2017 News & Events

A team of scientists from CSD and the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder published a paper in Atmospheric Chemistry and Physics that characterizes the emissions from animal feedlots.

Scientists have long known that animal feedlots emit volatile organic compounds (VOCs) into the atmosphere. This is problematic because VOCs can react to form ozone and fine particles, affecting air quality and human health. Furthermore, these VOCs are responsible for the unpleasant odor from animal feedlots.

However, it wasn't well-understood how different activities within the feedlots contribute to VOC emissions – for example, to what extent emissions come from the animals and their waste, or from the storage and use of the feed. CSD scientists also looked to characterize the chemical composition of those VOCs specific to animal feedlots, which included a broad category of chemicals such as alcohols, carboxylic acids, and sulfur compounds.

To better understand the sources and chemical compositions of the VOC emissions, CSD scientists made measurements from both their mobile laboratory and the NOAA WP-3D research aircraft. A new instrument on the aircraft and mobile laboratory allowed the scientists to get fast, high-resolution measurements of many different VOC chemicals as they sampled downwind from the feedlots.

The researchers looked at different kind of facilities and examined the chemical signatures of the VOCs and ammonia they emitted. The results show that VOC emissions mainly come from two sources: animals and their waste or feed storage and handling. However, the composition of what each source emits is different. For example, animals and their waste emit phenols and nitrogen-containing compounds such as ammonia, while the feed emits alcohols, carboxylic acids, and sulfur-containing compounds.

The researchers found that the same animals (cows) give off different VOCs depending on their diet and other practices. For example, across the Front Range, beef cattle had higher levels of emissions than dairy cattle. Also, there are sometimes complaints of unpleasant smells near large animal feedlots. The researchers found that sulfur-based compounds were the primary source of feedlot odor for all types of animal feedlots, and these sulfur compounds are largely emitted by animal waste.

Industry practices (e.g. feed additives) affect odor and atmospheric chemistry in and around feedlots. These results suggest that a better understanding of these processes – the sources and chemical composition of VOCs – could help industry target specific compounds and mitigate the impacts of emissions on air quality and human health, without affecting the productivity of the industry.