Pure biodiesel is classified as B100 and falls under the ASTM D6751 standard in the United States. According to this standard, B100 is defined as "a fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats, designated B 100."
Within the B100 classification, there are four specific grades:
- Grade No.1-B S15
- Grade No.1-B S500
- Grade No.2-B S15
- Grade No.2-B S500
These grades differ primarily in their sulfur content and cold flow properties. The "S15" designation indicates a maximum sulfur content of 0.0015% mass (15 ppm), while "S500" indicates a maximum sulfur content of 0.05% mass (500 ppm).
Each grade must meet specific requirements for various properties including flash point, water and sediment content, kinematic viscosity, cetane number, acid number, and oxidation stability. For example, all B100 grades require a minimum cetane number of 45 and a minimum flash point of 93°C.
For biodiesel to be sold commercially, it must meet these quality specifications. Using biodiesel that doesn't meet these standards can lead to serious issues such as engine seizure, filter plugging, and harmful emissions.
