Defining the Properties of Biodiesel

& Importance of the ASTM Requirements

Flash Point:

 

The flash point for biodiesel is used as a mechanism to limit the level of unrelated alcohol remaining in the finished fuel. The flash point is also of importance in connection with legal requirements and safety precautions involved in fuel handling and storage, and is normally specified to meet insurance and fire regulations.

The flash point specification for biodiesel is intended to be 100*C minimum. The flash point specification has been set at 130*C minimum to ensure an actual value of 100*C.

 

Sulfur:

 

The effect of sulfur content on engine wear and deposits appears to vary considerably in importance and depends largely on operating conditions. Fuel sulfur can also affect emissions control systems performance and various limits on sulfur have been imposed for environmental reasons. B100 is essentially sulfur-free.

 

Copper Strip Corrosion:

 

This test serves as a measure of possible difficulties with copper and brass or bronze parts of the fuel system. The presence of acids or sulfur-containing compounds can tarnish the copper strip, thus indicating the possibility for corrosion.

 

 

Cloud Point:

 

Cloud point is of importance in that it defines the temperature at which a cloud or haze of crystals appears in the fuel under prescribed test conditions which generally relates to the temperature at which crystals begin to precipitate from the fuel in use. Biodiesel generally has a higher cloud point than petroleum based diesel fuel.

The cloud point of biodiesel and its impact on the cold flow properties of the resulting blend should be monitored by the user to ensure trouble-free operation in cold climates.

 

 

 

Acid Number:

 

The acid number is used to determine the level of free fatty acids or processing acids that maybe be present in biodiesel. Biodiesel with a high acid number had been shown to increase fueling systems deposits and may increase the likelihood for corrosion.

 

 

Free Glycerin:

 

The free glycerin method is used to determine the level of glycerin in the fuel. High levels of free glycerin can cause injector deposits, as well as clogged fueling systems, and result in a buildup of free glycerin in the bottom of storage and fueling systems.

 

Total Glycerin:

 

The total glycerin method is used to determine the level of glycerin in the fuel and included the free glycerin and the glycerin portions of any unrelated or partially reacted oil or fat into its mono-alkyl esters has taken place. High levels of mono-,di- and triglycerides can cause injector deposits and may adversely affect the cold weather operation and filter plugging.

 

Calcium and Magnesium:

 

Calcium and magnesium may be presenting biodiesel as abrasive solids or soluble metallic soaps. Abrasive solids can contribute to injector, fuel pump, piston and ring wear as well as engine deposits. Soluble metallic soaps have little effect on wear, but they may contribute to filter plugging and engine deposits. High levels of calcium and magnesium compounds may also be collected in exhaust particulate removal devices, are not typically removed during passive or active regeneration, and can create increased back pressure and reduced time to service maintenance.

 

 

Sodium and Potassium:

 

Sodium and potassium may be presenting biodiesel as abrasive solids or soluble metallic soaps. Abrasive solids can contribute to injector, fuel pump, piston and ring wear as well as engine deposits. Soluble metallic soaps have little effect on wear, but they may contribute to filter plugging and engine deposits. High levels of sodium and potassium compounds may also be collected in exhaust particulate removal devices, are not typically removed during passive or active regeneration, and can create increased back pressure and reduced time to service maintenance.

Oxidation Stability:

 

Products of oxidation in biodiesel can take the form of various acids or polymers, which, if in high enough concentration, can cause fuel system deposits and lead to filter clogging and fuel system malfunctions. Additives designed to retard the formation of acids and polymers can significantly improve the oxidation stability performance of biodiesel.