Sustainable Phosphorus Recycling: A review of advanced recovery methods with a focus on hydrothermal humification technology and potential phosphorus resources in China for this method

The management of phosphorus (P) resources is facing dual challenges mediated by human activities: the scarcity of bioavailable P in soil and the disposal of massive undeveloped P resources in waste streams. In China, large amounts of P resources remain unexploited, including crop straw (0.9 Tg/year), pig manure (1.1 Tg/year), sludges (0.2 Tg/year), feces (0.5 Tg/year), as well as outbreaking algae (0.48 Tg/yr). Traditional P recovery technologies, including precipitation, acidulation and thermochemistry technology (PAT) and enhanced biological phosphorus removal technology (EBPR), have shown limitations in P recovery from these biomass waste streams. Hydrothermal humification technology (HTH) is a promising new technology, capable of converting typical waste streams into phosphate fertilizer for green and sustainable development. We estimate that the amount of available P that HTH could potentially extract from straw, macroalgae waste and sludge totals 0.46 Tg/year. Accordingly, the consistent development of HTH for the recycling of waste P in biomass will effectively improve China's P cycle and relieve the absence of phosphate rocks sources and environment pollution.