Effects of Pyrolysis Temperature on Biochar Physicochemical and Microbial Properties for H2S Removal from Biogas
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis article addresses the issue of sewage sludge, a problematic waste produced in sewage treatment plants even after anaerobic digestion, and its sustainable management. The study specifically investigates the use of pyrolyzed sewage sludge to create biochar that can be utilized as a filler in biofilters for the removal of hydrogen sulfide (H2S) from biogas. The research conducts an experimental and mathematical modeling analysis to understand the impact of pyrolysis temperature (ranging from 300°C to 600°C) on the physicochemical properties of the resulting biochar. These properties include porosity, specific surface area, pH, and electrical conductivity, which are crucial for the biochar's effectiveness in a biofiltration system designed to remove H2S. As a reviewer suggesting the publication of this study in "Sustainability," I would recommend addressing the following issues for improvement:
1. In the introduction, the urgent problems in this field are not highlighted, which makes the purpose of this research unclear? A more in-depth discussion is necessary, and the following work is available for reference.
Evaluation of biochar-derived carbocatalysts for pyrolytic conversion of sawdust: Life cycle assessment towards monophenol production. Fuel, 2022, 330: 125476.
Biochar assisted cultivation of Chlorella protothecoides for adsorption of tetracycline and electrochemical study on self-cultured Chlorella protothecoides. Bioresource Technology, 2023, 389: 129810.
2. The whole paper has only a first-level title and no second-level title, which makes the structure of the article confusing and difficult to read and understand.
3. In the results and discussion section, it is suggested to make a segmented description.
4. Why is Table 1 not found?
5. There are too many statements in the conclusion. I suggest condensing it into one paragraph to make it clearer.
Comments on the Quality of English LanguageExtensive editing of English language can be required
Author Response
Article: Effects of pyrolysis temperature on biochar physicochemical and microbial properties for H2S removal from biogas
Comments and responses to reviewer No. 1
COMMENTS AND RESPONSES:
Thank you for your relevant comments, we are sending comments. The corrections are shown in red in the text.
Regarding of note of English language, we have sent the article to MDPI's English editors for correction.
Ø 1. In the introduction, the urgent problems in this field are not highlighted, which makes the purpose of this research unclear? A more in-depth discussion is necessary, and the following work is available for reference.
Evaluation of biochar-derived carbocatalysts for pyrolytic conversion of sawdust: Life cycle assessment towards monophenol production. Fuel, 2022, 330: 125476.
Biochar assisted cultivation of Chlorella protothecoides for adsorption of tetracycline and electrochemical study on self-cultured Chlorella protothecoides. Bioresource Technology, 2023, 389: 129810.
On that basis, according to your recommendations, we have prepared a practically new introduction, which is much easier to read and understand than the previous one. That is, we have indicated how important it is to remove H2S from biogas and which packaging material is suitable for H2S removal. B. We also explained that pyrolysis is a way to convert sludge to biochar and how biochar meets the packaging material requirements by removing H2S. C. We explained that this work is expected to solve these two problems. Firstly, by studying the effect of pyrolysis on the properties of biochar and secondly, by using such biochar in a filter, to study the efficiency of the filter and to analyze the growth rate of bacteria in cleaning biogas from H2S.
In Line 29-108.
Thank you very much for suggesting a very good source of literature, which we have analyzed and cited. Scientists have done very useful research that aimed to prepare biochar-derived carbo-catalysts (BDCs) from three feedstocks (seaweed, microalga, and lignocellulosic bio-mass) and further evaluate the environmental impacts through life cycle assessment (LCA) methodology. In second study, the use of biochar and Chlorella protothecoides to jointly adsorb tetracycline is of great significance for environmental protection and microalgae cultivation.
In Line 45-53.
All corrections are marked in red in the text.
Ø 2. The whole paper has only a first-level title and no second-level title, which makes the structure of the article confusing and difficult to read and understand.
Thank you very much for your note. Thus, we structured the methodology section and the results and discussions section. On that basis, in the methodology section we added 3 subsections (2.1. Completion of the sewage sludge pyrolysis process; 2.2. The determination of the significant physicochemical properties of the biofilter packing material; 2.3. The preparation for biofiltration process) and supplemented the text along with a photo of the experiment.
All corrections are marked in red in the text. In Line 110, 119, 169.
Ø 3. In the results and discussion section, it is suggested to make a segmented description.
