|Rotz, Clarence - Al|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2013
Publication Date: 10/21/2013
Citation: Rotz, C.A., Isenberg, B.J., Stackhouse-Lawson, K.R., Pollak, E.J. 2013. A simulation-based approach for evaluating and comparing the environmental footprints of beef production systems. Journal of Animal Science. 91:5427-5437. Interpretive Summary: As a major food source, beef production provides an important service to our economy. Production of cattle and associated feed crops also impact our environment, and this impact is not well understood. Although several studies have been done to assess carbon footprint, there are other environmental impacts that must be considered. These include fossil energy use, water use, and reactive nitrogen loss to the environment. To further our understanding of the environmental impacts of beef production in the U.S., environmental footprints were determined for current and historical beef cattle production at the Roman L. Hruska U.S. Meat Animal Research Center, a USDA research facility that uses production practices similar to those of commercial cattle production. The current carbon footprint of the beef produced was found to be 10.9 kg of carbon dioxide equivalent units per kg of body weight sold, and the energy required to produce that beef (energy footprint) was 26.5 MJ/kg of body weight. The total water required (water footprint) was 21,300 liter/kg of body weight, and the water footprint excluding that obtained through precipitation was 2,790 liter/kg. An analysis of historical production practices indicate that over the past 40 years the carbon footprint of the beef produced has decreased 6% with no change in the energy footprint, and a 3% reduction in the reactive nitrogen footprint. Excluding precipitation, the water footprint has increased 42% due to greater use of irrigated corn production. This initial assessment provides a methodology that can be used to evaluate regional and national environmental improvements that have been made in beef cattle production.
Technical Abstract: A methodology was developed and used to determine environmental footprints of beef produced at the U.S. Meat Animal Research Center (MARC) in Clay Center, Nebraska with the goal of quantifying improvements achieved over the past 40 years. Relevant information for MARC operations was gathered and used to establish parameters representing their production system with the Integrated Farm System Model. The MARC farm, cow calf and feedlot operations were each simulated over recent historical weather to evaluate performance, environmental impact and economics. The current farm operation included 842 ha of alfalfa and 1,160 ha of corn to produce feed predominately for the beef herd of 5,500 cows, 1200 replacement heifers and 3,724 cattle finished per year. Spring and fall cow calf herds were fed on 9,720 ha of pastureland supplemented through the winter with hay and silage produced by the farm operation. Feedlot cattle were backgrounded 3 mo on hay and silage and finished over 7 mo on a diet high in corn grain and wet distiller’s grain. For weather year 2011, simulated feed production and use, energy use, and production costs were within 1% of actual records. A 25-year simulation of their current production system gave a carbon footprint of 10.9 kg of CO2 equivalent units per kg BW sold, and the energy required to produce that beef (energy footprint) was 26.5 MJ/kg BW. The total water required (water footprint) was 21,300 liter/kg BW sold, and the water footprint excluding that obtained through precipitation was 2,790 liter/kg BW. The simulated total cost of producing their beef was $2.11/kg BW sold, which agreed with their production records. Simulation of the production practices of 2005 indicate that the use of distiller’s grain in animal diets has had a relatively small effect on environmental footprints except that reactive nitrogen loss has increased 10%. Compared to 1970, the carbon footprint of the beef produced has decreased 6% with no change in the energy footprint, a 3% reduction in the reactive nitrogen footprint, and a 6% reduction in the real cost of production. The water footprint, excluding precipitation, has increased 42% due to greater use of irrigated corn production. This proven methodology provides a means for further analysis of regional and national environmental impacts of beef production.