|Todd, Richard - Rick|
|COLE, NOEL - Retired ARS Employee|
|Rotz, Clarence - Al|
|CASEY, KENNETH - Texas A&M Agrilife|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2016
Publication Date: 8/16/2016
Citation: Waldrip, H., Todd, R.W., Parker, D.B., Cole, N.A., Rotz, C.A., Casey, K. 2016. Nitrous oxide emissions from open-lot cattle feedyards: A review. Journal of Environmental Quality. doi:10-2134/JEQ2016.04.0140.
Interpretive Summary: The manure from beef cattle feedyards and open-lot dairies is a source of nitrous oxide, which is potent greenhouse gas that is involved in global climate change. Currently, the quantity of nitrous oxide produced in cattle systems in not well understood. Quantitative values are needed to estimate the effects of nitrous oxide emissions on the environment. In addition, standard methods for measuring manure-derived nitrous oxide have not been developed. Thus, measured values on feedyards and dairies are highly variable, leading to high levels of uncertainty. Methods to reduce feedyard nitrous oxide have not been well developed or evaluated. This paper, authored by scientists from ARS(Bushland, TX.) and Texas A&M AgriLife Research, reviews what we currently know, and what we don't know, about feedyard nitrous oxide. Differences in measurement techniques are discussed. In addition, potential methods to reduce the magnitude of feedyard nitrous oxide emissions are proposed. In short, much work is required to understand variability of feedyard nitrous oxide formation and emission from beef cattle feedyards and open lpt dairies.
Technical Abstract: Nitrous oxide volatilization from concentrated animal feeding operations (CAFO), including cattle feedyards, has become an important research topic. However, there are limitations to current measurement techniques, uncertainty in the magnitude of feedyard nitrous oxide fluxes and a lack of effective mitigation methods. The objective of this review was to assess nitrous oxide emissions from cattle feedyards, including comparison of measured and modeled emission rates, discussion of measurement methods and evaluation of mitigation options. Published annual per capita flux rates for beef cattle feedyards and open lot dairies were highly variable and ranged from 0.002 to 4.3 kg nitrous oxide per animal per year. On an area basis, published emission rates ranged from 0 to 41 mg nitrous oxide per square meter per hour. From these studies and IPCC emission factors (EF), calculated daily per capita nitrous oxide fluxes averaged 18 g nitrous oxide per animal per day (range of 0.04 to 67 g nitous oxide per animal per day). This variation was due to inconsistency in measurement techniques as well as irregularity in nitrous oxide production and volatilization attributable to management, animal diet and environmental conditions. Based on this review, it is clear that the magnitude and dynamics of nitrous oxide emissions from open-lot cattle systems are not well understood. Further research is required to quantify feedyard nitrous oxide fluxes and develop cost effective mitigation methods.