Monoterpenes in Scots Pine and Norway Spruce and their Emission during Kiln Drying

Abstract

Summary Scots pine (Pinus silvestris) and Norway spruce (Picea abies) were dried in a laboratory kiln, using conventional schedules with temperatures up to 60°C as well as schedules reaching 110°C. The losses of terpenes, which completely dominate the fugitive emissions from kiln drying of softwoods, were estimated by extraction of pooled subsamples from each batch, before and after drying. The original contents of terpenes were found to be in the ranges of 0.4–0.5% in pine sapwood, 0.8–1.1% in pine heartwood, and 0.02–0.08% in spruce, all calculated relative to the dry weight of the wood. The emissions from pine corresponded to 25–50% of the original content and those from spruce to 10–50%. High temperature drying in the laboratory was accompanied by larger losses, but this tendency was not found in the full-scale drying of spruce. No consistent difference was found between timber from the north of Sweden and from the south. Sampling of the vent exhaust fumes did not give results of sufficient reliability to confirm the extraction analyses.