Midwestern ranching operations linked to rising ammonia pollution
The agricultural industry is one of the biggest emitters of ammonia, methane and nitrous oxide. While animal agriculture in the United States has grown steadily for decades, livestock operations are also becoming denser. From 2002 to 2016, the number of concentrated animal feed operations (CAFOs) increased by almost 20% compared to only a 6% increase in the number of farm animals.
For the first time, researchers were able to link this increase in CAFOs to a dramatic increase in ammonia emissions. The results, which will be presented on Dec. 14 at the AGU’s fall 2021 meeting, raise health and environmental justice concerns about the pollutant’s effects, the researchers said.
The team collected animal density records from the United States Department of Agriculture (USDA) and the EPA, which showed where CAFOs have operated at the county level since 2002. Researchers focused on CAFO density medium to large (i.e. those with more than 300 cattle, more than 200 dairy cows or more than 750 pigs). Using satellite detection of ammonia collected by NASA’s Atmospheric Infrared Sonar (AIRS) aboard the Aqua satellite and comparing it with animal density data, the researchers determined that there was a significant relationship between the increase in CAFOs in the Midwest and the increase in ammonia in the same period.
“We know that ammonia comes from animal husbandry, but in fact, establishing a statistical link between ammonia concentrations and these point sources is not something that we have really been able to achieve before,” said Alyssa Burns. , doctoral student. student at the University of California, Irvine (UCI) and lead author of the study.
A call for regulation
The research team said their discovery is grounds for the EPA to consider regulating air pollution from CAFOs under the Clean Air Act. “I think there is an air quality regulatory framework that would allow the EPA to start working on [ammonia regulations] today, ”said Ann Marie Carlton, UCI chemistry professor and co-author of the study.
The ability to link atmospheric concentrations of ammonia to specific sources is particularly valuable, said Daven Henze, professor of mechanical engineering at the University of Colorado Boulder who was not involved in the research. Henze believed the new research could help scientists understand how the size and density of animal farms create different effects on air pollution.
Once released from animal wastes into the air, ammonia reacts quite easily with other air pollutants, such as greenhouse gases emitted by cars and power plants. This reaction forms particles in the air which are harmful to human health and cause premature death. “They have really profound health effects,” Burns said.
CAFOs stand out
CAFOs, in particular, Carlton said, can be a significant contributor to ammonia emissions because CAFOs treat animal waste differently from low-density animal operations. “If you have a relatively small farm with happy little cows, they can walk around in the poo and you can apply it to the soil in a sustainable way,” she said. “But when they’re confined, you’re more dependent on slurry and silage, and all of those things have more air emissions.”
If the EPA were to regulate CAFO emissions, it would be relatively easy for CAFOs to comply, Carlton said. Henze agreed. “The [are] some fairly affordable practices that can be implemented [to CAFOs] to significantly reduce ammonia emissions, ”he said.
Because CAFOs in the United States are often located in low-income counties and employ a disproportionate number of people of color, eliminating air pollution is a matter of environmental justice, Carlton said. Advances in detection technology reveal more of these disparities. “It’s getting harder and harder for pollution to hide,” she said.
—Grace van Deelen (@GVD__), science writer