Thermal Decomposition Behavior of Loblolly Pine Stemwood, Bark, and Limbs/Foliage Using TGA And DSC Techniques

Abstract. A standing tree before harvest has three primary components: bark, limbs/foliage, and stemwood. For a variety of reasons, most of the development work on forest biomass energy potential has used stemwood (also known as clean chips) as the feedstock. However, the amount of bark and limbs/foliage in a tree is significant (around 25% on mass basis) and may influence the economics of the forest-to-bioenergy process. In this study, the rate and kinetics of thermal decomposition of these three primary components were studied at heating rates of 5°C to 20°C min^-1 in both nitrogen and air atmospheres. The average mass fractions of the components were 74.6% stemwood, 18.2% limbs/foliage, and 7.2% bark. The stemwood component significantly had the lowest ash (0.32%, d.b.) and highest volatile matter (85.6%, d.b.) contents. Major loss in sample mass (40% to 60% of original mass depending on sample type) of each component occurred between 150°C and 425°C when the samples were thermally decomposed in nitrogen atmosphere. In air atmosphere, virtually all of the non-ash component of each sample was volatilized within the temperature range of 150°C to 600°C. The activation energies of stemwood were at least 20% lower than those of the low volatile matter content bark and limbs/foliage. The activation energies for the samples thermally decomposed in air atmosphere were higher than the corresponding values for nitrogen atmosphere.