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Tips

 

Getting started
There are some basic pieces of equipment that you need to manufacture biodiesel and also to check the quality of what you are producing. You will need:

• A glass kitchen blender, because sodium methoxide will react with plastic ones and cause them to crack and leak-used only for making biodiesel.
• A set of scales-capable of weighing 3.5 grams if using sodium hydroxide (NaOH) or 9 grams if using potassium hydroxide (KOH)
• A pH indicator or indicator solution (for use when washing and making biodiesel from used oil)
• A filter of some description (such as a sock filter or coffee filter papers)
• Methanol (try a member of a motor racing club)
• A tub ofNaOH or some KOH.

You will need a system to wash your fuel, either an aquarium pump or a pump-up sprayer. A hydrometer to test the specific gravity of the biodiesel can give an idea of the quality of the product. You should end up with fuel that has a specific gravity of 0.885. Sodium hydroxide (more commonly known as caustic soda) and potassium hydroxide are available from chemical suppliers. Caustic soda is also available at supermarkets.

Be careful washing
Before you start, you need to realise that Methanol and NaOH are dangerous substances. Methanol can irritate the skin and respiratory tract or blind or kill you if ingested. NaOH has the capacity to inflict severe chemical burns to the skin or the mouth, throat and digestive tract if swallowed (and probably even worse). Wear safety gear (glasses, PVC gloves and apron), keep supplies of running water and vinegar nearby and use the chemicals with caution and in a safe and responsible manner. I will also add that I will not be held responsible in anyway for any damage or injury that may result from readers making biodiesel.

Method
For every one litre of fresh vegetable oil you will need 3.5 grams of NaOH, and 200ml of methanol. With safety gear on, measure 200ml of methanol into your glass blender. Then weigh 3.5 grams of NaOH and carefully tip into the blender. Place the lid on the blender and mix until the caustic soda has dissolved. You have made sodium methoxide. Be careful as this is a very dangerous chemical. You then carefully pour the one litre of fresh vegetable oil into glass blender containing the sodium methoxide. Mix for 10 minutes and then let stand for six hours. During this time you will see a dark layer on the bottom with a clear layer on the top.
The glycerine, having a higher specific gravity, will set tle to the bottom and the biodiesel will be on top of the mixture. Decant the biodiesel carefully to ensure that you don't mix any glycerol back into the mixture.

Washing
You will first need to wash your biodiesel before using it. Even though it won't look like it, you will have soaps suspended in your biodiesel. The easiest way to get rid of soap is to add water and turn it into an emulsion. There is a lot of debate about the best way to wash biodiesel, but the simplest way is to wash with an equal volume of water and gently spray onto the top of the biodiesel through a pump up sprayer. Leave it to settle and again the biodiesel will be on the top of the mixture, with soapy water on the bottom. Test the pH of your biodiesel and continue to wash it until the pH is close to 7.5. To ensure there is no water in your biodiesel, heat it up to 100 degrees and evaporate any water. Hey presto, just filter and then add to your diesel tank.

By now, if you aren't put off making biodiesel, then like me, you will want to go onto doing reactions with used vegetable oil (because it's cheap!) from the local fish'n chippie or roadhouse. Unfortunately, the process is a bit more complicated and will require a titration to determine the amount of catalyst needed to successfully remove the glycerol from the oil. If you are going to process heavily used oil, you may even need to consider using acid. I looked at this and even made a few batches, but it is really a lot simpler to use fresh oil.

Copyright© Steven Hobbs 2003

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