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

Abstract

The US produces a large share of global biofuels but is unique in using a relatively inefficient biofuel pathway involving corn (maize) for ethanol production. The Renewable Fuel Standards that enshrine this feedstock were intended as a greenhouse gas emissions reduction measure but have had the effect of coupling the food, energy, and, to a lesser extent, water systems. This paper looks at the food–energy–water (FEW) nexus as exemplified by the growth in corn agriculture for internal combustion engine vehicle fuel and how that will likely change as vehicle electrification proceeds and accelerates. Starting with scenarios in which there is a rapid uptake in electric vehicles by 2030 and beyond, we examine the implications for the switch from liquid fuels for transportation in the United States toward electric vehicles (EVs). We find that scenarios in which EV penetration grows rapidly will clearly decrease demand for corn ethanol. Our analysis shows that, with judicious planning, the decrease in corn ethanol demand can have potential positive co-benefits. These co-benefits include reducing stressors on depleting aquifers and nutrient runoff to waterways. Substituting a small fraction of displaced industrial corn–ethanol cropland with large-scale solar photovoltaic (PV) capacity can supply a large fraction of the additional electricity needed for EVs. Finally, solar PV generation can ameliorate or even increase income and create more jobs than those lost to the decreased ethanol demand.

1. Introduction

One characteristic of the transition from a fossil fuel-dominated energy paradigm to a sustainable, renewable energy system is that a significant increase in the complexity of interactions between sub-systems will become apparent. Over the past several decades in the United States, petroleum products in the energy system have been used primarily in the transport sector [1]. A relatively early and ongoing example of cross-sectoral complexity in the energy transition commenced at the turn of this century with the increasing use (and subsidization) of ethanol made from corn (maize) as a by-mixture of gasoline [2]. Initial investigations by researchers concentrated on the question of net energy or greenhouse gas (GHG) emissions for corn ethanol (hereafter, in this context, simply “ethanol”) compared to gasoline [3,4,5,6,7]. This focus was important because of the dominant view at the time that “drop-in” substitutes for gasoline (and diesel fuel) would be the most promising pathway to reducing emissions in the transportation sector, at least for personal vehicles. Along with the focus on energy inputs and GHG outputs from the ethanol industry, there was also great unease with the issue of using a potential food crop (indirect, since almost all corn was used as animal feed or for the manufacturing of corn syrup) [8,9] and how indirect land use changes would impact the greenhouse gas reduction benefits of ethanol in the US [10,11]. The latter is still an ongoing debate when setting standards for GHG reductions [12].

The resolution, at least to a first approximation, that ethanol could bring net energy benefits, reduce US dependence on oil imports, and perhaps contribute to decreasing emissions has been moved to the background more recently due to the rapidly decreasing costs of batteries for electric vehicle (EV) applications [13,14], thus offering a completely different potential path to significantly lower GHG emissions, with overall higher efficiencies of resource use than would be possible with virtually any internal combustion engine vehicle (ICEV) technology. It is the aim of this paper to take a closer look at several significant potential implications and also co-benefits of the transition to EVs, and, in particular,, to examine these co-benefits in light of the dynamics within the corn ethanol sector that will be a necessary consequence of the transition to EVs.

Globally, EV sales represented 16% of total light-duty vehicle (LDV) sales in 2023 (although a significant fraction of about 30% of these are plug-in hybrid electric vehicles (PHEVs) [15]. This fraction is up from less than 1% of sales as recently as 2016. In China, EVs made up 37% of new registrations, with the comparable numbers being 82%, 16%, and 6% in Norway, the European Union and the U.S., respectively [15]. Both globally and in certain countries and regions, this represents an extremely rapid growth trajectory.

Since ethanol is used as an (roughly 10%) admixture with gasoline in most cases [16], a significant increase in EVs in the US fleet implies a decrease in the fraction and number of ICEVs, which in turn implies decreased demand for gasoline, and, by extension, ethanol. How large these changes will be depends strongly on the future penetration of EVs in the fleet. However, the decrease in demand for ethanol is only the beginning of a chain of consequences in the food, energy, and water (FEW) nexus, many of which may, with an appropriate degree of foresight, be turned into multi-faceted benefits. Unsurprisingly, there will necessarily also be trade-offs.

