A Novel Batched Four-Stage–Two-Phase Anaerobic Digestion System to Facilitate Methane Production from Rice Straw and Cow Manure with Low Inoculum/Substrate Ratios
Round 1
Reviewer 1 Report
Dear Editor of Fermentation,
Here encloses my review on Manuscript ID: fermentation-2418154
The paper “A novel batched 4-stage-2-phase anaerobic digestion system to 2 facilitate methane production from rice straw and cow manure 3 with low inoculum/substrate ratio” it would seem that the article aims to study double-stage anaerobic fermentation: i.e., the separation between the acidogenic and methanogenic phases. But it is not clear what the purposes of the study are. Abstract is in practice, incomprehensible.
Since the prerequisite of two-stage anaerobic fermentation is the separation of the microbiome, obtained essentially by biokinetic separation: residence times in a first reactor to wash-out the methanogenic populations which have growth times far longer than the acidogenic ones, having conducted experiments in batch systems, it is not able to understand how the separation of the anaerobic microbiome has been achieved.
In addition, the experimental part is poorly described, and the results (see all the figures) do not report any uncertainty. In addition, there is a big confusion between the Buswell formula and the Gompertz expression, in which the variables are confused (be careful that P and BMPo are the same thing!! of which the latter is evaluated theoretically while the former is estimated experimentally). A mass balance is completely missing to evaluate the consistency of the experimental measurements, which I repeat have nothing to do with the double stage.
Recommended Literature:
The work adds nothing new to the field; and the English in many parts is difficult to follow.
For all these reasons, I recommend do not publish the paper in Fermentation to maintain the high scientific value of the journal.
The English in many parts is difficult to follow.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript fermentation-2418154 "A novel batched 4-stage-2-phase anaerobic digestion system to facilitate methane production from rice straw and cow manure with low inoculum/substrate ratio" presents interesting results about bioenergy production. The paper presents relevant information. It is well designed and easy to follow. The applied methodology is adequate and the literature cited is highly actualized. It deserves publication in Fermentation after Minor Revisions. The authors must consider the following comments:
- “Two phase” is not a keywords. Provide more innovative keywords.
- The end of the abstract should describe a brief conclusion of the result and importance of the article.
- Equations need to be in font in the manuscript. Review all.
- English needs to be improved throughout the manuscript. Avoid using long sentences.
- English needs to be improved throughout the manuscript. Avoid using long sentences.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript "A novel batched 4-stage-2-phase anaerobic digestion system to facilitate methane production from rice straw and cow manure with low inoculum/substrate ratio" presents the results of an experiment achieving improve biomethane production from rice straw and cow manure co-digestion. Even if the topic is of clear interest for the readers of Fermentation, I have to suggest rejection mainly due to the English language that makes the comprehnsion of the manuscript really hard. There are incomplete sentences missing the verbs, as well as really complex sentences with changes of tenses. Also typos are present throughout the manuscript.
Another issue that I detected is the number of replication of the experiment reported in Section 2.2. I doubt that is acceptable a duplication of an experiment, since three replications are often defined as the minimum to get a dataset to be statistically elaborated.
I suggest the authors to make a complete English editing of the manuscript through a mother-tounge speaker and then reconsider submitting the manuscript. Also statistic significance of the experiments should be better evaluated.
Please, see comments and suggestion for Authors.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
It is still not clear what the article is trying to prove. Assuming that the starting hypotheses are correct, there is no trace in the article of the measurement of the quantity of hydrogen produced, only the methane is measured. On the other hand, if co-digestion of substrates is to be shown to be an advantage, this is nothing new: thousands, if not millions of anaerobic digesters, working with mixed substrates is a standardized everyday practice. The question on the table today for the development of the AD is: how advantageous is of switching from single stage to two stages? Does the increase in energy produced in the form of hytane (H2+CH4) compensate for the investments in the first stage? How much does the permanence time in the second stage decrease compared to the single stage, with a decrease in volumes and therefore investment and management costs? Not to mention the saving in materials which increases the energy sustainability of the system.
On all these questions the manuscript adds nothing.
Therefore, I confirm my previous opinion.
Minor corrections, in some parts the meaning of the reported expressions is not clear.
Reviewer 3 Report
The authors have improved the manuscript following the main suggestion given after the first revision round (English editing, statistics). I feel that the manuscript can be accepted in the revised version.
English Language is fine.
