Applicability of Eddy Covariance to Estimate Methane Emissions from Grazing Cattle

Coates, Trevor; Benvenutti, Marcelo A.; Flesch, Thomas K.; Charmley, E.; McGinn, S. M.; Chen, Deli

doi:10.2134/jeq2017.02.0084

Cited by 13 publications

(6 citation statements)

References 34 publications

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“…Supplemental hay was made available to the bison approximately 50 m west of the tower, and increases in the frequency of bison appearance there are associated with the animals' preferred feeding times after dawn and before dusk, but observed methane flux did not vary as a function of time of day (e.g., Dengel et al, 2011) as noted above. Regardless, ruminant methane flux measurements are simpler to make when animals congregate (Coates et al, 2017;Tallec et al, 2012) as was often observed in our study (e.g.,Figs. 2,9 and 10).…”

Section: Bison Spatial Distribution and Measurement Uncertaintymentioning

confidence: 52%

Methane efflux from an American bison herd

et al. 2021

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Abstract. American bison (Bison bison L.) have recovered from the brink of extinction over the past century. Bison reintroduction creates multiple environmental benefits, but impacts on greenhouse gas emissions are poorly understood. Bison are thought to have produced some 2 Tg yr−1 of the estimated 9–15 Tg yr−1 of pre-industrial enteric methane emissions, but few measurements have been made due to their mobile grazing habits and safety issues associated with measuring non-domesticated animals. Here, we measure methane and carbon dioxide fluxes from a bison herd on an enclosed pasture during daytime periods in winter using eddy covariance. Methane emissions from the study area were negligible in the absence of bison (mean ± standard deviation = −0.0009 ± 0.008 µmol m−2 s−1) and were significantly greater than zero, 0.048 ± 0.082 µmol m−2 s−1, with a positively skewed distribution, when bison were present. We coupled bison location estimates from automated camera images with two independent flux footprint models to calculate a mean per-animal methane efflux of 58.5 µmol s−1 per bison, similar to eddy covariance measurements of methane efflux from a cattle feedlot during winter. When we sum the observations over time with conservative uncertainty estimates we arrive at 81 g CH4 per bison d−1 with 95 % confidence intervals between 54 and 109 g CH4 per bison d−1. Uncertainty was dominated by bison location estimates (46 % of the total uncertainty), then the flux footprint model (33 %) and the eddy covariance measurements (21 %), suggesting that making higher-resolution animal location estimates is a logical starting point for decreasing total uncertainty. Annual measurements are ultimately necessary to determine the full greenhouse gas burden of bison grazing systems. Our observations highlight the need to compare greenhouse gas emissions from different ruminant grazing systems and demonstrate the potential for using eddy covariance to measure methane efflux from non-domesticated animals.

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Section: Bison Spatial Distribution and Measurement Uncertaintymentioning

confidence: 52%

Methane efflux from an American bison herd

et al. 2021

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“…when animals congregate (Coates et al, 2017;Tallec et al, 2012) and ruminant behavior is critical to track to estimate fieldscale efflux (de la Motte et al, 2019). Aggregation behavior in our study bison herd was often upwind of the eddy covariance tower (Figures 6 & 11) and resulted in more overlap between flux footprint and bison location than would have occurred if bison locations were randomly distributed throughout the study area, emphasizing the importance of tower placement in studies of grazing systems.…”

