Use of Biochar in Asphalts: Review

Round 1

Reviewer 1 Report

This is a concise review paper on a specific use of biochar as filling material for asphalts. Although very short the paper is of good quality and the methodological section is commendable.

Several critical points that authors are requested to address:

1. Eliminate the controversy of BC abbreviation. Line 32 defines BS as biochar whereas line 73 defines BS as biocarbon.
2. Chapter 1.2: authors forgot to note that charcoal and biochar are excellent absorbers with many useful applications as such e.g. they are extensively used as an absorption medium in purification of contaminated gaseous and aqueous radioactive effluents in nuclear industry (see the overviews with references there: IAEA. Treatment of Radioactive Gaseous Waste. IAEA-TECDOC-1744, IAEA, Vienna (2014), and An Introduction to Nuclear Waste Immobilisation, Third Edition, Elsevier, Amsterdam, 498 p. (2019)).
3. The conclusion section of paper looks too extended. Indeed, only the first and last paragraphs are really conclusions whereas the middle part of this section would be better placed in the paper as a separate Discussion section.

Author Response

5-april, 2022

Dear Editor and Reviewer 1,

 

We would like to thank you for your valuable and insightful comments that have helped us to improve our manuscript. Please find also in the following paragraphs our answers to the comments. We have tried our best to clarify all the points raised. We hope that this new version of the manuscript is satisfactory for publication.

 

 

Reviewer 1

 

This is a concise review paper on a specific use of biochar as filling material for asphalts. Although very short the paper is of good quality and the methodological section is commendable. Several critical points that authors are requested to address:

 

1. Eliminate the controversy of BC abbreviation. Line 32 defines BS as biochar whereas line 73 defines BS as biocarbon.

 

Answer: You're right. “Biocarbón” is the Spanish translation. We forgot to translate it. Thank you very much for your observation. We made the respective change in line 73.

 

2. Chapter 1.2: authors forgot to note that charcoal and biochar are excellent absorbers with many useful applications as such e.g. they are extensively used as an absorption medium in purification of contaminated gaseous and aqueous radioactive effluents in nuclear industry (see the overviews with references there: IAEA. Treatment of Radioactive Gaseous Waste. IAEA-TECDOC-1744, IAEA, Vienna (2014), and An Introduction to Nuclear Waste Immobilisation, Third Edition, Elsevier, Amsterdam, 498 p. (2019)).

 

Answer: You're right. For this reason, we write lines 97 to 98: “…vii) as absorbent material to remove from waste water, radioactive effluents in nuclear industry [44-47]”.  References 44 to 47 were placed.

 

3. The conclusion section of paper looks too extended. Indeed, only the first and last paragraphs are really conclusions whereas the middle part of this section would be better placed in the paper as a separate Discussion section.

 

Answer: We do not want to change the position of the conclusions obtained from the study. We improve the way they are presented (separating and numbering them) so that they are not so extensive views. We look forward to your understanding in this regard.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors , thank you very much for this interesting article. There are comments how you can improve it:

1. Collected references can be divided according main topics and shown graphically or in one table.
2. Using recovered bio char in various situations can cause not only positive effect but some obtained disadvantages must be included in this analysis.
3. By the end of yours article you can recommend some more numerical suggestions and express yours findings in percentage comparing with similar research.

Sincerely, Reviewer.

Author Response

5-april, 2022

Dear Editor and Reviewer 2,

 

We would like to thank you for your valuable and insightful comments that have helped us to improve our manuscript. Please find also in the following paragraphs our answers to the comments. We have tried our best to clarify all the points raised. We hope that this new version of the manuscript is satisfactory for publication.

 

Reviewer 2

 

Dear Authors, thank you very much for this interesting article. There are comments how you can improve it:

 

1. Collected references can be divided according main topics and shown graphically or in one table.

 

Answer: Taking into account your comment we made Tables 1-3 (see lines 293 to 394).

 

2. Using recovered bio char in various situations can cause not only positive effect but some obtained disadvantages must be included in this analysis.

 

Answer: You have reason. However, few studies show disadvantages of BC use. Taking into account your comment, we write some of them on lines 106 to 115. Regarding the use of BC as an asphalt binder modifier, some disadvantages are mentioned in conclusions (lines 316 to 318).

 

3. By the end of yours article you can recommend some more numerical suggestions and express yours findings in percentage comparing with similar research.

 

Answer: Thank you very much for your comment. Information on the subject is scarce. There is little numerical data to cite. However, in lines 321 to 325 we redact some numerical conclusions.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

The article presents a literature review on biochar in terms of its use in asphalts. The paper presents a description of biochar production and its main directions of application.
Biochar has similar properties to charcoal, however, it indicates its use in agriculture and environmental protection. It was already used in 19th century agricultural crops in Europe and South America. Currently, the properties of biochar are being rediscovered and new application areas include: bioenergy, waste management and climate change mitigation. Biochar can also be used for soil carbon sequestration, remediation of soil contaminated with organic and inorganic compounds. Biochar can be produced by pyrolysis of various materials, such as e.g. energy crops, forest waste, agricultural biomass, sewage sludge, waste from food production and processing, etc. organic carbon and mineral compounds, high porosity and specific surface, and thus sorption properties and retention of nutrients. Currently, biomass is used on a mass scale to produce electricity and heat under the banner of reducing CO2 emissions. In fact, only electricity production counts, as it is preferred by special certificates.
In the reviewed article, the authors analyzed items in the world literature dealing with the use of biochar in asphalt. This direction is not well understood yet, and the research works analyzed in this study do not provide unanimous conclusions.
The authors took up an interesting and important, from the point of view of environmental issues, topic related to the circular economy. On the basis of the conducted analysis of the collected literature, the necessary directions for further research on modification of asphalt mixtures with biochar have been presented.

Author Response

5-april, 2022

Dear Editor and Reviewer 3,

 

We would like to thank you for your valuable and insightful comments that have helped us to improve our manuscript. Please find also in the following paragraphs our answers to the comments. We have tried our best to clarify all the points raised. We hope that this new version of the manuscript is satisfactory for publication.

 

Reviewer 3

 

The article presents a literature review on biochar in terms of its use in asphalts. The paper presents a description of biochar production and its main directions of application.
Biochar has similar properties to charcoal, however, it indicates its use in agriculture and environmental protection. It was already used in 19th century agricultural crops in Europe and South America. Currently, the properties of biochar are being rediscovered and new application areas include: bioenergy, waste management and climate change mitigation. Biochar can also be used for soil carbon sequestration, remediation of soil contaminated with organic and inorganic compounds. Biochar can be produced by pyrolysis of various materials, such as e.g. energy crops, forest waste, agricultural biomass, sewage sludge, waste from food production and processing, etc. organic carbon and mineral compounds, high porosity and specific surface, and thus sorption properties and retention of nutrients. Currently, biomass is used on a mass scale to produce electricity and heat under the banner of reducing CO2 emissions. In fact, only electricity production counts, as it is preferred by special certificates. In the reviewed article, the authors analyzed items in the world literature dealing with the use of biochar in asphalt. This direction is not well understood yet, and the research works analyzed in this study do not provide unanimous conclusions.
The authors took up an interesting and important, from the point of view of environmental issues, topic related to the circular economy. On the basis of the conducted analysis of the collected literature, the necessary directions for further research on modification of asphalt mixtures with biochar have been presented.

 

Answer: You made a very interesting summary and analysis. Your comments are valuable. Thank you very much for your review.

Author Response File: Author Response.pdf