Nashville, Tennessee, is undergoing rapid urbanization and population growth, bringing increased traffic congestion and air quality challenges to the city’s core. Against this backdrop, flex fuel vehicles (FFVs) have become more common on Nashville’s streets, often marketed as a greener alternative to conventional gasoline cars. These vehicles can operate on gasoline, E85 (a blend of 85% ethanol and 15% gasoline), or any mixture in between. While FFVs offer the promise of reduced fossil fuel dependence and lower tailpipe carbon emissions, their real environmental footprint depends heavily on how the ethanol fuel is produced, transported, and consumed. For Nashville’s urban environment, the net effect is complex and warrants a closer look at both the benefits and the trade-offs.

What Are Flex Fuel Vehicles and How Do They Work?

Flex fuel vehicles are essentially standard internal combustion engine cars, trucks, or SUVs that have been modified to run on high-ethanol blends. They are equipped with a fuel composition sensor that detects the ethanol-gasoline ratio in the tank and adjusts the engine’s timing, fuel injection, and air-fuel mixture accordingly. This flexibility allows FFVs to use any combination of unleaded gasoline and E85 — from pure gasoline up to 85% ethanol — without needing separate tanks or driver intervention.

Engine manufacturing costs for FFVs are only slightly higher than conventional vehicles, and most major automakers — including Ford, General Motors, Chrysler, Toyota, and Nissan — have produced millions of FFVs over the past two decades. In fact, many drivers may own an FFV without knowing it; a yellow gas cap or a “FlexFuel” badge on the rear of the vehicle are common indicators. The U.S. Department of Energy’s Alternative Fuels Data Center provides a searchable database of FFV models.

E85 contains roughly 85% ethanol and 15% gasoline. The high oxygen content of ethanol allows the fuel to burn more completely in the engine, which can reduce certain pollutants. However, ethanol contains less energy per gallon than gasoline — about 27% less — meaning FFVs running on E85 typically experience a reduction in fuel economy. Drivers must balance the lower price of E85 (often 20–30% cheaper than regular gasoline) against the need to refuel more frequently.

The Promise of Flex Fuel: Environmental Benefits

Supporters of flex fuel technology point to several environmental advantages, especially when E85 is produced from sustainably grown feedstocks. Ethanol is a renewable fuel made from corn, sugarcane, or cellulosic biomass, and its use can reduce lifecycle greenhouse gas (GHG) emissions compared to gasoline.

Reduced Lifecycle Carbon Emissions

According to the U.S. Environmental Protection Agency, the Renewable Fuel Standard (RFS) requires that corn‑based ethanol achieve at least a 20% reduction in lifecycle GHG emissions relative to gasoline. Advanced biofuels, such as cellulosic ethanol, can achieve reductions of 60% or more. When FFVs burn E85, the carbon dioxide released during combustion is partially offset by the CO₂ absorbed by the corn plants during growth. This creates a somewhat closed carbon cycle, especially if the farming and processing operations are energy-efficient.

In Nashville’s urban areas, a shift from gasoline to E85 could help the city meet its Climate Action Plan goals. The Nashville-Davidson County Sustainability Division has set targets for reducing community‑wide GHG emissions by 80% by 2050. Incorporating low‑carbon fuels is one of several strategies, alongside electric vehicle adoption and transit improvements.

Lower Tailpipe Emissions of Certain Pollutants

Ethanol has a high octane rating (about 109 for E85 vs. 87–93 for regular gasoline), which allows for higher compression ratios and more efficient combustion. When burned, ethanol emits less carbon monoxide, fewer particulate matter (PM) emissions, and lower levels of harmful aromatic hydrocarbons such as benzene. For Nashville, where ground‑level ozone and PM2.5 are occasional concerns — particularly in the summer months — any reduction in smog-forming pollutants can benefit public health, especially for children, the elderly, and individuals with respiratory conditions.

Support for Local Agriculture and Energy Independence

Tennessee is a significant corn‑growing state; in 2023, farmers harvested over 1 million acres of corn, much of which goes to ethanol production. Using locally produced ethanol in Nashville’s FFVs reduces dependence on imported oil and keeps energy dollars within the state. Ethanol plants also create jobs in rural communities and support the agricultural economy. The Tennessee Department of Agriculture notes that the biofuels industry has become an important part of the state’s renewable energy portfolio.

