Investigation of Properties of Liquid and Solid Fractions of Hydrochars Produced from Apple Wood Wastes at Different Temperatures and Times of Hydrothermal Carbonization

Hydrochar is a carbonaceous solid material obtained from hydrothermal carbonization (HTC) of biomass and has received more attention as a potential agent for soil contaminants stabilization and soil improvement. Physical and chemical properties of hydrochar are affected by the feedstock nature and production processes (HTC temperature and reaction time). The aim of this work was investigation of some properties of hydrochars produced from apple pruning wastes at temperatures of 180, 200, and 220 °C and 6, 9, and 12 h reaction times. In addition, the effect of the hydrochar produced at 180 °C and 12 h on availability of some nutrients in soil and corn growth was investigated. The results showed that pH of solid and liquid fractions of hydrochars were in the range of 5.7-6.9 and 3.5-4.1, respectively. By increasing conversion temperature and reaction time, the hydrochar yield and the pH of the liquid fraction were decreased, but pH and concentrations of P, Ca, Mg, and ash of solid fraction and concentrations of N, P, Ca, Mg, Fe, Mn, Cu and Zn and EC of liquid fraction were increased. Findings from this work suggested that HTC at higher temperatures increased elements concentrations in both solid and liquid fractions, and may be useful for agricultural aims. The results of the greenhouse experiment showed that hydrochar increased the availability of P added to the soil and the corn P uptake.