Deploying Municipal Solid Waste Management 3R-WTE Framework in Saudi Arabia: Challenges and Future
Round 1
Reviewer 1 Report
It would have been advantageous to have some pcitographical representation of the study based on the results and their weightage.
Author Response
Dear Editor and Reviewers,
We would like to express our sincere gratitude for your valuable comments, which helped to
significantly improve the quality of this manuscript. This major revision of the paper fully takes
into consideration all of your reviewers’ valuable comments. The revised sections in the manuscript are highlighted in yellow. Similarly, please find below the detailed replies to these
comments and description of the revisions made for each comment, all highlighted in yellow.
Reviewer 1 comments
Reviewer comment #1:
It would have been advantageous to have some pcitographical representation of the study based on the results and their weightage.
We would like to thank the reviewer for this valuable comment. Three pictures have been added to represent the study (Figures 6-8).
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear authors,
I find the research interesting with potential perspective in the WtE sector future applications if more concrete data are provided. However, I suggest considering the new trend with respect to the 4R dimensions (reduce, reuse, recycle, recover). From my point of view if you use the 4R by replacing the 3R concept (starting from the manuscript title) it will add value to the research. It is worth mentioning that the 4R framework is at the core of the European Union (EU) Waste Framework Directive [Conceptualizing the circular economy: An analysis of 114 definitions. Resources, conservation and recycling, 2017, 127: 221-232]. Another argument is based on the definitions. It is clear also in the manuscript that by referring to the 3R – the last R represents- ‘’recycling involves an initial stage at which the waste is segregated into recyclable and non-recyclable contents’’. Therefore the RECOVERY is not mentioned, being an essential word given the fact that your research explores the ‘’energy production in the eastern province in Saudi Arabia under two scenarios (complete mass-burn with and without recycling)’’.
- Lines 50-94: I suggest considering the results obtained in Modalities for conversion of waste to energy—Challenges and perspectives. Science of The Total Environment, 138610; Maintenance strategies and local impact of MSW incinerators. WIT Transactions on Ecology and the Environment, 176, 3-13. Pyrolysis is another type of treatment if the selective collection index is high.
- Line 77-79: It will be useful to mention also about SRF ( Energy recovery from Municipal Solid Waste in EU: proposals to assess the management performance under a circular economy perspective. In MATEC Web of Conferences (Vol. 121, p. 05006). EDP Sciences;)
- Line 137: The application of a CE model (considering Romania and Bolivia case studies) could be found also in -Introduction of the circular economy within developing regions: A comparative analysis of advantages and opportunities for waste valorization. Journal of environmental management, 230, 366-378
- Table 1. Please explain the Tables' contents before their display in the manuscript. What is the difference between kWh/kg in material, kW h/kg in waste HHV, Energy content (Btu/lb)? I recommend using one type of unit measure it will be easier to compare the data.
- Table 1. Total energy for mass burn with recycling scenario (kW h/kg)- 0.377 Btu/lb. How these values were calculated? What is the separate collection rate? What is the separate collection quality index? What types of materials are considered in this scenario?
- Line 269. A small mistype error – ‘’mass-burn’’
- Explain the acronyms as their first appearance in the text Energy recovery potential(ERP)
- Section 3.1. Overall comment. Please explain how you have reached to the values depicted in figure 7.? I find mandatory answering to the question that I have highlighted in comment no. 5
- Section 3.2. Here you have described the general situation with the MSW management in the area studied, along with future recommendations. Please provide concrete data. For example sub-section 3.2.2.7 Reuse of discarded wood. What the initial load of wood waste? What is the separated collection rate? How much material costs were reduced?. Same for the other sub-sections presented in section 3.2
Best regards,
Author Response
Dear Editor and Reviewers,
We would like to express our sincere gratitude for your valuable comments, which helped to
significantly improve the quality of this manuscript. This major revision of the paper fully takes
into consideration all of your reviewers’ valuable comments. The revised sections in the manuscript are highlighted in yellow. Similarly, please find below the detailed replies to these
comments and description of the revisions made for each comment, all highlighted in yellow.
Reviewer 2 comments
Reviewer comment #1:
Dear authors,
I find the research interesting with potential perspective in the WtE sector future applications if more concrete data are provided. However, I suggest considering the new trend with respect to the 4R dimensions (reduce, reuse, recycle, recover). From my point of view if you use the 4R by replacing the 3R concept (starting from the manuscript title) it will add value to the research. It is worth mentioning that the 4R framework is at the core of the European Union (EU) Waste Framework Directive [Conceptualizing the circular economy: An analysis of 114 definitions. Resources, conservation and recycling, 2017, 127: 221-232].
