Environmental Research Letters (Jan 2017)
How China’s nitrogen footprint of food has changed from 1961 to 2010
Abstract
People have increased the amount of reactive nitrogen (Nr) in the environment as a result of food production methods and consumption choices. However, the connection between dietary choices and environmental impacts over time has not yet been studied in China. Here we combine a nitrogen footprint tool, the N-Calculator, with a food chain model, NUFER (NUtrient flows in Food chains, Environment and Resources use), to analyze the N footprint of food in China. We use the NUFER model to provide a detailed estimation of the amounts and forms of Nr released to the environment during food production, which is then used to calculate virtual nitrogen factors (VNFs, unit: kg N released/kg N in product) of major food items. The food N footprint consists of the food consumption N footprint and food production N footprint. The average per capita food N footprint increased from 4.7 kg N capita ^−1 yr ^−1 in the 1960s to 21 kg N capita ^−1 yr ^−1 in the 2000s, and the national food N footprint in China increased from 3.4 metric tons (MT) N yr ^−1 in the 1960s to 28 MT N yr ^−1 in the 2000s. The proportion of the food N footprint that is animal-derived increased from 37% to 54% during this period. The food production N footprint accounted for 84% of the national food N footprint in the 2000s, compared to 62% in the 1960s. More Nr has been added to the food production systems to produce enough food for a growing population that is increasing its per-capita food consumption. The increasing VNFs in China indicate that an increasing amount of Nr is being lost per unit of N embedded in food products consumed by humans in the past five decades. National N losses from food production increased from 6 MT N yr ^−1 in the 1960s to 23 MT N yr ^−1 in the 2000s. N was lost to the environment in four ways: ammonia (NH _3 ) emissions and dinitrogen (N _2 ) emissions through denitrification (each account for nearly 40%), N losses to water systems (20%), and nitrous oxide (N _2 O) emissions (1%). The average per capita food N footprint in China is relatively high compared with those of developed countries in the 2000s. To reduce the food N footprint in China, it is important to both reduce the Nr losses during food production and encourage diets associated with a lower N footprint, such as shifting towards a more plant-based diet.
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