Target of Biodiesel Production

It is estimated that Petrolium Diesel demand by the end of 10th plan (In 2006-07) shall be in the tune of 52.33 million tons. In order to achieve 5% replacement of petroleum diesel by biodiesel by the year 2006-07, there is a need to bring minimum 2.29 million hectares area under Jatropha Curcas plantation.

Biodiesel Production

Biodiesel can be produced from straight vegetable oil, animal fats/tallow & used vegetable oil. There are 3 basic steps followed in biodiesel production from oils & fats :
  1. Base catalyzed transesterification of the oil.
  2. Direct acid catalyzed transesterification of the oil
  3. Conversion of the oil to its fatty acids & then to biodiesel.
Almost all biodiesel is produced using base catalyzed transesterification as it is the most economical process requiring only low temperature & pressure & producing a 95-98% conversion yield. The process being the easiest process the same is dealt as under. The transesterification process is the reaction of triglyceride (Fat/Oil) with an alcohol to form esters & glycerol. A triglyceride as a glycerin molecule as its base with three long chain fatty acids attached. The characteristic of fat are determined by the nature of the fatty acid attached to the glycerin. The nature of the fatty acid can in turn affect the characteristic of the biodiesel. During the es-terification process, the triglyceride is reacted with alcohol in presence of a catalyzed, usually a strong alkaline like sodiuIi1 hydroxide. The alcohol reacts with the fatty acids to form the mono-alkyl ester or biodiesel & crude glycerol. In most production methanol or ethanol is the alcohol used (methanol produces methyl esters. ethanol produces ethyl esters) & is base catalyzed by either sodium hydroxide or potassium hydroxide. Potassium hydroxide has been found to be more suitable for the ethyl ester biodiesel production; either base can be used for methyl ester. A common product of the transesterification process is Rape Methyl Ester (RME) produced from raw rape seed oil reacted with methanol.

The reaction between the fat or oil and the alcohol is a reversible reaction & so the alcohol must be added in excess to drive the reaction in right direction & ensure complete conversion. The figure below shows the chemical process for methyl ester biodiesel.