Changes of C, H, and N Elements of Corn Straw during the Microwave Heating Process

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Peer Review Report

1. Original submission

1.1. Recommendation

Major revision

2. Comments to Authors

Manuscript ID: carbon-2668113

Title: C, H, and N elements of corn straw during the microwave heating process

Authors: Zhihong Liu, Weitao Cao, Man Zhang , Wenke Zhao, Yaning Zhang

Overview

The article deals with C, H and N migration in corn straw during microwave heating. The survey includes the effects of residence time, heating temperature and microwave power on the process. As a result, the only conclusion announced is:" The proportion of C element rose with extended residence time, whereas the proportion of H element decreased as residence time increases".

2.1. Major comments

1. My first remark stems from the following fact:

Hypothesis: Energy from biomass, as a renewable energy source, is very important for advancing low-carbon energy development, resource sustainability and an alternative to fossil fuels.

A thesis is missing: What is the relation between the migration of C; H and N in biomass with the energy yield? What is the conclusion from the established dependencies between residence time, heating temperature, microwave power and migration? How will microwave treatment of biomass increase the energy efficiency of its processing? An example of such an approach is the overview presented in section Introduction, pages 2 and 3; lines 61-106.

2. Page 3, line 112: What is the criterion for the high importance of the efficient use of biomass in the reported case: High yield of volatile matters? High yield of charcoal? Use of the heat energy from the process? Or something else?

3. As the main drawback of the research, I will point out the lack of data showing the relationship between the composition of the biomass, the mechanisms of destruction of the lignocellulosic matrix and the conditions of its thermal treatment (temperature, time and radiation power). Undoubtedly, the mechanism of degradation of hemicellulose, cellulose and lignin is directly related to the so-called migration of C, N and H, i.e. with their ratio in time as well as under different temperatures. Do you have any data on what processes take place in the microwave-assisted heating of biomass? What is the mechanism and sequence of destruction of the three main components - cellulose, lignin and hemicellulose? What is the role of biomass ash content under microwave treatment conditions?

2.2. Minor comments

1.  The meanings of the abbreviations M_ar; V_ar; C_ar and A_ar (Table 1) are not previously defined in the text.

Author Response

Thank you for your letter and comments and suggestions for our manuscript. These comments are valuable and helpful for improving our manuscript, and they are also of important guiding significance to our future research. We have read the comments carefully and made revisions accordingly. The revised parts are marked in red in the Revised Manuscript with changes marked.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article is very well elaborated and it is encouraging that experiments were performed without adding microwave absorbent, which is, as author pointed out, of great significance for the efficient utilization of biomass. However, I would recommend to adjust the discussion in order to be more accessible to a wider group of researchers. Here are some of the comments how to improve.

For example, the material preparation section is written very poorly, I would recommend for the authors to extend the description of materials manipulation prior to MW experiments, details should be provided so that the results can be reproduced. This is clearly under the scope of the Journal and highly recommended.

Secondly, material characterization is missing, giving the essential information to the readers on what methods were used to perform a pristine materials characterization (elemental, structural, morphological, etc.) but also to establish the changes in elemental percentage composition as well wat was the residual components after the MW treatment at different temperatures.

Did the authors compared results obtained by MW with some other method for material pyrolysis?

Some discussion on the material transformation upon thermal treatment are missing, since the temperature such as 275 °C is low temperature to perform severe structural changes but only some modifications.

Authors mentioned the CO₂ release. How they came to this conclusion? Can you provide some additional information on the amount (%) of gas released?

 

What is the final potential application depending on the selected conditions? 

Author Response

Thank you for your letter and comments and suggestions for our manuscript. These comments are valuable and helpful for improving our manuscript, and they are also of important guiding significance to our future research. We have read the comments carefully and made revisions accordingly. The revised parts are marked in red in the Revised Manuscript with changes marked.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Overall comments

This paper lacks technical content as a paper, the experimental design is not comprehensive enough to make it a “paper”. I am sorry but I have to reject it.

 

Specific comments

1.      Title: “C, H, and N elements of corn straw during the microwave heating process” It is not very clear, I suggest change it into “Changes of C, H, and N elements of corn straw during the microwave heating process”

2.      “Leading 20 to an increased oxidation rate” How could you know that the oxidation rate was increasing?

 

3.      Sorry, I just had an overview at the paper, I do not think the technical content is sufficient to make a paper. Regardless of originality, the overall content reads like an experimental report. I have to reject it.

