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Beef cattle are estimated to directly contribute 26% of U.S. agricultural greenhouse gas (GHG) emissions, and future climate change policy may target reducing these emissions. Life cycle assessment (LCA) of GHG emissions from U.S. feedlot beef cattle was conducted to compare methods of the U.S. Environmental Protection Agency (EPA) with a more complete evaluation of emissions. The inclusion of emissions from crop production for feed, associated land use change, and other minor factors nearly doubled GHG emissions associated with beef feedlots from the EPA Annual Inventory estimate of 1611 kgCO2e hd-1 yr-1 to 3182 ± 167 kgCO2e hd-1 yr-1. Feeding of coproducts from ethanol production is estimated to reduce feedlot emissions by 6%. Furthermore, inclusion of pasture and land use change emissions from the cow-calf stage of the animal life cycle nearly tripled GHG emissions compared to the feedlot LCA (6.0 to 16.67 ± 0.32 kgCO2e kg-1 beef). Despite use of expanded system boundaries in the LCA, U.S. beef cattle GHG emissions were lower than the majority of previous U.S. and international assessments of beef cattle. Nearly a 16-fold range in results can be found for U.S. beef using different system boundaries and assumptions. Use of LCA-driven carbon pricing on U.S. beef could reduce beef demand and associated beef GHG emissions by 2.7 to 21 Tg CO2e yr-1.
Advisor: Adam J. Liska
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