Hazardous air pollutants and volatile organic compounds emitted during kiln drying of southern pine lumber to interior and export moisture specifications.

摘要

The emission levels of hazardous air pollutants (HAPs) from wood kilns are needed to comply with the Clean Air Act. Softwood lumber, including southern pine (Pinus taeda, Pinus palustris, Pinus echinata, and Pinus elliottii), is considered kiln dry when the wood moisture content reaches below 19 percent, but it is sometimes overdried or dried to 8 percent moisture content for export or interior applications. To study HAP emissions when drying to 8 percent moisture content, green lumber was obtained from a local mill, and 12 charges were kiln dried using three schedules: a 99 degrees C elevated schedule and 116 degrees C and 127 degrees C high-temperature schedules. Methanol and formaldehyde were collected and analyzed using the National Council for Air and Stream Improvement (NCASI) 98.01 method, "Chilled Impinger Method for Use at Wood Products Mills to Measure Formaldehyde, Methanol, and Phenol," where formaldehyde was analyzed via spectrophotometry using acetylacetone and methanol was analyzed via gas chromatography with a flame ionization detector. The high-temperature schedules had significantly greater HAP emissions than the elevated schedule. When drying from 19 to 8 percent moisture content, methanol and formaldehyde emissions increased by an average of 48 and 52 percent, respectively. Volatile organic compounds (VOCs) were also measured using a flame ionization detector by the NCASI VOC method with results similar to previous studies. The methanol, formaldehyde, and total volatile organic emissions were reported according to the Environmental Protection Agency OTM-26 method, "Interim VOC Measurement Protocol for the Wood Products Industry." The results were slightly higher than the NCASI VOC results because of more accurate quantification of methanol.