Environmental Impact and Life Cycle Cost Analysis of Superhydrophobic Coatings for Anti-Icing Applications
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis study assesses the environmental and economic effects of polyurethane elastomer (PUE) superhydrophobic coatings for anti-icing purposes. By utilizing a Life Cycle Assessment (LCA), it compares PUE-coated surfaces with bare aluminum. The results indicate that PUE-coated systems not only minimize ice buildup but also have a reduced environmental footprint and are more cost-efficient. The research highlights potential advancements through the use of eco-friendlier materials, positioning PUE coatings as a sustainable and economical approach to addressing ice-related challenges.
The topic of this study appears to be somewhat original, though it builds on existing research. While superhydrophobic coatings and their anti-icing properties have been studied extensively, this study’s focus on conducting a comprehensive Life Cycle Assessment (LCA) of PUE coatings and comparing them to bare aluminum in terms of both environmental impact and cost offers a unique angle.
The conclusions of the study are generally consistent with the evidence and arguments presented. The references are appropriate and relevant. However, a few of the cited references are relatively older (from the early 2000s), especially regarding LCA and anti-icing materials. Including more recent studies could provide an updated perspective, especially with evolving environmental regulations and new materials.
Nevertheless, the used methodology is not acceptable. The LCA analysis is performed to estimate the environmental impact when “cradle-to-grave” scope is considered. It is also important that the use phase parameters are taken into the consideration. However, some of further controls should be considered. For example:
- the long-term impact of potential chemical leaching or degradation of PUE coatings over time, including their interaction with various environments (e.g., marine, atmospheric), could be critical for a thorough sustainability analysis.
- Inclusion of “end-of-life” assessment.
Author Response
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.
Comment 1: A few of the cited references are relatively older (from the early 2000s), especially regarding LCA and anti-icing materials. Including more recent studies could provide an updated perspective, especially with evolving environmental regulations and new materials.
Response: Thank you for your valuable suggestion. As per the reviewer's suggestion, the changes have been made in the revised manuscript (refer page no. 3).
Comment 2: Nevertheless, the used methodology is not acceptable. The LCA analysis is performed to estimate the environmental impact when “cradle-to-grave” scope is considered. It is also important that the use phase parameters are taken into the consideration. However, some of further controls should be considered. For example:
- the long-term impact of potential chemical leaching or degradation of PUE coatings over time, including their interaction with various environments (e.g., marine, atmospheric), could be critical for a thorough sustainability analysis.
- Inclusion of “end-of-life” assessment.
Response: Thank you for your valuable suggestion. As per the reviewer's suggestion, the long-term impact of degradation of PUE coatings and its environmental impact is reported in the revised manuscript. The present LCA model excludes transportation and end-of-the-life phases (refer page no. 3).
Reviewer 2 Report
Comments and Suggestions for AuthorsComments of coatings-3220062
The main weaknesses of the manuscript:
The manuscript can be published in present form. But please pay attention to the superscript or subscript of "unit".
Author Response
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.
Comment 1: The manuscript can be published in present form. But please pay attention to the superscript or subscript of "unit".
Response: Thank you for your valuable suggestion. As per the reviewer's suggestion, superscript or subscript of the units have been corrected.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors present an interesting manuscript devoted to the theoretical analysis of the efficiency of using superhydrophobic coatings based on polyurethanes. Some results presented by the authors are incomplete due to the lack of parameters/characteristics of the superhydrophobic coating:
1) It is necessary to present the characteristics of the coating: contact angle, roll-off angle, assessment of the stability of the properties. The reader cannot know how stable the coating you are considering is. How were the anti-icing properties of the coatings assessed? What is the adhesion of ice to the coating? Perhaps the coating loses its properties after one freezing cycle.
2) 2) Aircraft wings are a separate and very complex topic! Here, first of all, questions of mechanical resistance of the coating arise (effects of dust, sand, UV, etc.). It is also a known fact that the wings and fuselage are pre-flight treated with glycols; I think that such a comparison would be extremely appropriate.
In general, the article can be recommended for publication after additions have been made.
Author Response
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.
Comment 1: It is necessary to present the characteristics of the coating: contact angle, roll-off angle, assessment of the stability of the properties. The reader cannot know how stable the coating you are considering is. How were the anti-icing properties of the coatings assessed? What is the adhesion of ice to the coating? Perhaps the coating loses its properties after one freezing cycle.
Response: Thank you for your valuable suggestion. In line with the reviewer's comments, we have included the properties of the coating, such as the water contact angle and ice adhesion shear strength, in the supplementary file (refer to Table S1 and Table S2). While these specific properties do not play a direct role in the environmental impact analysis, we have considered their overall effect in terms of the coating's lifespan.
Comment 2: Aircraft wings are a separate and very complex topic! Here, first of all, questions of mechanical resistance of the coating arise (effects of dust, sand, UV, etc.). It is also a known fact that the wings and fuselage are pre-flight treated with glycols; I think that such a comparison would be extremely appropriate.
