Characteristics of Biochars Derived from the Pyrolysis and Co-Pyrolysis of Rubberwood Sawdust and Sewage Sludge for Further Applications

Round 1

Reviewer 1 Report

The presented work "Characteristics of biochars derived from the pyrolysis and co-pyrolysis of rubberwood sawdust and sewage sludge for further applications" can, in the given form, be rather taken for analysis of samples from pyrolysis and co-pyrolysis.

The submitted manuscript lacks:

1. reasoning of the choice of feedstock for the production of biochar as a fertilizer and, at the same time, comparison with the best available biochar produced from other bio-waste,
2. deeper analysis of the use of biochar produced by pyrolysis and co-pyrolysis of RBS, SS and their blends in other applications for their most suitable use,
3. discussion about other technological usability of RWS, SS and their blends,
4. composition of raw materials before pyrolysis.

 

Unfortunately, based on the above-mentioned shortcomings of the manuscript, I cannot recommend its publication.

Author Response

Response to the comments of reviewers on a manuscript entitled “Biochar characteristics derived from the pyrolysis and co-pyrolysis of rubberwood sawdust and sewage sludge for further applications” (Manuscript ID: sustainability-1607167)

 

The authors thank the editor and reviewers for giving us a chance to improve this manuscript. All comments have been carefully considered and addressed by the authors. The writing and contents were improved throughout the manuscript. Responses to the comments of reviewers are shown in the revised manuscript with specific page and line numbers. All changes were highlighted by the “YELLOW” color in the revised manuscript.

 

Reviewer # 1:

The presented work "Characteristics of biochars derived from the pyrolysis and co-pyrolysis of rubberwood sawdust and sewage sludge for further applications" can, in the given form, be rather taken for analysis of samples from pyrolysis and co-pyrolysis.

The submitted manuscript lacks:

1. reasoning of the choice of feedstock for the production of biochar as a fertilizer and, at the same time, comparison with the best available biochar produced from other bio-waste,
2. deeper analysis of the use of biochar produced by pyrolysis and co-pyrolysis of RBS, SS and their blends in other applications for their most suitable use,
3. discussion about other technological usability of RWS, SS and their blends,
4. composition of raw materials before pyrolysis.

Unfortunately, based on the above-mentioned shortcomings of the manuscript, I cannot recommend its publication.

Comments:

- The authors thank to reviewer #1 for giving the suggestions and indicating the weak points of this manuscript. These comments are valuable aspects to improve this study. The authors hope that the reviewer will give the chance to consider the revised manuscript and agree to publish this study in this journal.

 

1. Reasoning of the choice of feedstock for the production of biochar as a fertilizer and, at the same time, comparison with the best available biochar produced from other bio-waste,

- The authors have chosen these biomasses as local waste raw materials for feedstocks to produce valuable energy products in previous work (Ali et al. doi:10.1007/s11356-021-15283-6.), due to the cheapest in cost and easy availability and was try to reuse and deplete the waste burden on the environment which. Secondly, the rubberwood sawdust (RWS) biomass was combined with the sewage sludge (SS) waste as clean biomass without any harmful contaminants; it decreased some polluted elements from the SS side, especially Pb, as shown in Table 1. The C, K, Mg, Ca, K, and P are the fundamental nutrients for the soil crops to help in growths (1-Jeguirim, M.; Goddard, M.-L.; Tamosiunas, A.; Berrich-Betouche, E.; Azzaz, A.A.; Praspaliauskas, M.; Jellali, S. Olive Mill Wastewater: From a Pollutant to Green Fuels, Agricultural Water Source and Bio-Fertilizer. Biofuel Production. Renew. Energy 2020, 149, 716–724, doi:10.1016/j.renene.2019.12.079.; 2- Dai, Z.; Meng, J.; Muhammad, N.; Liu, X.; Wang, H.; He, Y.; Brookes, P.C.; Xu, J. The Potential Feasibility for Soil Improvement, Based on the Properties of Biochars Pyrolyzed from Different Feedstocks. J. Soils Sediments 2013, 13, 989–1000, doi:10.1007/s11368-013-0698-y.; 3- Novotny, E.H.; Maia, C.M.B. de F.; Carvalho, M.T. de M.; Madari, B.E. Biochar: Pyrogenic Carbon for Agricultural Use-a Critical Review. Rev. Bras. Ciênc. Solo 2015, 39, 321–344.), it can be seen that in our work RWSB and SSB (biochars), these all nutrients are available in higher quantities. May it be considered for further applications without other anxious elements such as Pb and Cd. So, we also tried to compare our biochars results with other best biochars in the whole manuscript.

