I hope that this was not already covered as I did search for it.

The question in my subject is one posed to me after doing several acid/base batches with a 90% great turn out. I had made one bad test batch by calculating methanol wrong, and leaving too much water in the oil.

In a conversation with a bio enthusiast recently I was asked if the use of Sulfuric Acid raises the amount of Sulfur in Biodiesel for the sake of an ASTM test.

As you can imagine, this question came from a small commercial outlet that relies on ASTM standards to sell biodiesl. I realize this is a forum for home brewers, but I cannot help tapping in to the great biodiesel minds on this forum.

I hope the compliment outweighs any offense one would take by introducing a commercial question into a homebrew forum.

Thank you.

Alex,
As far as I understand it, no the Sulfur content is not increased using Estrification. The Acid used is purely a catalyst which is not consumed in the estrification process. Any acid used is neutralized to it's corresponding salt during the proceeding base stage that follows estrification.

-Dave-

The sulfur should be either decanted with the byproduct or washed out. If done properly, none should remain in the fuel. There are a number of BioPro users who've esterified with Sulfuric as part of their process and have passed the ASTM tests.