The environmental costs of corn: should the US change how it grows its dominant crop? | Farming
This article was produced in partnership. with Projector
For decades, corn dominated American agriculture. It spans 90 million acres, about the size of Montana, and finds its way into everything from animal feed and processed foods to the ethanol that’s mixed into most of the nation’s gasoline.
But a growing body of research reveals that the U.S. obsession with corn comes at a high price: The fertilizer used to grow it is warming the planet and polluting water.
Corn is vital to the rural economy and the world’s food supply, and researchers say the problem is not the corn itself. This is how we raise it.
Corn farmers rely on heavy fertilizer use to maintain today’s high yields. When the nitrogen in fertilizer breaks down in the soil, it releases nitrous oxide, a greenhouse gas almost 300 times more powerful than carbon dioxide. Producing nitrogenous fertilizer also releases large amounts of carbon dioxide, increasing the climate footprint.
The corn and ethanol industries insist that the rapid growth of ethanol, which now consumes 40% of the U.S. corn crop, is a net environmental benefit and strongly oppose research suggesting otherwise.
The industry is also pushing for ethanol-based jet fuel and high-ethanol gasoline blends as growth in electric vehicles threatens long-term gasoline sales.
Studies show that agriculture accounts for more than 10% of U.S. greenhouse gas emissions, and corn uses more than two-thirds of all nitrogen fertilizer nationwide; making it a leading driver of agricultural nitrogen oxide emissions.
Since 2000, U.S. corn production has increased nearly 50%, further exacerbating the crop’s impact on climate.
The environmental costs of corn rarely make headlines or become the subject of political debate. Much of the dynamic traces back to federal policy and the powerful corn and ethanol lobby that helps shape it.
The Renewable Fuel Standard (RFS), adopted in the mid-2000s, required gasoline to be blended with ethanol, a biofuel derived almost entirely from corn in the United States. This order increased the demand and prices of corn and encouraged farmers to plant more corn.
Many people plant corn on the same land every year. The practice, called “continuous maize,” requires large amounts of nitrogen fertilizer and results in particularly high emissions of nitrous oxide.
At the same time, federal subsidies make growing corn more profitable than diversifying. Taxpayers have covered more than $50 billion in corn insurance premiums over the past 30 years, according to federal data compiled by the Environmental Working Group.
Researchers say proven conservation steps, such as planting rows of trees, shrubs and grasses in cornfields, can significantly reduce these emissions. But the Trump administration eliminated Many of the incentives that help farmers try such practices.
All of this raises a bigger question, experts say: If the U.S.’s most widely planted crop is worsening climate change, shouldn’t we be growing it differently?
How did Egypt take over the USA?
In the late 1990s, corn farmers in the United States were in trouble. Prices had plummeted amid a global grain glut and the Asian financial crisis. A 1999 report from the Federal Reserve Bank of Minneapolis stated that crop prices had “hit rock bottom.”
Corn production really took off in the 2000s after federal mandates and incentives helped convert much of the U.S. corn crop into ethanol.
In 2001, the U.S. Department of Agriculture launched the bioenergy program, which pays ethanol producers to increase the use of agricultural products as fuel. Later, the 2002 farm bill created programs to support ethanol and other renewable energy.
Corn growers soon launched an all-out campaign to persuade Congress to require gasoline to be blended with ethanol, arguing that it reduces greenhouse gases, reduces dependence on oil, and stimulates rural economies.
“I started getting calls from Capitol Hill saying, ‘Do you want your growers to stop calling us? We’re here for you,'” Jon Doggett, then the industry’s chief lobbyist, said in a speech. article Published by the National Corn Growers Association. “I’ve never seen anything like it before, and I haven’t seen anything like it since.”
In 2005, Congress created the RFS, which requires the addition of ethanol to gasoline, and expanded it two years later. The amount of corn used domestically for ethanol has more than tripled in the last 20 years.
Tim Searchinger, a researcher at Princeton University’s School of Public and International Affairs, said increased demand for corn as a result of the RFS has increased prices around the world. The result, Searchinger says, was more land cleared to grow corn. Global Carbon Project found that nitrogen oxide emissions from human activities increased by 40% from 1980 to 2020.
In the United States, “king corn” has become a political force. National corn and ethanol trade groups have spent more than $55 million on lobbying since 2010 and millions more on political donations to Democrats and Republicans, according to campaign finance records analyzed by Floodlight.
In 2024 alone, these trade groups spent twice as much on lobbying as the National Rifle Association. Now industries are pushing for the next big prize: expanding high-ethanol gasoline blends and positioning ethanol-based jet fuel as the “low-carbon” future of aviation.
