Economic implications of synergies and trade-offs in nutrient and water circular systems. A review in water-stressed agricultural contexts

Circular approaches to recovering water and nutrients from wastewater offer significant potential to alleviate both quantitative and qualitative water stress while providing valuable inputs for agriculture. We examine the synergies and trade-offs between water and nutrient circularity in water-stressed agricultural contexts, focusing on their economic implications. Results show that circular systems can deliver high-quality irrigation water, enhance soil fertility, and increase biomass yields, reducing reliance on synthetic fertilisers and freshwater. Nonetheless, trade-offs emerge from contamination risks, logistical complexity, and high capital and operational costs. Potential economic benefits include resilience to fluctuating input prices, reduced waste-management costs, and new revenue streams from recovered resources. Locally limited market access and technological constraints remain barriers to scalability. Water and nutrient circularity represent a promising pathway to support sustainable food systems and alleviate water stress, but enabling policies, improved governance, and context-specific investments are essential to ensure a coherent approach is adopted at scale.