Is ethanol really more eco-friendly than gas?

An Enterprise employee fuels a car with ethanol in Washington, D.C.
An Enterprise car rental employee gases up a Chevrolet with E85 flex-fuel in Washington, D.C. More eco-conscious consumers are demanding cars with higher gas mileage from auto rental companies. See more pictures of AFVs.
Chip Somodevilla/Getty Images

In the energy industry, the need for change is no longer debatable. Beyond the danger of complete dependence on foreign oil when both global politics and gas prices are more volatile than ever, the environmental impact of burning millions of gallons of fossil fuels faster than we can say "greenhouse gases" is beginning to sink into the general consciousness. So what's the answer? Some say it's hydrogen, which is a brilliant alternative but ultimately raises some complex questions about safety. Others point to natural resources like sunlight and wind. Parts of the renewable-energy industry are pretty keen on ethanol, as well -- how can you argue with the wisdom of powering our cars with bountiful corn?

Apparently, you can argue with it, and many people are. First, a quick primer on what ethanol is and how it's made.


Ethanol is grain alcohol. In the United States, it's usually made from corn. In Brazil, it's most commonly made with sugarcane. Wheat, barley and potatoes are also sources of ethanol.

There are a couple of ways to make fuel-grade ethanol, and one of the most common ones is the dry-mill method, which goes something like this:

  • The corn (or other grain) passes through a grinding meal. It comes out as a powder.
  • A mixture made of this grain powder, water and an enzyme enters a high-heat cooker, where it's liquefied. The enzyme helps to break down the grain compound to aide in the liquefaction process.
  • The liquefied mash is cooled, and another enzyme is added to the mix. This enzyme converts the starch into sugars that can be fermented to create alcohol.
  • Yeast is added to the sugar mixture to begin the fermentation process. The sugars break down to ethanol (a form of alcohol) and carbon dioxide.
  • The fermented mixture is distilled. The ethanol separates from the solids.
  • A dehydration process removes water from the separated ethanol.
  • A small amount of gasoline is added to the ethanol in order to make it undrinkable. All ethanol used as a fuel must be made nonpotable.

Byproducts of this process, including ­distiller's grain and carbon dioxide, are useful in the farming and ranching industries and may be sold by the ethanol-manufacturing plant for various purposes. But according to many experts in agriculture, making ethanol a major player in the fuel industry has serious drawbacks.

In this article, we'll look at what makes ethanol a potentially good source of clean energy -- and find out why some people think this potential is limited.


Ethanol Controversy

Some folks have been fueling with corn for decades.
Ethanol fuel isn't a modern invention; some folks have been fueling with corn for decades.

In its current status as a low-percentage fuel additive, the benefits of ethanol are obvious. Since ethanol contains a lot of oxygen in its chemical structure, it burns pretty cleanly. Added in small amounts (typically one part ethanol, nine parts gasoline) to the gasoline that fuels our cars, it reduces greenhouse emissions like carbon monoxide and nitrogen oxides. Argonne National Laboratory reports an approximate 10-ton (9.07-metric ton) decrease in greenhouse-gas emissions resulting from the use of ethanol fuel in 2007 alone [source: Biofuels Digest]. A 2006 study in Wisconsin showed 16 percent fewer high-ozone days since the 1994 introduction of 10-90 fuel [source: Ethanol].

The addition of ethanol to the fuel mix also reduces the amount of gasoline we consume when we drive, and any car can run on this 10-90 ethanol mix (called E10). The 85-15 ethanol mix (called E85) that only fuels special flexible fuel vehicles (FFVs) burns even more cleanly, further reducing the release of harmful gases into the atmosphere that can cause air and water pollution, global warming and smog. But only a relative handful of vehicles can run on this mix -- one in 40 cars as of 2006 [source: Joyce]. It's not commonly stocked in gas stations.


The problem with using ethanol as fuel in a large-scale way comes down to two primary, related issues:

  • There's not nearly as much energy in ethanol as there is in gasoline.
  • Creating significant amounts of energy from food crops would deplete the amount of land available for growing actual food for people to eat.

While most experts agree on these two points, they tend to differ in terms of degree.

According to Cornell University professor of agriculture David Pimentel, producing ethanol actually creates a net energy loss. According to his calculations, producing corn and processing it into 1 gallon (3.7 liters) of ethanol requires 131,000 BTUs of energy; but 1 gallon of ethanol contains only 77,000 BTUs [source: Health and Energy]. And since farmers are using fossil-fuel-powered equipment to plant, maintain and harvest the corn and are using fossil-fuel-powered machinery to process that corn into ethanol and then, in almost all cases, to ship the product to collection points via fuel-powered transport, the ethanol industry is actually burning large amounts of gasoline to produce this alternative fuel. That ethanol could end up containing less energy than the gasoline consumed to produce it.

The transport aspect of the process could change soon, though, with the opening of the very first U.S. ethanol pipeline in December 2008. It carries ethanol 85 miles (136 kilometers) through Florida from Tampa to Orlando. Piping ethanol has always been a problem because the fuel picks up impurities on the way from point A to point B. These impurities are unacceptable in ethanol and can damage traditional gas pipeline material. But the Texas company that developed the pipeline appears to have overcome the challenges [source: Galbraith].

Of course that's just one pipeline. Even so, not all scientists agree with Pimentel's dire analysis regarding energy efficiency. ­The U.S. National Renewable Energy Lab finds that it requires 1 BTU of fossil fuel to get 1.3 BTUs of ethanol to market [source: NREL]. That would mean a 30 percent net gain in energy, not a net loss.

Energy efficiency aside, those in Pimentel's camp actually don't see corn as a truly renewable energy source. Pimentel estimates that powering a car for a single year using ethanol would require 11 acres (44,515 square meters) of corn, space that can be used to feed at least seven people [source: Health and Energy]. Since corn fields in the United States take a while to replenish themselves, due to both soil erosion and irrigation issues, those acres would ultimately be out of commission for an extended period of time, meaning no corn for ethanol and no usable land for other food crops. To sustain an ethanol-based fuel industry, more and more farm land would have to be set aside for corn alone. The ultimate result could be a shortage of domestically grown food and higher prices at the supermarket for all sorts of produce.

One possible answer to the ethanol controversy is something called cellulosic ethanol. Cellulosic ethanol is made from nonfood products such as corn stalks, wood chips and switchgrass. If this tiny corner of the ethanol industry develops into a large enough producer, cellulosic ethanol could prove to be a viable, lower-cost compromise in the ethanol versus gasoline debate.

For more information on ethanol and other renewable-energy options, look over the links on the next page.


Lots More Information

Related HowStuffWorks Articles
More Great Links

  • "Argonne National Laboratory says ethanol reduced GGEs by 10 million tons in 2007." Biofuels Digest. April 22, 2008.
  • Barrionuevo, Alexei. "Springtime for Ethanol." The New York Times. Jan. 23, 2007.
  • Galbraith, Kate. "An Ethanol Pipeline Begins Service." The New York Times. Dec. 10, 2008.
  • Halperin, Alex. "Ethanol: Myths and Realities." BusinessWeek Online. May 19, 2006. tc20060519_225336.htm
  • Joyce, Christopher. "Study Backs Ethanol as Gasoline Substitute." Jan. 26, 2006.
  • Segelkin, Roger. "Ethanol Fuel from Corn Faulted as 'Unsustainable Subsidized Food Burning'."