The Food, Energy, and Water Nexus through the Lens of Electric Vehicle Adoption and Ethanol Consumption in the United States

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript touches upon the important topic of moving towards a more sustainable, renewable future as we transition from fossil-fuel-based to electric vehicles. It is certainly valuable to investigate the implications to the corn ethanol sector across the domains of the food, energy, and water nexus. A key feature of this work is that the authors have considered various scenarios triggered by the growth of EV sales, allowing for a more holistic assessment. The interactive app is a great addition to better understand/visualize the authors' work. I recommend the manuscript for approval. The feedback below are questions that need further investigation. Not required to be addressed now, however, these are important for comprehensiveness to complement this work.

1) While the net income of farmers as PV owners is expected to be higher, it is important to understand the feasibility of this undertaking. What are some of the roadblocks that farmers could experience before they find higher incomes?

2) Similarly, we need to make a stronger argument for why farmers will choose the PV lease route considering it will reduce their net income. Is this at all a possibility that farmers will undertake? What will it take to convince them?

3) The direct employment/job distribution system will change. How to ensure that people are trained to take on the newer roles? How would the government need to get involved to ensure people don't lose jobs and can in fact sustain the demand growth in certain skills?

4) I liked the assessment regarding reduction in demand for irrigation water. The next step would be a deeper geographic assessment to identify which farms/regions are most in need to conserve irrigation water and optimize the savings. The next step here would be to understand if those farms/regions are sustainable from the POV of building solar PV farms. The intersection of both is perhaps ideal in the FEW nexus.

My hope is that these questions stoke your curiosity to take the work one level further and deeper especially considering the need today to move towards sustainability

Author Response

Reviewer 1

The manuscript touches upon the important topic of moving towards a more sustainable, renewable future as we transition from fossil-fuel-based to electric vehicles. It is certainly valuable to investigate the implications to the corn ethanol sector across the domains of the food, energy, and water nexus. A key feature of this work is that the authors have considered various scenarios triggered by the growth of EV sales, allowing for a more holistic assessment. The interactive app is a great addition to better understand/visualize the authors' work. I recommend the manuscript for approval. The feedback below are questions that need further investigation. Not required to be addressed now, however, these are important for comprehensiveness to complement this work.

Thank you for the positive comments about the manuscript and we are glad that you appreciated the value-added of the app.

There are several comments by the referees on the economic considerations that we have presented here. In the revised manuscript, we have made clear that this should be considered an indicative calculation only, as the overall benefits and to whom they might accrue, will depend heavily on ownership structures for solar PV.

1) While the net income of farmers as PV owners is expected to be higher, it is important to understand the feasibility of this undertaking. What are some of the roadblocks that farmers could experience before they find higher incomes?

In the paragraph describing this option, we have added this sentence: “This pathway would be considerably more complicated for a farm owner to follow, but represents at a basic level the potential overall macroeconomic benefits of solar PV as opposed to ethanol production.”

2) Similarly, we need to make a stronger argument for why farmers will choose the PV lease route considering it will reduce their net income. Is this at all a possibility that farmers will undertake? What will it take to convince them?

This “PV lease” case might be considered the simplest example. A farmer leases a fraction of land that had been  previously used for ethanol (and now will not be, according to the scenario assumption). In the final paragraph of Section 3.7, we qualified this result by pointing out that it is unlikely that the farmer would simply leave land idle (unless incentivized through other programs that would go beyond the scope of this analysis).

3) The direct employment/job distribution system will change. How to ensure that people are trained to take on the newer roles? How would the government need to get involved to ensure people don't lose jobs and can in fact sustain the demand growth in certain skills?

This is an important point, although it goes beyond the scope of this analysis. We have added a paragraph, “An important component of the energy system transformation of which the move from liquid fuels to low-emissions electricity is a part, is to facilitate a “just transition,” an effort that will likely require significant governmental policy interventions as well as collaborations with industrial and commercial partners [47]. That is, although we show consequences for employment in Figure 9, hidden behind the totals are differing skills that may be necessary. On the other hand, since the total employment increases in the short- to medium-term, the main co-benefit of a switch in transportation fuels is an increase in jobs and not a drastic and rapid decrease in the corn-ethanol sector.”

4) I liked the assessment regarding reduction in demand for irrigation water. The next step would be a deeper geographic assessment to identify which farms/regions are most in need to conserve irrigation water and optimize the savings. The next step here would be to understand if those farms/regions are sustainable from the POV of building solar PV farms. The intersection of both is perhaps ideal in the FEW nexus.