As demand for corn ethanol decreases, additional land used for fuel corn crops can be either taken out of production or put to other uses. The key contribution of this work is to show through a set of scenarios that a relatively small fraction of that land (on the order of 10%) that will presumably not be needed for ethanol production can be used for solar photovoltaic electricity production instead and that this substitution could supply nearly all of the additional electricity needed to meet the demand for a rapidly increasing EV fleet.

In addition, following the assumption of a growing EV fleet, a number of other potential co-benefits beyond carbon emission reductions may result. The scenarios presented in this work show that unsustainable withdrawals of groundwater in some areas, particularly above the Ogallala aquifer, could be reduced through the judicious selection of areas in which to reduce corn production for ethanol. Although corn is a crop of which only a relatively small percentage is irrigated, decreasing demand for corn in regions that are water-stressed would have the added benefit of moving toward the sustainable use of valuable and non-replenishable (on century time scales) water resources. Likewise, the large increase in fertilizer use due to increased corn production for ethanol over the past two decades could be reversed, with co-benefits for water quality in the extended Mississippi River watershed.

Finally, we present a somewhat more speculative analysis that shows that the loss of income in the corn ethanol sector (including growing and industrial processing components) can be to some extent replaced by income from solar PV electricity, with the caveat that it will depend on who develops the solar projects and how leases and income are distributed. Job creation in the solar industry could compensate for losses in the ethanol sector of the economy, albeit with shifts in required skills.

In the next sections, we will consider these different factors in turn. We begin by describing our assumptions and data in Section 2 and then give results for EV sales and fleet growth (the key input to the model, given in Section 3.1). Implications for corn ethanol demand (and the accompanying change in land use), water used for irrigation, and fertilizer use are presented in Section 3.2, Section 3.3, and Section 3.4, respectively, followed by options for solar photovoltaics to replace a fraction of land use in Section 3.5. Net energy availability comparisons are made in Section 3.6, with socioeconomic variables (earnings and jobs) discussed in Section 3.7. Finally, a discussion of the results and the conclusions are given in Section 4 and Section 5.

2. Materials and Methods

The approach taken in this paper is to start with the assumption of continued strong growth in sales of electric vehicles. As a consequence of rather slow vehicle turnover rates, there will be a lagging but similar increase in the EV fleet. This approach is justified by three different developments: current trends in EV sales [15,17], commitments by governments at both federal and state levels to decrease carbon emissions in the transportation sector, and stated commitments by vehicle manufacturers to phase out the production of ICEVs [18]. A model of stock turnover for US light-duty vehicles (LDVs) is created in which the initial growth rate of EV sales and an overall maximum production of LDVs are consistent with data trends from the past decade. Scrapping rates of LDVs are also consistent with recent trends and that, together with the sales data, the overall fleet grows by 0.5%/year. From that starting point, scenarios with a 25%, 50%, and 75% share of EV sales by 2030 are created, assuming an eventual level of 100% EV LDVs. The time horizon is 2050. Both ICEVs and EVs are assumed to have efficiency improvements of 1%/year.

As ethanol input feedstock, corn yields are assumed to increase by about two bushels/acre/year (approximately 1%/year) [9]. Ethanol process improvements (liters of ethanol per bushel of corn) are assumed to increase by about 0.5 L/decade, consistent with historical data [19]. For fertilizer application and land irrigation, data from the USDA National Agricultural Statistics Service were used [9]. Fertilizer use is assumed to be the following: a rate of 68 kg/acre on 93% of planted acreage for nitrogen; 32 kg/acre for 80% of acreage for phosphate; and 23 kg/acre on 63% of acreage for potash [9]. Approximately 10 million acres (four million hectares) of corn are irrigated each year, which we assume to be a baseline from which reductions can be made.

For solar photovoltaic systems, we assume a land use of five acres per MW of capacity and a yield of 1000 MWh_ac/MW_DC,cap, which is a conservative average for existing projects in the US Midwest [20]. To project forward the generation of electricity from land with solar PV substituting for corn planting, we use three different scenarios of 5%, 7%, and 10% of the “freed” land being used for solar PV.

