Pilot-Plant-Scale Extraction of Antioxidant Compounds from Lavender: Experimental Data and Methodology for an Economic Assessment

Round 1

Reviewer 1 Report

This paper proposes an economic assessment of SFE extraction with a wider approach than the conventional ones, like those for instance of the Meireles’s team (ref 16, 22 and 23 in the text). Here financial aspect is more developed and I will not give any comments on this part because it is out of my field of expertise.  I will focus on the technical part.

1-       How was done the scaling-up? I was not able to get the ref 27 from the authors. Because cost of utilities/kg of extract in table 5 diminishes with the size of the vessels (line 286, “CUT decreases proportionally with the change of scale”), this would indicate a diffusion controlled extraction where the CO2 flow rate is kept constant at scaling up, which is not very common. If it is the case, it has to be mentioned because usually the ratio CO2/feed is kept constant for solubility limited extractions and cost of utilities/kg of extract is almost constant. As the authors mentioned line 50, such processes have “relatively energy-intensive needs”, this is an important point.

2-       I was surprised by the low cost of the SFE plant (421 k€ for a 100 L extractor). Do the authors check these values with European manufacturers like NATEX for example?

3-       In the sensitivity analysis of paragraph 3.6, variation of the energy prices is not considered, as we unfortunately know that this price will significantly vary in these troubled times, it would have been interesting to give an idea of its influence.

I have more minor remarks

4-       The technical description of the process is not clear and does not present that the solvent pressure is reduced to 50 bar and that is must be recompressed to be recirculated. This constitutes the energetic cost.

5-       What do you mean with “10% of losses”? Does it refers to the recirculation flow rate? In this case this is a rather high value. What does it represent? Losses in the extract recovery? Leaks? Losses at the unloading?

6-       On Figure 1, are the two separators in parallel? By the way, the second one has no input.

7-       As mentioned in the text, the exchanger after Mixer 1 is a condenser not a cooler. The energy consumption of the coolant of this condenser is indeed the prominent energetic cost in the case of liquid pump recirculation cycle.

8-       “°C” has a strange typing in all the text.

9-       In table 4, the commercial price of CO2 is too high (almost 10 times lower if it is not bought in bottles). Indeed, it has a slight influence because these processes do not consume much CO2.

This paper proposes an economic assessment of SFE extraction with a wider approach than the conventional ones, like those for instance of the Meireles’s team (ref 16, 22 and 23 in the text). Here financial aspect is more developed and I will not give any comments on this part because it is out of my field of expertise.  I will focus on the technical part.

1-       How was done the scaling-up? I was not able to get the ref 27 from the authors. Because cost of utilities/kg of extract in table 5 diminishes with the size of the vessels (line 286, “CUT decreases proportionally with the change of scale”), this would indicate a diffusion controlled extraction where the CO2 flow rate is kept constant at scaling up, which is not very common. If it is the case, it has to be mentioned because usually the ratio CO2/feed is kept constant for solubility limited extractions and cost of utilities/kg of extract is almost constant. As the authors mentioned line 50, such processes have “relatively energy-intensive needs”, this is an important point.

2-       I was surprised by the low cost of the SFE plant (421 k€ for a 100 L extractor). Do the authors check these values with European manufacturers like NATEX for example?

3-       In the sensitivity analysis of paragraph 3.6, variation of the energy prices is not considered, as we unfortunately know that this price will significantly vary in these troubled times, it would have been interesting to give an idea of its influence.

I have more minor remarks

4-       The technical description of the process is not clear and does not present that the solvent pressure is reduced to 50 bar and that is must be recompressed to be recirculated. This constitutes the energetic cost.

5-       What do you mean with “10% of losses”? Does it refers to the recirculation flow rate? In this case this is a rather high value. What does it represent? Losses in the extract recovery? Leaks? Losses at the unloading?

6-       On Figure 1, are the two separators in parallel? By the way, the second one has no input.

7-       As mentioned in the text, the exchanger after Mixer 1 is a condenser not a cooler. The energy consumption of the coolant of this condenser is indeed the prominent energetic cost in the case of liquid pump recirculation cycle.

8-       “°C” has a strange typing in all the text.

9-       In table 4, the commercial price of CO2 is too high (almost 10 times lower if it is not bought in bottles). Indeed, it has a slight influence because these processes do not consume much CO2.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

In this paper, the technical and economic feasibility of lavender essential oil extraction by supercritical CO₂  method was investigated as a pilot plant scale. Even though the article has certain scientific significance, some parts of it are incomplete. I have the following comments.

 Abstract:

-The abstract should be revised and restructured. The results (numerical values) of the study should be included in the abstract. Which factors were more affected? Please clarify completely.

- I suggest to conclude based on the results obtained. 

 Introduction:

- The introduction does not provide the necessary information about the background of the study. Especially regarding other extraction methods and their advantages and disadvantages.

- Line 50 and elsewhere: Acronyms (abbreviations) should be included in the text when the words are first entered. In this case, SFE should be included on line 38.

- Line 52: “scCO₂” please write in complete form.

- The objectives of the study should be explained more clearly and precisely. In this section, a summary of the working method is given.

 Materials and methods:

- You should report all details of materials and equipment (supplier, purity and ….)

- Equation 1: Add “(%)” in front of “Extraction yield”. In addition, use the multiplication sign (×) in the equations.

- Line 121 and elsewhere: Please delete “•” after DPPH.

- Equation 2: Put “%” in the brackets.

The statistical analysis section should be added in the materials and methods section. I suggest describing which are the study factors and variables. Describe the analysis parameters, method of data analysis, etc.

 Results and discussion

- Section 3.2: Please describe the internal and external factors affecting the project of lavender extraction.

-Equation 3: Please use “×” instead of “*”. Also in equation 4.

- Section 3.3: Describe the key factors in an investment analysis of the Lavender project.

 - The result and discussion section in this paper is very important and the authors should present and explain the results obtained in their study well and compare it with the results of others. Therefore, this part should be strengthened.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors:

The manuscript "Pilot-plant scale extraction of antioxidant compounds from lavender: experimental data and methodology for the economic assessment" by Cruz Sánchez et al has demonstrated the price of the equipment was the factor that could most influence the robustness of the project and the business strategy. I have just a few suggestions.

1. Some background information or references are missing. In introduction, please add more background information about ROS and anti-oxidative function, which play important roles in many diseases. especially mitochondria damage and cancer development. It can emphasize the importance of your article. (Please cite: 1. An Epigenetic Role of Mitochondria in Cancer. Cells 2022, 11, 2518. https://doi.org/10.3390/cells11162518

2. Advances in the Prevention and Treatment of Obesity-Driven Effects in Breast Cancers. Front Oncol. 2022 doi: 10.3389/fonc.2022.820968.
3. mitochondrial mutations and mitoepigenetics: Focus on regulation of oxidative stress-induced responses in breast cancers. Semin Cancer Biol. 2022 Aug;83:556-569. doi: 10.1016/j.semcancer.2020.09.012.)

Best, 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Authors well answered to all comments in a proper manner. I recommend publication of the paper in its current form.