What is biodiesel?

Biodiesel is an alternative fuel produced from vegetable oils and animal fats. Soybean oil is the most common feedstock but other sources, such as, rape seed (canola), mustard seed, corn oil, coconut oil, sunflower seed, recycled cooking oil and rendered animal fats can be used. Biodiesel is made by reacting a wood or grain alcohol, such as methanol


or ethanol, with the feedstock and with the help of a sodium hydroxide catalyst the reaction produces biodiesel and glycerin. To have production consistency, the American


Society of Testing Materials has established quality standards. Pure biodiesel is designated B100. It has a heat value of 118,170 Btu/gal, about 8% less than No. 2 diesel. This


is due to about 10% less carbon.
For use as a fuel in the transportation industry, a blend of 20% biodiesel to 80% petrodiesel (B20) is fairly standard. For use as a heating fuel a blend of 2 to 20% biodiesel


with No. 2 fuel oil is acceptable in most existing heating systems without any modification. This is referred to as bioheat. Many fuel oil dealers across the U.S can now supply


a bioheat blend of up to 20%. There are several reasons for not going higher than 20% at this time. Biodiesel has a higher viscosity than fuel oil. This means that its pour


point (the temperature below which the fuel will not flow) is higher. The pour point for No. 2 fuel oil is -11oF and for B20, 0oF. In cold climates, bioheat fuel needs to be


stored inside a building.
Biodiesel is also a solvent. This can present some problems in an existing heating system until all the sludge is removed from the tank and supply lines. The filter may have to


be changed several times until everything is cleaned up. Once the system is clean, the burner will probably be more efficient. When ratios of greater than 30% are used, the


rubber seals in the fuel pump can break down causing leaks. Manufacturers are now incorporating better seals in new pumps to overcome this.