The chemical composition of olive cake can vary based on the climate and extraction method used [20]. Its composition includes the stone (18-32%), pulp, shell, kernel, residual oil and approximately 40-60% water. The main elements present in solid olive by-products are natural polymers, namely lignin (26-30%), hemicellulose (7-9%) and cellulose (7-9%), proteins (5-7%), fatty acids (5-8%) and phenolic compounds (oleuropein, hydroxytyrosol and tyrosol) [21]. This chemical structure highlights the solid waste from olive processing as a promising source of bioactive compounds and nutrients, especially in light of the growing search for natural alternatives to synthetic ingredients [11; 16; 20; 22]. Efficient extraction methods can maximise the utilisation of these compounds, contributing to sustainability and added value in the olive oil industry. Here are several methods for extracting components from olive cake [23]: (1) Solvent extraction: This method involves using solvents to dissolve and extract specific compounds from the olive cake. Common solvents include ethanol, methanol, hexane and water. Solvent extraction is widely used due to its efficiency and ability to extract a wide range of compounds; however, the choice of solvent is critical as it affects the yield and purity of the extracted compounds. Additionally, solvent recovery and disposal can pose environmental challenges [24]; (2) Supercritical fluid extraction (SFE): This method uses supercritical fluids, typically carbon dioxide (CO\({}_{2}\)), at high pressure and temperature to extract components. SFE is a green technology that avoids the use of harmful organic solvents. It is highly selective and can produce high-purity extracts. The disadvantages of this method are associated with the initial setup cost for SFE equipment, which is high, and the fact that the process requires precise control of temperature and pressure [25]; (3) Ultrasound-assisted extraction (UAE): UAE uses ultrasonic waves to create cavitation bubbles in the extraction solvent, which helps to break down cell walls and enhance the release of intracellular compounds. This method is relatively quick, energy efficient and can be conducted at lower temperatures, preserving the integrity of heat-sensitive compounds. The efficiency of UAE can be influenced by the ultrasonic frequency and power as well as the properties of the solvent and the sample [26]; (4) Microwave-assisted extraction (MAE): This method uses microwave energy to heat the sample and solvent, which accelerates the extraction process. MAE is fast, efficient and can reduce solvent usage. It is particularly effective for extracting polar compounds. The method may not be suitable for nonpolar compounds and there is a risk of overheating or degradation of sensitive compounds [26]; (5) Enzyme-assisted extraction (EAE): This method employs specific enzymes to break down cell walls and release the desired compounds from the olive cake. This method can enhance the yield and selectivity of the extraction process. It is environmentally friendly and can be conducted under mild conditions. The cost of enzymes can be high and the process parameters need to be carefully optimised to achieve the best results [27]; (6) Pressurised liquid extraction (PLE): Also known as accelerated solvent extraction, PLE uses high pressure and temperature to enhance the extraction efficiency of solvents. PLE is faster than traditional solvent extraction and can use smaller amounts of solvent. It is effective for extracting both polar and nonpolar compounds; however, the equipment cost is relatively high and there is a risk of thermal degradation of heat-sensitive compounds [28]. Figure 1: An overview of olive oil extraction, emphasising the different by-products generated by each extraction method. Selecting the appropriate extraction method for olive cake components depends on several factors, including the nature of the target compounds, environmental considerations and economic viability.