On-farm case study of greenhouse gas emissions for beef enterprises

Summary

​In response to climate change, research is being undertaken to understand the on-farm greenhouse gas (GHG) emissions for agricultural systems and investigate options farmers may have for mitigating or offsetting emissions. In this study a Life Cycle Assessment (LCA) framework is used to determine both on-farm GHG emissions and the overall 'cradle-to-farm gate' emissions attributed to beef production. The total on-farm emissions for the two properties were 2,984 t CO2-e/yr (or 1.93 t/livestock unit) for the 634-cow enterprise turning off weaner cattle at Gympie and 5,725 t CO2-e/yr (or 1.70 t/livestock unit) for the 720-cow enterprise turning off finished steers in the Arcadia Valley. The on-farm emissions are largely attributable to enteric methane emissions from the beef herd. 
The overall 'cradle-to-farm gate' GHG emissions associated with enterprise products were 3,145 t CO2-e/yr at Gympie and 7,422 t CO2-e/yr in the Arcadia Valley, with the additional emissions coming from off-farm inputs (fuel for farm vehicles and earth moving equipment, electricity, supplementary feed, agricultural chemicals, farm services) and additionally, for the Arcadia Valley enterprise, from purchased store steers. The carbon footprint of beef products at the farm gate ranged from 15.8-23.4 kg CO2-e/ kg live weight at Gympie and 11.6-16.5 kg CO2-e/ kg live weight in the Arcadia Valley. 
The ability to off-set on-farm emissions through reforestation varied between the two locations, with predicted biosequestration rates of 19.3–34.7 t CO2-e/ha/yr at Gympie (rainfall 1200 mm/year) from eucalypt plantation and 1.5–9.8 t CO2-e/ha/yr in the Arcadia Valley (rainfall 600 mm/year) through reforestation from a combination of Brigalow regrowth, leucaena and environmental eucalypt plantings. The area that would need to be reforested to off-set on-farm emissions would be 86-155 ha at Gympie (7-13% of the holding) and 629-4,108 ha in the Arcadia Valley (9-60%). 
If carbon sequestration could be achieved at the higher end of the rates nominated, a significant proportion of on-farm emissions could be off-set by sequestration in timber with minimal impact on beef production. However, at the lower end of the forest sequestration range, the required level of land use change would reduce the carrying capacity, and hence beef production, especially at the Arcadia Valley site.