For solar PV lease rates on agricultural land, we assume that farmers are offered anywhere from less than $500 to more than $1000 in annual payment rate per acre from solar energy, according to Purdue University’s Ag Economy Barometer [21].

Finally, we compare the economics of ethanol and solar pv from different points of view, depending on whether farmland is leased or owned, as well as looking at both corn and ethanol separately, and for solar pv, whether solar development is owned by the landowner or land is leased to a developer. Overall ethanol margins are taken as 0.045 USD/US gallon [22]. In addition to the direct economic incomes generated for both energy sources, we also use an employment factor method [23,24,25] to compare direct jobs in construction and in operations and the maintenance of corn farming, ethanol production, and solar pv installation, ignoring the manufacturing of solar panels.

3. Results

In the following sub-sections, we present results for EV growth trajectories, the assumed starting point in this work, and then for the different implications of EV growth on corn acreage, water and pesticide usage, opportunities for solar photovoltaics as an alternative energy source to corn ethanol, issues of net energy and energy return on energy invested (EROEI), and the follow-up impacts on income and jobs.

3.1. Electric Vehicle Growth

Three scenarios for EV sales growth are chosen, all with the assumption that eventually all LDV sales will be EVs. A logistic function for sales is assumed, with the initial growth rate being chosen so that sales of EVs in 2030 are 25%, 50%, and 75% in the three scenarios, as shown in Figure 1a. These growth rates and the assumptions made about fleet size, scrapping or retirement rates, and total sales are sufficient to fix the outputs for EV fleet penetration shown in Figure 1b, in which it can be seen that with even aggressive growth in EV sales, fleet penetrations of EVs by 2050 indicate that we will be far from a complete transition away from fossil fuel ICEVs. The sales shares in 2030 are chosen to represent a range of potential futures. For example, global EV sales shares have grown from less than one percent in 2016 to 18% in 2023; in Norway, sales shares increased from six percent a decade ago to over 90% in 2023 [15]. In China, the largest global market, EVs will make up over 40% of new car sales in 2024, up from 1.5% seven years ago [15]. In the US, sales shares have increased from one percent to nine percent in the past seven years, and the Biden administration had a goal of 50% EV sales by 2030 [26], a goal which has since been somewhat softened. In addition, many car manufacturers have set aggressive targets for their own production of EVs, up to 100% by the middle of the next decade [27]. These examples make plausible the rapid growth that would be necessary to achieve the scenario targets set in our three cases. Representative scenarios are shown in Figure 1 and in the following figures. Variations of these scenarios can be tested using the interactive app developed to accompany this paper (https://fewevethanol-jdoaeeagkxf7qotbyyrybk.streamlit.app/, accessed on 21 June 2024).

As EV penetration increases significantly, according to the assumptions that form our starting point, liquid fuel demand will decrease, including demand for ethanol. In our low-uptake case (25% EV sales by 2030), demand for ethanol decreases by 63%, from 54 to 20 billion liters by 2050, as shown in Figure 2.

3.2. Area of Corn Planted

The United States is the largest producer and consumer of corn products. Corn is widely cultivated due to its multitude of uses, including food products, livestock feed, and ethanol [28]. Corn is one of the most planted crops in the US, with about 90 million acres of cropland devoted to corn, an amount that has continued to grow year over year for the past two decades (although planted acreage is still less than it was at the beginning of the 20th century) [9]. While the acreage has shifted throughout the century, total production itself has dramatically increased as farming techniques became more efficient, especially with the advent of chemical fertilizers starting in the 1950s. However, the increase in corn production by about five billion bushels (with 39.37 bushels equaling one metric tonne) over the past two decades may be linked almost entirely to the rise in ethanol production, which accounts for 45% of total corn use today [28].

Decreased demand for ethanol implies a decrease in harvested corn acreage by about 25 million acres, as shown in Figure 3 for the three scenarios. Coupled with ongoing yield improvement trends, acreage planted in corn used for ethanol shows a decline even more quickly than the demand for corn in our scenarios, starting in the historical data. This analysis does not take into account which other crops might be planted in place of corn, nor does it consider potential impacts of climate change such as increasing growing degree days, increasing killing degree days, droughts, and extreme weather events [29,30,31,32].

