Properties of RDF after Prolonged Storage

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Abstract

·       The abstract mentions the analysis of RDF properties but lacks specifics about the methods. Including a brief mention of the critical analytical techniques would provide better insight into the research approach.

·       While the abstract summarizes the findings, it could be enhanced by briefly highlighting the most significant results, especially those that are unexpected or counterintuitive.

·       The abstract should articulate the study's significance more strongly. A sentence on how this research contributes to the field of waste management or informs RDF usage practices would be valuable.

·       Incorporate distinct keywords for better indexing and searchability, avoiding those already in the title.

1. Introduction

·       The introduction effectively highlights global waste generation issues. It could be further strengthened by providing specific statistics or trends to showcase the increasing challenge of waste management.

·       The discussion on sustainable disposal methods is informative. Exploring alternative methods besides RDF and their comparative advantages or limitations would provide a more comprehensive perspective.

·       The manuscript addresses RDF heterogeneity. Expanding on how this heterogeneity impacts RDF processing and utilization in real-world scenarios would be beneficial.

·       The manuscript touches on RDF storage and homogenization. A more detailed discussion of different storage methods and their impact on RDF quality would be valuable.

·       The rationale for the study is clear. However, explicitly linking the research objectives to addressing specific gaps in current RDF practices could strengthen the justification.

·       Once you've introduced an abbreviation, stick with that abbreviation throughout the manuscript to avoid

·       The research objectives are somewhat implicit. Making them explicit would help readers quickly grasp the main focus of the study.

·       While the introduction addresses RDF in the EU context, briefly mentioning its global relevance would broaden the scope and appeal of the study.

·       Maintain consistency in terminology; choose either RDF or SRF and use it exclusively to prevent confusion.

2. Materials and Methods

·       Please specify the age of the RDF samples used in your study.

·       Discuss any potential sampling biases and how they were mitigated.

·       The description of the RDF pile, including its composition, is comprehensive. A suggestion would be to provide a visual representation, such as a photograph or schematic, to help readers visualize the pile and the sampling process.

·       The sampling method is well-described. However, including a justification for the chosen depths and their potential impact on the study’s outcomes would be beneficial.

·       The approach to measuring bulk density is detailed. A suggestion for improvement is to elaborate on how this measurement relates to RDF's handling and storage characteristics.

·       The method for measuring water content is standard. Clarifying the potential impact of varying water content on RDF quality and combustion efficiency would add value.

·       The procedure for determining ash content is well explained. It would be useful to discuss the significance of ash content in RDF, especially concerning its use as a fuel.

·       The measurement of pellet expansion is an interesting inclusion. Expanding on the relevance of this measure in terms of RDF storage and handling could provide a clearer understanding of its importance.

·       The manuscript describes outdoor storage conditions. Discussing how varying environmental conditions might have impacted the results would add depth to the analysis.

·       Discussing any limitations or potential sources of error in the methods used and how these might impact the interpretation of results would provide a more balanced view.

3. Results and 4. Discussion

Particle Size Distribution

·       If possible, compare these findings with other RDF particle size distribution studies. This would help contextualize your results within the broader field.

·       The manuscript mentions outdoor storage. Delving deeper into how environmental factors like weather conditions might have affected particle size distribution would provide a more comprehensive understanding.

·       If applicable, compare your findings with industry standards for RDF particle size distribution to gauge the quality and applicability of the RDF produced.

·       Discuss the implications of the observed particle size distribution on the handling and processing of RDF, including any challenges or advantages it presents.

·       Suggest areas for further research based on the findings, such as exploring the impact of different storage conditions on particle size distribution.

Bulk density

·       The manuscript mentions outdoor storage. Discussing how varying environmental conditions might have affected the bulk density of the RDF would add depth to the analysis.

·       Discuss how the observed bulk density values might impact RDF's handling, storage, and processing efficiency. This could include implications for transportation and combustion efficiency.

·       Delve deeper into how environmental factors like weather conditions might have affected bulk density, providing a more comprehensive understanding.

·       Explore whether and how the duration of storage impacts bulk density, providing insights into optimal storage conditions for RDF.

·       Discuss the implications of the observed bulk density on the handling and processing of RDF, including any challenges or advantages it presents.

Water content

·       Discuss the implications of the measured water content levels on RDF’s quality, specifically, how moisture affects RDF’s calorific value, combustion efficiency, and handling during processing.

·       Comparing the observed water content values with industry standards or typical values for RDF can provide context and help assess the quality of the RDF studied.

·       Explore how environmental factors, such as humidity or rainfall, might have affected the water content. This would add depth to the understanding of RDF storage conditions.

·       Discuss the findings' practical implications regarding RDF processing, storage, and utilization—for example, the need for drying processes or the impact on storage conditions.

·       Analyze whether and how the duration of storage impacts water content. Insights into how long-term storage affects RDF moisture levels would be valuable.

·       Propose areas for further research based on the findings, such as exploring the impact of different storage methods on water content.

·       Detail the environmental conditions (like weather) during sampling, as this can provide context for the water content results.

Ash content

·       Comparing the ash content values with typical or standard values in RDF literature would provide useful context and help assess the RDF quality.

·       Discuss the practical implications of the findings regarding RDF processing and storage. For instance, how does ash content impact the combustion process?

Heat of Combustion

·       Comparing the measured heat of combustion values with typical or standard values in RDF literature would provide useful context and help assess the RDF quality.

·       Discuss the potential reasons for any observed variability in the heat of combustion values among different fractions, considering factors like particle size and moisture content.

·       Investigate any correlations between the heat of combustion and other properties like ash content, water content, or particle size.