Another argument is based on the definitions. It is clear also in the manuscript that by referring to the 3R – the last R represents- ‘’recycling involves an initial stage at which the waste is segregated into recyclable and non-recyclable contents’’. Therefore the RECOVERY is not mentioned, being an essential word given the fact that your research explores the ‘’energy production in the eastern province in Saudi Arabia under two scenarios (complete mass-burn with and without recycling)’’.
We would like to acknowledge this valuable comment. We totally agree on the fact that the 4R is highly overlapping with our 3R-WTE framework. The difference that distinct the 4R framework from ours is the Recovery stage. In the work of [Conceptualizing the circular economy: An analysis of 114 definitions. Resources, conservation and recycling, 2017, 127: 221-232], which we cited in our revised manuscript, address Recovery in 4R framework (pp 223, Table 2) pertaining only WTE- incineration. As such, we present the 4R framework as “3 R-WTE”. We clarify this point in the Methods section in our revised manuscript.
Below is the added the below paragraph in the Methods section.
“Although many research can be found on combined WTE along with waste mitigation initiatives, Yet less consensus in naming such initiatives is witnessed in the literature as concluded by Kirchherr. Perhaps the use of the 4R framework (Reduce, Reuse, Recycle, Recover) which is at the core of the European Union (EU) Waste Framework Directive (European Commission, 2008) is the most reliable definition of the combined WTE residential waste mitigation frameworks. In our work, we adopt almost a similar definition to the 4,R however, we distinct our proposed combined WTE waste mitigation framework in the Recovery stage. In the work of [Conceptualizing the circular economy: An analysis of 114 definitions. Resources, conservation and recycling, 2017, 127: 221-232], address Recovery in 4R framework (pp 223, Table 2) pertained only to WTE- incineration. Therefore the “recover” is not mentioned, being an essential word given the fact that your research explores the ‘’energy production in the eastern province in Saudi Arabia under two scenarios (complete mass-burn with and without recycling)’’. As such, we present the 4R framework as “3 R-WTE”.”
- Lines 50-94: I suggest considering the results obtained in Modalities for conversion of waste to energy—Challenges and perspectives. Science of The Total Environment, 138610; Maintenance strategies and local impact of MSW incinerators. WIT Transactions on Ecology and the Environment, 176, 3-13. Pyrolysis is another type of treatment if the selective collection index is high.
The two suggested studies have been cited in the manuscript.
- Line 77-79: It will be useful to mention also about SRF ( Energy recovery from Municipal Solid Waste in EU: proposals to assess the management performance under a circular economy perspective. In MATEC Web of Conferences (Vol. 121, p. 05006). EDP Sciences;).
We have mentioned about the solid recovered fuel (SRF) and cited the proposed paper.
- Line 137: The application of a CE model (considering Romania and Bolivia case studies) could be found also in -Introduction of the circular economy within developing regions: A comparative analysis of advantages and opportunities for waste valorization. Journal of environmental management, 230, 366-378.
The suggested paper have been cited in the revised manuscript.
- Table 1. Please explain the Tables' contents before their display in the manuscript. What is the difference between kWh/kg in material, kW h/kg in waste HHV, Energy content (Btu/lb)? I recommend using one type of unit measure it will be easier to compare the data.
In the manuscript, we have explained the Tables 1 contents before its display. The difference between kWh/kg in material and kW h/kg in waste has been explained in the manuscript and highlighted in yellow. In addition, all units measure have been unified.
- Table 1. Total energy for mass burn with recycling scenario (kW h/kg)- 0.377 Btu/lb. How these values were calculated? What is the separate collection rate? What is the separate collection quality index? What types of materials are considered in this scenario?
Total energy for mass burn with recycling scenario is calculated as the summation of the LHV column values after removing of all potentially recyclable products (paper, plastics, glass, wood, and textile) from the waste before combustion.
In this manuscript, we assume that all recyclable products will be 100% recycled and we assumed all recyclable products are pure with good quality. Therefore, the separate collection quality index is assumed to be 100%. However, in Saudi Arabia, the recycling rate is very low (10%-15% of total waste) and recycling activities are mostly manual and labor intensive. Saudi Arabia in it Vision2030 is planning to achieve a recycling rate of 40%.
The following note is attached to Table 1.
** The values assume the separate collection rate and separate collection quality index to be 100 %
- Line 269. A small mistype error – ‘’mass-burn’’
Thank you for addressing this mistype error which we rectified in our revised submission.
- Explain the acronyms as their first appearance in the text Energy recovery potential(ERP)
All acronyms, including ERP, have been explained before being used in the whole manuscript.
