Estimates of animal methane emissions

Area of Science:

• Environmental Science
• Agricultural Science
• Climate Science

Background:

• Domestic animals contribute significantly to atmospheric methane (CH4) emissions, totaling approximately 77 Tg annually from enteric fermentation and 10-14 Tg from manure management.
• Ruminants, primarily cattle and buffalo, account for about 95% of global enteric methane due to their digestive processes and large populations.

Purpose of the Study:

• To highlight the significant contribution of domestic animal agriculture to global methane emissions.
• To identify key factors influencing the accuracy of methane emission estimations from livestock.
• To underscore the need for precise data on animal populations and feed intake.

Main Methods:

• Analysis of global livestock census data and estimated feed consumption patterns.
• Quantification of methane production as a fraction of gross energy intake for various ruminant species.
• Assessment of methane release from different animal manure disposal systems, particularly anaerobic lagoons.

Main Results:

• Enteric methane emissions from domestic animals are estimated at 77 Tg/year, with ruminants being the primary source.
• Manure disposal systems contribute an additional 10-14 Tg of methane annually.
• The fraction of gross energy lost as enteric methane for cattle, sheep, and goats typically ranges from 5.5% to 6.5%.
• Methane emissions from manure are significantly affected by the prevalence of anaerobic lagoon disposal methods.

Conclusions:

• Accurate estimation of livestock methane emissions is crucial for climate change mitigation strategies.
• Improving the accuracy of cattle and buffalo census data and diet consumption estimates is essential for refining emission factors.
• Non-ruminant livestock, such as swine, are becoming increasingly significant contributors to methane emissions, particularly from manure management.