What is the difference between biodiesel and SVO?

if you're used to filling up your car with standard gasoline, the difference between biodiesel and straight vegetable oil (SVO, but it also has other names) might be a clear as mud. Here's a cheat sheet. Important Point #1:
  • SVO: is pure vegetable oil, just like what you use to cook with.
  • Biodiesel is plant fat or animal oil that has alcohol (usually methanol) added to it and glycerine removed through a process called transesterification.
and, now, Important Point #2:
  • To use SVO in a vehicle requires converting the diesel engine.
  • Biodiesel can be used in any diesel engine.
Get the long version of the differences between these fuels and more after the jump.

The two biofuels have a lot in common in that they both can work (see above) in diesel vehicles and are sometimes available through the same refueling stations. There is a natural affinity between promoters of the two fuels, especially the committed greenies who go around collecting waste grease to either a.) make into biodiesel or b.) filter and use as SVO.

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SVO goes by many names, including VegOil, waste vegetable oil (WVO) or virgin vegetable oil (VVO). This has led to some calls for clarity, but SVO is stil the most common term for the unadulterated plant oil. Some people use VVO in their engines, but it is more common to recycle cooking grease by filtering it before use.

Since the fuel is not converted, the engine has to be. The conversion process includes adding a second tank for the SVO, a heating system for the fuel, special fuel lines and more. This can cost around $2,000 to have someone install the system. In an SVO car, standard diesel fuel is used to start up and shut down the engine. Once running, the warm engine's radiator fluid heats up the SVO. The heated - and more viscous - SVO can then be used in the diesel engine. For more information on these conversions, check out GreaseCar or Golden Fuel Systems.

Since biodiesel is processed to make it a bit more like petrodiesel, biodiesel will burn in any diesel engine. Modern diesel engines, though, are much more complicated than the diesel engines of old and using B100 is definitely not recommended in a new "oil-burning" Audi A4. Most biodiesel cars are older (think 1970's) Mercedes Benzs and the like.

Biodiesel can be made from many types of plants, and sometimes more: research has shown that adding polystyrene to the fuel can be a benefit. One important thing to know about any biodiesel you might put into your tank is whether or not it's made from crops or from waste grease. Waste grease biodiesel has a much lower carbon footprint because the liquid was already used once. Crop-based biodiesel - made from soy or jatropha or palm oil - is easier to produce in large quantities but carries with it some of the same negatives of land and water use as corn ethanol and also raises the potential for food vs. fuel debates. Biodiesel can also be made from animal fat.

Biodiesel proponents fall into two main camp: the home brewers and the largescale producers. Large companies involved in the biodiesel industry work together through the National Biodiesel Board. Home brewers often associate in local co-ops and through the Internet. If you're interested in trying this, we can recommend Girl Mark's Biodiesel Homebrew Guide. Of course, we should mention that making your own combustible fuel at home is dangerous.

Thanks to GenWaylaid for the idea for this week's issue of Greenlings. If there's a topic you'd like us to cover in a future Greenlings, please send it in or add a comment to this post. To learn more about biodiesel, keep an eye on this page.

Top photo by nicolas.boullosa. Licensed under Creative Commons license 2.0.

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