June 1, 2008
The Green Roots of Diesel
So what's the scoop on biodiesel — the greener, cleaner version of the notoriously dirty, sooty fuel known as diesel #2?
Well, first off, that was once a capital D in diesel, as in Rudolf Diesel, a turn-of-the-century German inventor, engineer, and social theorist. Diesel is credited with inventing and perfecting the sparkless internal combustion engine at the end of the 19th century. Rather than using a spark that jumped from an electrode to catalyze the explosion within the cylinder walls, Diesel's invention relied on pure compression to produce combustion. The revolutionary engine received the Grand Prize at the World's Fair in Paris in 1900.
As physics dictates, the more a gas is compressed, the hotter it gets. The pistons in Diesel's invention compressed air to at least twice the extent a gasoline engine did, bringing cylinder temperatures to between 1,300 and 1,650 degrees Fahrenheit. When atomized peanut oil was injected into this environment at the top of the piston's stroke, it exploded instantly and intensely.
That's right, peanut oil was the fuel oil Diesel selected to power his invention, long before oil companies ever thought of deriving a petroleum product that would run in Diesel's sparkless (a.k.a. compression-ignition) engine. Remarkably, the first diesel engine was powered by a less-refined version of what we call biodiesel today.
The Rise of Petroleum Diesel
In response to Diesel's invention, oil company scientists invented a petroleum distillate with combustibility properties very similar to those of peanut oil — the early form of diesel #2. This legacy lives on today, in the newly-mandated Ultra-Low-Sulfur formula (ULSD).
Because fossil fuels were exceedingly affordable and readily available for much of the 20th century, the infrastructure for cleaning and processing vegetable oil into a stable, competitive fuel for Diesel's engine never truly developed. Diesel #2 quickly rose to prominence as the fuel for the compression-ignition engine. However, high sulfur content and relatively primitive injection technologies resulted in diesel engines that did not thoroughly burn all of the fuel injected into their cylinders, leading to their reputation as smoky, smelly and slow.
With the gradual rise in gas prices toward the end of the 20th century, a couple of gas crises, and the rise of environmentalism, various individuals have worked to return the diesel engine to its vegetable-fueled roots — the fuel intended by its namesake. Fuels for diesel engines developed from various oils all come under the biodiesel heading. Learn more about the latest biodiesel choices in Part 2.
Biodiesel, Part 2 — How It Works and What's Ahead
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