Introduction:
Bubbling air into Biodiesel has been around as a method for cleansing the fuel almost from the beginning. However, it’s always been utilized during the water washing process to help agitate water up into the Biodiesel layer or as a method for drying the water out of the cleansed fuel.

In this case, however, it’s utilized BEFORE any water washing or dry washing is performed. After the glycerin has been removed from the fuel, air bubbles are passed through the fuel for a period of time to help accelerate the evaporation of methanol from the Biodiesel. By removing a portion of the excess methanol from the Biodiesel, soap suspended by the methanol separates and falls to the bottom of the container.

When properly performed, this method will greatly reduce methanol and soap left over in the Biodiesel prior to washing it. By reducing the methanol and soap amounts, washing can occur much more rapidly and less water will be required to fully cleanse the fuel of it’s impurities.

If the fuel is to be dry washed through ion exchange resins (such as Thermax or Purolite) or cellulose material (such as Eco2Pure), bubbling with air can greatly increase the life of the dry wash media.

How To Do It:
1) Process your Biodiesel as normal
2) Allow the glycerin to settle and remove from the Biodiesel
3) Place a bubbler into the Biodiesel and with the lid to the vessel open, bubble aggressively for at least 8-10 hours
4) Blowing air ACROSS the opening of the vessel (not into the vessel, but across the top of it) will help to pull the evaporated methanol up and away
5) Turn off the bubbler and allow the Biodiesel to settle for 2-4 hours
6) Remove anything that settles to the bottom (most likely soap)
7) Proceed to wash the fuel

Example Bubbler Setup:

This bubbler setup works great with vessels that are 55 gallon or smaller.

It’s made using a lime wood bubble stone, a variable flow air pump, some aquarium tubing and small air fittings.

Additional Notes:
– Be sure the area you’re doing this in is well ventilated as you’ll be evaporating methanol into the air
– Ensure that the bubbler is near the bottom of the vessel and that the air supply is sufficient to generate aggressive bubbles
– It’s helpful to use a vessel that fully drains at the bottom to ensure full removal of any settled soaps
– Bubbling can possibly oxidize the Biodiesel. If you plan on storing the Biodiesel for extended periods of time (3-4+ months), you may want to add an oxidative stabilizer to the fuel afterward
– If it’s possible to heat the Biodiesel while bubbling, it will help remove methanol faster