Preparation

• 1
  Animal fats and vegetable oils can be used to make biodiesel fuel.Stockbyte/Stockbyte/Getty Images
  
  Mix a small test batch of biodiesel to figure out how much lye you need to add to the oil to start the process of transesterfication. In a well-ventilated area, add 4.5 grams of granulated lye to 1/5 liter of methanol. This produces sodium methoxide, a highly caustic solution, so protect your hands with gloves. Add the sodium methoxide to 1 liter of warm, filtered cooking oil (filtered through a 5-10 micron cooking oil filter, available from restaurant supply stores). Stir for one hour. The mixture can be stirred by hand or you can use a mechanical paint stirrer. When stirring is completed, allow the mixture to sit for another hour. This will allow the mixture to separate into two layers: a top layer of biodiesel and a bottom layer of glycerin soap. If the layers do not separate, repeat the process and increase the lye to 5.5 grams. Once you figure out how much lye you need to transesterfy the oil you are using, make a large batch of biodiesel.
  
  
• 2
  Diesel engines can run on biodiesel fuels just as they do on diesel fuel.Photos.com/Photos.com/Getty Images
  
  Make a large, 10-liter batch of biodiesel. Add 55 grams of granulated lye to 2 liters of methanol until completely dissolved. Pour the lye/methanol mixture into 10 liters of warm, filtered used cooking oil. Stir the mixture for an hour, then allow it to rest for eight hours. By then the the mixture should have separated into biodiesel on top and glycerin on the bottom. Siphon the top layer of biodiesel from the mixture.
  
  
• 3). "Wash" the biodiesel by adding a matching amount of water on top of it. Let stand 12 hours. This will cause any glycerin in the biodiesel to emulsify with the water, and the water/glycerin mixture will sink to the bottom of the container, leaving a top layer of almost pure biodiesel. Siphon this top layer of biodiesel off, or make your biodiesel-water-glycerin mixture in a container with a tap, wait 12 hours, then drain out the lower layer of water and glycerin.
  
  
• 4
  After your homemade biofuel has all water removed from it, the biofuel can be used in your diesel engine.Jupiterimages/Comstock/Getty Images
  
  Heat the biodiesel to 130 F for 20 minutes to evaporate any remaining water in the mixture.
  
  
• 5). Filter the warm biodiesel fuel through a 5-10 micron cooking oil filter before putting in your diesel engine.