Territorial Inequalities, Ecological and Material Footprints of the Energy Transition: Case Study of the Cantabrian-Mediterranean Bioregion

Round 1

Reviewer 1 Report

This article is devoted to the topical issue of the study of a set of indicators (criteria) to ensure an effective energy transition on the example of a Bioregion in Spain. However, the reviewer has a number of questions and recommendations that the authors need to answer:

1. It is recommended to add the specific region for which the study was conducted to the title of the article

2. Abstract: briefly describe the aim and problems of this study

3. Abstract: briefly present the research methodology

4. Introduction: clearly describe the goal and objectives of the study

5. Introduction: briefly present the specifics of each scenario

6. Introduction: describe the features of the energy transition in Spain (at the legislative level, methodological aspects, as well as current practical experience)

7. Introduction: to review similar studies conducted in other countries (including EU countries, as well as Asia, America, etc.)

8. Introduction: at the end of this section, add a brief description of the article structure

9. Discussion: remove "¿" in lines 331 and 332

10. References: sources 4 and 54 are identical

11. References: review the design according to the requirements of the journal

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

There are several issues in this paper.  I enumerate below.

1.  What is the definition for Net-zero greenhouse gas emissions and decarbonization? (lines 31 and 33) There is some discussion, but it isn't helpful.  How fast is "rapid"?  How does the balancing act of "net-zero" work in theory and in practice?

2.  What exactly is "territorial and energy inequality"? (lines 43 and 44)  In fact, how do you counter territorial inequality?  Are the authors talking about resource endowments?  

3.  What is a "unit of resilience"? (line 47)  How is it measured, exactly?  Seems like there should be a lot of nuance in this, but it is simply stated and then nothing.  

4.  What does a "100% renewable electricity system" look like?   Is there a standard definition or do the authors have one?

5.  I was confused, when does the base scenario start?  (line 94).  

6.  In subsection 2.1.1. (lines 101 to 105), the authors discuss switching to electrical cars.  What is the cost of this conversion?  If the authors are making policy recommendations, this should be addressed, even with back-of-the envelope calculations.  I also do not see any serious discussion in the paper about the infrastructure changes (and costs) that must be undertaken for such a switch.  

7.  I have heard about "hydrogen" as a source for electricity, but I haven't heard of anything serious.  Is this technology there? (line 109)  Puts the current energy situation in Europe in perspective if this technology is available and there is no real mention in the media.

8. What is the current mix for heating, hot water, and cooking? (lines 112 and 113)  And again, what is the conversion cost?

9. In lines 135 to 140, the authors mention studies by Jacobson and the European Commission.  Are these the only two ways of looking at renewable energy systems for the area?  I would think there are many ways of making calculations, and I am still no clear how this done.  The same applies for the ecological footprint (subsection 2.3).  There are many calculators out there, why did the authors use the one mentioned in the paper?  

10.  In line 186, the authors say minerals are "common goods"  They are, by definition, private goods.  They are rival and excludable.  Is the assumption of them being "common" (rival but not excludable) from whatever model they are using?  How does categorizing them properly affect their model?  I would assume, given some discussion later, that their price would increase as scarcity increases.  This is why adding costs in the analysis is helpful.  

11.  Is there some math model for all the "scenarios"?  Is there a conceptual model that illustrates how all items are related and used to create some conclusion?  Why is this not in the paper?  

12.  What is the point of Figure 3?  Are the authors positing something?  The authors mention that it illustrate "inverse correlation".  What do they mean by this?  Is it an inverse relationship instead?  If it is an inverse correlation, show me the numbers.

13.  In line 257, instead of "studious" it should be "studies".

14.  Where do the numbers for Figure 7 come from?  How is it being determined (again, there is no model!)

15.  For figures 8 and 9, is there a map for potential for solar, wind, etc. that can be used to see if it may match the predictions?  

16.  For all scenarios, what will the price to consumers be?  I imagine that will be important in determining the success of these policies, unless they are "imposed" on households.  

17.  Where are the numbers from lines 292 to 293 from?  How were they calculated?  What were the assumptions?  Any idea on the costs?  

18.  The paragraph in lines 300 to 303 imply that the policy scenarios are not feasible based on resource constraints. Is this correct?  If so, did the authors create a scenario that takes this critical limitation in mind?

19.  In lines 359 to 360, the authors mention "increased inequalities".  What are these inequalities?  Are they economic inequalities or are they as a result of imbalances between Supply and Demand (market failure)? 

20.  Can the PV potential described in lines 372 to 373 able to meet household level demand?  How were these numbers derived?  Is a citation missing?

21.  What do the authors mean in the sentence that starts at the end of line 378 and goes to 380?  It makes no sense.

22.  For the scenarios, what are the underlying socio-economic assumptions?  What are the assumptions with respect to changes in household and business behavior?  What are the assumptions with respect to population changes?  

Author Response

Please see the attachment

There are several issues in this paper.  I enumerate below.

Dear Reviewer, thank you very much for your time reviewing this paper. We would also like to thank you for your comments which helped us to improve the quality of the paper. We have gone through most of the document, restructured the document placing the focus on the indicators, and making more visual the results in order to improve the quality of the paper as you have recommended us.

Regarding all your proposal about the costs. We would like to point that We focus on the impacts of the energy transition and not on its economic costs. Regarding the costs of a 100% renewable electricity system, we estimated them taking into account the downward trend in the prices of renewable technologies, the results were in the same order of magnitude as those obtained in some of the cited articles. But these estimations have become totally outdated during the last year. We believe that it is very difficult to estimate the costs of a 100% renewable system for the year 2050 due to the uncertainty and volatility that exists around the prices of materials and their supply-demand relationship. In order to clarify it we have added this sentence at the end of the new section 3.3 Model assumptions:

Cost constraints have not been considered because we would incorporate considera-ble uncertainty in the model due to the recent high price volatilities of raw materials [54] and renewable technologies [13].

1. What is the definition for Net-zero greenhouse gas emissions and decarbonization? (lines 31 and 33) There is some discussion, but it isn't helpful.  How fast is "rapid"?  How does the balancing act of "net-zero" work in theory and in practice?

net zero means cutting greenhouse gas emissions to as close to zero as possible, with any remaining emissions re-absorbed from the atmosphere, by oceans and forests for instance. (in the case of the cited reference, Europe plans too the use of Carbon capture methods).

Decarbonization: refers to the process of reducing carbon dioxide (CO2) emissions resulting from human activity in the atmosphere.

Rapid is used because the goal to be carbon neutral is 2050.

To make it clearer we have changed the first paragraph:

During the 21st United Nations Framework Convention on Climate Change in Paris it was internationally agreed to keep global warming well below 2°C [1]. In this respect, the European Union aims to be climate-neutral by 2050, with net-zero greenhouse gas emissions [2]. This means a shift from fossil fuels, which are greenhouse gas emitters, to-ward less polluting renewable energy sources (RES), where electrification plays a key role [3]. This shift is also called decarbonization as it reduces the carbon dioxide equivalent emissions which is the metric measured of greenhouse gases [4].

2. What exactly is "territorial and energy inequality"? (lines 43 and 44)  In fact, how do you counter territorial inequality?  Are the authors talking about resource endowments?  

We are referring to the situation of energy inequality (and territory) that is beginning to arise, where there are energy-consuming territories that barely have installed renewable power, due to various negative factors that these technologies have, such as worsening of the landscape, tourism, etc. Compared to other territories with a smaller population that are producing renewable energy much higher than their consumption, causing demonstrations in defense of the territory against new installations.

In addition, the most populated regions tend to have a higher GDP than the less populated regions, which, added to the relationship between energy consumption and GDP, can cause higher inequalities and not only energy or occupation of the territory.

We add this sentence to explain it in section 4.1. where we explain the results of energy self-sufficiency

2. An emerging imbalance between electricity production and consumption in auton-omous communities could lead to increased inequalities. The least populated au-tonomous communities would generate energy for the most populated ones, allow-ing its higher development and attracting more population.

We also add this paragraph in lines 436 to 441:

Suppose this installation trend is replicated elsewhere, with rural and unpopulated regions supplying energy necessities of urban and populated regions. In that case, it may cause significant imbalances between autonomous communities or territories, with seri-ous social problems, as has already occurred in the mining case described in the Global Atlas of Environmental Justice [90], raising a global concern about energy colonialism in the energy transition [91].

3. What is a "unit of resilience"? (line 47)  How is it measured, exactly?  Seems like there should be a lot of nuance in this, but it is simply stated and then nothing.  

It is stated in the cited reference. It is an idea original from the Spanish chapter of the Club of Rome and “Fundación Foros de la Concordia”. They refer to resilience due to the fact that the Bioregion has sufficient renewable resources as a whole, to adapt to the energy transformation towards renewable sources necessary in the face of the climate emergency. And that when a external event, or fault, or lack of resource occurs in a territory the rest help.

4. What does a "100% renewable electricity system" look like?   Is there a standard definition or do the authors have one?

A 100% renewable electrical system is a system that produces electrical energy from renewable sources, these sources can be, for example, the sun, wind, biomass, biogas, geothermal, hydraulic, tidal...

5. I was confused, when does the base scenario start?  (line 94).  

We refer it as the current energy situation. We have changed the name to Reference scenario for better understanding, and structured the paper in a different manner. Section 3 Describes the case of the Bioregion indicating that the reference scenario is the current situation.

6. In subsection 2.1.1. (lines 101 to 105), the authors discuss switching to electrical cars.  What is the cost of this conversion?  If the authors are making policy recommendations, this should be addressed, even with back-of-the envelope calculations.  I also do not see any serious discussion in the paper about the infrastructure changes (and costs) that must be undertaken for such a switch.  

As metioned before we do not evaluate costs.

We have evaluated what land transport complete electrification would mean concerning the impact on the demand for materials. Because the industry, the governments and different reports are committed to the electrification of land transport.

We evaluate the demand for materials for the necessary infrastructures too. We have calculated the necessary power in the distribution and transport lines to satisfy the new electrical demands. We add this sentence 3.3 Model assumptions when talking about limitations and cost constraints.

We have also considered distribution and transmission line materials requirements that guarantee an appropriate interconnection and electricity distribution.

7. I have heard about "hydrogen" as a source for electricity, but I haven't heard of anything serious.  Is this technology there? (line 109)  Puts the current energy situation in Europe in perspective if this technology is available and there is no real mention in the media.

Due to the fact that the European Commission's industrial transformation report still had a high percentage of fossil fuels depending on carbon capture methods to have a net zero emissions balance, we have decided to supply these energy sources with biofuels in a sustainable way and hydrogen produced with renewable sources. Currently there are metallurgical industries that are using hydrogen as a source of energy to produce steel.

We have changed the sentence to this one to clarify: And added it on Table 2, Assumptions.

Replacement of fossil fuel energy sources considered on the 2050 European Commission Reference Scenario for industry [51] by biofuels (mainly biogas) and hydrogen. A 80% electrolysis efficiency for hydrogen production.

8. What is the current mix for heating, hot water, and cooking? (lines 112 and 113)  And again, what is the conversion cost?

The current mix can be found in reference 39. Units in ktoe. This information is available in supplementary material with energy conversion.

Heat pumps COP for heating and hot water production is 4.2. Cooking with oil products and Gas is changed by induction hobs with a 52% higher efficiency.

9. In lines 135 to 140, the authors mention studies by Jacobson and the European Commission.  Are these the only two ways of looking at renewable energy systems for the area?  I would think there are many ways of making calculations, and I am still no clear how this done.  The same applies for the ecological footprint (subsection 2.3).  There are many calculators out there, why did the authors use the one mentioned in the paper?  

We compare our results with studies cited as they have been validated. There are other studies with which we compare the results and are similar. There are no many studies that simulate the case of Spain. We add a comment in Assumptions as technical limitations and we add in the supplementary material the comparison.

We did the calculations by comparing energy demands with renewable production, always having a higher production than the demand, with an annual energy overproduction of 38%.Data is supplied in the supplementary material in an Excel.

We selected the mentioned article because it is the previous study in which an evaluation of the ecological footprint in the bioregion is made. There are no more jobs where ecological footprints are made for the same bioregion.

10. In line 186, the authors say minerals are "common goods"  They are, by definition, private goods.  They are rival and excludable.  Is the assumption of them being "common" (rival but not excludable) from whatever model they are using?  How does categorizing them properly affect their model?  I would assume, given some discussion later, that their price would increase as scarcity increases.  This is why adding costs in the analysis is helpful.  

We have changed the sentence by removing the word common goods as it can lead to confusion, it was a consideration to explain the subsequent comparison. We have transformed all the section 2.3.  in order to clarify it better:

11. Is there some math model for all the "scenarios"?  Is there a conceptual model that illustrates how all items are related and used to create some conclusion?  Why is this not in the paper?  

It is explained in the methodology, data collected is shown in supplementary material. We have added more information in the supplementary material to clarify it better.

12. What is the point of Figure 3?  Are the authors positing something?  The authors mention that it illustrate "inverse correlation".  What do they mean by this?  Is it an inverse relationship instead?  If it is an inverse correlation, show me the numbers.