·       Analyze whether and how the duration of storage impacts the heat of combustion, providing insights into how storage conditions affect RDF quality.

·       Propose areas for further research based on the findings, such as exploring the impact of different storage methods on the heat of combustion.

Mechanical Properties and Expansion Coefficient

·       Results regarding pellet expansion are presented. A more in-depth analysis of what these expansion rates imply about the RDF's physical characteristics would be beneficial.

·       The manuscript discusses the expansion coefficient, but a deeper explanation of how this property affects the RDF's quality, particularly in terms of its handling and storage, would be valuable.

·       If there are industry standards for pellet expansion in RDF, comparing your results with these standards would contextualize the findings.

·       Discuss how the process of pellet formation, including pressure and material composition, may have influenced the mechanical properties and expansion coefficient.

·       Explore correlations between mechanical properties, expansion coefficient, and other measured properties like moisture or ash content.

·       For Figures 1-3, please explain what the three colored lines mean.

5. Conclusions

·       The conclusion that long-term open-air storage has no notable negative effect on RDF quality is significant. Elaborating on the environmental implications of these findings, such as the impact on greenhouse gas emissions or leachate production, would provide a more holistic view.

·       While the conclusions address the implications for RDF processing, expanding on specific recommendations for RDF handling, transportation, and combustion based on these findings would be practical for readers.

·       The noted differences in RDF properties between depth fractions are essential. Discussing how this knowledge could inform better segregation or homogenization strategies during RDF processing would be insightful.

·       The conclusion that long-term storage does not necessitate specific procedures for maintaining RDF quality is practical. Discussing the potential cost and operational benefits of this finding for waste management facilities would add depth.

·       Placing these conclusions in the context of sustainable waste management and circular economy principles would enhance the manuscript's relevance to current global challenges.

·       Address the economic implications of long-term RDF storage, including potential cost savings or resource optimization strategies.

·       Acknowledge other study limitations and suggest specific directions for future research to build upon these findings.

Comments on the Quality of English Language

Once you've introduced an abbreviation, stick with that abbreviation throughout the manuscript to avoid redundancy and maintain clarity.

Author Response

Dear Reviewer,

please see the attachment for our reply to your review.

With kindest regards,

the Authors.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Overall, the idea is novel and has importance, but the methods and literature review require improvement. Also, I havent seen a proper analysis or experimental steps.

In current form, paper lacks credibility and acceptance.

Below are the required details: 1. What is the main question addressed by the research? The research aims to provide specific criteria for refuse derived fuel (RDF) for MSW feedstock
2. What parts do you consider original or relevant for the field? What
specific gap in the field does the paper address? The idea is novel, but the manuscript lacks alot of scientific analysis and mostly equations and initial experimental results.
3. What does it add to the subject area compared with other published
material? This idea is novel since it could improve and enhance thermochemical reactions and increase the quality and quantity of final products. 
4. What specific improvements should the authors consider regarding the
methodology? What further controls should be considered? More details including steps and experimental analysis techniques, analytical equipment to be used.
5. Please describe how the conclusions are or are not consistent with the
evidence and arguments presented. Please also indicate if all main questions
posed were addressed and by which specific experiments. The manuscript is primary undergraduate level and lacks comprehensive analysis and analytical equipment to be used
6. Are the references appropriate? YES
7. Please include any additional comments on the tables and figures and
quality of the data. THE MANUSCRIPT lacks scientific analysis, I recommend to authors to read the following manuscripts.    https://www.mdpi.com/2073-4433/14/4/655
https://www.e3s-conferences.org/articles/e3sconf/abs/2020/18/e3sconf_icepp2020_04006/e3sconf_icepp2020_04006.html

 

Comments on the Quality of English Language

Acceptable

Author Response

Dear Reviewer,

please see the attachment for our reply to your review.

With kindest regards,

the Authors.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors, 

The paper assesses the quality of samples of refuse-derived fuel regarding the conditions and duration of its storage. The material from which the samples were derived was drawn from a pile stored outdoors for over three years, fully exposed to weather conditions for the entirety of that time. In my opinion, the article is well-structured and argued. The empirical research is well done and the method is clearly exposed. However, I have a few comments that could help the authors to improve the article. 

1) The introduction does not clearly establish the contribution of the article to the literature, maybe the authors considered that there were some innovations in the methods used, in data for the geographical region where the experiment was conducted, or in the practical implications of the research. I would suggest stating this point explicitly in the introduction. 

2) In my opinion, the discussion is not well-referenced and contextualized with respect to previous work. The results of the article are only discussed with respect to two previous articles [4] and [12] and one of them is personal communication. I would suggest improving the discussion contextualizing the results in a broader stream of previous literature. 

3) In the discussion or conclusion, I miss a broader discussion of the practical implications of the findings. I would suggest adding a discussion, for example, about what the implications of the findings are for the design of public policies related to municipal solid waste or for private energy companies. 

I hope my comments could help the authors to improve the manuscript. 

Kind regards, 

Reviewer.

Author Response

Dear Reviewer,

please see the attachment for our reply to your review.

With kindest regards,

the Authors.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Stellar work on the revisions. Every concern has been squared away. Your manuscript's now tougher, thanks to your diligence.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript is acceptable stating relevant technologies to RDF

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors, 

In my opinion, the authors have succesfully incorporated the comments made in the first round, especially in the introduction and discussion section. I only have one minor comment, the numerical correlation of references in the main text starts from 1 to 30 and in the references section from 0 to 29, which makes it confusing to check the references.

Congratulations for the work done. 

Kind regards, 

Reviewer.