Summary
We don’t want to put a huge weight on your shoulders but who wants blood on their hands? Renewable fuel sources can ease the pain.  Bio-diesel can be used in any diesel car, pretty much its vegetable oil that has been thinned to a similar consistency as diesel fuel.  

Old Technology
Rudolph Diesel invented the diesel engine around 1893 to run off of multiple fuel sources.  When he demonstrated the engine at the 1900 Exposition Universelle (World's Fair) he was using peanut oil.

What is biodiesel?
Biodiesel is the name of a clean burning alternative fuel, produced from domestic, renewable resources. Biodiesel contains no petroleum, but it can be blended at any level with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with little or no modifications. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics.

Why should I use biodiesel?
Biodiesel is better for the environment because it is made from renewable resources and has lower emissions compared to petroleum diesel. It is less toxic than table salt and biodegrades as fast as sugar. Since it is made in the USA from renewable resources such as soybeans, its use decreases our dependence on foreign oil and contributes to our own economy.

Bio-Diesel vs Vegetable Oil
Regular vegetable oil is thicker because it hasn't been thinned out like Bio-Diesel.  You can get your diesel car converted to run off of regular or recycled vegetable oil.  The conversion is simple it just heats up vegetable oil to make it thinner, so your car can burn it easier.

Simplicty
You can mix vegetable oil, diesel and bio-diesel in the same tank at the same time, no problem.