We have changed the sentence, we do not use the correlation term, but we use the relationship term:

We want to illustrate the existing trend in installing renewable energies, which is being installed in regions with a lower population density. This same trend is expected in the coming years, according to the planning of the transmission network manager. Therefore, we have used this same installation trend (where it is installed in the least populated regions) for the 2030 and 2050 scenarios.

13. In line 257, instead of "studious" it should be "studies".

Thanks, corrected.

14. Where do the numbers for Figure 7 come from?  How is it being determined (again, there is no model!)

Our model is an energy balance. We did the calculations by comparing energy demands with renewable production, always having a higher production than the demand, with an annual energy overproduction of 38%. we need that installed power due to the production hours of each technology considered. In addition to taking into account the renewable production of each geographical situation.

We add more information about energy demands for the scenario and capacity factors considered in the supplementary material.

15. For figures 8 and 9, is there a map for potential for solar, wind, etc. that can be used to see if it may match the predictions?  

Yes, we base on the references 74 to 77. We have added resources considered in the supplementary material.

We have compared the renewable potential of each autonomous community with the demands. For example, in the case of wind power, km2 with a wind speed greater than 6 m/s in each autonomous community. For a power density of 6 MW/km2, If an autonomous community did not have sufficient wind potential, it would be administered by another if it did have enough. The same has been done for biomass and biogas. In the case of solar, it has been considered that there is no resource restriction, but it has been evaluated the building rooftop potentials.

16. For all scenarios, what will the price to consumers be?  I imagine that will be important in determining the success of these policies, unless they are "imposed" on households.  

As mentioned before, we decided not to include cost estimation.

17. Where are the numbers from lines 292 to 293 from?  How were they calculated?  What were the assumptions?  Any idea on the costs?  

Multiplying the number of vehicles, necessary renewable power, storage, distribution lines and so on by the material needs of each technology.

The data on the material needs of each technology is shown in the additional material, in addition to the vehicle fleet, and the needs for each scenario.

18. The paragraph in lines 300 to 303 imply that the policy scenarios are not feasible based on resource constraints. Is this correct?  If so, did the authors create a scenario that takes this critical limitation in mind?

Yes it is correct.

We are working on it. Future work is oriented toward reaching that goals for the Bioregion. Evaluating ecological, material, and water footprint in a self-sufficiency energy scenario.

19. In lines 359 to 360, the authors mention "increased inequalities".  What are these inequalities?  Are they economic inequalities or are they as a result of imbalances between Supply and Demand (market failure)? 

We are referring to the situation of energy inequality (and territory) that is beginning to arise, where there are energy-consuming territories that barely have installed renewable power, due to various negative factors that these technologies have, such as worsening of the landscape, tourism, etc. Compared to other territories with a smaller population that are producing renewable energy much higher than their consumption, causing demonstrations in defense of the territory against new installations.

In addition, the most populated regions tend to have a higher GDP than the less populated regions, which, added to the relationship between energy consumption and GDP, can cause higher inequalities and not only energy or occupation of the territory.

We add this sentence to explain it in section 4.1. where we explain the results of energy self-sufficiency

2. An emerging imbalance between electricity production and consumption in auton-omous communities could lead to increased inequalities. The least populated au-tonomous communities would generate energy for the most populated ones, allow-ing its higher development and attracting more population.

We also add this paragraph in lines 436 to 441:

Suppose this installation trend is replicated elsewhere, with rural and unpopulated regions supplying energy necessities of urban and populated regions. In that case, it may cause significant imbalances between autonomous communities or territories, with seri-ous social problems, as has already occurred in the mining case described in the Global Atlas of Environmental Justice [90], raising a global concern about energy colonialism in the energy transition [91].

20. Can the PV potential described in lines 372 to 373 able to meet household level demand?  How were these numbers derived?  Is a citation missing?

References 77 and 76. cited in table 1 We add the cites at the end of the sentence for better understanding and clarify the sentence. And add the resources in the supplementary material

Moreover, Moreover, PV potential installation on building roofs is between 30% [77] and 51% [76] of all PV power capacity needed in 2050 scenarios

21. What do the authors mean in the sentence that starts at the end of line 378 and goes to 380?  It makes no sense.

We refer to the fact that solar and photovoltaic energy are not manageable, and the manageable energies available to the bioregion are less than those in the Spanish models. That is why we have a higher overproduction.

We have added a limitations part and added the supplementary material the comparison among studies.

In model assumptions lines 278 to 292:

It is necessary to point out some limitations of our simulations. We assume a perfect electricity transmission with no congestion nor frequency regulations and perfect match-ing between energy generation, energy storage and energy demand. Furthermore, there are uncertainties in extreme weather events where energy demands and production may vary. To address this uncertainty, we are assuming an energy overproduction to guarantee that energy demand can always be supplied. We have also considered distribution and trans-mission line materials requirements that guarantee an appropriate interconnection and electricity distribution.

We assume that these limitations do not change the results significantly, since we have compared the electrical power system of the Bioregion for the 2050 scenario with others already proven for Spain. More detailed information is shown in the supplemen-tary material.

In the supplementary material:

In order to validate the model, Figure S1 shows the electrical power system of the Bi-oregion for the 2050 scenario compared with those proposed by Jacobson [5] and the Eu-ropean Commission [45] for Spain. Comparatively, hydropower production is lower in our model because of the Bioregion’s hydrological characteristics. In addition, thermal power production from renewable sources is lower when considering the Bioregion’s re-newable biomass and biogas production capacities. Thus, we have modelled a higher overproduction, which is the ratio of energy production to energy demand, due to the lower availability of manageable energy

22. For the scenarios, what are the underlying socio-economic assumptions?  What are the assumptions with respect to changes in household and business behavior?  What are the assumptions with respect to population changes?  

We are considering that there are no changes in the population's behavior. Only technological changes are made, replacing energy sources with renewables, replacing combustion vehicles with electric vehicles, replacing fossil fuel heating with heat pumps or solar thermal, and better building insulation (as explained in methodology).

For population changes and activity we consider references: [45], [50], [72]

We consider economic growth in GDP (1.5% annual but an elasticity factor of 0.2) and transport activity for each mode of transport expected by the EC model for Spain.

We consider the population growth expected by the National Institute of Statistics (5%) [72].

