Physicochemical Properties of Biobutanol as an Advanced Biofuel

Round 1

Reviewer 1 Report

In the manuscript entitled "Use of biomaterials for biobutanol production: review and application" the authors describe the physicochemical properties of different blends of bio-butanol-gasoline, bio-ethanol-gasoline and other additives.

This work presents some interesting data, but the article lacks order and logic.

Comments

Line 2. Title: "use of biomaterials for biobutanol production: review and application”. This title does not correspond to the work that we can see in the article. This paper does not discuss the production of biobutanol from organic sources, a great deal of the work is focused on the physicochemical properties of biobutanol-gasoline and bioethanol-gasoline blends. The authors should review the title of the paper.

Line 20. Bio-butanol is a…. Line 21. …Bioethanol and it… Line 22 …reviewers bio-butanol… Line 28: bio-butanol; bioethanol. The same in the rest of the text. The authors use the words biobutanol and butanol interchangeably, although they sometimes differentiate the two words when talking about biologically produced butanol (bio-butanol) and chemically produced butanol (butanol).

Line 20. Biobutanol is not environmentally friendly, in any case the source used will be, but biobutanol (biological) and butanol (fossil) produce the same pollutants.

Line 21. Change “materials” to “sources”

Line 32. … obtaining fuels and energy.

Line 39. Imported or fossil fuels?

Line 39. Biofuels do not reduce greenhouse gas emissions. The authors must differentiate between net production of greenhouse gases and gross production of greenhouse gases

Line 41. “The production of biofuels will also improve the economic position of local workers by creating jobs” Reference.

Line 46-52. The use of energy crops reduces the availability of food; therefore, they should be included as first-generation biofuels.

Line 55. …Composition (cellulose, hemicellulose and lignin) of different…

Line 61-62. Missed citation [XX]

General. The introduction should include data from techno-economic studies of the different production ways, e.g., https://doi.org/10.1002/bbb.143

General. The authors should explain the processes for biologically producing alcohols from lignocellulosic biomass (Pre-treatments, enzymatic hydrolysis, fermentation, SSF, SHF, consolidated bioprocessing, etc.).

Line 67. Are there more sources to produce these alcohols? e.g. animal waste?

Lines 89-90. Biological production. Lines 91-94. Syngas source. Lines 95-118. Chemical production. Lines 119-130. Syngas source. Lines 131-148. Biological production from lignocellulosic waste. Authors should reorder the content of the introduction.

Line 134. References 71 and 73 do not refer to the production of isobutanol from lignocellulosic materials. These citations show the first genetic modifications for microorganisms producing isobutanol (71) and modifications in other microorganisms (73).

Lines 135-148. I recommend describing the use of GMOs as producers of bio-butanol (e.g., isobutanol GMOs producers). For example, is well know that the production of isobutanol with wild microorganisms is not economically viable, they have very low production rates. The metabolism of ABE is not of interest in this article as there are numerous metabolic pathways to produce these alcohols.

Lines 149-154. The authors should examine the legislation for the use of these alcohols as additive to gasoline and diesel in different countries, for example in the European Union and the United States. The United States was the first country to allow the use of isobutanol-gasoline blends.

General. I recommend a restructuring of the introduction. The introduction is untidy and contains information of little interest for the purpose of the article (physico-chemical characteristics of blends bioalcohol-gasoline). In addition, I recommend including techno-economic studies of the bioproduction of these alcohols from different lignocellulosic waste and syngas.

Table 3. The information in the table is better in text.

Figures 10, 11, 12. It is not necessary to show all chromatograms, show only the most relevant

Line 585. This article does not describe well the production of the alcohols, the article deals with the physicochemical properties of alcohol-fuel blends

Line 585. Viable? Reference. Line 599. ¿es la producción de bio-butanol de segunda generación económicamente viable?

Line 593. … same raw materials…

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Title: The title is not appropriate. From the title I thought it was a review article, but its a research article. The title should be rewritten in order to reflect the content of the paper.

Keywords: use keywords different from the title. This will increase the visibility of your paper.

Introduction:

Line 31: explain what is the current global situation.

Line 47: can be used for what?

Line 48: significant amount of value added products instead of renewable energy.