Thank you very much for your note. Analogously, in the results and discussions section we added 3 subsections (3.1. The results of the physicochemical properties of pyrolyzed biochar; 3.2. Biofiltration performance and kinetic study of hydrogen sulfide removal; 3.3. Microbiological studies of the packing material and removal efficiency of hydrogen sulfide).
All corrections are marked in red in the text. In Line 226, 286, 337.
Ø 4. Why is Table 1 not found?
Table 1 should not have been. there was simply a numbering error here. Thank you very much for your comment, we have corrected it.
All corrections are marked in red in the text. In Line 268, 279.
Ø 5. There are too many statements in the conclusion. I suggest condensing it into one paragraph to make it clearer.
We agree that the conclusions contained too much information. Thus, we condensed the conclusions and we left only the main conclusions of our work to make it clearer.
All corrections are marked in red in the text. In Line 407-429.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsIn the manuscript of Sustainability-3047164, I can understand the author hope to present a work of studying temperaure on sludge derived biochar properties, and further applying the biochar as a packing material in biofilters for removing the H2S from biogas as well as investigating the relevant bacterial growth rate. Althogh the topic is good and very close to practial application, the quality of this manuscript is still very poor. I hereby suggest a major revision on this work, hope the author could seize the chance to improve the quality of the work.
Comments,
(1) The title is not correct. As I can not get what kind of story did the author hope to tell. The current title told two separated things, 1) pyrolysis affected biochar property 2) bacterial growth rate... The two topic showed no relations. In addition, I can not see any information about mathematic modelling in the entire work. Therefore, I suggest the author could carefully consier about revising the title of this work.
(2) The Introduction part is terrible....The language need to be concised and the logic should be clearly stated. I understand the autuor are not very good at using English, It doesn't matter, as English is not my first language either. Try to rearrange the introduction in your own language and translate it into English. A suggested outline might be a. State the importance of removing H2S from biogas and what kind of packing material is good for H2S removal. b. Current situation of digestate/sludge generation, pyrolysis provide a way to convert sludge to biochar, and how biochar meet the requrement of packing material in H2S removal. c. this work hope to solve the two issues by using an integrating way, first, investigating the impacts of pyrolysis on biochar properties. second, applying these biochar into H2S removal biofilter and investigate the effect of H2S removal baterial growth rate.
(3) Section of Method and material, just state the experiment desigh and relevant method, no need to provide useless information such as science popularization.
(4) Whether methane will be affected in biofilter, such adsorbed by the biochar/packing material, or degredaded by microorganisms.
(5) It is highly suggested the author to cite https://doi.org/10.3390/polym15122741 in the revised manuscript as it is regarding to biochar properties from waste biomass.
Hoping the author could revise their manuscript by following these comments, and significantly improve the quality of their work.
Comments on the Quality of English LanguageEnglish quality is not good enough. But the most important thing is to make the outline and logic of this work more clear.
Author Response
Article: Effects of pyrolysis temperature on biochar physicochemical and microbial properties for H2S removal from biogas
Comments and responses to reviewer No. 2
COMMENTS AND RESPONSES:
Thank you for your relevant comments, we are sending comments. The corrections are shown in red in the text.
Regarding of note of English language, we have sent the article to MDPI's English editors for correction.
Ø 1. The title is not correct. As I can not get what kind of story did the author hope to tell. The current title told two separated things, 1) pyrolysis affected biochar property 2) bacterial growth rate... The two topic showed no relations. In addition, I can not see any information about mathematic modelling in the entire work. Therefore, I suggest the author could carefully consider about revising the title of this work.
According to your very good recommendations, the previous title of the article („Experimental and mathematical modelling of pyrolysis temperature’s impact on biochar physicochemical properties and bacterial growth rate to remove H2S from biogas“) has been changed to a new one („Effects of pyrolysis temperature on biochar physicochemical and microbial properties for H2S removal from biogas“).
Thank you very much for this recommendation/note. All corrections are marked in red in the text. In Line 1-3.
Ø 2.The Introduction part is terrible. The language need to be concised and the logic should be clearly stated. I understand the author are not very good at using English, It doesn't matter, as English is not my first language either. Try to rearrange the introduction in your own language and translate it into English. A suggested outline might be a. State the importance of removing H2S from biogas and what kind of packing material is good for H2S removal. b. Current situation of digestate/sludge generation, pyrolysis provide a way to convert sludge to biochar, and how biochar meet the requirement of packing material in H2S removal. c. this work hope to solve the two issues by using an integrating way, first, investigating the impacts of pyrolysis on biochar properties. second, applying these biochar into H2S removal biofilter and investigate the effect of H2S removal bacterial growth rate.
