A dump truck carries feed along a dirt road lines with snow
Jacob Weingardt delivers feed to cattle at Amana Society Farms feedlot in Amana, Iowa. Credit: Jim Slosiarek / The Gazette

At Amana Farms, in eastern Iowa, some 2,500 Angus cattle stand at a rail waiting for their breakfast. A truck drives slowly down the line, dumping a mix of hay, corn and distillers grains into the troughs.

Manure drops through the slatted floor into a pit that is scraped every hour, shifting manure to an anaerobic digester nearby. The digester, which acts like a 1.6 million-gallon bovine stomach, processes the manure and other food waste into methane, which is captured and turned into electricity.

Cattle stand near a feeding trough as a truck slowly approaches at Amana Society Farms feedlot in Amana, Iowa, on Wednesday, February 1, 2023. Credit: Jim Slosiarek, The Gazette

“We essentially can power all the homes in the colonies and all the small businesses,” said Amana Farms general manager John McGrath about the Amana Colonies, a set of small towns that are a popular tourist destination.  

Digesters are one solution to the big challenge of reducing greenhouse gas emissions from agriculture, which makes up more than 10% of the total greenhouse gas emissions in the United States as of 2020, the most recent year available. 

Agriculture is a major source of planet-warming greenhouse gases, and farming-intensive states like Iowa — with 13 million acres of corn and seven hogs per person — are outsized contributors, federal data show. Iowa ranks No. 2, behind Texas, for greenhouse gas emissions from agriculture. 

While nationwide emissions from sectors like energy production have fallen in recent decades, those from agriculture — especially livestock and corn — have grown.

Half the states in the country have no greenhouse gas reduction goals, which makes it hard to see how the United States is going to reach its economywide target of a 50% reduction below 2005 emissions levels by 2030.

“It’s purely a political decision, right?” said Steven Hall, an associate professor in the Department of Ecology, Evolution and Organismal Biology at Iowa State University. “If there’s no political will to advocate for such goals, it’s not going to happen absent market-based approaches or voluntary efforts.”

The Environmental Protection Agency has been tracking greenhouse gas emissions since 1990. Over that time, the energy and industrial sectors have slashed their combined emissions by nearly 35%, according to an analysis by The Gazette and Investigate Midwest of the EPA’s Greenhouse Gas Inventory Data Explorer.

The agriculture and transportation sectors each went up more than 6% between 1990 and 2020, but transportation is poised to plummet as more electric cars hit the roads. Modern agriculture, heavily dependent on fossil fuels and nitrogen fertilizer, doesn’t have a solution on the horizon.

A pump used to move animal waste through a series of chambers in an anaerobic digester is seen at Amana Society Farms feedlot in Amana, Iowa, on Wednesday, February 1, 2023. Animal waste from the society’s cattle operation is fed into its 1.6 million gallon anaerobic digester to produce methane which powers generators that turn it into electricity. Credit: Jim Slosiarek, The Gazette

Corn and more corn

U.S. corn growers have been planting more than 90 million acres a year since 2018, far more than the 60 million acres in the early 1980s, the U.S. Department of Agriculture reported. Nearly half of that corn nationwide is used to make ethanol. 

The top five greenhouse gas emitters from crop production, according to the EPA’s data since 1990, are, in order, Texas, Iowa, Kansas, Illinois and Nebraska. Producing ethanol also causes emissions, but that carbon dioxide is not counted under agricultural emissions data. Neither are greenhouse gases from fertilizer production.  

Corn requires nitrogen fertilizer to make amino acids, protein and chlorophyll. But too much fertilizer, or fertilizer applied at the wrong time, can cause nitrogen to run off into waterways or to be released into the air as a greenhouse gas.

Iowa farmers bought 5.27 million metric tons of fertilizer in crop year 2022, up 14% from 2021 and up 45% from 2020, according to state sales data. 

Last year was the first year since at least before 2014 that farmers applied more fertilizer in the fall than in the spring, University of Iowa research scientist Chris Jones tweeted in November. Because there’s no crop in the ground after harvest to absorb the nutrients, more go into the air and water.


Texas, California, Iowa, Nebraska and Kansas — the top five emitters for livestock, according to the EPA data from 1990 to 2020 — contribute more than one-third of the county’s emissions from cattle, swine and other livestock. 

Some producers are trying new technologies to reduce emissions from their animals, which produce methane through digestion. 

Anaerobic digesters are a costly option at $1 million to $5 million. Iowa passed a bill in 2021 that allows livestock farms to exceed maximum animal thresholds by building a digester to process manure, which caused a flurry of new permits at Iowa dairies.

Another approach is breeding cows that eat less while still producing the same amount of beef, McGrath said. Or including seaweed in cattle feed to reduce methane. 

Lack of progress

Comparing states’ greenhouse gas emissions from agriculture can be like comparing apples to oranges. Or rice to strawberries. Or corn to peanuts. That’s because soil type, climate and crops can influence emissions, but the multipliers used for the calculations are standardized.

