Biochar Effectively Reduced N₂O Emissions During Heap Composting and NH₃ Emissions During Aerobic Composting

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 

General comments

1. The manuscript is poorly written in English. The authors use many words inappropriately or even incorrectly to emphasize their statements. It is recommended that a qualified professional translate the original text.
2. Right from the title, the manuscript presents a questionable aspect regarding the term "anoxic," which appears to have been misused, as it means "oxygen-lacking" or "oxygen-free."
3. The abstract presents the main results, but should also show the conclusions that can be drawn from them, highlighting their novelty and contribution to current knowledge.
4. Keywords cannot contain terms used in the title, but instead indexing terms commonly used in the field of study.
5. The introduction to the copy of the manuscript received by the reviewer contains several unacceptable errors. Furthermore, the hypothesis of the work must be well-established in the introduction.
6. The materials and methods section also contains error messages and lacks relevant information for replicating the experiment.
7. The results and discussion section is excessively long. It is recommended that the discussion be separated from the results and maintain the same presentation structure. Figure titles should be more informative about the study's topic. Some figures should have their clarity improved. Several sections of the discussion should be accompanied by supporting or disconfirming references.
8. The study's main findings should be presented clearly and directly in the conclusions. Furthermore, the novelty of these findings and their contribution to knowledge on the subject should be established.
9. The manuscript may be relevant to the field of study if the reviewers' suggestions are followed.
10. Some self-citations were observed.
11. The manuscript is scientifically sound, but it lacks a clear hypothesis, and some aspects of the methodology require clarification.
12. The manuscript's results could be reproduced if some aspects of the methodology were better described.
13. Some figures should be presented more clearly, and their titles should be more informative about the study's topic. In general, the data are interpreted appropriately and consistently in the manuscript.
14. Conclusions are not succinct and straightforward and should present the study's main findings, as well as its novelty and contribution to knowledge.
15. Data availability statements are adequate.

Specific comments

1. Line 2: The term "anoxic" is questionable.
2. Line 15: Replace the term "application."
3. Lines 18 and 19: It is unclear what type of difference is being determined.
4. Line 20: It is essential to indicate the crop from which the straw was obtained.
5. Line 25: The term "conversely" does not seem to correspond to the context of the statement.
6. Line 31: The keywords should be changed.
7. Line 37: The error message presented in several parts of the manuscript is unacceptable.
8. Line 64: The term "enterprises" should be changed.
9. Line 67: The term "favored" should be changed.
10. Line 71: "Yield superior emission reduction outcomes" should be expressed more clearly.
11. Line 77: The term "distinction" should be changed. l) Lines 79 to 81: The text should be rewritten to be more understandable.
12. Section 2.1: The study institution and its location should be better described.
13. Line 86: The term "procured" should be changed.
14. Line 87: The plant composition of the straw should be presented. The term "fundamental" should be reconsidered.
15. Table 1: The table title should be more informative.
16. Section 2.2: The "anoxic composting" process should be described in detail.
17. Lines 96 and 97: The materials to which the "3:1 ratio" refers should be better clarified.
18. Lines 101 to 103: The text implies that both processes were subjected to "periodic manual turning." If this is correct, the two processes should be described in a way that highlights the differences between them.
19. Line 109: What does "high-throughput sequencing analysis" refer to?
20. Lines 111 and 112: Equipment manufacturer information should be included, as in line 121.
21. Line 119: Was only N₂O considered a "greenhouse gas"?
22. Lines 129 and 130: "With the help of the Canoco 5 program" is a meaningless sentence.
23. Lines 147 to 151: Both sentences should be supported by a reference.
24. Lines 167 to 170: There should be a reference corroborating the discussion.
25. Lines 171 to 176: The pH ranges presented in parentheses are challenging to understand.
26. Lines 171 to 176: We cannot speak of "alkaline shift" or "acidification," since the entire pH range shown in Figure 1c is within the alkalinity range.
27. Line 181: The term "augmented" should be changed.
28. Line 186: The use of the terms "synergistic" and "synergistically" (line 303) should be very well supported.
29. Line 196: The use of "rebound" or "rebounded" should be reconsidered.
30. Line 223: The term "paired" should be changed.
31. Line 228: The phrase "A widely accepted criterion posits" should be replaced with a reference or description of the criterion.
32. Line 235: The term "expedite" should be replaced. hh) Line 251: Replace "ammonium-ammonia" with their molecular formulas.
33. Line 267: The term "spike" should be replaced.
34. Line 288: The Shannon and Chao1 indices should be described in the materials and methods section.
35. Lines 291 to 297: The context of the terms "species richness," "community diversity," and "microbial richness and diversity" should be carefully specified.
36. Line 312: Rewrite the sentence "these results were consistent with the established composting microbiota profiles."
37. Line 313: The term "heightened" should be replaced.
38. Figures 5 and 6: Increase the clarity of the figures.
39. Lines 348 and 349: The subtitles should be separated. pp) Lines 408 and 409: the “Data Availability Statement” is inadequate.

