Impact of Fuel Production Technologies on Energy Consumption and GHG Emissions from Diesel and Electric–Hydrogen Hybrid Buses in Rio de Janeiro, Brazil

Round 1

Reviewer 1 Report

The research would be enriched by a review of the literature supporting the concept of green urban transport and an assessment of the importance of green urban transport, its impact on the urban environment and urban dwellers. This should be linked to the fuel used by urban buses and green fuel alternatives.

I missed a comparative analysis with similar studies conducted by other scholars with researchs on a similar topic.
Most of the sources of the literature used are older than 5 years. The analysis of the sources of the most recent scientific literature would help to better justify the choice of the topic, would allow the authors of the study to provide deeper summaries and to make recommendations in the part of the conclusions.

Maybe efforts to rich the research trying to answer the following questions would be useful? Does Brazil have a strategy for achieving the UN Sustainable Development Goals? What about the strategy of the chosen city to analyze? Do other megacities of the world show similar problems? How is such  problems assessed and what decisions are made?

 

Author Response

See attached file.

Author Response File: Author Response.docx

Reviewer 2 Report

Congratulations, it is a very exciting topic and I really enjoyed reviewing the paper. Nonetheless, some aspect should be reconsidered or improved.

Line 29: And what about BEVs and PHEVs? Their share among newly sold cars is rapidly growing in certain markets (e.g. EU, China, USA). Please review and refer some market trends.

Line 43: Was there any other option, such as battery electric buses / trolleybuses / streetcars, etc. There a plenty of other technologies for reduction of GHG emission / air pollution of local public transportation.

Table1: It is shown rather badly in the pdf reader. I do not know whether it is the fault of pdf or other... I suggest that similar vehicle should be used for the analysis (e.g. 12m length solo bus with max theoretical capacity of n people, similar technical parameters, etc.). Then, this info could be put out of the table to the body text. So the table could be suppressed.

Table2: Put these infos to the body text - this table contains only the definitions.

Line114-117: A figure or table would be more appropriate.

Line 127: "capacity to process 13 x 106 m3 of oil per year" Do you mean 13×10^6m3?

Line 129: What does "bep" mean?

Line 130: This calculation would be more clear using a table.

Figure 2 and Figure 3 should be merged into one, using two axes.

Further considerations:

First, the paper lack of a cost-benefit analysis. I am sure, that hydrogen could be a sound solutation for future mobility, especially in the case of heavy duty vehicles, like buses, but they are much more expensive than conventional buses. You should analyse this aspect, as it is extremely significant from societal / financial point of view. Maybe a much more efficient solution would be reducing individual mobility (using tolls, reducing speed, etc.) and using conventional buses since it is much cheaper and lower car usage could cause similar reduction of GHG emission. When mobility demand is sufficient enough, implementation of a streetcar line would be an other viable answer. To highlight present mobility demand, please present the modal share in the paper.

Second, it is rather hard to follow the calculations. I suggest that modify them to a more user-friendly form using equations or even tables.

Author Response

See attacehd file.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors need to attend the following suggestions in order to support the relationship among objective, methodology, results, discussion, and conclusions:

·       To improve the introduction, literature review: They must include more background about the research topic

·       How did you define the sample size?. Why did they define a sample of 2 buses?. They must be precise the statistical method. Therefore, the methodology must be more detailed, and to specify the total process followed in the investigation.

·       The results and discussion must be explanatory and discussed in reference to the reality of the potential benefits. They need to be more objective

·       The results/discussion requires more strong support with others researchers and experiences related to the topic research in order to strength the discussion and conclusions, including more international and national references.

·       They need to discuss more with criteria of sustainable development.

·       What is the true contribution to scientific knowledge and the solution of the real problem?

·       What are the practical uses of the results obtained from this study?

·       To specify which were the main limitations to carry out this research?

·       It is necessary to include multidimensional strategies proposals to guarantee the aplication of th obtained results in order to contribute to sustainable development.

·       They need to discuss, what it would happen if the problem is not attended, considering social, ecological, economics, legal and environmental policy impacts?. Therefore, they need to propose strategies for achieving best social, ecological and economics impacts in long term. In sum, What are the strategies proposal in order to promote and advancing toward a real application of the results and sustainable development as a total system?.

Author Response

See attached file

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The correction of the article basically solved all the previous problematic points of researching and information presentation. The article has become relevant, "friendly" to the reader in the sense of providing information. The performed analysis can be used by other authors in order to analyze the same problem in other areas within the framework of this topic.

Reviewer 2 Report

The paper was improved significantly, so I recommend accepting it for publication. However, I was not convinced by the Authors, why is acceptable to neglect BEVs in the analysis. In Europe, it is a trend using BEVs in urban public transportation, while hydrogen is rather just an option, it is used more widespread in case of replace diesel-fuelled trains in non-electrified railway tracks.