 

 

2. Deeper analysis of the use of biochar produced by pyrolysis and co-pyrolysis of RBS, SS and their blends in other applications for their most suitable use,

The analyses with the reasoning of biochar appropriate application were briefly discussed in the results and discussion section and tried to compare with best biochars; please see the results and discussion section.

 

3. Discussion about other technological usability of RWS, SS and their blends,

We have tried to discuss the application of RWSB, SSB, and theirs blends in the results and discussion section; please see pages no 8 and 13 and lines no 350-353; 562-567.

 

4. Composition of raw materials before pyrolysis.

- We have already done the comparison of the material before pyrolysis in our previous work, please see this article (Ali, L.; Palamanit, A.; Techato, K.; Baloch, K.A.; Jutidamrongphan, W. Valorization of Rubberwood Sawdust and Sewage Sludge by Pyrolysis and Co-Pyrolysis Using Agitated Bed Reactor for Producing Biofuel or Value-Added Products. Environ. Sci. Pollut. Res. 2021, doi:10.1007/s11356-021-15283-6.).

Reviewer 2 Report

Comments to author

This manuscript characterized the biochar, produced from two different feedstock/their proportion through slow pyrolysis technologies. Analysis was performed following standard protocol. This study could be useful to identify the properties of biochar produced from rubberwood sawdust and sewage sludge. Some minor revision are suggested below.

- Introduction section is long and can be shortened. For example, author may merge first and second paragraph to provide the environmental and agronomic significance of biochar. 

Line 32: P, K, Ca and Mg are not trace elements.

Line 50: Redundancy; crops and plants. You may delete ‘plants’

Line 98: What are those undesired components? Specify!

Line 102-103: Provide reference

Line 121: Adoption field? not clear.

Line 183: Check numbering. Instead of 3, it may be 2.2 and so on for 4 and 5 - you have again mentioned number 3 in the line 285 under result and discussion section.   

Line 353: You have already mentioned in line 334, thus, you may delete the sentence.

Line 373-376: Difficult to follow the sentence. You may provide the ranges for each element in the parenthesis for example, Si (6731-102415.3), Ca (…) and so on!

Line 377: List out the name of pollutant contaminants.

Line 394-396: This is a speculation. You may provide reference of some relevant studies to support your statement.

Line 640: Significantly higher than what?

Line 642: Comparable? Please elaborate and compare your results with their to make it clear.  

 

Author Response

Response to the comments of reviewers on a manuscript entitled “Biochar characteristics derived from the pyrolysis and co-pyrolysis of rubberwood sawdust and sewage sludge for further applications” (Manuscript ID: sustainability-1607167)

The authors thank the editor and reviewers for giving us a chance to improve this manuscript. All comments have been carefully considered and addressed by the authors. The writing and contents were improved throughout the manuscript. Responses to the comments of reviewers are shown in the revised manuscript with specific page and line numbers. All changes were highlighted by the “YELLOW” color in the revised manuscript.

Reviewer # 2:

This manuscript characterized the biochar, produced from two different feedstock/their proportion through slow pyrolysis technologies. Analysis was performed following standard protocol. This study could be useful to identify the properties of biochar produced from rubberwood sawdust and sewage sludge. Some minor revision are suggested below.

 

1. Introduction section is long and can be shortened. For example, author may merge first and second paragraph to provide the environmental and agronomic significance of biochar

- Thank you for your valuable suggestion; we have merged both paragraphs in one and specified environmental and agronomic aspects of biochar; please see pages no1-2 and lines no 43-67.

 

2. Line 32: P, K, Ca and Mg are not trace elements.

- This sentence has been rewritten and improved; please see page no 1 and lines no 31-32.

 

3. Line 50: Redundancy; crops and plants. You may delete ‘plants’

- The same meaning words are removed; please see page no 2 and line no 50.

 

4. Line 98: What are those undesired components? Specify!

- The missing information is added in the sentence for complete meaning; please see page no 2 and lines no 94-97.

 

5. Line 102-103: Provide reference.

- We are sorry this sentence was be deleted due to repetitions.

