Cows have become the butt of a lot of jokes. Or rather, their gas is joke-inducing as more people learn about the link between heat-trapping greenhouse gas emissions and cow burps and flatulence. In fact, livestock, especially cattle, are the largest human-induced sources of methane in the United States.

Researchers at the National Institute of Standards and Technology and Kansas State University unveiled a technology that more precisely measures cows’ gas emissions. This could lead to innovations that reduce greenhouse gas emissions on farms.

The technology

The researchers used a device called an agricomb, an optical frequency comb used in an agricultural setting. Optical frequency combs are precise tools that measure different light frequencies. 

The scientists used the portable agricomb to measure emissions of methane, ammonia, carbon dioxide, and water vapor based on light absorption in the atmosphere around a beef cattle feedlot in Kansas. The tool is especially good at measuring multiple gases at the same time, which is challenging for other technologies. This is the first time such a tool has been used in an agricultural setting.

The agricomb was able to identify trace amounts of gases, both from the cattle themselves and manure on the ground. The system is better able to characterize sources of gases compared with commercial sensors. And it is better at handling difficult-to-measure gases, such as ammonia. This shows promise for measuring emissions from cows that are widely dispersed in a pasture instead of clumped together in a pen.

Next steps

What cattle eat affects their emissions, but that is largely unaccounted for in greenhouse gas emission models. The cattle in the Kansas feedlot study ate a mixture of hay and corn silage. NIST and KSU’s next study will be on cows that eat native grasses in a pasture.

“The different feed, plus microbial activity in grassland soils that consumes methane, may mean less atmospheric methane production in the pasture than in the feedlot,” NIST physicist Brian Washburn said in a news release. “The cattle spend about 75% of their life in the pasture, so this measurement would be more representative of the net methane production. This would also be a harder measurement, since it would take place over a larger area.”

The researchers say the agricomb is accurately able to quantify agricultural gas emissions. They suggest that using an agricomb could help in designing cleaner and more productive farms.