Evaluating dispersion modeling options to estimate methane emissions from grazing beef cattle

Area of Science:

• Agricultural Science
• Environmental Science
• Atmospheric Science

Background:

• Enteric methane (CH4) emissions from cattle represent a significant greenhouse gas source and an energy loss, impacting livestock production efficiency.
• Accurate quantification of enteric CH4 emissions is crucial for evaluating mitigation strategies and understanding its environmental impact.

Purpose of the Study:

• To assess the influence of cattle stocking density on enteric CH4 emissions.
• To evaluate the effect of different source configurations (point vs. area source, and area source elevation) on CH4 emissions from grazing beef cattle.
• To validate the use of nonintrusive atmospheric measurements and gas dispersion modeling for estimating CH4 emissions.

Main Methods:

• Employed nonintrusive atmospheric measurements to quantify CH4 emissions from grazing beef cattle.
• Utilized a gas dispersion model to analyze emission data based on source configuration and stocking density.
• Compared CH4 emissions between point-source and area-source configurations, including elevated and ground-level area sources.

Main Results:

• Average measured enteric CH4 emission ranged from 240 to 250 g/animal/day for both point and area sources.
• No significant difference in CH4 emissions was observed between elevated (0.5 m) and ground-level (0 m) area sources.
• Stocking density influenced CH4 emissions in the point-source configuration, with some variations also noted for area-source emissions.

Conclusions:

• The study highlights the flexibility of the area-source configuration within the gas dispersion model for estimating CH4 emissions, even under low stocking densities.
• Findings contribute to a better understanding of factors affecting enteric CH4 emissions in beef cattle and inform mitigation efforts.
• Nonintrusive atmospheric measurements offer a viable method for assessing CH4 emissions in grazing systems.