the difficulty is in releasing the lipid from their intracellular location in the most energy-efficient and economical way possible, avoiding the use of large amounts of solvent. a key requirement is that the oil be released and extracted without significant contamination by other cellular components, such as DNA or chlorophyll. there is much scope for approaches based on selective decomposition of the cell wall, using ultrasound, microwave, enzymes, pressurizd fluid extraction and abrasives, such as silica powder. the mechanism of each of these techniques is different but most of the techniques involve disruption of cell to release the lipid present in cytoplasm