Verdict:
Recommended as a short-term strategy until zero-emission cars powered by renewables become widely available. If we can make biodiesel from waste, this fuel becomes the best option.

What is it?:
In 1925, Rudolf Diesel, inventor of the diesel engine, ran his diesel engine on peanut oil. Any organic oil can be easily converted into fuel for any unmodified diesel vehicle, though most manufacturers use soybean or vegetable oil. 

Pros:

• When it comes to global warming emissions, 100 percent biodiesel (B100) outperforms just about every fuel available, reducing vehicle emissions by 41 percent compared to diesel and 52 percent compared to gasoline, even when you factor in soybean production, according to the University of Minnesota. Those statistics only improve when biodiesel is made from waste.
• Diesel vehicles run on B100 biodiesel have 10- to 20- percent higher fuel economies than comparable gas-powered automobiles, according to the US Department of Energy.
• Biodiesel is biodegradable and considered nontoxic by the Environmental Protection Agency. It's also a good lubricant, which helps keep fuel lines from clogging.
• Biodiesel helps reduce US foreign oil imports.
• Drivers can make their own biodiesel from waste vegetable oil collected from local restaurants, which has a further benefit of keeping that oil from entering the waste stream. (Our Real Money article tells you more.)

Cons:

• Americans use more than 40 billion gallons of diesel a year, and shifting just that amount to biodiesel would make impossible demands on our agricultural land. Displacing food crops with biodiesel crops could cause major spikes in world food prices, which would be disastrous for the world's poor.
• Since the majority of the soybeans grown for US consumption are genetically modified, we'd likely see a proliferation of GMO crops if we ramped up biodiesel from soy or other foodstocks.
• Some biodiesel imported into the European Union from Indonesia, Malaysia, and Thailand comes from palm trees planted on clearcut rainforest lands, negating any emissions reduction associated with its use.
• Any blend of biodiesel can gel in cold weather, at higher temperatures than diesel will gel. Drivers get around this problem with tank heaters or winterizing additives.
• Pure biodiesel (B100) is not as widely available as petrodiesel-biodiesel blends. The environmental benefits of biodiesel are diluted, naturally, in blends like the widely availalbe B20 (20 percent biodiesel, 80 percent petrodiesel). 
• Using biodiesel may void your vehicle warranty. According to the National Biodiesel Board, "most major engine companies have stated formally that the use of blends up to B20 will not void their parts and workmanship warranties." If you use a blend higher than B20, however, you may have problems with getting manufacturers to honor your warranty.

Current status:
Biodiesel is more accessible than ever, with the number of US public fueling stations rising from zero in 1997 to 1,432 today.

The concerns associated with converting land from food production to biodiesel production remain an obstacle to scaling up this alternative fuel. However, several promising developments may soon surmount that problem.

In 2004,  University of New Hampshire physicist Michael Briggs noted that aquatic farms could be used to grow crops for biodiesel production. With high oil content, rapid growth rates, and far fewer land requirements, some aquatic crops like algae may make sense as future sources of biodiesel. Biodiesel can be made from waste tallow and other agricultural waste products, says the Sustainable Biodiesel Alliance. And John Rivera, CEO of the United States Sustainable Energy Corp., has pioneered a new process for making biodiesel from soybeans that is about two-thirds more efficient than standard biodiesel processing.

In the meantime, many drivers make biodiesel from waste vegetable oil, the most sustainable option now available.

Should You Make the Switch?:
Yes. If you are thinking about your next vehicle purchase or already own a diesel vehicle, see if you have access to B100 biodiesel or could make your own. You'll help create demand for biodiesel that could spur scientists and companies to advance sustainable ways to expand production of this fuel.

Cars run on B100 and B80 emit fewer greenhouse gases than even a hybrid Prius (see chart). You can make your own biodiesel alone or with a cooperative, order it from a supplier, or, if you have pumps near you, buy it locally.

If you do not have easy access to biodiesel or ingredients to make your own, a hybrid car is currently your best choice.

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