Comments on the Quality of English Language

Please see my comments in the attached document.

Author Response

Response to the Reviewer 1

 

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Biochar effectively reduced the emission of N₂O during anoxic composting and NH₃ during aerobic composting” (ID: agriculture-3832971). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. The responds to the reviewer’s comments, point by point, are as flowing:

 

Reviewer #1:

General comments

Q1. The manuscript is poorly written in English. The authors use many words inappropriately or even incorrectly to emphasize their statements. It is recommended that a qualified professional translate the original text.

R1: Thank you for your kind reminder. The manuscript has been edited by native English speaking editors at AJE (No. 95B5-E06B-AFC0-8AE9-F9C7).

Q2. Right from the title, the manuscript presents a questionable aspect regarding the term "anoxic," which appears to have been misused, as it means "oxygen-lacking" or "oxygen-free."

R2: Your point is critical. The term "anoxic" specifically means "oxygen-deficient" or "oxygen-free." In this study, "anoxic" specifically refers to the oxygen-limited process relying on natural ventilation (without forced aeration or mechanical turning), in contrast to "aerobic composting" which depends on human intervention.

Q3. The abstract presents the main results, but should also show the conclusions that can be drawn from them, highlighting their novelty and contribution to current knowledge.

R3. Thank you for your suggestion. Your feedback is highly relevant—the abstract should indeed explicitly highlight the study's conclusions, innovations, and its contribution to the field. We will revise the abstract by adding the following content: Adding 10% biochar during the initial stage of aerobic composting helps reduce ammonia volatilization, decrease nitrogen loss, and improve compost product quality. At the livestock farm level, mixing livestock manure with straw additives and incorporating 10% biochar for a 45-day composting process not only reduces greenhouse gas N₂O emissions but also enhances the sanitization level of the manure.

Q4. Keywords cannot contain terms used in the title, but instead indexing terms commonly used in the field of study.

R4: Thank you for your suggestions. We have revised the keywords as follows: agricultural waste; additive; waste treatment; greenhouse gas; microbial community.

Q5. The introduction to the copy of the manuscript received by the reviewer contains several unacceptable errors. Furthermore, the hypothesis of the work must be well-established in the introduction.

R5: Thank you for highlighting these critical issues. We have thoroughly reviewed and revised the introduction section of the manuscript, with particular emphasis on refining the theoretical framework and explicitly stating the core hypothesis of this study: Building on previous research demonstrating biochar's efficacy in reducing nitrogen loss during aerobic composting, we hypothesize that biochar can similarly mitigate nitrogen loss under anaerobic composting conditions, and we aim to compare its mechanistic differences across these two composting systems through controlled experiments.

Q6. The materials and methods section also contains error messages and lacks relevant information for replicating the experiment.

R6: Thank you for your suggestions. We have revised and refined this section accordingly.

Q7. The results and discussion section is excessively long. It is recommended that the discussion be separated from the results and maintain the same presentation structure. Figure titles should be more informative about the study's topic. Some figures should have their clarity improved. Several sections of the discussion should be accompanied by supporting or disconfirming references.

R7: Thank you for your suggestion. Considering the manuscript requirements and our writing conventions, we have decided to retain the placement of Results and Discussion together. We have revised and refined all figure captions and the Discussion section accordingly.

Q8. The study's main findings should be presented clearly and directly in the conclusions. Furthermore, the novelty of these findings and their contribution to knowledge on the subject should be established.

