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How to make your own fuelHow to make a simple heat exchanger
Can I burn straight vegetable fat in my diesel engine?How can I know if my engine will run on Straight Vegetable Oil?

If my engine runs on SVO, then can I burn WVO?

The answer very probably is, Yes it will.

Lets assume you have tested the engine on SVO and it works fine, either without any conversion or with the addition of a heated fuel filter and / or heat exchanger.  You may find that your engine will run on SVO only if a little solvent is added to the fuel.  In any situation, there is not any financial gain thereby achieved.  The cost of new food quality SVO is likely to be between 40p to 50p per litre.  Non-food quality SVO may be cheaper but it is not easy to find.  Add to this the cost of the Duty at 45.82 p and you will soon see that it is more expensive to run on SVO than it is to run on DERV.  The only benefit is to the environment.  However the situation will change if the government implements a tax break on the use of SVO.  At present there is no commitment to this, only to a tax break on bio-diesel.  In Germany and most other European countries all non-fossil fuels are Duty free.  Letters to Gordon Brown or Paul Boateng drawing attention to the need to include within the tax break SVO and mixes of fuels containing mainly renewable organic fats, in compliance with other European countries.

At present it is only worth converting to SVO if you can get a supply of WVO at negligible cost.  Most chip shops will be very glad to give away their used fat, some may even be prepared to pay you to take it away.  Just think of that - actually being paid to fill your vehicle up with fuel!  But the reality is more likely to be that the fat will be very dirty and not especially pleasant.  Before use, it will have to be cleaned.

To do this you will need to build a primary settlement tank, a 45 gallon steel oil drum may suffice for personal use.  You will need to fit an means of heating the fat with an immersion heater, and a tap at the bottom to drain out water.  Explore your local area to find suppliers of suitable fat.  For this simple process you need to use clear runny rape seed oil, and not the opaque and more solid Palmitic oils that have the consistendy of peanut butter.  The best form of oil will be clear but an amber colour and without any trace of sediment.  Fill the separator drum until it is nearly full, heat the fat up to about 60 degrees and stir it.  The fat will become more transparent.  Let it settle for about 10 minutes and drain out a sample from the bottom into a pyrex measuring jug.  You should be able to tell if there is any water in the jug, as the fat will float over any water.  The water may appear like white emulsion paint.  Keep removing samples until there is no sign of water.

Then warm the fat up again, and ladle it through a 'Jay' cloth supported in a metal kitchen sieve.  This will remove any suspended particles.  You could also make a permanent filter using the air filter used in a lorry, or several of them in parallel.  You should get a filter with detachable filter papers that can be washed in soap suds.

I then store the cleaned fat in washed and dried 25 litre tubs ready for use.  To every 24 liters I add 1 litre of solvent like white spirit.  This helps to coagulate any remaining animal fats, which are then precipitated forming a thin residue on the bottom of the container.  After at least one month open the tub carefully without disturbing it, and you should find a clear honey like liquid at the top, and possibly a slight residue at the very bottom.  Siphon off the clear liquid and put it into your fuel tank.  Any cloudy material remaining can be put back into your primary settlement tank and it can be processed again.  It is best to keep these tubs protected from cold weather or hot conditions in a shed or garage.

Remember that it is one thing to test a small sample of SVO in your engine, but another to run an engine on SVO for a long period of time.  That is not to say that damage will certainly be caused to the engine.  The fuels we make for commercial sale use a much more sophisticated version of this simple technique.  Some engine manufacturers have suggested that an engine running on vegetable fat will last many times longer than one running on DERV or ULSD.  The fact is that this is an unknown territory.  We need to test the use of SVO in all kinds of vehicles, but to do so cautiously, and not fool-hardedly.  It is always important to maintain the engine properly, check water levels, and check oil levels and make sure you always carry spare fuel filters in the vehicle in case of blockage.  Watch the exhaust for excessive sooting, and every few months go back to running on DERV to remind yourself what the comparison between the two types of fuel is like.

How to make your own heat exchanger

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John Nicholson      September 2005 June 2007
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