Legacy phosphorus mobilization and waste recovery technologies for agricultural sustainability

Efficient phosphorus (P) management is critical for global food security yet current practices rely on a linear model that leaves significant portions of applied fertilizer immobilized as legacy P in soils or lost to the environment. This review establishes an integrated framework to transition toward a circular P economy (CPE) by synthesizing advances in soil biogeochemistry, recovery engineering, and nutrient governance. A systematic diagnostic protocol utilizing chemical fractionation, physical characterization, and biological assessment is proposed to identify dominant soil P retention mechanisms and guide site-specific interventions. Biological mobilization strategies such as organic acid production, siderophore mediated iron P decoupling, and enzymatic mineralization provide pathways to unlock recalcitrant soil P forms. Simultaneously, recovery technologies including thermochemical processes, precipitation methods, and membrane separation are evaluated for their capacity to produce agronomically functional products from waste streams. An integrated decision matrix links diagnostic characterization to mechanism-specific mobilization and compatible recovered products, thereby operationalizing circularity at the field level. Successful implementation requires aligning recovered product selection with regional soil chemistry to maximize impact and minimize re-fixation. By bridging disciplinary fragmentation, this review provides an actionable systems-oriented framework for a CPE that not only secures P resilience by reducing reliance on finite mineral reserves, but also mitigates the environmental degradation associated with nutrient runoff to ensure long term agricultural and economic sustainability.