The 80/20 Biodiesel Production Method


Made famous by Dr. Jon Van Gerpen from the University of Idaho, this technique is in use in many a commercial Biodiesel plant yielding excellent results!

How To Do It:
When making the Biodiesel, instead of adding the full amount of methanol & catalyst, split it up into two separate reactions.

In the first reaction, add 80% of what you normally would have used, pull the glycerin off, and then add the rest of the methanol & catalyst & react again. This will generate a little more glycerin that can then be removed as well.

In most cases, the Biodiesel will become more fully reacted when using the 80/20 method.
It’s ideal to use with oil that titrates higher than normal.

Here’s an example of a standard recipe:
100 Gal oil titrating at 5 on a KOH scale
20 Gal Methanol
4542 Grams KOH (7 base + 5 titration = 12 x 378.5 liters)

Here’s how we’d convert it to an 80/20 recipe
The “80” Part
100 Gal oil
16 Gal Methanol (20 x .80 = 16)
3634 Grams KOH (4542 x .80 = 3634)
1) Heat the oil up to 130-135 Deg F
2) Fully dissolve the KOH into the methanol
3) Add the methanol/KOH mixture to the oil & mix for at least 2 hours
4) Allow the glycerin to separate & drain it off (about 10-12 hours settling)

The “20” Part
Same 100 Gal oil
4 Gal Methanol (20 x .2 = 4)
908 Grams KOH (4542 x .2 = 908)
1) Reheat reacted oil up to 130-135 Deg F
2) Fully dissolve the KOH into the methanol
3) Add the methanol/KOH mixture to the oil & mix for 2 hours
4) Allow the glycerin to separate & drain off (about 10-12 hours settling)

Then run a 3/27 Biodiesel Conversion Test to ensure it’s thoroughly reacted.

If reacted, wash the fuel as normal (either with dry washing or water washing).

Why It Works
To explain how this works, imagine all of your oil, catalyst, and methanol on the left side of a balance scale. As the reaction occurs, the reacted Biodiesel, glycerin, and any soap will end up on the other side of the balance scale.

In this particular chemical reaction (called transesterification), the reaction likes to occur until the scale balances out (or reaches something called equilibrium). Once equilibrium is reached, it’s difficult to push the reaction much further; even if there’s still a lot of unreacted oil sitting on the left hand side.

So, with the 80/20 method, we react a portion of the oil into Biodiesel & glycerin, then strip away the glycerin, making the scale out of balance again. We then add more catalyst & methanol to the left hand side and the reaction starts happening again until it brings the scale back into balance (even more Biodiesel & glycerin is produced). By splitting the production process into two separate reactions, we’re able to push more oil from the left side into reacted Biodiesel on the right side and thereby get more completely reacted Biodiesel.

If you’re finding that you continually don’t pass 3/27 tests, give this method a try. You may just be able to “push” your reactions all the way to completion!

Additional Resources:
Two Stage Base/Base Recipes
Biodiesel Tutorial Base/Base Two Stage Processing

About Utah Biodiesel Supply

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