Biodiesel production is typically done with refined or edible oils using methanol and an alkaline catalyst. Edible oils are usually diverted to human consumption, so people often mistakenly believe biodiesel will cause conflict with food availability. Edible oils are not a requirement of diesel, however, for two simple reasons:

1. A large amount of oils and fats are available that are not edible or refined but still can be converted with new technology into biodiesel. This includes waste oil, as well as oil from waste.
2. Engines can be converted with new technology to run on non-edible oils as well as petroleum diesel and biodiesel. This is how Rudolph originally envisioned things.

The second seems less likely to emerge in mass numbers because the complexity of a hardware solution and support. There are engines and conversion kits today. However, hardware solutions present a far greater task to create, deploy and support than to create a new refinement technique for the supply-chain that produces a consistent grade of fuel from waste.

With regard to the first solution, biodiesel researchers and manufacturers found that alkaline-esterification of certain oils had problems with high levels of free fatty acids (FFA). The FFA react with the alkaline catalyst and generate soaps that inhibit the separation of the ester and glycerin.

One solution is to convert high FFA oils into mono-esters. In other words, an acid esterification phase will convert some of the FFA into biodiesel. This process has been found to be successful already with rubber seeds and even tobacco:

The tobacco biodiesel obtained had the fuel properties within the limits prescribed by the latest American (ASTM D 6751-02) and European (DIN EN 14214) standards, except a somewhat higher acid value than that prescribed by the latter standard (<0.5). Thus, tobacco seeds (TS), as agricultural wastes, might be a valuable renewable raw material for the biodiesel production.

An even more interesting system has been described (somewhat exuberantly) by Gas 2.0. The author suggests that technology has finally begun to reach a reasonable level of efficiency for conversion of waste to fuel.

Basically, the process works like this:

* Raw fats and oils of any type are combined with an alcohol
* This mixture is fed through a sulfated zirconia column heated to 300 degrees Celsius
* Their Easy Fatty Acid Removal (EFAR) system recycles any unreacted raw material back through the reactor
* Excess alcohol is recycled back through the reactor
* Pure biodiesel comes out the end

The advantages of the system are:

* No waste produced; No washing or neutralizing of the biodiesel is necessary
* 100% conversion of raw materials to biodiesel
* Any raw fat or oil can be used to make biodiesel
* Very efficient due to heat recapture from the column
* Sulfated zirconia catalyst never needs replacing
* Very small footprint of the reactor system, uses an extremely small amount of area for the amount of biodiesel produced
* Essentially no emissions and no waste stream from the process; Easy permitting from the government

Sounds very steezy. I am reminded of the vehicles in the book Ring World, where the driver would toss garbage into a hopper for fuel.

A company called Ever Cat Fuels has been created to push the technology and apparently will license it to others three to five years from now.