NIST’s “Agricomb” … measures multiple gas emissions from cattle


N. Hanasek / NIST

After the debut of optical frequency comb Light ruler, Spin-off continued. Astrocom Measuring starlight and radar-like comb systems Detect natural gas leaks.. And now, researchers have announced “Agricom” for measuring belching in cattle.

Agricom can help optimize agricultural processes and reduce the production of greenhouse gases that trap heat.

Researchers at the National Institute of Standards and Technology (NIST) and Kansas State University (KSU) use NIST’s Agricom to emit methane, ammonia, carbon dioxide, and water vapor from the atmosphere around a beef feedlot in Kansas. The amount was measured at the same time. The NIST device (2-comb system) identifies trace gases based on the exact shade and amount of infrared radiation absorbed by the atmosphere as the comb light traverses outdoor paths.

Listed in the journal Science Advances, The demonstration was the first use of frequencycom in an agricultural environment. The portable system was installed in a trailer parked next to the feedlot. The laser light has been specially amplified and filtered to target a particular gas.

Researchers measured gas along two 100-meter paths upwind and leeward from an enclosure with about 300 cows. Emissions from livestock, primarily cattle, are the largest source of anthropogenic methane, the main greenhouse gas in the United States, and ammonia is an important air pollutant, so the experiment focused on methane and ammonia. I did.

In the measurements, we obtained emissions from both the digestive process of cattle and manure on the ground. Agricom measured both methane and ammonia concentrations at one-millionth levels with one-2.5 billionth accuracy. The results of methane agricom were comparable to those of commercial sensors that sampled air at multiple inlets along the edges of the feedlot. Comb systems were especially useful for ammonia because this gas is sticky and difficult to measure with systems that draw in air. In addition, Agricom can measure many gases at the same time, which was difficult with conventional systems.

Finally, while off-the-shelf sensors measured accurate background levels faster, according to the paper, Agricom was able to more accurately capture the leeward plume and better characterize the gas source. Improving accuracy is important for planned future measurements of methane from sparsely distributed cattle in the pasture, which is a much more difficult problem.

The match between old and new technologies stimulates the belief that Agricom can be used to accurately quantify gas in the agricultural context, the paper suggests. Advantages of Agricom include sensitivity to a wide range of infrared light, high accuracy, calibration-free detection of multiple gases at once, and flexibility in measurement setup. Combining two combs with different “tooth” spacing to identify the exact color of the light will make the analysis more accurate.

Estimating methane emissions from livestock is difficult due to variations in commercial farm management practices and cattle characteristics. In addition, what cattle eat affects emissions, which is not explained in the national inventory, creating great uncertainty in greenhouse gas emission models. Cows at the Kansas Feedlot ate a mixture of hay and corn silage.

“In the future, we plan to work with KSU to measure pastures where cattle eat native grass,” said NIST physicist Brian Washburn. “In addition to different feeds, microbial activity in grassland soils that consume methane can mean less atmospheric methane production in pastures than in feedlots. Cows account for about 75% of their lives. This measurement better represents the net methane production because we are spending time in the pasture, because it is done in a wider area, about 500m x 500m, less animals, about 40 animals. , It will be a more difficult measurement. “

Researchers support precision agriculture (using new technology to increase yields) and design cleaner, more productive farms by allowing Agricom to measure more gas at the same time on a large spatial scale. It suggests that you can do it.

This work was partially funded by the National Science Foundation, the ARPA-E MONITOR Program, the William and Joan Porter Foundation, and the Haviger Heritage Foundation.

Papers: DI Herman, C. Weerasekara, LC Hutcherson, FR Giorgetta, KC Cossel, EM Waxman, GM Colacion, NR Newbury, SM Welch, BD DePaola, I. Coddington, EA Santos, BR Washburn. Accurate multiple agricultural gas fluxes determined using wideband open path dual comb spectroscopy. Science Advances.. Published online on March 31, 2021. DOI: 10.1126 / sciadv.abe9765 NIST’s “Agricomb” … measures multiple gas emissions from cattle

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