Plan the perfect garden with our interactive tool →

How do I Separate Glycerin From Biofuel?

rural highway image by Sirena Designs from

Making biodiesel fuel at home is becoming an attractive alternative to petroleum because it is clean burning, renewable, and surprisingly easy to make. Biodiesel fuel results when a reaction occurs from heating several chemical agents with vegetable oil, leaving a layer of glycerin and a layer of unwashed bio-diesel fuel. Separating the glycerin from the bio-diesel is a necessary step before the bio-diesel can be further processed and used for fuel. Always wear safety glasses and gloves and work in a well-ventilated area.

Step 1

Measure one teaspoon of sodium hydroxide onto the small dish, and then pour eight ounces of methanol into the half-quart bowl. Slowly add the sodium hydroxide to the methanol while stirring. When the sodium hydroxide is completely dissolved, cover the bowl so methanol fumes do not fill the work area. This creates sodium meth-oxide.

Step 2

Heat one quart of vegetable cooking oil in a double boiler pot, where the bottom boiler is filled with water and the top pot contains vegetable oil. Heat the oil on the stove to between 131 to 150-degrees Fahrenheit, using the temperature gauge to measure. Do not let the temperature go above 150-degrees Fahrenheit.

Step 3

Add the sodium meth-oxide to the oil and stir for 15 minutes. The heat assists with the chemical reaction that occurs in the pot of oil. Stop stirring after 15 minutes and turn off the stove. In about 40 minutes, the glycerin will begin settling to the bottom of the pot, however it will take another eight hours for the glycerin to completely separate from the bio-diesel. During the cooling process, the glycerin will sink to the bottom of the pot while the bio-diesel floats on top.

Step 4

Carefully tip the pot containing the bio-diesel and pour it into the 1 1/2-quart beaker. A beaker is a container that is roughly cylindrical and it is shaped for easy pouring. Pour the bio-diesel pot very gently so the glycerin at the bottom does not break apart and contaminate the bio-diesel. This becomes more crucial as the bio-diesel empties and the glycerin has a greater chance of falling apart. Tipping the pot allows more of control over the glycerin so you can extract more usable bio-diesel.

Step 5

Pour six ounces of clear water over the bio-diesel to wash it. The water will separate at the bottom of the beaker as a layer that looks like milk. The bio-diesel, meanwhile, forms its own layer at the top of the beaker looking like orange juice. As the water sinks through the bio-diesel, it catches any remaining glycerin, methanol and sodium hydroxide and removes them from the bio-diesel. Pour off the bio-diesel from the beaker and then wash it again. Continue washing until the water settling to the bottom is clear. Let the bio-diesel sit in a well-ventilated area for several days in the sun until it turns a brownish yellow.

Garden Guides