How far can you drive on a bushel of corn?
Popular Mechanics is Crunching the numbers on alternative fuels.
The Great Alt-Fuel Debate: It takes five barrels of crude oil to produce enough gasoline (nearly 97 gal.) to power a Honda Civic from New York to California. So how do the alternative fuels that may gradually reduce America's dependence on foreign oil stack up against the mileage and convenience of the filling-station stalwart?
Case For: Ethanol is an excellent, clean-burning fuel, potentially providing more horsepower than gasoline. In fact, ethanol has a higher octane rating (over 100) and burns cooler than gasoline. However, pure alcohol isn't volatile enough to get an engine started on cold days, hence E85. Much smaller quantities of ethanol are also added to around 30 percent of the gasoline sold in the States to meet EPA requirements for oxygenated fuels in metropolitan areas with the country's worst ozone air pollution.
According to the National Ethanol Vehicle Coalition (NEVC), E85 currently is available in 36 states. The Environmental Protection Agency (EPA) lists 34 models of flex-fuel vehicles (FFV)--cars and trucks that can burn pure gasoline, E85 or any ratio of gas/ethanol in between--available in the 2006 model year. The NEVC estimates that 6 million FFVs have been sold in the States to date.
The performance of E85 vehicles is potentially higher than that of gasoline vehicles because E85's high octane rating allows a much higher compression ratio, which translates into higher thermodynamic efficiency. However, FFVs that retain the capacity to run on gasoline alone can't really take advantage of this octane boost since they also need to be able to run on pump-grade gasoline.
Cynics claim that it takes more energy to grow corn and distill it into alcohol than you can get out of the alcohol. However, according to the DOE, the growing, fermenting and distillation chain actually results in a surplus of energy that ranges from 34 to 66 percent. Moreover, the carbon dioxide (CO2) that an engine produces started out as atmospheric CO2 that the cornstalk captured during growth, making ethanol greenhouse gas neutral. Recent DOE studies note that using ethanol in blends lowers carbon monoxide (CO) and CO2 emissions substantially. In 2005, burning such blends had the same effect on greenhouse gas emissions as removing 1 million cars from American roads.
Case Against: Alcohol is a corrosive solvent. Anything exposed to ethanol must be made of corrosion-resistant (and expensive) stainless steel or plastic--from fuel-injection components to the tanks, pumps and hoses that dispense E85, as well as the tankers that deliver it.
Growing corn is an intensive process that requires pesticides, fertilizer, heavy equipment and transport. When considering the viability of ethanol, the total impact of all that activity needs to be taken into account.
Outlook: Hopeful--to a point. According to the Renewable Fuels Association, 95 ethanol refineries produced more than 4.3 billion gal. of ethanol in 2005. An additional 40 new or expanded refineries slated to come on line in the next 18 months will increase that to 6.3 billion gal. That sounds like a lot--and it is--but it represents just over 3 percent of our annual consumption of more than 200 billion gal. of gasoline and diesel.
One acre of corn can produce 300 gal. of ethanol per growing season. So, in order to replace that 200 billion gal. of petroleum products, American farmers would need to dedicate 675 million acres, or 71 percent of the nation's 938 million acres of farmland, to growing feedstock. Clearly, ethanol alone won't kick our fossil fuel dependence--unless we want to replace our oil imports with food imports. READ REST HERE
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