References

1. United Nations. Paris agreement. In proceedings of the 21st conference parties, Paris, France, (11 december 2015). http://dx.doi.org/FCCC/CP/ 2015/L.9
2. EU Commission. Long-term strategy for 2050. Available online: https://ec.europa.eu/clima/eu-action/climate-strategies-targets/2050-long-term-strategy_es (accessed on 15 June 2022).
3. Net Zero by 2050, A Roadmap for the Global Energy Sector; International Energy Agency: Paris, France, 2021.
4. EC Comission. Glosary: Carbon dioxide equivalent. 2022. Available online: https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Carbon_dioxide_equivalent#:~:text=A%20carbon%20dioxide%20equivalent%20or,with%20the%20same%20global%20warming (accessed on 15 September 2022).
5. Jacobson, M. Z.; Delucchi, M. A.; Cameron, M. A.; Manogaran, I. P.; Shu, Y.; Krauland v., A.-K. Impacts of Green New Deal Energy Plans on Grid Stability, Costs, Jobs, Health, and Climate in 143 countries. One Earth 1 2019, 4, 449-463. https://doi.org/10.1016/j.oneear.2019.12.003.
6. Child, M.; Bogdanov, D.; Breyer, C. The role of storage technologies for the transition to a 100% renewable energy system in Europe. Energy Procedia 2018, 155, 44-60. https://doi.org/10.1016/j.egypro.2018.11.067.
7. Estrategia de descarbonización a largo plazo 2050. Estrategia a largo plazo para una economía española, moderna, competitiva y climáticamente neutra a 2050; Ministerio para la Transición Ecológica y el Reto Demográfico: Madrid, Spain, 2020.
8. Hussain, A.; Perwez, U.; Ullah, K.; Kim, C.; Asghar, N. Long-term scenario pathways to assess the potential of best available technologies and cost reduction of avoided carbon emissions in an existing 100% renewable regional power system: A case study of Gilgit-Baltistan (GB), Pakistan. Energy 2021, 221. https://doi.org/10.1016/j.energy.2021.119855.
9. Felipe Andreu, J.; Schneider, D.; Krajačić, G. Evaluation of integration of solar energy into the district heating system of the city of Velika Gorica. Thermal Science 2016, 20, 1049-1060. https://doi.org/10.2298/TSCI151106106A.
10. Poggi, F.; Firmino, A; Amado, M. Planning renewable energy in rural areas: Impacts on occupation and land use. Energy 2018, 155, 630-640. https://doi.org/10.1016/j.energy.2018.05.009.
11. De Pascali, P.; Bagaini, A. Energy Transition and Urban Planning for Local Development. A Critical Review of the Evolution of Integrated Spatial and Energy Planning. Energies2019, 12, 35. https://doi.org/10.3390/en12010035
12. Valero, A; Valero, A.; Calvo, G. Ortego, A. Material bottlenecks in the future development of green technologies. Renewable and Sustainable Energy Reviews 2018, 178-200. https://doi.org/10.1016/j.rser.2018.05.041.
13. The Role of Critical Minerals in Clean Energy Transitions, World Energy Outlook Special Report; International Energy Agency: Paris, France, 2021.
14. Calvo, G.; Valero, A. Strategic mineral resources: Availability and future estimations for the renewable energy sector. Environmental Development 2022, 41, 100640. https://doi.org/10.1016/j.envdev.2021.100640.
15. Calvo, G.; Valero, A.; Valero, A. Thermodynamic Approach to Evaluate the Criticality of Raw Materials and Its Application through a Material Flow Analysis in Europe. Journal of Industrial Ecology 2017, 839-852, 22, https://doi.org/10.1111/jiec.12624.
16. Calvo, G.; Valero, A; Valero, A. Assessing maximum production peak and resource availability of non-fuel mineral resources: Analyzing the influence of extractable global resources. Resources, Conservation and Recycling 2017, 208-217, 125. https://doi.org/10.1016/j.resconrec.2017.06.009.
17. Ortego, A.; Calvo, G.; Valero, A; Iglesias-Émbil, M.; Valero, A.; Villacampa, M. Assessment of strategic raw materials in the automobile sector. Resources, Conservation and Recycling 2020, 161, 104968. https://doi.org/10.1016/j.resconrec.2020.104968
18. EU Commission. Critical raw material list. 2022. Available online: https://rmis.jrc.ec.europa.eu/?page=crm-list-2020-e294f6. (accessed on 10 July 2022).
19. Partington, R. Inflation in eurozone hits record 8.6% as Ukraine war continues. The Guardian. 1 July 2022. Available online: https://www.theguardian.com/business/2022/jul/01/inflation-in-eurozone-hits-record-86-as-ukraine-war-continues (accessed on 6 September 2022)
20. Caldara, D.; Conlisk, S.; Iacoviello, M.; Penn, M. The Effect of the War in Ukraine on Global Activity and Inflation; FEDS Notes. Washington: Board of Governors of the Federal Reserve System, May 27, 2022. https://doi.org/10.17016/2380-7172.3141.
21. IDAE; MITECO. Plan Nacional Integrado de Energía y Clima; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
22. Zalk, J.; Behrens, P. The spatial extent of renewable and non-renewable power generation: A review and meta-analysis of power densities and their application in the U.S. Energy Policy 2018, 123, 83-91. https://doi.org/10.1016/j.enpol.2018.08.023
23. Global Footprint Network. Ecological Footprint. 2021. Available online: https://www.footprintnetwork.org/our-work/ecological-footprint/ (accessed on 1 October 2021).
24. Global Footprint Network. Glossary. 2022. Available online: https://www.footprintnetwork.org/resources/glossary/ (accessed on 5 June 2022).
25. Valero, A; Valero, A. Thanatia, The Destiny of the Earth’s Mineral resources: A cradle –to-cradle assessment; World Sci. Publ. Co. 2014. ISBN 978-981-4273-93-0.
26. Schmidt-Bleek, F. MIPS–A universal ecological measure? Fresenius Environmental Bulletin 1993, 2, 8, 306–311.
27. Planetary Pressures–Adjusted Human Development Index (PHDI). 2022. Available online: https://hdr.undp.org/planetary-pressures-adjusted-human-development-index#/indicies/PHDI (accessed on 30 July 2022).
28. Valero, A; Valero, A.; Calvo, G. The Material Limits of Energy Transition: Thanatia; Springer Nature: Switzerland, 2021. ISBN 978-3-03078532-1.
29. Palacios, J.-L.; Calvo, G.; Valero, A.; Valero, A. The cost of mineral depletion in Latin America: An exergoecology view. Resources Policy 2018, 59, 117-124. https://doi.org/10.1016/j.resourpol.2018.06.007.
30. Palacios, J.-L.; Calvo, G.; Valero, A.; Valero, A. Exergoecology Assessment of Mineral Exports from Latin America: Beyond a Tonnage Perspective. Sustainability2018, 10, 723. https://doi.org/10.3390/su10030723.
31. Valero, A.; Valero, A.; Arauzo, I. Evolution of the decrease in mineral exergy throughout the 20th century. The case of copper in the US. Energy 2008, 33, 2, 107-115. https://doi.org/10.1016/j.energy.2007.11.007.
32. Valero, A; Valero, A. Es la entropía, estúpido!. In Bioeconomía para el siglo XXI. Actualidad de Nicholas Georgescu-Roegen.; Arenas, L.; Naredo, J. M.; Riechmann, J.; Libros de la Catarata Publ.: Madrid, Spain, 2022; pp.185-227. ISBN 978-84-1352-500-6.
33. United States Geological Survey USGS. USGS Online Publications Directory. 2022. Available online: https://pubs.usgs.gov/periodicals/mcs2022/ (accessed on 25 February 2022).
34. Grupo Aragonés del Capítulo Español del Club de Roma. Reunión 22 de septiembre biorregión cantábrico-mediterránea (Meeting September 22 Cantabrian-Mediterranean bioregion). Available online: https://www.clubderoma-aragon.org/eventos/reunion-22-de-septiembre-biorregion-cantabrico-mediterranea/ (accessed on 6 July 2021).
35. Fundación Foros de la Concordia. La biorregión Cantábrico-Mediterránea (BCM) constituye un espacio geográfico con raíces naturales, sociales e históricas comunes, que encuentra en el río Ebro su gran eje vertebrador (The Cantabrian-Mediterranean bioregion (BCM) constitutes a geographical space with common natural, social and historical roots, which finds its great backbone in the Ebro River). Available online: https://www.bioebro.org/la-biorregion/ (accessed on 25 August 2021).
36. Expansión/Datosmacro.com. El PIB de las comunidades autónomas (The GDP of the autonomous communities). Available online: https://datosmacro.expansion.com/pib/espana-comunidades-autonomas (accessed on 6 July 2021).
37. The World Bank. Consumo de energía procedente de combustibles fósiles (Energy consumption from fossil fuels). 2022. Available online: https://datos.bancomundial.org/indicator/EG.USE.COMM.FO.ZS (accessed on 20 June 2022).
38. REE; MITECO. Plan de desarrollo de la Red de Transporte de Energía Eléctrica Período 2021-2026; Red Eléctrica de España: Madrid, Spain, 2021.
39. Bistaffa, F.; Blum, C.; Cerquides, J.; Farinelli, A.; Rodríguez-Aguilar, J. A Computational Approach to Quantify the Benefits of Ridesharing for Policy Makers and Travellers. IEEE Transactions on Intelligent Transportation Systems 2021, 22, 119-130. Doi: 10.1109/TITS.2019.2954982.
40. Jonge, D. d.; Bistaffa, F.; Levy, J. A Heuristic Algorithm for Multi-Agent Vehicle Routing with Automated Negotiation. pp. 404-412. In Proceedings of the 20th International Conference on Autonomous Agents and Multiagent Systems (AAMAS), virtual event, United Kingdom, (3-7 May 2021). http://hdl.handle.net/10261/257887.
41. García-Álvarez, A.; Pérez-Martínez, P. J.; González-Franco, I. Energy Consumption and Carbon Dioxide Emissions in Rail and Road Freight Transport in Spain: A Case Study of Car Carriers and Bulk Petrochemicals. Journal of Intelligent Transportation Systems 2013, 17, 3, 233-244. https://doi.org/10.1080/15472450.2012.719456
42. Análisis del recurso. Atlas eólico de España. Estudio técnico PER 2011-2020; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2011.
43. Enevoldsen, P.; Jacobson, M. Data investigation of installed and output power densities of onshore and offshore wind turbines worldwide. Energy for sustainable development 2021, 60, 40-51. https://doi.org/10.1016/j.esd.2020.11.004.
44. Álvarez, C.; Zafra, M. Cuánto ocupan las megacentrales solares: investigadores alertan del impacto del ‘boom’ fotovoltaico. El País. 23 JAnuary 2021. Available online: https://elpais.com/clima-y-medio-ambiente/2021-01-23/cuanto-ocupan-las-megacentrales-solares-investigadores-alertan-del-impacto-del-boom-fotovoltaico.html (accessed on 5 august 2021).
45. EU Reference Scenario 2020, Energy, transport and GHG emissions - Trends 2050; European Commission: Brussels, Belgium, 2021.
46. Paula-Elena, D.; Liviu-George, M. The relationship between Income, Consumption and GDP: A Time Series, Cross-Country Analysis. Procedia Economics and Finance 2015, 23, 1535-1543. https://doi.org/10.1016/S2212-5671(15)00374-3.
47. Nguyen, T.-V.; Schnidrig, J.; Maréchal, F. An analysis of the impacts of green mobility strategies and technologies on different European energy systems. In Proceedings of ECOS 2021 - The 34th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Sicily, Italy, (28 june 2021).
48. Schnidrig, J; Nguyen, T.-V; Li, X.; Maréchal, F. A modelling framework for assessing the impact of green mobility technologies on energy systems. In Proceedings of ECOS 2021 - The 34th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Sicily, Italy, (28 june 2021).
49. García Álvarez, A.; Martín Cañizares, M. d. P. Metodología de cálculo del consumo de energía de los trenes de viajeros y actuaciones en el diseño del material rodante para su reducción; ElecRail: Madrid, Spain, 2010.
50. EU Commission. EU Reference Scenario 2020. Available online: https://ec.europa.eu/energy/data-analysis/energy-modelling/eu-reference-scenario-2020_en (accessed on 27 July 2021).
51. Hager, T.J.; Morawicki, R. Energy consumption during cooking in the residential sector of developed nations: A review. Food policy 2013, 40, 54-63. https://doi.org/10.1016/j.foodpol.2013.02.003
52. economics for energy. Escenarios para el sector energético en España 2030-2050. Vigo, Spain, 2017.
53. Estrategia a largo plazo para una economía española moderna, competitiva y climáticamente neutra en 2050. Anexos; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
54. Magdalena, R.; Calvo, G.; Valero, A. The Energy Cost of Extracting Critical Raw Materials from Tailings: The Case of Coltan. Geosciences 2022, 12, 214. https:// doi.org/10.3390/geosciences12050214.
55. Gobierno de Aragón. Boletín de Coyuntura Energética en Aragón 2018: Zaragoza, Spain, 2019.
56. Govern Illes Balears. PORTAL ENERGÈTIC (energy portal). 2021. Available online: http://www.caib.es/sites/energia/ca/publicacions_estadistiques_i_preus_de_lenergia-7491/ (accessed on 6 July 2021).
57. Instituto Catalán de Energía. Balance energético de Cataluña (catalonian energy balance). Available online: http://icaen.gencat.cat/es/energia/estadistiques/resultats/anuals/balanc_energetic/ (accessed on 6 July 2021).
58. ivace energía. Datos energéticos de la Comunitat Valenciana; Generalitat Valenciana: Valencia, Spain, 2019.
59. Área de Estudios y Planificación. EUSKADI ENERGÍA 2018, Datos energéticos; Ente Vasco de la Energía: Bilbao, Spain, 2020.
60. Datos energéticos de la C.A. de Euskadi (Energy data of Basque Country autonomous community). 2021. Available online: https://www.eustat.eus/estadisticas/tema_552/opt_1/tipo_1/ti_datos-energeticos-de-la-c-a/temas.html#el. (accessed on 6 July 2021).
61. Gobierno de Navarra. Balance Energético de Navarra; Pamplona, Spain, 2018.
62. La energía en España 2018. Ministerio para la Transición Ecológica y el Reto Demográfico: Madrid, Spain, 2020.
63. Informe sintético de indicadores de eficiencia energética en España. Año 2018; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
64. IDAE; MITECO. Consumo de Energía final (final energy consumption). Available online: http://sieeweb.idae.es/consumofinal/ (accessed on 6 July 2021).
65. El sistema eléctrico español 2018; Red Eléctrica de España: Madrid, Spain, 2019.
66. El sistema eléctrico español informe 2020, producción de energía eléctrica; Red Eléctrica de España: Madrid, Spain, 2021.
67. Ministerio de Transportes, Movilidad y Agenda Urbana. Consumo energético en el transporte por modo, tipo de combustible y tipo de tráfico (Energy consumption in transport by mode, type of fuel and type of traffic). Available online: https://apps.fomento.gob.es/BDOTLE/visorBDpop.aspx?i=314 (accessed on 14 July 2021).
68. Dirección General de Tráfico. Series históricas del parque de vehículos. Available online: https://www.dgt.es/es/seguridad-vial/estadisticas-e-indicadores/parque-vehiculos/series-historicas/ (accessed on 15 July 2021).
69. Análisis sobre los kilómetros anotados en las ITV; Dirección General de Tráfico: Madrid, Spain, 2018.
70. IDAE; MITECO. Informe anual del consumo energético año 2019; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
71. economics for energy. Estrategias para la descarbonización del transporte terrestre en España, Un análisis de escenarios. Vigo, Spain, 2020.
72. INE. Proyecciones de Población 2020–2070; Instituto Nacional de Estadística: Madrid, Spain, 2020.
73. Photovoltaic Geographical Information System. 2021. Available online: https://re.jrc.ec.europa.eu/pvg_tools/en/ (accessed on: 20 July 2021).
74. Situación y potencial de generación de biogás; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2011.
75. Evaluación del potencial de energía de la biomasa, estudio técnico PER 2011-2020; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2011.
76. Observatorio Sostenibilidad. 1 millón de tejados solares en 2025: energía rentable y accesible para los ciudadanos. Madrid, Spain, 2021.
77. Bódis, K.; Kougias, I.; Jäger-Waldau, A; Taylor, N.; Szabó, S. A high-resolution geospatial assessment of the rooftop solar photovoltaic potential in the European Union. Renewable and Sustainable Energy Reviews 2019, 114, 109309. https://doi.org/10.1016/j.rser.2019.109309
78. Azam, A.; Rafiq, M.; Shafique, M.; Zhang, H.; Yuan, J. Analyzing the effect of natural gas, nuclear energy and renewable energy on GDP and carbon emissions: A multi-variate panel data analysis. Energy 2021, 219, 119592. https://doi.org/10.1016/j.energy.2020.119592
79. KumarNarayan, P.; Narayan, S; Popp, S. A note on the long-run elasticities from the energy consumption–GDP relationship, Applied Energy 2010, 87, 3, 1054-1057. https://doi.org/10.1016/j.apenergy.2009.08.037
80. Iglesias-Émbil, M.; Valero, A.; Ortego, A.; Villacampa, M.; Vilaró, J.; Villalba, G. Raw material use in a battery electric car – a thermodynamic rarity assessment. Resources, Conservation & Recycling 2020, 158, 104820. https://doi.org/10.1016/j.resconrec.2020.104820
81. Carrara, S.; Dias, P. A.; Plazzotta, B.; Pavel, C. Raw materials demand for wind and solar PV technologies in the transition towards a decarbonized energy system; Publications Office, 2020. https://data.europa.eu/doi/10.2760/160859
82. Ashby, M.; Attwood, J.; Lord, F. Materials for Low-Carbon Power - A White Paper, 2nd ed.; Granta teaching resources, 2012.
83. García-Olivares, A.; Ballabrera-Poy, J.; García-Ladona, E; Turiel, A. A global renewable mix with proven technologies and common materials. Energy Policy 2012, 41, 561-574. https://doi.org/10.1016/j.enpol.2011.11.018.
84. Jones, H.; Moura, F.; Domingos, T. Life cycle assessment of high-speed rail: a case study in Portugal. Int J Life Cycle Assess 2017, 22, 410-422. https://doi.org/10.1007/s11367-016-1177-7.
85. Verdejo, E. Z.; Requerimientos materiales de la transmisión y distribución de la electricidad para la transición energética. Master tesis, Universidad de Valladolid, escuela de ingenierías industriales, Valladolid, Spain, 2021.
86. Manifestaciones ALIENTE (ALIENTE protests). 2022. Available online: https://aliente.org/category/campanas/manifestaciones-aliente (accessed on 30 June 2022).
87. Hernández, A.; Renovable sí, pero no así. La razón. 2021. Available online: https://www.larazon.es/opinion/20211012/jeiekwh5xfbjxcut4lc7ltglsi.html (accessed on 01 May 2022).
88. Pérez, B.P.; Díaz-Cuevas, P. Connections between Water, Energy and Landscape: The Social Acceptance in the Monachil River Valley (South of Spain). Land 2022, 11, 1203. https://doi.org/10.3390/ land11081203
89. Estado del acceso y conexión de la generación renovable eólica y solar fotovoltaica. 2022. Available online: https://www.ree.es/es/clientes/datos-acumulados-generacion-renovable (accessed on 25 June 2022).
90. Temper, L.; del Bene, D.; Martinez-Alier, J. Mapping the frontiers and front lines of global environmental justice: the EJAtlas. Journal of Political Ecology 2015. 22, 255-278. https://doi.org/10.2458/v22i1.21108.
91. Mavhunga, C.C.; Trischler, H. (Eds). Energy (and) Colonialism, Energy (In)Dependence: Africa, Europe, Greenland, North America. RCC perspectives 2014, 5. doi.org/10.5282/rcc/6554.
92. Valero, A.; Torrubia, J. Libro Blanco de la Biorregión Cantábrico-Mediterránea. Cap 4. Fundación Foros de la Concordia y Capitulo Español del Club de Roma, 2020.
93. Bruckner, T.; Bashmakov, I.; Mulugetta, Y.; Chum, H.; Navarro, A. d. l. V. ; Edmonds, J.; Faaij, A.; Fungtammasan, B.; Garg, A.; Hertwich, E.; Honnery, D.; Infield, D.; Kainuma, M.; Khennas, S.; Kim, S.; Nimir, H.; Riahi, K.; Strachan, N.; Wiser, R.; Zhang a. X. Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change; Cambridge University Press: Cambridge, United Kingdom and New York, NY, USA. 2014.
94. Ambrose, H.; Kendall, A.; Lozano, M.; Wachche, S.; Fulton, L. Trends in life cycle greenhouse gas emissions of future light duty electric vehicles. Transportation Research Part D: Transport and Environment 2020, 18, 102287, https://doi.org/10.1016/j.trd.2020.102287
95. Lee, D.; Thomas, V.M.; Brown, M.A. Electric Urban Delivery Trucks: Energy Use, Greenhouse Gas Emissions, and Cost-Effectiveness. Environmental Science & Technology 2013, 47, 14, 8022-8030. https://doi.org/10.1021/es400179w
96. Carranza, G; Nascimiento, M.D.; Fanals, J,; Febrer, J.; Valderrama, C. Life cycle assessment and economic analysis of the electric motorcycle in the city of Barcelona and the impact on air pollution. Science of the Total Environment 2022, 821, 153419 https://doi.org/10.1016/j.scitotenv.2022.153419
97. Ministerio de Consumo/EC-JRC. Sostenibilidad del consumo en España. Evaluación del impacto ambiental asociado a los patrones de consumo mediante Análisis del Ciclo de Vida; Ministerio de Consumo: Madrid, Spain, 2022.
98. Una población en crecimiento. 2022. Available online: https://www.un.org/es/global-issues/population (accessed on 2 February 2022).
99. Carnegie Europe; Open Society European Policy Institute. The EU and Climate Security: Toward Ecological Diplomacy. Carnegie Endowment for International Peace; Washington DC, USA, 2021.
100. Lallana, M.; Almazán, A.; Valero, A.; Lareo, Á. Assessing Energy Descent Scenarios for the Ecological Transition in Spain 2020–2030. Sustainability 2021, 13, 11867. https:// doi.org/10.3390/su132111867.