As of 2023, over 50% of US corn is grown in only four states: Iowa (16.4%), Illinois (14.8%), Nebraska (11.3%), and Minnesota (9.9%) [33]. These rankings have remained relatively constant since 2000, with the corn production of different states shifting only slightly between then and the present day. Within these high-producing states, corn production has increased significantly since 2000. Iowa, Illinois, Nebraska, and Minnesota, which make up approximately half of total production, increased their production by between 35% and 50%, a total of 2.3 billion bushels in 2022 compared to 2000. Significant increases in production have occurred for all other top corn-producing states as well.

3.3. Irrigation

Although only about 10–15% of the US corn crop is irrigated, a significant fraction of irrigated corn is grown in areas with stressed aquifers, as much 87% according to one report [34,35]. Therefore, reducing the need for irrigated crops would be a contribution to sustainable water and aquifer management. Based on the reduction in corn ethanol demand, a judicious choice to reduce the planting of corn in irrigated areas could save about 17 Gm³ of groundwater, as shown in Figure 4. Since currently, a maximum of about 10 million acres of corn are irrigated, the savings will saturate rather quickly as more and more corn is displaced, including corn from non-irrigated areas.

More important than the absolute magnitude of the decrease in water demand is the determination of the areas that are water-stressed and for which decreases in withdrawals of groundwater would represent a sustainability co-benefit of reduced corn cropping.

3.4. Nutrient Use and Runoff

Reducing the size of the corn crop can also result in decreases in the use of nutrient inputs such as nitrogen, phosphate, and potash used as fertilizers. Large fractions of corn acreage use these inputs (98%, 80%, and 63%, respectively). In the scenario with 50% EV sales fraction by 2030, the savings in total fertilizer use compared to current values is shown in Figure 5 The data shown in Figure 5 represent the fraction of total nutrient reductions for all crops, not just corn, as corn fertilizer represents roughly 45% of total nutrient application [36]. Reducing nutrient inputs (not only by reducing the acreage of planted and harvested corn) directly results in a reduced runoff of nutrients to waterways as well as economic damages, possibly over an extended period of time [37,38,39,40].

3.5. Substitution of Corn by Solar Photovoltaics

The efficiency of land use is important, and increasingly, there are conflicts in rural areas between the farmers who wish to use some of their land for large-scale solar arrays and those who wish to preserve farmland for crops. Although the argument can be made that the transition discussed in this paper is the substitution of one industrial product (monoculture corn made into ethanol for transportation use) for another one (utility-scale solar photovoltaic arrays), rather than a fundamental question of “farms” vs. “industry,” the point that can be made from the current approach is that a relatively small fraction of farmland that is currently used for ethanol production, and which therefore will not be needed for that purpose if a transition to electric mobility is made, could be instead used for generating renewable (here, solar pv) electricity that will be needed to assist the transition. Figure 6 shows the amount of electricity that can be generated by substituting 7% of decreased ethanol corn cropland for solar pv, given in terms of the estimated fraction this would supply for all expected EVs in the model. That is, if sales of EVs rise to 25%, 50%, or 75% of total LDV sales by 2030, this will increase the overall EV fleet size and thus the demand for electricity. By substituting 7% of the land no longer needed for ethanol with solar PV, 60% of all EV electricity could be generated, with a relatively conservative estimate of 1000 MWh_ac/MW_capacity efficiency. Clearly, faster EV growth and less substitution of land (5%) leads to a smaller fraction of EV demand covered of about 40%; conversely, 10% substitution and slower EV uptake allows more than 90% of the additional electricity demand from EVs to be satisfied. By extension, with 50% EV sales by 2030 and 10–12% of current corn-for-ethanol land used for solar PV, 100% of the additional electricity demand can be satisfied. Additional cases can be tested using the interactive app developed to accompany this paper (https://fewevethanol-jdoaeeagkxf7qotbyyrybk.streamlit.app/, accessed on 21 June 2024).

3.6. Net Energy Considerations and EROEI (Energy Return on Energy Input or Investment)

Net energy is the amount of energy remaining after accounting for the energy costs of the production of a fuel or electricity [41]. Energy Return on Energy Investment (EROEI) is the ratio of the amount of energy a source requires to deliver a unit of net energy to society compared to the energy flows involved in all stages of the production process [41]. More specifically, EROEI is a metric commonly used to assess the energy “profitability” of different energy production technologies, with EROEI > 1 indicating that more useful energy is delivered than what is used during the energy production process for that technology [41]. Even an EROEI < 1 is not necessarily enough to disqualify an energy source as being useful—thermally generated electricity certainly is such a case, but with an output (electricity) that is far more flexibly useful than the input energy sources (coal or natural gas).

