Valorization of spruce needle waste via supercritical extraction of waxes and facile isolation of nonacosan-10-ol

Abstract

Supercritical carbon dioxide was utilized as a sustainable alternative to solvent extraction of waxes from the waste needles of two spruce species, namely Norwegian and Sitka spruce. These extracts were rich in nonacosan-10-ol, an organic compound with hydrophobic properties that lends its use in the preparation of superhydrophobic coatings. The highest crude yields were 1.7% w/w of needles obtained at 400 bar and 60 °C, while nonacosan-10-ol was selectively extracted at 200 bar and 60 °C (8070 ± 91.1 μg/g of needles). Purification of nonacosan-10-ol from the wax extracts was conducted using a simple rapid green recrystallization technique. This yielded a recovery of 44.6% ± 2% and 48.4% ± 2% of the total nonacosan-10-ol from the original crude Sitka (3600 μg/g of needles) and Norwegian wax (1920 μg/g of needles) respectively. Application of nonacosan-10-ol to a filter paper led to the formation of highly hydrophobic surfaces, with preliminary contact angles of up to 149°. This sustainable production method may develop opportunities to valorize forestry waste within a holistic biorefinery.