Ethanol is one of the most common alternative fuels being used in the world today. A clear grain alcohol that has been made for hundreds of years, this moonshine has found new life as a biofuel. In 2007, the United States exceeded expectations and produced seven billion gallons of ethanol, beating out Brazil to be the largest producer in the world. With production processes constantly improving, ethanol has the potential to be a dominant fuel in the future.

How ethanol works. Ethanol can be made from variety of grains, including corn, sugar cane, wheat, sorghum, and potatoes. Most ethanol first undergoes a dry milling process to grind the grain into meal. The meal is combined with water and enzymes to create a simple sugar from the starch. That mixture is fermented, distilled, and a small amount of gas is added to make it unfit for drinking. The resulting alcohol can be used as fuel on its own or mixed with gasoline. Byproducts from ethanol production include carbon dioxide, which is harnessed to carbonate beverages, and a coarse grain that can be used for nutrient-packed animal feed. Cellulosic ethanol, once only a theory, can now be made from tough biomass including plant waste, corn stalks, and switchgrass. This kind of ethanol produces 94 percent fewer greenhouse gas emissions than gasoline. Researchers at the U.S. Department of Energy's Bioethanol Pilot Plant can turn one ton of rough plant material into fuel over the course of a day. And a study by the Proceedings of the National Academy of Sciences published in early 2008 showed that switchgrass produces five times the energy needed to grow it.

Ethanol has clear advantages. Ethanol is made from renewable resources. The amount of oxygen in ethanol improves combustion and reduces harmful emissions. It's also biodegradable, nontoxic, and can be produced domestically. Already, most Americans use gasoline containing 10 percent ethanol as a replacement for the toxic fuel additive benzene. Currently E85 fuel containing 85 percent ethanol and 15 percent gasoline is available at more than 1,000 stations, mostly around the Midwest. Challenges to widespread ethanol adoption persist because it cannot travel through pipelines like gasoline and must be trucked. Ethanol contains less energy than gasoline, which means more frequent trips to the pump. Production also requires energy, although efficiency is rising with help from new technological developments and clean energy sources like wind power for biorefineries. Corn tends to get the most attention in America, but other crops have far more ethanol potential. In other countries, sugar cane, sugar beets, and cassava crops have yielded more gallons per acre than corn.

An alternative fuel front-runner. Ethanol is frequently compared to biodiesel, which is also biodegradable, nontoxic, and cuts emissions. Made from vegetable oils and greases, biodiesel can easily be put into vehicles that already have diesel engines. However, it takes fewer plants to produce ethanol than to make biodiesel. Plug-in hybrid vehicles currently in development could theoretically run with ethanol to significantly minimize the impact on the environment. And, unlike the hydrogen fuel cell technology that is still being tested, ethanol has the advantage of being a reality.

If refineries make it they will come. Ethanol has strong support within the United States government. The country's 2007 Energy Bill calls for increased ethanol production and anticipates that the United States will up its ethanol output to 15 billion gallons by 2015. In addition, the bill encourages scientists and companies to advance cellulosic ethanol technology. E85 has been priced at about the same amount as gasoline, and that's with government subsidies in place, but cellulosic ethanol production is expected to bring the price down. Only flex-fuel vehicles can handle more than 10 percent ethanol, and they comprise between 1 and 3 percent of all vehicles on the road. Conversions are tricky. However, car makers have been urging the government to make biofuels more readily available at the pump to increase demand for flex-fuel cars. In 2007, Americans consumed 20.7 million barrels of oil per day-a thirst for energy that could be met with ethanol.

Ethanol is a clean, renewable energy source. With bipartisan political support and agricultural operations at the ready, ethanol has potential to replace gasoline at the pump. Challenges in ethanol production remain, but the tools to overcome them continue to crop up.

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