R8: Thank you for your suggestion. We have revised the conclusion as follows: This study demonstrated that biochar amendment enhances composting efficiency by prolonging the thermophilic phase and raising the pH, thereby improving organic matter stabilization and product safety. Specifically, biochar-added anoxic composting (BC1) reduced NH₃ and N₂O emissions by 27.8% and 49.5%, respectively, compared to conventional anoxic composting (C1). While aerobic composting with biochar (BC2) reduced cumulative NH₃ emissions by 56.6% relative to the control, BC1 outperformed BC2 by suppressing NH₃ emissions by 84.2%. These reductions were mechanistically attributed to biochar’s microbial modulation: it suppressed Bacteroidota (associated with ammonia volatilization) and enriched Chryseolinea (linked to nitrogen retention), restructuring microbial networks to mitigate gaseous losses. Moreover, adding 10% biochar during initial aerobic composting reduces ammonia volatilization and nitrogen loss while enhancing compost quality. At the farm level, a 45-day co-composting process of livestock manure with straw and 10% biochar not only lowers N₂O emissions but also improves sanitization.

Q9. The manuscript may be relevant to the field of study if the reviewers' suggestions are followed.

R9: Done.

Q10. Some self-citations were observed.

R10: Thank you for your suggestion. We have optimized the references and confirmed their relevance.

Q11. The manuscript is scientifically sound, but it lacks a clear hypothesis, and some aspects of the methodology require clarification.

R11: Thank you for your suggestion. We have supplemented the assumptions in the preface.

Q12. The manuscript's results could be reproduced if some aspects of the methodology were better described.

R12: Thank you for the reminder. We have supplemented and revised the Materials and Methods section to ensure the reproducibility of the manuscript results.

Q13. Some figures should be presented more clearly, and their titles should be more informative about the study's topic. In general, the data are interpreted appropriately and consistently in the manuscript.

R13: We have revised and refined all figure captions and the Discussion section accordingly.

Q14. Conclusions are not succinct and straightforward and should present the study's main findings, as well as its novelty and contribution to knowledge.

R14: Thank you for your suggestion. We have revised the conclusion.

Q15. Data availability statements are adequate.

R15: Thank you for your suggestion.  We have revised the conclusion

Specific comments

Q16. Line 2: The term "anoxic" is questionable.

R16: Thank you for your feedback. The term "anaerobic" conditions in this study specifically refers to environments with natural ventilation but no mechanical ventilation, rather than strictly "anoxic" (oxygen-free) states. The terminology has been revised to prevent ambiguity.

Q17. Line 15: Replace the term "application."

R17: Thank you for your suggestion. We have replaced the term "application" with "utilisation" in Line 15 to enhance terminological precision.

Q18. Lines 18 and 19: It is unclear what type of difference is being determined.

R18: Thank you for your comment. The "differences" mentioned in Lines 18-19 specifically refer to the variations between anaerobic and aerobic composting methods in terms of compost quality, emission reduction effectiveness, and microbial community composition. The description has been clarified accordingly.

Q19. Line 20: It is essential to indicate the crop from which the straw was obtained.

R19: Thank you for your feedback. We have revised the generic term "straw" to "corn straw" in Line 20 to precisely specify the source of the experimental material.

Q20. Line 25: The term "conversely" does not seem to correspond to the context of the statement.

R20: Thank you for identifying this issue. We have noted the improper use of "conversely" in Line 25 and have revised it to "nevertheless" to more accurately convey the transitional relationship within the context.

Q21. Line 31: The keywords should be changed.

R21: Thank you for this important suggestion. We have revised the keywords in Line 31 to: "cow dung; biochar; composting; nitrogen loss; microbial community" to more accurately reflect the core aspects of our research.

Q22. Line 37: The error message presented in several parts of the manuscript is unacceptable.

R22: Yes. We have made corrections to the erroneous information.

Q23. Line 64: The term "enterprises" should be changed.

R23: Thank you for pointing this out. We agree that the term "enterprises" was not precise in this context and have revised it to "facilities" to better align with technical terminology.

Q24. Line 67: The term "favored" should be changed.

R24: Thank you for your suggestion. We have noted that the term "favored" may carry subjective connotations in this context and have revised it to "widely used" to more objectively and accurately describe the current application status of this technology.

Q25. Line 71: "Yield superior emission reduction outcomes" should be expressed more clearly.

R25: Thank you for this valuable suggestion. We have revised the expression to "yield superior greenhouse gas emission reduction outcomes". By specifying "greenhouse gas", the specific scope of emission reduction effects is now more clearly defined.

Q26. Line 77: The term "distinction" should be changed. l) Lines 79 to 81: The text should be rewritten to be more understandable.

R26: Thank you for these important revision suggestions. We have implemented the following improvements: firstly, we have replaced "distinction" with the more commonly used term "differences" to enhance terminological precision. Additionally, we have restructured the text in lines 79-81 to clearly emphasize that "this study is anticipated to provide practical guidance for nitrogen retention in waste-to-fertilizer processes by incorporating biochar into anaerobic composting," making the logical relationship between the technical approach and application value more comprehensible.

