Comparative Thermochemical and Combustion Analysis of Biomass Pellets Derived from Woody and Agricultural Residues

This study presents a comparative thermochemical and combustion analysis of biomass pellets derived from softwood, hardwood, sunflower husks, wheat straw, and lavender residues. This investigation was performed using thermogravimetric analysis (TG), derivative thermogravimetric analysis (DTG), and differential scanning calorimetry (DSC) to evaluate the thermal degradation behavior, combustion reactivity, heat-release characteristics, and ash-forming tendencies of the investigated biomass types. The results revealed substantial differences between woody biomass and agricultural residues in terms of thermal stability, thermal degradation behavior, and energy output. Softwood pellets exhibited the highest thermal reactivity, the most intense devolatilization process, and the highest heat release during combustion, indicating higher thermal reactivity and favorable fuel properties. Hardwood pellets demonstrated improved thermal stability due to increased lignin content, resulting in broader thermal decomposition regions and more gradual heat release. In contrast, sunflower husk and wheat straw pellets showed lower thermal reactivity and significantly higher residual mass, indicating elevated ash content and reduced thermal decomposition behavior. Lavender pellets exhibited intermediate thermochemical behavior associated with the presence of volatile extractives and moderate thermal stability. The integrated TG-DTG-DSC approach enabled a direct comparison of woody biomass and agricultural residues under identical experimental conditions and expanded the available thermochemical data for lavender-derived pellets. The results provide a comparative framework for assessing biomass resources intended for energy applications.