Techno-Economic Evaluation of Biorefineries Based on Low-Value Feedstocks Using the BioSTEAM Software: A Case Study for Animal Bedding
Round 1
Reviewer 1 Report
The paper reports technical and economic data of a biorefinery using as animal bedding materials as feedstock. The results for the animal bedding process come from using an open-source code. The case is compared to the straw based process, and interesting results are reported. However, two important points should be addressed before acceptance:
1. The traceability of the methodology must be improved significantly.
- The source of the software is referenced correctly, but its version is not mentioned in the document. Given that this is an open-source code, then further modifications through different branches can come out afterwards. So, the date of access is not sufficient; the build version or similar must be clearly identified in the manuscript. The same applies to the version of the documentation of the software.
- In many parts of the manuscript is stated that "implemented as in the original software". That results somehow hard to track back if the original source is not provided. The methodology implemented in the original software came from a previous source so that the previous source must be cited, as usual.
- Some information comes from a personal quotation. That is ok, but at least the date of the quote must be reported. The APA style for personal communications is suggested.
2. The data about the minimum ethanol selling price is very interesting. However, this type of study usually reports a sensitivity of the cost to the plant capacity. This is even more relevant provided the significant weight of the capital in the economic balance. A very important point in economic evaluations is the installed capacity from where the process becomes economically sustainable and that information is missing in the paper. The sensitivity of the cost to the plant capacity should be reported at least briefly.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
This MS presents a BioSTEAM TEA of ethanol production from animal bedding. The authors properly address an important but somewhat neglected area of biofuel research, the impact of low cost biomass and biomass conditioning in the MSP of ethanol. Moreover introduce an case study for animal bedding using the a new economics tool as BioSTEAM. I find the paper well-structured and interesting, with very few grammatical errors, as far as I can see. After a few minor corrections I think the paper is well worth to be published.
Comments:
Line 47-50, a conditioning concept is introduced, be more specific about what type (physical, mechanical, chemical, etc ) and general equipment of conditioning are you referring, please provide references.
Section 2. Please provide in the text or table the chemical and physical characteristics of both wheat straw and the animal bedding. The bulk density and the dimensions of these type of materials make them hard to handle. In addition I would refer in the text each supplemental figure.
Line 93-94, fermentable sugars are in the liquid fraction, why the complete slurry was not fermented, please provide an explanation of the configuration used in this study.
Line 107, enzymes for this model were purchased externally or produced on site?, please provide this information in the text.
Line 113-115. It looks that ammonia was used as N supplement, but which was your C source? please provide this information in the text.
Section Economic estimations.
It looks that most of the economic parameters used to estimate CAPEX and OPEX are based in the original model (BioSTEAM), however I strongly recommend to briefly explain them.
Please included the discounted cash flow analysis parameters used to calculated MSP in text or a table
How fixed cost were estimated?
The cost of equipment are updated to 2019?
Section Results and Discussion
General comment: the feedstock utilized in this economic modeling are high in ash content (mostly silica) and low bulk density, so I am wondering if this model has considered special equipment design to avoid great wear of the processing equipment, as well the influence of a precondition step to deal with the bulk density of the biomass? Please could you address these topics
Supplemental materials.
Figure S4 and S5. Both figures are recycling water after the filter press.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors deals with a very interesting subject, as they assess the feasibility of a biorefinery based on low value feedstocks, facing one of their main problems, which is the economic impact of these facilities, and proposing a solution.
Moreover, the presentation of the results is complete and thorough, connecting with clear conclusions.
Thus, I can not comment much about this work, as it was carried out properly.
Having said that, I want to ask you some changes and questions:
- There are some typos in the text, such as the lack of space between data and their units (lines 18, 22, 233, 236, etc.).
- Concerning the keywords, a piece of advice: except for bioethanol, change the rest, as they are included in the title. This way, you will have more different words and the search engine positioning will be better for your article.
- Line 56: I guess that you compare your biorefinery proposal with a wheat straw biorefinery because it is a consolidated facility and very similar to yours. Point out these reasons clearly at this point (or other that I can forget).
- In the materials and method section, I really miss a basic scheme explaining the three biorefineries you have studied, including the main steps carried out and pointing out (visually) the differences among them.
- L. 35 add more current references (2019-2020) to support this idea, which is really interesting.
- L.40 add more current references to support your idea, here some you should add:
- They worked with frying oils: Encinar, J.M.; Nogales, S.; González, J.F. 2020. Biodiesel and biolubricant production from different vegetable oils through transesterification. Engineering Reports, DOI:https://doi.org/10.1002/eng2.12190
- They talk about many wastes, such as pomace: Vivek Kumar Gaura, Poonam Sharmac, Ranjna Sirohid, Mukesh Kumar Awasthie,
Claude-Gilles Dussapf, Ashok Pandey. 2020. Assessing the impact of industrial waste on environment and mitigation strategies: A comprehensive review. Journal of Hazardous Materials. DOI: https://doi.org/10.1016/j.jhazmat.2020.123019 - They worked with agricultural wastes: Alexis Sagastume Gutierrez, Juan J. Cabello Eras, Luc Hens, Carlo Vandecasteele. 2020. The energy potential of agriculture, agroindustrial, livestock, and
slaughterhouse biomass wastes through direct combustion and
anaerobic digestion. The case of Colombia.Journal of Cleaner Production. DOI: https://doi.org/10.1016/j.jclepro.2020.122317
- Adding these references would be interesting, as your reference lists does not include (in my opinion) enough current works (2019-2020).
- Maybe I am wrong, but you have considered your design starting with a fixed amount of feedstock, and all your comparisons are with equivalent facilities. This is only one question (just out of curiosity): have you considered a real scenario, according to data of feedstock generation / product demand, for further research in the future? It would made your work even more practical, which is a good point for many journals.
- In any case, your research work is really complete. Congratulations!
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The response to the comments provided by the authors is satisfactory and the manuscript was corrected accordingly. I have no further observations.
Congratulations to the authors.
