Advances and Perspectives in Biohydrogen Production from Palm Oil Mill Effluent
, Walter Jose Martinez-Burgos *, Gabriela De Bona Sartor, Luiz Alberto Junior Letti, Júlio Cesar De Carvalho, Carlos Ricardo Soccol and Adriane Bianchi Pedroni Medeiros *Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn the Introduction section: please update the information,Referencing 20182 It is relatively old reference for oil palm production;
Line 48-52, Please consider rewriting it by separating it into different sentences. The current structure is a long sentence without a break, which makes it difficult to read.
I would rather see a comprehensive table showing different pretreatments, which material was used, and how much yield of biogas or biohydrogen was achieved. This will help the readers to have an overview of the literature review process.
Please note that the h2 yield in the table should follow the same conversion measures. Make it consistent either report as H2/mol or H2/gCOD.
Information in the hydrogen part is very limited. The authors have mainly fitted with a basic treatment technology description with limited research examples. I advise compiling different treatment technologies to produce Hydrogen and discussing the benefits and drawbacks of the system.
Section 6, where the authors introduced strategies to enhance biohydrogen production, was useful. Please note all the values shown follow the same pattern.
In the economic section, please exchange all the values to the USD and follow the same in the entire text.
The conclusion authors stated, “However, the production of hydrogen from POME still faces numerous challenges for its large-scale production, requiring the adjustment of several parameters to obtain higher yields.” . I cannot see these elements where discussed in the text. Please elaborate.
Comments on the Quality of English LanguageOverall, the manuscript is very well written. Minor re-structuring is required.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsAuthors analysed Advances and Perspectives in Biohydrogen Production from POME. There are some parts, which must be revised:
1. Abstract is lacking main finding, it is not well organised.
2. L38; L66, L117, L162 and etc. has different abbreviations for POME. Make concise through the all text.
3. L50 has different units form than e.g. L81 and etc. Use consistent system (m/kg or m*kg-1).
4. L81, L303, L314 and others, use SI system units: kWh, L, h and etc. Make uniform through all text.
5. L104. What do you mean by "(table 2,3 and 4)" - are these table in this review, or copied from other text, because these table are not close to the mentioned place and are not related to the meaning.
6. Fig. 1 depicts "POME pretreatment methods" - what are these methods used for? You must clarify why this Fig is here.
7. L155 there are some unclear expressions.
8. L211-L225 are not relevant to H2 production and the topic of the paper.
9. Table 2 has references to process parameters and H2 yield. But there are no H2 yields from [49] and [11] reference, thus these references are not relevant to idea for H2 production.
10. L286. "5 alkaline pretreatments on POME, being alkaline 286 (10% NaOH), acidic (10% H2SO4), heat (80°C for 1h), and a combination of alkaline and 287 heat, and acid and heat. " - read one more time and prove, that H2SO4 or heat is alkaline pretreatment.
11. L339-L344 are not relevant to H2 production and the topic of the paper.
12. Table 3 has various measuring units for H2 yield. In the review article the units must be uniform to have the imagination and comparison about differences found in literature. How can be compared 1.87 mol H2/mol with 1.5 L H2 /L- POME ? What is "mol de H2/mol" - some unclear expression.
13. After chapter there are not concluding and summarizing findings. After reading these chapters it is not clear if H2 production is doable, under which conditions, what is the range of H2 generation and etc. Add sumaries after each chapter (No 2, 3, 4, 5, 6 and 7).
14. Table 4 has no H2 yields at reference [12]. So this reference is not relevant to this table.
15. Use consistent units L403 and L423.
16. Text formatting, spaces between words are unacceptable and weird through all text.
17. Conclusions are too general and too short. Conclusions do not reflect all findings of review. It must contain some numerical expressions.
18. In general manuscript does not contain deeper analysis of the topic, authors do not give generalized overview/conclusions about findings.
Comments on the Quality of English Language
English must be improved.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsPaper is now better organised.
Comments on the Quality of English LanguageMinor english correction is required.
