Bridging the Gap between Biowaste and Biomethane Production: A Systematic Review Meta-Analysis Methodological Approach

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors wrote about a very topical topic in their article. Biogas production from organic materials will be important for several reasons in the coming years.

Overall, it meets the scientific requirements for articles. From a professional point of view, the work well summarizes knowledge about the topic being processed. The method of processing is appropriate. The analysis carried out is forward-looking.

Figure 2 shows the main sources of organic matter. It would be more interesting and illustrative to visualize the main categories of waste quantified.  It would also be nice to see the composition of substances from different sources from a chemical point of view. What literature data was found for this? This section should be explained in more detail.

I would suggest making comparisons in other areas, perhaps also in other countries in Europe.

In other European countries, what proportion of biogas is used to generate electricity?

Author Response

Comments 1: 
The authors wrote about a very topical topic in their article. Biogas production from organic materials will be important for several reasons in the coming years.
Overall, it meets the scientific requirements for articles. From a professional point of view, the work well summarizes knowledge about the topic being processed. The method of processing is appropriate. The analysis carried out is forward-looking.

Response 1: Thank you very much for your time reviewing this article.

 

Comments 2:
Figure 2 shows the main sources of organic matter. It would be more interesting and illustrative to visualize the main categories of waste quantified.  It would also be nice to see the composition of substances from different sources from a chemical point of view. What literature data was found for this? This section should be explained in more detail.

Response 2:
Thank you very much for the suggestions for improving section 2.1. We added more information about the quantified values of the main waste categories in EU and globally (Lines 99-107, 113-114, 116-119), while also presenting a new table (Table 1), with the composition of substances of each waste, regarding carbohydrate, protein, lipid and lignin content.

 

Comments 3:
I would suggest making comparisons in other areas, perhaps also in other countries in Europe.
In other European countries, what proportion of biogas is used to generate electricity?

Response 3:
Thank you very much for the comment. We added data of the EU27 regarding the percentages of biogas utilization (Lines 295-298).

Reviewer 2 Report

Comments and Suggestions for Authors

This study presents a systematic review meta analysis methodology for biomethane estimation, using over 600 values of volatile solids content and biochemical methane potential of 6 different waste streams, collected from 240 scientific studies. The research content has certain practical significance, but there are still the following problems:

 

1. The format of the paper requires further verification and correction, with a particular emphasis on checking paragraph indentation as well as the captions for figures and tables.

2. Please clarify if the statement “which in many cases has shown to notably improve the total methane production” in section 2.1 is supported by relevant proof materials.

3. In 3.2, the frequent use of various nouns and their corresponding abbreviations makes the writing redundant, which may lead to logical confusion for readers when reading this article. It is suggested that the “keywords used for search”, “corresponding notations”, and “the useful data values” in this section be organized into a table for an intuitive presentation, while the text should focus more on describing the operational procedures and research methods.

4. Please standardize the drawing of Figures 7 and 8 and present the images and tables clearly and separately.

5. The conclusion section is overly redundant. Please streamline this section.

Comments on the Quality of English Language

Moderate editing of English language required

Author Response

 Comments 1:
The format of the paper requires further verification and correction, with a particular emphasis on checking paragraph indentation as well as the captions for figures and tables.

Response 1:
Thank you very much for the comment. We further corrected many parts of the manuscript that needed proper indentation.

 

Comments 2:
Please clarify if the statement “which in many cases has shown to notably improve the total methane production” in section 2.1 is supported by relevant proof materials.

Response 2:
It is now clarified that the statement is supported by reference material.

 

Comments 3:
3.    In 3.2, the frequent use of various nouns and their corresponding abbreviations makes the writing redundant, which may lead to logical confusion for readers when reading this article. It is suggested that the “keywords used for search”, “corresponding notations”, and “the useful data values” in this section be organized into a table for an intuitive presentation, while the text should focus more on describing the operational procedures and research methods.

Response 3:
Thank you very much for the comments. The keywords, the corresponding notations and the data values collected (sample) are now presented into Table 2.

 

Comments 4:
Please standardize the drawing of Figures 7 and 8 and present the images and tables clearly and separately.

Response 4:
Figure 7 is now separated into Table 4 and Figure 7, and Figure 8 is separated into Table 5 and Figure 8.

 

 

Comments 5:
The conclusion section is overly redundant. Please streamline this section.

Response 5:
Thank you for the comment. We streamlined the conclusions section as you noted, keeping only the important parts.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

 Accept

Comments on the Quality of English Language

Minor editing of English language required