Tracking social-economic system nitrogen flow in China for emissions reduction and efficiency improvement

The increasing human demand have driven intensive reactive nitrogen (Nr) use, leading to high emissions and low efficiency in entire social-economic system. Herein, we accomplished a social-economic Nr flow model to trace the multi-sectorial Nr use, efficiency, and emissions in China from 1980 to 2020. The results showed that Nr use intensity increased 3.1-fold within four decades, with the decreasing proportions of Nr recovery from 32.7 % to 16.8 %. The Nr use pathways of production, consumption and waste management stages showed low resources use efficiency in agriculture and industrial production, high degree of consumption loss, insufficient waste treatment characteristics currently. Nr emissions peaked in 2012 and declined 12.7 % to 2020 owing to the nitrogen oxides control and mitigating overuse of fertilizers, and will continuously decrease under strategies in 2040 (41.7 % compared with 2012), indicating the large potential for emission reduction and efficiency improvement in next few decades.