7 - Biodiesel from Vegetable Oils

Summary

What Is Biodiesel?

Biodiesel refers to a renewable fuel for diesel engines that is derived from animal fats or vegetable oils (e.g., rapeseed oil, canola oil, soybean oil, sunflower oil, palm oil, used cooking oil, beef tallow, sheep tallow, and poultry oil). Biodiesel is a clear amber–yellow liquid with a viscosity similar to petroleum diesel (petrodiesel, diesel). With the flash point of 150°C, biodiesel is nonflammable and nonexplosive, in contrast to petrodiesel, which has a flash point of 64°C. This property makes biodiesel-fueled vehicles much safer in accidents than those powered by diesel or gasoline. Unlike petrodiesel, biodiesel is biodegradable and nontoxic and significantly reduces toxic and other emissions when burned as a fuel. Technically, biodiesel is a diesel engine fuel comprised of monoalkyl esters of long-chain fatty acids derived from animal fats or vegetable oils, designated B100, and meeting the requirements of the ASTM D-6751 standard. Some of its technical properties are listed in Table 7.1. Chemically, biodiesel is referred to as a monoalkyl ester, especially (m)ethylester, of long-chain fatty acids derived from natural lipids via the transesterification process. Biodiesel is typically produced by reacting a vegetable oil or animal fat with methanol or ethanol in the presence of a catalyst to yield methyl or ethyl esters (biodiesel) and glycerin (Demirbas, 2002a). Generally, methanol is preferred for transesterification, because it is less expensive than ethanol.

Biodiesel produces slightly lower power and torque, which results in a higher consumption than No. 2 diesel fuel for driving.