Resistance of smoked wood to subterranean and dry-wood termite attack

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Abstract

Specimens from Sengon (Paraserianthes falcataria), Sugi (Cryptomeria japonica), and Pulai (Alstonia sp.) trees were exposed for 3, 8, or 15 days to the smoke generated during Mangium wood (Acacia mangium) pyrolysis, and their resistance to termite biodeterioration was compared to that of polystyrene-treated or untreated woods. All treated-wood specimens were exposed to subterranean termites (Coptotermes curvignathus Holmgren) and dry-wood termites (Cryptotermes cynocephalus Light) under laboratory conditions. The results showed that: (1) All three untreated woods were classified as class V (or very poorly resistant) to subterranean termite attack. On the other hand untreated-wood specimens of Pulai and Sugi tree were classified as class IV (or poorly resistant) and specimens of Sengon tree as class III (or moderately resistant) to dry-wood termites, based on the national Indonesian standard; (2) for all three wood species, 3-day exposure to Mangium wood smoke increased their resistance to class I (or very resistant) to subterranean termite attack; and (3) smoke treatment for 3 days for Sengon and Pulai wood specimens, and 15 days for Sugi wood specimens was required to increase their resistance to dry-wood termite attack to class I, which is the resistance level characterizing polystyrene-treated woods for all three species.

Highlights

► Three woods from plantation had low resistant to subterranean and dry-wood termites. ► The woods were smoked, and compared to polystyrene and untreated woods. ► Smoked for 3 days resulted highest resistant class to subterranean termite attack. ► Smoke for 15 days resulted highest resistant class to dry-wood termite attack. ► Smoked woods had the same resistance classes with polystyrene woods

Introduction

Indonesian log production in 2009 reached 32 million m3 and 77% of it was supplied from plantation forests, which play a crucial role in planning the renewable resource management. Approximately 4.3 million hectares of fast-growing species have been developed, among which are included Mangium (Acacia mangium), Sengon (Paraserianthes falcataria), and Pulai (Alstonia sp.) trees (Ministry of Forestry, 2010). A large proportion of wood logs harvested from plantation forests are produced from juvenile wood specimens, which are inferior in physical and mechanical properties as well as in biodeterioration resistance when compared to mature wood. In Indonesia, economic losses resulting from deterioration of buildings by termite attack were estimated at U.S. $200–300 million in 2000 (Yoshimura and Tsunoda, 2005). It is expected that this value will increase in the future if wood logs prepared from juvenile wood specimens are not treated to increase their resistance prior to their use as building materials.

Wood log treatment with polystyrene or with plastic has been proposed to extend their service life because the resulting product is more resistant to biodeterioration and safe to living organisms. Hadi et al., 2002, Hadi et al., 2003 have proposed impregnating pine (Pinus merkusii) wood, Sengon wood, and rubber wood (Hevea brasiliensis) with monostyrene and polymerizing it through a heat treatment (at 60 °C) for 24 h. They found this wood treatment increased the wood resistance to deterioration by Trametes versicolor (white-rot fungi), Tyromyces palustris (brown-rot fungi), subterranean termites, and marine borers. Devi et al. (2003) found that the polystyrene treatment also improves resistance to biodegradation.

Wood smoke contains a large number of polycyclic aromatic hydrocarbons, and it is composed principally of phenols, aldehydes, ketones, organic acids, alcohols, esters, hydrocarbons, and various heterocyclic compounds (Stołyhwo and Sikorski, 2005). Hadi et al. (2010) found wood specimens exposed to wood smoke were more resistant to subterranean and dry-wood termite attack than unexposed specimens, and a 12-h exposure time to smoke increased the resistance of Mindi (Melia azedarach) and Sugi woods (Cryptomeria japonica), whose resistance went up by one class with regard to the Indonesian standard. However, longer exposure periods are required to reach the highest class I (or very resistant) level of resistance.

The density of the fast-growing Mangium (Acacia) wood is on average about 0.51 g cm−3, ranging from 0.34 to 0.71 g cm−3 (Hadjib et al., 2007). This wood also contains vinegar consisting of acetic acid, methanol, phenol, o-creosol, furfural, and cyclohexane (Nurhayati et al., 2005). The smoke is a byproduct created during the pyrolysis process used to make charcoal, and while it has not yet been utilized for this purpose, it could potentially be useful to increase wood resistance to termite attack.

The purpose of this work was to determine the resistance of Sengon, Sugi, and Pulai wood specimens to subterranean and dry-wood termite attack when they were exposed for 3, 8, or 15 days to Mangium wood smoke. The resistance of the untreated and smoke-treated wood specimens was compared to that of polystyrene-treated specimens.

Section snippets

Wood specimens and wood treatments

Sengon and Pulai wood specimens from Indonesia, and Sugi wood specimens from Japan were assayed for their resistance to subterranean and dry-wood termite attack. Air-dried Mangium wood was pyrolyzed to produce charcoal, and the smoke generated as a byproduct was utilized to expose wood specimens to smoke for periods of 3, 8, or 15 days. Pyrolysis was performed in a metal drum with a capacity of 200 L, and the smoke produced during the process was collected into another drum prior to entering the

Results and discussion

The densities of Sengon, Sugi, and Pulai woods were, respectively, 0.29 g cm−3, 0.34 g cm−3, and 0.36 g cm−3, and polystyrene loadings were, respectively, 124.4%, 74.9%, and 61.1%. Sengon wood had the highest polymer loading, followed by Sugi and Pulai woods. This is consistent with the observation made by Hadjib et al. (2000) that the lower density wood specimens had a higher polymer loading.

Acknowledgments

We acknowledge the sponsorship of this research by the Ministry of National Education of Indonesia, through Competitive Research Grant XV; and are grateful to S. Hiziroglu of Oklahoma State University for his suggestions and improvements of the manuscript.

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