Prefeasibility Analysis of Different Anaerobic Digestion Upgrading Pathways Using Organic Kitchen Food Waste as Raw Material

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper by Alzate et al. presents the use of Anaerobic Digestion (AD) to produce energy from waste streams, especially from organic kitchen food waste (OKFW). The authors first reviewed the general AD system, highlighting the principles of selecting biochemistry, microorganisms, feedstock, inoculum, operational parameters, etc. Later, the author described a case study of OKFW using a simulated food waste mixture, and evaluated the AD performance with experimental, simulation, and techno-economic assessment means. The article is comprehensive and well-written, generating a high interest to the readers in the field. Therefore, I recommend the acceptance in its current form.

Author Response

We greatly appreciate the reviewer's comments on improving the quality and clarity of the manuscript. 

Reviewer 2 Report

Comments and Suggestions for Authors

The authors present a review on the progress in modifying anaerobic fermentation to produce volatile fatty acids or hydrogen instead of biogas in the course of the last 10 years. Focused on organic kitchen and food waste from Colombia, the authors expand the content by experimentally applying the results which can be derived from the review part. Furthermore, based on a suggested production process for biogas and mixed volatile fatty acids as well as the experimental data, the authors developed a techno-economic assessment to analyse the feasibility of a production plant.

Before, I list some minor corrections, which can be found. I would like to encourage the authors to deposit their experimental data in a scientific repository in order to make it easily accessible for other scientists.

p. 1, l. 20: OKFW instead of OFKW

p. 6, table 2: Please explain the abbreviation “VS” (used several times in the table)

p. 12, table 4: What is meant by the parameter “Ms”

p. 18, l. 555: I would prefer “Case study” instead of “Case of study”

p. 19, l. 601: In order to separate the biogas from volatile FA, I would suggest to make a line break after “(…3100P).”. This should stress the importance of the paragraph on VFA and make the section easier to read.

p. 19, l. 606: The unit should be nm.

p. 20, figure 6: The figure states “Sc2 Unit 60” should it not mention “Unit 40”? Otherwise, the corresponding text is missing an explanation of Units higher than 40. If so, the explanations should be complemented.

p. 21, l. 677: Instead of “table 8” “table 7” is written in the header.

p. 24, l. 774: Please correct “bio-hytane” to “bio-hythane”

p. 24, l. 774f: Please revise the sentence written there.

After applying the minor corrections mentioned, I recommend the article for publication.

Comments on the Quality of English Language

Beside the minor corrections mentioned, the language is easy to read.

Author Response

We greatly appreciate the reviewer's comments on improving the manuscript's quality and clarity. 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This paper has a rather original format, being a combination of a review paper and a research article. Anaerobic digestion, a widely used renewable energy technology using biogas as an energy vector, is the subject of this manuscript. The paper analyses the pathways that favour the production of energy carriers and high-value products, considering key issues in relation to operating conditions and substrates. This is a part of the manuscript that could stand on its own as a review paper. The next section presents a case study where renewable energy and mixed volatile fatty acids are produced through the application of the biorefinery concept to several  proposed scenarios using organic food waste as feedstock. The case study includes an experimental and simulation phase. This part of the work needs to be improved, in particular from a methodological point of view. The subsequent research steps and experimental procedures need to be clarified. This manuscript requires minor revisions before it is ready for publication. Further detailed comments for consideration are provided below.

Comment 1#

Tables 1, 2 and 5 require correction. The details are not clear. Write the microorganism names in italics. Table 2 is too long and needs to be broken down into a number of parts. Unnecessary dot in Table 5

Comment 2#

Line 200, 222: Correct the space

Comment 3#

Check the form of citations so that there are two numbers in one bracket.

Comment 4#

Figure 5 presents some interesting content, but the form in which it is presented could be made more accessible. The layout of the diagrams could be improved. Customise captions.

Comment 5#

Line 605: “The absorbance was determined at a wavelength of 500 μm”, wavelength is in nm, correct it.

Comment 6#

 

References require detailed editing

Author Response

We greatly appreciate the reviewers' comments on improving the quality and clarity of the manuscript.

Author Response File: Author Response.pdf