Estimating herd-scale methane emissions from cattle in a feedlot using eddy covariance measurements and the carbon dioxide tracer method Article

Prajapati, P, Santos, EA. (2019). Estimating herd-scale methane emissions from cattle in a feedlot using eddy covariance measurements and the carbon dioxide tracer method . JOURNAL OF ENVIRONMENTAL QUALITY, 48(5), 1427-1434. 10.2134/jeq2018.09.0332

cited authors

  • Prajapati, P; Santos, EA

abstract

  • Measurements of methane (CH4) emissions from ruminants could provide invaluable data to reduce uncertainties in the global CH4 budget and to evaluate mitigation strategies to lower greenhouse gas emissions. The main objective of this study was to evaluate a new CO2 tracer (CO2T) approach that combined CH4 and CO2 atmospheric concentrations with eddy covariance (EC) CO2 flux measurements to estimate CH4 emissions from cattle in a feedlot. A closed-path EC system was used to measure CH4 and CO2 fluxes from a feedlot in Kansas. The EC flux measurements were scaled from landscape to animal scale using footprint analyses. Emissions of CH4 from the cattle were also estimated using the CO2T approach and measured CO2 and CH4 concentration, and scaled EC CO2 fluxes. The CH4 and CO2 concentration ratios showed a distinct diel trend with greater values during the daytime. Average monthly CH4 emission estimates using the CO2T approach ranged from 72 to 127 g animal−1 d−1, which was consistent with the values reported in other studies that had similar animal characteristics. The CO2T method CH4 emission estimates showed good agreement with scaled CH4 EC fluxes (slope = 0.9 and R2 = 0.8) for cold and dry months. However, the agreement between the two techniques was significantly reduced (slope = 1.5 and R2 = 0.6) during wet and warm months. On average, the CO2T method CH4 emission estimates were 3% greater than the EC CH4 emissions. Overall, our results suggest that the CO2T method can be used to estimate enteric feedlot CH4 emissions.

publication date

  • January 1, 2019

published in

Digital Object Identifier (DOI)

start page

  • 1427

end page

  • 1434

volume

  • 48

issue

  • 5