Variation of terpenes in sapwood and heartwood of loblolly pine: Impact on VOC emissions from drying lumber samples

A single loblolly pine tree approximately 45 years in age was harvested for use in this study. Increment core samples from throughout the length of the tree bole were analyzed for terpenes. Lumber samples from different locations within the tree were tested for volatile organic compound (VOC) emissions in a pilot-scale kiln. The concentration of terpenes was also determined in samples from lumber before and after drying. Analysis of terpenes in increment cores gave concentrations of terpenes in heartwood, inner sapwood, and outer sapwood of 1.1 (0.068), 0.29 (0.061) and 0.11 (0.11) percent on a dry weight basis, respectively (standard deviations are shown in parentheses). The measured VOC emissions from heartwood and sapwood lumber samples were 6.21 and 3.27 pounds per dry ton as carbon, respectively. Approximately 50 to 60 percent of total terpenes remained in the lumber samples after drying both heartwood and sapwood samples. The increased VOC emissions from drying lumber sawn from heartwood was due to the higher initial concentrations of terpenes in the heartwood tissue of the loblolly pine. Due to the potential for volatile organic compound (VOC) emissions from dry kilns to enhance ozone formation and the Environmental Protection Agency (EPA) permitting requirements for old and new kilns, considerable research related to VOC emissions from drying lumber has been reported in recent literature. The monoterpene portion of oleoresin was identified as the major chemical component in VOC emissions from laboratory-scale kilns drying loblolly pine (Pinus taeda) lumber samples (Punsuvon 1994, Ingram et al. 2000b). The observation of -pinene, camphene, -pinene, myrcene, limonene, and 4-allylanisole as the major chemical components in VOC emissions was consistent with the composition of volatile terpenes reported by Drew and Pylant (1966). These compounds were identified as the major components in turpentine from loblolly pine chips with a measured laboratory yield of 1.0 gal/dry ton (or approximately 7 lb/dry ton). Studies on the distribution of oleoresin components in the bole of radiata pine (Pinus radiata) showed that the highest concentrations occurred in the heartwood near the bottom of the tree and decreased toward the top of the stem (Kininmonth and Whitehouse 1991). The concentration of extractable material was higher in the heartwood than in the sapwood. The composition of the terpenes was very similar to that of southern pine with -pinene and -pinene occurring as the major components. The total concentration of terpenes in sapwood, heartwood, and knot tissue from loblolly pine samples was found to be 0.31, 1.51, and 3.31 percent on an ovendry basis (Ingram et al. 2000a). The VOC emissions from samples of lumber that were sorted to contain a high occurrence of knots was 4.24 pounds per ton as carbon (lbC/ton) on an ovendry basis. Clear sapwood samples from the same tree gave emission values of 2.86 lbC/dry ton. In that study, there was a tendency for knotty lumber samples to give higher emissions of VOC than clear samples; however, the number of samples was too small for statistical comparison. In studies of full-size kilns, Dallons et al. (1993) measured the amount of VOCs in samples of southern yellow pine lumber before and after drying and reported an emission factor of 2 lbC/thousand board feet (MBF) of lumber. Glass and Elam (1995) reported emission values of 1.7 and 1.4 lbC/MBF of The authors are, respectively, Former Graduate Student (currently employed by Novartis Pharmaceuticals Co.) and Professor, Forest Products Lab., Mississippi State Univ., Mississippi State, MS ([email protected]). This paper was received for publication in February 2005. Article No. 10015. ✳Forest Products Society Member. ©Forest Products Society 2006. Forest Prod. J. 56(9):80-83.