Two Stage Acid / Base Biodiesel Recipes

The Two Stage Acid/Base method is used in commercial biodiesel production to increase yield and reduce soap production. In commercial settings it is used on oil titrating from 2-6 (NaOH). It can be used to make biodiesel from high and very high FFA oils. The process creates water as a byproduct. As the concentration of water increases the reaction is slowed. To combat the slowing of the reaction for high FFA oils, the Acid stage is often performed in steps with the water drained between steps. The most commonly used variation of the Acid/Base method in homebrewing calls for one Acid step followed by one Base step without draining the water between.

Precautions

Acids attack steel. If you intend to use the Acid Eserification process repeatedly, you will need to make your processor from Stainless Steel. Processor made from mild steel and black pipe plumbing will literally be eaten away from the inside out.

Acids react violently with bases. You will need to take special care to keep your caustics away from the acids. Always add acid to water. Adding water to acids can cause the acids to splash.

FATTA Recipe

The internet has a large number of acid/base recipes. The original FATTA recipe seems to be the most commonly cited on homebrew sites.

D Kenny’s Method

Dkenny is a regular on the biodiesel.infopop.cc forum who regularly uses acid/base techniques. This is his recipe. Throughout he uses KOH titration levels. If you use NaOH to perform your titrations you will need to adjust the formulas accordingly.

1. Titrate the oil.
2. Use this formula to determine the amount of H2SO4 needed:. (Titration - 3) * 0.2 = ml of acid needed per liter of oil
3. Figure out 12% of the oil volume. This is the amount methanol needed.
4. Heat the oil to 140F to 150F. 60C to 65C.
5. Pour the acid into the methanol. SLOWLY is best, because it’ll boil like mad.
6. Add the methanol/acid mix to the oil.
7. Stir for 2 to 12 hrs. The easy way to determine when it's done is to titrate the mix as it processing. It'll reach 3 or so when it's done, if all went well.

Titrate your oil and use the standard 8g + Titration (KOH) to determine your KOH amount for the base stage.

If your initial titration was below 14, you will add methanol equal to 10% of the initial oil volume. That would give you 22% total methanol when you add the methanol from the acid stage to the methanol added in the base stage.

If your initial titration was above 14, then drain half of the methanol you added for the acid stage before proceeding with the base stage. You will now add methanol equal to 16% of the initial oil volume. The extra 6% is to compensate for the methanol drained.

If you drained, remix and recheck the titration. normally it drops from the ending titration

Math Example