“The emission factor for Texas or California is likely to be very different from the emission factor for Iowa, yet the way the emission factor is done doesn’t really take into account the differences,” Hall said.

Looking at a state’s agricultural emissions over time is a good way to see whether there have been changes, Hall said. Among Midwestern states, the trend lines bounce up and down, not showing dramatic improvement.

In many states, there are no plans to scale back. 

Iowa’s annual inventory of greenhouse gas emissions, which uses the trend of inventory numbers back to 1990 to project future emissions, shows emissions from the agricultural sector would increase 83% by 2040 if the state stays on the same trajectory as the past 30 years. 

Iowa has no greenhouse gas reduction goals, for agriculture or any other sector, the Iowa Department of Natural Resources confirmed. Iowa Agriculture Secretary Mike Naig, when asked whether he would support Iowa setting emission targets, said his agency doesn’t have that authority. 

“We must always balance the need to keep Iowa’s agriculture productive while also protecting our valuable shared natural resources,” he said in an email.

Setting goals

Climate change already is disturbing Midwest states with more dangerous storms, loss of animal species and risks of crop loss because of flood or drought. On a global scale, leaders are trying to keep the temperature rise from going above 1.5 degrees Celsius (or 2.7 degrees Fahrenheit) to avoid some of the worst calamities, including inundation of coastal areas and scarcity of food. 

A goal for greenhouse gas emissions is like a road map, guiding decisions along the way, said Jerald Schnoor, engineering professor and co-director at the University of Iowa’s Center for Global & Regional Environmental Research.

Of the 25 states with greenhouse gas reduction targets, 21 have Democratic governors. 

“California is the most progressive state when it comes to tackling greenhouse gas emissions,” said Frank Mitloehner, a professor and air quality specialist at the University of California at Davis. “The state has pursued reductions in a smart way, by incentivizing farmers to reduce their emissions.”

California, led by Democratic Gov. Gavin Newsom, passed regulations to reduce methane emissions from livestock and dairy by 40% below 2013 levels by 2030. The industry has made progress toward that goal, in part by using anaerobic digesters, Mitloehner said.

Illinois is among states that have committed to reducing greenhouse gas emissions by at least 26% below 2005 levels by 2025. The state passed the Climate and Equitable Jobs Act in 2021, but that legislation focuses on the energy and transportation sectors. 

Why not agriculture? 

“In some cases, the infrastructure isn’t quite in place to be able to do it,” said Don Wuebbles, an emeritus professor in the School of Earth, Society and Environment at the University of Illinois. For example, farm machinery still runs on fossil fuels, he said. 

“Part of it is reluctance on the farmer’s part and part of it is reluctance on the entire planet’s part to make things move fast enough to do what we need to be doing.”

Charles Stanier, a University of Iowa engineering professor who served on the Iowa Carbon Sequestration Task Force in 2021, said the bulk of the energy subgroup’s conversations were about CO2 pipelines and requiring public construction projects to use CO2-infused concrete. Both practices together would sequester only a tiny sliver of greenhouse gases, he said. 

Stanier suggested Gov. Kim Reynolds or the Iowa Legislature set a target for emission reductions, but task force members weren’t interested, he said. 

Iowa’s “direction is to monetize the agricultural reductions we can achieve either by having the consumer pay into the agricultural sector for the reductions, or to have the federal government pay,” Stanier said.

Incentives for change

The Inflation Reduction Act, which President Joe Biden signed into law in August, provides $19.5 billion for agricultural conservation, including $8.45 billion more for the Environmental Quality Incentives Program, which helps farmers pay for conservation practices such as growing cover crops during the winter or reduced tilling. Keeping roots in the soil stores more carbon dioxide.

Cover crops grow on about 4% of agricultural acres in the United States, according to data from the USDA’s 2017 agricultural census. More federal cost-share money could mean more farmers trying cover crops, conservation experts said. 

Companies — some to appease customers or boards — also are making investments in sustainable agriculture.

Cargill, which processes meat, eggs and grains for food companies, is offering contracts of up to $25 per acre to corn, soy or wheat farmers in 15 Midwest states to sequester carbon dioxide through regenerative practices, including no till, reduced tillage or cover crops.

Amana Farms earlier this year enrolled 3,300 acres in the program, McGrath said. The Cargill contract will help Amana buy a strip-till machine, which costs about $350,000. 

Since 2013, when Amana Farms stopped tilling 30% of its acres, McGrath has seen a half percent increase in organic material in the soil. So even if curbing greenhouse gases ranks lower on the priority list after improving soil health and water quality, McGrath said, it’s “coming along for the ride.” 

This story is a product of the Mississippi River Basin Ag & Water Desk, an editorially independent reporting network based at the University of Missouri School of Journalism in partnership with Report For America and the Society of Environmental Journalists, funded by the Walton Family Foundation.