Running biodiesel in your equipment can be a reliable way to control fuel costs — especially during times of global unrest. But biodiesel behaves differently inside an engine than conventional diesel fuel. It’s important to understand those differences and how to run biofuel successfully in your machines. 
 

Biodiesel Basics

Unlike conventional diesel fuel, which is distilled from crude oil, biodiesel is manufactured from vegetable oils, animal fats, and even recycled grease from restaurants. Biodiesel can also be made from natural gas, carbon dioxide. Because it’s made from these sources, biodiesel is both a renewable fuel and a biodegradable substance. It is a viable “green” option for fleets running diesel powered equipment. Biodiesel is often blended with conventional diesel fuels even though it can be used in its pure form. 

The raw oils or animal fats used to make biodiesel are chemically processed (esterified) to form a fatty acid called methyl ester (referred to as FAME). This esterified product (FAME) is biodiesel fuel that can be used in compression ignition engines. Without the chemical processing referred to as esterification, the oils or fats are not suitable for use as fuel in compression ignition engines. The oil or fat must be esterified and the water and contaminants removed.  

Fuel made of 100% FAME is referred to as B100 biodiesel, or neat biodiesel. Blends of up to 5% biodiesel (B5 fuels) are common in the United States and can be sold without any labeling indicating that biodiesel is contained in the finished fuel. Higher biodiesel blends of up to 20% (B20) are not uncommon in some areas.  

Biodiesel fuel is approved for use in Cat® machines. Only the U.S. specification ASTMD975 — which is the B5 type of biofuel — should be used.

Why Should You Consider Using Biodiesel?

According to Caterpillar, biodiesel offers the following advantages for your business: 

• It is a renewable, nontoxic and biodegradable fuel.

• It reduces tailpipe particulate matter, hydrocarbon and carbon monoxide emissions from most modern diesel engines. 

• It has high lubricity, which reduces friction.

• It has a high cetane number; B5 biodiesel blends have the same attributes as diesel fuel. 

Be Knowledgeable About Higher-Concentration Formulas

Biodiesel fuels with more than 5% biodiesel require more management. Here are some things to be aware of for these more concentrated formulas: 

• At B100, biodiesel has about 8% lower energy density than diesel. At B20 or lower blend levels, the energy density difference from diesel fuel is not significant.

• Biodiesel has lower oxidation stability and storage stability than diesel fuel. 

• Cold temperature operability is different than diesel fuel. Cloud point, pour point, and CFPP are typically higher than diesel fuel.

• Materials compatibility is more restricted than diesel fuel. 

• Higher biodiesel concentrations are more likely to dissolve and absorb water than diesel fuel.

• Metal content is higher than diesel fuel. Biodiesel can contain certain materials naturally or due to processing (phosphorus, sodium, calcium, potassium and magnesium). 

• Contaminants such as glycerides, mono and diesters and sterol glucosides can be present after an incomplete purifying process.

• Expect a higher propensity for microbial growth due to the biodegradable nature of biodiesel and to the tendency of higher water absorption.

Caterpillar Recommendations for Biodiesel Fuel Use

This chart shows which biodiesel blend levels are acceptable for use in Cat engines.