<![CDATA[This study aims to determine the effect of variations in HTC operating parameters (temperature, time, and biomass-to-water ratio) using a pressure cooker on the physicochemical characteristics of the resulting hydrochar. The hydrothermal carbonization process was conducted at the Laboratory of the Chemical Engineering Department, Politeknik Negeri Lhokseumawe, with a fixed distilled water volume of 200 mL at a pressure of 1.5 bar. The independent variables studied included variations in coffee silverskin mass (20 g, 30 g, and 40 g), operating temperature (200°C, 250°C, and 300°C), and contact/residence time (3 hours, 4 hours, and 5 hours). Characterization of the hydrochar was carried out through moisture content testing, mass yield recovery, Higher Heating Value (HHV), energy recovery, and functional group identification using Fourier-Transform Infrared Spectroscopy (FTIR). Based on the research data, an increase in temperature and residence time generally caused a decrease in hydrochar mass yield but increased the degree of carbonization. The highest heating value was achieved at an operating temperature of 250°C for 4 hours with a coffee silverskin weight of 20 g and 200 mL of distilled water, which produced a heating value of 18,865 J/g with an energy recovery reaching 89.10% and a moisture content of 3.5%. FTIR analysis of the solid product confirmed changes in the chemical structure, marked by the appearance of absorption peaks for hydroxyl groups (-OH), aliphatic C-H stretching vibrations, and aromatic carbon double bonds (C=C), indicating the formation of a stable charcoal structure. The use of a pressure cooker proved to be potentially effective as an economical laboratory-scale hydrothermal carbonization reactor medium. The best hydrochar characteristics approaching the properties of solid fuel were obtained at a temperature of 230–250°C with an operating time of 4 hours and a 1:10 ratio. The results of this study provide an alternative solution for utilizing coffee silverskin waste into a value-added biomass energy source.Keywords: Coffee silverskin, Hydrochar, mass yield, heating value, FTIR]]>
Copyrights © 2026