 

6. Line 121: Adoption field? not clear.

We are sorry this sentence was also deleted from this section, and we revised it in other meaningful sentences.

 

7. Line 353: You have already mentioned in line 334, thus, you may delete the sentence.

- The same sentence's repetition was deleted; please see page no 9.

 

8. Lines 373-376: Difficult to follow the sentence. You may provide the ranges for each element in the parenthesis for example, Si (6731-102415.3), Ca (…) and so on!

- The all-elements values were written inside brackets; please see page no 9 and lines no 379-382.

 

8. Line 377: List out the name of pollutant contaminants.

-The sentence is improved with nominated contaminates; please see page no 9 and lines no 382-386.

 

9. Line 394-396: This is a speculation. You may provide reference of some relevant studies to support your statement.

- The required reference is cited to support this sentence; please see page no 9 and lines no 399-403.

 

10. Line 640: Significantly higher than what?

- This sentence was repeated and confusing, so this has been removed from the paragraph; please see page no 16.

 

11. Line 642: Comparable? Please elaborate and compare your results with their to make it clear.

- The sentence is rewritten and improved; please see page no 16 and lines no 654-655.

Reviewer 3 Report

Overall, the paper sounds very interesting and it represents a novel work in the field of biochar. Despite this, the article must be revised in order to eliminate some contradictions and lacks.

Generally, I think that most of the authors’ results are affected by the high ash content of their feedstock. For example, all the samples seem to not decompose in TGA. The high amount of inorganic matter masks the decomposition of the organic fraction and consequently, it is hard to understand the decomposition process and yield of the pyrolysis. Furthermore, they obtained carbons with very low specific surface area (18 m2/g). That result is not acceptable for possible application as biosorbent as they had written in different parts of the text. Please, consider to or activate those carbons or delete those sentences. The same consideration can be done for the possible use of the carbons as fertilizer. These carbons are full of heavy metals and I do not recommend using them in soil. Finally, I think that an ion exchange procedure is not possible in this case. Please, consider changing some purposes explained in the text. 

Then, please review:

line 29 ==> elemental analysis in stand of elemental component

line 30 ==> please rewrite this sentence. The atomic composition does not match with a functional group analysis such as IR spectroscopy

243 ==> add some more information about how the SSA has been performed. I also recommend adding a figure of the collected isotherms. The shape of the isotherm gives important information about the specific surface area and which type of porosity is present in the material.

Author Response

Response to the comments of reviewers on a manuscript entitled “Biochar characteristics derived from the pyrolysis and co-pyrolysis of rubberwood sawdust and sewage sludge for further applications” (Manuscript ID: sustainability-1607167)

The authors thank the editor and reviewers for giving us a chance to improve this manuscript. All comments have been carefully considered and addressed by the authors. The writing and contents were improved throughout the manuscript. Responses to the comments of reviewers are shown in the revised manuscript with specific page and line numbers. All changes were highlighted by the “YELLOW” color in the revised manuscript.

Reviewer # 3:

Overall, the paper sounds very interesting and it represents a novel work in the field of biochar. Despite this, the article must be revised in order to eliminate some contradictions and lacks.

Generally, I think that most of the authors’ results are affected by the high ash content of their feedstock. For example, all the samples seem to not decompose in TGA. The high amount of inorganic matter masks the decomposition of the organic fraction and consequently, it is hard to understand the decomposition process and yield of the pyrolysis. Furthermore, they obtained carbons with very low specific surface area (18 m²/g). That result is not acceptable for possible application as biosorbent as they had written in different parts of the text. Please, consider to or activate those carbons or delete those sentences. The same consideration can be done for the possible use of the carbons as fertilizer. These carbons are full of heavy metals and I do not recommend using them in soil. Finally, I think that an ion exchange procedure is not possible in this case. Please, consider changing some purposes explained in the text.

Then, please review:

1. Generally, I think that most of the authors’ results are affected by the high ash content of their feedstock. For example, all the samples seem to not decompose in TGA. The high amount of inorganic matter masks the decomposition of the organic fraction and consequently, it is hard to understand the decomposition process and yield of the pyrolysis. Furthermore, they obtained carbons with very low specific surface area (18 m²/g). That result is not acceptable for possible application as biosorbent as they had written in different parts of the text. Please, consider to or activate those carbons or delete those sentences. The same consideration can be done for the possible use of the carbons as fertilizer. These carbons are full of heavy metals and I do not recommend using them in soil. Finally, I think that an ion exchange procedure is not possible in this case. Please, consider changing some purposes explained in the text.

