Wood processing as a source of terpene emissions compared to natural sources

Abstract

The aim of this paper is to analyse the importance of terpene emissions from forestry and the wood industry and relate these anthropogenic emissions to the natural terpene emissions from undisturbed forests. Biogenic volatile organic compounds are emitted naturally from trees and other plants. Boreal forests are dominated by terpene-emitting tree species. Anthropogenic terpene emissions occur due to drying, machining and tooling of wood. This is a cause of concern with regulatory authorities faced with expanding production of biofuels, e.g. wood pellets. Anthropogenic terpene emissions are of current importance as the use of biofuels has increased considerably over the recent years. The most important environmental effects of terpene emissions are due to the formation of photo-oxidants and atmospheric aerosols. Photo-oxidants cause forest and crop damage, and are harmful to humans. Carbonaceous aerosols have an impact on climate change. Furthermore, most sesquiterpenes are used in the chemical communication systems of various insects. There are also issues concerning the working environment in the wood industry. Environmental effects of terpene emissions are analysed with focus on three key aspects: the total amount of emissions, the concentration in air and the types of terpenes emitted. The reported concentrations of monoterpenes are in most cases below the occupational exposure limits, with drum barking and pellets production from non-dried sawdust close to the limit. Anthropogenically emitted terpenes have a higher proportion of sesquiterpenes than naturally emitted terpenes have, especially when the processing of wood involves elevated temperatures.

Release of Terpenes from Fir Wood during Its Long-Term Use and in Thermal Treatment

“…Most terpenes were thus released during the first years of fir beam exposure in buildings, while later the rate of release decreased and their total amount in beams approached the limit value of 3 mg/kg (Sample A). Resulting values are similar to those found by Granström [ 33 , 34 ] and Rupar, Sanati [ 15 ] during the storage of fir wood chips at various levels of moisture content.…”

“…The wood of coniferous trees contains approximately 0.1%–0.6% of terpenes. In needles, approximately five times higher concentrations were found compared to wood [ 3 , 33 , 34 ]. The rate of release of terpenes from harvested wood depends on the size of samples, moisture content, temperature, the manner of further processing and the course of exposure.…”

Tree water relations can trigger monoterpene emissions from Scots pine stems during spring recovery

“…Surprisingly, despite abundant knowledge on emissions of volatile isoprenoids from foliage, very little is known about their emissions from woody plant tissue. From the viewpoint of the timber and paper industry, isoprenoid emissions from harvested and further-processed timber have been previously reported Petersson, 1991, 1993;Granström, 2007), but living woody tree parts have gained only little attention. As the oleoresin storage pools in stems are large, emissions occur constitutively without any damage to the tree itself, but their seasonal patterns or driving factors have not been studied in detail.…”

Method Comparison for the Identification and Characterization of Odorants from Scots Pine (Pinus sylvestris L.) and Oriented Strand Boards (OSB) Made Thereof by GC-MS and GC-FID/O Using Different Headspace Techniques

“…The autooxidation of fatty acids, or enzymatic peroxidation, produces various volatile aliphatic saturated and unsaturated aldehydes [11,12]. Terpene emissions, on the other hand, derive directly from fresh wood, where they are present in resinous channels, primarily in softwoods, that extend between heart-and sapwood [13]. The biosynthesis of terpenes is started by a condensation reaction of two molecules of acetyl coenzyme A, where the compound acetoacetyl-coenzyme A is produced [14].…”