Valorisation of Organic Waste By-Products Using Black Soldier Fly (Hermetia illucens) as a Bio-Convertor
Round 1
Reviewer 1 Report
Hermetia illucens is one of the most popular studied insect species among insects for animal feed and pet food so it is highly justified to realize this topic. In my opinion, this topic is very relevant and necessary. The manuscript is a good contribution to this issue and includes interesting and necessary problems.
The manuscript is well written and its contents are appropriate. The structure of the manuscript is correct. The methods used are appropriate. The results obtained may serve as a prelude to further research in this field.
In my opinion, this manuscript fits the profile of the Sustainability Journal.
I noted a few small comments:
Species names should be written in Italics such as Hermetia illucens
Section ‘1.1 Outcomes’ does not seem to be appropriate here. I propose to move to the Materials and Methods section.
In the methods section, there is no description of the statistical methods used in Table 2.
Line 433 please combine citations
Author contributions should be prepared using the authors' initials, not whole names.
There are several inaccuracies in the literature list e.g., only the first author is listed followed by et al.
Author Response
Thank you very much for your kind words and very useful review
Please find my responses below:
Species names should be written in Italics such as Hermetia illucens
Response: Thank you for your close attention. All of the species names have now been corrected (italics)
Section ‘1.1 Outcomes’ does not seem to be appropriate here. I propose to move to the Materials and Methods section.
Response: Thank you – the outcomes have now been moved to methods and the section number changed to section 2.1. All if the following sections have been renumbered in methods.
In the methods section, there is no description of the statistical methods used in Table 2.
Response: Thank you, this has now been added to the section in methods
Line 433 please combine citations
Response: This has been done.
Author contributions should be prepared using the authors' initials, not whole names.
Response: Thank you – this has now been done.
There are several inaccuracies in the literature list e.g., only the first author is listed followed by et al.
Response: Thank you for your close attention. We have now fixed all ‘et al’ issues and corrected reference 5.
Reviewer 2 Report
In this manuscrips, it is not clearly provided how the feedstocks are valoraized to what. Fertilizer? Biodiesel? No information is given. It seems that only analysis results of feedstock before and after treatment are given, which is no scientific insight. To publish as a scientific paper, such insight and suppored data must be clearly given.
Author Response
Thank you for your useful comments on our work. We found these very useful in our edit and we feel we have improved the clarity of our intention as a result.
In this manuscrips, it is not clearly provided how the feedstocks are valoraized to what. Fertilizer? Biodiesel? No information is given. It seems that only analysis results of feedstock before and after treatment are given, which is no scientific insight. To publish as a scientific paper, such insight and suppored data must be clearly given.
Response: We are sorry that we didn’t make it clearer that the waste valorization is achieved by bioconversion of the waste into insect body mass. In other words, the black soldier fly larvae (BSFL) consume the waste, grow, converting the waste into more useful products. The insects are harvested and made into insect meal, which is a good replacement for animal protein (often fish meal) in feed manufacture. Fishmeal and fish oil are used extensively in animal feed production, however, they are believed to be unsustainable and relatively expensive (around £1000 per tonne). The Frass is a useful by-product which has, potentially, better potential as a fertilizer (based on N:P:K) than other animal waste currently valued as fertilizer (chicken manure is around £100 per tonne).
We thank the referee for pointing out that we have not been explicit enough about how the products might be used and how this adds value to the food waste processed.
To make it clearer, we have added the following to the third paragraph of the introduction: “There is a growing interest in the use of insects as natural bio-convertors of organic waste valorizing the waste by consuming the waste, incorporating it into their bodies and, in the process, converting it into valuable products”. At the end of the fourth paragraph we added: ”In this paper we will focus primarily on the value of the products as constituents of animal feed”.
In paragraph 8 we changed the first sentence adding the section in italics: “The increased interest in the use of BSFL as an organic waste management tool and a source of raw materials for the manufacture of animal feed has led to a better understanding of how nutrient density and feed substrate quality can influence the development and growth of BSFL.”
We feel that the results section is quite clearly focused on the nutritional profile of the BSFL product and the value of the different BSFL products (i.e. the product derived from different feedstocks) as constituents of aquaculture feed and that the significance of these results is explained quite comprehensively and with appropriate context in the Discussion.
To underline that we were primarily interested in valorization of food waste through the bioconversion of the waste into feed ingredients, we have changed the final paragraph in the conclusion: “BSFL treatment is a viable option for recovering and recycling organic waste by-products, especially if it is traceable to source. It provides opportunity for added valorization of these organic waste products as constituents of animal feed providing a more environmentally friendly alternative route than landfill or AD.
We hope that the referee will now agree that, our evaluation of the increase in nutritional and economic value of the waste by conversion into insect meal (and other useful by-products), showing that this insect meal would be a viable alternative to expensive and less sustainable animal feed constituents (e.g. fishmeal and fish oil) that we have offered some useful scientific insight.
Reviewer 3 Report
Thank you for the opportunity to review this article.
The authors evaluated the Valorisation of Organic waste by-products using Black soldier fly (Hermetia illucens) as a bio-convertor.
Line 77. Hermetia illucens...Please write in italics
Line 87. H. illucens... the same as above
Line 119,120. CH4...4 is exponent?
Table 1. H&B...what dose it means?
Table 2b. Please write the table with the same way in the first column
Line 396. [53]...what dose it means?
Author Response
Thank you very much for your kind words and positive review. We believe we have made all of the changes you suggested but we were not certain what you were suggesting in reference to Table 2b.
In detail:
Line 77. Hermetia illucens...Please write in italics
Response: Thank you for your close attention. All of the species names have now been corrected (italics)
Line 87. H. illucens... the same as above
Response: Thank you, corrected.
Line 119,120. CH4...4 is exponent?
Response: Thank you, Methane formula corrected to CH4 (subscript 4).
Table 1. H&B...what dose it means?
Response: We are sorry for the confusion – the source of the waste has been added to make it clearer.
Table 2b. Please write the table with the same way in the first column
We are not sure what the referee would like us to do, however, his comment did draw our attention to the table numbering and we have now corrected this. We have changed the numbers from the original table 2a to table 3a upwards, including the in text citations.
Line 396. [53]...what dose it means?
Response: Thank you. This was a reference. We have moved it to the figure legend.
Round 2
Reviewer 2 Report
Reviewer's comments are addressed in the revision.
