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### "Gold Born from Water"—Recovery of Yellow Phosphorus from Sewage Sludge (NKK) NKK (now JFE Steel) collaborated with Nippon Chemical Industrial to develop technology for recovering high-purity yellow phosphorus from sewage sludge. This technology utilizes a high-temperature melting furnace to convert incinerated sewage sludge ash into molten slag, enabling phosphorus recovery. This method is attracting attention as a way to reduce dependence on conventional phosphorus resources and contribute to securing domestic phosphorus resources, with expectations for its introduction at sewage treatment facilities. ### Related Information (Current) The National Institute of Advanced Industrial Science and Technology (AIST) has developed a technology to recover phosphorus from sewage sludge incineration ash and produce phosphorus-based products such as flame retardants. This technology enables more effective resource utilization by chemically recycling the recovered crude phosphoric
acid. Tohoku University and Sumitomo Corporation are conducting demonstration experiments to recover phosphoric acid from unused phosphorus resources such as slag, waste acid, and sewage sludge incineration ash, and to produce yellow phosphorus. The primary goal is to establish stable domestic production technology for yellow phosphorus, particularly for use as a semiconductor raw material.

Hokkaido University has developed technology to efficiently and selectively separate and recover phosphorus from sources like sewage sludge incineration ash. By combining chlorination and carbon reduction processes, phosphorus can be recovered in a higher purity form, contributing to improved resource circulation. ### Summary

Technologies for recovering yellow phosphorus from sewage sludge are currently being refined by various research institutions and companies. Amid concerns over phosphorus resource depletion, establishing this technology is expected to enable its application across diverse fields, including agriculture and the semiconductor industry. Securing domestic phosphorus resources and advancing recycling technologies are hoped to further realize sustainable resource circulation in the future.