Phosphorus is a finite resource essential to global food security, yet many import-dependent regions face increasing supply risks from concentrated reserves and geopolitical disruption. While municipal wastewater sludge offers a promising domestic secondary source of phosphorus, large-scale recovery remains limited by uncertainty over practical yields under real-world engineering and economic constraints. Previous assessments have often relied on aggregated data that obscure facility-specific conditions, leaving recoverable potential poorly constrained and potentially overstated. Here we developed an integrated facility-level framework connecting treatment scale, process configuration, phosphorus speciation, costs and spatial distribution, and applied it to a nationwide dataset for Japan. Results showed that engineering constraints reduced theoretical recovery by 34–63%, yet an integrated pathway combining decentralized aqueous-phase recovery with centralized ash leaching could still make a substantial contribution to the national target of agricultural phosphorus supply. Realizing this potential requires targeted incentives to address pronounced cost heterogeneity across facilities and coordinated spatial redistribution of recovered products. By establishing constraint-integrated modeling approaches, this work provides a transferable basis for evaluating recovery pathways, prioritizing investment and designing implementation strategies in other import-dependent regions seeking to advance circular phosphorus economies.