Strategies to mitigate nitrous oxide emissions from herbivore production systems

Area of Science:

• Agricultural Science
• Environmental Science
• Animal Science

Background:

• Herbivores are a major source of nitrous oxide (N2O) emissions, contributing significantly to both manure- and soil-related N2O.
• Growing global food demand necessitates mitigation strategies to prevent increased N2O emissions from livestock systems.
• Nitrous oxide production and emissions are intrinsically linked to nitrogen (N) transfer efficiency within livestock systems (animal, manure, soil, crop).

Purpose of the Study:

• To review and structure mitigation options for nitrous oxide (N2O) emissions from livestock systems.
• To identify and categorize N2O mitigation strategies across different nitrogen pathways within livestock production.
• To highlight the importance of integrated approaches considering N and carbon cycles and potential trade-offs with other greenhouse gases.

Main Methods:

• Literature review and synthesis of existing mitigation strategies for N2O emissions in livestock.
• Categorization of mitigation options based on nitrogen (N) transfer pathways: diet, animal, soil, and crop.
• Analysis of the impact of N2O mitigation options on N and carbon cycles and other greenhouse gas emissions.

Main Results:

• Dietary interventions (e.g., reduced crude protein, increased condensed tannins) and breeding for improved N conversion are key animal-related options.
• Soil-based measures include efficient fertilizer/manure use and nitrification inhibitors; reducing grazing time is effective in pasture systems.
• Crop-based solutions involve breeding for N-use efficiency and incorporating N2-fixing clover pastures.
• All mitigation strategies impact N and carbon cycles, requiring careful consideration to avoid offsetting N2O reductions with increased ammonia, methane, or CO2 emissions.

Conclusions:

• A wide array of N2O mitigation options exists for livestock systems, targeting various N pathways.
• Practical implementation of N2O mitigation lags due to insufficient farmer awareness and targeted policies.
• Achieved N2O emission reductions have largely been co-benefits of other nitrogen-focused policies, indicating a need for more direct N2O strategies.