Application of the supercritical CO2 extraction technology on the recovery of natural fat from the sheepskin degreasing process

The content of natural fat in sheepskins can amount up to 50% on the dry skin weight. In order to have skins in good conditions to be adequately processed afterwards, it is necessary to degrease them to a some extent. One of the degreasing methods is carried out with non ionic surfactants in aqueous medium. At the end of this degreasing process a highly pollutant emulsion consisting of natural fat and surfactant in water is obtained. In order to reduce the high contamination load of this emulsion, this is heated to 90°C, at which temperature the emulsion breaks. In this way, water with a reduced contamination load and a fatty phase made up of water, salt, natural fat and non ionic surfactant are obtained separately. Given the nature of this fatty phase, no suitable use has been found up to now. This study deals with the feasibility of the supercritical CO2 extraction technology to separate the fatty phase obtained from the residual bath of sheepskin aqueous degreasing into its components, natural fat and non ionic surfactant. On the other hand, the natural fat of sheepskins consists of different components: lanoline, waxes, triglycerides, fatty acids, cholesterol, mono- and diglycerides. The fractionation of the different components of the natural fat as a function of the CO2 pressure and temperature has also been studied. Supercritical fluid extraction technology allows the recovery of natural fat present in the fatty waste obtained from the residual bath of sheepskin degreasing. An increase in the CO2 density leads to the extraction of a larger number of components of natural fat. All the components of natural fat are extracted at an extraction temperature of 45°C and at CO2 density of 0.70–0.75 g/ml. The non ionic surfactant is not extracted under these conditions.