Separating your alcohol from your fermented fruit
By Dr Garth Cambray
In the previous article we looked at how to convert old fruit into a fermented mixture containing a small quantity of alcohol. Here we look at a simple, inexpensive way of turning that into a starting material for lawnmower fuel.
A week and a half of fermentation will give you a solution with somewhere between 5 and 10% ethanol fuel by volume. This will not burn in your lawnmower. It needs to be concentrated.
How does one concentrate ethanol fuel from a raw fermented fuel mixture? To do this you will have to separate the ethanol from the other stuff in the fermentation. This is easily done with a still. A still is a device which uses the fact that ethanol evaporates at a lower temperature (78 degrees Celsius) than water (100 degrees Celsius) to separate the two.
Your raw ethanol fuel mixture is heated and the ethanol evaporates before the water and is then taken to another place where the ethanol vapour cools, condenses and runs into a tank. There are many ways of distilling alcohol, some use heat from flames, some use electricity, but we are trying to get away from that, so we are going to show you how to make a solar still – using that great free fireball in the sky, the Sun, to make your own free fuel for you.
To make a solar still, you need a container, a sheet of fibre glass roofing, a little bit of melamine board, some chipboard screws, a tube of silicone, an old towel that is beyond use anywhere else (preferably black – if not dye it black) and some plumbing fittings. Note that to make this I only bought a tube of silicone – everything else was rubbish that was lurking around – this is low cost, and effective and most people will be able to make one from stuff lurking around in the corners of the house and garden.
Make a trough in the bottom of the container as shown. Seal all parts of the wood with silicone – be excessive here, silicone is cheap, taking this thing apart to fix it later will cost more in time. Put a plumbing fitting into the side of the trough and one into the bottom of the container.
Secure the dark towel to the back of the container so that it hangs into the trough.
Secure the fibre glass roofing to the top of the container so that it is completely gas tight.
Allow to dry.
Pour your fermented fuel mixture into the trough – capillary action will draw the water, fruit and fuel ethanol mixture up onto the towel – which – when heated by the sun, will cause the ethanol to evaporate faster than water.
The ethanol vapour will rise and condense on the fibre glass roofing and run down to the bottom where it will run out through the bottom plumbing fitting into an outside storage vessel.
Initially the distillate will have a high ethanol content – with time this will decrease. Separate the different cuts into different containers. Some of the later low ethanol cuts can be kept and redistilled later.
You now have a slightly concentrated alcohol solution. Process all of your fermented fruit juice this way and store it in a tin – take the low alcohol bits and pieces that come out of the still at the end and redistill them a few times.
You will have now managed to convert your low alcohol fermented fruit juice into a higher alcohol – probably 30-40% by volume, distillate. You can put this in the still again and this will allow you to concentrate the alcohol further to 50-70%, depending on how careful you are. This will not however be sufficiently concentrated to run a lawnmower engine. The next step is to build a reflux column, to see how to do this, go to the next article: Making your own reflux column from a piece of old irrigation pipe or some tin cans
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