- Section 3.1. Overall comment. Please explain how you have reached to the values depicted in figure 7.? I find mandatory answering to the question that I have highlighted in comment no. 5
To reach the values, the following steps are followed:
- The total energy for WTE scenario (LHV) is used along with the daily dry waste generated by the Eastern Province to compute the Energy Recovery Potential (ERP) in (GWh/day) using the following equation:
Energy Recovery Potential (ERP) =(dry waste(tons/day)X LHV(kwh/kg))/1000,
- The net generated power in MW is calculated using:
NGP = ɳ * ERP *
For example, for Year 2010, Complete mass-burn:
- Daily waste generated = population size * average daily waste generated (kg/capita)= 4,130,033*1.4/1000 = 5,782.05 tons/day
- ERP =(dry waste(tons/day)X LHV(kwh/kg))/1000= (5,782.05*2.51)/1000 = 52(GWh/day)
- NGP = ɳ * ERP * = 0.25* 14.52*(10^3/24 )=151.25 MW
Where ɳ is the combustion efficiency of 25%.
- Section 3.2. Here you have described the general situation with the MSW management in the area studied, along with future recommendations. Please provide concrete data. For example sub-section 3.2.2.7 Reuse of discarded wood. What the initial load of wood waste? What is the separated collection rate? How much material costs were reduced?. Same for the other sub-sections presented in section 3.2.
More detailed data is provided in each sub-section and linked to the environment in our case study i.e. number of trees that can be saved by implementing the 3R-Wte framework.
Best regards,
Reviewer 3 Report
The paper is interesting due to its informative nature, but it cannot be considered a scientific article, since it is limited to collecting and displaying social, political and environmental data.
As a general comment, the manuscript should be revised to improve the format (separation between words, words and signs, units, etc.)
On the other hand, there are some specific aspects that must be improved:
Abstract, line 25: change kg/head for kg/capita (since in the whole article it is cited like this)
Line 45: I think it is more appropriate cited as: Kaza et al. (2018) [1] stated that...
Line 47 and 50: I think it is more appropriate cited as: Hoornweg et al. (2012) [3] forecasted that...
Line 51: I think it is more appropriate cited as: Vergara and Tchobanoglous (2012) [4] studied...
Line 91: ... waste by 70% to 80% with lower...By weight or by volume?
Line 135: I think it is more appropriate cited as: Hoang et al. (2020) [27] studied...
Figure 2: Please, point to the approximate zone of the residential area in Figure 2
Line 173: is KSA the name of the eastern province?
Line 180: In figure 4 only the percentage of each fraction appears, but not the LHV
Line 196 to 202: Most of this paragraph is copied from previous paragraphs. No need to put it twice above all in the "Results"
Line 239: Table 1 Please, you should specify if these data are on a dry or wet weight
Line 239, Table 1, column kWh/kg in waste HHV: These data seem too low to me. Even if these data are represented on a wet basis (it must be specified) it would suppose a humidity of around 70%, which seems to me too much humidity for these types of waste, especially plastic, textile, etc. Authors should verify it.
Line 288-289: 11,000 inhabitants produce 3,000 tons/day? it seems to me an excessively high generation: 272.7 kg/capita·day ???? I guess it will be 272.7 kg/capita·year
Line 492: the residents living in the camp produce 3,000 tons of MWS per day: change MWS by MSW. The same possible mistake than above: 3,000 tons/capita·day? even if the rate were 3000 t/capita·year, the daily rate would be 0.75 kg/capita·day
It would be desirable for the authors to include some interesting indicator, such as energy consumption per household in summer - winter, how many households would be supplied by the energy from burning waste with / without recycling, etc.
Author Response
Dear Editor and Reviewers,
We would like to express our sincere gratitude for your valuable comments, which helped to
significantly improve the quality of this manuscript. This major revision of the paper fully takes
into consideration all of your reviewers’ valuable comments. The revised sections in the manuscript are highlighted in yellow. Similarly, please find below the detailed replies to these
comments and description of the revisions made for each comment, all highlighted in yellow.
Reviewer 3 comments
Reviewer comment #1:
The paper is interesting due to its informative nature, but it cannot be considered a scientific article, since it is limited to collecting and displaying social, political and environmental data.
We would like to thank the reviewer on this comment. We agree that the research methods relied heavily on collecting and displaying social, political and environmental data. However, we believe that this data is valuable to be collected, processed and declared as distinct framework to promote future initiatives in Saudi Arabia and perhaps in other countries sharing same environment of Saudi Arabia (Rapid growth in waste generation with almost zero attempts toward circular economy). Such sound applicable frameworks is believed to extend the WTE initiatives (combined with waste mitigation) in other provinces in Saudi Arabia through governmental official service entities (With a land area of approximately 2,150,000 km2).
As a general comment, the manuscript should be revised to improve the format (separation between words, words and signs, units, etc.)
