Fertilizer potential of liquid product from hydrothermal treatment of swine manure

•Fertilizer potential of liquid product of swine manure after HTT was first evaluated.•98% of N in manure was converted to soluble form after HTT at 200 °C for 60 min.•GI over 100% was achieved using the liquid product from HTT at 150 °C for 60 min.•Heavy metal contents in liquid product were within the thresholds for plant growth. Compared with composting, hydrothermal treatment (HTT) technology can dramatically shorten the duration for manure waste treatment. This study firstly investigated the effect of HTT on solubilization of N, P and organics from swine manure, and then evaluated the phytotoxicity of liquid product from hydrothermally treated manure by seed germination test. Results show that 98% of N in manure could be converted into soluble form after HTT at 200 °C for 60 min. Soluble P in hydrothermally treated manure (at 150 °C for 60 min) was 2.7 times that in raw manure. The germination indices (GI) were all greater than 100% when the liquid product (from HTT at 150 °C for 60 min) or its diluted samples being used. Results from this study suggest that HTT could be a promising technology for producing safe and value-added liquid fertilizers from swine manure.