We agree that there would have to be a deeper analysis done to determine exactly in which regions the most advantage would be gained by reducing corn-ethanol production, in terms of water savings. We also believe that such an analysis, which would move much more into a specific and sensitive policymaking direction is beyond the scope of this paper.

My hope is that these questions stoke your curiosity to take the work one level further and deeper especially considering the need today to move towards sustainability

Reviewer 2 Report

Comments and Suggestions for Authors

The paper discusses future scenarios of EV adoption and its impacts on the corn-ethanol economy. The paper is well written and provides useful data in order to convince corn producer states in the US that the shift from ICEV to EV can also be profitable to them (as presented in figure 9, where the income of farms who shift from corn production to photovoltaic generation can drastically increase over the years).

1- It is not clear if the data used to create Figure 9 also takes into consideration all the costs involved in the shift from corn producer farms to become PV generation companies - which must be much higher than passively leasing the farms to PV companies (as in Figure 8).

2- It is also not clear if the data used to create Figure 9 considers the stochastic nature of PV generation and the necessity of investissements in energy storage equipment (in order to buffer the variability in the generated power).

3- Perhaps the authors could give more information about the interactive app.
I am not sure if the mathematical models used in order to produce the plots would be of the interest for the readers of Sustainability (which might reach a broader audience than Electrical/Energy engineering) - but, from the point of view of reproducibility in a scientific paper, perhaps the authors could present these equations in the Appendix.

Author Response

Reviewer 2

The paper discusses future scenarios of EV adoption and its impacts on the corn-ethanol economy. The paper is well written and provides useful data in order to convince corn producer states in the US that the shift from ICEV to EV can also be profitable to them (as presented in figure 9, where the income of farms who shift from corn production to photovoltaic generation can drastically increase over the years).

Thank you for the positive feedback on the paper.

1- It is not clear if the data used to create Figure 9 also takes into consideration all the costs involved in the shift from corn producer farms to become PV generation companies - which must be much higher than passively leasing the farms to PV companies (as in Figure 8).

(Note that this is now Fig. 8 in the revised manuscript due to the deletion of Fig. 4) The response we would provide here is the same as to comment  1) of reviewer #1:

(Referencing the “owner/developer” option) In the paragraph describing this option, we have added this sentence: “This pathway would be considerably more complicated for a farm owner to follow, but represents at a basic level the potential overall macroeconomic benefits of solar PV as opposed to ethanol production.”

In addition, we have added the sentence to this section, “There is also uncertainty in the available income-generating models for farmers through solar PV electricity generation. Therefore, the two cases described in this section should be viewed as only indicative of potential alternative income streams to ethanol.”

2- It is also not clear if the data used to create Figure 9 considers the stochastic nature of PV generation and the necessity of investissements in energy storage equipment (in order to buffer the variability in the generated power).

Although an interesting and important topic in itself, the variable nature of solar PV and resulting requirements for energy storage are not important for this work.  We are looking at marginal substitutions of electricity for fossil fuel transportation energy, and therefore have an implicit assumption that the grid will be stable and able to supply energy. Furthermore, our arguments are not made at the level of the time-dependance of energy supply and demand, but only for an overall yearly demand for electricity to give an indication of the feasibility of generating enough new electricity for increasing EVs even with a small fraction of land currently used for transportation fuels.

3- Perhaps the authors could give more information about the interactive app.
I am not sure if the mathematical models used in order to produce the plots would be of the interest for the readers of Sustainability (which might reach a broader audience than Electrical/Energy engineering) - but, from the point of view of reproducibility in a scientific paper, perhaps the authors could present these equations in the Appendix.

In this case, we feel that presenting the details of the model  in the paper are not as important as the fact that we have included a link to the repository in which those interested can access  the spreadsheet model used to generate the main results, as well as the Python code used to create the app.

Reviewer 3 Report

Comments and Suggestions for Authors

·        The abstract needs a major restructure. For example, the last sentence is 5 lines long, with so many connections and unfamiliar usage of words.

·        Furthermore, I got lost reading through the abstract about what this paper is about, and how your goals have been achieved.

·        Always remember the best way to construct an abstract is using the IMRaD structure: Introduction, Methods, Results and Discussion.

·        In the introduction I would break the paragraph at line 83 with the word “We show here” and make sure you highlight the contributions of the paper in a separate paragraph.

·        In the final paragraph of section I, you may add the section numbers you are referring to.

·        The first statement in section 2 was very confusing, I may suggest the following as an example as much as what I understood from your paper “In this paper, we begin with two key assumptions. First, we anticipate a robust increase in the sales of electric vehicles. Second, we recognize that there will be a lag before this surge in sales leads to a corresponding growth in the size of the electric vehicle fleet.”

