From Production to Consumption: A Coupled Human–Environmental Nitrogen Flow Analysis in China

Abstract

Anthropogenic inputs of reactive nitrogen (Nr) provide sufficient food, energy, and industrial products to meet human demands; however, only a fraction of Nr is consumed as food and nonfood goods, and the rest is lost to the environment and negatively affects ecosystems. High-resolution studies of nitrogen flows are invaluable to increase nitrogen use efficiencies and reduce environmental emissions. In this study, a comprehensive substance flow analysis of nitrogen for China in 2014 is presented. Based on the conceptual framework, which highlights the key roles of human drivers, the analysis of the synthetic ammonia supply and demand balance shows that 75% of ammonia is used for agricultural purposes. Moreover, the life cycle analysis of food nitrogen shows that human food consumption accounts for approximately 7% of the total Nr inputs. A quantitative analysis of pollutant emissions shows that industrial and crop production are the main sources of atmospheric emissions, while livestock farming and crop production are the main sources of water emissions. Finally, we investigate four scenarios (efficiency improvement, high recycling rate, nitrogen oxide emission reduction, and a combined scenario) and provide relevant policy recommendations (large farm size, standardized agricultural production model, flue gas denitration, etc.) for improving nitrogen management practices.

Aggravation of reactive nitrogen flow driven by human production and consumption in Guangzhou City China

“…HBNF was used to produce N fertilizers and other synthetic ammonia products (e.g., plastics, synthetic rubbers, synthetic fibers, detergents, drugs and other products). Our estimate of the HBNF input intensity in 2015 was 114.6 kg N ha −1 y −1 , which was higher than the average value in China (~48.9 kg N ha −1 y −1 ) 29 . Another important characteristic of Nr inputs in Guangzhou was the heavy reliance on external supplies, especially agricultural products.…”

“…In 2015, Nr transfer to rivers from domestic wastewater accounted for 78% of the total Nr input into rivers, indicating that in a developed urban system, Nr transfer to rivers is primarily due to human consumption rather than productive and natural processes. The situation differed with respect to the Nr sources of the water in China, where Nr in the water was mainly derived from processes associated with livestock production and the loss of N fertilizer 29 .…”

The trends of aquacultural nitrogen budget and its environmental implications in China

“…Therefore, it is necessary that a national monitoring programme globally manage and monitor trends in point source pollution and diffuse agricultural pollution sources. Taking N pollution as an example, problems such as N fertilizer surplus in agriculture, industrial Nr emissions (such as those from the chemical, meat, textiles, and food processing industries), and Nr wastewater discharge from residents require attention and corresponding actions 23 .…”

Analysis of anthropogenic nitrogen and its influencing factors in Beijing

“…and NOx emission caused by food and energy production increased nearly threefold between 1860 and 1990 (Galloway et al, 2004), adversely affecting human health and regional sustainability (Luo et al, 2018). Due to the high concentration of people and socioeconomic activities that occurs in cities, these problems become particularly prominent at the scale of cities, and cities have become global hotspots of concern (Gu et al, 2009).…”

“…The same accounting system was also applied to the net anthropogenic nitrogen input in a study in the Victoria Basin in East Africa (Zhou et al 2014) and the Huaihe River Basin in China (Zhang et al 2016a). In addition, unlike previous studies, Luo et al (2018) considered nitrogen in industrial use, human consumption, and agriculture, and the nitrogen recovered by the waste management system in coupled human-environment nitrogen flows in China.…”