Environment-food nexus in trout ponds: a developed index by combining grey water footprint and life cycle assessment

Fish ponds are reliable food supply in local scale. However, they have adverse environmental impacts due to discharging pollution to the surface waters. To quantify the sustainability of this industry with the perspective of environment-food nexus, the-state-of-the-art index of food environmental footprint (FEF) is used and calculated for trout ponds (TPs). For this purpose, an integrated method is developed for accounting the environmental impacts of TPs by including grey water footprint (GWF) in Recipe, a tool for life cycle impact assessment (LCIA). GWF stands for the embedded water consumption and LCIA combines the potential health and ecological impacts. Here, water quality data of multiple pollutants, BOD, COD, TSS, NO₂, NO₃, NH₄, TN, PO₄, DO and Cu⁺², in the influent and effluent of Iranian TPs was obtained by field experiments and discussed with data from 9 countries. Results showed that TSS and NH₄ are critical pollutants and the average GWF is about 16 m³/kg. Moreover, human health impacts are relatively greater than ecological damages. Nevertheless, FEF is calculated 0.17 and verifies TP sustainability (< 1). Based on environment-food nexus perspective; it means that the positive value of food production dominates TPs’ negative environmental damages. In addition, this study reviewed the efficiency of constructed wetlands for low-strength wastewater treatment. Due to its potential on TSS and NH₄ removal, this system can reduce the GWF and added environmental damages of TPs 85% and 58%, respectively. Consequently, FEF decreases to 0.023 showing the very sustainability (< 0.1) of TPs by wastewater treatment.

Graphical abstract