Line 50: reducing which emissions?

Line 55: is shown in Table 1.

Table 1: I would separate between first, second, and third generation. at the moment all the feedstocks are mixed up.

Overall the introduction is too large. it should be reduced to at least 50% of its current size. I just got lost with all the information that is provided in there.

Results: You need to reference the Figures and Tables in the text before you show them.

Figure 11 and 12 are not fundamental, neither the text in lines 490-502. I would delete all of this and just focus on Table 6.

Overall, you have discussion in the results section but you don't present your results at all. Please make it clear. Or you have Results and discussion separate or you join them. At the moment they are all mixed up.

You need to present your results before you discuss them. What can we see from each figure? What is the trend? What is the highest and the lowest value?

Discussion: You are just reporting the results obtained by other scientistics. This is not how a discussion should be written. You should compare your results with the results obtained by other authors.

Conclusions:

Line 584: You are not reviewing! This is a research article. Please rephrase. This paper investigates, not reviews.

Line 595: You didn't do any economical analysis so you can't make this type of conclusions in your paper.

The conclusion should be rewritten in order to report the conclusions of your study. At the moment its just general things you are talking about.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

This study investigated the potential of butanol as an alternative to ethanol. This work shows scientific contribution to the field and is appropriate to be published in this journal. Following modifications can make this article more solid: 

Line 26: “it is potentially a better fuel for use in gasoline engines than the more widely used ethanol”. “Better” is a very vague word. Although butanol blends offer some advantages over ethanol blends, but it is not necessarily meaning that butanol is a better option. For instance, we still do not have the technology to produce butanol as cheap as ethanol which is a very important factor. Many considerations must be taken to account for this sentence. You can use the following paper to see what parameters need to be considered: “Identification of Promising Alternative Mono-Alcohol Fuel Blend Components for Spark Ignition Engines”  

Line 41: “bioethanol and biodiesel produced from food sources, are currently the most common alternative fuel.”. This sentence must be modified. Nowadays, ethanol is not produced solely from food resources. It can also be produced from lignocellulosic biomass. Companies such DuPont are exploiting such technologies. Same for biodiesel as it can obtained from sources such as cyanobacteria and microalgae.  

I would suggest dividing the introduction into two parts to avoid confusion for readers. After a general introduction on biofuels, you can add a subsection to explain the production pathways. Then, you can add another subsection to focus more on fuel properties which is then followed by the experimental section. Maybe choosing a better tittle for the paper can help readers to understand what they are going to read.  

MTBE and ETBE have known negative environmental impacts. Why you chose them for your blends? 

It is impossible to measure T100 during the distillation. How did you measure it? To find why it is not possible, following papers can be helpful.  

• Prediction of the Distillation Curve and Vapor Pressure of Alcohol–Gasoline Blends Using Pseudocomponents and an Equation of State 
• Near-azeotropic volatility behavior of hydrous and anhydrous ethanol gasoline mixtures and impact on droplet evaporation dynamics 

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

The current work deals with the use of biomaterials as fuels, especially butanol. It is a well presenting paper, with a well-established research methodology and a very comprehensive experimental section. The paper deserves publication after the following minor revisions:

1. Abstract: It is very poor comparing with the rest of the paper. The authors ought to mention at least some indicative results-highlights of their study.
2. Keywords: Why butanol is in bold?
3. Line 175: Syntax error.
4. Table 3: Rename “Spray technique” into “Injection technique”.
5. Discussion: Include also in your discussion the in situ production of alcohols in gasoline (https://doi.org/10.1016/j.cattod.2014.07.058) as potential replacement of GEOs (Gasoline Ethers Oxygenates).

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

After the first revision the article has been improved. I think it is an interesting work.

Author Response

Thank you very much for your peer review.

Reviewer 2 Report

I stand by my decision of rejecting the paper.

For example, the discussion of the paper was not improved. The authors are not discussing their results but rather listing findings reported by other authors.They should discuss their own results and then support them using the references.

Author Response

Thank you for the peer review. We have greatly extended the discussion and compared it with other relevant papers. (line 469-543, line 552-572, ref 84, 85, 88, 92, 93, 99,  101, 102)