Vegetable Oil as Fuel
As any diesel historian will tell you, the use of vegetable oil as a fuel is not a new idea. Indeed, Rudolf Diesel, the German engineer who developed the Diesel engine, was fully aware of its ability to run on various diverse fuels, including pure vegetable oil. He was in fact drawn to such a prospect, stating in 1911 that “the Diesel engine can be fed with vegetable oils and would help considerably in the development of agriculture of the countries which use it.” While the legitimacy of this statement is debatable (see Cons), it nonetheless demonstrates that plant oil as fuel is not a radical modern idea, but rather an established, if neglected, one.
It should be made clear that vegetable oil, in all its various forms, can only be used in Diesel engines—it cannot mechanically function in a regular gasoline engine. Ethanol, a similar but significantly distinct biofuel, can be used in regular gas engines. We will not go much into ethanol, but it is important to note that the recent surge of interest in and production of ethanol-based fuels should be observed with a critical eye, so that all facets of this possibly beneficial fuel are fully understood. If you are interested, we do not feel that the primary current U.S. manner of ethanol production (i.e.- with corn) is the right solution, but it could represent a step towards more sustainable and efficient biofuels (for more information see here at the Argonne National Laboratory, or here at Cornell University, or even here at Wikipedia, among various other sources).
At the present time, there are two main ways to use vegetable oil in Diesel engines: first, through the production of biodiesel, and second, through engine modification for the combustion of straight vegetable oil.
Biodiesel involves taking pure plant oil and subjecting it to a series of chemical reactions to change its chemical composition and increase its viscosity to the point of being able to be used in unmodified Diesel engines. Typically, however (particularly in commercial productions), this pure vegetable product (dead plants) is mixed with regular petroleum diesel (long-dead critters and plants) to produce what most people know as biodiesel. From this mixing comes the labeling of various biodiesels by their ratio of vegetable to petroleum—that is, B20 is 20% vegetable oil, B50 is 50%, B100 is 100%, etc. So, to summarize, biodiesel functions in essentially the same manner as regular diesel and can be used, unaltered, in any Diesel engine.
The use of straight vegetable oil to power Diesel engines requires that components of the engine and/or vehicle be modified with various add-ons or alterations. These mechanical alternations come in two primary forms: a "single-tank (or one-tank) system" and a "two-tank system."
In the "two-tank system" the conversion procedure typically involves (primarily) the addition of an extra fuel tank (normally in the trunk) for vegetable oil, an addition and rerouting of various fuel lines, and the redirection of engine coolant to run through the installed extra tank. The extra tank is, fairly obviously, used to store the vegetable oil one plans to use as fuel, just as a regular fuel tank is used to store the petroleum-byproducts one plans to use as fuel. It is connected to the engine through the added fuel lines, and runs through a special valve (called a solenoid valve, if you care) that enables the driver to switch back-and-forth from the regular fuel tank to the extra, vegetable oil tank. However, in order for straight vegetable oil to be combusted in the unaltered engine (and easily carried in the fuel lines), in must be much thinner than its normal room-temperature state. Therefore, the oil in the extra tank must be heated (to a minimum of 160 degrees) before it can be used. To achieve this temperature effectively, typically hollow metal coils are installed in the bottom of the vegetable oil tank, through which coolant from the engine is passed. When the engine is running, it transfers extreme heat to the coolant (while the coolant in turn cools the engine) and the coolant then carries this engine waste heat through the metal coils of the extra tank, heating the oil therein. So, for straight vegetable oil to be used in a two-tank system, the engine must first be started on regular diesel or biodiesel until it heats the vegetable oil to the proper temperature and viscosity. The engine can then be switched to run on the pure vegetable oil. To clear out the fuel lines and system after use, the engine must again be run on regular diesel for a few minutes just before shutting off. (For a detailed description of the mechanics of this whole gruesome process, we recommend Joshua Tickell’s book, From the Fryer to the Fuel Tank). This is the primary and most-widespread system used in the United States.
The "single-tank system" was developed in Germany by Elsbett Technologie. It is much less common in the United States, but allows for the use of both petro-diesel and vegetable oil (or any mix thereof) in a vehicle's original fuel tank, with some limitations. TO BE FURTHER UPDATED...
For all of these methods, biodiesel and single-tank and two-tank systems, the vegetable oil fuel can come from two main sources:
First, one could procure pure unused oil from any number of locations (including your kitchen cabinet). Relatively any kind of oil made from plants can be used (including corn, canola, sunflower, linseed, peanut, etc.) but all (in fact many) would not be economical or efficient for such purposes.
The second source, and currently most appealing to us for the purposes of our trip, is what is commonly called waste vegetable oil (WVO). This is oil that has been previously used for other purposes, such as (typically), frying or cooking. WVO can be found at almost any restaurant, fast food joint, or cafeteria, and ideally is free. For restaurants, WVO is a waste product—is trash—so taking it from them (with permission!) should not typically interfere with their normal operations. They are getting rid of it anyway.
WVO provides our best option for fueling a vegetable driven diesel system for a number of reasons, which we examine in the Pros section.
* This page is still being edited. Information presented as fact is correct to the best of our knowledge; if you find errors or discrepancies, please let us know. References will be added eventually. |
