This article was first published in 2008.
Do a quick web search under ‘biodiesel’ or talk to
biodiesel enthusiasts and you could assume that DIY making of biodiesel is cheap
and easy; that it’s environmentally sound; and that all diesel engine cars run
beautifully on the fuel.
But dig further and you’ll also find that the home
production of biodiesel is potentially very dangerous; that to do it safely can involve
costs much higher than they first appear; and that there are major
question marks over car manufacturer support for biodiesel fuelled cars.
And then there’s another (Australian) implication:
all biodiesel (including DIY stuff) is taxed at 38 cents per litre. If the fuel
reaches the required quality standard, you can get that money back from the
government – but few if any home producers have their fuel quality tested, an
expensive process. Instead, they just produce biodiesel on the quiet – modern
day bootleggers waiting for the tax man to knock on the door!
So what actually is biodiesel? Biodiesel is a fuel
made by chemically altering vegetable oils or animal fats.
Vegetable and animal fats and oils are
triglycerides, containing glycerine. The biodiesel process turns the oils and
fats into esters, separating out the glycerine. The glycerine sinks to the
bottom and the biodiesel floats to the top and can be syphoned off.
process is called transesterification, a method that substitutes alcohol for the
glycerine in a chemical reaction, using a catalyst.
The alcohol that is usually used is methanol and
the catalyst is either potassium hydroxide (KOH) or sodium hydroxide (caustic
Biodiesel can be made in small or large batches:
the smaller the batch, the more easily obtainable the equipment needed. journeytoforever.org
describes the making of a small test batch of biodiesel.
(Note: the following process is described here
just to show what is involved in making a small batch. If you wish to make
biodiesel, you MUST observe very important safety requirements for the handling
of these chemicals and follow a much more detailed set of instructions.)
1 litre of new vegetable oil (eg supermarket
200 ml of methanol
either potassium hydroxide (KOH) or sodium
cheap secondhand blender
scales accurate to at least 0.1 grams
measuring beakers for methanol and oil
half-litre translucent white HDPE container with
bung and screw-on cap
2 funnels to fit the HDPE container
three 2-litre PET water or soft-drink bottles
Accurately weigh out the catalyst – the amounts
needed depend on its purity and also the characteristics of the oil. In this
small batch only 3-4 grams are needed.
The catalyst is weighed in a sealed plastic bag to
reduce water absorption from the atmosphere
Measure out 200ml of methanol and pour it into the
Add the catalyst and then swirl the container
until the catalyst dissolves. The mixture will grow hot from the reaction that
is forming sodium methoxide or potassium methoxide (depending on the catalyst
Pre-heat the vegetable oil to 55 degrees C
Pour in the prepared sodium methoxide or potassium
Secure lid and blend for 20 – 30 minutes
Pour the mixture from the blender into the 2-litre
Allow to settle for 12-24 hours
Darker coloured glycerine will form a distinct
layer at the bottom
Decant the lighter coloured biodiesel liquid from
the upper section of the container, placing it in a clean glass jar or another
Put 150ml of the biodiesel into another PET bottle
or glass jar
Add 150ml of water and cap bottle or jar
Shake violently for 10 seconds
If the biodiesel is of appropriate quality, it
should separate from the water in about 30 minutes.
Use two of the 2-litre PET bottles
Pierce a small hole in the base of each bottle and
then cover the holes with duct tape
Pour the biodiesel into one bottle and add 0.5
litres of tap water
Screw cap on tightly and then roll it about until
oil and water are well mixed
Allow to settle and then drain off water from
bottom of bottle through hole
Repeat the washing process
The biodiesel production process is then
Clearly the above description is not suitable for
making large amounts. However it shows the type of process that needs to be
followed, irrespective of the quantity being produced.
Making Larger Quantities
To make useable quantities of biodiesel, more
sophisticated equipment than that described above is needed. One example of a
suitable home unit is the Biomaster biodiesel processor from Australian company
Bioworks. It can produce 150 litres of biodiesel per 24 hour period. The
Biomaster reduces emissions of methanol and does not require manual mixing of
The company lists some of the features of the
- Ideal for used and raw vegetable oils
Self draining cone tanks
Approx. 1 hour labour time
Anti-vortex tank fittings
Centrifugal tank mixing
No pouring or hand mixing of liquids
- Built in sprinkler wash system
Unique design catalyst mixing mesh
150 litre biodiesel production
30 kg glycerol production
2 kW/hr energy consumption per batch
The base Biomaster costs AUD$3245.
