Resource footprint and environmental load of phosphorus metabolism in food production and consumption system: evidence from Zhangzhou prefecture in China

The anthropogenic phosphorus (P) scarcity and the negative ecological effects of P induced eutrophication and pollution, mainly caused by the growth of population and economics as well as being aggravated by the inefficient... [ view full abstract ]

The anthropogenic phosphorus (P) scarcity and the negative ecological effects of P induced eutrophication and pollution, mainly caused by the growth of population and economics as well as being aggravated by the inefficient use of P from mine to field to fork in developing countries, call for substantial reduction in demand through efficiency and recycling. Using substance flow analysis (SFA), dozens of mass balance models were constructed, and then flow charts were drawn to systematically present P flows in Zhangzhou prefecture of Fujian province in China from 1995 to 2014. The charts were used to identify where P use efficiency can be improved, and understand the changes of resource demand and environmental load of P metabolism for policy-making related to the improvement on its metabolism efficiency and recycling. SFA results showed that there are significant different on the increase of annual P input to the three agricultural production subsystems, i.e. 0.64×10⁴ t P and 20% for crop farming mainly contributed by fertilizers, 679 t P and 15% for livestock, and 2.54×10⁴ t P and 325% for aquaculture in the 20 years, respectively. While, total input amount of the whole system increased 1.73 times from 4.42×10⁴ t P in 1995 to 7.67×10⁴ t P in 2014, mainly contributed from crop farming and aquaculture in each year. Accordingly, since 1995, the increased amount of annual net P loss to the environment from the three subsystems was up to 0.6×10⁴ t P, 783 t P, and 2.32×10⁴ t P in 2014 respectively, with the increase rates of 31%, 8487%, and 325% successively. Thereby, the increase of annual P demand and its net loss from aquaculture were much higher than those for the other two subsystems. This indicated that it was much more urgent to improve P use efficiencies of aquaculture subsystem, without overlooking the importance of improving P use efficiencies in crop farming for the reduction of anthropogenic P demand in the prefecture, compared with other subsystems. In food consumption subsystem, annual food P consumption significantly increased 236% (559 t P yr^-1) by urban residents and slightly reduced 6.76% (116 t P yr^-1) by rural residents from 1995 to 2014. Accordingly, per capita food P footprint increased 70% for urban residents and decreased 3.85% for rural residents within the 20 years. As a result, net environmental P load increased 17% (183 t P yr^-1) from rural residents’ excreta and 114% (374 t P yr^-1) from urban residents’ excreta in the 20 years, respectively. Therefore, urbanization was one of the dominant driving factors on exacerbating environmental load and resource shortage of P metabolism, and should be considered in policy-making related to improve P metabolism efficiency and recycling. But, the effect of urbanization on P loss was mainly  changed by residents’ food consumption pattern rather than discharging wastewater, WWTPs can play little role in reducing P load of the whole system as most of P loss occurred during agricultural production.