Since the 1990s, estimates of the EROEI of corn ethanol in the US have undergone a gradual increase, with a 2023 review reporting the EROEI of corn ethanol to be approximately 1.2 [42].

The EROEI of solar PV technology has also undergone a gradual increase over time as technology has improved. Comparing the EROEIs of solar PVs to that of corn ethanol over the past two decades reveals that solar PV has higher EROIs compared to the EROIs of corn ethanol. A meta-analysis review assessing EROEIs of solar PVs from 2000 to 2013 found that the mean harmonized EROEI varied from 8.7 to 34.2 [43]. More recently, a 2022 study reported that wind, solar PV, and hydropower all have EROEIs at or above 10 [41], while a 2023 review reported that the EROEI of solar PV is around 8 [42]. These comparatively higher EROEIs for a solar PV of 10 or more indicate that the technology is delivering over 90% of the energy it produces to society as net energy, while the much lower reported EROEI values of corn ethanol indicate that it is delivering far less [41]. In the study from 2023, it was reported that 88% of the total energy from solar PVs goes directly to society, while 12% is offset by production requirements; and in contrast, 20% of the total energy created from corn ethanol goes to society, while 80% is offset by production requirements [42]. These findings suggest that converting US farmland currently used to grow corn for ethanol into solar PV arrays would generate significantly higher yields of net energy to the US transportation sector. Furthermore, since electric motors are three to four times more efficient than internal combustion engines, the advantage in energy terms for the production of useful final energy services is even greater [42].

3.7. Economic Considerations—Ethanol Producers and Farmers

The US Department of Agriculture tracks the costs of inputs to corn growing, both in terms of operating costs and allocated overhead costs [44]. When all costs are included, and depending somewhat on the region, the net value of corn production averaged over the period from 2005 to 2022 and without government payments has ranged from 48 USD/acre in the “Heartland” region (roughly Iowa, Illinois, Indiana, and Missouri, with parts of Minnesota and Ohio), to 2 USD/acre in the “Prairie Gateway” region (Kansas and part of Nebraska, relevant for corn), to 4 USD/acre in the “Northern Great Plains” region (parts of Nebraska and Minnesota and the Dakotas) [44]. All of these regions show large fluctuations from year to year. Operating margins for corn ethanol demonstrate equally large variations and, when taking into account full operating as well as estimated capital costs, are rather small, averaging about 0.05 USD/gallon [22]. There is also uncertainty in the available income-generating models for farmers through solar PV electricity generation. Therefore, the two cases described in this section should be viewed as only indicative of potential alternative income streams to ethanol.

Taking that value as a guideline, we calculated the total net income for ethanol industry farms for the case of decreasing ethanol demand. At the same time, and given the baseline assumption of 7% land substitution and lease rates of 1000 USD/acre for solar PV projects [21], in Figure 7, we show how leasing a fraction of land to a PV developer would slow the decrease in income from lost ethanol revenue, aggregated across the two income streams. An additional possible incentive for a farmer, but not taken into account here, is that the solar PV lease income would be guaranteed for 20–30 years, whereas yearly net income from corn ethanol has been very volatile over the past two decades and dependent on federal subsidies.

Another potentially more lucrative model for landowning farmers would be to become solar developers. With current typical PPA prices for utility-scale projects being 30–40 USD/MWh in the Midwest [45], we compare ethanol income to potential solar PV income, as shown in Figure 8. This pathway would be considerably more complicated for a farm owner to follow but represents at a basic level the potential overall macroeconomic benefits of solar PV as opposed to ethanol production.

Note that the results shown in Figure 7 and Figure 8 are incomplete, since the additional solar income from 10% of the land no longer needed for ethanol production means that 90% of the corn ethanol land could still be used for other purposes or even be allocated (or returned) to farmland conservation programs, which have their own value to farmers.

