Is Ethanol Worse for the Climate Than Gasoline? An In-depth Analysis

Examining new studies and debates over the climate impact of corn-based ethanol compared to gasoline.

By Sneha Tete, Integrated MA, Certified Relationship Coach

Created on Sep 27, 2025

Examining new studies and debates over the climate impact of corn-based ethanol compared to gasoline.

For decades, corn-based ethanol has been promoted in the United States as a key element in reducing greenhouse gas emissions and dependence on fossil fuels. The Renewable Fuel Standard (RFS), established in 2005, mandated the blending of billions of gallons of ethanol into the nation’s gasoline supply – an effort broadly marketed as a climate-friendly move. However, a recent peer-reviewed study challenges this narrative, suggesting that modern ethanol production may, in fact, be more harmful to the climate than conventional gasoline. This article explores the findings, controversies, methodologies, and what this means for the American renewable fuel policy moving forward.

The RFS: Background and Policy Goals

The Renewable Fuel Standard (RFS) was introduced with bipartisan support to reduce greenhouse gas (GHG) emissions, provide a boost to the U.S. agricultural economy, and cut energy reliance on foreign oil. It requires oil refiners to blend increasing amounts of renewable fuels, especially ethanol, into gasoline. Proponents argued this would lower carbon emissions and create a significant market for U.S. corn, especially benefiting states like Iowa – the top corn producer, with about half the crop used for ethanol fuel.

Goal: Cut national emissions and support domestic agriculture
Implementation: Mandated ethanol blending levels
Intended outcome: Decrease in GHG emissions compared to petroleum gasoline

What Did the New Study Find?

Recent research, funded in part by the U.S. Department of Energy and National Wildlife Federation, published in the Proceedings of the National Academy of Sciences, offers a startling conclusion: corn-based ethanol may be at least 24% more carbon-intensive than gasoline over its production lifecycle.

The researchers conducted a five-year, in-depth analysis, tracking changes in land use, fertilizer application, and emissions from both ethanol and gasoline production.
The primary driver of ethanol’s unexpected emissions: expansion of corn cultivation and associated land use change, which releases significant carbon stored in soil and increases fertilizer-related emissions.

Fuel Type	Estimated Carbon Intensity Compared to Gasoline
Corn Ethanol	At least 24% higher
Gasoline (Conventional)	–

The study highlighted that, since the implementation of the RFS, almost 7 million acres of new cropland have come into production between 2008 and 2016 – an 8.7% increase driven primarily by corn for ethanol.

Why Would Ethanol Have a Higher Carbon Intensity?

The analysis suggests several interlinked emissions sources:

Land Use Change: Growing demand for corn caused conversion of grasslands and other non-agricultural lands into croplands. Tilling these lands releases carbon stored in the soil.
Fertilizer Use: Intensive corn cultivation uses substantial fertilizer, resulting in emissions of nitrous oxide, a potent greenhouse gas.
On-Farm Emissions: Fuel and energy used in planting, harvesting, and processing further contribute to the lifecycle carbon footprint.

All these factors combined led the authors to declare that, when considering all impacts, ethanol fails to deliver on its climate promises.

Industry Response and Counterarguments

Ethanol producers and agricultural groups challenged the study’s assumptions and findings. Geoff Cooper, president of the Renewable Fuels Association, argued the research employed “a series of worst-case assumptions” and “cherry-picked data,” suggesting that more inclusive, up-to-date industry data would lead to very different conclusions.

Main counterpoints from the ethanol industry:

Independently reviewed studies by Harvard, USDA, and DOE’s Argonne National Laboratory estimate corn ethanol reduces GHG emissions by 40-50% compared to gasoline.
Modern farming is more efficient: corn yields have increased, meaning more ethanol can be produced per acre with less environmental impact.
Overall U.S. cropland has declined, and current corn acreage is similar to levels prior to the RFS, undermining claims of massive new land conversion.
Technological innovation: Use of cover crops, better fertilizer management, and cleaner refinery processes are significantly lowering ethanol’s lifecycle emissions.

Supporting Studies: Ethanol’s Green Credentials

The U.S. Department of Agriculture (USDA) and allied studies have shown that lifecycle emissions from ethanol are about 39% lower than gasoline, with potential for reductions of over 70% as technology advances.
Improved modeling of so-called indirect land use change (iLUC) has resulted in significantly lower emissions estimates for ethanol than early critics projected.
Switching to higher-ethanol blends in gasoline (E15, E85) further reduces overall carbon emissions and hazardous air pollutants.