Q27. Section 2.1: The study institution and its location should be better described.

R27: Thank you for your valuable feedback. We have supplemented detailed information about the research institution and environment in the original text, specifically stating: "The composting site was located in an experimental shed behind the Institute of Plant Protection and Soil Fertilizer of the Hubei Academy of Agricultural Sciences in Wuhan, Hubei Province, China, equipped with a rain-sheltered roof and well-ventilated systems." This addition enhances the environmental reproducibility elements of the study, making the spatiotemporal characteristics of the experimental setting more explicit.

Q28. Line 86: The term "procured" should be changed.

R28: Thank you for your suggestion regarding terminology optimization. We have adopted the recommendation and changed "procured" to "acquired" in the original text.

Q29. Line 87: The plant composition of the straw should be presented. The term "fundamental" should be reconsidered.

R29: Thank you for your valuable suggestions. We have supplemented the specific plant composition of the straw at Line 87 and replaced the term “fundamental” with “basic” to enhance the accuracy and rigor of the description.

Q30. Table 1: The table title should be more informative.

R30: Thank you for your suggestion. We have revised the table title to "Basic Physical and Chemical Properties of Composting Raw Materials: Cow Manure, Rapeseed Straw, and Biochar" to make the content clearer and more informative.

Q31. Section 2.2: The "anoxic composting" process should be described in detail.

R31: Thank you for your suggestions. We have refined the details in the Materials and Methods section.

Q32. Lines 96 and 97: The materials to which the "3:1 ratio" refers should be better clarified.

R32: Due to the high cost of auxiliary materials in actual production, it is difficult to achieve a carbon-to-nitrogen ratio exceeding 25 in the initial feedstock. To better align with real-world manufacturing conditions, this study directly mixed manure and auxiliary materials at a 3:1 ratio, maintaining consistency across all treatments while achieving the desired heating effect.

Q33. Lines 101 to 103: The text implies that both processes were subjected to "periodic manual turning." If this is correct, the two processes should be described in a way that highlights the differences between them.

R33: Thank you for highlighting this issue. We have revised the description in Lines 101 to 103 to clearly indicate that only the aerobic composting treatment involved periodic manual turning, thereby accurately distinguishing between the two processes.

Q34. Line 109: What does "high-throughput sequencing analysis" refer to?

R34: Thank you for pointing out this oversight. We have clarified in the manuscript that "high-throughput sequencing analysis" specifically refers to 16S rRNA gene-based high-throughput sequencing technology used for analyzing microbial community structure.

Q35. Lines 111 and 112: Equipment manufacturer information should be included, as in line 121.

R35: Yes. We have added the content (Elementar, Germany).

Q36. Line 119: Was only N₂O considered a "greenhouse gas"?

R36: Not. We have modified the “greenhouse gas” to “N₂O emissions”.

Q37. Lines 129 and 130: "With the help of the Canoco 5 program" is a meaningless sentence.

R37: We have deleted “With the help of the Canoco 5 program”.

Q38.Lines 147 to 151: Both sentences should be supported by a reference.

R38: We have added reference support. [18,19]

Q39. Lines 167 to 170: There should be a reference corroborating the discussion.

R39: We have added reference support. [27]

Q40. Lines 171 to 176: The pH ranges presented in parentheses are challenging to understand.

R40: Thank you for your valuable feedback. The range in parentheses represents the pH value range during the four different treatment periods of the experiment.

Q41. Lines 171 to 176: We cannot speak of "alkaline shift" or "acidification," since the entire pH range shown in Figure 1c is within the alkalinity range.

R41: Yes. We have added the content. The pH value increases in the first phase corresponded to ammonia (NH₃) volatilization during nitrogen mineralization. Subsequent pH decrease was driven by reduced NH₃ emissions and the accumulation of low-molecular-weight fatty acids (e.g., acetic, propionic) and CO₂ from organic matter decomposition.

Q42. Line 181: The term "augmented" should be changed.

R42: Yes. We have deleted “augmented”.

Q43. Line 186: The use of the terms "synergistic" and "synergistically" (line 303) should be very well supported.

R43: Yes. We have deleted "synergistic" and "synergistically".

Q44. Line 196: The use of "rebound" or "rebounded" should be reconsidered.

R44: Yes. We have modified the “rebounded” to “increased”.

Q45. Line 223: The term "paired" should be changed.

R45: Yes. We have modified the “paired” to “used alongside”.