Yes, you are very right that the intro is terrible. On that basis, according to your recommendations, we have prepared a practically new introduction, which is much easier to read and understand than the previous one. That is, we have indicated how important it is to remove H2S from biogas and which packaging material is suitable for H2S removal. B. We also explained that pyrolysis is a way to convert sludge to biochar and how biochar meets the packaging material requirements by removing H2S. C. We explained that this work is expected to solve these two problems. Firstly, by studying the effect of pyrolysis on the properties of biochar and secondly, by using such biochar in a filter, to study the efficiency of the filter and to analyze the growth rate of bacteria in cleaning biogas from H2S.
Regarding of note of English language, we have sent the article to MDPI's English editors for correction. All corrections are marked in red in the text. In Line 29-108.
Ø 3. Section of Method and material, just state the experiment design and relevant method, no need to provide useless information such as science popularization.
Thank you very much for your note. Thus, we structured the methodology section and deleted unnecessary information that was related to the popularization of science. On that basis, we added 3 subsections (2.1. Completion of the sewage sludge pyrolysis process; 2.2. The determination of the significant physicochemical properties of the biofilter packing material; 2.3. The preparation for biofiltration process) and supplemented the text along with a photo of the experiment.
All corrections are marked in red in the text. In Line 110, 119, 169.
Ø 4. Whether methane will be affected in biofilter, such adsorbed by the biochar/packing material, or degraded by microorganisms.
Thank you very much for your comment. Yes, we have answered you how methane will be affected in the biofilter. During the research, it was found that the concentration of CH4 increased slightly during the desulfurization process. According to other researchers, the slight decrease in CO2 concentration in biogas was proportional to the recorded increase in CH4 concentration, from 60.0% to 61.7−63.5%, respectively.
All corrections are marked in red in the text. In Line 395-397.
Ø 5. It is highly suggested the author to cite https://doi.org/10.3390/polym15122741 in the revised manuscript as it is regarding to biochar properties from waste biomass.
Thank you very much for suggesting a very good source of literature, which we have analyzed and cited. This is a mature and promising approach as these products can be widely utilized in many areas such as carbon sequestration, power production, environmental remediation, and energy storage.
All corrections are marked in red in the text. In Line 41-45.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe management of sewage sludge is a very ecologically challenging issue due to the high concentration of pollutants. On the other hand, H2S in biogas represents a very undesirable component, which needs to be removed. The paper presents excellent experimental research that brings together a potential solution to both environmental issues. The application of pyrolysis as an economically and environmentally acceptable treatment of sewage sludge in order to obtain biochar, which has the ability to remove H2S from biogas, seems like an excellent solution. Certainly, scientific papers covering this area are interesting and necessary, but certain corrections are needed in order to improve the quality. My comments are as follows.
1. Introdustion
Interesting and important information can be read in the introduction, but the essence of the paper is the application of bacteria in order to remove H2S from biogas, which is not reviewed in the literature. Therefore, it is necessary to amend/supplement the introduction with a review of the literature that provides all relevant information about the type and origin of bacteria, about the mechanism of their action on the purification of biogas from H2S, about the influential parameters of that process, so a review of everything that is the essence of the work.
2. Materials and Methods
Add a schematic view and photos of the experimental plant with a detailed view of the parts and a description of the material flows.
Add photos by stages of sample preparation.
Everything has to be photo-documented.
After the paragraph explaining how bulk density was determined, add a short explanation of how porosity was determined.
3. Results and discussions
Add photos of biochar packing materials after pyrolysis, biofilters, SEM, etc. As I mentioned earlier, everything needs to be photo-documented, so that the paper is more meaningful and easier to follow and understand.
I don't insist, but for better clarity, it might be good to separate the text by the analyzed parameters.
4. Conclusion
The conclusion is a little bit longer, but it gives a nice overview of the most important results, that is, the conclusions drawn.
Line 380: bulk density 4 kg/m – please correct
The acknowledgment just has confirmed my impression that the paper resulted from research within the doctoral dissertation, because that is exactly how it was written, systematically with a lot of detail and analysis, but as I have already stated, each step needs to be supported with appropriate images.
Author Response
Article: Effects of pyrolysis temperature on biochar physicochemical and microbial properties for H2S removal from biogas
Comments and responses to reviewer No. 3
COMMENTS AND RESPONSES:
Thank you for your relevant comments, we are sending comments. The corrections are shown in red in the text.