One person using a Biomaster is Jonathon Thwaites,
who also runs seminars on home biodiesel production. His biodiesel plant is
located in a backyard shed, has full local government planning permission and
conforms to legislation relating to storage of dangerous chemicals and
For every 100 litres of biodiesel that is
produced, you’ll need about 100 litres of used vegetable oil (or new oil of
course), 20 litres of methanol, water and a small quantity of a catalyst. So, to
perhaps state the obvious, if your car uses a tank of fuel a week, to run it
entirely on biodiesel you’ll need to collect something like 50 litres of oil a
This oil may be available free from your local
fish and chip shop or restaurant, but it is likely that you’ll have to collect
it from a number of shops. (Jonathon Thwaites told us he collects 40 litres a
week from a high class restaurant but that some fish and chip shops change their
oil so rarely that you might collect 40 litres only every five weeks.)
In addition, you need storage facilities for the
used oil, the methanol and the biodiesel. These vessels must be safe for fuel
storage (no bodgy plastic containers!) and must be located in an area approved
for the storage of the quantities you’re dealing with.
The glycerol will also need to be disposed of –
it’s biodegradable and water-soluble so disposal doesn’t normally cause too much
of a problem.
Take into account the sourcing and collection of
the raw oil, the storage of the chemicals and liquids, the requirement (in our
view it’s a requirement!) that quality and safe professional equipment is used,
and you can see that making your own biodiesel is a pretty major on-going
is often blended with petroleum diesel fuel. The ratio of biodiesel to petroleum
diesel is expressed as ‘B’ number – B100 is straight biodiesel, B5 is only 5 per
cent biodiesel, and so on. Biodiesel and petroleum diesel blend seamlessly.
Cars and Biodiesel
So having produced your first batch of biodiesel,
can you just pour it into your diesel car’s tank and head off? Well, yes and no.
Firstly, it’s unlikely – very unlikely – that your
car’s manufacturer’s warranty will be valid if you use untested fuel in your
vehicle. Secondly, even if the fuel can be shown to be of high quality, the
manufacturer may well not permit B100 use.
When using biodiesel, fuel filters will initially
need to be changed frequently – biodiesel acts as a fuel system cleaner and so
more material will be deposited in the filter(s).
Some suggest that the engine’s fuel injection
timing should be retarded for better results (and lower oxides of nitrogen
emissions – see below), a process that on diesels of the last decade will
require engine management modifications and on earlier engines, skilled
Rubber parts in the fuel system may be
deleteriously affected by the biodiesel. This potentially includes seals and
hoses. However, recent cars apparently do not have problems in these areas. (It
must be kept in mind that low sulphur diesel also degrades rubber parts – many
older car fuel systems have had failures when petroleum diesel previously
changed to a low sulphur variety.)
Despite anecdotal evidence of how diesels ‘love’
to run on biodiesel, the only dyno tests that we have been able to find show a
decrease in power or, at best, a matching of the power achieved on petroleum
diesel fuel. This isn’t to say that if the engine was tuned specifically for
biodiesel (eg on electronically managed cars by the use of an aftermarket
interceptor), the results wouldn’t be better – the cetane value of biodiesel is
higher than petroleum diesel.
Finally, the emissions performance of biodiesel is
a question mark. Some studies show on biodiesel increased emissions of
hydrocarbons and oxides of nitrogen, but reduced emissions of particulates and
carbon monoxide. However, how good the emissions are of a modern
biodiesel-fuelled car (complete with exhaust particulate filters, a cat
converter, perhaps urea injection – all designed for petroleum diesel) is not so
Biodegradable: not harmful to soil or groundwater in cases of accidental
Is a renewable fuel
Carbon neutral, will not contribute to the Greenhouse Effect
Can be used neat or blended in any ratio with petroleum diesel
It initially seems a great idea – brewing your own
fuel in your backyard shed from vege cooking oil that’s being thrown away.
And for people in certain circumstances, we think
individuals producing biodiesel is a great idea. For example, we talked to a
truck operator who is making 14,000 litres of biodiesel a week. His trucks pick
up the waste oil (though it now costs him $800 a tonne; four years ago it was
free) and he then turns it into fuel for his truck fleet. His biodiesel plant
operates 24 hours a day, 7 days a week.
We can also see it working very well on a
But those situations are very different to a
suburban home producer. To be honest, the thought of people handling relatively
large quantities of highly inflammable fuels and toxic chemicals - and doing so
in backyard sheds - seems to us to be a series of disasters in the making. With
suitable equipment, and appropriate fuel handling facilities and safety
equipment and procedures, the risk can be brought down to manageable proportions
– but then again, the capital investment is also much higher.
DIY biodiesel? Interesting – sure! But not for
But that’s definitely not to say that biodiesel
itself isn’t worthy of much greater attention and use – but produced
commercially or semi-commercially to the required quality standards.
Jonathon Thwaites - www.sustainability.fm.uwa.edu.au
Biomaster - www.bioworks.com.au