Q46. Line 228: The phrase "A widely accepted criterion posits" should be replaced with a reference or description of the criterion.

R46: Done.

Q47. Line 235: The term "expedite" should be replaced. hh) Line 251: Replace "ammonium-ammonia" with their molecular formulas.

R47: Yes. We have modified the “expedite” to “accelerate the degradation of”. We have modified the “ammonium-ammonia” to “NH⁺₄‒NH₃”.

Q48. Line 267: The term "spike" should be replaced.

R48: Yes. We have modified the “spike” to “peak”.

Q49. Line 288: The Shannon and Chao1 indices should be described in the materials and methods section.

R49: Yes. we've added it to the Materials and Methods section.

Q50. Lines 291 to 297: The context of the terms "species richness," "community diversity," and "microbial richness and diversity" should be carefully specified.

R50: Yes. We have carefully reviewed the entire text and standardized the terminology.

Q51. Line 312: Rewrite the sentence "these results were consistent with the established composting microbiota profiles."

R51: Yes. We have modified the “these results were consistent with the established composting microbiota profiles” to “this result is consistent with the microbial community lineages observed in previous studies on composting”.

Q52. Line 313: The term "heightened" should be replaced.

R52: Yes. We have modified the “heightened” to “enhanced”.

Q53. Figures 5 and 6: Increase the clarity of the figures.

R53: Done.

Q54. Lines 348 and 349: The subtitles should be separated. pp) Lines 408 and 409: the “Data Availability Statement” is inadequate.

R54: Done.

 

 

Special thanks to you for your good comments.

 

We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in revised paper. We appreciate for Editors/Reviewers’ warm work earnestly, and hope that the correction will meet with approval. Once again, thank you very much for your comments and suggestions.

 

With best wishes,

Yours sincerely,

Cheng Hu (correspondence author)

 

Reviewer 2 Report

Comments and Suggestions for Authors

Comments on the manuscript ‘Biochar effectively reduced the emission of N2O during anoxic composting and NH3 during aerobic composting’:

• In this research, a structured study was conducted on the effects of biochar on NH₃ and N₂O emissions during aerobic and anoxic composting.
• The English writing of the manuscript is good, and there seems to be no problem.

Introduction:

• The introduction is structured appropriately, and the research background, research gap, and study objectives are clearly presented.

Materials and methods:

• What was the basis for choosing a 10% level of biochar and no other levels? Comparing different rates of biochar would likely provide a more comprehensive understanding.
• Although Table 1 lists the basic properties of biochar, other important properties of biochar, including pyrolysis temperature, surface area, porosity, and elemental composition, are not provided.
• Details of aerobic and anoxic composting are not mentioned. The aeration regime needs to be clearly defined in the Methods for aerobic composting (e.g., frequency and duration of turning, airflow volumes if mechanical aeration is used). What exactly determines the "anoxic" state - was it only limited in terms of oxygen (sealed), or just naturally ventilated with no mechanical aeration?
• The locations of the temperature sensors in the pile should be clearly outlined to ensure the accuracy and representativeness of the data collected.

 

Results and discussion:

• The results of the study are well presented, and the interpretation of the results and their comparison with relevant literature and references are done in an acceptable manner.

Conclusion:

• The conclusion section is written coherently and is consistent with the experimental results.

General considerations and questions:

• In your opinion, do fungi and other microorganisms (in addition to bacteria) have any effects or interference in the composting process? Is the lack of consideration for other microorganisms, besides bacteria, viewed as a limitation in this study?
• Did other greenhouse gases, such as methane (CH₄), have any effect or interference on the results?

Author Response

Response to the Reviewer 2

 

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Biochar effectively reduced the emission of N₂O during anoxic composting and NH₃ during aerobic composting” (ID: agriculture-3832971). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. The responds to the reviewer’s comments, point by point, are as flowing:

 

Reviewer #2:

Comments on the manuscript ‘Biochar effectively reduced the emission of N₂O during anoxic composting and NH₃ during aerobic composting’:

In this research, a structured study was conducted on the effects of biochar on NH₃ and N₂O emissions during aerobic and anoxic composting.

The English writing of the manuscript is good, and there seems to be no problem.

Introduction:

The introduction is structured appropriately, and the research background, research gap, and study objectives are clearly presented.

Materials and methods:

What was the basis for choosing a 10% level of biochar and no other levels? Comparing different rates of biochar would likely provide a more comprehensive understanding.

