Volatile Organic Compounds Emitted during the Kiln Drying of Southern Pine Utility Poles

Abstract

Southern pine is the most common species used for utility poles in the United States. However, information regarding air emissions from pole drying is very limited. With respect to drying, poles have longer lengths, resulting in limited end-grain exposure, higher final moisture content, and lower ratios of surface area to volume, and typically southern pine poles have higher amounts of heartwood compared with southern pine lumber because of pole age. For this research, several green southern pine utility pole bolts were obtained and cut into matched kiln charges that contained sapwood only, mostly sapwood, mostly heartwood, and knotty material. Eight charges were dried at 230°F dry bulb with at least a 50°F wet bulb depression until the poles reached a moisture content of 30 percent at a depth 3 inches from the surface. Volatile organic emissions from the kiln charges were measured using federal guidelines. The mean emission values from the all sapwood, mostly sapwood, mostly heartwood, and knotty wood kiln charges were 3.59, 3.52, 2.64, and 3.65 pounds of volatile organic emissions per thousand board feet, respectively. The emissions of the sapwood, mostly sapwood, and knotty charges were similar to clear lumber emission values. The emissions from the knotty charges were less than emissions from knotty lumber. The results suggest that heartwood-rich utility poles release much less organic emissions than heartwood lumber, perhaps because of the band of sapwood that always surrounds the heartwood in poles as opposed to lumber where the heartwood is often exposed at the surface.