Conversion of Sugarcane Trash to Nanocrystalline Cellulose and its Life Cycle Assessment
Round 1
Reviewer 1 Report
The authors report on sugarcane Trash (SCT) and compared the environmental impact of SCT in NCC production to that of bioethanol. The NCC production was suggested to have a higher envronmental impact than bioethanol. Most effects were contributed by electricity and MIBK usage for NCC and bioethanol production, respectively.
The authors need to address the following issues:
Most effects were contributed by electricity… What does this mean?
By sugarcane trash, do the authors not mean bagasse?
“The changing color indicated increased and decreased cellulose and lignin content…” how can the change in color determine this, since both are colorless in pure form?
“Hydrolysis of the bleached pulp was studied using 50% and 58% sulfuric acid at 45 133 ℃ for 30 min, 45 min, and 60 min…” Following acid hydrolysis, the cellulose needs to be dialyzed for several days to remove sulfate ester moieties from the surface, was dialysis performed to get to neutral pH? Otherwise it cannot be claimed that pure NCC was obtained.
The authors need to explain the origin of the spherical shapes of NCC, as opposed to the common long strands with lengths (100-300 nm) and high aspect ratios typically observed. Having spherical shaped NCC is very unusual and the characterization not convincing. What material constitute the rest of the matrix in which the NCC is supposedly embedded?
Figure 5: the XRD peaks are very broad suggesting an amorphous state, the opposite of NCC which should show sharp peaks. With NCC as spherical particles, it would be difficult to accurately assess the degree of crystallinity.
The FTIR spectrum should be shown in the more common Transmittance mode, and the relevant peaks should be labeled. There should also be many SO3 related peaks that must be mentioned based on the manner the synthesis was performed.
SEM should be accompanied by a EDX analysis, to see what elements are distributed where.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The topic of the work is relevant and is devoted to a comparative analysis of the conversion of waste from the processing of plant materials using catalysts.
There are major remarks on the manuscript:
1. The authors consider 2 technologies - the production of NCC and bioethanol, but only the first part is described in the results. Data on the enzymatic hydrolysis of sugarcane trash, the effect of pretreatment, the rate and efficiency of the catalytic processes, and the characterization of the products formed should be reported. This shortcoming is the most significant in the work, otherwise it is necessary to change the name, reduce the Life Cycle Impact Assessment section and pay more attention to obtaining NCC and its properties.
2. Results on NCC morphology. The resulting product is not entirely clear on the SEM photo, it turns out that NCC is directly only in certain places, while much larger, non-nanoscale fragments are visible against the background. You should either explain in more detail, or leave only the result of TEM. The titles
3. Results of determining the crystallinity of the products. For clarity, it is necessary to give an example of a diffraction pattern of the original raw material or an alternative NCC, for example, obtained from another raw material, as a comparison. Fig.4 and Fig.5 lack NCC. Photo hydrolysis sounds incorrect.
4. Abstract. Too many values are presented, while there is no information about what catalytic processes are being studied, what is new in this direction. Otherwise, there are doubts about the correspondence of the article to the journal.
5. line 37: The phrase is not quite correct, because hemicelluloses are mixed polymers, there are xylans, mannans, galactans, etc. Thus, the number of carbohydrate polymers can be 3, 4 or more. Rephrase.
6. line 72: The phrase that 33.35% (i.e. only cellulose) can be used for ethanol biosynthesis is not correct. It is known that the hexoses contained in hemicelluloses can be consumed by S. cerevisiae to produce ethanol. In general, it seems that the authors have difficulties in explaining the processes of bioconversion of plant materials.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I am still of the opinion residual lignin is what is considered spherical NCC in this paper; HCl with acetic acid treatment can give spherical NCC but not sulphuric acid. This will undoubtedly be further investigated by others.
It is not clear to me how the work is related to Catalysis, perhaps the authors can comment on this.
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
The authors responded to comments, but I did not notice significant changes in the manuscript. I recommend changing the title of the article (removing the comparison with the production of bioethanol) and paying more attention in the results to the production of NCC, this is the main experimental result. The Life Cycle Impact Assessment can be significantly reduced, or a detailed comparison with the literature data can be made in a separate manuscript. In addition, there are some gaps in knowledge about the theory of the conversion of plant materials into bioethanol (the answer to Comment 6 is not completely correct).
The interpretation of SEM analysis results also remains ambiguous. In the above example, the predominance of nanospheres is clearly visible, but in your figures (perhaps due to poor image quality) there are not a large number of nano-objects. I recommend removing this part from the manuscript.
Author Response
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