Section: Bison Spatial Distributionmentioning

confidence: 80%

Methane efflux from an American bison herd

Stoy¹,

Cook²,

Dore³

et al. 2020

Preprint

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Abstract. American bison (Bison bison L.) have recovered from the brink of extinction over the past century. Bison reintroduction creates multiple environmental benefits, but their impacts on greenhouse gas emissions are poorly understood. Bison are thought to have produced some 2&#8201;Tg&#8201;year&#8722;1 of the estimated 9&#8211;15&#8201;Tg&#8201;year&#8722;1 of pre-industrial enteric methane emissions, but few contemporary measurements have been made due to their mobile grazing habits and safety issues associated with direct measurements. Here, we measure methane and carbon dioxide fluxes from a bison herd on an enclosed pasture during daytime periods in winter using eddy covariance. Methane emissions from the study area were negligible in the absence of bison (mean&#8201;&#177;&#8201;standard deviation&#8201;=&#8201;0.0024&#8201;&#177;&#8201;0.042&#8201;&#956;mol&#8201;m&#8722;2&#8201;s&#8722;1) and were significantly greater than zero, 0.048&#8201;&#177;&#8201;0.082&#8201;&#956;mol&#8201;m&#8722;2&#8201;s&#8722;1 with a positively skewed distribution, when bison were present. We coupled an eddy covariance flux footprint analysis with bison location estimates from automated camera images to calculate a mean (median) methane flux of 38&#8201;&#956;mol&#8201;s&#8722;1 (22&#8201;&#956;mol&#8201;s&#8722;1) per animal, or 52&#8201;&#177;&#8201;14&#8201;g&#8201;CH4&#8201;day&#8722;1 (31&#8201;g&#8201;CH4&#8201;day&#8722;1), less than half of measured emission rates for range cattle. Emission estimates are subject to spatial uncertainty in bison location measurements and the flux footprint, but from our measurements there is no evidence that bison methane emissions exceed those from cattle. We caution however that our measurements were made during winter and that evening measurements of bison distributions were not possible using our approach. Annual measurements are ultimately necessary to determine the greenhouse gas burden of bison grazing systems. Eddy covariance is a promising technique for measuring ruminant methane emissions in conventional and alternate grazing systems and can be used to compare them going forward.

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“…The application of the EC technique to quantify CH 4 fluxes and other tracer gases was made possible with the development of fast-response and fielddeployable optical sensors [25]. The method requires the knowledge of animal numbers and their location within the footprint and a model to interpret the relationship between the calculated flux and the emission rate of point sources within the footprint [90]. Under the current technical conditions, minor fluctuations of air mass and energy flux on several time scales (hour, day, season, and year) can be measured [89].…”

Section: Eddy Covariance (Ec) Techniquementioning

confidence: 99%

Contemporary Methods of Measuring and Estimating Methane Emission from Ruminants

Bekele

Guinguina

Zegeye

et al. 2022

Methane

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This review aims to elucidate the contemporary methods of measuring and estimating methane (CH4) emissions from ruminants. Six categories of methods for measuring and estimating CH4 emissions from ruminants are discussed. The widely used methods in most CH4 abatement experiments comprise the gold standard respiration chamber, in vitro incubation, and the sulfur hexafluoride (SF6) techniques. In the spot sampling methods, the paper discusses the sniffer method, the GreenFeed system, the face mask method, and the portable accumulation chamber. The spot sampling relies on the measurement of short-term breath data adequately on spot. The mathematical modeling methods focus on predicting CH4 emissions from ruminants without undertaking extensive and costly experiments. For instance, the Intergovernmental Panel on Climate Change (IPCC) provides default values for regional emission factors and other parameters using three levels of estimation (Tier 1, 2 and 3 levels), with Tier 1 and Tier 3 being the simplest and most complex methods, respectively. The laser technologies include the open-path laser technique and the laser CH4 detector. They use the laser CH4 detector and wireless sensor networks to measure CH4 flux. The micrometeorological methods rely on measurements of meteorological data in line with CH4 concentration. The last category of methods for measuring and estimating CH4 emissions in this paper is the emerging technologies. They include the blood CH4 concentration tracer, infrared thermography, intraruminal telemetry, the eddy covariance (EC) technique, carbon dioxide as a tracer gas, and polytunnel. The emerging technologies are essential for the future development of effective quantification of CH4 emissions from ruminants. In general, adequate knowledge of CH4 emission measurement methods is important for planning, implementing, interpreting, and comparing experimental results.

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Applicability of Eddy Covariance to Estimate Methane Emissions from Grazing Cattle

Cited by 13 publications

References 34 publications

Methane efflux from an American bison herd

Methane efflux from an American bison herd

Methane efflux from an American bison herd

Contemporary Methods of Measuring and Estimating Methane Emission from Ruminants

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