3.8. Employment Factors

For employment in the ethanol industry, an employment factor was calculated by finding the average ethanol production from 2015 to 2022 [9]. Dividing the total number of direct jobs (35,000) [46] by the average production of ethanol (53 billion liters) resulted in 660 jobs per billion liters. Jobs in ethanol production were broken down into two groups, with 45% of jobs being in agriculture and 55% in manufacturing, wholesale trade, and business services [46]. Agriculture thus represents 300 jobs per billion liters, and the other segments represent 360 jobs per billion liters.

For the solar PV industry, we use literature values for employment factors, divided into construction and installation jobs, at 3 jobs/MW of capacity installed, and operation and maintenance jobs, with an employment factor of 0.1 jobs/MW of operating capacity [24]. Figure 9 shows the results for total employment in the two industries, with corn agriculture plus ethanol production on the one hand and solar PV construction plus maintenance jobs on the other hand. As is to be expected, as time goes on, the number of construction jobs peaks and declines, whereas the number of operation and maintenance jobs continues to increase with increasing installed capacity.

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

4. Discussion

Starting from an assumption that trends in personal vehicle electrification will proceed quite rapidly over the next decade and beyond, a number of direct consequences follow. The first and most obvious of these is that demand for gasoline will decrease, and since ethanol is currently mixed with gasoline at an average concentration of 10% in the US, demand for ethanol will also decrease. Measures could be, and will be, undertaken to extend the use of ethanol from corn, for example, by allowing for increased mixing percentages and for subsidizing corn ethanol for the aviation industry [12,48], and these will likely be independent of evaluations as to the ultimate GHG emissions advantages of EVs [49] and still-controversial and questionable emissions reduction potential for corn ethanol [50].

Our scenarios do not evaluate the likelihood of the transition to EVs taking place as rapidly as postulated. However, given incentives, policies, and manufacturer commitments with varying degrees of certainty, together with recent historical examples of rapid EV sales growth in some regions and countries, this sector could conceivably be near a tipping point toward the acceptance of EVs more broadly. It appears that other aspects of the ongoing energy transitions have tended to catch incumbent technologies by surprise, e.g., rapid growth in solar PV capacity installation and rapid decrease in cost over the past ten years. Once the EV transition as a driver of concomitant changes takes hold, there will potentially be a relatively short time for industry and policy makers to react and generate appropriate responses.

The cascade of consequences or co-benefits of the transition away from ICEVs encompasses a dynamic that is somewhat unique globally. With the exception of Brazil, no other country has encouraged the large-scale use of ethanol in the liquid fuels sector. In Brazil, the use of sugar cane as the feedstock for bioethanol is considerably more efficient in terms of land, water, fertilizer, and input energy than corn ethanol in the US [51,52], and it has been suggested that GHG emissions can be reduced even further by using the “waste” from sugarcane to generate electricity for hybrid electric vehicles [53]. In the US, there are significant political pressures, mainly in corn-growing states, that will make policy decisions about how best to move away from corn ethanol (or whether to do so) quite challenging and likely only determined at the margins by purely scientific calculations.

Our analysis is idealistic in that changes in demand for ethanol would trigger a set of decisions based on environmental concerns, coupled with socioeconomic factors. Reducing corn planting preferentially where irrigation is needed and where aquifers are stressed would be one criterion. There is also evidence that corn ethanol production has implications for the amount of land in the Conservation Reserve Program [54] and on critical habitats for endangered species [55]. There may be potential for decreasing subsidy support for ethanol with replacement subsidies, at least temporarily, if the changes would help ameliorate environmental stressors. We also implicitly assume that land taken out of corn ethanol production for US transportation will not be used for corn ethanol in other applications or for increased exports. Thus, our calculations for reductions in land use, fertilizer application (and concomitant runoff), and water consumption will all depend on a number of interacting factors.

As the shift in energy systems is made toward electrification with zero-carbon sources, the energy system as a whole will become more complex; an early example of this was precisely the introduction of the Renewable Fuels Standard in the U.S., which immediately coupled the food and energy sectors in ways that had not been the case previously. Navigating various trade-offs and potentially conflicting goals will be at the heart of the energy system transformation challenge. Although this work has presented a stark contrast between the use of ethanol as a fuel additive in ICEVs and the use of energy by EVs, analyses unsurprisingly show that EVs alone will not be enough, even within the transport sector, to meet pledged climate targets [56] and also show that solutions will be regionally dependent [53].

