Evaluating greenhouse gas mitigation practices in livestock systems: an illustration of a whole-farm approach

Abstract

SUMMARYAs agriculture contributes about 0·08 of Canada's greenhouse gas (GHG) emissions, reducing agricultural emissions would significantly decrease total Canadian GHG output. Evaluating mitigation practices is not always easy because of the complexity of farming systems in which one change may affect many processes and associated emissions. The objective of the current study was to compare the effects of selected management practices on net whole-farm emissions, expressed in CO2equivalents (CO2e) from a beef production system, as estimated for hypothetical farms at four disparate locations in western Canada. Whole-farm emissions (t CO2e) per unit of protein output (t) of 11 management systems (Table 2) were compared for each farm using a model based, in part, on Intergovernmental Panel on Climate Change (IPCC) equations. Compared with the baseline management scenario, maintaining cattle on alfalfa-grass pastures showed the largest decrease (0·53–1·08 t CO2e/t protein) in emissions for all locations. Feeding lower quality forage over winter showed the greatest increase in emissions per unit protein on the southern Alberta (S.AB) and northern Alberta (N.AB) farms, with increases of 1·36 and 2·22 t CO2e/t protein, respectively. Eliminating the fertilization of forages resulted in the largest increase (4·20 t CO2e/t protein) in emissions per unit protein on the Saskatchewan (SK) farm, while reducing the fertilizer rate by half for all crops showed the largest increase (11·40 t CO2e/t protein) on the Manitoba (MB) farm. The findings, while approximate, illustrate the importance of considering all GHGs simultaneously, and show that practices which best reduce emissions may vary among locations. The findings also suggest merit in comparing emissions on the basis of CO2e per unit of protein exported off-farm, rather than on the basis of total CO2e or CO2e per hectare.