Tracing Nitrogen Flows Associated with Beef Supply Chains: A Consumption-Based Assessment.

Area of Science:

• Environmental Science
• Agricultural Science
• Supply Chain Management

Background:

• Highly connected food chains lack traceability and transparency, hindering efforts to manage environmental burdens.
• Reactive nitrogen release from food systems is linked to biodiversity loss and water quality degradation.
• Beef production, particularly feed production, is associated with substantial nitrogen footprints.

Purpose of the Study:

• To develop a framework for tracing spatial heterogeneity in nitrogen releases throughout the U.S. beef supply chain.
• To quantify the nitrogen footprint of beef consumption at the county level.
• To analyze the disparity between consumption-based and production-based nitrogen impacts.

Main Methods:

• An optimization-based framework was developed to trace beef product supply chains at the county level.
• Publicly available data were used to construct a weighted network of nutrient flows based on mass balance.
• The model incorporated synthetic fertilizers, manure production, and crop uptake and residues.

Main Results:

• Beef consumption in one U.S. county can lead to nitrogen losses in hundreds of other counties.
• Annual U.S. beef consumption releases approximately 1.33 teragrams (Tg) of nitrogen (N) into the environment.
• The majority of nitrogen pollution occurred during the feed production phase as diffuse pollution.

Conclusions:

• Understanding the spatial distribution of nitrogen losses is critical for targeted environmental interventions in the beef supply chain.
• Consumption-based accounting is essential for a comprehensive assessment of the environmental sustainability of beef production.
• Significant disparities exist between the environmental impacts of beef production and consumption, highlighting the need for supply chain transparency.