Biodiesel is an eco-friendly, alternative diesel fuel prepared from domestic renewable resources i.e. vegetable oils (edible or non-edible oil) and animal fats, that runs in diesel engines-cars, buses, trucks, construction equipment, boats, generators, and oil home heating units. Biodiesel has been gaining worldwide popularity as an alternative energy source because it is non toxic, biodegradable & non flammable. Various edible and non edible oils, like rice bran oil, coconut oil, Jatropha curcas, castor oil, cottonseed oil, mahua, karanja which are either surplus and are nonedible type can be used for preparation of biodiesel. Biodiesel can be used either in the pure form or as blends on conventional petrodiesel in automobiles without any major modifications. Its biodegradability makes it eco-friendly. It may lead to a revolutionary transformation of the current economic & energy scenario with an era of economic bloom & prosperity for our society.
Some types of biodiesel are manufactured from specifically grown crops that would otherwise serve no purpose. Other types of biodiesel raise certain ethical issues because they are made from crops that are used as a food source. Alternatively there is biodiesel made from waste oil that has already been used in the manufacture of a product, normally food like crisps or from restaurants that use oil in fryers.
In Europe, the main source of biodiesel is rapeseed. Oil from jatropha (Jatropha curcas) nuts has been an increasingly important biodiesel oil source in tropical climates (Openshaw, 2000). Jatropha plants tolerate poor, degraded soils and are resistant to pest and disease. Jatropha plantations for biodiesel production have been started in India and in some African countries.
Palm (Elaeis guineensis) oil is one of the most cost effective biodiesel feedstocks. Palm oil biodiesel has been increasingly produced in Southeast Asia (in Malaysia and other countries) and in South America. Biodiesel from different sources show certain differences in properties caused by different chemical composition, for instance by a higher degree of saturation in animal fats. Most of existing biodiesel experience has been accumulated with Soya and Rapeseed (Majewski, 2005).
One of the primary method for biotechnical preparation of fatty acid methyl ester biodiesel. Biodiesel is produced in a combined microbial/chemical process in which Cryptococcus curvatus in a sterile whey fraction preferably deproteinized 20% whey concentration without further additives produces an intracellular fatty-acid rich triglyceride, “single cell oil”. After disruption of the cells, the oil is removed from the culture and cell fragments and is directly reacted to known chemicals to produce the fatty acid methyl esters.
Chemically, transesterified biodiesel comprises a mix of mono-alkyl esters of long chain fatty acids. The most common form uses methanol (converted to sodium methoxide) to produce methyl esters as it is the cheapest alcohol available, though ethanol can be used to produce an ethyl ester biodiesel and higher alcohols such as isopropanol and butanol have also been used. Using alcohols of higher molecular weights improves the cold flow properties of the resulting ester, at the cost of a less efficient transesterification reaction. A lipid transesterification production process is used to convert the base oil to the desired esters. Any Free fatty acids (FFAs) in the base oil are either converted to soap and removed from the process, or they are esterified (yielding more biodiesel) using an acidic catalyst. After this processing, unlike straight vegetable oil, biodiesel has combustion properties very similar to those of petroleum diesel, and can replace it in most current uses.
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