Author Response

Thank you for your letter and comments and suggestions for our manuscript. These comments are valuable and helpful for improving our manuscript, and they are also of important guiding significance to our future research. We have read the comments carefully and made revisions accordingly. The revised parts are marked in red in the Revised Manuscript with changes marked.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

This manuscript showed intriguing study

Comments on the Quality of English Language

no

Author Response

Thanks for your positive comments.

We also tried to improve the manuscript which was uploaded as the revised manuscript.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Just to let you know, what you explain in Response#1 is not a conclusion. The presence of numerical data in the Conclusions section turns it into a Results and Discussion section. The conclusion is: What do the obtained results exhibit, what follows from the observed dependencies, i.e. what is the cause and effect relationship and how would it improve what is known so far on the matter?  Possibility to further develop the topic (optional).

 

The rest of the responses are convincing. I recommend that the article be published after minor corrections in the Conclusions section.

 

 

 

 

 

 

Author Response

Reviewer #1:

Just to let you know, what you explain in Response#1 is not a conclusion. The presence of numerical data in the Conclusions section turns it into a Results and Discussion section. The conclusion is: What do the obtained results exhibit, what follows from the observed dependencies, i.e. what is the cause and effect relationship and how would it improve what is known so far on the matter? Possibility to further develop the topic (optional).

The rest of the responses are convincing. I recommend that the article be published after minor corrections in the Conclusions section.

Response:

Thanks for your comments and suggestions. We have made corrections in the Conclusions section. The details are as follows.

	Line	Content
Original	272-288	At temperatures below 275 °C, N elements of corn straw particles didn't migrate much. As the temperature increased, the proportion of C element went up, while the pro-portion of H element steadily decreased. At 225 °C, the proportion of C element decreased due to an oxidation reaction. The time the corn straw particles spent in the reaction chamber (residence time) was critical for the migration C, H, and N elements. With longer residence times, the proportion of C element increased from 31.77% to 35.36%, while the proportion of H element de-creased from 4.50% to 3.83%. A significant change in the proportion of C element occurred around the 30-minute mark, indicating a notable oxidation process. Microwave power plays a role in both the heating rate of the sample and the maxi-mum temperature it can reach, which affects the migration of C, H, and N elements. At 160 W, the proportion of C element increased initially and then decreased as residence time grew, with the turning point occurring at 30 min. The proportion of H element de-creased as residence time increased. When the microwave power was 180 W and 200 W, the oxidation rate of C element was slower than the release rate of H-containing volatiles. Consequently, the proportion of C element increased with longer residence times, while the proportion of H element decreased.
Revised	272-289	At temperatures below 275 °C, N elements of corn straw particles didn't migrate much. As the temperature increased, the carbonization process of corn straw was more complete, and the proportion of C element increased gradually. At 225 °C, the proportion of C element decreased due to an oxidation reaction. The residence time was critical for the migration C, H, and N elements. The increase of residence time made the carbonization process of corn straw more complete, resulting in the increased of C element proportion from 31.77% to 35.36%. A significant de-creased in the proportion of C element occurred around the 30-minute mark, indicating a notable oxidation process. Microwave power played a role in both the heating rate of the sample and the maximum temperature it can reach, which affected the changes of C, H, and N elements. At 160 W, the proportion of C element increased initially and then decreased as residence time grew, with the turning point occurring at 30 min due to the oxidation of C element. The proportion of H element decreased as residence time increased due to the continuously released of H-containing volatiles. When the microwave power was 180 W and 200 W, the carbonization process of C element was more complete with the increased of residence time. Consequently, the proportion of C element increased, while the proportion of H element decreased.

 

Reviewer 2 Report

Comments and Suggestions for Authors

The authors kindly responded to all of the required comments and suggestions. Therefore, I recommend the paper be published in the corrected form provided by the authors.

Author Response

Thanks for your kind comments.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors did well in revision. However, by looking at the color of the sample, it is difficult to conclude anything about the oxidation rate. Maybe you can say “the carbonization process is more complete.”

Author Response

Reviewer #3:

The authors did well in revision. However, by looking at the color of the sample, it is difficult to conclude anything about the oxidation rate. Maybe you can say “the carbonization process is more complete”.

Response:

Thanks for your suggestion. Yes, the color of the sample can only reflect its carbonization process, but cannot indicate its oxidation rate. We have made changes in the manuscript, and the details are as follows.

	Line	Content
Original	19-22	When there was an increase in the microwave powers between 160 W and 200 W, higher temperatures were reached in the samples, leading to an increased oxidation rate of C element and a more rapid release rate of volatiles containing H element.
Revised	19-21	When there was an increase in the microwave powers between 160 W and 200 W, higher temperatures were reached in the samples, leading to the carbonization process of corn straw more complete.