How it all started
A very clever man called Rudolf Diesel invented a
new type of engine that operated at a higher compression ratio
and didn't have spark plugs. The first thing that he noticed
was that it was about 30% more efficient than a petrol engine
and, also, he could run it on vegetable oil! Very quickly,
the engine became adapted for use with fossil fuels since
they were, and still are, very much cheaper than vegetable
oil and Rudolf's second idea became forgotten.
Then along came Tony Blair and his chancellor of the
exchequer, Gordon Brown, and they changed the fuel duties
on fuels so that vegetable oil became a viable fuel source
in the UK. Other countries, such as Germany, have been using
vegetable oil as a fuel for many years and have developed
sophisticated methods of adapting engines and processing fuels.
Traditionally, biodiesel is the label attached to 'methyl
esters of fatty acids', which is basically vegetable oil reacted
with methanol, but the British government has broadened the
scope of the definition of biodiesel to include straight vegetable
oil or SVO so opening the field to use relatively unprocessed
oils with much less processing waste and energy consumption.
Environmental campaigners are pushing for the greater use
of sustainable fuels which have less harmful effect on the
planet - biodiesel, in it's most unprocessed state, is one
of the best options that we have.
What is vegetable oil?
Vegetable oil comes in very many shapes
and sizes, with varying properties. The most important consideration
is melting point. The actual vegetable oil molecule is composed
of three long carbon chains on a glycerol 'backbone' and it's
properties are determined by the individual 'fatty acid' chains.
Rapeseed oil, for example, may be composed of different combinations
of about 6 different fatty acids and each one of these creates
a unique molecule, with unique properties. Some waste oil
contains 'free fatty acid', which is a result of water in
fried food reacting with the triglyceride to split it up into
it's four components. Waste oil also contains varying amounts
of animal and fish oils which may be solid at room temperature
in their natural state. As a breast of chicken, for example,
is fried, oil diffuses out of the chicken and is replaced
by oil from the fryer and as more and more chicken is fried,
the concentration of chicken oil increases, thickening the
oil until it may become solid.
There are many different types of vegetable
oil and each one has unique properties. The best one for use
as a fuel is undoubtedly rapeseed oil as it is relatively
thin, cheap to produce and easy to get hold of. A second best
would be sunflower oil. If you go into a supermarket in the
UK, rapeseed oil is the stuff in the cheap plastic bottles
which sometimes has little yellow flowers on it.
Can it be used as a fuel
for diesel engines?
The answer is 'yes', but we have to be careful not
to use it in the wrong way otherwise engine damage may occur.
There are two schools of thought, both of which seem to work
well. The first is to blend vegetable oil in with diesel or
kerosene up to a ratio of about 20%, depending on what extra
additives are used and what the
ambient temperature is. The additive
is used to compensate for the loss in ignition properties
and to help keep the combustion cylinder parts clean. The
second school of thought is to use a two
tank system where the vehicle is started up on a thin,
highly combustible fuel such as fossil diesel and then switched
over to a second tank when the engine is nice and hot. Biodiesel
is a third alternative and can be found blended with diesel
at 5% in some petrol stations. Biodiesel is the scientifically
approved derivitive of vegetable oil and is a relatively highly
processed product which has a much lower viscosity than straight
Vegetable oil works much better in older vehicles
which DO NOT have lucas injection pumps. We have created a
of over 150 vehicles that have been running on vegetable oil
which has highlighted some of the successes and failiures
that people have had. The database can be browsed by make
or model to see if a particular vehicle is already running
on vegetable oil and how well it runs.
Can vegetable oil harm
Yes it can. It must be used within sensible limits
and pushing these limits for convenience or cost will cause
long term, or even immediate problems. Some of the conclusions
that people have made regarding the use of vegetable oil as
a diesel fuel have been contradictory and so there are no
guarantees to be given. Some of the motor industry test labs
found that vegetable oil accelerates coking of the engine,
others found it had no detrimental effect in long term trials.
One of the problems with this research is that none of the
engines were used with 2 tank
systems and so they were started from cold on vegetable
100% vegetable oil, which is a definite disadvantage. A recent
report from Ricardo has shown that older, indirect engines
give good performance statistics when running with a two tank
system, with increased fuel efficiency and similar emmisions
when compared with diesel.
In addition to the resources mentioned above, goat
industries has a discussion
board that has highlighted some other problems that may
be encountered. One of the problems that has been discovered
through discussion is the effect that hot vegetable oil can
have on the filter cartridge in the fuel system. Some cartridges
seem to suffer from deterioration of the glue that binds the
filter cloth to the metal retaining plate, which may be due
to the high temperature of the fuel or the high acid content
if waste oil is used. High acid content may also affect some
of the engine parts and there has been some mention of injector
needles becoming corroded from people running static electricity
Goat industries has endeavoured to produce high quality
information based on extensive research into using vegetable
oil as a fuel for diesel engines. The information published
on this web site will enable people to use this fuel safely
and protect the environment. One of our major concerns is
that the engine must be protected and that the fuel should
not be promoted at the expense of people's vehicles. Information
on some other websites does try to push the limits of sensible
use in an effort to save the planet, but we think that this
will only back fire and give vegetable oil a bad name when
the news of engines blowing up filters through.
Myths and legends of
vegetable oil use
There is a lot of rubbish talked about concerning
these fuels. Some of it is a result of people trying to protect
their 'secret' recipes and thereby creating mis-informative
myths. One of these was the 'teaspoon full of white spirit
in vegetable oil' on the top gear program - absolute rubbish!
The 'white spirit' was supposed to be a special fuel additive.
Beware of myths - lets create legends!
Myth number 2. Not all diesel engines will run on
a mix of 95% diesel and 5% white spirit. Again, absolute rubbish!
We've heard of quite a few vehicles actually breaking down
on this brew. Older vehicles, with indirect injection, without
lucas pumps, are more compatible with higher concentrations
of vegetable oil. White spirit can be added, but quite a bit
more than 5% would be needed to have any effect.
Some people mix vegetable oil with petrol and use
it in a diesel engine! See Database
We have heard of some vehicles travelling over 200,000
km on vegetable oil.
The pros and cons of
using vegetable oil as a fuel
- Environmentally friendly.
- Waste oil is cheaper.
- Smoother engine running - no 'knock'.
- Better lubrication.
- Less reliance on petro-chemicals.
- Enhanced street credibility.
- May cause engine coking if misused.
- May invalidate vehicle warrantee.
- Exhaust smells of chips (unless cat. converter
- Have to pay tax to customs and excise
- Harder to start the engine in the morning
- Will destroy some injector pumps
- Only useful in older vehicles.