One of the things we want to be able to do is make our own biodiesel fuel from waste vegetable oil. There are lots of resources available to make it in batches from used oil. You can get the oil from hamburger joints or Chinese restaurants. We also want to explore other possibilities, notably continuous processes or new processes.

The basic process of converting waste oil to biodiesel is called esterification:

Carboxylic acids react readily with alcohols in
the presence of catalytic amount of mineral acids to yield compounds called
esters.  The process is called Esterification:

The mechanism of the acid-catalyzed esterification
is as follows:

The carbonyl oxygen is protonized so that the carbon
can be more likely attacked by the relatively weaker alcohol nucleophile:

The second step is the rate determining step: the
alcoholic oxygen attack the carbonyl carbon to form an tetrahedral intermediate:

After proton transfer, the water molecule is released:

Finally, the proton catalyst is regenerated:

Steps (1), (3), (5) are rapid proton transfer steps
-- simple acid base reactions. Although bare protons are shown in
each case, they are actually solvated by some Lewis bases, which may be
ethanol or water.  In steps (2) and (4), C-O bonds are formed or broken. 
These steps have higher activation energies than the proton-transfer steps.

Above is from Introduction to Organic Chemistry by Andrew Streitwieser and Clayton H. Heathcock, University of Carnifornia at Berkeley.

Practically, there are three steps in the process:

1. Reflux - heating a mixture of ingredients in a vessel.
2. Separation - separating the organic layer from the aqueous layer.
3. Purification - obtaining the pure ester, which in this case is biodiesel.

To get an idea of what you would need to do, you can look at two recipes from JourneyToForever here or here.

We hope to put up an article of Gadgetarius' actual setup in the near future, as well as discuss other ways to do it. I read some articles today on using solid acids as catalyts for esterification. You can read one article on why you would want to do that here (or if that link disappears get the article here.) I also found information about sulphated zirconium pellets, which might be used in this same process:

Technical Data for Sulfated Zirconia Pellet

■Summary

Japan Energy's Sulfated Zirconia Pellet is a novel solid acid catalyst which is formed sulfated zirconia that is well known as solid superacid with original method of Japan Energy Corporation. In spite of solid catalyst, our catalyst exhibits acid strength greater than sulfuric acid and shows excellent performance for various acid catalyzed reactions　(esterification, isomerization, acylation, alkylation, etherification, polymerization, cracking etc.).

Today, in manufacturing plants of chemicals in the world, sulfuric acid, aluminum chloride, and acids including fluorine are used in large quantity as catalysts. These catalysts are usually used in homogeneous reaction process, then cause various problems such as corrosion, catalyst separation, acid waste, environmental pollution. Therefore, there are many needs replace to solid catalysts which are easy to handle and environmental friendly. Our catalyst is just the catalyst replies to their needs.

Our catalyst has great environmental advantage because of low corrosion, easy separation, and no acid waste problems. Especially, the pellet form is available for fixed-bed reaction processes. In addition, it is available for recycle use through regeneration consists of a simple carbon burning. Moreover, our catalyst may have excellent economical advantage because of productivity improvement resulting from its good catalytic activity and lowering the cost of equipment.

■Properties

Though optimum catalyst properties are greatly changed with kind of reactions, the properties can be tuned to your needs. Further, we have other catalyst variations such as loaded with noble metal and powdery type. Please readily ask us in detail.

■Supposed Structure of Active Sites

Nature of active sites of Sulfated zirconia is not well comprehended yet. One example of supposed structure is illustrated as follows(M. Hino and K. Arata, Hyomen, Vol. 28, No. 7, 481-491 (1990)).

In this way, it is believed that sulfated zirconia acts either as Bronsted acid catalyst or as Lewis acid catalyst.

■Process Comparison with Sulfuric Acid Catalyst

The use of our catalyst makes it possible to simplify reaction process. Moreover, our catalyst also has environmental advantages because of low corrosion and no acid waste problems.

■Applications for Reactions

* Esterification