How to convert cooking oil waste into biodiesel fuel

Written by emilytrudeau
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How to convert cooking oil waste into biodiesel fuel
Used vegetable oil must be filtered before being processed into biodiesel fuel. (pan image by Daniel Gustavsson from Fotolia.com)

Biodiesel is a fuel made from long chain fatty acids that can be found in vegetable oil and animal fats. These fatty acids are linked with a methanol molecule to form biodiesel. The biodiesel is a safe, reliable, inexpensive, and clean fuel that can be run in any diesel vehicle. The process of converting vegetable oil to biodiesel can be done by almost anyone, and can be a rewarding experience that contributes to your independence and environmental responsibility.

Skill level:
Moderate

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Things you need

  • 1 litre waste oil
  • Coffee filter
  • 99 per cent pure methanol
  • 6.25 grams sodium hydroxide lye
  • 99 per cent pure rubbing alcohol
  • 1 large white plastic container with a tight-fitting lid
  • 1 litre water
  • 3 2 litre soda bottles
  • Duct tape
  • Thermometer

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Instructions

  1. 1

    Filter your waste oil to remove any particulates. This can best be done using a coffee filter. Then heat the oil to remove any water that may be in it. If it is not making popping sounds around 48.9 degrees Celsius, there is no water in it. Otherwise, heat to 100 degrees C and stir carefully to bring water to the top to evaporate. Then heat to 129 degrees C for 10 minutes and let cool.

  2. 2

    Quickly measure out lye into a plastic bag on the scale, and then close the bag. Do not allow the lye to remain exposed to the air for long, as it will absorb moisture. Measure out methanol and pour it into the 1/2 litre plastic container using a funnel. Use the other funnel to pour the lye into the plastic container, and screw the cap on tightly. Swirl the mixture for about a minute at a time, five or six times, until the lye is completely dissolved in the methanol, creating methoxide. The solution will get hot. It should take between 10 minutes and half an hour to completely dissolve.

  3. 3

    Heat the oil to 54.4 degrees Celsius, and carefully pour into a blender. Carefully add the methoxide to the oil with the blender still turned off. Tightly replace the lid, and turn the blender on low. Mix for 20 to 30 minutes.

  4. 4

    Pour the mixture into a 2-liter bottle and screw the cap on tightly. Allow the mixture to cool and settle for 12 to 24 hours. Once it is settled, there will be two distinct layers: the top lighter-coloured layer is the biodiesel, and the bottom darker layer is the glycerine by-product. Carefully pour off the top layer of biodiesel into another 2-liter soda bottle, leaving the glycerine behind. You will have to let it settle again if glycerine mixes into the new bottle.

  5. 5

    Test your fuel by putting 150mL of biodiesel in a plastic soda bottle with 150mL of water. Shake it up well for 10 seconds, and then let it settle. If the mixture forms two distinct layers, with biodiesel on top and water on bottom, you have made quality fuel. If they stay mixed in a light yellow mousse, you will have to repeat the batch, and probably need to measure your ingredients more closely.

  6. 6

    Wash your biodiesel fuel by combining it with 1/2 litre of fresh water in a 2-liter bottle. Mix together and let them settle, just like in the wash test. Poke a small hole in the bottom of the bottle and allow water to drain out. Cover the hole with duct tape and repeat the process two or three more times until biodiesel is translucent.

Tips and warnings

  • Get an inexpensive or used blender that you will not be too sad about ruining.
  • Read all precautions on chemicals that you are using.
  • Wear proper protective clothing such as safety glasses and gloves.
  • Keep away from children, flames, and your skin and eyes.

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