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Biodiesel, Part 2: How It Works and What's Ahead

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author photo by Autotrader June 2008

The Chemistry
"Biodiesel" includes any non-petroleum, typically vegetable-based oil that has undergone a chemical process to remove a waxy substance called glycerin. Since glycerin will clot and thicken at very low temperatures, it is potentially harmful to diesel engines and vehicle fuel systems. Removing the glycerin brings the oil closer to diesel #2 in density, freeze point, and other characteristics so that it can be easily stored, pumped, and burned by any diesel engine.

Many different oils can be converted to biodiesel: peanut, safflower, canola, rapeseed and flax, to name a few. Animal fats and oils can also be broken down using the glycerin-removal process known as transesterification, as may the oil secreted by blue-green algae.

For winter stability, biodiesel is often blended with petroleum diesel to lower its "gel point" — the temperature at which it begins to thicken. Blending with petroleum diesel also helps to alleviate automakers' concerns that biodiesel is relatively new and untested.

Pure biodiesel is known as B100 (100% biodiesel), and a blend with any amount of petroleum diesel is identified with a B followed by the percentage of biodiesel in the blend. (For example, B40 would indicate a blend of 40% biodiesel and 60% petroleum diesel.) A number of major diesel engine manufacturers have confirmed that using B20 in their engines will cause no damage nor void warranties.

Simply put, today's biodiesel production takes the practice of burning peanut oil a few significant steps further than originally implemented by the diesel engine's inventor, Rudolf Diesel. Today's oil sources have been greatly expanded; cold weather performance and fuel stability have been addressed; engine and fuel system reliability and longevity have been certified; and environmental impact (in regard to both fuel production and combustion) has been considered.

Environmental Impacts
The EPA confirms that with regard to most exhaust pollutants, biodiesel scores significantly cleaner than diesel #2. Using B100 in a modern diesel engine — one designed prior to the newest '08/'09 "clean-diesel" specs — yielded the following exhaust stream improvements in relation to petroleum diesel:

  • A 50% reduction in carbon monoxide
  • A 70% reduction in particulate matter (the "soot" or smoke you see coming from diesel tailpipes)
  • A 40% reduction in total hydrocarbon emissions
  • No change in methane emissions
  • A 9% increase in nitrogen oxide emissions

Biodiesel proponents note that the latest round of passenger-car diesel engines, conforming to recent EPA standards, use advanced catalytic converter technology and particulate traps to significantly reduce nitrogen oxide and particulate matter emissions. The end result: diesel engines available now are cleaner burning than their gasoline competitors, even when burning inherently dirtier diesel #2. When this new generation of clean diesels is run on biodiesel blends or B100, their emission profiles will be even cleaner.

Advocates also contend that biodiesel is a better lubricant than petroleum diesel, reducing engine wear and adding longevity to the already sturdy diesel engine. Biodiesel is biodegradable, dissipating quickly after any spills and degrading four times faster than petroleum diesel. It has a higher flashpoint than petroleum diesel — meaning it will not ignite as easily — making it safer and easier to handle and transport. And finally, B100 is nontoxic.

Virgin vs. Waste Vegetable Oil (WVO)
Virgin-based biodiesel is produced from fresh, virgin oil harvested from crops grown for the sole purpose of providing a fuel source. Biodiesel made from fats and oils that have already served a commercial purpose (for example, fryer oil at a restaurant or discarded animal fats) is known as waste vegetable oil-based biodiesel (WVO-based biodiesel).

The price for many vegetable oils has risen steeply as demand for crop-based fuels has increased. Due in part to the American governmental mandate for increased alternative fuel production, this recent price spike has made virgin-based biodiesel less competitive with diesel #2. Costs in many cases have exceeded those of diesel #2. In addition, many believe that deforestation to make room for crop fields for the production of virgin-based biodiesel is harmful to the environment, especially in densely forested regions in countries like Brazil.

For these reasons and others, many are beginning to see WVO-based biodiesel as the most cost-effective and environmentally sensitive biodiesel option. While not uncommon, the production of WVO-based biodiesel still falls into the domain of the environmental enthusiast. Dispensing stations are often independent operations, and WVO collection is on a small, local scale. Certain fast-food restaurant chains have begun looking into donating their WVO as both a means of free waste removal and a bragging right of greater environmental awareness. As of yet, however, no major contracts or deals of this sort have been announced in the U.S.

Biodiesel vs. Other Alternative Fuels & Technologies
Biodiesel has much to recommend it as part of the answer to environmental and energy dependence concerns:

  • The new, advanced diesel vehicles have been shown to be competitive with other green options in performance and fuel economy for the price.
  • From the perspective of environmental impact, biodiesel enthusiasts argue that a biodiesel-powered passenger car is no more complex to dismantle and recycle than a traditional gasoline passenger vehicle, without the battery recycling issues of gas-electric hybrids.

Biodiesel will continue to have a role as an alternative fuel source. How big a role depends on market acceptance and future development of a delivery infrastructure.

Biodiesel Part 1: Back to the Future

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Biodiesel, Part 2: How It Works and What's Ahead - Autotrader