Global agricultural greenhouse gas emissions: Enteric methane in IPCC reports
Joshua Bourassa*1, Elena Vinco2
1 University of Calgary, Calgary, AB, Canada, Simpson Centre, The School of Public Policy
Efforts to reduce emissions across sectors are implemented globally, as increasing environmental, social, and economic pressures accumulate. Methane from enteric fermentation is the single largest source of agricultural-based greenhouse gas emissions in Canada. The Global Methane Pledge, an agreement between over 100 different countries including the USA and EU, commits to limiting average global temperature increase to ≤ 1.5 degrees. Parties committed to the pledge are required to disclose national methane emissions following IPCC guidelines. High variability in emission estimates and calculation methodology for enteric methane produced by cattle in the agricultural sector confound comparability between countries and previous reports. Depending on use of Tier 1, 2, 3, although the e IPCC generally recommends using a Tier 2 or 3 approach for dairy and beef cattle, approaches and default emission factors covering different animal, ration, management, and environmental dimensions, emission factors uncertainty values ranged from ±6 to ±50 percent. As the specificity and resolution of data increases as countries move from Tier 1 to Tier 2 and Tier 3 approaches, the resulting emission factors should increase in accuracy, accordingly, reflecting regional and country-specific operations. Relative to the other Annex I Parties to the United Nation Framework Convention on Climate Change, average methane emission per head of dairy cattle in Canada is high, linked to increased animal weight and milk productivity. Conversely, average non-dairy cattle emission per head in Canada is low, and is ranked the lowest among major global producers. The current IPCC methodology is not inclusive of current and prospective reduction technologies. Failure to account for various reduction technologies may deter implementation of strategies to reduce methane, as emission reduction in cattle herds would not be reflected. This increasingly prevalent reporting gap impedes future reliability and accuracy of methane reporting and disclosures and should be addressed in future methodology updates to ensure systematic calculations and improved emission estimates.
Keywords: Agriculture, enteric fermentation, greenhouse gas emissions, methane, national inventory report
Contact Address: Elena Vinco, University of Calgary, Calgary, AB, Canada, Simpson Centre, The School of Public Policy, 906 8 ave sw, T2P 1H9 Calgary, Canada, e-mail: elena.vincoucalgary.ca