**2. Biodiesel as an emerging energy resource**

Biodiesel may be defined as an oxygenated, non-toxic, biodegradable, eco-friendly and sulfur-free alternative diesel oil. Chemically biodiesel may be defined as a fuel that is composed of mono-alkyl esters of long chain fatty acids obtained from renewable sources such as animal fats, vegetable oilsthat comply the ASTM and European quality standards. Different natural oils are used for the production of biodiesel such as coconut, rapeseeds, soybeans and waste cooking oil (**Figure 3**).