The Other Side of the Coin: Environmental Costs and Challenges

Despite the benefits, the environmental impact of ethanol production is subject to intense debate. Concerns about land use, water consumption, fertilizer runoff, and indirect market effects can significantly diminish or even negate the theoretical GHG reductions.

Land Use Change and Deforestation

Large‑scale corn farming requires vast tracts of land. When existing grasslands, forests, or wetlands are converted to cropland to meet ethanol demand, carbon stored in native vegetation and soils is released into the atmosphere. This is known as indirect land‑use change (ILUC). A widely cited study published in Science found that when emissions from land‑use change are included, corn‑based ethanol may have a larger carbon footprint than gasoline. Although more recent models have refined these estimates, the debate remains active. For Nashville, the local environmental cost is not directly visible, but it contributes to the global carbon cycle that affects regional climate.

Water Use and Agricultural Pollution

Corn is a water‑intensive crop, and irrigation in certain regions can strain local water resources. In Tennessee, rainfall generally meets corn’s needs, but fertilizer and pesticide runoff from cornfields can flow into the Mississippi River basin and eventually contribute to the Gulf of Mexico’s hypoxic “dead zone.” Nitrogen and phosphorus from agricultural runoff fuel algal blooms that deplete oxygen in coastal waters, harming marine life. This is a distant but real consequence of ethanol production that supports Nashville’s FFVs.

Energy Balance and Well‑to‑Wheels Efficiency

Producing ethanol involves substantial energy inputs: diesel for farm equipment, natural gas for fertilizer production, electricity for ethanol plants, and fuel for transportation. The ratio of energy output to fossil energy input for corn ethanol is estimated at 1.3 to 1.6, meaning the ethanol delivers only 30%–60% more energy than the fossil energy used to produce it. In contrast, gasoline has a well‑to‑wheels fossil energy ratio of about 0.85 (i.e., it takes 85 units of fossil energy to deliver 100 units of gasoline). While corn ethanol does yield a modest net energy gain, the emissions associated with fossil fuel inputs must be counted.

Furthermore, because E85 has lower energy density, an FFV burning E85 will emit about the same amount of CO₂ per mile — or slightly less — than a comparable gasoline vehicle only if the ethanol production emissions are low. Under average conditions, using E85 in today’s FFVs results in a 10–20% reduction in lifecycle GHG emissions, according to the Argonne National Laboratory’s GREET model. However, achieving the upper end of that range requires efficient farming, low‑carbon processing, and minimal land‑use change.

Nashville’s Urban Landscape: Unique Considerations for Flex Fuel Adoption

Nashville’s specific urban conditions — climate, traffic patterns, infrastructure, and existing sustainability initiatives — influence whether FFVs can deliver real environmental benefits within the city limits.

Air Quality and Public Health in the Urban Core

Davidson County is a non‑attainment area for ozone under the Clean Air Act, meaning it fails to meet the National Ambient Air Quality Standard for ground‑level ozone. Ozone is formed when volatile organic compounds (VOCs) and nitrogen oxides (NOx) react in sunlight. Ethanol blends can reduce tailpipe VOCs and aromatics, but they may increase NOx emissions in some engine calibrations. Studies on the net impact of E85 on ozone formation are mixed; the outcome depends on the specific vehicle fleet and meteorological conditions. For Nashville, a broad switch to E85 could slightly improve or worsen ozone, depending on how newer engines are tuned. Careful monitoring and updated engine calibrations are essential.

The Nashville Area Metropolitan Planning Organization (MPO) and the Tennessee Department of Environment and Conservation (TDEC) have partnered to promote alternative fuels through the Nashville Clean Cities Coalition. Increasing the availability of E85 is one of the coalition’s strategies to reduce mobile‑source emissions. If the ethanol blend used is produced sustainably, the combination of lower lifecycle carbon and reduced air toxics could improve overall urban air quality.

Infrastructure Gaps and Fuel Availability

As of 2025, Nashville has fewer than 20 public E85 fueling stations, compared to hundreds of gasoline stations. Most E85 pumps are concentrated on the outskirts of the city or near major highways, making it inconvenient for downtown residents and commuters to fill up with high‑ethanol fuel. Expanding the network requires investment from fuel retailers, who are often hesitant due to lower demand and the cost of retrofitting storage tanks and dispensers for ethanol‑compatible materials. Without a robust network, many FFV owners in Nashville will continue to fill up with gasoline, negating any environmental benefit.