One report summarized: “The lifecycle carbon intensity of today’s ethanol is about 46% lower than gasoline’s carbon intensity.”

Disagreement Over Land Use Change

Land use change (LUC) stands at the heart of the debate between ethanol detractors and backers. Critics argue that increased demand for corn incentivizes plowing up prairies and grasslands, releasing previously sequestered carbon. However, industry experts and agencies counter that overall U.S. cropland actually shrank during the period in question, and that yield increases (not acreage hikes) account for rising ethanol output.

According to recent USDA and EPA data:

Annual average corn yields have risen from about 150 bushels per acre in the early 2000s to nearly 180+ bushels per acre today.
The actual amount of fertilizer per bushel of corn has decreased by over 50% for nitrogen and by nearly 70% for phosphate and potash since 1970.
Modern techniques allow for more efficient fertilizer use, further reducing per-bushel emissions.

Environmental and Public Health Impacts Beyond Carbon

Beyond their climate implications, fuel blends and refinery processes affect public health and the broader environment:

Ethanol Blends and Air Quality: Higher ethanol blends reduce the concentration of aromatics (hazardous air pollutants) in gasoline, with potential expansions in E15 and E85 lowering respiratory and cardiovascular risks.
Water Quality and Pesticide Use: Critics of ethanol underscore ongoing concerns about fertilizer and pesticide runoff from intensified corn plantations. These can contribute to ‘dead zones’ via nitrate runoff in water bodies, regardless of carbon accounting debates.

The Bigger Picture: Biofuels, Electric Vehicles, and U.S. Energy Policy

With the White House’s increased interest in electric vehicles (EVs), many see a crossroads for U.S. biofuels policy. Iowa and other agricultural states continue to advocate for the expansion of E15 blends (15% ethanol), directly tying the economic health of rural regions to ethanol sales. Others argue that investments should shift toward supporting EV infrastructure, with the fastest emission reductions resulting from full electrification of transit.

Economic Factor: Biofuel production is tightly interwoven into the Midwestern agricultural economy.
Policy Dilemma: Should subsidies and mandates support incremental emissions reductions from ethanol, or be redirected to accelerate the transition to zero-emission vehicles?

Frequently Asked Questions (FAQs)

Q: Is corn-based ethanol truly worse for climate than gasoline?

A: According to one recent five-year study, it may be at least 24% more carbon-intensive than gasoline when accounting for land use change and fertilizer emissions. However, several other major studies from the USDA, Department of Energy, and Harvard find that ethanol’s lifecycle emissions are 40-46% lower than gasoline. The precise answer depends on which models and assumptions are used.

Q: What are the main contributors to ethanol’s carbon footprint?

A: The largest contributors are emissions from land use change (tilling new acres for corn), fertilizer-related emissions, and fossil fuel energy used in producing and refining ethanol.

Q: Has the expansion of ethanol production increased overall cropland?

A: The new study claims around 7 million new acres came into production for ethanol corn between 2008-2016. However, federal data shows that on a national scale, total cropland has not significantly increased, and improved yields account for most of the rise in corn production.

Q: Can ethanol production become more sustainable?

A: Yes. Technological innovations such as precision agriculture, reduced tillage, use of cover crops, efficient fertilizer practices, and continued improvements at ethanol plants can lower lifecycle emissions. Some leading analysts project a potential 70% reduction from gasoline’s emissions by 2022.

Q: What are the alternatives to corn-based ethanol for sustainable fuel?

A: Advanced biofuels using cellulosic feedstocks, algae, or waste biomass can provide much larger climate benefits, but currently face economic and logistical challenges. Electrification of vehicles bypasses the limitations of both gasoline and biofuel blends.

Key Takeaways and Future Outlook

The emissions impact of corn ethanol remains fiercely debated, hinging on land use assumptions, data models, and system boundaries.
Recent peer-reviewed research challenges the idea that ethanol is always cleaner than gasoline, largely due to land conversion and fertilizer emissions.
The ethanol industry points to rapid improvements in farming and refining efficiency, as well as more accurate modeling, to support their claim that ethanol reduces GHG emissions by 40-46%.
With the U.S. federal government prioritizing electric vehicles as a long-term decarbonization strategy, the role of ethanol – and biofuels in general – is at a policy turning point.