Ammonia emissions from beef cattle feedyards: A review

Authors: LEE, MYEONGSEONG - Texas A&M University; AUVERMANN, BRENT - Texas A&M University; TEDESCHI, LUIS - Texas A&M University; Koziel, Jacek; BRANDANI, CAROLINA - Texas A&M University; GOUVEA, VINICIUS - Texas A&M University; SMITH, JASON - Texas A&M University; CASEY, KENNETH - Texas A&M University

Submitted to: Frontiers in Animal Science
Publication Type: Review Article
Publication Acceptance Date: 6/3/2025
Publication Date: 7/2/2025
Citation: Lee, M., Auvermann, B.W., Tedeschi, L.O., Koziel, J.A., Brandani, C.B., Gouvea, V.N., Smith, J.K., Casey, K.D. 2025. Ammonia emissions from beef cattle feedyards: A review. Frontiers in Animal Science. 6. Article 1608387. https://doi.org/10.3389/fanim.2025.1608387.
DOI: https://doi.org/10.3389/fanim.2025.1608387

Interpretive Summary: Over the past few decades, livestock and poultry farmers have scaled up farming operations to meet society’s demand for high-quality meats, milk, eggs, and by-products. This has generated profits and jobs, while the environmental problems associated with air quality have been exacerbated. These unwanted side-effects of confined animal feeding operations (CAFOs) are caused by gas emissions from manure. Mitigating NH3 emissions from beef cattle feedyards is critical to achieve an environmental and sustainable production of animals benefiting the producers and society in general. Researchers from ARS (Bushland) and Texas A&M University reviewed the literature focused on ammonia (NH3) emissions from beef cattle feedlots. The review reports the state-of-the art NH3 emission factors and fluxes that can be used for improved assessment of emissions and benchmarking of mitigation strategies. The precision diet feeding to meet, but not exceed, metabolic crude protein requirements was identified as the most practical way to mitigate NH3 emissions.

Technical Abstract: This review described the state of the science concerning the generation, measurement, and mitigation of ammonia (NH3) emissions from beef cattle feedyards. NH3 emissions primarily come from urinary urea in cattle manure. In the past, constant emission factors were used to inventory NH3 emissions. Currently, NH3 emission factors estimated by process-based mechanistic models reflecting various factors affecting NH3 emissions in the feedyard environment are available. This review of current literature indicated the average NH3 emissions from a beef cattle feedyard was approximately 119 g/head/day (range 24 to 318 g/head/day), and the average NH3 flux was approximately 58 µg/m2/s (range 2 to 185 µg/m2/s). Although more realistic estimates of NH3 emission flux from open-lot livestock facilities were being obtained using process-based models, there was still significant variation depending on the diet composition, manure management practices, and the feedyard environment, including both seasonal weather patterns and synoptic weather events. We note the need to improve inventories of NH3 emissions into categories of crude protein percentage, manure management implemented, and feedyard environment. Some mitigation strategies can be effective, such as diet manipulation, growth-promoting technologies, and manure or pen-surface amendments. Of those, precision diet feeding to meet but not exceed protein requirements appeared to be the most practical way to reduce ammonia emissions over the animals’ feeding period; laboratory studies suggested that shorter-term reductions in emission flux may be possible with the other approaches, but they were far more speculative at this point as to both their efficacy and their cost of implementation.