For decades, corn has reigned over American agriculture. It sprawls across 90m acres – about the size of Montana – and goes into everything from livestock feed and processed foods to the ethanol blended into most of the nation’s gasoline.
But a growing body of research reveals that the US’s obsession with corn has a steep price: the fertilizer used to grow it is warming the planet and contaminating water.
Corn is essential to the rural economy and to the world’s food supply, and researchers say the problem isn’t the corn itself. It’s how we grow it.
Research undercuts ethanol’s clean-fuel claims
Corn and ethanol trade groups did not respond to requests for interviews. But they have long promoted corn ethanol as a climate-friendly fuel.
The Renewable Fuels Association cites government and university researchthat finds burning ethanol reduces greenhouse gas emissions by roughly 40%-50% compared with gasoline. The ethanol industry says the climate critics have it wrong – and that most of the corn used for fuel comes from better yields and smarter farming, not from plowing up new land. The amount of fertilizer required to produce a bushel of corn has dropped sharply in recent decades, they say.
“Ethanol reduces carbon emissions, removing the carbon equivalent of 12 million cars from the road each year,” according to the Renewable Fuels Association.
Growth Energy, a major ethanol trade group, said in a written statement to Floodlight that US farmers and biofuel producers are “constantly finding new ways to make their operations more efficient and more environmentally beneficial”, using things like cover crops to reduce their carbon footprint. “Biofuel producers are making investments today that will make their products net-zero or even net negative in the next two decades,” the statement said.
Some research tells a different story.
A recent Environmental Working Group report finds that the way corn is grown in much of the midwest – with the same fields planted in corn year after year – carries a heavy climate cost.
And research in 2022 by agricultural land use expert Tyler Lark and colleagues links the Renewable Fuel Standard to worsening water pollution and increased emissions, concluding the climate impact is “no less than gasoline and likely at least 24% higher”.
Lark’s research has been disputed by scientists at the Argonne National Laboratory, Purdue University and the University of Illinois, who published a formal rebuttal arguing the study relied on “questionable assumptions” and faulty modeling – a charge Lark’s team has rejected.
One recent study found that solar panels can generate as much energy as corn ethanol on roughly 3% of the land.
“It’s just a terrible use of land,” Searchinger, the Princeton researcher, said of ethanol. “And you can’t solve climate change if you’re going to make such terrible use of land.”
Nitrogen polluting rural drinking water
The nitrogen used to grow corn and other crops is also a key source of drinking water pollution, experts say.
According to a new report by Clean Wisconsin and the Alliance for the Great Lakes, more than 90% of nitrate contamination in Wisconsin’s groundwater is linked to agricultural sources – mostly synthetic fertilizer and manure.
In 2022, Tyler Frye and his wife moved into a new home in the rural village of Casco, Wisconsin, about 20 miles (32km) east of Green Bay. Testing found their well water had nitrate levels more than twice the EPA’s safe limit. “We were pretty shocked,” Frye said.
He installed a reverse-osmosis system in the basement and still buys bottled water for his wife, who is breastfeeding their daughter, born in July.
When he watches manure or fertilizer being spread on nearby fields, he said, one question nags him: “Where does that go?”
What cleaner corn could look like
Reducing corn’s climate footprint is possible – but the farmers trying to do it are swimming against the policy tide.
In northern Iowa, Wendy Johnson is planting 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. Across the rest of the farm, they enrich the soil by rotating crops and planting cover crops. They have also converted less productive parts of the fields into “prairie strips” – bands of prairie grass that store carbon and require no fertilizer.
They were counting on $20,000 a year from the now-cancelled Climate-Smart grant program, but it never came.
“It’s hard to take risks on your own,” Johnson said. “That’s where federal support really helps.”
In south-east Iowa, sixth-generation farmer Levi Lyle mixes organic and conventional methods across 290 acres. He uses a three-year rotation, extensive cover crops and a technique called roller crimping: flattening rye each spring to create a mulch that suppresses weeds, feeds the soil and reduces fertilizer needs.
“The roller crimping of cover crops is a huge, huge opportunity to sequester more carbon, improve soil health, save money on chemicals and still get a similar yield,” Lyle said.
Despite mounting research about corn’s climate costs, industry groups are pushing for legislation to pave the way for ethanol-based jet fuel.
Researchers warn that producing enough ethanol-based aviation fuel could prompt another 114m acres to be converted to corn, or 20% more corn acres than the US plants for all purposes.
“The result,” said University of Iowa professor and natural resources economist Silvia Secchi, “would be essentially to enshrine this dysfunctional system that we created.”
Read through the full article by Ames Alexander / The Guardian