Research debunks ethanol’s clean fuel claims
Corn and ethanol trade groups did not respond to interview requests. But they have long promoted corn ethanol as a climate-friendly fuel.
Quoted by the Renewable Fuels Association government and university research One study found that burning ethanol reduces greenhouse gas emissions by about 40% to 50% compared to gasoline. The ethanol industry says climate critics have it wrong, and that most of the corn used for fuel comes from better crops and smarter farming, not from plowing new land. The amount of fertilizer needed to produce a bushel of corn is said to have fallen sharply in recent years.
According to the Renewable Fuels Association, “Ethanol removes the carbon equivalent of 12 million cars from the roads each year by reducing carbon emissions.”
Growth Energy, a major ethanol trade group, said in a written statement to Floodlight that U.S. farmers and biofuel producers are “consistently finding new ways to make their operations more efficient and more environmentally beneficial” by using things like cover crops to reduce their carbon footprint. “Biofuel producers invest today “This will turn their products into net zero or even net negative over the next two decades,” he said.
Some studies tell a different story.
recently Environmental Working Group report It reveals that the way corn is grown in much of the Midwest—planting corn in the same fields year after year—carries a heavy climate cost.
And research Agricultural land use expert Tyler Lark and colleagues in 2022 linked the Renewable Fuel Standard to worsening water pollution and increased emissions, concluding that its climate impact is “no less than gasoline and is likely at least 24% higher.”
Lark’s research has been challenged by scientists from Argonne National Laboratory, Purdue University, and the University of Illinois; scientists issued a formal rebuttal arguing that the study was based on “questionable assumptions” and faulty modelling; this was an accusation Lark’s team denied.
A recent study found that solar panels can produce as much energy as corn ethanol on about 3% of the land.
“It’s just a terrible use of the land,” Searchinger, the Princeton researcher, said of ethanol. “And you can’t solve climate change if you’re going to use land in such a terrible way.”
nitrogen pollutionrural drinking water
Nitrogen used to grow corn and other crops is also a major source of drinking water pollution, experts say.
According to a New report from Clean Wisconsin and the Great Lakes AllianceMore than 90% of nitrate pollution in Wisconsin groundwater is linked to agricultural sources (mostly synthetic fertilizer and manure).
In 2022, Tyler Frye and his wife moved to a new home in the rural village of Casco, Wisconsin, about 20 miles (32 km) east of Green Bay. Tests revealed that the well water contained nitrate levels more than twice the EPA’s safe limit. “We were pretty shocked,” Frye said.
He installed a reverse osmosis system in his basement and still buys bottled water for his wife, who is breastfeeding their daughter, who was born in July.
When he watched manure, or manure, being spread on nearby fields, he said one question troubled him: “Where is this going?”
What might cleaner corn look like?
It is possible to reduce corn’s climate footprint, but farmers trying to do so are swimming against the policy tide.
Latest moves of the Trump administration We eliminated Biden-era incentives for climate-friendly agricultural practicesWhich agriculture minister Brooke Rollins dismissed as part of the “green new scam”.
But research shows that proven conservation practices, such as planting trees, shrubs and shrubs in cornfields, can make a measurable difference.
In northern Iowa, Wendy Johnson plants fruit and nut trees, organic grains, shrubs and other plants that need little or no nitrogen fertilizer on 130 of the 1,200 acres (485 hectares) of corn and soybeans she farms with her father. On the rest of the farm, they enrich the soil by rotational cropping and planting cover crops. They also converted less productive parts of the fields into “prairie strips,” strips of fescue that store carbon and do not require fertilizer.
They were hoping to receive $20,000 a year from the now-canceled Climate-Smart grant program, but that never happened.
“It’s hard to take risks on your own,” Johnson said. “That’s where federal support really helps.”
In southeast Iowa, sixth-generation farmer Levi Lyle blends organic and conventional methods on 290 acres of land. It uses a three-year rotation, extensive cover crops and a technique called roller crimping: flattening the rye each spring to create a mulch that suppresses weeds, nourishes the soil and reduces the need for fertilizer.
“Rolling cover crops is a huge opportunity to sequester more carbon, improve soil health, save on chemicals and still achieve similar yields,” Lyle said.
Despite growing research on corn’s climate costs, industry groups are pushing for legislation that would pave the way for ethanol-based jet fuel.
Producing enough ethanol-based aviation fuel could lead to another 114 million acres of land, researchers warn will be turned into cornor 20% more corn area than US crops for all purposes.
“The result will be to essentially glorify this dysfunctional system that we have created,” said Silvia Secchi, a University of Iowa professor and natural resources economist.
Projector is a nonprofit newsroom that investigates the forces holding back climate action
