Circularity of Bioenergy Residues: Acidification of Anaerobic Digestate Prior to Addition of Wood Ash
Round 1
Reviewer 1 Report
Sustainability
Circularity of Bioenergy Residues: Acidification of Anaerobic Digestate Prior to Addition of Wood Ash Renewable and Sustainable Energy Reviews
The manuscript is of general interest. However, some major revisions are required. The following comments should help further improve the quality of the work:
1-Abstract should be improved. The main quantitative findings should be included in the Abstract.
2-There are too many keywords; up to six keywords are allowed.
3-Latin words such as via, etc. should be italicized.
4-More attention should be paid to punctuation marks. On many occasions, there are missing.
5-Biomass is an important part of this work and should be more effectively highlighted. In a recent work (A review on biomass: importance, chemistry, classification, and conversion), Tursi has well elaborated on that. Please refer to this work and further enrich the manuscript.
6-Please include a Table of Abbreviations/Nomenclatures.
7-The novelty/originality of the paper should be more effectively established. It would be advisable to add a Table to the “Introduction” section, tabulating the latest research works in the field to highlight the novelty of the present work accordingly.
8-The Introduction is too brief and should be expanded by including the latest research and review works published in this domain to enhance the timeliness of the present manuscript.
9-Latest trends in biogas production should be briefly explained by referring to the latest review articles, including (A comprehensive review on recent biological innovations to improve biogas production, Part 1: Upstream strategies) and (A comprehensive review on recent biological innovations to improve biogas production, part 2: Mainstream and downstream strategies) by Tabatabaei and colleagues.
10-There are unnecessary spaces between numbers and the percentage symbol (%). Please screen though the manuscript and get this fixed where needed.
11-Please combine Tables 1, 2, 3, and 4.
12-Reference lumping should be avoided. Please cite references where they exactly belong; this will prevent reference lumping.
13-All Equations should be properly referred to (mentioned) in the text.
14-In Figures 6, 7, and 10, the panels have been designated using “a” and “b”; so for referring to the other elements in the panels, these letters should not be used. Instead, please use, Arabic numbers (1, 2, 3, etc.) or Latin numbers (i, ii, iii, etc.).
15-Please change "5. Conclusions” to “5. Conclusions and prospects". Accordingly, please elaborate on the future research needs in this domain.
16-The limitations of the study should also be explained.
17-The practical implication of the present study should be included as well.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The aim of this work was the development of novel fertilizer through the acidic treatment of anaerobic digestate followed by addition of wood ashes. The claim of the development of novel fertilizer is not studied in this work at all. The work was focused on the treatment of anaerobic digestate using (sulphuric, hydrochloric, nitric, and lactic acid) in 50 ml centrifugal tube. and measuring the pH and electric conductivity.
- For this type of research complete analysis of feedstock needs to be carried out as well as the resulted proposed product.
- The microbiological part which just writing "lactic acid promoted the growth of filamentous microbes in agrowaste digestate and microbial colonies in the food waste digestate" is very poor and needs support by results which is not there in this work.
- The results related to the effect of treatment on microbial growth is very unclear and not supported by any scientific evidence.
- How this treatment can affect the microbial consortium and count is missing and this part is very important for the discussion of this type of research.
- The results showed that lactic acid did not affect negatively the organic matter of the anaerobic digestates but promoted excessive undesired microbial growth (this was given in the conclusion part which was not proven in this work in good approach). In addition, concluding that sterilization of the anaerobic digestate via poisoning with sodium azide could be performed in future investigation (this approach is not suitable at all as the aim is to develop fertilizer not addition of toxic material to the soil!!!). Sterilization in this process is not suitable at all in any means if authors think about scalability of this process beyond 50 ml centrifuge tube.
Author Response
Please, see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
Review Report
The manuscript entitled “Circularity of Bioenergy Residues: Acidification of Anaerobic Digestate Prior to Addition of Wood Ash” investigates the implications of acid treatment of food waste digestate and post-harvest vegetable waste digestate for effective preparation of soil amendment in combination with woof fly ash. The management of organic waste and transferring this organic waste into valuable nutrient resources is an important aspect for circular economies. The study is interesting and might of good importance for general readers. But there are few minor comments which must be addressed before its acceptance.
- Abstract: Please write complete names of acids instead of their formulas. Give a singleline statement about the objectives of the study.
- Introduction: Objectives of the study are not clear rephrase the line 70-73. Line 76 Write Groundwater instead of underground water
- Add few lines and citations related to the acid treatment and nutrient profiling of organic wastes.
- Material and Methods this sections must be showed materials used for example organic waste sources, Acid sources and how the combinations were prepared but this section for example line 79-94 seems to show findings and process of the combinations which I think must be added in results section. Same is the case with the rest of the section until line 134. This section need to modified as proper material and method section
- Line 145 the word is buffering capacity, Figure 6 to 12 can go to supplementary information, but they bust be added in results section instead of discussion section.
- Conclusion section need a specific statement about the efficacy of various acids in relation to the organic waste treatment.
Author Response
Please, see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript can be accepted for publication.
Reviewer 2 Report
Authors did significant improvement in very good approach. They addressed all comments raised in the first review round.
