Thermal Analysis of St. John's Wort Wastes and Biochars: A Study of Combustion Characteristics and Kinetics

Since St. John's wort is used extensively in industries such as food, medicine and cosmetics, it is a type of biomass with a high waste potential. The utilization of these wastes is very important both to minimize environmental negativity and to provide an economic contribution. This study aimed to determine the potential of St. John's wort wastes and biochar forms produced from these wastes to be used as solid fuel. In this context, the combustion behavior of the biomass and biochar samples obtained were determined by thermogravimetric analysis method. In addition, combustion activation energies of these samples were calculated using Kissenger-Akahira-Sunosa and Flynn-Wall-Ozawa methods. According to the analysis, more than 90% of all samples were burned and the combustion activation energy values ranged between 70.08 and 203.86 kJ/mol. When all the results obtained are evaluated, it is understood that these biomass wastes and their biochars can be used in combustion systems as direct fuel or additive.