- The authors special thanks to reviewer #3 for deep review and great appreciation for our work. The main purpose of this work was to indicate the properties of produced biochar from RWS and SS by pyrolysis and find out how they can act or be capable of using this biochar in the field. However, we have followed your most valuable suggestion. So, we have revised our whole manuscript and tried to modify inside information for readers, as well as we also try to add helpful information to use carbons as fertilizer.

 

2. line 29 ==> elemental analysis in stand of elemental component.

- This was corrected and remained “elemental component to elemental analysis” as per suggestion; please see page no 1 and line no 29.

 

3. line 30 ==> please rewrite this sentence. The atomic composition does not match with a functional group analysis such as IR spectroscopy.

- This sentence was revised and corrected; please see page no 1 and lines no 30-31.

 

4. line 243 ==> add some more information about how the SSA has been performed. I also recommend adding a figure of the collected isotherms. The shape of the isotherm gives important information about the specific surface area and which type of porosity is present in the material.

- More detail about BET determination of biochars samples was added; please see page no 5 and lines no 237-246.

Reviewer 4 Report

This study  investigated the characteristics of biochars produced from RWS, SS, and their blends. The obtained results indicated that the SSB had high ash content and low carbon content. The topic falls within the scope of the journal. I have minor revision suggestions. 

Generally, this is correlated with the feedstock particle size and/or pyrolysis temperature, which are reported by the latest studies such as Deng et al. 2021, Waste Management; Yang et al. 2021, Bioresource Technology. I suggest the author to discuss this in the manuscript. However, the present citation lists were too long, half of them can be removed. Please revise.

L318, please check the accurate of the citation [66,67]. There are tons of studies associated with mitigation of N2O. 

Figs, please indicate all components in the legend.

 

Author Response

Response to the comments of reviewers on a manuscript entitled “Biochar characteristics derived from the pyrolysis and co-pyrolysis of rubberwood sawdust and sewage sludge for further applications” (Manuscript ID: sustainability-1607167)

The authors thank the editor and reviewers for giving us a chance to improve this manuscript. All comments have been carefully considered and addressed by the authors. The writing and contents were improved throughout the manuscript. Responses to the comments of reviewers are shown in the revised manuscript with specific page and line numbers. All changes were highlighted by the “YELLOW” color in the revised manuscript.

Reviewer # 4:

This study investigated the characteristics of biochars produced from RWS, SS, and their blends. The obtained results indicated that the SSB had high ash content and low carbon content. The topic falls within the scope of the journal. I have minor revision suggestions.

Generally, this is correlated with the feedstock particle size and/or pyrolysis temperature, which are reported by the latest studies such as Deng et al. 2021, Waste Management; Yang et al. 2021, Bioresource Technology. I suggest the author to discuss this in the manuscript. However, the present citation lists were too long, half of them can be removed. Please revise.

1. Generally, this is correlated with the feedstock particle size and/or pyrolysis temperature, which are reported by the latest studies such as Deng et al. 2021, Waste Management; Yang et al. 2021, Bioresource Technology. I suggest the author to discuss this in the manuscript.

Thank you for your appreciation and for forgiving more valuable corrections; we have read and followed these works mentioned above and added some information to our work. Please see pages no 2 and 3 and lines no 83-85 and 69 and 102-104, respectively.

 

2. However, the present citation lists were too long, half of them can be removed. Please revise.

The cited references in our work, we have tried to remove some extra references and revised them in the whole manuscript.

 

3. L318, please check the accurate of the citation [66,67]. There are tons of studies associated with mitigation of N₂O.

-The irrelevant citations have been removed from the sentences and add a relevant reference; please see page no 7 and line no 317-319.

 

4. Figs, please indicate all components in the legend.

- All components were indicated in the relevant legends; please see pages no 11-18.

Round 2

Reviewer 1 Report

I would like to thank to the authors for supplementing the submitted article for review. I have not any objections to the corrected version of the contribution.

In the future, I recommend the authors to provide a short review of their previous work, on which the submitted paper builds, whereby the choice of the input feedstock is reasoned.