Biomass from the wood processing industry as a source of phenolic compounds for various chemical applications

Abstract

European forests, which cover approximately 1,040 million hectares in Europe, are crucial sources of renewable biomass. In the Slovak Republic, where forests constitute 41.3% of the land area, broadleaf forests are the dominant type; however, the processing of coniferous wood, particularly spruce (Picea abies), is highly prevalent. Spruce wood is extensively used in the papermaking and construction industries due to its rapid growth and increased wood mass production. This study aims to extract phenolic compounds from spruce bark, a byproduct of the wood industry, using supercritical CO2 extraction—a method known for its environmental safety and efficiency. The bark was manually collected, air-dried, and ground to a fraction size of 1-1.5 mm. To enhance the extraction of phenolic compounds, ethanol and ethyl acetate (1:1) were used as co-solvents. Design of experiment (DoE) was used to optimize the extraction conditions, varying temperatures from 40 °C to 140 °C and pressures from 80 to 480 bars. The results indicate that temperature has a significant impact on the extraction yield, with an indirectly proportional relationship observed. The optimal extraction conditions were identified at a temperature of 47.7 °C and a pressure of 80 bars, achieving the highest yield. Subsequently, an analysis was performed using gas chromatography coupled with mass spectrometry (GC-MS), which identified 27 terpenes, 11 resin acids, 4 phenols, 4 phytosterols, and 17 other compounds. The total phenolic content (TPC) was determined using the Folin-Ciocalteu method as Gallic Acid Equivalent (GAE), ranging from 44.376 to 648.752 mg GAE/100 g of dry bark. The antioxidant activity was determined to be in the range from 27.269 to 284.642 mg GAE/g of sample.