We would like to thank the reviewer for this comment. We tried to our best to amend this comment in the revised manuscript.
On the other hand, there are some specific aspects that must be improved:
Abstract, line 25: change kg/head for kg/capita (since in the whole article it is cited like this)
The “kg/head” has been replaced with “kg/capita” in the whole manuscript.
Line 45: I think it is more appropriate cited as: Kaza et al. (2018) [1] stated that...
The citation has been modified in the manuscript.
Line 47 and 50: I think it is more appropriate cited as: Hoornweg et al. (2012) [3] forecasted that...
The citation has been modified in the manuscript.
Line 51: I think it is more appropriate cited as: Vergara and Tchobanoglous (2012) [4] studied...
The citation has been modified in the manuscript.
Line 91: ... waste by 70% to 80% with lower...By weight or by volume?
Thank you for addressing this mistype error which we rectified in our revised submission.
The sentence has been revised as “has the advantage of reducing waste by 80% and mass by 70% and relatively lower cost in comparison to other technologies [27]”.
Line 135: I think it is more appropriate cited as: Hoang et al. (2020) [27] studied...
The citation has been modified in the manuscript.
Figure 2: Please, point to the approximate zone of the residential area in Figure 2
We point out to the approximate zone of the residential area in figure 2. We revised figure 2 to zoom in the residential area studied.
Line 173: is KSA the name of the eastern province?
KSA is abbreviation of Kingdom of Saudi Arabia. However, the “KSA” is replaced by Saudi Arabia in the whole manuscript.
Line 180: In figure 4 only the percentage of each fraction appears, but not the LHV
Figure 4 has been removed from the manuscript and the materials compositions have been added to Table 1 as a column.
Line 196 to 202: Most of this paragraph is copied from previous paragraphs. No need to put it twice above all in the "Results"
Thank you for drawing our attention to this point. The paragraph in the Result section have been modified.
Line 239: Table 1 Please, you should specify if these data are on a dry or wet weight
The data are on dry weight. Initially the data were provided in HHV and after reviewing different studies, we found that the numbers are in LHV. We have revised the values to the low heating value (LHV) in the updated submission in Table 1 which cites four references.
Line 239, Table 1, column kWh/kg in waste HHV: These data seem too low to me. Even if these data are represented on a wet basis (it must be specified) it would suppose a humidity of around 70%, which seems to me too much humidity for these types of waste, especially plastic, textile, etc. Authors should verify it.
Thank you for bringing this valuable point as surely humidity plays a key role in determining the energy potential from waste. We have revised the values to the low heating value (LHV) in the updated submission in Table 1 which cites following references, namely:
- Khan, M.S.M.; Kaneesamkandi, Z. Biodegradable waste to biogas: renewable energy option for the Kingdom of Saudi Arabia. J. Innov. Appl. Stud 2013, 4, 101–113.
- Ouda, O.K.; Raza, S.A.; Nizami, A.S.; Rehan, M.; Al-Waked, R.; Korres, N.E. Waste to energy potential: a case study of Saudi Arabia. Renewable and Sustainable Energy Reviews 2016, 61, 328–340.
- Ouda, O.K.; Cekirge, H.M.; Raza, S.A. An assessment of the potential contribution from waste-to-energy facilities to electricity demand in Saudi Arabia. Energy Conversion and Management 2013, 75, 402–406.
Line 288-289: 11,000 inhabitants produce 3,000 tons/day? it seems to me an excessively high generation: 272.7 kg/capita·day ???? I guess it will be 272.7 kg/capita·year.
Thank you for addressing this mistype error which we rectified in our revised submission. Actually, the correct number is 3000 tons/year.
Line 492: the residents living in the camp produce 3,000 tons of MWS per day: change MWS by MSW. The same possible mistake than above: 3,000 tons/capita·day? even if the rate were 3000 t/capita·year, the daily rate would be 0.75 kg/capita·day
The abbreviation “MWS” has been replaced by “MSW”. The correct number is 3000 tons/year and the daily rate would be 0.75 kg/capita·day
It would be desirable for the authors to include some interesting indicator, such as energy consumption per household in summer - winter, how many households would be supplied by the energy from burning waste with / without recycling, etc.
Thank you for this suggestion. We have added the following indicators the manuscript which hopefully will be found interesting and beneficial by the readers:
- Energy consumption per household
- Number of households supplied by the energy from burning waste with / without recycling.
- Number of households supplied by the energy generated from the 3000 tons collected by the camp.
- More detailed data is provided and linked to the environment in our case study i.e. number of trees that can be saved by implementing the 3R-Wte framework.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Dear Authors,
Thank you very much for taking the time to improve the manuscript. I recommend it for publication.
Best regards,
