The Potential of Valorized Sisal Decorticated Waste in Rearing of Black Soldier Fly

Round 1

Reviewer 1 Report

Comments for author File: Comments.pdf

Author Response

Dear reviewer

I have worked on the comments and uploaded in the folder 

Author Response File: Author Response.docx

Reviewer 2 Report

This paper describes the use of sisal decorticated waste (I believe it is a plant material leftover from robe production) for feed for black soldier fly larvae. I find that this is a relevant subject to be investigated, and that the subject is relevant for the journal ‘Recycling’. However, I also find the paper in many respects is immature, the paper suffers from quit a few grammatical errors and places of imprecise language, which make it hard to read. I also suggest you reduce the number of significant numbers in most results. Because of this, I recommend that the paper needs major revisions before it can be reconsidered for publication.

 

Specific points of criticism.

Abstract.

Line 13. The listed ions seem rather arbitrary chosen? I think you have to explain why these are the ones that are reported or were analyzed?

Line 14. I suggest you avoid unneeded terms like ‘very’.

Line 15. Please report energy contents per quantum of material.

Line 16. You report that the BSF larvae contained less that 10% moisture. This number is unrealistically low. Please check it this number is correct. Living animals usually contain maybe 70-80% water.

Line 17. Wet weight og dry weight?

Line 19. Please rephrase, this cannot be understood, I think.

 

Introduction

Line 31. Please rephrase, this cannot be understood, I think.

Line 43-50. It seems a bit arbitrary and incomplete what is mentioned here? I find it hard to find the red line 

Line 50. % of what?

 

Materials and methods

Figure 1. I find it hard to see the importance of this figure?

Line 68. Please indicate what is measured?

Figure 2. I find it hard to see the relevance also of this figure. I am at least missing a scale bar.

Line 88. Please notice, that what you mention as ‘parameters’ are in fact ‘variables’. The same is the case elsewhere.

Figure 3. I find it hard to see the relevance also of this figure.

Line 110. Please indicate what is measured?

Figure 4. Please describe what is in this picture in greater details than now.

Line 128. How can you know that the material was fermented aerobically? It is probably just at the surface of the material that conditions were aerobic? Otherwise, you would have experienced a composting process, I think.

Line 129. Please explain what you mean by ‘vertical farm’?

Line 134. I suggest you avoid self-made abbreviations, such as e.g. 5DOL.

Line 140-141. Please rephrase, this cannot be understood, I think.

Line 147. Please indicate what is measured?

Line 148-149. I do not agree, this may not be the case, see e.g. Bekker et al., Waste Management 127, 73-79, 2021. Microbes may also degrade and use some of the substate.

Line 157. Is ‘CHNS/O machine’ the correct name of this piece of equipment?

Line 160. I suggest you either write formulas outside text. Or that you in words describes that the amount of protein is 6.25 times the amount of N. 

Line 164-165. Unclear what you mean, please rephrase?

 

Results

Table 6. Why are date not shown as average of triplicates as is the case in Table 5?

Table 7. I have a hard time believing the accuracy of these measurements as some values are quite different from values in the literature. Please check if values are correct and please show values as triplicates, incl. error measurements. 

Table 8. Please explain why only some of the measured values are also reported in the abstract? Please explain the selection criteria.

 

Discussion

I find it difficult to see why this section is separated into short subsections. It makes it hard to see the red lines and discuss the results in overall terms. I also find that most part of the Discussion section would have fitted better into Results.

Line 272-278. I find it hard to see why this is relevant when the +paper is about BSF rearing? Please explain.

Line 283-284. The DO bust be close to zero in most parts of the substrate, and highly variable at/close to the surface. The larvae and microbes take up the oxygen.

Lien 286-287. This conductivity is very high (much higher than e.g. seawater)? Is the value correct? And, why is electricity important? Ion strength is probably what you try to measure indirectly?

Line 286-288. I think you misunderstand the respiratory mechanism of insects. They breath gaseous O2 and not dissolved DO. Maybe you also forget that DO is used by microbes and therefore will disappear if not replaced by new O2.

Line 313. How much substrate was used to produce these larvae?

Line 319. Wet weight or dry weight?

