Shining a Light On Cow Burps
How physicists joined forces with agronomists and animal scientists to measure methane emissions using lasers and improve efficiency measures for cattle producers
By Kirsten Conard
Photo by Dan Donnert
Cows and lasers? It’s not quite what readers may be picturing.
K-State researchers across the departments of agronomy, animal sciences and industry, and physics have partnered with the National Institute of Standards and Technology to develop a laser system that measures greenhouse gas emissions at a herd or farm scale rather than on a single-animal basis.
The impact? The researchers believe that this new technology will improve the accuracy of greenhouse gas inventories and identify new management practices that improve energy and nutrient use efficiency, which the K-State team thinks will potentially lead to better economic outcomes and decreased greenhouse gas emissions.
Why measure methane emissions
Methane is not only a greenhouse gas, but also a key metric for evaluating feed and production efficiency for cattle. Logan Thompson, assistant professor in sustainable livestock feeding at K-State, is excited to see this project grow, as the scientific community previously lacked the ability to measure greenhouse gas emissions at herd level.
“(Methane) is a pretty potent energy-trapping gas in the atmosphere,” Thompson said. “If we reduce the amount of methane emitted, we are going to reduce our industry’s carbon footprint."
The research also has a direct impact on ranchers.
“Methane is a loss of energy,” Thompson said. “Cattle consume primarily grass… they lose some of that consumed energy in the form of methane. So, if we can conserve more of that energy... we can improve the performance and efficiency of that animal.”
Thompson said that the more fiber included in the cattle’s diet, the more methane they produce. Cattle are ruminants, meaning they rely on microbes to break down plant fibers. When cows expel methane, they lose energy that could have been absorbed and used to support growth, muscle development, reproduction, and lactation.
High fiber diets like grass increase fermentation time, therefore producing more methane and losing energy that the cow could have used. Therefore, the more methane a cow emits, the less feed-efficient the animal is. Improving a cattle herd’s efficiency improves profitability through lowered feed costs and higher productivity in the animal.
Shining a literal light on cow burps
Brian Washburn, NIST physicist and project leader and adjunct professor in the Department of Physics, and Eduardo Santos, associate professor in the Department of Agronomy, initiated and led this study.
The team built a frequency comb spectroscopy, called an “agrocomb,” which is a high-resolution infrared laser with equally spaced frequencies that uses light to measure the presence of certain molecules in the atmosphere. The laser is pointed at the height of the animal’s head, towards a mirror 100-400 meters away. The mirror reflects the light back to a sensor, which turns the light into electrical signals containing information about the gases present.
“The gas absorbs specific colors of a laser,” Washburn said, “and we know those colors from doing lab measurements. So, if we send the laser out, it gets absorbed a little bit by the gas, letting us know it is (present).”
This technology is not exclusive to methane; it also measures water vapor, carbon dioxide, ammonia and other greenhouse gases.
Washburn said the laser method does not affect the cattle’s normal grazing habits.
“This isn’t a Death Star laser,” he said. “It does not damage your eye even if you look into (it).”
Two lasers are used in this process. One laser is placed upwind of the herd to get an initial measurement of gases already present in the atmosphere. The second is placed downwind to measure the emissions produced by the cattle between the lasers.
In Kansas, this research is being done at K-State's Rannell’s Ranch and the beef stocker unit.
"We picked Rannell’s Ranch because of its topography, which enables a very long line of sight, along with access to AC power,” Santos said. “We are working to improve the power consumption through solar power, which will expand the opportunities for on-farm research in remote locations.”
Along with being at K-State, the technology has also been set up in Colorado and southwest Kansas.
The connection between sorghum and cattle
Sorghum is a common feed for cattle in feedlots and reliably grows in water-limited regions. Sarah Sexton-Bowser, director for K-State's Center for Sorghum Improvement is a stakeholder in this technology for her research to improve sorghum feed value. She said the state of Kansas grows more than 50% of the sorghum crop for the United States.
“Sorghum has more than 40,000 unique genotypes,” Sexton-Bowser said. “There is a treasure trove that we mined for improved agronomic production, traits that support the farmers when they grow the crop, but we have yet to exploit those traits… to support efficiency for the animal system.”
She adds: “Methane is a great tool to measure efficiency in cattle, helping us to elevate an already great agricultural system in Kansas.”
The power of collaboration
Interdisciplinary research provides an opportunity for experts across different fields to come together on a difficult problem and use their unique knowledge to create a solution. According to Washburn, it is also beneficial for the students on the project.
One such student is Lindsay Morris, who worked as a graduate research assistant and a postdoctoral researcher on this project while pursuing her doctoral degree in physics at K-State. She now works as a soil health specialist for northeast Kansas in the Kansas Association of Conservation Districts.
Morris worked alongside physics and agronomy students from K-State and University of Colorado graduate researchers for NIST.
“It was a very cool experience. Very non-traditional,” she said. “It makes my ability to look at things from a different perspective a little bit easier. A big part of interdisciplinary work is speaking different scientific languages.”
Looking toward the future
Washburn said this research and technology generate new opportunities for future research in livestock genetics, feed additives, crop research and other livestock management practices. He said researchers hope to one day do farm-scale measurements to inform ranchers of their herds’ methane output so they can make decisions on the management of that herd.
It can also be used by companies selling products that claim to reduce methane output as a proof point.
“This is the kind of project that would put more control in the producer’s hands,” Morris said.
Thompson said that in managing grazing, ranchers can try to time plants for grazing when they are highest in protein and lowest in fiber, as well as determining which supplements to provide to balance the cattle’s rumen ecosystem. In a feedlot, the diet provided to cattle can make an impact on their energy efficiency.
The technology can also be used for future research. The ability to measure multiple gases allows the agrocombs to be used to address issues related to crop water use, soil nutrient management, and monitoring greenhouse emissions at farm scale.
“The team is pushing the boundaries of what we are able to do and measure,” Sexton-Bowser said, adding that the study of methane creates a win-win scenario, “with methane being an important measure for environmental resiliency, today and tomorrow.”
“Physics should be for helping people,” Washburn said, noting that K-State is illuminating a path toward a more sustainable and informed future in agriculture.