Upcycling of tobacco waste for solid-liquid co-production via hydrothermal treatment: Fuel application and fertilizer investigation

Based on global demand for agriculture sustainable development, the recycling of biomass residues, such as tobacco waste (TW) become increasingly urgent. Hydrothermal carbonization (HTC) effectively converts TW into valuable fuel and fertilizer from its solid phase (SP) and aqueous phase (AP). The higher heating value of SP220 increased significantly from 2.4 MJ/kg (TW) to 14.3 MJ/kg, indicating potential as a fuel substitute. The nutrient-rich AP220, with 1145 mg/L total nitrogen and 13.7 g/L total organic carbon, promoted Brassica napus growth, with a 40 % dilution (AP-40) yielding the highest biomass (10.3–32.1 g fresh weight) and antioxidant capacity (superoxide dismutase activity from 88.8 to 196.3 U/g). Field trials confirmed the practicality of AP, enhancing plant growth and soil ammonium nitrogen (43.17 mg/kg, three-fold higher than the control). This work achieves an upcycling value-added solid-liquid approach for TW, contributing to waste management and environmental sustainability by closing the loop in resource recycling. • HTC method was employed for solid-liquid upcycling of TW. • The SP220 exhibited fuel substitution potential (14.3 MJ/kg). • The release of dissolved organic matter during HTC enhanced the fertilizer efficiency of AP. • AP220 was rich in nitrogen (1145 mg/L) and total organic carbon (13.7 g/L). • Plant root development and antioxidant capacity were promoted by AP.