Vegetable oil based road fuels for diesel
oils can be used in diesel engines either in it's neat form, called
straight vegetable oil (SVO), or in forms produced as a result of
chemical reactions such as transesterification. There are a number
of different recipes for producing shorter chain length chemical
structures and these products are called bio-diesel or E-diesel
or similar. There are many arguments for using each of these fuels
in preference to the other and the following page argues in favor
of SVO: http://www.goatindustries.fsnet.co.uk/svoreport.htm
|Prototype bio-diesel plant photographs.
| The photograph above shows a prototype
bio-fuel production plant composed of, from right to left, a stainless
steel methoxide mixer, a pump, a fuels mixer with internal paddle
and a settlement/bubble-wash tank. In the transesterification reaction,
methanol is firstly mixed with a small amount of caustic soda and
then pumped into the fuel mixing tank where it is mixed with vegetable
oil at approx. 55 degrees C. After about 2 hours the reactants are
pumped into the tank with the conical bottom and one of the products,
glycerin, is allowed to settle out to the bottom. The glycerin is
drawn off from the bottom and the remaining liquid is washed by
adding water and bubbling air from the bottom. One of the main problems
with this process is 'what do you do with the dirty water?' It can
be treated with acid to neutralize the Ph but there are still large
amounts of water to be disposed of.
|The photo above shows methyl ester, or 'bio-diesel' and glycerin
produced from the transesterification of waste vegetable oil that
can be collected from pubs and hotels. The sample shows two distinct
layers, the glycerin and the methyl esters. To get clean, clear
diesel the top layer must be washed with water by a process called
|The photo on the left shows the top of the fuels mixer.
The flywheel seen is powered by a domestic washing machine motor
which itself drives a shaft mounted on two bearing blocks with a
paddle on the end. A gas burner is used to pre-heat the oil. There
are many safety issues to be aware of when producing fuel in this
way. Methanol is extremely inflammable and methoxide extremely corrosive.
Fire or explosions could be caused by sparks from the motor, static
electricity from mixing methanol and localized pressure development
in the pump.
|Vegetable oil processing trailer
|Goat industries is involved in the production and
promotion of vegetable oil based fuels and our equipment is operated
within the specially built trailer shown below and on the right.
One of the main problems with dealing with vegetable oils was that
it produced a lot of mess on the floor very quickly. The oil spills
out of pipe connections every time they are undone and then spreads
over the floor from being trodden in, producing a dangerous, slippery
surface. We solved this problem by using an industrial type metal
grid flooring set in five panels on large galvanized iron drip trays.
The trays each have four drain holes with pipes attached below to
collect oil and water.
The other side of the trailer, as seen above, is mostly
open and makes it appropriate for demonstration purposes at agricultural
Waste vegetable oil filtration
|The photo below shows filtration equipment
for producing SVO ready for the road. Waste oil from pubs and hotels
can be heated in the blue oil drum to about 40 degrees C and then
pumped into the conical filter on top of the green drum. 200 liters
of oil may need a couple of clean filters to hand. They can be easily
changed when clogged up and are held in place by the cord tied over
the rim of the drum. The filtered oil can then be stored in smaller
containers with sealable lids to keep air out. Oil can be stored
for a long time in this way.