·        Figure 1 bottom which should be named b and the top to be a, needs a Y-axis label. Same for Figure 7.

·        I’m not sure if Figure 4 adds something to the paper.

 

·        Please explain how and why the farmer’s income would drop by half. And how this can be rectified. Figures 8 and 9 need to be better explained, it is not clear at all what you are presenting. 

·        You may also consider the concept of Net-Zero Energy and automation of Biofuel productions such as in the following works:
- W. W. Saad, A. Hebala and H. A. Ashour, "Net-zero-energy automated bio-diesel production unit," 2017 Intl Conf on Advanced Control Circuits Systems (ACCS) Systems & 2017 Intl Conf on New Paradigms in Electronics & Information Technology (PEIT), Alexandria, Egypt, 2017, pp. 79-84, doi: 10.1109/ACCS-PEIT.2017.8303023. 

- M. Ferraro, F. Sergi, V. Antonucci, F. Guarino, G. Tumminia and M. Cellura, "Load match and grid interaction optimization of a net zero energy building through electricity storage: An Italian case-study", EEEIC 2016-Int. Conf. Environ. Electr. Eng., pp. 4-8, 2016.

 

Comments on the Quality of English Language

·        The abstract needs a major restructure. For example, the last sentence is 5 lines long, with so many connections and unfamiliar usage of words. There are many similar incidents of long sentences or uncommon words being used. 

Author Response

Reviewer 3

• The abstract needs a major restructure. For example, the last sentence is 5 lines long, with so many connections and unfamiliar usage of words.

This has been edited

• Furthermore, I got lost reading through the abstract about what this paper is about, and how your goals have been achieved.

Thank you for this very useful comment and suggestion; the abstract has now been re-written.

• Always remember the best way to construct an abstract is using the IMRaD structure: Introduction, Methods, Results and Discussion.

The abstract has now been re-written to follow this model.

• In the introduction I would break the paragraph at line 83 with the word “We show here” and make sure you highlight the contributions of the paper in a separate paragraph.

We have rewritten this paragraph to emphasize more clearly the contributions of the paper.

• In the final paragraph of section I, you may add the section numbers you are referring to.

This has now been done.

• The first statement in section 2 was very confusing, I may suggest the following as an example as much as what I understood from your paper “In this paper, we begin with two key assumptions. First, we anticipate a robust increase in the sales of electric vehicles. Second, we recognize that there will be a lag before this surge in sales leads to a corresponding growth in the size of the electric vehicle fleet.”

A change has been made along the lines suggested.

• Figure 1 bottom which should be named b and the top to be a, needs a Y-axis label. Same for Figure 7.

Figure 1 has now been changed, as have Figs. 6 and 9 (new numbers for these)

• I’m not sure if Figure 4 adds something to the paper.

Agreed; we have cut Figure 4 and renumbered all subsequent figures and references.

• Please explain how and why the farmer’s income would drop by half. And how this can be rectified. Figures 8 and 9 need to be better explained, it is not clear at all what you are presenting. 
  
  

We have now added additional explanation of these Figures (now  Figure 7 and Figure 8 in the revised manuscript due to the elimination of Figure 4 from the original submission).

• 
  You may also consider the concept of Net-Zero Energy and automation of Biofuel productions such as in the following works:
  - W. W. Saad, A. Hebala and H. A. Ashour, "Net-zero-energy automated bio-diesel production unit," 2017 Intl Conf on Advanced Control Circuits Systems (ACCS) Systems & 2017 Intl Conf on New Paradigms in Electronics & Information Technology (PEIT), Alexandria, Egypt, 2017, pp. 79-84, doi: 10.1109/ACCS-PEIT.2017.8303023. 

- M. Ferraro, F. Sergi, V. Antonucci, F. Guarino, G. Tumminia and M. Cellura, "Load match and grid interaction optimization of a net zero energy building through electricity storage: An Italian case-study", EEEIC 2016-Int. Conf. Environ. Electr. Eng., pp. 4-8, 2016.

I downloaded and read through these papers, but did not find them to be directly relevant for this work, as they deal with bio-diesel and with building energy consumption. Certainly interesting topics, but we have tried to cite some quite recent works that also include an overview of relevant past references.

• The abstract needs a major restructure. For example, the last sentence is 5 lines long, with so many connections and unfamiliar usage of words. There are many similar incidents of long sentences or uncommon words being used. 

We have edited the abstract and several other places in the manuscript.