Economic viability of eco-friendly wood treatment methods for small-scale sawmill operations

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Abstract

In Zambales Province, Philippines, a cooperative of 14 small-scale sawmills processing approximately 800 m³ of lumber per year recently shifted from creosote dip-treatment to untreated sales after the local supplier discontinued operations. Within two years, warranty claims for termite and fungal damage rose by 340%, threatening the cooperative's market position. Can eco-friendly alternatives restore the protective function that creosote provided—and can they do so at a cost that a small sawmill can absorb? This study addressed both questions through a paired laboratory-economics investigation. Five treatment methods—neem oil dip, neem bark extract pressure treatment, Khaya senegalensis bark extract dip, K. senegalensis pressure treatment, and cashew nut shell liquid (CNSL) dip—were compared against CCA pressure treatment and untreated controls on sapwood blocks of Parashorea malaanonan (bagtikan) and Shorea contorta (white lauan) over 16 weeks of accelerated fungal decay and 12-week forced-feeding termite bioassays. Simultaneously, a full cost model—covering raw material sourcing, extraction, treatment chemical preparation, equipment amortisation, labour, energy, and waste disposal—was constructed using 2022 Philippine market prices. K. senegalensis pressure treatment delivered the best biological protection among the eco-friendly methods (mean fungal weight loss 5.1%, termite mortality 92.7%) at a treatment cost of US$32.40/m³, compared with US$46.20/m³ for CCA. When annualised over estimated service life, K. senegalensis pressure treatment was 28% cheaper than CCA per year of protection, and dip application of K. senegalensis extract was cheaper still—US$9.80/m³—with acceptable protection for non-ground-contact interior use. The break-even analysis showed that any eco-friendly treatment paying for itself within 5 years at Philippine lumber prices was economically viable, and three of the five methods met this threshold.

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