From Production to Application : A Systematic Analysis of Nitrogen Flow in China

Nitrogen is one of the most important elements in natural ecosystems and organism. Due to the rapid economic development of China, a large amount of anthropogenic nitrogen has been invested to meet human consumption demand,... [ view full abstract ]

Nitrogen is one of the most important elements in natural ecosystems and organism. Due to the rapid economic development of China, a large amount of anthropogenic nitrogen has been invested to meet human consumption demand, including food, energy and industrial nitrogen. At present, China is the world's largest producer of reactive nitrogen and consumer of nitrogen fertilizer. However, the nitrogen use efficiency is pretty low due to irrational use of nitrogen and a large amount of nitrogen losses. It has brought serious environmental nitrogen pollution problem (e.g., groundwater nitrate enrichment, fresh water eutrophication, air pollution and human health effects), which is in the hot spot of global nitrogen cycle research. To map the potential towards increasing nitrogen use efficiency and reduce environmental losses, a high-resolution insight of the nitrogen streams is pivotal. This study provides a substance flow analysis for nitrogen based on life cycle thinking which focuses on agriculture, industry, human consumption, waste management, atmosphere and hydrosphere subsystems at large-scale in China for the year 2014. The key factors influencing nitrogen use efficiency were identified by constructing a nitrogen metabolism model with human consumption as the core. Through the quantitative analysis of agricultural, industrial and human consumption subsystems, the main ways of nitrogen losses were found out. In conclusion, reducing nitrogen impacts requires increasing the on-farm nitrogen use efficiency reducing nitrogen oxide emissions. Furthermore, it requires the development of efficient formulation fertilizers and the advancement of agricultural fertilization and industrial models, which can reduce the application rates of nitrogen fertilizer by about 25%. Except for agriculture activities, encouraging reasonable and balanced dietary structure, improved manure and waste management and new efficient technologies that are ideal for increasing nitrogen use efficiency and reducing nitrogen emissions.