How to make diesel from vegetable oil

What you need

  1. Waste vegetable oil (WVO)
  2. Lye (sodium hydroxide or potassium hydroxide)
  3. Alcohol (Methanol or Ethanol) 15% by volume of the WVO
  4. Heat (perhaps a calor gas burner or diesel heater)
  5. Reaction vessels (perhaps oil drums)
  6. Thermometer
  7. Blender (do it by hand or build something automatic)
  8. Isopropyl Alcohol (use 99% IPA)
  9. Eyedropper (or any other type of 1 milliliter dropper)
  10. pH paper (litmus paper)
  11. Rubber gloves, safety glasses, plastic apron

! ! CAUTION ! !
Use extreme caution when working with these ingredients.

Lye (sodium hydroxide or potassium hydroxide) is also very toxic and burns the skin upon touch. It is also extremely damaging if ingested. Ensure plenty of ventilation and access to water. Have lots of newspaper and detergent on hand.

Methanol (wood alcohol) is toxic. It can be absorbed by the skin and cause nerve deterioration with prolonged usage. If splashed in eyes it can cause blindness and could be fatal if swallowed. Take necessary precautions when using methanol!

Ethanol (grain alcohol) is also toxic. It is found in all alcoholic drinks and gets you drunk. Take necessary precautions when using ethanol!


The make up of the free fatty acids in vegetable oil changes when it been heated (which is why cold pressed oils are better for you). Oil which has been used in cooking will require more of the reactive agents (lye and alcohol) than fresh oil. It is necessary to determine the exact amount of lye needed to neutralize the acids otherwise you will make excessive amounts of glycerin and less biodiesel as a result.

To determine the quantity of lye to use for your oil

  1. Dissolve 1 gram lye in 1 litre of water.
  2. Dissolve 1ml. of vegetable oil in 10 ml. Isopropyl Alcohol
  3. Drop the lye solution into the oil mixture, one milliliter at a time. After each ml. ,check the pH level of the oil mixture.
  4. Continue to add the lye solution into the oil solution, one ml. at a time until a pH of 8-9 is reached.
  5. Write down how many ml. of the lye solution you needed.
  6. To determine the proportions - add 3.5 to the number you wrote down. The result is the number of grams you need to catalyze each litre of oil.

To make your biodiesel

  1. Measure a quantity of oil into a suitable container and heat to 120F.
  2. In separate container mix Methanol (15% by weight or 17.2% by volume in relation to the quantity of oil you are processing) with lye (calculating the amount using the method outlined above). The lye must be added slowly as it will become extremely hot. The resulting mixture is Sodium Methoxide.
  3. Add the mixture to the heated oil mix vigorously for about an hour. You may want to set up some kind of mechanical aid to do this, perhaps using cycle power.
  4. Monitor the rate of separation by taking samples at ten minute intervals.
  5. Stop mixing when it appears that the separation has stopped. Leave the mixture to cool and settle over night or for at least 8 hours.
  6. The free fatty acids (glycerin), will sink to the bottom forming a cloudy layer. On top will be your biodiesel (methyl esters), but before using it, any remaining soaps or salts should be removed (or they may cause engine damage).
  7. Syphon the methyl ester into a separate clean container and add water. Gently stir the mixture then leave it to settle again. When the water has separated from the methyl esters, drain or syphon the water out from the bottom of the container.
  8. Repeat the process until the rinse water you are removing reaches a pH level of 6 to 7 and contains no soap bubbles. If white substances form at the bottom. or any bubbles form at the surface the liquid should be re-washed.
  9. If the liquid appears cloudy, then water is being retained. It should be reheated gently in order to make the water evaporate

Your bio-diesel is now ready to use :-)

Check out more detailed instructions elsewhere on the web:

Discussions on this page


Home | Community | Woodland | Resources | Search