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“There’s a fine line between patriotism and corn.”David L. Wolper If you have ever traveled through the Midwest—particularly Illinois, Indiana, Iowa, or Ohio—you may have noticed a singular plant: corn. It is hard to miss. Fields of it stretch in every direction. It even makes an effective setting for a horror movie. But perhaps the most unsettling thing about corn is how little of the crop ends up directly on people’s plates.
In 2024, U.S. farmers harvested 14.9 billion bushels of corn at an average yield of 179.3 bushels per acre. Roughly 5.5 billion bushels—about 37 percent of the crop—were used to produce fuel ethanol.[1,2] The United States has long been the world’s largest ethanol producer, well ahead of Brazil; the 2021 global production profile below illustrates that dominance.[3] Figure 1.
Global fuel-ethanol production by country or region, 2021. Source: Renewable Fuels Association analysis of public and private data.[3] Food, fuel, and a revealing calculation How much potential food energy is represented by that corn?
At 179.3 bushels per acre and 56 pounds per bushel, an acre yields about 10,000 pounds of grain. Using a rough value of 1,500 calories per pound, that is approximately 15 million calories per acre.
Dividing the 5.5 billion bushels used for ethanol by the 2024 national yield produces an acreage equivalent of about 30.7 million acres—not 45 million acres. On paper, those acres represent roughly 460 trillion calories, or the annual caloric needs of about 570 million people at 2,200 calories per day. That is not a literal estimate of how many people could be fed. Most U.S. corn is field corn rather than the sweet corn eaten as a vegetable; diets require far more than calories; distribution, affordability, storage, and politics determine who eats; and ethanol plants return part of the grain to the feed system as distillers grains and other coproducts. Even with those qualifications, the scale of land and biological productivity committed to transportation fuel remains striking. So why convert so much potential food and habitat into fuel? Combine harvesting corn How corn became fuel policy A quick trip down history lane: U.S. gasoline prices rose sharply in 2005 and again in 2006. In response to concerns about fuel prices, greenhouse-gas emissions, and dependence on imported oil, Congress established the Renewable Fuel Standard in the Energy Policy Act of 2005 and greatly expanded it through the Energy Independence and Security Act of 2007.[4,5] The RFS remains the world’s largest biofuel mandate. Corn appeared to be an ideal candidate. It has a high starch content, and the United States already led the world in corn production. Between 2006 and 2007, planted corn acreage rose from 78.3 million to 93.5 million acres—one of the largest year-to-year increases on record—while ethanol production expanded rapidly.[2,6] Those are acreage figures, however, not billions of bushels of ethanol. Do we still need corn ethanol at its present scale? Other renewable-energy technologies have grown dramatically. U.S. wind generation, for example, rose from roughly 34 terawatt-hours in 2007 to more than 425 terawatt-hours in 2023.[7] Wind and solar do not directly replace liquid fuel in every vehicle, but electrification increasingly changes the terms of the energy-independence debate. An ethanol fuel plant in West Burlington, Iowa The disputed energy and carbon balance Whether corn ethanol yields substantially more energy than its production consumes has been debated for decades. An influential early analysis concluded that producing ethanol from corn required more fossil energy than the fuel contained.[8] Later Department of Energy analyses, incorporating coproduct credits and improvements in farming and refining, found a positive energy balance. Results depend heavily on assumptions about fertilizer, farm energy, refinery efficiency, coproducts, and land-use change.[9] The climate balance is equally contested. EPA’s Renewable Fuel Standard requires qualifying conventional renewable fuel from newer facilities to achieve at least a 20 percent lifecycle greenhouse-gas reduction relative to the petroleum baseline.[5] Yet a 2022 analysis in the Proceedings of the National Academy of Sciences concluded that, after accounting for land conversion, higher fertilizer use, and crop displacement caused by the RFS, the carbon intensity of corn ethanol was likely at least 24 percent greater than gasoline.[10] The conclusion is not that every gallon has the same footprint, but that policy-driven land-use effects can overturn apparent benefits measured only at the refinery gate. Corn also carries hidden environmental and health costs. High yields commonly require substantial nitrogen fertilizer, much of it made through the energy-intensive Haber–Bosch process. Nitrogen losses contribute to greenhouse-gas emissions, water pollution, and airborne fine particles. A 2019 study estimated that pollution associated with U.S. corn production causes approximately 4,300 premature deaths annually, with ammonia from fertilizer application a major contributor.[11] Could another crop do better? Other plants can produce ethanol more efficiently. Brazil relies primarily on sugarcane, whose sugars are more readily fermented than corn starch. Sugarcane and cassava, however, are poorly suited to cold Midwestern winters. Industrial sweet potatoes present a more intriguing possibility. Unlike sweet potatoes grown for the table, industrial sweet potatoes are allowed to develop very large storage roots. Trials in Alabama and Maryland found that selected industrial sweet-potato systems could produce more than twice as much ethanol per hectare as the national average for corn.[12] Feedstock and location Liters of ethanol per hectare Sweet potato — U.S.
average 2,608 Corn — Maryland 3,399 Corn — Alabama 3,797 Corn — U.S. average 3,880 Potato — U.S. average 4,884 Sugar beet — U.S. average 5,891 Sugarcane — U.S. average 6,195 Cassava — Alabama 6,717 Industrial sweet potato — Alabama 8,141 Industrial sweet potato — Maryland 8,839 Table 1. Estimated ethanol yield from selected carbohydrate crops. Trial locations are shown where applicable. A hectare equals 2.47 acres. Source: Ziska et al. (2009).[12] Figure 2. A conventional sweet potato (left) and an industrial sweet potato (right).
Image credits and publication permissions should be confirmed before publication. The comparison is promising, but it is not proof that industrial sweet potatoes can simply replace corn throughout the Corn Belt. Results from Alabama and Maryland cannot be assumed to hold across Iowa, Illinois, Indiana, or Ohio. A national transition would also require suitable cultivars, mechanized harvesting, storage systems, processing infrastructure, reliable markets, and careful assessment of water use, soil impacts, crop rotations, disease pressure, and farm economics. Sweet potatoes generally require less nitrogen fertilizer than high-yield corn, but their performance and inputs vary by soil, climate, and management.[12,13] Still, the trial data invite a useful thought experiment.
If a crop yielded twice as much ethanol per acre as corn, the approximately 30.7 million acre-equivalents associated with the 2024 ethanol feedstock could theoretically be reduced to about 15.4 million acres. The remaining land—roughly 15 million acres—might support food production, other crops, or restored native habitat. That is an illustration of biological potential, not a deployment forecast.