Two hardwood species, namely red oak and yellow-poplar, were separated into their bark, sapwood and heartwood components. The samples were tested for calorific value, specific gravity, proximate analysis, mineral composition, chemical composition, ultimate analysis, and thermo-chemical decomposition behavior. In addition, the thermo-chemical decomposition behaviors of cellulose, xylan, and lignin polymers were also tested. Thermo-chemical decomposition behavior was assessed using a thermo-gravimetric (TGA) system by heating the sample from 50 °C to 700 °C at the heating rates of 10, 30 and 50 °C/min under nitrogen. The activation energy was calculated for various fractional conversion values using the isoconversion method. The results showed that char yields of lignin, cellulose and xylan were 41.43%, 4.45% and 1.89%, respectively, at the end of pyrolysis. Furthermore, cellulose, xylan and lignin decomposed dramatically in the temperature range of 320 °C to 360 °C, 150 °C to 230 °C and 100 °C to 410 °C, respectively, with decomposition peaks occurring at 340 °C, 200 °C and 340 °C, respectively. In addition, the maximum activation energy for cellulose was 381 kJ/mol at 360 °C and for xylan it was 348 kJ/mol at 210 °C.