Dry distillation
Dry distillation involves heating in the absence of oxygen and heat is applied usually as a direct flame to the vessel. The high temperatures release essential oils. And the steams of essential oil are condensed to produce essential oil, this process may lead to pyrolysis in the solid. In extraction dry distillation, many organic compounds may decompose. This method is used to extract essential oils with a high boiling point from wood or coal [20].