Comprehensive evaluation of product characteristics and energy consumption in hydrothermal carbonization of food waste anaerobic digestate: A perspective on phosphorus recovery and fuel properties

Food waste digestate (FWD) is rich in organic matter and phosphorus(P) elements, making it a potential source for energy and P recovery. Hydrothermal carbonization (HTC) addresses FWD's dehydration and stability issues, improving hydrochar's fuel properties and P recovery in hydrothermal liquid. Experiments with various additives reveals 1M HCl's effectiveness, increasing P recovery by 88.31 % at 120 degrees C, decreasing hydrochar ash content by 21.42 %, and raising heating value by 45.01 %. Principal component analysis highlights the viability of acid treatment for P leaching and hydrochar enhancement, with pH as a crucial factor. HTC substantially reduces energy consumption by 57.42 % compared to direct drying. Hydrochar without additives shows potential as slow-release P fertilizers, with a 28.8 % increase in total phosphorus at 240 degrees C, where 99.4 % of P exists as apatite inorganic. Soil tests reveal differences with formic acid method in P availability, showing varying correlations with different P forms. This research offers insights for FWD resource utilization.