Local policies — such as grants for station conversion or requirements for new fueling stations to include at least one alternative fuel option — could accelerate infrastructure growth. The U.S. Department of Energy’s Alternative Fueling Station Locator shows that Kroger, Shell, and Mapco are among the chains that have installed E85 pumps in the Nashville area, but coverage remains sparse.

Traffic Patterns and Drive‑Cycle Effects

Nashville’s urban core experiences stop‑and‑go commuting, especially on interstates I‑24, I‑40, and I‑65. Ethanol’s higher latent heat of vaporization can reduce in‑cylinder temperatures, which may help suppress NOx formation under high load conditions. However, during cold starts and short trips — common in urban driving — ethanol’s lower volatility can cause harder cold starts and increased emissions of unburned hydrocarbons. Modern FFVs compensate with engine programming, but real‑world urban driving may still produce slightly higher emissions of some pollutants compared to highway cruising. Nashville’s fleet mix and daily drive cycles must be considered when modeling the net impact of FFVs.

Comparative Perspective: Flex Fuel vs. Other Clean Vehicle Technologies

To put FFVs in context, it is helpful to compare them with other options available to Nashville drivers: battery electric vehicles (BEVs), plug‑in hybrids (PHEVs), and conventional hybrids.

Vehicle TypeLifecycle GHG Reduction (vs. avg gasoline)*Local Air Quality BenefitInfrastructure Needs
Gasoline FFV on E8510–20%Moderate (reduced CO, PM, aromatics)Few E85 stations needed
Conventional Hybrid25–35%Lower fuel consumption, same tailpipe per mileNone
Plug‑in Hybrid (PHEV)30–50% (depending on electric miles)Zero‑emission electric modeCharging stations
Battery Electric Vehicle (BEV)50–70% (grid average)Zero tailpipe emissionsExtensive charging network

*Note: Reductions are approximate and depend on fuel source, driving patterns, and the electricity grid mix. BEVs charged on a high‑renewables grid can achieve 90%+ reductions.

While FFVs offer a moderate reduction in greenhouse gases and are compatible with existing refueling habits, they lag behind hybrids and EVs in both efficiency and tailpipe pollution. However, FFVs cost little to nothing more than a conventional gasoline car, making them an accessible entry point for many drivers. For Nashville residents who cannot afford a hybrid or EV, switching to E85 when available represents a step in the right direction — provided the ethanol is sustainably sourced.

Policy and Incentives: Driving the Future of Flex Fuel in Nashville

Federal and state policies play a critical role in shaping the adoption of FFVs and the demand for ethanol. The Renewable Fuel Standard (RFS) mandates that a certain volume of renewable fuel be blended into the nation’s transportation fuel supply, creating a market for ethanol. Tennessee offers a state excise tax exemption for E85 fuel (reducing the tax by $0.04 per gallon), which helps lower the pump price for consumers. Additionally, the Tennessee Valley Authority (TVA) has partnered with local utilities to fund electric vehicle charging infrastructure, but similar programs for ethanol fueling stations are less common.

Nashville’s own sustainability initiatives could be enhanced by targeted policies: for example, requiring that a percentage of the city’s fleet vehicles be FFVs and giving preference to E85 fueling contracts could demonstrate leadership. Public awareness campaigns are also needed to educate drivers about the availability of E85 and their vehicle’s flex fuel capability — many FFV owners do not know they can use E85. The Alternative Fuels Data Center offers resources and a vehicle look‑up tool.

Conclusion: A Balanced Path Forward for Nashville

Flex fuel vehicles are not a silver bullet for Nashville’s transportation environmental challenges, but they can be part of a diversified strategy alongside electrification, improved public transit, and active transportation. The key to maximizing the benefit of FFVs lies in producing ethanol with minimal environmental harm — through sustainable farming practices, reduced fertilizer use, and eventually cellulosic feedstocks from waste materials. Locally, expanding the E85 fueling network and integrating FFVs into fleet operations can provide incremental emissions reductions while EV technology matures and becomes more affordable.

For the Nashville resident driving an FFV, the choice to fill up with E85 is a meaningful one — provided the fuel is available and the price is right. City leaders and advocacy groups should work together to close infrastructure gaps, provide accurate consumer education, and support policies that reward the cleanest forms of ethanol. By taking a measured, evidence‑based approach, Nashville can ensure that flex fuel vehicles contribute positively to the city’s air quality and climate goals without ignoring the broader environmental consequences of ethanol production.