(215g) Supercritical CO2 extraction of Resin and Rubber from Guayule (Parthenium argentatum A.Gray) Biomass

Guayule (Parthenium argentatum A.Gray) is a desert shrub native to the southwestern U.S. and northern Mexico and one of the main alternative sources of natural rubber. To obtain high-quality rubber, the separation of non-rubber constituents (resin) is a crucial step during guayule biomass processing. Unlike other natural resins which are extracted as the main product and primary source of revenue (e.g. balsam and pine), guayule resin currently contributes little to the economic feasibility of guayule as an industrial crop. According to techno-economic analysis, however, the value-added use of resin can largely impact rubber production costs as much as 50%.

Guayule resin contains a wide range of secondary metabolites such as guayulins and argentatins with potential commercial applications in foods, pharmaceuticals, bio-insecticides, adhesives, coatings, etc. The separation, fractionation, and purification of guayule resin are critical to any value-added use of such a multicomponent mixture. Despite recent developments in separation techniques and instrumental analysis, natural resin isolation and characterization are still challenging tasks.

Fractionation of guayule resin has mostly been investigated using conventional solvent extraction techniques. Vacuum and steam distillation have been used for the separation of essential oils, with the associated thermal degradation of some non-volatile compounds. Decomposition of thermolabile compounds, consumption of large volumes of organic solvents, and long-time requirements are the main problems associated with conventional fractionation techniques which make the methods less economically feasible for larger scales. Improved extraction techniques can reduce extraction time, energy, and solvent consumption, yet a completely “green” technique that enables isolation of all of the targeted compounds is still elusive.

Guayule resin has the potential to overtake rubber value if the resin fractions can be suitably separated and used in high-value, medium-scale applications like pesticides, paints, and coatings. Of the developed methods for natural resin fractionation with potential for scale-up, pressurized solvent extractions like supercritical CO₂, pressurized liquid extraction, and accelerated solvent extraction are advantageous over other extraction methods due to their higher solubility and solvent diffusivity. In this study, the feasibility of supercritical CO₂ extraction has been investigated as an alternative for guayule resin and rubber separation and fractionation to guide the development of value-added guayule co-products at commercial scale and to enhance the feasibility of guayule as an industrial crop.