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An environmental assessment of dairy farms in the eastern United States.

R. Stout




An environmental assessment of dairy farms in the eastern United States.
C. A. Rotz1, R. Stout*1, M. Holly2, P. Kleinman1. 1USDA-ARS University Park, PA, 2University of Wisconsin-Green Bay Green Bay, WI.

There is need for a comprehensive assessment of the environmental impacts of dairy farms at regional and national scales to better track improvements made by the industry. A methodology using process-level simulation and cradle to farm-gate life cycle assessment has been applied to the eastern United States with plans for completing all regions of the country. Representative dairy farms of various sizes and management practices are simulated with the Integrated Farm System Model using the soil characteristics and climate where farms are located. Farm-gate footprints are determined by totaling values among farms and locations within the region considering the amounts of milk produced by each. Northeastern dairy farms were determined to emit 12,455 � 1,100 Gg CO2e of greenhouse gas with an intensity of 0.99 � 0.09 kg CO2e per kg of fat and protein corrected milk (FPCM) produced. Fossil energy consumption was 33,542 � 5,300 TJ or 2.68 � 0.42 MJ per kg FPCM. Blue (non-precipitation) water consumption was 193 � 42 Tg with an intensity of 15.4 � 3.4 kg per kg FPCM. A total of all forms of reactive N loss was 108 � 13 Gg with an intensity of 8.6 � 1.0 g per kg FPCM. These metrics were equivalent to 1.5% of the greenhouse gas emissions, 0.32% of fossil energy use and 0.87% of fresh water consumption reported by governmental agencies for recent years covering all states in the region. Thus, greenhouse gas emissions, fossil energy use and blue water use associated with dairy farm production in this region are relatively small compared with total estimates. Simulated emissions of volatile organic compounds were also within 2% of governmental estimates for the region. The greatest environmental concern appears to be that of ammonia emission, where dairy farms accounted for 65% of governmental estimates for the region. Environmental footprints were found to vary widely among farms as influenced primarily by soil characteristics and climate and secondarily by farm management. Therefore, prescriptive mitigation strategies for individual farms is more effective than uniform enforcement of specific strategies.

Keywords: life cycle assessment, greenhouse gas, nitrogen loss.