Content area
Full Text
ABSTRACT
This project investigated the influence of the end grain on volatile organic compound (VOC) emissions. Two lumber lengths and two end conditions were used to evaluate the end effect. The influence of season of harvesting and processing on VOC emissions was also investigated. End effect was not found to be statistically significant. Seasonal influence, however, was found to be statistically significant with respect to VOC emissions. This seasonal influence is different from that noted in earlier work (8,9). This difference suggests the need for additional study regarding the influence of processing season on VOC emissions.
Free water migrates out of wood at least 10 to 15 times faster via the end grain versus the radial or tangential surfaces (5,6) at room temperature. At higher temperatures, however, longitudinal flow probably does not play such an important role. In a previous study of the end effect in kiln-drying, it was reported that the end effect extends only a short distance (50 to 100 mm) from the ends of the boards (12). That study used red oak lumber, which is considered relatively "impermeable" with respect to drying. By contrast, pine lumber is considered relatively permeable (along the radial and tangential axes) with respect to drying (4). Therefore, the end effect of pine with respect to drying, and perhaps emissions, would be expected to be less than that of the oak in Wengert's study ( 12).
Loblolly pine contains many volatile organic compounds (VOCs). These VOCs are given off during drying of pine lumber. The hydrocarbon VOCs given off during wood drying are smog precursors; consequently, the U.S. Environmental Protection Agency is regulating industrial VOC emissions under the Clean Air Act Amendments of 1990 (1). This regulation has an economic impact on the forest products industry in general and particularly on the drying of southern yellow pine (1). The purpose of this research was to investigate the effect of lumber end grain on VOC emissions during pine lumber kiln-drying.
In this study, P. taeda (loblolly pine) lumber was dried in an experimental pilot kiln at the Mississippi Forest Products Laboratory, Mississippi State University, Miss. This experiment investigated the possibility that VOCs are emitted preferentially out of the endgrain (transverse) surface, in which case shorter pieces would produce...