Washing Problematic Bio Diesel At Home

Washing your bio diesel is a very important part of the process when you are making biofuel. The washing process removes excess Sodium Hydroxide and Methanol from the fuel meaning that it will burn clean in your engine!

Some of the waste vegetable oil I collected was a mixture of two different oils and probably had some water in it. I had to separate the two different oils and wash them before I could put the finished bio diesel in my car!

When I added the distilled water to the unwashed biofuel the water seemed to be clear at the bottom, however when I agitated the mixture it went cloudy and needed to be left to separate out.

The liquid looks very murky and the water has not separated from the diesel yet. Bio Diesel is Hydrophobic which means it separates from the Water (Hydrogen Dioxide) quite quickly on a molecular level.

In this close up you can see that the very bottom of the bottle contains water after leaving the bottle to stand for an hour or so the mixture looked like this.

A clear separation has occurred. The Sodium Hydroxide and methanol are hydrophillic and so they are dissolved in the water. The washing process has to be repeated until the water is totally clear. The water will appear clear at all times when the Sodium Hydroxide and Methanol have been removed. Effectively washed out of the bio diesel.

Here are the two different oils being washed together you can see that the darker oil has absorbed more methanol and sodium hydroxide than the lighter oil and will therefore take longer to wash!

When the two samples are stood next to each other you can clearly see that the darker of the two bio fuels has turned the water a milky colour. You will see over the next few photographs that the darker sample turns progressively lighter with each wash until both batches of biodiesel are the same colour.

First Wash

Second Wash

Third Wash

The bio diesel is then filtered again and left to "dry" overnight any excess water will evaporate overnight. After leaving the fuel to stand overnight I always filter it again before storing it.

For a complete guide to how you can make biodiesel at home from scratch this is a great book, it contains all the instructions on how you can easily make your own bio diesel processor that you can use to process 100 litres of biofuel a day!