Biodiesel Fuel: Overview
Biodiesel is a domestically produced renewable fuel that can be manufactured from new and used vegetable oils, animal fats, and recycled restaurant grease. It can be used in most any situation where petrodiesel is used. However, biodiesel is cleaner-burning, biodegradable, and non-toxic. Using biodiesel significantly reduces greenhouse gas emissions and toxic air pollutants because it is essentially free of sulfur and aromatics. Even though “diesel” is part of its name, there is no petroleum or other fossil fuels in biodiesel.
Technically, biodiesel is Methyl Ester, with the technical definition being:
- n. — a fuel composed of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats, designated B100, and meeting the requirements of ASTM (American Society for Testing & Materials) D6751.
Transesterification is the chemical process where the oil (triglyceride) is reacted with methanol or ethanol and a catalyst, such as sodium hydroxide or potassium hydroxide. This removes the glycerol molecule from the oil (triglyceride) and produces a methyl ester—biodiesel, and crude glycerin as a beneficial by-product. Once the glycerin is removed from the oil, the remaining molecules are, to a diesel engine, similar to petroleum diesel fuel. There are some notable differences. The biodiesel molecules are very simple hydrocarbon chains. These chains contain no sulfur or aromatics associated with fossil fuels. Biodiesel is made up of almost 10% oxygen, making it a naturally “oxygenated” fuel.