Effects of Different Materials on Biogas Production during Anaerobic Digestion of Food Waste

Round 1

Reviewer 1 Report

Comments for author File: Comments.pdf

Author Response

We would like thank the reviewers for their thoughtful comments. We have revised the manuscript based on this feedback. Please see attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The Manuscript ID: sustainability-2177214 “Effects of different materials on biogas production during anaerobic digestion of food waste” requires revision before accepted for publication. The specific comments are given below.

1.     In the abstract, present the most important numerical results.

2.     The "Introduction" section should follow the state of the art of this field and review what has been done, for supporting the research gap and the significance of this study. Please improve the state of the art overview, to clearly show the progress beyond the state of the art.

3.     In the last paragraph of the introduction, clearly indicate the research hypothesis.

4.     Provide significant words which are more relevant to the work in a logical sequence as ‘keywords’.

5.     Ln 124 Please provide more information like OLR, HRT, average flow for the sewage treatment facility (STP) of the city of Heraklion, Greece

6.     How much inoculum and FW were introduced? Tell us what the OLR and HRT was - it's very important!

7.     Please indicate the manufacturer, city, country when mentioning the equipment.

8.     Compare your results with those of other authors who have used FW blends. Indicate what percentage of food waste they used.

https://doi.org/10.1016/j.biombioe.2020.105913

https://doi.org/10.1016/j.wasman.2021.04.023

https://doi.org/10.3389/fmicb.2020.581997

9.     I am asking you to perform an energetic analysis in order to assess the legitimacy.

10.  It is also recommended to discuss and explain what should be the appropriate policies based on the findings of this study.

11.  Review the latest research from 2019 - 2023. Refresh the literature.

Author Response

We would like thank the reviewers for their thoughtful comments. We have revised the manuscript based on this feedback. Please see attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

This manuscript investigated the biogas output improvement after adding some additives during the biogas fermentation of food waste. The improvement of cumulative biogas production, VS and COD reduction were provided.

1.       Line 35-38, Line 75-84. There were a lot of conceptual introductions which was needless.

2.       There are a lot of parameters to evaluated performance of anaerobic digestion liquid system besides the biogas production, VS and COD reduction. This study only tested the three (biogas output, VS, COD) parameters, which is not enough to explain the reason of the improvement after adding the additives in the biogas fermentation system.

3.       The article is not sufficiently discussed.

Author Response

We would like thank the reviewers for their thoughtful comments. We have revised the manuscript based on this feedback. Please see attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

The article by I.D. Papastefanakis et al is devoted to the study of the effect of various nano-materials on biogas production during the anaerobic decomposition of food waste.

the article corresponds to the profile of the journal. But before considering it further, the authors should make some additions and corrections.

Lines 12-13. It is written that “The types of feedstocks and microorganisms used in the AD process have an impact on the efficiency of the process” Since the authors did not compare either the influence of the substrate or microorganisms on the degradation process, this sentence in the Abstract seems redundant.

Line 23. Perhaps it would be more correct to write that “The addition of ZnO/Ag and TiO2 improved the biogas cumulative yield by 12 and 44%, resp…”, as the authors compared the process in three conditions (control and two experiments) with respect to the end point.

Line 56. Latin name should be in italic.

Section 2.1. Raw materials. …

How many times did the authors run the experiment? Waste composition was defined as vegetables-bread-cooked food. Isn't the bread ready? How stable is the composition of the waste over the seasons? What results of the experiment can be expected if the waste is collected on another day?

Section 2.2.

How was the concentration of Ti solution?

Line 131. The solution was heated for 24 and 48 h. In what case for what?

Line 127 and Line 139 – both sections are under number 2.2

Section Biogas-methane experiment is described not enough. The Botle was 120 ml. How much FW was add in each case? In the case, line 141 ZnO/Ag and TiO2 – what was substrate for microbial growth? And where are results for that?

Line 151. The mention of pH meter can be omitted.

Lines 238-239 The sentence “The chemical oxygen demand decrease (%) 238

was computed as (TCODin - TCODout / TCODin) x 100, where TCODin and TCODout are the concentrations of feed and digested substrate, respectively.” Is a method and should be transferred in MM part.

Author Response

We would like thank the reviewers for their thoughtful comments. We have revised the manuscript based on this feedback. Please see attachment.

Author Response File: Author Response.pdf

Reviewer 5 Report

This paper demonstrating the effect of inorganic additives like micronutrients  on the efficiency of biogas producing reactors. The main focus of the paper is the investigation of  the existence of TiO2 and ZnO/Ag powders on anaerobic digestion. The results shows that the addition of ZnO/Ag and TiO2 improved the biogas cumulative yield by 12-44%,which represents a significant increase.

The article is very well written. 

Author Response

We would like thank the reviewers for their thoughtful comments. We have revised the manuscript based on this feedback. Please see attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Accepted

Author Response

The English improved through the manuscript. The manuscript was revised by an English native speaker (through the manuscript).

Author Response File: Author Response.pdf

Reviewer 2 Report

Thank you for taking into account my comments.

Author Response

The English improved through the manuscript. The manuscript was revised by an English native speaker (through the manuscript).

Author Response File: Author Response.pdf

Reviewer 3 Report

The test quantity of the experiment, and discussion of the manuscript is still insufficient.

Author Response

We would like thank the reviewers for their thoughtful comments. We have revised the manuscript based on this feedback. The English improved through the manuscript. The manuscript was revised by an English native speaker.

Author Response File: Author Response.pdf

Reviewer 4 Report

Some corrections of the MS were done. I do not have additional comments.  I think that at present form it can be accepted for publication.

Author Response

The English improved through the manuscript. The manuscript was revised by an English native speaker

Author Response File: Author Response.pdf