Proposal for Implementation of Extraction Mechanism of Raw Materials during Landfill Mining and Its Application in Alternative Fuel Production

Round 1

Reviewer 1 Report

The used research methods are appropriate. The research material is
sufficient. Methods section how all of the data in the Results section were cleary described. The study system were clearly described.
The way of the development and interpretation of the results
are considered to be appropriate. References selection are appropriate.

Author Response

Subject: Revision of manuscript Sustainability-2210633

Reviewer #1

Dear Reviewer,

The authors are grateful to you for the time and effort in reviewing the manuscript and the opportunity to publish the results of our research.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript proposes to assess the feasibility of extracting and recovering raw materials from landfills by developing a waste extraction mechanism and creating an SRF production line. The document is weak it needs improvement. Consider my comments in the attached file.

Comments for author File: Comments.pdf

Author Response

Subject: Revision of manuscript Sustainability-2210633

Reviewer #2

Dear Reviewer,

The authors are grateful to you for the time and effort in reviewing the manuscript and the valuable comments that helped improve the quality of the manuscript. We addressed all issues indicated in the review report and highlighted all changes in the revised version of the manuscript.

On behalf of the co-authors, I would like to present a detailed list of changes against each comment raised by Reviewers. All changes are highlighted in the uploaded revised version of the paper.

A detailed response to Reviewer’s comments

Line 1: What is the novelty of this work?

Answer: Scientific novelty:

Produced SRF from LMRs conforms to fuel obtained from a combustible fraction of MSW by fuel characteristics; there was substantiated environmental and economic effectiveness use of SRF in the cement industry.

Line 2. Title is too long, reduce it to 20 words.

Answer: The title of the manuscript has been shortened to 20 words (Line 2‒4)

Line 5. The work should include costing as well. This is meaningless otherwise

Answer: The calculation results (Table 5) about feasibility of using SRF in the cement industry as replacement fuel from economic and ecological aspects you can find in the additional file "Calculation economic efficiency of using the SRF" (Line 618‒623, 663‒670).

More important results of this calculation are outlined in the discussions and conclusions sections.

Line 33. Improve the background of research work

Answer: To tried maximum improved the background of research work according to the recommendations https://blog.mdpi.com/2021/02/24/improve-your-research-paper/ (it was re-write Abstract, Introduction, checked for plagiarism etc.)

Line 44. Justify the current research work.

Answer: Have been made changes to the introduction (Line 36‒105).

Line 87. Do not jump the gun (to do something too soon, especially without thinking carefully about it).

Answer: Why not? In the pictures below, you can see the stages of our research at the landfill and the RDF that we obtained after twice sieving (first on the territory landfill, second ‒ at the MBT plant)

Line 99. Add a section on detailed literature review.

Answer: Some scientific journals have a Literature review section in their content. There is no such section in the Sustainability journal in the instructions for the authors. The authors decided not to violate the manuscript rules for submission to the journal.

Line 110. Discuss sampling in detail, location, number of samples and theory.

Answer: We used Standard Test Method for the Determination of the Composition of Unprocessed Municipal Solid Waste (ASTM 113 D5231-92(2016). In order not to burden the manuscript with unnecessary text, a link to the resource is provided in work. In the manuscript's text, the authors added a Figure with the landfill's location and its Sections. Also added coordinates of each section (Line 110‒119).

Line 111. By hand?

Answer: Yes, we did it by hand. We've taken manual sorting at the territory landfill to determine the granulometric and morphological characteristics LMRs.

Line 125. Before testing the sample should have been crushed and mixed and then testing sample should have been prepared. This is because the sample is heterogeneous and fluctuations may be there in drilled samples.

Answer: You are absolutely right.

Thanks to your remark, I added the missing information to the manuscript's text for a more accurate understanding of the research process (Line 139‒141).

Line 161. Why text size is reduced?

Answer: I'm so sorry. This happened, most likely due to font inconsistencies. All document was formatted in the necessary format according to the guidelines for the author.

Line 194. Relate your results with existing literature.

Answer: According to your recommendation, the results of our research were related to the existing literature (Line 207‒480)

Line 201. The figure shows that on average 80% material will be backfilled. Mining costs will be huge, why don’t you consider processing waste well?

Answer: The landfill itself consists of three sections. The oldest Section I was decommissioned and reclaimed; the Newest Section II is in operation. Section II has five new sections for waste disposal, separated from each other by barriers 2.4 m high. Section III is reclaimed and has a separate site for the disposal of asbestos-containing waste with an area of 0.25 ha.

