Methanotrophs and Abiotic Factors- A Comprehensive Review

Evaluation:

-        -The aim of the paper is important in the current research area, but the conduct of review of literature is not clear, and the presentation of review findings is not clear.

-        -As a review paper, this paper must clearly describe how the various literature materials were selected from the thousands of papers out there in the subject area. For example, a quick search with the keyword ‘biofiltration’ in PubMed (by NIH) already results to 1,143 results as of the date of reviewing this paper. Add the literature pool of Web of Science and Scopus and the list with keyword ‘biofiltration’ will result to even more literature materials relevant to the topic. Then, what happens when that list of initially selected papers get to be grouped by the keyword ‘methane’, and so on. This approach should clearly show how the papers were narrowed down. This approach will also demonstrate the meaning of ‘comprehensive’ review, and perhaps will show trends in the topic through years, and decades of research and development in the area. So, please describe how the papers in the current version of this review paper were selected. Using such guided database-search approach in doing review of literature is now the standard approach in selecting literature materials to be used for deeper analysis in review papers.

-        -Also look into the use of a very helpful tool on bibliometric analysis called ‘Bibliometrix’, which is an R-software-based package for comprehensive bibliometric analysis.

-        -Please include graphical presentation of key trends, relations, etc. that are discussed in word-form in the paper. Review papers typically suffer from the lack of visual aids to help the reader see the findings of the review paper. The existing figures/graphs in the current version of the paper depict only small portions of the ideas being discussed, and they do not help understand the main findings of the review paper. Please create more integrated and more comprehensive visual aids/schematics/graphs, etc. Sometimes, there are graphical outputs from the use of PubMed, Web of Science, Scopus, etc.-based search of literature that can be integrated in a review paper as figure(s). Also make schematic on how the selection of papers was conducted as suggested in bullet-point 2.

-        -Also, please follow the instructions in preparing the manuscript for this journal.

Please improve the writing.

Reviewer 2 Report

Introduction

Dear Authors, thank you for deep review on methanotrophs used in the context of CH4 emission mitigations. The article provides valuable insight on the diversity of biologic studies employing methanotrophs in the context and is very focused on the microbiological description of the system employed. The review will allow reader to easily collect information on the subject and get a good overview.

Major comments

It was denoted that from line 126 to 141 and from 142 to 155 is basically the same section with some minor variation but no added information aside of references. Could be appropriate to merge the two section in a single one.

When it comes to pressure drop of biofilters, what is meant to be “not significant” in the paper? Looking at the diversity of tabulated mediums for biofiltering CH4 it would be good to have some overview of the average and/or theoretical reasoning on pressure drop. In fact, even if little already 50-100 mbar is significant from a process point of view in emission control.

180-181: I went through reference ---- 10. El Mashad, H. M., Barzee, T. J., Franco, R. B., Zhang, R., Kaffka, S., Mitloehner, F. (2023).Anaerobic Digestion and Alternative Manure Management Technologies for Methane Emissions Mitigation on Californian Dairies. Atmosphere, 14(1), 120 ---- I couldn´t find any information on the archaeon/bacterium co-culture from unknown species that was isolated. Can this be a referencing issue or could you explain?

Minor comments:

35-36 with 55% of anthropogenic emissions leading to CH4 gas concentrations below 3% v/v [51, 62] à Clarify the sentence, eventually, in the following way or i.e. did you mean: “with 55% of anthropogenic emission containing less than 3 Vol.% (v/v) methane (CH4)”.

121-122: revise formulation: Methanotrophs, which are able to convert methane, belong to a ….

125: have since greatly à Have since then greatly facilitated.

204-205: correct the sentence: “rather than just adsorb it are still not widely supported by research”

Reviewer 3 Report

This manuscript aims to summarize recent information on the various methanotrophic bacterial species (both methanotrophic and non-methanotrophic bacteria and fungi) and key factors such as salinity and temperature that affect CH4 biofiltration in methane biofiltration processes for reducing methane emissions, which contribute significantly to global warming.

Unfortunately, this manuscript does not meet the authors' intended objectives. As a result, it is difficult for readers to gain a broad understanding of the information on bacterial methane biofiltration. Therefore, we do not recommend that this review be published.

Section 3.3 is supposed to be a section on methane removal by fungi involved in methane biofiltration. However, the second half of the section changes to a discussion of fungi involved in methanogenesis. It is not possible to ascertain from the description in this review how this section is related to methane removal or methane oxidation.

A large amount of information is summarized in Table 2. However, there are no explanatory statements in the text regarding this information. Also, there is no explanation of the abbreviations used in the table, making it difficult for non-specialists to understand what is being summarized.

Section 4 also mixes methane oxidation and methanogenesis. The back half of the article is rather about methanogenesis, which has nothing to do with the purpose of this review. In addition, there is a paragraph in which the same content is repeated. This may be a copy-and-paste error.

Table 3 summarizes the effects of various improvement methods on GHG emissions from salt-impacted soils, but there is no specific explanation of this in the text, and it ends up being just a list of information.

There are also quite a few errors in the presentation of the paper, including the organization of chapters and sections and the inclusion of cited papers.

The appropriateness of the cited papers is also poor. Much of the content described in the introduction is the content summarized in the AR6 of the IPCC6. However, there are no citations to AR6, and instead various papers, doctoral thesis, and reviews are cited. These papers and the like are secondary or tertiary information and are not appropriate as citations.

As described above, unfortunately, this paper is not a comprehensive review and has many inadequacies. It needs to be completely and extensively rewritten.