PSXI-28 - Nitrogen footprint assessment of Korean native beef cattle farms: Uncertainty analysis and mitigation scenarios

Abstract: Nitrogen (N) lost during beef cattle production accompanies various environmental impacts and has become a rising concern among agricultural stakeholders. The objective of this study was to quantify the N footprint (NF) of Hanwoo beef cattle production in Korea at the farm gate through a life cycle assessment methodology. Field surveys were conducted on 106 farms across nine provinces to evaluate the NF of Hanwoo beef farms. N losses were calculated using emission factors using the refined Intergovernmental Panel on Climate Change (IPCC) guideline and expressed as NF (g N lost/kg of live body weight (LBW)). Uncertainty and sensitivity analyses were deployed to evaluate the precision of the results and to quantify the variability of the input data. The NF was averaged 132.8 (±61.9) g N/kg LBW. Volatilization was the highest contributing factor, followed by leaching and denitrification, each representing 68.4, 21.4, and 10.1 percent of the NF, respectively. The uncertainty of the output data was found to be 46.6 percent and was highly associated with emission factors uncertainties. We simulated four feasible mitigation scenarios that are cost effective and do not penalize productivity, and evaluated their capacity for reducing NF of meat: dietary modifications to decrease animal N excretion rates by adjusting the CP and rumen undegradable protein content for steers and fattening cows (A), microorganism additives to reduce volatilization from housing and manure storages through processing excess ammonium to synthesize microbial protein (B), using manure as land fertilizer instead of synthetic fertilizers to decrease denitrification from rice cultivation, and leaching and volatilization from all field types(C), and distributing straw-derived biochar (10-20 ton/ha) to the field after fertilizer application to reduce losses from crop production (D).

Combining these scenarios demonstrated the potential to reduce NF by 12.3 percent. Overall, our study provides a national metric that can be used to communicate the N uses impact of Korean beef production. The analyses indicate that more precise results could be achieved with future endeavors toward developing country-specific emission factor s. Integrating all four scenarios was shown to be the most effective approach to reducing the NF of beef production.