Since 2015, MBT plants have been operating in Lithuania, where the biological fraction, metals (non-ferrous and ferrous) are extracted, and waste is sorted into plastics (soft and hard), paper and mixed (tetra pack, textiles, etc.). After MBT, waste that can be recycled is sent to enterprises for recycling, and the fraction of MSW that cannot be recycled or reused is sent for incineration at the cogeneration power plant (CPP). In Kaunas, CPP started its work in 2020. Until 2015, before commissioning the MBT plants, almost all waste was taken to the landfill. Today, bottom ash that generates after the firing of the non-recyclable waste fraction is sent to the landfill.  Before sending to the landfill from bottom ash extract valuable metals and minerals. The ash is used as a material for dumping waste.

Our main task was to explore the possibility of extracting waste from the landfill, which had once been taken out for disposal. Figure 1 shows the results of studies on all three sections of the test site at different depths. As a result of the research, we recommended excavating waste from the landfill to a depth of 10 m. If we consider waste at a depth of up to 10 m as a potential component, then up to 60% of combustible materials can be excavated from the landfill. By extracting waste from the landfill, we will ensure the uninterrupted operation of the CPP, minimize the use of natural energy resources and thereby reduce greenhouse gas emissions.

In the pictures below, you can see differences between fuel from LMRs in different depths deeper than 10 m. Also presented photo fuel from LMRs from 1 to 10 m. It is our research without any theoretical hypotheses.

Line 205. Values are not acceptable… its not like some 10% mineral that is being mined.

Answer: Updated information on the percentage composition of a particular faction has been added to the manuscript.

A total fraction of more than 20 mm for Section I was in the range of 3 to 47% depending on depth. The minimum amount of coarse fraction and the predominance of fine fraction in this Section refer to the upper layer of the landfill and is explained by the fact that this Section of the landfill is reclaimed.

Line 252. Its better to report quantities recovered per ton of landfill mined.

Answer: At this stage of research (during the research conducted at the landfill), the customer set the task of obtaining information on the composition of landfill waste in %. Therefore, in the work, all data on the waste composition are presented in%. According to the authors, the presentation of the available information in such units of measurement more clearly and understandably presents a picture of the state of waste located at the landfill.

Line 283. Add a list of tables.

Answer: All acronyms were defined the first time they appeared in the text and also can be found in the “Abbreviations” before “References” (Line 687‒703).

Line 309. Fix formatting of the paper.

Answer: All document was formatted in the necessary format according to the guidelines for the author.

Line 343. Its good.

Answer: Yes.

Line 383. Is this proposed method from the current work?

Answer: Yes, we propose using the mechanism we developed for extracting waste from the landfill and, subsequently, the production of SRF.

Line 431. How many times the test is repeated?

Answer: The scanning of every sample during element analysis was repeated three times to gather reasonably good results (Line 166).

Line 567. Why ICP-OES is not used in this work?

Answer: The quantity element analysis of LMRs was performed using an ICP-OES, Optima 8000 (Perkin Elmer). (Line 160‒167).

Line 611. Discuss recommendation and future work.

Answer: In the text of the manuscript were added recommendations for future work. (Line 635‒640)

The text of the manuscript has been checked for spelling.

Author Response File: Author Response.docx

Reviewer 3 Report

I suggest the manuscript will be published without revision.

Author Response

Subject: Revision of manuscript Sustainability-2210633

Reviewer #3

Dear Reviewer,

The authors are grateful to you for the time and effort in reviewing the manuscript and the opportunity to publish the results of our research.

Author Response File: Author Response.docx

Reviewer 4 Report

This study attempted to assess the feasibility of extracting and recovering energy-intensive raw materials from landfills by developing a waste extraction mechanism and creating an solid recovered fuel production line for using it as a replacement fuel in the cement industry. 

The study is interesting but the structure, format and other issues need to be greatly improved in order to be considered for publication:

-Acronyms included in the abstract must be defined the first time they are named.

- All acronyms must be defined the first time they appear in the text.

- Different fonts appear and the formatting does not comply with the journal's author guidelines.

- The introduction is very poor and should be expanded to include a thorough analysis of the state of the art on obtaining fuel from landfill waste or other construction waste. It would also be advisable to make a bibliographic review of the advances being made on the use of construction waste for energy purposes in general.

- The methodology is complicated to understand and it would be advisable to include a diagram with all the steps followed for the production of fuel from waste.

