Cetane Number

Cetane number is a measure of the ignition delay (the time from fuel injection into the combustion chamber to ignition); higher cetane numbers are believed to provide easier starting and quieter operation. ASTM D6751 for biodiesel requires a minimum cetane number of 47; the cetane number required of petroleum diesel fuel is 40. B100 produced from highly saturated feedstocks can have a cetane number of 60 or higher. Figure 3 shows the cetane numbers of various biodiesel samples and compares them to diesel cetane numbers. While it is interesting to know the cetane numbers of biodiesels from different feedstock oils, biodiesel is most commonly a blend from two or more feedstocks. Thus, buyers should focus on measured fuel properties rather than trying to determine the feedstock source.