A Study on the Application of Coffee Waste Biochar with Hydrothermal Carbonization and Adsorption Performance of Heavy Metal

Coffee drinks are one of the most popular beverages around the world, and coffee beans are grown in about 80 countries. In addition, the consumption of coffee beans in Korea is about 150,000 tons as of 2018, the world's sixth largest, and the annual consumption of coffee per capita by people over 20 years old is about 353 cups, up 21 percent from 291 cups in 2015, which is about three times the consumption per capita of 132 cups by the world's population. However, despite the continued increase in coffee bean consumption, 99.8% of the coffee beans used remain as dregs, with the cost of handling them reaching 764.2 billion won a year, and environmental problems caused by CO₂ from the process cannot be ignored. Common coffee wastes have the advantage of high moisture content and high absorbency due to porous surface. Here, hydrothermal carbonization (HTC) is one of the thermal treatment methods and is a method of carbonation using temperatures of 180 ~ 300^oC and high pressure in a closed environment with limited oxygen. Unlike other pyrolysis methods, thermo-degradation methods have the advantage of cost-benefit that does not require pre-treatment of dryness because they conduct at a relatively low temperature and use water vapor pressure caused by evaporating moisture in the raw material itself. Therefore, it is suitable to recycle coffee wastes effectively using thermal water pressure carbonation reaction. We also want to evaluate the performance of adsorption by generating Activated Biochar through chemical activation as a method of utilizing Biochar produced after HTC reaction. Therefore, in this study, the optimum generation conditions of Biochar are derived by applying HTC method, which is suitable for utilizing the high moisture content and porous properties for recycling coffee wastes, and after deriving the optimal generation conditions for chemical activation of the Biochar produced, PAC(Powdered Activated Carbon) is compared with the characteristics analysis of coffee wastes and Biochar and Activated Biochar to check and evaluate the absorption performance of heavy metals.