Although Table 1 lists the basic properties of biochar, other important properties of biochar, including pyrolysis temperature, surface area, porosity, and elemental composition, are not provided.

Details of aerobic and anoxic composting are not mentioned. The aeration regime needs to be clearly defined in the Methods for aerobic composting (e.g., frequency and duration of turning, airflow volumes if mechanical aeration is used). What exactly determines the "anoxic" state - was it only limited in terms of oxygen (sealed), or just naturally ventilated with no mechanical aeration?

The locations of the temperature sensors in the pile should be clearly outlined to ensure the accuracy and representativeness of the data collected.

Results and discussion:

The results of the study are well presented, and the interpretation of the results and their comparison with relevant literature and references are done in an acceptable manner.

Conclusion:

The conclusion section is written coherently and is consistent with the experimental results.

General considerations and questions:

Q1. What was the basis for choosing a 10% level of biochar and no other levels? Comparing different rates of biochar would likely provide a more comprehensive understanding.

R1: Previous studies have examined the effects of a wide range of biochar application rates from 3% to 50%. Some researchers have discouraged the use of amounts higher than 10% because the addition of excess biochar causes severe water loss and heat dissipation, which can adversely affect the composting process. The cost of biochar can also be a limiting factor in deciding on the quantity applied. In general, however, an application rate of between 5% and 10% (by weight) is recommended in composting studies. For specific references, please consult the literature: (Neslihan Akdeniz, A systematic review of biochar use in animal waste composting, Waste Management, Volume 88,2019.)

Q2. Although Table 1 lists the basic properties of biochar, other important properties of biochar, including pyrolysis temperature, surface area, porosity, and elemental composition, are not provided.

R2: Thank you for your suggestion. We have added additional information about biochar.

Q3. Details of aerobic and anoxic composting are not mentioned.

R3: Thank you for your suggestion. We have added specific details about composting.

Q4. The aeration regime needs to be clearly defined in the Methods for aerobic composting (e.g., frequency and duration of turning, airflow volumes if mechanical aeration is used).

R4: Yes. We have made the necessary changes. The composting process spans 45 days. Manual turning operations serve as the aeration method for aerobic composting and last approximately 10 minutes. Periodic manual turning of the substrate is included on Days 7, 15, 24 and 33 to ensure homogeneity and aeration.

Q5. What exactly determines the "anoxic" state - was it only limited in terms of oxygen (sealed), or just naturally ventilated with no mechanical aeration?

R5: Yes. The term “anaerobic” conditions in this study primarily refers to environments with natural ventilation but no mechanical ventilation.

Q6. The locations of the temperature sensors in the pile should be clearly outlined to ensure the accuracy and representativeness of the data collected.

R6: Yes. The pile temperature is determined by taking three measurements with a thermometer at the upper, middle, and lower sections of the pile, then averaging the results to establish the overall pile temperature.

General considerations and questions:

Q7. In your opinion, do fungi and other microorganisms (in addition to bacteria) have any effects or interference in the composting process?

R7: Fungi and actinomycetes indeed exert influences on the composting process; however, this study did not prioritize investigating their specific effects. Furthermore, experimental replicates were implemented across different treatment groups to mitigate potential interference.

Q8. Is the lack of consideration for other microorganisms, besides bacteria, viewed as a limitation in this study?

R8: This study primarily focused on the effects of biochar addition on N₂O and NH₃ emissions under different composting methods, as well as the dynamics of bacterial communities during the composting process. Although fungi and actinomycetes also play crucial roles in organic matter decomposition, their influences were not included in the scope of this analysis. Replicates and randomized experimental designs were implemented to control potential variations introduced by these unmeasured factors. Future research will integrate eukaryotic microbial community analysis to more comprehensively elucidate the microbial driving mechanisms of composting.

Q9. Did other greenhouse gases, such as methane (CH₄), have any effect or interference on the results?

R9: Other greenhouse gases do not affect the experimental results. This study focused specifically on the impact of biochar on nitrogen emissions (N₂O and NH₃) and did not monitor the fluxes of other greenhouse gases such as methane (CH₄). The production of CH₄ serves as an indicator of anaerobic conditions, which are also conducive to denitrification that generates N₂O.

 

 

 

Special thanks to you for your good comments.

 

We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in revised paper. We appreciate for Editors/Reviewers’ warm work earnestly, and hope that the correction will meet with approval. Once again, thank you very much for your comments and suggestions.

