During the preparatory actions of the project, a selection of three types of raw materials resulting from tanning processes were selected. This selection has been made based on their origin, considering only the waste from cowhide leather, and at the same time based on the sulphur content, because if biodiesel obtained contents a high level of sulphur, this must be removed before the biodiesel is used in combustion engines in order to avoid emission of these pollutants to the environment.
In addition to the characterisation of the different raw materials, the separation process of the fat and protein fractions has been successfully optimised, since biodiesel and biostimulant will be generated from each of these phases, respectively, and it is important that those have suitable properties for the synthesis process of each product.
One of the most outstanding things during the characterisation stage is the similarity in amino acid composition between these three selected raw materials. These amino acids, which will remain in the protein phase for the synthesis of biostimulants, favour the production of chlorophyll and the absorption of water and nutrients in plants. However, it is also worth highlighting the high content of ashes (high mineral content) of one of the samples. This is because of the formation of soap as a result of the tanning process.
Biodiesel is a liquid that is obtained from natural lipids such as vegetable oils or animal fats by esterification and transesterification processes. Therefore, of the fat fractions obtained from the three types of raw materials selected, it is worth highlighting the quality of one of them compared to the others, even though anyone of the three raw materials are suitable for the supercritical process that will be applied in this project.