Halving global ammonia emissions with cost-effective measures

Excess ammonia (NH3) emissions from human activities pose severe threats to global ecosystems and human health. Although urgent control of NH3 emissions is needed, a comprehensive quantification of mitigation strategies and their cost-effectiveness is lacking on a global scale. Here we employ a multi-model framework to evaluate 32 mitigation measures across 7 sectors in 185 countries. Our analysis reveals that strategic implementation of technological and non-technological (policy and behavioural) measures could reduce global NH3 emissions by up to 60% at an average cost of US$7.4 per kilogram of NH3. The estimated implementation cost of US$274 ± 116 billion is far outweighed by the resulting environmental, health and resource benefits, which we indicatively estimate at US$722 ± 302 billion. Priority action in China and India could yield the largest net gains, whereas Sub-Saharan Africa faces limited cost-effectiveness owing to structural and economic barriers. Future scenarios indicate that ambitious implementation pathways could halve NH3 emissions by 2050, whereas weak climate action and inadequate nitrogen regulations would drive continued emission growth, leading to substantial environmental deterioration. These findings highlight both the feasibility and urgency of integrating NH3 control into multi-objective policies for food security, air quality and sustainable development.