Regarding of note of English language, we have sent the article to MDPI's English editors for correction.
In Introduction
Ø 1. Interesting and important information can be read in the introduction, but the essence of the paper is the application of bacteria in order to remove H2S from biogas, which is not reviewed in the literature. Therefore, it is necessary to amend/supplement the introduction with a review of the literature that provides all relevant information about the type and origin of bacteria, about the mechanism of their action on the purification of biogas from H2S, about the influential parameters of that process, so a review of everything that is the essence of the work.
Thank you very much for the interesting and relevant information you found in the introduction, but based on the comments of other reviewers, we have improved the introduction and cited the literature cited by other reviewers.
All corrections are marked in red in the text. In Line 29-108.
In Materials and Methods
Ø 2. Add a schematic view and photos of the experimental plant with a detailed view of the parts and a description of the material flows.
Thank you very much for your valuable suggestion, we have attached the device used in our experiments and photos with a detailed view and description of the materials. This is Figure number 1.
All corrections are marked in red in the text. In Line 199.
Ø 3. Add photos by stages of sample preparation.
Attached photos according to the stages of sample preparation, you will find in Figures 1.
All corrections are marked in red in the text. In Line 199.
Ø 4. Everything has to be photo-documented.
Thank you very much for the comment, but we have added photos as much as possible. We will prepare more photos in future articles.
Ø 5. After the paragraph explaining how bulk density was determined, add a short explanation of how porosity was determined.
Thank you very much for your comment, we have added a brief explanation of how porosity was determined:
the t-plot strategy is a significant method that was designed based on the New Source Performance Standards (NSPS) and permits deciding the miniature as well as meso-porous volumes and the particular surface region of an example.
All corrections are marked in red in the text. In Line 131-134.
In Results and discussions
Ø 6. Add photos of biochar packing materials after pyrolysis, biofilters, SEM, etc. As I mentioned earlier, everything needs to be photo-documented, so that the paper is more meaningful and easier to follow and understand.
As we answered you earlier, we added photos, the paper would be more meaningful, easier to follow and understand. For other photos (SEM, etc) according to recommendations, we will prepare more photos in future articles.
Ø 7. I don't insist, but for better clarity, it might be good to separate the text by the analyzed parameters.
Thank you very much for your note. we agree with you that for greater clarity it might be useful to separate the text according to the parameters being analyzed. So we did:
Thus, we structured the methodology section and the results and discussions section. On that basis, in the methodology section we added 3 subsections (2.1. Completion of the sewage sludge pyrolysis process; 2.2. The determination of the significant physicochemical properties of the biofilter packing material; 2.3. The preparation for biofiltration process) and supplemented the text along with a photo of the experiment.
In Line 110, 119, 169.
Analogously, in the results and discussions section we added 3 subsections (3.1. The results of the physicochemical properties of pyrolyzed biochar; 3.2. Biofiltration performance and kinetic study of hydrogen sulfide removal; 3.3. Microbiological studies of the packing material and removal efficiency of hydrogen sulfide).
In Line 226, 286, 337.
All corrections are marked in red in the text.
In Conclusions
Ø 8. The conclusion is a little bit longer, but it gives a nice overview of the most important results, that is, the conclusions drawn.
Thank you very much for your comments, we have shortened the conclusions. Thus, we left only the main conclusions of our work to make it clearer.
All corrections are marked in red in the text. In Line 407-429.
All corrections are marked in red in the text.
Ø 9. Line 380: bulk density 4 kg/m – please correct
Thank you very much for your note. We deleted this line, so we have nothing to show that we fixed it.
The acknowledgment just has confirmed my impression that the paper resulted from research within the doctoral dissertation, because that is exactly how it was written, systematically with a lot of detail and analysis, but as I have already stated, each step needs to be supported with appropriate images.
Thank you very much for our recognition, appreciation and kind words. If we don't give up, in the future we want to make a breakthrough in our science to explore even more and discover new things.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAccept
Comments on the Quality of English LanguageAccept
Author Response
Comments and Suggestions for Authors: Accept Comments on the Quality of English Language: Accept Response: Many thanks to the reviewer for the feedback.Reviewer 2 Report
Comments and Suggestions for AuthorsThe comments from me were well addressed in the revised manuscript.
Author Response
Comments: The comments from me were well addressed in the revised manuscript.
Response: Many thanks to the reviewer for the feedback.
