Nutrient shortages and agricultural recycling options worldwide, with special reference to China

Mineral nutrients such as Phosphorus and Zinc are getting scarcer worldwide. Unlike fossil fuels, for which over time substitutes can be developed, these nutrients cannot be substituted as they are essential for life on earth. For instance, in both plants and animals Phosphorus is a component of DNA, RNA, ATP and of phospholipids which form all cell membranes. Phosphorus is thus essential for the replication of cells and consequently growth and ultimately reproduction. Further, phosphorus in humans is mostly concentrated in bones giving shape to the human body, which largely consists of water. A significant fraction of these minerals is disposed of in the form of manure and considered a pollutant to be disposed of often via surface water eventually to the ocean or fixated in the soil which amounts to an almost irreversible loss. Another fraction is lost in industrial transformation. According to the US Geological Survey, the easily and economically mineable reserves of phosphate rock are sufficient for some 120 years of current consumption levels. In the case of Zinc this is 22 years. Moreover, phosphate rock resources are very unevenly distributed. For example, 65 per cent of Phosphate rocks are located in China, Morocco and Western Sahara. These conditions may affect Phosphorus availability elsewhere. This paper provides a first quantification for some essential mineral nutrients as they occur in different sections of the geosphere and explores possible solutions to ensure sustainable fertilizer options. For Phosphorus these include the mining of P on P-intoxicated land, abstaining from high and inefficient doses of P, and P recovery from urban human and animal waste as well as waste products from biofuel production. Further waste product recycling will be easier and less costly when production and consumption areas are geographically close. Saving options for micro-nutrients such as Zinc are largely similar to those for Phosphorus, but in addition can consist of the reduction of non-agricultural applications. The second part of the paper provides an application for China. We analyze net nutrient use in Chinese agriculture and address the question to which extent China can reduce this net demand in the coming decades, while meeting its requirements for food, feed and biofuel. For this, we use the Chinagro welfare model that comprehensively depicts China’s farm sector in 2433 counties while connecting these through trade and transportation flows to each other, to rural and urban consumers and to abroad. The model computes net surpluses from application of N, P and K fertilizer in crop fields. The paper presents scenario simulations suggesting excessive use of N and P, while K application is insufficient and actually mined from the soil. The findings thus indicate that more balanced fertilizer mixes will be required to sustain high crop yields, which simultaneously would reduce currently experienced environmental problems.