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Ethanol Explained

June 19, 2008

Yikes! Gas is over $4 a gallon and President Bush and John McCain are talking about drilling for oil on the outer continental shelf. We’ve got a problem (a few actually). So, what’s the solution? More oil is not the answer, but what about alternative fuels?

Alternative fuels, especially ethanol, are getting a lot of press. Some people think ethanol will save us. Others think it will screw us. Before you choose a side, learn the basics: 

Ethanol is “a colorless volatile flammable liquid” according to good ol’ Merriam-Webster. In other words, it’s fuel—and alcohol.

In the U.S., when we talk about ethanol to fuel our cars, trucks, buses, boats and airplanes, we talk about corn ethanol and cellulosic ethanol. Corn ethanol comes from corn kernels. Cellulosic ethanol comes cellulose—a starch-like chain of sugars found in the not-so-yummy parts of the corn plant (the cob, the stalk, the leaves, etc.) and in other things we don’t eat like switchgrass and paper sludge.

And why is ethanol better than petroleum-based gasoline? It’s all about the carbon source, baby. Kara Podkaminer, PhD candidate at Dartmouth’s Thayer School of Engineering explains: “If you’re taking carbon that’s been underground for millions of years and putting that into the air, you’re going to start accumulating carbon dioxide in the atmosphere. But with ethanol, you’re taking carbon that was already in the atmosphere, carbon that was taken up by plants in the last year or so. When you burn it, you’re putting it back into the atmosphere so you’re not really adding any carbon dioxide to the atmosphere. It’s basically net zero greenhouse gas emissions.”

Right now, we’re making corn ethanol in the U.S. (the Brazilians are making sugar cane ethanol). The Department of Energy (DoE) estimates that corn ethanol emissions are 10 to 20 percent below petroleum-based gasoline levels and that corn ethanol produces 26 percent more energy than it takes to make it. But, cellulosic ethanol is even better.

The DoE estimates that cellulosic ethanol emissions are 80 to 100 percent lower than gasoline emissions. Plus, cellulosic ethanol produces 80 percent more energy than the energy required to produce it.

Cellulosic biomass (the fancy term for the stuff used to make cellulosic ethanol) beats corn on a few other points as well. For instance, switchgrass is a low-maintenance prairie grass native to most parts of North America. It doesn’t require much (if any) water or fertilizer and is happiest in areas unsuitable for most crops. Another bonus: these plants fuel the ethanol-making process themselves, no fossil fuels required. Some parts of the plant are fermented into ethanol while the non-fermentable parts of the plant can be burned to power the process.

So, why aren’t we making cellulosic ethanol? Because making corn ethanol is so much easier! (And because it’s easier, it’s cheaper.) But scientists are working on a way to make cellulosic ethanol more efficiently—and once they do that, it could be cheaper than corn ethanol.

Of course, mass-producing ethanol would require a lot of land. And land is a limited resource. (If you want to find out just how much land we’d need to produce enough ethanol to fuel our current driving habits, you’ll have to buy chapter 3 of “Energy and American Society—Thirteen Myths.”)

Does that mean we should create more land? Umm, no. It means that we should keep investigating all of our alternative energy options from ethanol and oil from algae to wind and solar. 

6 Comments leave one →
  1. June 20, 2008 11:48 pm

    Really well-written article, Kelsey!

    Switchgrass sounds like a good alternative energy contributor. I sort of want to make a map of the US that trades best alternative energy resource per geographic area (e.g., solar in New Mexico, algae near coasts and wind near coasts and valleys… ) and then start a government program to educate and encourage industries in these areas as to their “optimal” alternative energy. Ooops, sorry, didn’t realize I was on a soapbox. Hee.

  2. Abby McCarthy permalink
    June 21, 2008 3:37 am

    Hey guys-
    Pete- could you talk about the amount of petroleum-based fertilizer used on the corn grown to make ethanol? Or do I have to go and read chapter 3 myself to figure that one out??


  3. maukamakai permalink*
    June 23, 2008 2:23 pm

    Yup. Here it is:
    To produce 1 gallon of corn ethanol, farmers use at least 1.8 gallons of fossil fuels. That’s a combination of the fossil fuels used in fertilizer and the fossil fuels used to power tractors. I’m not sure exactly how it breaks down into fertilizer and fuel.

  4. Abby McCarthy permalink
    June 24, 2008 1:37 am

    Hey –
    Thanks loads- can you cite a source on that, or is it in the aforementioned Chapter 3?

  5. maukamakai permalink*
    June 24, 2008 2:22 pm

    It could very well be in Chapter 3, but Chapter 3 is $25 so I wouldn’t know. Here’s the source I used:


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