**4. Extraction of essential oils**

Essential oils can be extracted by methods of steam distillation, steam and water utilised strategies to isolate these aromatic essences [41]. The best extraction method will undoubtedly be one which does not use any solvent, generates no residual waste and requires no energy to process it. Obviously, there is no other solvent more ideal than water on plants. It is available, recyclable and non-toxic. Water is already widely used in the extraction of essential oils by steam distillation [42].
