The term biodiesel is described as a clean burning alternative fuel, produced from domestic, renewable resources. Biodiesel does not contain petroleum; however it can be blended with petroleum diesel to create a biodiesel blend. There are many positive attributes to biodiesel including its non toxic and biodegradable characteristics. It is also one of the only fuel products that do not emit sulfur into the earth’s atmosphere.
INSIDE THE TERMINOLOGY
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Acid Esterification. Esterification increases the yield of biodiesel. When oil feedstocks contain an excess of free fatty acids they have to go through the process of esterification. The key to effectively preparing for the esterification process is to make sure the feedstocks have been sufficiently filtered by removing all contaminants and water. Upon filtration the feedstocks are fed to the acid esterification process. The catalyst, sulfuric acid, is dissolved in methanol and then mixed with the pretreated oil. Once the mixture is heated and stirred, the free fatty acids are converted to biodiesel. The final step of esterification is to dewater and feed the product to the transesterification process.
Transesterification.Oil feedstocks containing small amounts of free fatty acids are fed directly to the transesterification process. The catalyst, potassium hydroxide, is dissolved in methanol and then mixed with the pretreated oil. The co-products of this reaction are biodiesel and glycerin.
Methanol recovery. Methanol is usually removed after the biodiesel and glycerin have been separated into two layers, preventing reaction reversal. The methanol is then cleaned and recycled back to the beginning of the process.
Biodiesel Refining Once separated from the glycerin, the biodiesel goes through a purification process, removing all remaining alcohol and catalyst. It is then dried and stored. To guarantee the biodiesel is without color, odor and sulfur, an additional distillation process may be implemented.