Since there are a number of parameters that can influence the outputs discussed in this paper, an online app has been developed to allow for the interactive changing of input parameters, including rates of sales penetration, fraction of farmland used for solar PV, and ethanol and PV net income rates. The app can be found at https://fewevethanol-jdoaeeagkxf7qotbyyrybk.streamlit.app/ (accessed on 21 June 2024).

5. Conclusions

The transition from a fossil fuel-based energy system to a sustainable, renewable energy paradigm entails increased complexity in inter-sectoral interactions. This paper explores the implications of electric vehicle (EV) adoption on the corn ethanol sector in the United States across various domains across the food, energy, and water (FEW) nexus. We examine scenarios of EV sales growth and their impacts on corn acreage, water and fertilizer usage, potential for solar photovoltaic (PV) energy, net energy considerations, economic impacts on ethanol producers and farmers, and employment factors. The shift toward renewable energy and the electrification of transportation, the rapidity of which has caught many by surprise, has prompted a reassessment of energy sources, notably corn ethanol, historically seen as a potential gasoline substitute for decarbonization pathways. However, with the rise in EVs fueled by decreasing battery costs, the focus has shifted. Three EV sales growth scenarios are considered, reflecting different adoption rates that are plausible based on government policies, as well as stated plans and goals of manufacturers. Even with aggressive EV sales growth, fossil fuel ICEVs will remain in the transportation sector by 2050, albeit at reduced levels. However, declining demand for liquid fuels and therefore for ethanol implies reduced corn acreage. This decline could lead to shifts in agricultural practices, impacting regions heavily reliant on corn production. The co-benefits of reduced corn cultivation could include alleviated water stress and decreased fertilizer usage, contributing to sustainable agricultural practices and environmental conservation. Current corn acreage could be repurposed in part for solar PV installations, potentially meeting a significant portion of the additional electricity demand from EVs. The literature shows a higher energy return on investment for solar PV compared to corn ethanol, suggesting a more efficient allocation of resources toward renewable energy sources. The economic implications for ethanol producers and farmers may include the mitigation of income loss through solar PV leasing or transitioning to solar development. Employment projections highlight potential shifts in job markets, with opportunities arising in the solar PV industry alongside challenges for those dependent on the ethanol sector. Thus, the transition to EVs presents both challenges and opportunities across several sectors. Understanding these implications is crucial for policymakers, industry stakeholders, and agricultural communities navigating the evolving energy landscape.

While acknowledging the potential benefits such as decreased greenhouse gas emissions and enhanced resource efficiency associated with EVs, the complexities and trade-offs involved in this transition are acknowledged. Replacing gasoline and diesel fuel with corn ethanol can result in somewhat reduced GHG emissions, but the only clear path toward a Paris Agreement-compatible target of near-zero emissions is through renewable electricity and the electrification of transportation. This was, however, not the focus of the present paper. Another FEW consideration that is outside of the scope of the paper itself but nonetheless important for a complete sustainability evaluation is the impact that EV production will have. The batteries required for EVs must made from mined resources that require water resources and have socioeconomic implications; as EVs become more popular and accessible, as envisioned in the scenarios used in the present work, resource use and sustainability pressures will also increase. Zooming out further, it is worth mentioning that EVs are not the only alternative to ICEVs, and if measures are taken to improve public transport infrastructure in the US, there may not be a one-to-one replacement of personal LDVs or continued expected growth of car sales.

This paper highlights the need for further investigation into several key areas, including more a granular understanding of the economic viability and sustainability of ethanol production while demand is declining, as well as the broader implications for agricultural practices, water management, and rural economies. Future research endeavors could delve deeper into understanding the socio-economic impacts of shifting land usage from ethanol production to solar photovoltaic installations, interviewing large stakeholders, exploring alternative livelihood opportunities for affected communities, and devising strategies for equitable and sustainable transitions. Additionally, a continued analysis of net energy considerations, such as Energy Return on Investment (EROI), should be taken into account in guiding policy decisions and investment priorities toward a more resilient and environmentally sound energy future.