Line 330-333. Many more studies are available. Please specify your selection criteria.

Line 336-338. This cannot be concluded. Many more aspects need to be taken into consideration.

Line 360-362. This is very strange?

Author Response

Dear reviewer,

I have worked on the comments and upload in the word document

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Please, see the comments in the attachment.

Comments for author File: Comments.pdf

Author Response

Dear reviewer

Kindly find the worked comment as you instructed

Author Response File: Author Response.docx

Reviewer 2 Report

I think the paper has been improved, not least the language. But there are still sentences I find hard to understand, and I recommend one extra round of language revisions. There are, however, other revisions which I don’t agree to, as described below. Therefore, I still cannot recommend publication until after major revisions.

 

Specific points of criticism.

Abstract.

Line 14 and many places below. Please adjust the significant figure to what can be justified by e.g. the accuracy og the analysis. E.g. is the protein analysis used in this study not a accurate measure of proteins.

Line 15. Why not kcal per 1 g? And, the value is unrealistically high? And, what do you mean by SDW?

Line 16-17 and Table 7: When I add all your contents, measure in %, I reach 148%. Are measures accurate?

 

Introduction

Line 53. What do you mean by ‘work better’? High protein may not necessarily be a sign of how well a substrate works but may also be related to e.g. low lipid contents (maybe something that affected results in table 7)?

Line 56. Why do you say ‘Therefore, the organic wastes will…’? Is there a relationship between substrate mixing (banana and spent grain) and organic waste treatment? Please explain.

Fig. 1. I still don’t think this figure is needed. It should be sufficient to give the coordinates, as you already do.

Line 156 and Table 6. I still find the sentence ‘The obtained difference explains the waste being reduced by being consumed by BSF larvae’ inaccurate. You cannot be sure it is the larvae that have reduced the substrate alone. Microbes may have consumed part of it. Under some conditions, microbes may consume more substrate than the larvae, see Bekker et al., Waste Management 127, 73-79, 2021.

Line 172. I think it works better now, with the equation outside the text. However, I think that N describes an amount (weight maybe?) rather than the number of nitrogen (atoms)?

Section 2.8. You also report on lipid, ash and carbohydrate contents but don't tell how these were measured?

Line 178. guess the t-test will not tell the difference, but the likelihood that averages are different?

 

Results and discussion

Table 1. Needs a bit more explanatory text. What is S/N? What is %W2 and %W3? Which means is it, that you are reporting?

Fig. 3 does not show amount on y-axis, but rather ratios?

Line 196. This sentence is not clear. What do you mean by ‘AS observed in (W1),’? Furthermore, Amount will normally refer to weight?

Line 204. Please specify ‘which findings’?

Table 2. I am no expert in conductivity but think that conductivity is most often reported in micro-siemens per centimeter. Your value corresponds to 0.015 micro-siemens per centimeter? Drinking water has conductivities of 200-800 micro-siemens per centimeter. Your waste apparently has much lower conductivity than drinking water? Is this true? In the first version of the manuscript, I thought you reported very high conductivity, but now very low ones? I suggest you check if these values are correct.

Figure 4 should be omitted. No need to repeat the data from Table 2.

Table 5. I think it should be sufficient to show either individual values or average and SD. Showing both is a bit extraordinary and confusing, I think.

Figure 5 should be omitted. No need to repeat the data from Table 5.

Figure 6 should be omitted. No need to repeat the data from Table 6.

Line 325. Microbes may have contributed, as mentioned above.

Table 7. Are these data trustworthy and reproducible? 16% protein is very low. 3.7% lipid is very low. 37% ash is very high. Added together, these numbers are higher than 100%. What biochemical compounds do you think all the carbohydrates represent, these numbers seem also high? I suggest you compare you data to other sources, see e.g. Eriksen 2022, PLoS ONE 17: e0276605.

Figure 7 should be omitted. No need to repeat the data from Table 7.

 

Conclusions

Line 379-383. It can be discussed if this text really belongs to Conclusions. It describes something that have not really been investigated. Maybe it would be better to include in Discussion?

Author Response

Dear reviewer,

Kindly find the document contains the worked comments of my revised article

Author Response File: Author Response.docx