Potential of natural-origin loblolly pine tree fractions as a bioenergy feedstock
Chemical characterization was performed on 10 different samples of loblolly pine (Pinus taeda L.), representing the various woody components of trees (bole, slab, tops and branches, and precommercial stem-only) harvested from two naturally regenerated forests in southern Arkansas. Ultimate analysis, proximate analysis using thermogravimetry, and the energy content of the samples were determined to help evaluate their bioenergy utility. Elemental analysis revealed no significant differences between the pine tree fractions, whereas differences were observed in the proximate analysis, particularly in regard to the fixed carbon content. Generally, proximate analyses did not show significant differences between the slabwood and bolewood samples, although the “tops and branches” and “whole stem” samples contained the lowest volatile matter amounts and the greatest amounts of fixed carbon and ash content. In terms of the calorific value, the “tops and limbs” sample reported the lowest energy content, whereas the “whole stem” sample was among the highest reported value with statistical significance. These results indicate that whole stem samples may be an attractive prospect for bioenergy applications such as gasification, pelletization, and combustion, owing to favorable heating content values and relatively low ash content. Although a number of logistical challenges exist in their acquisition and processing, slabs, topwood, and branches offer opportunities for bioenergy applications that can increase the utilization of forest residues without threatening more traditional uses of wood in lumber, panels, and paper. Finally, we then briefly consider the silvicultural implications of these results for naturally regenerated southern pine–dominated forests.