Investigating Methane Emissions from Cattle Facilities in Northeastern Colorado

Agriculture is the second-largest anthropogenic source of methane (CH4) in the United States, after oil and natural gas production. Regions like northeastern Colorado are home to animal feeding facilities and oil and natural gas production. The proximity of interfering CH4 sources makes it challenging to quantify CH4 emissions from cattle. Using aircraft measurements of CH4, ammonia (NH3), and ethane (C2H6) from the Transport and Transformation of Ammonia (TRANS2Am) campaign, we calculated CH4 emissions from concentrated animal feeding operations (CAFOs) using a mass balance equation and a multivariate regression (MVR) approach. We calculated an average CH4 emission rate from beef cattle facilities as 7.2 ± 2.7 g head-1 hour-1. A unique aspect of the TRANS2Am campaign was the repeated sampling of individual CAFOs, which helped constrain uncertainties in the mass balance and MVR approaches and enabled evaluation of variability in CAFO emissions. Additionally, this study examines CH4 emission variability as a function of the number of cattle, cattle type, and time of day. Though both the number of cattle and cattle type are factors in cattle CH4 emissions, they do not fully explain the range of CH4 emissions observed during this study. The largest variability occurred at the daily time scale, suggesting that facility management practices drive some of the observed variability and highlighting the need to measure emissions from individual facilities and link them to specific management practices to understand the variability in cattle emissions.