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.
Biodiesel
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.
Which method is best, Straight Vegetable Oil (SVO) or
Biodiesel?
In our opinion, Straight Vegetable Oil might be the best way
to use vegetable oil in diesel engines in the long term as
there is no processing required, which makes it the most
efficient way to get the oil from the fields to the fuel tank.
In the short term and until the diesel engine industry fits
all engines with fuel heaters, Biodiesel might be the
quickest way to drive the fuel's adoption and start
displacing some of the petro diesel we use today.
Depending on where you stand on the issue, each camp has its
own proponents. History will tell us which method pans out,
the only thing we know for sure is that vegetable oil will
play a part in meeting some of the world's energy needs.
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