Effect of inorganic matter on pyrolysis and gas formation rates of palm empty fruit bunch and eucalyptus bark using TG–MS

Palm empty fruit bunch (EFB) and eucalyptus bark (EB) were leached with room-temperature water, hot water, or hydrochloric acid (HCl) to remove inorganics, then characterized for ash/elemental content and pyrolysis behavior using thermogravimetric analysis (TGA) and thermogravimetric analysis–mass spectrometry (TG–MS). Potassium dominated in EFB, while calcium was predominant in EB. Water removed alkali metals but not alkaline earths; HCl removed both (80%–99%). Leaching shifted the main weight loss of EFB to higher temperatures by 20 °C–30 °C, confirming that K catalyses early degradation and promotes char formation. For EB, Ca removal accelerated devolatilization. Gas evolution during pyrolysis decreased after HCl leaching (CO2, CO, H2O), whereas the liquid yield increased markedly: for EFB, it ranged from 24.5 to 40.9 g/100 g raw, and for EB, it ranged from 18.9 to 25.4 g/100 g raw. Overall, selective removal of inorganic species explains the distinct pyrolysis pathways of these biomasses and offers a practical way to improve liquid production.