Client Articles
Particles of Incomplete Combustion: Vegetable Oil vs. Petroleum Products
By Ray Kemp
When discussing PICs, one must consider two things; the engine, and the fuel. Internal combustion engines are inherently inefficient and polluting. Even the best engineered, most finely tuned internal combustion engine does not burn all of the fuel that is fed to it. Therefore, some fuel will always make it through the process incompletely burned and will exit the tail pipe as PICs. That's the sad, but true, nature of the internal combustion engine. All this energy and mind power we're putting into developing new fuels for internal combustion engines is really as fundamentally misguided as searching out new sources of petroleum to burn. What we really should be sweating over is a replacement for the internal combustion engines that are one of the actual root causes of our atmospheric woes. Emf, nuclear, hydrogen, there are a lot of other possibilities.
The quality and operating state of the engine determine the volume of PICs. My beat up old Mitsubishi pickup is a perfect example. When it starts up in the morning, all cold and crotchety, it puts out voluminous blue smoke. That's PICs. Once it warms up to operating temperature, it produces virtually no visible exhaust gas. There are still some PICs, but not nearly as much. The real and valuable difference between petro- and bio-diesel is the quality and nature of the PICs.
Petroleum diesel is made from aromatic hydrocarbons. Petroleum has an "aromatic hydrocarbon ring", a full circle of linked carbons in its molecular makeup. For reasons I don't know, aromatic hydrocarbons are extremely toxic. Everywhere they show up, not just in fuel, they are poisonous. The byproducts of burning aromatic hydrocarbons are also noxious and toxic and carcinogenic.
Bio-diesel is composed of straight chain hydrocarbons. Bio-diesel does not have aromatic rings. The byproducts of burning bio-diesel are non toxic, non carcinogenic, and; to most people, not only not noxious, but actually pleasant to smell.
So, the summary of the PICs discussion is thus:
- All internal combustion engines produce PICs.
- All internal combustion engines are inherently bad.
- The less efficient and more smoky the engine, the more bad it is.
- PICs from petroleum are toxic and carcinogenic.
- PICs from bio-diesel are non toxic and non carcinogenic.
That's the PICs story as I understand it.
Vegetable oil and bio-diesel are totally different chemicals. They have totally different physical properties that I could take pages to differentiate, but I'll leave that alone for the moment.
Vegetable oil is a triglyceride. Bio-diesel is an ester, generally a methyl ester. Triglycerides are big, fat, kludgy molecules. Esters are small, slick molecules. Triglycerides are shaped like a three armed octopus. The head of the octopus is a glycerin molecule (glyceride), with three (tri) fatty acid ester chains hanging off of it. The bio-diesel production reaction breaks those three arms off of the glycerin head and turns them into esters, and that's where you get your bio-diesel; three bio-diesel molecules for each triglyceride molecule you beat up on.
This may sound esoteric, but it has absolutely huge ramifications for the world of bio-diesel and there is a huge degree of public misperception and confusion about this topic. Vegetable oil triglycerides may be burned as fuel but they don't burn cleanly because they're big and kludgy and they have that big glycerin head that really doesn't like to burn at all. That's why vegetable oil itself is not a federally certified fuel like bio-diesel is. PICs like you wouldn't believe.
When you burn straight vegetable oil (SVO) for fuel, you are technically breaking the law. Parallel to the bio-diesel world is the SVO world; people who convert their vehicles to burn SVO. Again, doing this is technically illegal. Environmentally, it may be marginally better than petro because the PICs are non carcinogenic, but not very much better because there are lots and lots of those PICs. Mechanically, SvVO does bad things to your engine and completely bypasses the lubricity benefit that is one of the strongest selling points of bio-diesel. Economically, it would take years to recoup the cost of a well done SVO conversion through fuel-cost savings. So that really leaves only a variety of political reasons to justify burning SVO as fuel.
Finally, bio-diesel can come from a lot of places other than vegetable oil. Bio-diesel can be derived from vegetable oil. It can also be derived from animal fats. In the rarified atmosphere of lab experimentation, bio-diesel can be derived from synthetic molecules that I know almost nothing about, but they're doing it. There are also a bunch of other methods, again mostly experimental, for producing bio-diesel other than the traditional methods that pretty much all production enterprises utilize.
misc @ kf3biodiesel.com
KF3 BioDiesel