Thermal Decomposition and Combustion Characteristics of Pistachio Pruning Residues

Due to different reasons, such as the destructive effects of fossil fuel consumption, climate changes, global warming, and threats to human health, biomass is considered as alternate fuel. This biofuel is the most widespread source of renewable energy, and its scientific exploitation is increasing.  In this research, pistachio pruning residues including leaves and stems were separately used as a source for biomass and their combustion and heat characteristics were investigated. A TGA device was used for thermal analysis and the combustion properties including enthalpy of combustion, high heating value (HHV) and low heating value (LHV) were measured experimentally and by using regression equations. The amounts of cellulose, hemicellulose, and lignin in stem were 48%, 16%, and 15%, respectively, and the same materials for leaves were 35%, 19%, and 32%, respectively. The high calorific value was calculated using regression equations, which were calculated as 17.5 MJ/kg for stem and 14.5 MJ/kg for leaves. The results showed that the two methods for determining the HHV and LHV were in good agreement with each other. The TGA analysis of the samples showed that the thermal decomposition of stem and leaves starts at a temperature of about 220°C, but during the initial stage of decomposition, the decomposition rate for stem is more severe than the decomposition rate of leaves.