24th Pacific Science Congress (PSC-24)

Phosphorus is an essential but non-renewable resource. Japan, lacking domestic phosphate rock, faces high supply vulnerability. While the nation generates substantial phosphorus-rich sewage sludge and has long investigated recovery technologies, full-scale implementation remains limited, leaving most sludge incinerated and landfilled. In response to the government’s 2030 target to enhance phosphorus recovery and secure domestic food production amid increasing global supply disturbance, a comprehensive evaluation of recovery scalability is urgently needed. To this end, we conducted a techno-economic assessment of practical recovery potential from sewage sludge using data from ~2,600 wastewater treatment plants. The analysis examined key recovery routes—precipitation/crystallization of Magnesium Ammonium Phosphate (MAP) and Hydroxyapatite (HAP), and ash-based extraction (leaching/melting)—by integrating their technical feasibility, economic performance.
Our analysis estimated that in 2020, about 67.4 kt of phosphorus entered Japan’s wastewater systems. With regional removal efficiencies of 73–89%, approximately 53.5 kt was retained in sludge—equivalent to a theoretical recovery potential of 41% of the nation’s annual agricultural demand. When economic and engineering constraints were considered, this potential declined to 15% (P1: decentralized MAP + HAP route) and 30% (P2: centralized ash-based route). Among all options, the P3 pathway using ash leaching proved the most cost-effective, comparable to conventional phosphate fertilizers, though regional self-sufficiency still varied widely. Overall, these findings provide a data-driven basis for optimizing phosphorus recovery pathways, guiding product allocation, and promoting cross-regional phosphorus circulation.
 

Phosphorus recovery, technological route, sewage sludge