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Have you heard the legend of the steam-powered car? Many decades ago, according to rumor, a gas-powered engine prototype and a steam-engine car were both tested side by side. The large audience in attendance gasped in amazement when the steam engine suddenly exploded.

Neil Chambers, who wrote the book “Urban Green” and is a green-tech consultant at Chambers Design, says the legend may not be true, but does point to an interesting fact: the reason most of us drive a gas-powered car is not necessarily because gasoline is the best combustion agent. He says the story may be one reason why people started trusting internal combustion engines more as a safer engine fuel.

In speaking to several automotive experts, FoxNews.com found there are several fringe options for alternative fuel in cars. Some are so out there that there’s only one working prototype, others are a cause of serious concern over safety in both transporting the fuel and using it in modern engines.

The US consumed about a quarter of the gasoline used in the entire world last year, according to a U.S. Energy Information Administration report. We like our cars. Yet, because it takes millions of years for fossil fuels to form, many automakers are looking for better options, a fuel source that is plentiful like water or at least one that causes fewer carbon-dioxide emissions.

Hydrogen

One of the most promising alternative fuels is hydrogen. Chambers says the main benefit of hydrogen is that it can be generated from water, an abundant source, and that carbon emissions are much lower than gasoline.

Mercedes-Benz is a leading proponent. Their hydrogen-powered 2012 B-Class F-CELL, which is currently available in Southern California, has a 134 horsepower electric motor and a range of about 190 miles. A hydrogen fuel cell stack uses a chemical process to generate the electricity to power the car, so the kind of large, heavy battery pack used in conventional electric cars is unnecessary. Even better, refueling takes no longer than filling up a car with gasoline.

John Hanson, the national manager for environmental, safety, and quality at Toyota, told FoxNews.com that, of the alt-fuels we discussed, hydrogen is on the top of their list. The automaker currently has a demo fleet of about 100 Toyota Highlanders that run on hydrogen fuel cells. He says there is a 2 to 1 advantage in per mile fuel costs over gas engines.

Harvard-trained geologist Byron King with Agora Financial says the main problem with hydrogen-powered cars is that the hydrogen has to be created first by electrolyzing water. He says the process is expensive and complex, two killers in the auto industry.

Sawdust


A few years ago, automotive experts started talking about using sawdust as a potential fuel source. The idea is that, instead of using corn or other foodstuffs to create ethanol, you generate ethanol using sawdust, corn husks, and other waste materials.

“Straw, sawdust, and human waste are all potential feedstocks for syngas, which is convertible into ethanol, butanol, and other liquid alternative transportation fuels,” says Mark Maher, the General Motors executive director for powertrain vehicle integration. According to Mahr, waste material research is in a start-up phase with companies like Coskata leading the charge.

However, King says the idea of using sawdust is not realistic. He cited a Chevron study that said it would take an area the size of New Mexico to produce enough raw materials to create enough ethanol to satisfy U.S. consumption.

Nuclear energy


Could plutonium, thorium, or some other radioactive element power the future car? The idea seems plausible – after all, decaying plutonium is used to propel NASA research spacecraft.

A company called Laser Power Systems is developing an engine that runs on thorium, although the it has not released detailed specifications about how the engine would work. Patrick Cox, an analyst at Agora Financial, says thorium could become a potential fuel source for future cars because it is so abundant, easily mined, safe to handle, and cannot be weaponized.

Because thorium produces such a small amount of radioactive waste, the costs associated with transporting and using thorium in future cars would be 50 percent less than using uranium, Cox says. King agreed, although he says it could take 50 years before researchers come up with a viable thorium-fueled engine.

Another issue with nuclear energy as a fuel source has to do with public perception. Chad Joshi, the CEO of the alternative fuel company Altranex, says nuclear power only makes sense as a centralize power source in plants. There are too many safety concerns with using nuclear power in a moving vehicle for most people. As a result, Maher said the direct use of nuclear power on a vehicle is not likely. However, he said nuclear energy will be a key component to the production of electricity for battery-powered cars.

Wood


Wood chips can be used to heat your home, but why not use them to propel your car? That’s the idea behind the Wood Powered SUV, developed by Beaver Energy.

The company’s converted 1988 Isuzu Trooper turns wood chips into an organic fuel, and can drive about 20 miles on 25 pounds of chips. The truck uses a process called pyrolization, which converts any organic compound (including wood chips, grass clippings, and even garbage) into hydrogen and carbon molecules. The fuel, produced in a contraption on the back of the SUV, is then used in a modified internal combustion engine.

Chambers says using wood for fuel makes sense only because the source material is organic so the material does not need to be produced. Like compressed natural gas, organic fuels could cost about 30% less than gasoline and produce fewer harmful emissions. The main issue of course, is retrofitting the car. It would costs thousands of dollars to modify engines to run on organic fuels, he says, and the infrastructure required to distribute the fuel would have to be created from scratch. 


Ammonia

You use it to clean your kitchen floor, but ammonia might also be a fuel source for your car.

In 2007 a graduate student at the University of Michigan designed and built a bi-fuel pickup truck that could run on either gasoline or a mix of gasoline and up to 80 percent ammonia. According to the study, the advantages of using ammonia are that it is a renewable source of energy, produces no carbon emissions when burned and can cost significantly less than gasoline.

Ammonia, which is comprised of nitrogen and hydrogen, can also be “cracked” in a chemical process to produce hydrogen gas to use in fuel cell cars. The appeal here is that ammonia is potentially much easier to produce and transport than hydrogen.

However, a 2006 study by the Department of Energy (Potential Roles of Ammonia in a Hydrogen Economy) suggests that the size of the type of decomposition reactor needed for the conversion would be so large that it would be impractical to carry one on a vehicle, and the safety hazard created by the toxicity of an ammonia spill in the event of an accident would need to be addressed. But the potential exists to use ammonia as a medium to transport hydrogen to fueling stations where it would be converted on site.