Author Response File: Author Response.pdf

Reviewer 3 Report

Land 1873317

The paper demonstrate an important issue regarding  energy transition in a bioregion, by presenting the territorial inequities, ecological and material footprints of the energy transition for the bioregion in Spain. Two scenarios are compared. Several suggestions are offered to the authors for their consideration when they revise the paper.

1. Only the terminologies and their brief descriptions are listed in the section 2. The authors are suggested to have the measurement methods or the analysis methodology in section 2; and hence the corresponding analysis and results can be reported.

2. Some indicators in Table 1 is not clear enough: such as "Territory equivalent", and "Renewable production vs Demand". 

3. Please revise the rare part of the title of Figure 3.

Author Response

The paper demonstrate an important issue regarding  energy transition in a bioregion, by presenting the territorial inequities, ecological and material footprints of the energy transition for the bioregion in Spain. Two scenarios are compared. Several suggestions are offered to the authors for their consideration when they revise the paper.

 Dear Reviewer, thank you very much for your time reviewing this paper. We would also like to thank you for your comments which helped us to improve the quality of the paper. We have gone through most of the document, restructured the document placing the focus on the indicators, and making more visual the results in order to improve the quality of the paper as you have recommended us.

1. Only the terminologies and their brief descriptions are listed in the section 2. The authors are suggested to have the measurement methods or the analysis methodology in section 2; and hence the corresponding analysis and results can be reported.

Thanks, we have restructured all the paper and methodology for a better understanding. Now we first describe the indicators in section 2.Methodology. Later we talk about the case study and the model assumptions. We hope that now is clearer for a better understanding.

2. Some indicators in Table 1 is not clear enough: such as "Territory equivalent", and "Renewable production vs Demand". 

Both are deleted from the table. We have restructured the paper and we present these indicators in the results with a better explaining. Subsections 4.1 to 4.2

we have changed the title of renewable production vs Demand by: Renewable electricity self-sufficiency and explained it with an equation:

2.1. Renewable energy self-sufficiency

The first indicator is renewable energy self-sufficiency. We obtain it from the ratio between renewable energy generation and energy demand, as equation 1 shows.

This indicator aims to show the degree of energy self-sufficiency of a territory with renewable sources. It has some interesting connotations since by comparing regions that form a unit, the interdependence between them can be seen. “Sacrifice regions”, meaning net energy exporter territories making available more RES-devoted land than they need domestically, can be easily detected. This, in turn, is an indication of potential social conflicts. Moreover, it is an indicator of external energy dependency and consequential vulnerabilities in a 100% renewable system.

The ideal result would be a value slightly higher than 100%, with enough surplus to cover losses.

We have explained better the concept of territory equivalent:

The ecological footprint is an internationally recognized sustainability indicator used as a standardized measure of demand for natural capital. It compares how fast resources are consumed, and waste is generated with the speed of nature to generate new resources and absorb waste measured in areas [23]. The calculation consists of converting the equivalent global biologically productive hectares to the direct and indirect consumption of energy, biomass, building materials, water, and other resources on a population basis. The per capita biological capacity available on Earth is estimated to be 1.6 gha in 2019, and the ratio of the humanity footprint to the per capita biological capacity is 1.75 [23], which implies humanity’s total ecological footprint of 1.75 planet Earths.

Results are shown with the concept of “Planet Equivalent” [24]. However, instead of the ratio of an individual’s (or country’s per capita) footprint to the per capita biological capacity available on Earth, we have used the ratio of the territory’s ecological footprint to the territory’s biocapacity. We have named the result “Territory Equivalent”. A value of 2 means that the Bioregion needs 2 times its territory biocapacity to compensate for its eco-logical footprint.

We have changed too labels in figures.

3. Please revise the rare part of the title of Figure 3.

We have changed the title and the axis title for more clarity. What do you mean with rare part?

Title: Renewable power generation capacity and population density relationship by 2026, elaborated with data from [38].

