Assessment of the Impact of Material Selection on Aviation Sustainability, from a Circular Economy Perspective
Round 1
Reviewer 1 Report
This work describes a well-structured design and decision-making tool for an aircraft component based on various factors and criteria, such as circularity, cost and environmental impact. The process is described well in the manuscript and several aspects have been taken into account. A few minor comments follow below:
line 42: typo at 'end-of-life'
line 67: the authors need to add 1-2 phrases of what are the limitations mentioned in Ref.[14], not just cite the paper.
Section 2.2, lines 127-129: are these literature sources available in this study? Also, what would be the functional unit this study was based on and the emissions calculations were referring to?
Section 2.2: It's not clear which exactly is the system under study. Is it a particular aircraft component from a particular aircraft? As manufacturing assumptions are made, this needs to reflect a particular component and its manufacturing processes.
Line 155-156: Although this sounds reasonable, it needs to be properly justified with a reference. Are there any LCAs showing that the use phase is the most dominant in terms of emissions? How about the manufacturing?
Line 189: Please expand EoL to 'end of life' with the abbreviation in brackets.
In Table 1 why the weight of the recycled CFRP is higher than the virgin CFRP component? Is there a justification to this?
The novelty of the presented work needs to be emphasised more. How is this tool going to help people make decisions? Why is it more robust than the current methods?
Author Response
Dear reviewer,
Thank you a lot for your fruitful comments with which I fully agree.
Please find the answers to your comments below:
line 42: typo at 'end-of-life'
corrected
line 67: the authors need to add 1-2 phrases of what are the limitations mentioned in Ref.[14], not just cite the paper.
the structure of the phrase has changed, by naming the limitation described in the mentioned paper, i.e. ‘...they are not related to the aviation sector [12, 14]’
Section 2.2, lines 127-129: are these literature sources available in this study? Also, what would be the functional unit this study was based on and the emissions calculations were referring to?
All literature sources exploited in the current work are described in section 2.2.
Explanations regarding the functional unit and some further considerations, have been added in the first paragraph of Section 2.1:
Section 2.2: It's not clear which exactly is the system under study. Is it a particular aircraft component from a particular aircraft? As manufacturing assumptions are made, this needs to reflect a particular component and its manufacturing processes.
With regards to your previous comment, the system under study is a hypothetical aircraft panel component made of typical aerospace materials. Please, see the answer to the previous comment.
Line 155-156: Although this sounds reasonable, it needs to be properly justified with a reference. Are there any LCAs showing that the use phase is the most dominant in terms of emissions? How about the manufacturing?
Citation has been added. The impact of manufacturing in terms of environmental emissions is almost negligible compared to the use phase impact, especially when speaking about sectors with long lifetime duration, such as the aviation sector.
Line 189: Please expand EoL to 'end of life' with the abbreviation in brackets.
Done
In Table 1 why the weight of the recycled CFRP is higher than the virgin CFRP component? Is there a justification to this?
The mechanical properties of the recycled CFRP are generally inferior to these of the virgin one. Therefore, to compensate for the material property variation, the recycled CFRP should be thicker and thus heavier, in order to present the same mechanical properties with the virgin one. This is explained in section 2.1.
The novelty of the presented work needs to be emphasised more. How is this tool going to help people make decisions? Why is it more robust than the current methods?
The novelty of the present work is justified in the 4th and 5th paragraph of the introduction section. To emphasize the novelty, two additional phrases have been added a the end of the 4th and 5th paragraph of the Introduction Section.
Reviewer 2 Report
The article is focused on the assessment of the impact of material selection on aviation sustainability from a circular economy perspective. The issue of sustainability, which the authors deal with, is very actual and topical. The form of the article (separation chapters, choice of pictures, diagrams etc.) is adequate to its content. The scope of the article proportional to the information value of knowledge contained in it. The authors properly relate the article to the previous publications on the given topic.
However, there are some issues that could be improved.
There should be a description on the organization of the paper at the end of the introduction section,
The authors should consider testing the effectiveness, especially accuracy, of the used/proposed methods.
The authors should add a comparison of results to other similar studies to the conclusion and they need to give some directions on their future works in the conclusion section.
Author Response
Dear reviewer,
Thank you a lot for your fruitful comments with which I fully agree.
Please find the answers to your comments below:
There should be a description on the organization of the paper at the end of the introduction section.
A small description of the paper structure is given at the end of the introduction section.
The authors should consider testing the effectiveness, especially accuracy, of the used/proposed methods.
In the conclusions section, 2 phrases have been added emphasizing the sensitivity of the tool to the accuracy of the input data, as well as the need to define procedures which can guarantee the scientific validity of the assessment.
The authors should add a comparison of results to other similar studies to the conclusion and they need to give some directions on their future works in the conclusion section.
The authors are aware of LCA studies which have been cited in the manuscript and assess the environmental, economic impact, and circularity, individually. Therefore, as the developed holistic tool assesses the combination of LCA, LCC and circularity metrics, a direct comparison cannot be easily made with other studies from the literature. A relevant statement is also added in the end of the 4th paragraph of the introduction section.
Moreover, in the conclusions section, a mention on the future work of the authors is made.
