Since biodiesel can be made from, among other things, food crops, there are those who believe producing them does not meet ecological, environmental, and human needs. Opponents also worry if the growth of plants is fast enough to accommodate fuel needs. Another category of potential feedstocks for biodiesel is microalgae. (1)
Biodiesel is an alternative fuel made from renewable biological sources such as vegetable oils both (edible and non edible oil) and animal fats. Vegetable oils are usually esters of glycol with different chain length and degree of saturation. It may be seen that vegetable contains a substantial amount of oxygen in their molecules. Practically the high viscosity of vegetable oils (30- 200 Centistokes) as compared to that to Diesel (5.8- 6.4 Centistokes) leads to unfavorable pumping, inefficient mixing of fuel with air contributes to incomplete combustion, high flash point result in increased carbon deposit formation and inferior coking. Due to these problems, vegetable oil needs to be modified to bring the combustion related properties closer to those of Diesel oil.