References

1. United Nations. Paris agreement. In proceedings of the 21st conference parties, Paris, France, (11 december 2015). http://dx.doi.org/FCCC/CP/ 2015/L.9
2. EU Commission. Long-term strategy for 2050. Available online: https://ec.europa.eu/clima/eu-action/climate-strategies-targets/2050-long-term-strategy_es (accessed on 15 June 2022).
3. Net Zero by 2050, A Roadmap for the Global Energy Sector; International Energy Agency: Paris, France, 2021.
4. EC Comission. Glosary: Carbon dioxide equivalent. 2022. Available online: https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Carbon_dioxide_equivalent#:~:text=A%20carbon%20dioxide%20equivalent%20or,with%20the%20same%20global%20warming (accessed on 15 September 2022).
5. Jacobson, M. Z.; Delucchi, M. A.; Cameron, M. A.; Manogaran, I. P.; Shu, Y.; Krauland v., A.-K. Impacts of Green New Deal Energy Plans on Grid Stability, Costs, Jobs, Health, and Climate in 143 countries. One Earth 1 2019, 4, 449-463. https://doi.org/10.1016/j.oneear.2019.12.003.
6. Child, M.; Bogdanov, D.; Breyer, C. The role of storage technologies for the transition to a 100% renewable energy system in Europe. Energy Procedia 2018, 155, 44-60. https://doi.org/10.1016/j.egypro.2018.11.067.
7. Estrategia de descarbonización a largo plazo 2050. Estrategia a largo plazo para una economía española, moderna, competitiva y climáticamente neutra a 2050; Ministerio para la Transición Ecológica y el Reto Demográfico: Madrid, Spain, 2020.
8. Hussain, A.; Perwez, U.; Ullah, K.; Kim, C.; Asghar, N. Long-term scenario pathways to assess the potential of best available technologies and cost reduction of avoided carbon emissions in an existing 100% renewable regional power system: A case study of Gilgit-Baltistan (GB), Pakistan. Energy 2021, 221. https://doi.org/10.1016/j.energy.2021.119855.
9. Felipe Andreu, J.; Schneider, D.; Krajačić, G. Evaluation of integration of solar energy into the district heating system of the city of Velika Gorica. Thermal Science 2016, 20, 1049-1060. https://doi.org/10.2298/TSCI151106106A.
10. Poggi, F.; Firmino, A; Amado, M. Planning renewable energy in rural areas: Impacts on occupation and land use. Energy 2018, 155, 630-640. https://doi.org/10.1016/j.energy.2018.05.009.
11. De Pascali, P.; Bagaini, A. Energy Transition and Urban Planning for Local Development. A Critical Review of the Evolution of Integrated Spatial and Energy Planning. Energies2019, 12, 35. https://doi.org/10.3390/en12010035
12. Valero, A; Valero, A.; Calvo, G. Ortego, A. Material bottlenecks in the future development of green technologies. Renewable and Sustainable Energy Reviews 2018, 178-200. https://doi.org/10.1016/j.rser.2018.05.041.
13. The Role of Critical Minerals in Clean Energy Transitions, World Energy Outlook Special Report; International Energy Agency: Paris, France, 2021.
14. Calvo, G.; Valero, A. Strategic mineral resources: Availability and future estimations for the renewable energy sector. Environmental Development 2022, 41, 100640. https://doi.org/10.1016/j.envdev.2021.100640.
15. Calvo, G.; Valero, A.; Valero, A. Thermodynamic Approach to Evaluate the Criticality of Raw Materials and Its Application through a Material Flow Analysis in Europe. Journal of Industrial Ecology 2017, 839-852, 22, https://doi.org/10.1111/jiec.12624.
16. Calvo, G.; Valero, A; Valero, A. Assessing maximum production peak and resource availability of non-fuel mineral resources: Analyzing the influence of extractable global resources. Resources, Conservation and Recycling 2017, 208-217, 125. https://doi.org/10.1016/j.resconrec.2017.06.009.
17. Ortego, A.; Calvo, G.; Valero, A; Iglesias-Émbil, M.; Valero, A.; Villacampa, M. Assessment of strategic raw materials in the automobile sector. Resources, Conservation and Recycling 2020, 161, 104968. https://doi.org/10.1016/j.resconrec.2020.104968
18. EU Commission. Critical raw material list. 2022. Available online: https://rmis.jrc.ec.europa.eu/?page=crm-list-2020-e294f6. (accessed on 10 July 2022).
19. Partington, R. Inflation in eurozone hits record 8.6% as Ukraine war continues. The Guardian. 1 July 2022. Available online: https://www.theguardian.com/business/2022/jul/01/inflation-in-eurozone-hits-record-86-as-ukraine-war-continues (accessed on 6 September 2022)
20. Caldara, D.; Conlisk, S.; Iacoviello, M.; Penn, M. The Effect of the War in Ukraine on Global Activity and Inflation; FEDS Notes. Washington: Board of Governors of the Federal Reserve System, May 27, 2022. https://doi.org/10.17016/2380-7172.3141.
21. IDAE; MITECO. Plan Nacional Integrado de Energía y Clima; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
22. Zalk, J.; Behrens, P. The spatial extent of renewable and non-renewable power generation: A review and meta-analysis of power densities and their application in the U.S. Energy Policy 2018, 123, 83-91. https://doi.org/10.1016/j.enpol.2018.08.023
23. Global Footprint Network. Ecological Footprint. 2021. Available online: https://www.footprintnetwork.org/our-work/ecological-footprint/ (accessed on 1 October 2021).
24. Global Footprint Network. Glossary. 2022. Available online: https://www.footprintnetwork.org/resources/glossary/ (accessed on 5 June 2022).
25. Valero, A; Valero, A. Thanatia, The Destiny of the Earth’s Mineral resources: A cradle –to-cradle assessment; World Sci. Publ. Co. 2014. ISBN 978-981-4273-93-0.
26. Schmidt-Bleek, F. MIPS–A universal ecological measure? Fresenius Environmental Bulletin 1993, 2, 8, 306–311.
27. Planetary Pressures–Adjusted Human Development Index (PHDI). 2022. Available online: https://hdr.undp.org/planetary-pressures-adjusted-human-development-index#/indicies/PHDI (accessed on 30 July 2022).
28. Valero, A; Valero, A.; Calvo, G. The Material Limits of Energy Transition: Thanatia; Springer Nature: Switzerland, 2021. ISBN 978-3-03078532-1.
29. Palacios, J.-L.; Calvo, G.; Valero, A.; Valero, A. The cost of mineral depletion in Latin America: An exergoecology view. Resources Policy 2018, 59, 117-124. https://doi.org/10.1016/j.resourpol.2018.06.007.
30. Palacios, J.-L.; Calvo, G.; Valero, A.; Valero, A. Exergoecology Assessment of Mineral Exports from Latin America: Beyond a Tonnage Perspective. Sustainability2018, 10, 723. https://doi.org/10.3390/su10030723.
31. Valero, A.; Valero, A.; Arauzo, I. Evolution of the decrease in mineral exergy throughout the 20th century. The case of copper in the US. Energy 2008, 33, 2, 107-115. https://doi.org/10.1016/j.energy.2007.11.007.
32. Valero, A; Valero, A. Es la entropía, estúpido!. In Bioeconomía para el siglo XXI. Actualidad de Nicholas Georgescu-Roegen.; Arenas, L.; Naredo, J. M.; Riechmann, J.; Libros de la Catarata Publ.: Madrid, Spain, 2022; pp.185-227. ISBN 978-84-1352-500-6.
33. United States Geological Survey USGS. USGS Online Publications Directory. 2022. Available online: https://pubs.usgs.gov/periodicals/mcs2022/ (accessed on 25 February 2022).
34. Grupo Aragonés del Capítulo Español del Club de Roma. Reunión 22 de septiembre biorregión cantábrico-mediterránea (Meeting September 22 Cantabrian-Mediterranean bioregion). Available online: https://www.clubderoma-aragon.org/eventos/reunion-22-de-septiembre-biorregion-cantabrico-mediterranea/ (accessed on 6 July 2021).
35. Fundación Foros de la Concordia. La biorregión Cantábrico-Mediterránea (BCM) constituye un espacio geográfico con raíces naturales, sociales e históricas comunes, que encuentra en el río Ebro su gran eje vertebrador (The Cantabrian-Mediterranean bioregion (BCM) constitutes a geographical space with common natural, social and historical roots, which finds its great backbone in the Ebro River). Available online: https://www.bioebro.org/la-biorregion/ (accessed on 25 August 2021).
36. Expansión/Datosmacro.com. El PIB de las comunidades autónomas (The GDP of the autonomous communities). Available online: https://datosmacro.expansion.com/pib/espana-comunidades-autonomas (accessed on 6 July 2021).
37. The World Bank. Consumo de energía procedente de combustibles fósiles (Energy consumption from fossil fuels). 2022. Available online: https://datos.bancomundial.org/indicator/EG.USE.COMM.FO.ZS (accessed on 20 June 2022).
38. REE; MITECO. Plan de desarrollo de la Red de Transporte de Energía Eléctrica Período 2021-2026; Red Eléctrica de España: Madrid, Spain, 2021.
39. Bistaffa, F.; Blum, C.; Cerquides, J.; Farinelli, A.; Rodríguez-Aguilar, J. A Computational Approach to Quantify the Benefits of Ridesharing for Policy Makers and Travellers. IEEE Transactions on Intelligent Transportation Systems 2021, 22, 119-130. Doi: 10.1109/TITS.2019.2954982.
40. Jonge, D. d.; Bistaffa, F.; Levy, J. A Heuristic Algorithm for Multi-Agent Vehicle Routing with Automated Negotiation. pp. 404-412. In Proceedings of the 20th International Conference on Autonomous Agents and Multiagent Systems (AAMAS), virtual event, United Kingdom, (3-7 May 2021). http://hdl.handle.net/10261/257887.
41. García-Álvarez, A.; Pérez-Martínez, P. J.; González-Franco, I. Energy Consumption and Carbon Dioxide Emissions in Rail and Road Freight Transport in Spain: A Case Study of Car Carriers and Bulk Petrochemicals. Journal of Intelligent Transportation Systems 2013, 17, 3, 233-244. https://doi.org/10.1080/15472450.2012.719456
42. Análisis del recurso. Atlas eólico de España. Estudio técnico PER 2011-2020; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2011.
43. Enevoldsen, P.; Jacobson, M. Data investigation of installed and output power densities of onshore and offshore wind turbines worldwide. Energy for sustainable development 2021, 60, 40-51. https://doi.org/10.1016/j.esd.2020.11.004.
44. Álvarez, C.; Zafra, M. Cuánto ocupan las megacentrales solares: investigadores alertan del impacto del ‘boom’ fotovoltaico. El País. 23 JAnuary 2021. Available online: https://elpais.com/clima-y-medio-ambiente/2021-01-23/cuanto-ocupan-las-megacentrales-solares-investigadores-alertan-del-impacto-del-boom-fotovoltaico.html (accessed on 5 august 2021).
45. EU Reference Scenario 2020, Energy, transport and GHG emissions - Trends 2050; European Commission: Brussels, Belgium, 2021.
46. Paula-Elena, D.; Liviu-George, M. The relationship between Income, Consumption and GDP: A Time Series, Cross-Country Analysis. Procedia Economics and Finance 2015, 23, 1535-1543. https://doi.org/10.1016/S2212-5671(15)00374-3.
47. Nguyen, T.-V.; Schnidrig, J.; Maréchal, F. An analysis of the impacts of green mobility strategies and technologies on different European energy systems. In Proceedings of ECOS 2021 - The 34th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Sicily, Italy, (28 june 2021).
48. Schnidrig, J; Nguyen, T.-V; Li, X.; Maréchal, F. A modelling framework for assessing the impact of green mobility technologies on energy systems. In Proceedings of ECOS 2021 - The 34th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Sicily, Italy, (28 june 2021).
49. García Álvarez, A.; Martín Cañizares, M. d. P. Metodología de cálculo del consumo de energía de los trenes de viajeros y actuaciones en el diseño del material rodante para su reducción; ElecRail: Madrid, Spain, 2010.
50. EU Commission. EU Reference Scenario 2020. Available online: https://ec.europa.eu/energy/data-analysis/energy-modelling/eu-reference-scenario-2020_en (accessed on 27 July 2021).
51. Hager, T.J.; Morawicki, R. Energy consumption during cooking in the residential sector of developed nations: A review. Food policy 2013, 40, 54-63. https://doi.org/10.1016/j.foodpol.2013.02.003
52. economics for energy. Escenarios para el sector energético en España 2030-2050. Vigo, Spain, 2017.
53. Estrategia a largo plazo para una economía española moderna, competitiva y climáticamente neutra en 2050. Anexos; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
54. Magdalena, R.; Calvo, G.; Valero, A. The Energy Cost of Extracting Critical Raw Materials from Tailings: The Case of Coltan. Geosciences 2022, 12, 214. https:// doi.org/10.3390/geosciences12050214.
55. Gobierno de Aragón. Boletín de Coyuntura Energética en Aragón 2018: Zaragoza, Spain, 2019.
56. Govern Illes Balears. PORTAL ENERGÈTIC (energy portal). 2021. Available online: http://www.caib.es/sites/energia/ca/publicacions_estadistiques_i_preus_de_lenergia-7491/ (accessed on 6 July 2021).
57. Instituto Catalán de Energía. Balance energético de Cataluña (catalonian energy balance). Available online: http://icaen.gencat.cat/es/energia/estadistiques/resultats/anuals/balanc_energetic/ (accessed on 6 July 2021).
58. ivace energía. Datos energéticos de la Comunitat Valenciana; Generalitat Valenciana: Valencia, Spain, 2019.
59. Área de Estudios y Planificación. EUSKADI ENERGÍA 2018, Datos energéticos; Ente Vasco de la Energía: Bilbao, Spain, 2020.
60. Datos energéticos de la C.A. de Euskadi (Energy data of Basque Country autonomous community). 2021. Available online: https://www.eustat.eus/estadisticas/tema_552/opt_1/tipo_1/ti_datos-energeticos-de-la-c-a/temas.html#el. (accessed on 6 July 2021).
61. Gobierno de Navarra. Balance Energético de Navarra; Pamplona, Spain, 2018.
62. La energía en España 2018. Ministerio para la Transición Ecológica y el Reto Demográfico: Madrid, Spain, 2020.
63. Informe sintético de indicadores de eficiencia energética en España. Año 2018; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
64. IDAE; MITECO. Consumo de Energía final (final energy consumption). Available online: http://sieeweb.idae.es/consumofinal/ (accessed on 6 July 2021).
65. El sistema eléctrico español 2018; Red Eléctrica de España: Madrid, Spain, 2019.
66. El sistema eléctrico español informe 2020, producción de energía eléctrica; Red Eléctrica de España: Madrid, Spain, 2021.
67. Ministerio de Transportes, Movilidad y Agenda Urbana. Consumo energético en el transporte por modo, tipo de combustible y tipo de tráfico (Energy consumption in transport by mode, type of fuel and type of traffic). Available online: https://apps.fomento.gob.es/BDOTLE/visorBDpop.aspx?i=314 (accessed on 14 July 2021).
68. Dirección General de Tráfico. Series históricas del parque de vehículos. Available online: https://www.dgt.es/es/seguridad-vial/estadisticas-e-indicadores/parque-vehiculos/series-historicas/ (accessed on 15 July 2021).
69. Análisis sobre los kilómetros anotados en las ITV; Dirección General de Tráfico: Madrid, Spain, 2018.
70. IDAE; MITECO. Informe anual del consumo energético año 2019; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
71. economics for energy. Estrategias para la descarbonización del transporte terrestre en España, Un análisis de escenarios. Vigo, Spain, 2020.
72. INE. Proyecciones de Población 2020–2070; Instituto Nacional de Estadística: Madrid, Spain, 2020.
73. Photovoltaic Geographical Information System. 2021. Available online: https://re.jrc.ec.europa.eu/pvg_tools/en/ (accessed on: 20 July 2021).
74. Situación y potencial de generación de biogás; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2011.
75. Evaluación del potencial de energía de la biomasa, estudio técnico PER 2011-2020; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2011.
76. Observatorio Sostenibilidad. 1 millón de tejados solares en 2025: energía rentable y accesible para los ciudadanos. Madrid, Spain, 2021.
77. Bódis, K.; Kougias, I.; Jäger-Waldau, A; Taylor, N.; Szabó, S. A high-resolution geospatial assessment of the rooftop solar photovoltaic potential in the European Union. Renewable and Sustainable Energy Reviews 2019, 114, 109309. https://doi.org/10.1016/j.rser.2019.109309
78. Azam, A.; Rafiq, M.; Shafique, M.; Zhang, H.; Yuan, J. Analyzing the effect of natural gas, nuclear energy and renewable energy on GDP and carbon emissions: A multi-variate panel data analysis. Energy 2021, 219, 119592. https://doi.org/10.1016/j.energy.2020.119592
79. KumarNarayan, P.; Narayan, S; Popp, S. A note on the long-run elasticities from the energy consumption–GDP relationship, Applied Energy 2010, 87, 3, 1054-1057. https://doi.org/10.1016/j.apenergy.2009.08.037
80. Iglesias-Émbil, M.; Valero, A.; Ortego, A.; Villacampa, M.; Vilaró, J.; Villalba, G. Raw material use in a battery electric car – a thermodynamic rarity assessment. Resources, Conservation & Recycling 2020, 158, 104820. https://doi.org/10.1016/j.resconrec.2020.104820
81. Carrara, S.; Dias, P. A.; Plazzotta, B.; Pavel, C. Raw materials demand for wind and solar PV technologies in the transition towards a decarbonized energy system; Publications Office, 2020. https://data.europa.eu/doi/10.2760/160859
82. Ashby, M.; Attwood, J.; Lord, F. Materials for Low-Carbon Power - A White Paper, 2nd ed.; Granta teaching resources, 2012.
83. García-Olivares, A.; Ballabrera-Poy, J.; García-Ladona, E; Turiel, A. A global renewable mix with proven technologies and common materials. Energy Policy 2012, 41, 561-574. https://doi.org/10.1016/j.enpol.2011.11.018.
84. Jones, H.; Moura, F.; Domingos, T. Life cycle assessment of high-speed rail: a case study in Portugal. Int J Life Cycle Assess 2017, 22, 410-422. https://doi.org/10.1007/s11367-016-1177-7.
85. Verdejo, E. Z.; Requerimientos materiales de la transmisión y distribución de la electricidad para la transición energética. Master tesis, Universidad de Valladolid, escuela de ingenierías industriales, Valladolid, Spain, 2021.
86. Manifestaciones ALIENTE (ALIENTE protests). 2022. Available online: https://aliente.org/category/campanas/manifestaciones-aliente (accessed on 30 June 2022).
87. Hernández, A.; Renovable sí, pero no así. La razón. 2021. Available online: https://www.larazon.es/opinion/20211012/jeiekwh5xfbjxcut4lc7ltglsi.html (accessed on 01 May 2022).
88. Pérez, B.P.; Díaz-Cuevas, P. Connections between Water, Energy and Landscape: The Social Acceptance in the Monachil River Valley (South of Spain). Land 2022, 11, 1203. https://doi.org/10.3390/ land11081203
89. Estado del acceso y conexión de la generación renovable eólica y solar fotovoltaica. 2022. Available online: https://www.ree.es/es/clientes/datos-acumulados-generacion-renovable (accessed on 25 June 2022).
90. Temper, L.; del Bene, D.; Martinez-Alier, J. Mapping the frontiers and front lines of global environmental justice: the EJAtlas. Journal of Political Ecology 2015. 22, 255-278. https://doi.org/10.2458/v22i1.21108.
91. Mavhunga, C.C.; Trischler, H. (Eds). Energy (and) Colonialism, Energy (In)Dependence: Africa, Europe, Greenland, North America. RCC perspectives 2014, 5. doi.org/10.5282/rcc/6554.
92. Valero, A.; Torrubia, J. Libro Blanco de la Biorregión Cantábrico-Mediterránea. Cap 4. Fundación Foros de la Concordia y Capitulo Español del Club de Roma, 2020.
93. Bruckner, T.; Bashmakov, I.; Mulugetta, Y.; Chum, H.; Navarro, A. d. l. V. ; Edmonds, J.; Faaij, A.; Fungtammasan, B.; Garg, A.; Hertwich, E.; Honnery, D.; Infield, D.; Kainuma, M.; Khennas, S.; Kim, S.; Nimir, H.; Riahi, K.; Strachan, N.; Wiser, R.; Zhang a. X. Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change; Cambridge University Press: Cambridge, United Kingdom and New York, NY, USA. 2014.
94. Ambrose, H.; Kendall, A.; Lozano, M.; Wachche, S.; Fulton, L. Trends in life cycle greenhouse gas emissions of future light duty electric vehicles. Transportation Research Part D: Transport and Environment 2020, 18, 102287, https://doi.org/10.1016/j.trd.2020.102287
95. Lee, D.; Thomas, V.M.; Brown, M.A. Electric Urban Delivery Trucks: Energy Use, Greenhouse Gas Emissions, and Cost-Effectiveness. Environmental Science & Technology 2013, 47, 14, 8022-8030. https://doi.org/10.1021/es400179w
96. Carranza, G; Nascimiento, M.D.; Fanals, J,; Febrer, J.; Valderrama, C. Life cycle assessment and economic analysis of the electric motorcycle in the city of Barcelona and the impact on air pollution. Science of the Total Environment 2022, 821, 153419 https://doi.org/10.1016/j.scitotenv.2022.153419
97. Ministerio de Consumo/EC-JRC. Sostenibilidad del consumo en España. Evaluación del impacto ambiental asociado a los patrones de consumo mediante Análisis del Ciclo de Vida; Ministerio de Consumo: Madrid, Spain, 2022.
98. Una población en crecimiento. 2022. Available online: https://www.un.org/es/global-issues/population (accessed on 2 February 2022).
99. Carnegie Europe; Open Society European Policy Institute. The EU and Climate Security: Toward Ecological Diplomacy. Carnegie Endowment for International Peace; Washington DC, USA, 2021.
100. Lallana, M.; Almazán, A.; Valero, A.; Lareo, Á. Assessing Energy Descent Scenarios for the Ecological Transition in Spain 2020–2030. Sustainability 2021, 13, 11867. https:// doi.org/10.3390/su132111867.

