Biodiesel

Biodiesel

Biodiesel has received much attention in recent years. Although numerous reports are available on the production of biodiesel from vegetable oils of terraneous oil-plants, such as soybean, sunflower and palm oils, the production of biodiesel from microalgae is a newly emerging field. Microalgal biotechnology appears to possess high potential for biodiesel production because a significant increase in lipid content of microalgae is now possible through heterotrophic cultivation and genetic engineering approaches.

The production of biodiesel has recently received much attention worldwide. Because of the world energy crisis , many countries have started to take a series of measures to resolve this problem. Finding alternative energy resources is a pressing mission for many countries, especially for those countries lacking conventional fuel resources. In the 1930s and 1940s, vegetable oils has been used as diesel fuels in the emergency situation. With the rapid development of the modern industry, the demand for energy has been greatly increased in recent years, and therefore alternative energy sources are being explored. Thus, the term “biodiesel” has appeared very frequently in many recent reports.

The world total biodiesel production was estimated to be around 1.8 billion liters in 2003 . Although there was no increase in biodiesel production between 1996 and 1998, a sharp increase in biodiesel production was observed in the past several years. It is speculated that the production of biodiesel will be further tremendously increased because of increasing demand for fuels and “cleaner” energy globally.

Biodiesel is made from biomass oils, mostly from vegetable oils. Biodiesel appears to be an attractive energy resource for several reasons. First, biodiesel is a renewable resource of energy that could be sustainably supplied. It is understood that the petroleum reserves are to be depleted in less than 50 years at the present rate of consumption . Second, biodiesel appears to have several favorable environmental properties resulting in no net increased release of carbon dioxide and very low sulfur content.

The release of sulfur content and carbon monoxide would be cut down by 30% and 10%, respectively, by using biodiesel as energy source. Using biodiesel as energy source, the gas generated during combustion could be reduced, and the decrease in carbon monoxide is owing to the relatively high oxygen content in biodiesel. Moreover, biodiesel contains no aromatic compounds and other chemical substances which are harmful to the environment. Recent investigation has indicated that the use of biodiesel can decrease 90% of air toxicity and 95% of cancers compared to common diesel source. Third, biodiesel appears to have significant economic potential because as a non-renewable fuel that fossil fuel prices will increase inescapability further in the future. Finally, biodiesel is better than diesel fuel in terms of flash point and biodegradability .

Conventional biodiesel mainly comes from soybean and vegetable oils, palm oil, sunflower oil, rapeseed oil as well as restaurant waste oil. The number of carbon in the carbon chain of the diesel oil molecular is about 15, which is similar to that of the plant oil with 14-18 ...