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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 its environmentally sound; and that all diesel engine cars run beautifully on the fuel.
But dig further and youll 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 theres 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!
Making Biodiesel
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.
The 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 soda, NaOH).
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.)
Requirements
1 litre of new vegetable oil (eg supermarket cooking oil)
200 ml of methanol
either potassium hydroxide (KOH) or sodium hydroxide (NaOH)
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
duct tape
thermometer
Mixing Catalyst
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 HPDE container
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 used).
Blending
Pre-heat the vegetable oil to 55 degrees C
Pour in the prepared sodium methoxide or potassium methoxide
Secure lid and blend for 20 30 minutes
Separating
Pour the mixture from the blender into the 2-litre PET bottle
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 PET container
Testing
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.
Washing
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 finished.