The Introduction of Sustainable Aviation Fuels—A Discussion of Challenges, Options and Alternatives

Round 1

Reviewer 1 Report

This is an outstanding paper that shows the challenges (impossibilities??) of SAF.  My one suggestion is that - if possible - the author show the real consequences of high fuel prices on an airline or airline customer.   For example, given Lufthansa's current revenue how much of an increase in jet fuel price could they tolerate before they start to loose money and how does that compare to the large increases in jet fuel price projected in the paper.  Or conversely, how much would the average plane ticket need to increase such that the airline makes a reasonable profit when using targeted volumes of SAF. These types of examples would concretely show the financial impact we all will have to face by getting off petroleum based fuel

Author Response

Please find it in the attachment

Reviewer 2 Report

The paper provides a good overview of the SAF discussion in Europe in light of the ReFuelEU Aviation initiative.

·        Section 2 would focus more on the EU policy journey on the efforts of the decarbonization of transport and aviation in particular, including references/brief discussion on the LCA approaches.

·        A discussion on the GHG emission reduction potential of SAF pathways could be introduced as well.

·        Although totally understandable, the author provides only examples from Germany. A couple of more countries could be added in the discussion (e.g. Spain, the Netherlands – both advanced in such issues)

·        Lines 138 – 140: would like to have more information, e.g. sources of aviation demand projections, etc. The reported 47 million tons of SAF have been estimated by another source in the literature, and in particular from an NGO, and this should be clear in the text. The assumptions made in the original publication should be summarized here as well. Further, relevant figures from other sources should be provided as well, e.g. based on the information provided in the impact assessment of the Commission for the ReFuelEU Aviation, or the CTP 2030, etc. Other sources (with the necessary assumptions to focus on Europe) may include IRENA, IATA, IEA, etc.

·        In section 3.1 the list of SAF certified pathways should be included, or at least a couple of references should be provided to other sources clearly indicating the purpose of the citing the relevant references

·        Lines 171 – 173: what means "all available biomass"? Assumptions of the original work should be provided here as well to put the elements shown into the right context and perspective

·        Lines 188 – 194: what about the installed capacities for RES? electrolytes?

·        Lines 195 – 201: this would has to be compared to the numbers in the impact assessment of the EC for the ReFuelAviation initiative (and the CTP2030)

·        Lines 221 – 222: some additional discussion here would be useful. Several references on the implementation of CORSIA and the corresponding EU directives can be found in the literature

·        it is indeed important to discuss the issue of carbon leakage

·        paragraph starting on line 340: I would try to find in the literature quantification about the expected market share of such technologies in the future energy and technology mix

·        line 396: “we” should not be written as it refers to a figure form the literature – see relevant comments earlier

Author Response

Please find it in the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

This paper aims to discuss the economics of climate change mitigation in aviation and the role sustainable aviation fuels. Although there is very valuable information in the study, some issues need to be explained. My recommendations and questions are as follows:

-        The clear purpose of the study is not clear and its difference/novelty from the existing literature should be clearly stated.

-        There are quite a lot of numerical information in the study and it would be better for the reader to give these numbers in separate categories as tables.

-        The author focused only on CO₂ emissions. Other emissions should also be mentioned.

-        In literature, it will be useful to give information about the studies on the combustion of biofuels in aviation industry.

-        It should be given information about the general characteristics and prices of the fuels used in the aviation industry.

Author Response

Please find it in the attachment

Round 2

Reviewer 3 Report

·    Suggestions and critique of the reviews very carefully studied.

·       These corrections and additions seem enough.

·       The study complies with the acceptance state.