 

With best wishes,

Yours sincerely,

Cheng Hu (correspondence author)

 

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript „Biochar effectively reduced the emission of N2O during anoxic 2 composting and NH3 during aerobic composting“ by Zhang et al. reports the effects of adding biochar to composting of manure under anoxic and aerobic condition. The manuscript is well written and the experiments and statistical analysis adequate. It offers interesting information on the application of biochar in composting process and shows that it can be beneficial to counteract the well known nitrogen losses during the process. 

However, in the introduction section the references are lost. The authors have to fix that before the article can be published.

Author Response

Response to the Reviewer 3

 

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Biochar effectively reduced the emission of N₂O during anoxic composting and NH₃ during aerobic composting” (ID: agriculture-3832971). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. The responds to the reviewer’s comments, point by point, are as flowing:

 

Reviewer #3:

The manuscript “Biochar effectively reduced the emission of N₂O during anoxic composting and NH₃ during aerobic composting” by Zhang et al. reports the effects of adding biochar to composting of manure under anoxic and aerobic condition. The manuscript is well written and the experiments and statistical analysis adequate. It offers interesting information on the application of biochar in composting process and shows that it can be beneficial to counteract the well known nitrogen losses during the process.

However, in the introduction section the references are lost. The authors have to fix that before the article can be published.

Reply: We appreciate the positive feedback and valuable comments. We have thoroughly reviewed and supplemented the references in the introduction section, and all missing citations have been corrected.

 

 

Special thanks to you for your good comments.

 

We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in revised paper. We appreciate for Editors/Reviewers’ warm work earnestly, and hope that the correction will meet with approval. Once again, thank you very much for your comments and suggestions.

 

With best wishes,

Yours sincerely,

Cheng Hu (correspondence author)

 

Reviewer 4 Report

Comments and Suggestions for Authors

Authors did valuable study about different composting approaches and their influence to N₂O and NH₃ emissions. Used methodology was satisfactory as well as is very well written, and achieved results indicates major differences between composting methods and role of additives. Moreover, achieved results were deeply discussed.

Still there are some minor issues in respect to manuscript. In introduction and methods are errors to references which not allowed to precisely track used references. Very surprising is carbon content for biochar represented in Table 1 which is rather low for this material. For produced biochar potentially are  other detected parameters such as surface area etc. Those numbers in methods could more explain properties of used material. There is no identification or discussion about bacteria originated from dong, but more justified their changes during composting process.

Author Response

Response to the Reviewer 4

 

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Biochar effectively reduced the emission of N₂O during anoxic composting and NH₃ during aerobic composting” (ID: agriculture-3832971). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. The responds to the reviewer’s comments, point by point, are as flowing:

 

Reviewer #4:

Authors did valuable study about different composting approaches and their influence to N₂O and NH₃ emissions. Used methodology was satisfactory as well as is very well written, and achieved results indicates major differences between composting methods and role of additives. Moreover, achieved results were deeply discussed.

Still there are some minor issues in respect to manuscript. In introduction and methods are errors to references which not allowed to precisely track used references. Very surprising is carbon content for biochar represented in Table 1 which is rather low for this material. For produced biochar potentially are other detected parameters such as surface area etc. Those numbers in methods could more explain properties of used material. There is no identification or discussion about bacteria originated from dong, but more justified their changes during composting process.

Q1. Still there are some minor issues in respect to manuscript. In introduction and methods are errors to references which not allowed to precisely track used references.

R1: Thank you for highlighting this issue. We have carefully reviewed and corrected the reference errors in both the Introduction and the Materials and Methods sections to ensure the accuracy and traceability of all citations.

Q2. Very surprising is carbon content for biochar represented in Table 1 which is rather low for this material.

R2: Thank you for this important observation. The carbon content data for biochar in Table 1 has been verified and is accurate. The relatively low value may be attributed to the specific feedstock properties or pyrolysis conditions used in the biochar production. We would be happy to provide additional details if needed.

Q3. For produced biochar potentially are other detected parameters such as surface area etc. Those numbers in methods could more explain properties of used material.

R3: Thank you for your valuable suggestion. As recommended, we have included additional key parameters of the biochar (such as surface area, etc.) in the Methods section. These data help to better elucidate the properties of the material used.

Q4. There is no identification or discussion about bacteria originated from dong, but more justified their changes during composting process.

R4: Thank you for this important comment. The current study primarily focused on changes in the microbial community during the composting process, and therefore did not include separate identification or discussion of bacteria originating from feces. We agree that such analysis could provide further insight, and will consider addressing this aspect in future work.