- In the discussion section, the authors should highlight the advantages of the fuel obtained compared to fuels obtained in other studies using other types of waste, such as food waste, plastics, etc. In the discussion section it is important to discuss and highlight the results obtained compared to other studies with similar characteristics and not to limit the presentation to experimental results only.

Author Response

Subject: Revision of manuscript Sustainability-2210633

Reviewer #4

Dear Reviewer,

The authors are grateful to you for the time and effort in reviewing the manuscript and the valuable comments that helped improve the quality of the manuscript. We addressed all issues indicated in the review report and highlighted all changes in the revised version of the manuscript.

On behalf of the co-authors, I would like to present a detailed list of changes against each comment raised by Reviewers. All changes are highlighted in the uploaded revised version of the paper.

A detailed response to Reviewer’s comments

1) Acronyms included in the abstract must be defined the first time they are named.

Answer: Acronyms included in the abstract were defined the first time they were named (Line: 15, 19, 22, 24, 47, 83, 173, 177 and other).

2) All acronyms must be defined the first time they appear in the text.

Answer: All acronyms were defined the first time they appeared in the text and also can be found in the “Abbreviations” before “References” (Line 687‒703).

3) Different fonts appear and the formatting does not comply with the journal's author guidelines.

Answer: All document was formatted in the necessary format according to the guidelines for the author.

4) The introduction is very poor and should be expanded to include a thorough analysis of state of the art on obtaining fuel from a landfill or other construction waste. It would also be advisable to make a bibliographic review of the advances in using construction waste for energy purposes.

Answer: The introduction has been rewritten to reflect the reviewer's recommendations (Line: 36‒105).

5) The methodology is complicated to understand, and it would be advisable to include a diagram with all the steps followed to produce fuel from waste.

Answer: We used Standard Test Method for the Determination of the Composition of Unprocessed Municipal Solid Waste (ASTM 113 D5231-92(2016). To avoid burdening the manuscript with unnecessary text, a link to the resource is provided in the work.

For a more detailed presentation of the entire process of conducting research, a diagram with a detailed description is given below.

6) In the discussion section, the authors should highlight the advantages of the fuel obtained compared to fuels obtained in other studies using other types of waste, such as food waste, plastics, etc. In the discussion section, it is important to discuss and highlight the results obtained compared to other studies with similar characteristics and not to limit the presentation to experimental results only.

Answer: In the discussion section, the results obtained were compared to other studies. The discussion section was changed/rewritten/added based on the comments of reviewers (482-640).

The text of the manuscript has been checked for spelling.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The draft has been significantly improved, however, some more things are required. The most important thing is the novelty or research contribution part. Discuss it in detail. The authors should proof read the paper to remove minor mistakes as well.

Author Response

Subject: Revision of manuscript Sustainability-2210633

Reviewer #2

Dear Reviewer,

The authors are grateful to you for the time and effort in reviewing the manuscript and the valuable comments that helped improve the quality of the manuscript. We addressed all issues indicated in the review report and highlighted all changes in the revised version of the manuscript.

On behalf of the co-authors, I would like to present a detailed list of changes against each comment raised by Reviewers. All changes are highlighted in the uploaded revised version of the paper.

A detailed response to Reviewer’s comments

Comments: The most important thing is the novelty or research contribution part. Discuss it in detail. The authors should proof read the paper to remove minor mistakes as well.

Answer: The authors have proofread the paper to remove minor mistakes, especially:

Line: 44-46; 57-59; 109-110; 114; 138-139; 170; 269; 271; 280; 293-298; 305-306; 309-310; 320-323; 333; 339-340; 363; 386; 398-399; 407; 409-411; 413; and Conclusions 642-669.

Line: 706-886. The stage "Reference" was checked, added missing information (DOI, etc.).

Answer: The manuscript's text has been checked for spelling using the Grammarly Premium program.

Author Response File: Author Response.docx

Reviewer 4 Report

The authors made all required changes.

Author Response

Subject: Revision of manuscript Sustainability-2210633

Reviewer #4

Dear Reviewer,

The authors are grateful to you for the time and effort in reviewing the manuscript and the opportunity to publish the results of our research.

Author Response File: Author Response.docx

Round 3

Reviewer 4 Report

The authors made all required changes.

Author Response

Subject: Revision of manuscript Sustainability-2210633

Reviewer #4

Dear Reviewer,

The authors are grateful to you for the time and effort in reviewing the manuscript and the opportunity to publish the results of our research.

Author Response File: Author Response.docx