Author Response File: Author Response.pdf

Reviewer 4 Report

An overall very interesting article covering a 'hot topic' globally right now and the authors have captured the main aspects and issues of energy transition very well.  The article is well written with a sound concept and methodology applied. Of course there can be a discussion to what extent and how soon the electrification can happen, what is the sustainability of the production of PV, CSP and wind power production plants and should and energy balance rely on wind and solar, that would require more storage capacity and how sustainable will the storage technologies be. A base load by nuclear energy? Is it considered? Or other type of on-demand production of baseload (e.g. biomas in CHP plants) Perhaps a bit more detail in the discussion of the material footprints could be advised. Nevertheless an article presents results of an interesting study that can be replicated in other regions.

Still I noticed some shortcomings that could be addressed to improve the article even more:

The article does not have a hypothesis stated in the paper, perhaps it should be added. Also the section of Limitations is not included.

In the lines of 72-74 address an importance of self-sufficiency and risks of foreign dependence, but a mention of the Russian unprovoked invasion to Ukraine that has shattered the supply of Russian produced fossil fuels should be mentioned as I assume it is also relevant to Spain as well as the weaponisation of fossil fuels and price increase caused by the actions of Russia at the moment and potential weaponisation of fossil fuels (and also materials and technologies used for producing PV) by other dictatorships in the future.

in ch 2.1.3 heating only or heating and cooling? Also 'increase in activity' should be explained and an assumption for energy saving and increase of energy efficiency should be mentioned here (it is mentioned later in the text)

The naming of the scenarios -  maybe ''high and low material intensity'' scenario would sound better instead of highly ands lowly?

In the description of Figure 4 I would have liked to see the resources used for heat production - is it fossil or renewable? What is meant by the Renewable energy? Is it used for the production of electricity? It seems that the resources e.g. waste and coal etc. are combined in a graph with the energy outcome e.g. electricity and heat. Can they be separated? 

In Fig. 7 ''Thermal'' energy means geothermal? Please use the same term throughout the whole article.

Line 337 - The energy demand decreases without reducing activity thanks to electrification, 337 which is more efficient. - also due to energy efficiency in appliances, buildings and energy saving incentives

In Line 335 you mention the use of nuclear energy, was it showed anywhere in the Figures or in the text before? What is the future for the use of nuclear energy in the region? A sustainable youse of nuclear energy is considered a viable option in many regions, but it was not sufficiently covered in this article.

The polygonal surfaces is meant the installation on buildings? This could perhaps be explained at the first mention of the term. And the term is no longer used at the end of the article, an inconsistency there as well.

The language is overall very good, still there are some lines e.g. 36-37 that could be  rephrased to make them more readable, so a readthrough of the whole article would be advised.

Author Response

Please see attachment

An overall very interesting article covering a 'hot topic' globally right now and the authors have captured the main aspects and issues of energy transition very well.  The article is well written with a sound concept and methodology applied. Of course there can be a discussion to what extent and how soon the electrification can happen, what is the sustainability of the production of PV, CSP and wind power production plants and should and energy balance rely on wind and solar, that would require more storage capacity and how sustainable will the storage technologies be. A base load by nuclear energy? Is it considered? Or other type of on-demand production of baseload (e.g. biomas in CHP plants) Perhaps a bit more detail in the discussion of the material footprints could be advised. Nevertheless an article presents results of an interesting study that can be replicated in other regions.

 Dear Reviewer, thank you very much for your time reviewing this paper and your assessment. We would also like to thank you for your comments which helped us to improve the quality of the paper. We have gone through most of the document, restructured the document placing the focus on the indicators, and making more visual the results in order to improve the quality of the paper as you have recommended us.

We have considered the 2050 scenario in order to have a temporary scenario and as it is the goal from the EU.

The sustainability is addressed on the material demands, space consumption and CO2 emissions during building, of course there is a lack according to water resources needed to manufacture them, we hope to continue researching on this scope in order to improve our findings. In order to cover a little bit of the scope that you mention we added these sentences from line 91 to 98:

The energy transition goal is to reduce fossil fuel consumption and greenhouse gas (GHG) emissions drastically using clean technologies. Therefore, the associated carbon footprint, expressed in tons of CO2 equivalent, significantly decreases since, at least in the use phase, clean technologies, including renewables or electric mobility, do not emit GHGs.

That said, clean technologies generate other impacts that cannot be measured through the carbon footprint alone. Important amounts of water, raw materials, and en-ergy (most of which obtained from fossil fuels) are required to produce them

About the energy balance we have compared our model with others and estimated the storage capacities, we talk about the limitations of the model in section 3.3. Model assumptions from lines 278 to 303. And compare the model with others already made for Spain in the Supplementary material.

We consider the production with biomass and biogas, we call it thermal, We state in line 340” In 2050 thermal refers to biogas and biomass power plants”.

We have improved too the discussion about material footprints as follows (inside of the results) Section 4.3. Lines 517 to 537:

Suppose almost all resources of some materials and several times the planet’s known reserves are required to meet a global energy transition. In that case, significant inequali-ties are expected between countries in achieving the energy transition due to the lack of access to materials. Together with the context of global warming, it can lead to severe ge-opolitical conflicts [99].

The results indicate the criticality of mineral materials, their scarcity relative to their consumption and the local supply risks they may entail. These supply risks may con-strain the technological development necessary to achieve an energy transition at regional and global levels. The high pressure on critical materials also indicates the need to con-sider scenarios with a more significant reduction in consumption [100] and more efficient use of the mineral materials necessary for an energy transition. Furthermore, the global equivalent reserves footprint shows the minimum mineral requirements for an energy transition as the life cycle of the products and subsequent recycling rate are not taken into account. This also indicates the need to find more deposits that guarantee a global energy transition and a circular economy that minimizes waste materials.

The result of the global equivalent mineral footprint if everyone performs the same energy transition indicates the unsustainability of current lifestyles in the Bioregion. However, similar results are obtained compared with global north lifestyles. The result for European citizens performing the same energy transition indicates that one-third of lith-ium and cobalt reserves are needed, in addition to one-sixth of silver, nickel, neodymium and copper reserves when Europe represents a tenth of world’s population.

Still I noticed some shortcomings that could be addressed to improve the article even more:

The article does not have a hypothesis stated in the paper, perhaps it should be added. Also the section of Limitations is not included.

We have added a section called model assumptionsm where we talk about the hypothesis considered. We have also added these paragraphs in the same section in order to talk about the limitations.

Cost constraints have not been considered because we would incorporate considera-ble uncertainty in the model due to the recent high price volatilities of raw materials [54] and renewable technologies [13].

It is necessary to point out some limitations of our simulations. We assume a perfect electricity transmission with no congestion nor frequency regulations and perfect match-ing between energy generation, energy storage and energy demand. Furthermore, there are uncertainties in extreme weather events where energy demands and production may vary. To address this uncertainty, we are assuming an energy overproduction to guarantee that energy demand can always be supplied. We have also considered distribution and trans-mission line materials requirements that guarantee an appropriate interconnection and electricity distribution.

We assume that these limitations do not change the results significantly, since we have compared the electrical power system of the Bioregion for the 2050 scenario with others already proven for Spain. More detailed information is shown in the supplemen-tary material.

Disruptive technological changes, which have not been considered in our model, can occur during the energy transition, requiring fewer materials or space resources. In this respect, it is not our goal to predict the future but to guide future policies based on the available technologies and existing global plan trends.

We have gathered the data with the most recent available reports, there may be some data uncertainties or recent changes in activity or demand predictions, but these uncer-tainties do not change the conclusions of this paper.

In the lines of 72-74 address an importance of self-sufficiency and risks of foreign dependence, but a mention of the Russian unprovoked invasion to Ukraine that has shattered the supply of Russian produced fossil fuels should be mentioned as I assume it is also relevant to Spain as well as the weaponisation of fossil fuels and price increase caused by the actions of Russia at the moment and potential weaponisation of fossil fuels (and also materials and technologies used for producing PV) by other dictatorships in the future.

We have added these sentences in the introduction.

The first is the energy self-sufficiency indicator, evaluating the potential social impacts associated with the space consumption of clean technologies and extra-territorial energy dependence. The second is the well-known ecological footprint. The third is the critical global equivalent mineral footprint, which evaluates the limits of an energy transition due to potential material shortages and supply risks. The first and third indicators show foreign dependence and exposure to geopolitical instabilities, which are vulnerabilities with negative consequences. This has become evident in Ukraine’s war, in which Europe’s gas dependence on Russia is provoking severe economic consequences in Europe [19] and the world [20].

We have added too this sentence in line 441:

Suppose this installation trend is replicated elsewhere, with rural and unpopulated regions supplying energy necessities of urban and populated regions. In that case, it may cause significant imbalances between autonomous communities or territories, with seri-ous social problems, as has already occurred in the mining case described in the Global Atlas of Environmental Justice [90], raising a global concern about energy colonialism in the energy transition [91]. On the other hand, these extreme energy dependences may lead to vulnerabilities and supply risks.

We have also added this sentence in conclusions:

For this reason, this work proposes installing renewable power in accordance with the energy demand of each territory, seeking self-sufficiency as far as possible and avoiding energy colonialism practices or extreme energy dependences.

in ch 2.1.3 heating only or heating and cooling? Also 'increase in activity' should be explained and an assumption for energy saving and increase of energy efficiency should be mentioned here (it is mentioned later in the text)

We have considered heating electrification with heat pumps, which work for cooling too.

We have explained increase in activity (with a new reference too) and mentioned the energy efficiency:

we have considered an increase in consumption linked to the expected population and GDP growth [46].

Residential consumption increases linearly to population growth, choosing an income elasticity value of 0.2 between GDP and consumption increase [52].

The naming of the scenarios -  maybe ''high and low material intensity'' scenario would sound better instead of highly ands lowly?

Thanks for the proposal. Finally we decided to show the results with an average of the high and low material intensity. We have changed the term in the supplementary material where we supply all the data and also the results for both scenarios.

In the description of Figure 4 I would have liked to see the resources used for heat production - is it fossil or renewable? What is meant by the Renewable energy? Is it used for the production of electricity? It seems that the resources e.g. waste and coal etc. are combined in a graph with the energy outcome e.g. electricity and heat. Can they be separated? 

We have changed the term to final energy consumption which is more appropriate.

Final energy consumption represents the kind of energy source that we use in our demands. For example to plug a PC uses electricity, to drive a car uses oil, and heating a house with gas, direct renewable, coal, or maybe oil.

With renewable energy we mean for direct use, as for example heating a house with biomass. Or heating a house with solar thermal.

Heat is coming usually from cogeneration power plants, which a big part of industry use, currently is mostly used from gas, but some are using biogas and biomass. With heat we mean the part of the process that only demand for heat. In the 100% renewable system we have checked that there are enough natural resources to satisfy the heat demand in case of producing with cogeneration with biogas or biomass.

