112 An environmental assessment of beef cattle production in the United States.

摘要

Cattle production effects on the environment and the overall sustainability of beef have become national and international concerns. Our objective was to quantify important environmental impacts of beef cattle production in the United States. Surveys and visits of farms, ranches and feedlots were conducted throughout seven regions (Northeast, Southeast, Midwest, Northern Plains, Southern Plains, Northwest and Southwest) to determine common practices and characteristics of cattle production. These data along with those from other information sources were used to create 150 representative production systems throughout the country, which were simulated with the Integrated Farm System Model using local soil and climate data. The simulations quantified the performance and environmental impacts of production systems for each region. From these data, a farm-gate life cycle assessment quantified resource use and emissions for all production systems including traditional beef breeds and cull Holstein animals from the dairy industry. Regional and national totals were determined as the sum of the production system outputs times the number of cattle represented by each simulated system. The total of all greenhouse gas and reactive nitrogen emissions associated with beef cattle production were 244 ± 26 Tg CO2e and 1788 ± 138 Mg N, respectively. Total fossil energy use was 577 ± 55 PJ and blue water consumption was 23.4 ± 3.4 Pg. Environmental intensities expressed per kg of carcass weight produced were 21.5 ± 2.3 kg CO e, 157 ± 12 g N, 50.7 ± 4.8 MJ, and 1971 ± 302 kg, respectively for carbon, nitrogen, energy, and blue water. These farm gate values are being combined with post farm gate sources of packing, processing, distribution, retail, consumption and waste handling to produce a full life cycle assessment of U.S. beef. This is the most detailed, yet comprehensive, study to date on the sustainability of U.S. beef.