Response: Thank you for your valuable suggestion. The current manuscript focuses on estimating the environmental impact of the coatings based on the materials used in the inventory. We agree that factors such as the effects of dust, sand, UV exposure, and pre-flight treatment of wings and fuselage using glycol are also important. However, these factors have been covered in detail in the report [44], which was used to inform the assumed lifespan of the coating.
Reviewer 4 Report
Comments and Suggestions for AuthorsThe authors conducted a life cycle assessment (LCA) of bare aluminum and PUE-coated systems using the Centrum voor Milieukunde Leiden methodology, focusing on cradle-to-gate environmental impact. Their findings show that the PUE-coated system significantly reduces environmental impact and is more economical than bare aluminum, with potential for further improvements through the use of bio-based and less toxic chemicals.
Comments:
1. The authors mention the use of the Centrum voor Milieukunde Leiden (CML) methodology for Life Cycle Assessment (LCA), but they do not explain its principles or why it was chosen for this analysis. The CML methodology focuses on a midpoint impact assessment approach, evaluating categories such as global warming potential (GWP), acidification, eutrophication, and resource depletion. A detailed explanation of this method and how it applies to both bare aluminum and PUE-coated systems would enhance the reader's understanding of the environmental impact assessment.
2. The paper lacks a clear justification for the selection of the PUE-coated system for anti-icing applications. The authors should discuss the specific advantages of the PUE coating in terms of durability, cost, energy efficiency, and environmental benefits compared to other commonly reported anti-icing systems (e.g., hydrophobic coatings, electrothermal systems). A comparative analysis in the introduction would provide context and strengthen the rationale behind choosing this system.
3.Figure 1 is briefly mentioned without sufficient explanation. The authors should provide a detailed analysis of how the two energy systems (uncoated and PUE-coated) affect energy consumption and correlate with emissions. Does the PUE-coated system significantly reduce operational emissions? It would be helpful to explain the figure's data trends and their implications for fuel efficiency and carbon footprint, particularly in the aviation sector.
4. The Levelized Cost of Coating (LCoC) data presented in Table 3 compares the costs associated with uncoated and PUE-coated systems. However, the authors do not provide a detailed explanation of these numbers. The total costs and energy savings need to be discussed, along with conclusions on how the PUE-coated system improves cost-efficiency over time. The authors should also discuss how the cost savings scale with increased aircraft operational lifetimes and highlight key factors that make the PUE-coated system more economical.
Author Response
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.
Comment 1: The authors mention the use of the Centrum voor Milieukunde Leiden (CML) methodology for Life Cycle Assessment (LCA), but they do not explain its principles or why it was chosen for this analysis. The CML methodology focuses on a midpoint impact assessment approach, evaluating categories such as global warming potential (GWP), acidification, eutrophication, and resource depletion. A detailed explanation of this method and how it applies to both bare aluminum and PUE-coated systems would enhance the reader's understanding of the environmental impact assessment.
Response: Thank you for your valuable suggestion. As per the reviewer's suggestion, the Centrum voor Milieukunde Leiden (CML) methodology is explained in detail (refer page no. 4).
Comment 2: The paper lacks a clear justification for the selection of the PUE-coated system for anti-icing applications. The authors should discuss the specific advantages of the PUE coating in terms of durability, cost, energy efficiency, and environmental benefits compared to other commonly reported anti-icing systems (e.g., hydrophobic coatings, electrothermal systems). A comparative analysis in the introduction would provide context and strengthen the rationale behind choosing this system.
Response: Thank you for your valuable suggestion. As per the reviewer's suggestion, the changes have been made in the revised manuscript (refer page no. 2 & 3).
Comment 3: Figure 1 is briefly mentioned without sufficient explanation. The authors should provide a detailed analysis of how the two energy systems (uncoated and PUE-coated) affect energy consumption and correlate with emissions. Does the PUE-coated system significantly reduce operational emissions? It would be helpful to explain the figure's data trends and their implications for fuel efficiency and carbon footprint, particularly in the aviation sector.
Response: Thank you for your valuable suggestion. As per the reviewer's suggestion, the changes have been made in the revised manuscript (refer page no. 4).
Comment 4: The Levelized Cost of Coating (LCoC) data presented in Table 3 compares the costs associated with uncoated and PUE-coated systems. However, the authors do not provide a detailed explanation of these numbers. The total costs and energy savings need to be discussed, along with conclusions on how the PUE-coated system improves cost-efficiency over time. The authors should also discuss how the cost savings scale with increased aircraft operational lifetimes and highlight key factors that make the PUE-coated system more economical.
Response: Thank you for your valuable suggestion. As per the reviewer's suggestion, the changes have been made in the revised manuscript (refer page no. 9).
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript is ready to be accepted for publication. All issues were addressed.