Here is the definition from EEA “Total final energy demand (consumption) is the sum of energy consumption in each final demand sector. In each sub-sector or end-use, at least six types of energy are shown: coal, oil, gas, electricity, heat and renewables.” https://www.eea.europa.eu/data-and-maps/indicators/final-energy-consumption-outlook-from-iea#:~:text=Total%20final%20energy%20demand%20(consumption,%2C%20electricity%2C%20heat%20and%20renewables.

Anyway in supplementary material we show each final energy consumption by sector and the electricity mix.

In Fig. 7 ''Thermal'' energy means geothermal? Please use the same term throughout the whole article.

We add this explanation: Figure 5 shows the Bioregion’s renewable nameplate capacity for the reference, 2030 and 2050 scenarios. Thermal represents the conventional thermal power plants fueled with conventional fuels in 2020 and 2030. In 2050 thermal refers to biogas and biomass power plants.

Line 337 - The energy demand decreases without reducing activity thanks to electrification, 337 which is more efficient. - also due to energy efficiency in appliances, buildings and energy saving incentives

Thanks for the comment. We have no considered saving incentives, just the technological transformation and better isolation in buildings. We changed the sentence in Results lines 325 to 335:

Total energy demand decreases in all scenarios without reducing economic activity thanks to electrification, which is more efficient. Due to partial transport electrification, 2030 oil demands decrease, increasing electricity demand.

By 2050, as most of the economy is electrified, electrical energy represents 79.37% of the final energy consumption, 233 TWh, doubling the current electricity demand. Electric-ity demand for hydrogen production accounts for 22 TWh. A small oil-dependent fraction (4.75%) is still considered for difficult to decarbonize sectors, such as primary sector and part of the industry sector. The 2050 efficient scenario achieves a greater electricity de-mand reduction of 40 TWh thanks to land transport efficient measures and building iso-lation.

In Line 335 you mention the use of nuclear energy, was it showed anywhere in the Figures or in the text before? What is the future for the use of nuclear energy in the region? A sustainable youse of nuclear energy is considered a viable option in many regions, but it was not sufficiently covered in this article.

No, It has not been shown before as it is part of the current electrical mix. We have only considered the closure plans of the current nuclear power plants.

We have not considered nuclear energy as it is not a renewable energy, and it is very difficult for new plants to be built in Spain due to public opposition. But as engineers we consider that nuclear energy is a very important source during the transition to a 100% renewable electrical system.

The polygonal surfaces is meant the installation on buildings? This could perhaps be explained at the first mention of the term. And the term is no longer used at the end of the article, an inconsistency there as well.

It is the land surface area occupied by renewables energies. We have changed the sentence, now is in model assumptions line 259:

The electrical system model is based on an energy balance to meet energy demands. We have considered full load hours for each technology and territory. We have considered a power density installation between 4 to 8 MW/km2 to estimate the polygonal surface ar-ea occupied by wind farms based on [42], [43]. There is no resource scarcity for ground photovoltaics (PV) in any scenario, considering the polygonal area occupied by PV of 70 MW/km2 [44].

We use the term polygonal area because it is the total area needed to install a power plant, and we have compared with the wind resources of each autonomous community ( area with a mean value of wind speed higher than 6 m/s)

The language is overall very good, still there are some lines e.g. 36-37 that could be  rephrased to make them more readable, so a readthrough of the whole article would be advised.

Thanks for the comment, we have reviewed all the text and made several corrections. The sentence you refer now states like that:

It is a fact that RES technologies imply large occupation space impacting rural areas and biodiversity [10], highlighting the importance of linking spatial planning to energy planning [11]. Furthermore, decarbonization implies the requirement of vast amounts of raw materials used to produce clean technologies [12], [13], [14], [15], [16], [17]. Raw mate-rials security of supply raises global and European concerns [18] as mineral shortages may put at risk the very development of the energy transition.

