Biomass is one of the main renewable energy sources and coupled with carbon dioxide adsorbent material, such as calcium oxide sorbent, it increases the biomass conversion efficiency during gasification. This study aims to investigate the thermal degradation behavior of biomass and biomass/sorbent blends. Thermal stability is the stability of the material to resist change in physical shape as its temperature change. The purpose of this study is to determine the thermal stability and the conversion efficiency of biomass and biomass with sorbent blends. Thermo gravimetric analysis (TGA) was employed to determine the thermal stability of biomass and sorbent mixtures of pine-wood, calcium oxide (CaO), and or magnesium oxide (MgO), which will ultimately determine the gasification characteristics of the blends. A mixture resulted in the highest thermal stability and conversion efficiency compared to others will be the one suitable for gasification.