Meta-Analysis of Strategies to Reduce NH3 Emissions from Slurries in European Agriculture and Consequences for Greenhouse Gas Emissions

Summary

This meta-analysis of peer-reviewed European experimental data evaluated management strategies to reduce ammonia emissions from livestock slurries, with specific attention to unintended increases in other greenhouse gas emissions (pollution swapping). Slurry acidification emerged as the only strategy that significantly reduced ammonia emissions (−69%) without increasing other greenhouse gases, whilst alternative approaches including biological treatment, separation, storage modification, and variable application methods reduced ammonia but increased emissions of methane, nitrous oxide, or carbon dioxide. The authors recommend combining multiple technologies such as acidification with soil incorporation, alongside emerging approaches like microbial inhibitors and slow-release fertilisers, to achieve holistic greenhouse gas mitigation.

Regional applicability

These findings are directly applicable to UK intensive livestock systems, where slurry management is subject to increasingly stringent air quality regulations. The meta-analysis provides evidence-based guidance for UK policy and farm practice, particularly relevant to nitrogen and ammonia regulations under the Environment Act 2021 and future agricultural support schemes.

Key measures

Ammonia (NH3) emission reductions expressed as percentages; concurrent changes in methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) emissions

Outcomes reported

The meta-analysis evaluated the efficacy of major agricultural management practices on ammonia emissions from slurries across treatment, storage, and application stages, whilst assessing potential pollution swapping effects with other greenhouse gases (methane, nitrous oxide, carbon dioxide).

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