Jörn Appelt

Crude tall oil contains many valuable chemicals such as fatty acids and terpenes which can be used for the production of bio-based plastics, adhesives and paints. In addition to the widely used vacuum distillation process, crude tall oil can also be upgraded using supercritical CO₂ (scCO₂) extraction. However, research on the extraction of crude tall oil with scCO₂ is still very limited. The main factors influencing scCO₂ extraction are temperature, scCO₂ density and the contact time between scCO₂ and the feedstock. The influence of temperature and contact time was therefore investigated in this study. Extraction vessels with different volumes and different scCO₂ flows were used for this purpose. Increasing the temperature at the same scCO₂ density is decisive for increasing the yield. The yield decreases if the contact time is too low, as the scCO₂ cannot be fully saturated. GC-MS/FID analysis of the extracts and the residue shows a change in the extract composition over time and an enrichment of fatty acids in the extract and of diterpenoids in the residue.

Extractives from silver birch (Betula pendula) can play an important role in the future bioeconomy by delivering the feedstock, for instance, for antioxidative applications. It is, therefore, inevitable to gain knowledge of the distribution of extractive content and composition in the different tissues of the tree for estimating the potential volumes of valuable extractable compounds. This study examines the extractable compound distribution of different tree tissues such as outer and inner bark and wood, respectively, considering the original height of the stem and comparing the yields after Soxhlet and accelerated solvent extraction (ASE). Eleven parts of the model tree (seven stem discs and four branches) were separated into primary tissues and extracted with a ternary solvent system. The investigated extraction methods resulted in a comparable performance regarding yields and the composition of the extractives. The extractives were divided into single compounds such as betulin, lupeol, γ-sitosterol, and lupeone and substance groups such as carbohydrates, terpenes, aromatics, and other groups. The distribution of single substances and substance groups depends on the location and function of the examined tissues. Furthermore, the evidence for the correlation of a single substance’s location and original tree height is stronger for lupeol than for betulin. Primary betulin sources of the calculated betulin output are the outer bark of the stem and the branches. By using small branches, further potential for the extraction of betulin can be utilized. A model calculation of the betulin content in the current birch tree revealed a significant potential of 23 kg of betulin available as a valuable chemical resource after by-product utilization.