Scientists aim to reduce emissions from cows — by changing their diet
A high-tech laser measured gases produced by cattle on a Kansas feedlot - the results may help mitigate future cattle emissions
On feedlots across the U.S., cows produce methane, a greenhouse gas 28 times more potent than carbon dioxide at trapping heat in the atmosphere. They also produce ammonia, a gas that reacts with acids in the atmosphere to create aerosols, like PM2.5, a pollutant dangerous to human health.
In an effort to find novel ways to mitigate harmful gases escaping into the atmosphere, scientists wondered — could changing cattle’s diet reduce the gases they leave behind?
To test the idea, a team of CU Boulder, the National Institute of Standards and Technology (NIST), and Kansas State University researchers used high-tech lasers on a Kansas feedlot to measure gases produced by cows.
“We wanted to test if changing what we feed the cattle could potentially reduce how much methane or ammonia they create,” said Nathan Sweet, a chemistry PhD student in CIRES Fellow Joost de Gouw’s lab, who tracked ammonia emissions in the study. “If one feed results in less ammonia emissions than the other, that could be important for local air quality.”
Most cattle in the U.S. are finished on corn, but studies have found sorghum is more sustainable as it requires less water and fertilizer, and is resilient to heat. Sweet and the team set up the experiment at Kansas State University Southeast Research-Extension Center, where they separated the cows into two groups and fed them separate diets of corn and sorghum.
The team installed a laser, a Dual Comb Spectroscopy instrument, along the fenceline to measure methane and ammonia emissions 24 hours a day for eight months — measuring gases on each end of the feedlot to collect data from several wind directions. Every 15 minutes, the instrument switched between measuring different pens gathering data on gases produced by cows eating different grains.
The Dual Comb Spectroscopy instrument is placed along the fenceline on the Kansas feedlot to monitor emissions. Nathan Sweet/CIRES
Sweet and his team are finalizing data and analyzing results. Preliminary findings from over a week of data reveal small differences in ammonia emissions between the corn and sorghum lots. The team has yet to conclude if the differences are statistically significant and if any differences vary through time.
Looking ahead, Sweet will expand his research in Colorado, measuring ammonia at feedlots near Fort Collins, in order to further researchers’ understanding of Colorado’s front range air quality as it relates to agriculture.
“In places like Colorado and Kansas, ammonia from cattle is a major source of toxic air pollution,” Sweet said. “While we’re still analyzing the data, we know that if we find a change in ammonia from switching to sorghum, and if that switch were to be implemented on a large enough scale, that could be really important for improving local air quality.”
To learn more about Nathan Sweet’s work click here to read about his AGU24 poster.
