Influences of Hydrothermal Carbonization on Phosphorus Availability of Swine Manure-Derived Hydrochar: Insights into Reaction Time and Temperature

The utilization of biomass waste, like that of swine manure, to produce hydrochar is a promising means whereby improvements in carbon neutralization, phosphorus (P) recyclization, and crop growth could be achieved. However, there is little information that can be found regarding the topic of swine manure-derived hydrochar (SMHC) P availability for crop growth use alone, making it essential to study SMHC P availability fluctuation under different hydrothermal carbonization (HTC) conditions. This research investigates SMHC P availability under varying HTC reaction temperatures and times. In which contents like those of Hedley P fractionation, total P in NaHCO3 extract solution, and Olsen-P, are examined under different hydrothermal conditions. Wherein increases in HTC reaction temperatures and times were observed to have brought about decreased trends in solid yields, the pH of SMHC, the content of water-soluble P, the amount of P absorbed on the surface of SMHC, the total P contents of NaHCO3 extract solution, and in the content of Olsen-P. Whereas increased trends were observed in the contents of Fe/Al-P and Ca-P in SMHC, likewise under the aforementioned increases in HTC reaction temperatures and times. This research aims to develop better understandings in hydrochar P availability fluctuation under different HTC reaction conditions, making it a good guide for lessening the environmental impact of swine manure and improving P recyclization for agricultural use.