Making Your Own Biodiesel

Maybe not all it's cracked up to be

by Julian Edgar

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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!

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. 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. 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

  1. 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).

  1. 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

  1. 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

  1. 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.

  1. 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.

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 methoxide.

The company lists some of the features of the Biomaster as:

  • 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 fuels.


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 week!

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 exercise.

Mixing and Matching

Biodiesel 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 mechanical adjustment.

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 readily discernible.

Biodiesel Advantages

  • Biodegradable: not harmful to soil or groundwater in cases of accidental spillage
  • 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
  • Conclusion

    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 farm.

    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 us...

    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 -

    Biomaster -

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