References

1. United Nations. Paris agreement. In proceedings of the 21st conference parties, Paris, France, (11 december 2015). http://dx.doi.org/FCCC/CP/ 2015/L.9
2. EU Commission. Long-term strategy for 2050. Available online: https://ec.europa.eu/clima/eu-action/climate-strategies-targets/2050-long-term-strategy_es (accessed on 15 June 2022).
3. Net Zero by 2050, A Roadmap for the Global Energy Sector; International Energy Agency: Paris, France, 2021.
4. EC Comission. Glosary: Carbon dioxide equivalent. 2022. Available online: https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Carbon_dioxide_equivalent#:~:text=A%20carbon%20dioxide%20equivalent%20or,with%20the%20same%20global%20warming (accessed on 15 September 2022).
5. Jacobson, M. Z.; Delucchi, M. A.; Cameron, M. A.; Manogaran, I. P.; Shu, Y.; Krauland v., A.-K. Impacts of Green New Deal Energy Plans on Grid Stability, Costs, Jobs, Health, and Climate in 143 countries. One Earth 1 2019, 4, 449-463. https://doi.org/10.1016/j.oneear.2019.12.003.
6. Child, M.; Bogdanov, D.; Breyer, C. The role of storage technologies for the transition to a 100% renewable energy system in Europe. Energy Procedia 2018, 155, 44-60. https://doi.org/10.1016/j.egypro.2018.11.067.
7. Estrategia de descarbonización a largo plazo 2050. Estrategia a largo plazo para una economía española, moderna, competitiva y climáticamente neutra a 2050; Ministerio para la Transición Ecológica y el Reto Demográfico: Madrid, Spain, 2020.
8. Hussain, A.; Perwez, U.; Ullah, K.; Kim, C.; Asghar, N. Long-term scenario pathways to assess the potential of best available technologies and cost reduction of avoided carbon emissions in an existing 100% renewable regional power system: A case study of Gilgit-Baltistan (GB), Pakistan. Energy 2021, 221. https://doi.org/10.1016/j.energy.2021.119855.
9. Felipe Andreu, J.; Schneider, D.; Krajačić, G. Evaluation of integration of solar energy into the district heating system of the city of Velika Gorica. Thermal Science 2016, 20, 1049-1060. https://doi.org/10.2298/TSCI151106106A.
10. Poggi, F.; Firmino, A; Amado, M. Planning renewable energy in rural areas: Impacts on occupation and land use. Energy 2018, 155, 630-640. https://doi.org/10.1016/j.energy.2018.05.009.
11. De Pascali, P.; Bagaini, A. Energy Transition and Urban Planning for Local Development. A Critical Review of the Evolution of Integrated Spatial and Energy Planning. Energies2019, 12, 35. https://doi.org/10.3390/en12010035
12. Valero, A; Valero, A.; Calvo, G. Ortego, A. Material bottlenecks in the future development of green technologies. Renewable and Sustainable Energy Reviews 2018, 178-200. https://doi.org/10.1016/j.rser.2018.05.041.
13. The Role of Critical Minerals in Clean Energy Transitions, World Energy Outlook Special Report; International Energy Agency: Paris, France, 2021.
14. Calvo, G.; Valero, A. Strategic mineral resources: Availability and future estimations for the renewable energy sector. Environmental Development 2022, 41, 100640. https://doi.org/10.1016/j.envdev.2021.100640.
15. Calvo, G.; Valero, A.; Valero, A. Thermodynamic Approach to Evaluate the Criticality of Raw Materials and Its Application through a Material Flow Analysis in Europe. Journal of Industrial Ecology 2017, 839-852, 22, https://doi.org/10.1111/jiec.12624.
16. Calvo, G.; Valero, A; Valero, A. Assessing maximum production peak and resource availability of non-fuel mineral resources: Analyzing the influence of extractable global resources. Resources, Conservation and Recycling 2017, 208-217, 125. https://doi.org/10.1016/j.resconrec.2017.06.009.
17. Ortego, A.; Calvo, G.; Valero, A; Iglesias-Émbil, M.; Valero, A.; Villacampa, M. Assessment of strategic raw materials in the automobile sector. Resources, Conservation and Recycling 2020, 161, 104968. https://doi.org/10.1016/j.resconrec.2020.104968
18. EU Commission. Critical raw material list. 2022. Available online: https://rmis.jrc.ec.europa.eu/?page=crm-list-2020-e294f6. (accessed on 10 July 2022).
19. Partington, R. Inflation in eurozone hits record 8.6% as Ukraine war continues. The Guardian. 1 July 2022. Available online: https://www.theguardian.com/business/2022/jul/01/inflation-in-eurozone-hits-record-86-as-ukraine-war-continues (accessed on 6 September 2022)
20. Caldara, D.; Conlisk, S.; Iacoviello, M.; Penn, M. The Effect of the War in Ukraine on Global Activity and Inflation; FEDS Notes. Washington: Board of Governors of the Federal Reserve System, May 27, 2022. https://doi.org/10.17016/2380-7172.3141.
21. IDAE; MITECO. Plan Nacional Integrado de Energía y Clima; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
22. Zalk, J.; Behrens, P. The spatial extent of renewable and non-renewable power generation: A review and meta-analysis of power densities and their application in the U.S. Energy Policy 2018, 123, 83-91. https://doi.org/10.1016/j.enpol.2018.08.023
23. Global Footprint Network. Ecological Footprint. 2021. Available online: https://www.footprintnetwork.org/our-work/ecological-footprint/ (accessed on 1 October 2021).
24. Global Footprint Network. Glossary. 2022. Available online: https://www.footprintnetwork.org/resources/glossary/ (accessed on 5 June 2022).
25. Valero, A; Valero, A. Thanatia, The Destiny of the Earth’s Mineral resources: A cradle –to-cradle assessment; World Sci. Publ. Co. 2014. ISBN 978-981-4273-93-0.
26. Schmidt-Bleek, F. MIPS–A universal ecological measure? Fresenius Environmental Bulletin 1993, 2, 8, 306–311.
27. Planetary Pressures–Adjusted Human Development Index (PHDI). 2022. Available online: https://hdr.undp.org/planetary-pressures-adjusted-human-development-index#/indicies/PHDI (accessed on 30 July 2022).
28. Valero, A; Valero, A.; Calvo, G. The Material Limits of Energy Transition: Thanatia; Springer Nature: Switzerland, 2021. ISBN 978-3-03078532-1.
29. Palacios, J.-L.; Calvo, G.; Valero, A.; Valero, A. The cost of mineral depletion in Latin America: An exergoecology view. Resources Policy 2018, 59, 117-124. https://doi.org/10.1016/j.resourpol.2018.06.007.
30. Palacios, J.-L.; Calvo, G.; Valero, A.; Valero, A. Exergoecology Assessment of Mineral Exports from Latin America: Beyond a Tonnage Perspective. Sustainability2018, 10, 723. https://doi.org/10.3390/su10030723.
31. Valero, A.; Valero, A.; Arauzo, I. Evolution of the decrease in mineral exergy throughout the 20th century. The case of copper in the US. Energy 2008, 33, 2, 107-115. https://doi.org/10.1016/j.energy.2007.11.007.
32. Valero, A; Valero, A. Es la entropía, estúpido!. In Bioeconomía para el siglo XXI. Actualidad de Nicholas Georgescu-Roegen.; Arenas, L.; Naredo, J. M.; Riechmann, J.; Libros de la Catarata Publ.: Madrid, Spain, 2022; pp.185-227. ISBN 978-84-1352-500-6.
33. United States Geological Survey USGS. USGS Online Publications Directory. 2022. Available online: https://pubs.usgs.gov/periodicals/mcs2022/ (accessed on 25 February 2022).
34. Grupo Aragonés del Capítulo Español del Club de Roma. Reunión 22 de septiembre biorregión cantábrico-mediterránea (Meeting September 22 Cantabrian-Mediterranean bioregion). Available online: https://www.clubderoma-aragon.org/eventos/reunion-22-de-septiembre-biorregion-cantabrico-mediterranea/ (accessed on 6 July 2021).
35. Fundación Foros de la Concordia. La biorregión Cantábrico-Mediterránea (BCM) constituye un espacio geográfico con raíces naturales, sociales e históricas comunes, que encuentra en el río Ebro su gran eje vertebrador (The Cantabrian-Mediterranean bioregion (BCM) constitutes a geographical space with common natural, social and historical roots, which finds its great backbone in the Ebro River). Available online: https://www.bioebro.org/la-biorregion/ (accessed on 25 August 2021).
36. Expansión/Datosmacro.com. El PIB de las comunidades autónomas (The GDP of the autonomous communities). Available online: https://datosmacro.expansion.com/pib/espana-comunidades-autonomas (accessed on 6 July 2021).
37. The World Bank. Consumo de energía procedente de combustibles fósiles (Energy consumption from fossil fuels). 2022. Available online: https://datos.bancomundial.org/indicator/EG.USE.COMM.FO.ZS (accessed on 20 June 2022).
38. REE; MITECO. Plan de desarrollo de la Red de Transporte de Energía Eléctrica Período 2021-2026; Red Eléctrica de España: Madrid, Spain, 2021.
39. Bistaffa, F.; Blum, C.; Cerquides, J.; Farinelli, A.; Rodríguez-Aguilar, J. A Computational Approach to Quantify the Benefits of Ridesharing for Policy Makers and Travellers. IEEE Transactions on Intelligent Transportation Systems 2021, 22, 119-130. Doi: 10.1109/TITS.2019.2954982.
40. Jonge, D. d.; Bistaffa, F.; Levy, J. A Heuristic Algorithm for Multi-Agent Vehicle Routing with Automated Negotiation. pp. 404-412. In Proceedings of the 20th International Conference on Autonomous Agents and Multiagent Systems (AAMAS), virtual event, United Kingdom, (3-7 May 2021). http://hdl.handle.net/10261/257887.
41. García-Álvarez, A.; Pérez-Martínez, P. J.; González-Franco, I. Energy Consumption and Carbon Dioxide Emissions in Rail and Road Freight Transport in Spain: A Case Study of Car Carriers and Bulk Petrochemicals. Journal of Intelligent Transportation Systems 2013, 17, 3, 233-244. https://doi.org/10.1080/15472450.2012.719456
42. Análisis del recurso. Atlas eólico de España. Estudio técnico PER 2011-2020; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2011.
43. Enevoldsen, P.; Jacobson, M. Data investigation of installed and output power densities of onshore and offshore wind turbines worldwide. Energy for sustainable development 2021, 60, 40-51. https://doi.org/10.1016/j.esd.2020.11.004.
44. Álvarez, C.; Zafra, M. Cuánto ocupan las megacentrales solares: investigadores alertan del impacto del ‘boom’ fotovoltaico. El País. 23 JAnuary 2021. Available online: https://elpais.com/clima-y-medio-ambiente/2021-01-23/cuanto-ocupan-las-megacentrales-solares-investigadores-alertan-del-impacto-del-boom-fotovoltaico.html (accessed on 5 august 2021).
45. EU Reference Scenario 2020, Energy, transport and GHG emissions - Trends 2050; European Commission: Brussels, Belgium, 2021.
46. Paula-Elena, D.; Liviu-George, M. The relationship between Income, Consumption and GDP: A Time Series, Cross-Country Analysis. Procedia Economics and Finance 2015, 23, 1535-1543. https://doi.org/10.1016/S2212-5671(15)00374-3.
47. Nguyen, T.-V.; Schnidrig, J.; Maréchal, F. An analysis of the impacts of green mobility strategies and technologies on different European energy systems. In Proceedings of ECOS 2021 - The 34th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Sicily, Italy, (28 june 2021).
48. Schnidrig, J; Nguyen, T.-V; Li, X.; Maréchal, F. A modelling framework for assessing the impact of green mobility technologies on energy systems. In Proceedings of ECOS 2021 - The 34th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Sicily, Italy, (28 june 2021).
49. García Álvarez, A.; Martín Cañizares, M. d. P. Metodología de cálculo del consumo de energía de los trenes de viajeros y actuaciones en el diseño del material rodante para su reducción; ElecRail: Madrid, Spain, 2010.
50. EU Commission. EU Reference Scenario 2020. Available online: https://ec.europa.eu/energy/data-analysis/energy-modelling/eu-reference-scenario-2020_en (accessed on 27 July 2021).
51. Hager, T.J.; Morawicki, R. Energy consumption during cooking in the residential sector of developed nations: A review. Food policy 2013, 40, 54-63. https://doi.org/10.1016/j.foodpol.2013.02.003
52. economics for energy. Escenarios para el sector energético en España 2030-2050. Vigo, Spain, 2017.
53. Estrategia a largo plazo para una economía española moderna, competitiva y climáticamente neutra en 2050. Anexos; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
54. Magdalena, R.; Calvo, G.; Valero, A. The Energy Cost of Extracting Critical Raw Materials from Tailings: The Case of Coltan. Geosciences 2022, 12, 214. https:// doi.org/10.3390/geosciences12050214.
55. Gobierno de Aragón. Boletín de Coyuntura Energética en Aragón 2018: Zaragoza, Spain, 2019.
56. Govern Illes Balears. PORTAL ENERGÈTIC (energy portal). 2021. Available online: http://www.caib.es/sites/energia/ca/publicacions_estadistiques_i_preus_de_lenergia-7491/ (accessed on 6 July 2021).
57. Instituto Catalán de Energía. Balance energético de Cataluña (catalonian energy balance). Available online: http://icaen.gencat.cat/es/energia/estadistiques/resultats/anuals/balanc_energetic/ (accessed on 6 July 2021).
58. ivace energía. Datos energéticos de la Comunitat Valenciana; Generalitat Valenciana: Valencia, Spain, 2019.
59. Área de Estudios y Planificación. EUSKADI ENERGÍA 2018, Datos energéticos; Ente Vasco de la Energía: Bilbao, Spain, 2020.
60. Datos energéticos de la C.A. de Euskadi (Energy data of Basque Country autonomous community). 2021. Available online: https://www.eustat.eus/estadisticas/tema_552/opt_1/tipo_1/ti_datos-energeticos-de-la-c-a/temas.html#el. (accessed on 6 July 2021).
61. Gobierno de Navarra. Balance Energético de Navarra; Pamplona, Spain, 2018.
62. La energía en España 2018. Ministerio para la Transición Ecológica y el Reto Demográfico: Madrid, Spain, 2020.
63. Informe sintético de indicadores de eficiencia energética en España. Año 2018; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
64. IDAE; MITECO. Consumo de Energía final (final energy consumption). Available online: http://sieeweb.idae.es/consumofinal/ (accessed on 6 July 2021).
65. El sistema eléctrico español 2018; Red Eléctrica de España: Madrid, Spain, 2019.
66. El sistema eléctrico español informe 2020, producción de energía eléctrica; Red Eléctrica de España: Madrid, Spain, 2021.
67. Ministerio de Transportes, Movilidad y Agenda Urbana. Consumo energético en el transporte por modo, tipo de combustible y tipo de tráfico (Energy consumption in transport by mode, type of fuel and type of traffic). Available online: https://apps.fomento.gob.es/BDOTLE/visorBDpop.aspx?i=314 (accessed on 14 July 2021).
68. Dirección General de Tráfico. Series históricas del parque de vehículos. Available online: https://www.dgt.es/es/seguridad-vial/estadisticas-e-indicadores/parque-vehiculos/series-historicas/ (accessed on 15 July 2021).
69. Análisis sobre los kilómetros anotados en las ITV; Dirección General de Tráfico: Madrid, Spain, 2018.
70. IDAE; MITECO. Informe anual del consumo energético año 2019; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2020.
71. economics for energy. Estrategias para la descarbonización del transporte terrestre en España, Un análisis de escenarios. Vigo, Spain, 2020.
72. INE. Proyecciones de Población 2020–2070; Instituto Nacional de Estadística: Madrid, Spain, 2020.
73. Photovoltaic Geographical Information System. 2021. Available online: https://re.jrc.ec.europa.eu/pvg_tools/en/ (accessed on: 20 July 2021).
74. Situación y potencial de generación de biogás; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2011.
75. Evaluación del potencial de energía de la biomasa, estudio técnico PER 2011-2020; Ministerio para la transición ecológica y el reto demográfico: Madrid, Spain, 2011.
76. Observatorio Sostenibilidad. 1 millón de tejados solares en 2025: energía rentable y accesible para los ciudadanos. Madrid, Spain, 2021.
77. Bódis, K.; Kougias, I.; Jäger-Waldau, A; Taylor, N.; Szabó, S. A high-resolution geospatial assessment of the rooftop solar photovoltaic potential in the European Union. Renewable and Sustainable Energy Reviews 2019, 114, 109309. https://doi.org/10.1016/j.rser.2019.109309
78. Azam, A.; Rafiq, M.; Shafique, M.; Zhang, H.; Yuan, J. Analyzing the effect of natural gas, nuclear energy and renewable energy on GDP and carbon emissions: A multi-variate panel data analysis. Energy 2021, 219, 119592. https://doi.org/10.1016/j.energy.2020.119592
79. KumarNarayan, P.; Narayan, S; Popp, S. A note on the long-run elasticities from the energy consumption–GDP relationship, Applied Energy 2010, 87, 3, 1054-1057. https://doi.org/10.1016/j.apenergy.2009.08.037
80. Iglesias-Émbil, M.; Valero, A.; Ortego, A.; Villacampa, M.; Vilaró, J.; Villalba, G. Raw material use in a battery electric car – a thermodynamic rarity assessment. Resources, Conservation & Recycling 2020, 158, 104820. https://doi.org/10.1016/j.resconrec.2020.104820
81. Carrara, S.; Dias, P. A.; Plazzotta, B.; Pavel, C. Raw materials demand for wind and solar PV technologies in the transition towards a decarbonized energy system; Publications Office, 2020. https://data.europa.eu/doi/10.2760/160859
82. Ashby, M.; Attwood, J.; Lord, F. Materials for Low-Carbon Power - A White Paper, 2nd ed.; Granta teaching resources, 2012.
83. García-Olivares, A.; Ballabrera-Poy, J.; García-Ladona, E; Turiel, A. A global renewable mix with proven technologies and common materials. Energy Policy 2012, 41, 561-574. https://doi.org/10.1016/j.enpol.2011.11.018.
84. Jones, H.; Moura, F.; Domingos, T. Life cycle assessment of high-speed rail: a case study in Portugal. Int J Life Cycle Assess 2017, 22, 410-422. https://doi.org/10.1007/s11367-016-1177-7.
85. Verdejo, E. Z.; Requerimientos materiales de la transmisión y distribución de la electricidad para la transición energética. Master tesis, Universidad de Valladolid, escuela de ingenierías industriales, Valladolid, Spain, 2021.
86. Manifestaciones ALIENTE (ALIENTE protests). 2022. Available online: https://aliente.org/category/campanas/manifestaciones-aliente (accessed on 30 June 2022).
87. Hernández, A.; Renovable sí, pero no así. La razón. 2021. Available online: https://www.larazon.es/opinion/20211012/jeiekwh5xfbjxcut4lc7ltglsi.html (accessed on 01 May 2022).
88. Pérez, B.P.; Díaz-Cuevas, P. Connections between Water, Energy and Landscape: The Social Acceptance in the Monachil River Valley (South of Spain). Land 2022, 11, 1203. https://doi.org/10.3390/ land11081203
89. Estado del acceso y conexión de la generación renovable eólica y solar fotovoltaica. 2022. Available online: https://www.ree.es/es/clientes/datos-acumulados-generacion-renovable (accessed on 25 June 2022).
90. Temper, L.; del Bene, D.; Martinez-Alier, J. Mapping the frontiers and front lines of global environmental justice: the EJAtlas. Journal of Political Ecology 2015. 22, 255-278. https://doi.org/10.2458/v22i1.21108.
91. Mavhunga, C.C.; Trischler, H. (Eds). Energy (and) Colonialism, Energy (In)Dependence: Africa, Europe, Greenland, North America. RCC perspectives 2014, 5. doi.org/10.5282/rcc/6554.
92. Valero, A.; Torrubia, J. Libro Blanco de la Biorregión Cantábrico-Mediterránea. Cap 4. Fundación Foros de la Concordia y Capitulo Español del Club de Roma, 2020.
93. Bruckner, T.; Bashmakov, I.; Mulugetta, Y.; Chum, H.; Navarro, A. d. l. V. ; Edmonds, J.; Faaij, A.; Fungtammasan, B.; Garg, A.; Hertwich, E.; Honnery, D.; Infield, D.; Kainuma, M.; Khennas, S.; Kim, S.; Nimir, H.; Riahi, K.; Strachan, N.; Wiser, R.; Zhang a. X. Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change; Cambridge University Press: Cambridge, United Kingdom and New York, NY, USA. 2014.
94. Ambrose, H.; Kendall, A.; Lozano, M.; Wachche, S.; Fulton, L. Trends in life cycle greenhouse gas emissions of future light duty electric vehicles. Transportation Research Part D: Transport and Environment 2020, 18, 102287, https://doi.org/10.1016/j.trd.2020.102287
95. Lee, D.; Thomas, V.M.; Brown, M.A. Electric Urban Delivery Trucks: Energy Use, Greenhouse Gas Emissions, and Cost-Effectiveness. Environmental Science & Technology 2013, 47, 14, 8022-8030. https://doi.org/10.1021/es400179w
96. Carranza, G; Nascimiento, M.D.; Fanals, J,; Febrer, J.; Valderrama, C. Life cycle assessment and economic analysis of the electric motorcycle in the city of Barcelona and the impact on air pollution. Science of the Total Environment 2022, 821, 153419 https://doi.org/10.1016/j.scitotenv.2022.153419
97. Ministerio de Consumo/EC-JRC. Sostenibilidad del consumo en España. Evaluación del impacto ambiental asociado a los patrones de consumo mediante Análisis del Ciclo de Vida; Ministerio de Consumo: Madrid, Spain, 2022.
98. Una población en crecimiento. 2022. Available online: https://www.un.org/es/global-issues/population (accessed on 2 February 2022).
99. Carnegie Europe; Open Society European Policy Institute. The EU and Climate Security: Toward Ecological Diplomacy. Carnegie Endowment for International Peace; Washington DC, USA, 2021.
100. Lallana, M.; Almazán, A.; Valero, A.; Lareo, Á. Assessing Energy Descent Scenarios for the Ecological Transition in Spain 2020–2030. Sustainability 2021, 13, 11867. https:// doi.org/10.3390/su132111867.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have addressed all my previous concerns.  This version is much improved. 

One minor edition issue is on page 12-13, Figure 8.  The figure is on the bottom of page 12 and the description is on the top of page 13.