Production of combustible gas via incorporating CO<sub>2</sub> to pyrolysis of medicinal herbal waste

Abstract

With the recent increase in the utilization of medicinal herbs, the generation of medicinal herbal waste has increased. However, conventional protocols for solid waste management (landfill and incineration) present environmental threats considering the complex chemical composition of medicinal herbal waste. Thus, this study introduces a thermochemical approach for managing medicinal herbal waste, focusing on conversion of red ginseng marc (RGM) into energy resource. This study explores an innovative strategy to maximize the production of pyrogenic gases using CO2 form improved syngas generation. The experimental results revealed an enhancement in CO from the pyrolysis of RGM under the CO2 condition in reference with the N2 condition, which was ascribed to gas-phased homogeneous reaction of CO2 with volatile matters liberated from RGM. Moreover, gas-phase reactions have proven to be effective in decreasing the benzene analogs, especially polycyclic aromatic hydrocarbons (PAHs), in pyrogenic liquids. To accelerate the gas-phase reaction rate, a nickel (Ni)-based catalyst was employed for the RGM pyrolysis. The introduction of Ni catalyst to the gas-phase reaction led to an CO enhancement (272 %) from the RGM pyrolysis in the presence of CO2. All experimental observations highlight the potential of incorporating CO2 in thermochemical conversion of RGM as an innovative way to enhance energy recovery.