Biodiesel Production

Biodiesel or alkyl esters are produced from oils and fats. The three most commonly used methods of biodiesel production are:

1. Base catalyzed transesterification of the oil with alcohol
2. Direct acid catalyzed esterification of the oil with methanol
3. Conversion of the oil to fatty acids, then to alkyl esters with acid catalysis

The most popularly used method of biodiesel production is by the base catalyzed reaction. It is very economic and suitable due to several factors including:

• A low temperature of 150 F and 20 psi pressure processing
• A high conversion rate of 98% with minimal side reactions
• No intermediate steps for direct conversion to methyl ester
• Materials required are easily available and affordable

The most common method of biodiesel production is by transesterification. The process involves chemical alteration of an organic compound (oil in this case) to alcohol with the help of a catalyst.

Due to the chemical reaction, the oil molecules break down and the alcohol molecule replaces the glycerin portion of the molecule. If the free fatty acid level is very high it is possible that problems like soap formation may occur or sometimes the separation of glycerin can take place. The filtration and processing removes water and other contaminants. With the help of specialized technologies, any free fatty acids present can be removed or transformed into biodiesel.

The pretreated oils and fats are mixed with an alcohol (most commonly used methanol) and a catalyst (sodium hydroxide or potassium hydroxide). The oil particles, triglycerides, are broken apart and turned into methyl esters and glycerin. The glycerin and methyl esters are separated and purified. The excess alcohol is removed by distillation or flash evaporation process. The resulting biodiesel is then washed gently but thoroughly to remove any other impurities like soap or catalyst residues. It can be used as a fuel in diesel engines, and there is no need for making any modifications to the engine.