Urban Metabolism of Food-Sourced Nitrogen among Different Income Households: A Case Study Based on Large Sample Survey in Xiamen City, China.

Li Xing,Yu Zhao,Tao Lin,Xiongzhi Xue,Meixia Lin,Jiakun Liu

doi:10.3390/foods10112842

Abstract

Food consumption is fundamental for urban households if they are to sustain production and daily life. Nitrogen resulting from food consumption has significantly contributed to pollutant emissions in urban ecosystems. Taking Xiamen city, a rapid urbanizing area of southeast China as a case study, we evaluated the food-sourced nitrogen consumption of households based on a large simple onsite questionnaire survey, as well as differences between households in the consumption of plant-based and animal-based foods. A material flow analysis (MFA) was conducted to simulate the urban metabolism of food-sourced nitrogen and environmental emissions among different income groups. The impacts of household attributes, plant-based food consumption, and animal-based food consumption on environmental nitrogen emissions were examined with a structural equation model (SEM). Our results show that the surveyed households’ diets were more plant-based and less animal-based. Aquatic products and livestock were the source of 43.7% of food-sourced nitrogen, and 84.5% of the food-sourced nitrogen was discharge into the environment through direct discharge and waste treatment. Soil, water, and air emissions accounted for 62.8%, 30.1%, and 7.1% of the food-sourced nitrogen, respectively. Household income, household size, and household area are all associated with accelerating increases of nitrogen emissions released into the environment, though middle-income group households have the highest food-sourced environmental nitrogen emissions. On this basis, we discuss how to better manage the urban metabolism of food-sourced nitrogen, so as to improve urban household consumption, lower nitrogen emissions, and improve food security.

Highlights

Nitrogen is a major component of proteins, which are necessary for the existence of human beings and all other living organisms [1]
J where HWi represents the total nitrogen of food consumption in household i; Pi is the population in household i, that is, household size; W p is the nitrogen content of per capita food consumption in household i; w pj refers to the nitrogen content of food j consumption per capita; n is the category of household food consumption, n = 9; w j is the amount of food j consumption per capita. p j is the coefficient of the nitrogen content in food j, which hinges on the protein content according to the “2014–2018 China Mainland Food Balance
The six categories of income household consumption be ranked in decreasing order ing urban household environmental nitrogen emissions

Summary

Introduction

Nitrogen is a major component of proteins, which are necessary for the existence of human beings and all other living organisms [1]. Nitrogen flows and metabolic processes within cities are growing rapidly due to human activity [2,3,4,5,6,7,8,9]. Cities depend on nitrogen input, distribution, and output by human-dominated processes to maintain their functioning. This is commonly known as urban nitrogen metabolism [10,11]. Though essential, these processes have adverse impacts on the soil, water and atmosphere, and result in enhanced greenhouse effects [12,13], photochemical smog [14,15], water quality degradation [16,17,18], loss of soil nutrients [19,20], and biodiversity loss [21,22]. Urban nitrogen metabolism research has attracted increased attention in regional sustainable development [23]

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Results

Discussion

Conclusion