Definition of “straight vegetable oil (SVO)” vs. “biodiesel”

Q. What’s the difference between SVO and biodiesel?

A. Here’s a brief overview on biodiesel vs SVO:

Biodiesel vs Straight Vegetable Oil (SVO)
Vegetable oil seems to be the perfect replacement for petro based diesel, except for the fact that it has too high a viscosity for use in most existing diesel engines as a straight replacement fuel oil. This means you can either modify the engine to deal with high viscosity oil or process the oil to reduce it’s viscosity and we discuss the two options below:

Straight Vegetable Oil
One way to use vegetable oil as a fuel is to modify the vehicle so that it heats up the oil before it is used in the fuel system. Heating vegetable oil to 150F will reduce the oil’s viscosity sufficiently for use in a diesel engine.

It is possible to use Straight Vegetable Oil (SVO) by mixing the oil in with petroleum diesel so the vegetable oil acts as a fuel “extender”, but this is not recommended for long term use.

The other way to fuel a diesel engine with vegetable oil is to reduce the oil’s viscosity before it gets into the tank and in this way, neither the engine or vehicle needs modification. Biodiesel is the name of a variety of ester-based oxygenated fuels made from vegetable oils or animal fats. A Methyl ester of vegetable oil or what we now call Biodiesel is very similar to normal petrochemical based diesel fuel.

Its viscosity is only twice that of diesel fuel and its molecular weight is roughly 1/3 of vegetable oil, hence it can be used as a straight petro-diesel replacement. This reduced viscosity vegetable oil is now called Biodiesel with a number of standards like the European EN 14214 standard and American ASTM standard defining exactly what the properties of that oil should be.

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