Water and sludge resource planning for sustainable agriculture: An energy-water-food-waste nexus approach

The population rise and expected increase in global food demand will stress natural freshwater resources. It will also result in increased emissions if proper resource planning is not implemented and unconventional water and energy resources are not exploited. There is a need to assess the potential of these unconventional resources, such as wastewater and sludge in alleviating carbon emissions and water stress. This study aims to do so by assessing the use of treated wastewater and sludge for food production and optimizing their planning using a multi-objective optimization model embedded within an energy-water-food-waste nexus approach applied to a case study on the agricultural sector in the state of Qatar. It is demonstrated that the use of treated sewage effluent as a water resource can supply the fodder farms in Qatar with all their nitrogen fertilization requirements almost throughout the year. Furthermore, the use of both treated sewage effluent and sludge as a source of energy has the potential to reduce the carbon footprint and water stress level by 62 % and 57 %, respectively. It is thus recommended to include treated sewage effluent in the agricultural water budget and to suspend outdoor farming not only during the summer but also in the hot month of March, as the latter can result in an additional 7 % and 30 % reduction of carbon footprint compared to the base-scenario when the water stress level is set to 0 % and 75 %, respectively.