Waste to Energy from Municipal Wastewater Treatment Plants: A Science Mapping

Round 1

Reviewer 1 Report

The ms titled Waste to energy from municipal wastewater treatment plants: 2 A science mapping towards a circular economy submitted by Juan Jesús de la Torre Bayo is very interesting. The topic Fit the magazine domain. Some modification is necessary before acceptance for publication.

1.        Line 11-22: Abstract part. Supplementary literature collection period. Supplementary literature collection period

2.        Line 33: “CO2”. Modify subscript

3.        Fig.3: clear two vertical ordinate meaning difference

4.        Fig.4: Make sure the graph is clear by truncating the vertical coordinates of Figure a and b.

5.        The discussion needs to be strengthened, especially with regard to the current problems in the field and the direction of sustainable technology research under the low-carbon goal. Put forward your own ideas and opinions

6.        Line 581-607: Put forward the lack of research, and future research direction

7.        It is proposed that 337 documents be included in the supplementary material

8.        It is recommended that headings be compressed to level 3

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Manuscript ID: sustainability-2072134

The manuscript entitled, “Waste to energy from municipal wastewater treatment plants: A science mapping towards a circular economy” is a good and interesting literature review about waste-to-energy (WtE) technologies related to wastewater treatment plants (WWTPs). Juan Jesús de la Torre Bayo and co-authors nicely review literature WtE research using Science Mapping Analysis Tool (SciMAT) and VosViewer. Although work is transparent and can be published but I had selected major revision to enhance the novelty and better readership. I believe it will not take a long for the authors to work on this revision. My comments are,

 

1.      Revise this sentence, “Besides, WWTPs are also a rich source of organic matter and, thus, of chemical energy [8] that is about 9.3 times higher than the energy necessary to purify it [9]”

2.       Fig.1 &2 are not readable, provide clear one

3.      In introduction add few line about the importance of safe drinking water suggested to cite, https://doi.org/10.1080/03067319.2020.1846732. Surfaces and Interfaces 34 (2022) 102324

4.      It is more appropriate to provide colour Figures.

5.      Authors should clearly presents the novelty of this article

6.      The whole manuscript must be cross-checked thoroughly for English editing, grammatical, spelling mistakes, and syntax errors.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The methods and graphs are interesting however the conclusions and some comments are weak.

The proposed title „Waste to energy from municipal wastewater treatment plants: A science mapping towards a circular economy” is not clear and not in line with aim of the study there is nothing about circular economy in the chosen keywords. Therefore abstract is worth changing as well as the comments about the circular economy – focusing only on energy recovery is not sufficient for CE – there are a lot of papers dealing with the recovery of phosphorous and other valuable materials from waste sludge.

 

With the sentences - A significant increase in the number of documents was observed in comparison with the previous phase and coincided with the approval of the Directive 2008/98/EC on waste – could you specify papers from EU authors – if it had been correlated. The same about 3rd subperiod – after the adoption of the first EU action plan for the circular economy – the increase has been in Europe mostly.  It seems not to be confirmed in further part of the study as most papers are outside of EU.

Figure 4. Relationship between the number of documents and (a) the number of sources, (b) authors, and (c) countries. – it is unclear what country – not sufficiently described

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Accept in present form

Reviewer 3 Report

I accept as it is