 

Special thanks to you for your good comments.

We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in revised paper. We appreciate for Editors/Reviewers’ warm work earnestly, and hope that the correction will meet with approval. Once again, thank you very much for your comments and suggestions.

 

With best wishes,

Yours sincerely,

Cheng Hu (correspondence author)

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Please see my comments in the attached document.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Please see my comments in the attached document.

Author Response

Response to the Reviewers

 

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Biochar effectively reduced the emission of N₂O during anoxic composting and NH₃ during aerobic composting” (ID: agriculture-3832971). The responds to the reviewer’s comments, point by point, are as flowing:

 

This is a revision of the second version of the manuscript, which did not incorporate many of the suggestions made in the first version. Furthermore, some inaccuracies demonstrate that the manuscript seems to have been written sloppily and in a rush. One of the key aspects to be addressed is the authors' insistence on using the term anoxic composting, which is incorrect for the process they employ. The authors need to describe each composting process better and use the appropriate term for the type of composting performed without turning and forced aeration. See below a series of inconsistencies in the manuscript:

1. a) The manuscript is not well written in English – poor English. This issue must be addressed.

R: Thank you for your suggestion. The manuscript was improved by MDPI author services.

 

 

1. b) In the title itself, the manuscript presents a questionable aspect regarding the term "anoxic", which was misused, as it indicates the absence of oxygen, which is incorrect. There is abundant literature on composting methods in this regard.

R: Thank you for your suggestion. Recently growing interest is focused on facultative heap composting in China. The concepts and definitions of the different composting measures have remained inconclusive. In our previous studies, we have distinguished the definitions of three composting. (1) Heap composting, composting using manure without bulking agent and turning or forced aeration. (2) Anoxic composting, composting mixing manure and bulking without turning or forced aeration. (3) Aerobic composting, composting mixing manure and bulking with turning or forced aeration. Nonetheless, we have modified the “anoxic composting” to “heap composting” in this study to avoid unnecessary misunderstandings.

 

1. c) Authors should use the results and discussion to highlight the novelty and contribution to current knowledge.
2. d) The manuscript may be relevant to the field of study if the reviewers' suggestions are followed.

R: Thank you for your suggestion. We tried our best to improve the manuscript.

 

1. e) Line 2: Suppress the term "anoxic” from the text once and for all. It does not make any sense in the present case. Therefore, with this word included, the manuscript title becomes absurd and completely incorrect."

R: Done.

 

1. f) Line 19: Revise the sentence "to compare the difference."

R: Thank you for your suggestion. We have modified as “to clarify the difference”.

 

1. g) Line 20: Clarify how many experiments were performed.

R: Thank you for your suggestion. We have modified as “The experiment was”.

 

1. h) Lines 27 to 32: Rewrite, as these statements cannot be made because they were not observed.

R: The sentence has rewritten as “Biochar reduced nitrogen losses, especially N₂O emissions during heap composting and NH₃ emissions during aerobic composting”.

 

1. i) Line 52: The sentence "...that the addition-modified cornstalk..." is incorrect.

R: The sentence has modified as “…reported that cornstalk biochar could regulate nitrification processes, thereby reducing NH₃ emissions during layer manure composting”.

 

1. j) Line 63: The sentence "...practices that employed on livestock farms..." is incorrect.

R: The sentence has modified as “… adopted in livestock farms...”.

 

1. k) Line 97: "Rapeseed straw" is incorrect.

R: It was modified as “corn straw”.

 

1. l) Lines 104 to 105: Clarify which of the materials corresponds to a ratio of 3 and which material corresponds to a ratio of 1.

R: We have demonstrated “fresh cow manure and straw at a 3:1 mass ratio”.

 

1. m) Lines 109 to 114: The text is very confusing: each process should be described separately in relation to turning and aeration.

R: The sentence has modified as “After mixing the initial materials, no turning or forced aeration in C1 and BC1 treatment, but manual turning was performed on day 7, 15, 24 and 33 in C2 and BC2 treatment. The experiment lasted 45 days”.

 

1. n) Lines 141 and 142: The Shannon and Chao1 indices should be described, or a reference provided. Lines 205, 256, and 249: Subtitles should be presented separately.

R: We have added “which represent microbial community richness and diversity, respectively”.

 

1. o) Line 243: The sentence “Yang et al. [28] that a decrease...” is incorrect.

R: It was modified as “Yang et al. [28] reported that a decrease…”.

 

 

With best wishes,

Yours sincerely,

Cheng Hu (correspondence author)