Recent Advances in Membrane-Based Biogas and Biohydrogen Upgrading

Round 1

Reviewer 1 Report

Herein,

The authors review recent advances in membrane-based biogas separation. The author encompasses a wide range of techniques and is suitable for publication in Processes.

 

I recommend the following:

1. Remove or condense Sections 2.1 through 2.3; these techniques are outside of the scope of membrane separation; Authors can rework Section 2.4 to include why membrane separation is a preference over the above techniques.

 

2. Place '4. Challenges...' section last and discuss specifically some of the challenges mentioned in the different membrane separation techniques.

Author Response

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Reviewer 2 Report

Dear Authors

Congratulations on making an excellent manuscript. I have no significant substantive comments - However, I suggest that the Figures 1 and 2 with too small a font should be corrected.

Author Response

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Reviewer 3 Report

This review is written a bit like a textbook chapter. Emphasis is placed on the description of general principles, while ignoring the basic purpose of the review is to illustrate recent scientific progress in related fields.  In my opinion, these general descriptions should be greatly simplified while enhancing the illustration of recent articles. For example, Part 5.1.3, each material such as zeolites, COF or MOF, the representative results shall be figured out, and the progress shall be summarized in detail. In this way, each paragraph will be extended into several pages to fulfill the general style of the current reviews.

Author Response

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Reviewer 4 Report

Review of paper ‘Recent advances in membrane-based biogas and biohydrogen upgrading’ prepared by Cenit Soto, Laura Palacio, Raúl Muñoz, Pedro Prádanos and Antonio Hernandez.

 Manuscript processes-1915048 is focused on the presentation of the state-of-the-art membrane techniques used in biogas and H2 production. I have some suggestions that authors may consider before publishing this work:

1. The authors have identified other methods for biogas and biohydrogen purification technologies: it is worth pointing out the advantages and disadvantages of these solutions and thus showing why, as shown in Figure 1, membrane techniques have gained the most ground in recent years. At the same time, it is a pity that there is no data for recent years - the graph is exaggerated and only relates to the period up to 2019. New data should be provided, especially since more reports are now available. There is already a 2022 report - review work should give you the latest data (see https://bioenergyeurope.org/29-statistical-reports/370-biogas-2022.html.

2. Figure 2 needs to be corrected. To be changed: font size too small, lettering blurred. Also in Figures 3 and 12 the letterings are blurred and needs to be corrected.

3. In Equation 2: standard cubic centimetre, usually presented in subscript.

4. From a membrane application point of view, the most important parameters are permeability and selectivity. In my opinion, the authors should clearly indicate these parameters for the membranes in question while pointing out the most important research directions in these issues.

5. As this is a review paper, it would be useful to point out the technical and economic evaluation of the membrane used in biogas and biohydrogen processes/

6. As indicated in Figure 2, when considering membranes for gas separation, one criterion is the construction of the membrane (configuration flat, HF, etc.). The authors should discuss how this structure will affect the separation processes discussed. Another important aspect that has not been discussed in detail is the service life of the membranes. This is a very important aspect for industrial applications.

Author Response

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Round 2

Reviewer 3 Report

The authors have added considerable part  and enriched the content, while was reluctant to reduce some to make it a little shorter and a little easier to  finish reading.  anyway, so be it.  

Reviewer 4 Report

The  authors revised the manuscript as recommended. I have no further comments.