Challenges and solutions for nutrient efficiency and waste valorization in the island agri-food system in Taiwan

Sustainable nutrient management remains a critical challenge for agri-food systems worldwide, particularly in resource-constrained island regions. Excessive nitrogen (N) and phosphorus (P) losses, driven by reliance on imported fertilizers and feed and inefficient waste management, contribute to eutrophication, greenhouse gas emissions, and soil degradation. These environmental burdens undermine the resilience and sustainability of food systems. This study employed material flow analysis (MFA) to evaluate nutrient flows and losses in Taiwan, a densely populated island that is highly dependent on external nutrient inputs. Results indicate annual inflows of 358.6 kt N and 118.3 kt P, of which 84% of N and 48% of P are lost, primarily through domestic and industrial wastewater discharge and manure mismanagement. Scenario-based assessments demonstrate that enhanced biowaste recycling, including livestock manure, food waste, and wastewater, could reduce fertilizer imports and mitigate greenhouse gas emissions by up to 98,299 tons CO2 eq annually. Although some progress has been made in municipal wastewater valorization, broader implementation of nutrient recovery strategies remains limited. The findings underscore the need for integrated policy frameworks and cross-sectoral collaboration to enhance nutrient circularity, reduce environmental pressures, and support cleaner food production in island settings. This study provides a comprehensive systems-level assessment of nutrient use inefficiencies and recovery opportunities, offering actionable insights for decision-makers and environmental planners. The approach and findings are relevant for developing science-based policies to improve sustainability in vulnerable agri-food systems globally.