Review Reports

Round 1

Reviewer 1 Report

1. Layer inoculation instead of premixing inoculation was used to treat solid-state anaerobic digestion of maize straw (MS) and pig manure (PM). This study found that layer inoculation was effective to enhance methane production under high volatile fatty acid (VFA) concentrations. The English writing of this manuscript is satisfactory. The methods used in this study and the derived experimental results can provide helpful references for academicians in relevant fields. A few modifications should be made prior to its further being considered possible publication.

2.  There are a few mathematical symbols and abbreviations in this manuscript. Hence, a list of nomenclature is suggested to be added in the revised manuscript in order to quickly understand the meaning of the article.

3. An illustrating diagram to present the schematic set-up of the experiment is suggested so that the possible audience can understand how the investigation is carried out.

4. Please check the correctness of: “10276xg” in line 128, and “10-20 ng” in line 154; subscript “4” in lines 172 and 241; repeat “20” in line 226; please remove repeated “reaction” at line 152; etc.

5.  Whole words should be provided once their corresponding abbreviations first appear, for example, PCo2 in line 397.

6. More detailed discussion of the results is encouraged, particularly on page 7 for Figs. 3 and 4.

7. In the section Conclusions, more results from this study should be summarized in this section. The current content seems too concise. In addition, abbreviations such as SS-AD and VFA are generally not used in this section.

8.      The reference format on page 12 should be consistent and follow the format regulation of the journal, for example, references 1, 2, 4, and 6.

1. English writing of this manuscript is considered satisfactory.

Author Response

Dear editor and reviewers:

Thank you very much for reviewing our manuscript "Layer inoculation as a new technology to resist volatile fatty acid inhibition during solid-state anaerobic digestion: Methane yield performance and microbial responses" and giving us very valuable comments. During the past days, we have considered these comments carefully, and all corresponding modifications are marked in “Track Changes” function of the revised manscript.

Once again, many thanks for considering possible publication of our manuscript.

Reviewer 2 Report

Layer inoculation as a new technology to resist volatile fatty acid inhibition during solid-state anaerobic digestion: Methane yield performance and microbial responses

Xingliang Gao , Zhuowu Li, Keqiang Zhang, Dewang Kong, Wenxuan Gao, Junfeng Liang , Fuyuan Liu, and Lianzhu Du

The research is innovative and covers many aspects of modern agriculture and industrial biotechnology. Anaerobic digestion is an appropriate method for converting biomass resources into biogas that is rich in methane. The present research analyzed a new inoculation method named layer inoculation, and compared to premixing inoculation in solid-state anaerobic digestion of pig manure and maize straw. The results showed that the cumulative CH₄ yields from layer inoculation (211.5 ml/g-VS) were 5.64 times those from premixing inoculation (37.5 ml/g-VS) under low inoculation ratio (25%), with the values of total volatile fatty acid being greater than 30.0 mg/g. The inoculum has an important influence on the methanogenic community. Methanosphaerula and Methanothrix were the most dominant genera.

Some comments and suggestions for the authors:

1)     It should be correct CH₄ in 172 paragraph.

 2)     It should be correct CH₄ in 231, 241 paragraphs.

 3)     It should be correct in Figure 1 in 173, 285, 295, 315 paragraphs.

 4)     It should be correct (Figure S1) in 264 paragraph.

  5)     It should be correct (Figure S2) in 305 paragraph.

  6)     It should be correct in Figure 4 in 271 paragraph.

  7)     It should be correct are shown in Figure 5 in 324 paragraph.

            8)     This was also supported by the digestion performance (Figure1 and Figure 2) and the methanogenic community (Figure 5) in 390, 391 paragraphs.

               9)     I think too many abbreviations in the manuscript.

              10) Could you please to explain the abbreviations in the Table 1.

            11) Could you please explain in the table 2 the abbreviations and meanings of the letters „P, M, L“ ?

               12) Could you please to explain the abbreviations in the Figure 1?

                13) Could you please to explain the abbreviations in the Figure 2?

 

 

Comments for author File: Comments.pdf

Author Response

Dear editor and reviewers:

Thank you very much for reviewing our manuscript "Layer inoculation as a new technology to resist volatile fatty acid inhibition during solid-state anaerobic digestion: Methane yield performance and microbial responses" and giving us very valuable comments. During the past days, we have considered these comments carefully, and all corresponding modifications are marked in “Track Changes” function of the revised manscript.

Once again, many thanks for considering possible publication of our manuscript