Mitigation potential of agricultural Ammonia in China and associated costs and benefits

This study conducts the first comprehensive assessment of national NH3 mitigation based on multiple models. Our study reveals there are considerable societal benefits (US$ 32-75 billion) for China to reduce agricultural NH3 emissions compared to its implementation costs (US$ 6-11 billion). The technical mitigation potential of agricultural NH3 emissions in China is 53% (38-67%), around two times higher than the Europe27 (~24%). Saving unnecessary N fertilizer use and protein-rich feed could provide 30% of mitigation potential without abatement cost. Apart from technical mitigation options, reducing consumption of animal products could offer further NH3 mitigation potential by 2050.

Growing evidence suggest that further improvement of air quality and public health in China need the involvement of NH3 mitigation. However, China has not yet formulated and introduced policies to reduce NH3 emissions and there is no available systematic assessment of NH3 mitigation potential, costs and benefits. 2 Agricultural NH3 mitigation potential and costs 2.1 Marginal abatement cost curve (MACC) A bottom-up NH3 MACC (Fig.1) for China reveals that a reduction of 1.6 Tg NH3-N (30% of the total reduction) is potentially available at zero cost for the agricultural sector by saving unnecessary fertilizer use and protein-rich feed. 2.2 Comparison with other countries China has around two times higher NH3 mitigation potential (~53%) than the EU27 (~24%) and Canada(~29%) with lower unit implementation cost (US$ 0.8-2.1 per kg NH3-N abated). This is not surprising because as a developing agriculture country, China has the highest level of NH3 emissions in the world and has not yet implemented mitigation policies. 3 Mitigation passway and environmental benefits Four mitigation scenarios (DIET, NUE, REC and ALL) towards 2050 are simulated to explore optimal NH3 mitigation pathways. Results reveal that ALL scenerio has the largest NH3 mitigation potential and abatement costs, but also the highest net economic benefits (US$ 44-77 billion). 4 Policy implications Saving unnecessary N fertilizer use and protein-rich feed (cheap and easy mitigation options) should be introduced first to pick the “low-hanging fruit” of NH3 mitigation in China. Apart from improving agricultural management with technical options, human dietary change, as a non-technical strategy, will play an important role in reducing agricultural NH3 emissions in China in the next 30 years.