Could ethanol be the way to go? Tom and Ray investigate the energy pros and cons.

Dear Car Talk

Dear Car Talk | Jul 01, 2006

Dear Tom and Ray:

I've always wondered about ethanol. Seems too good to be true -- you just plant some corn, harvest it, and in no time you have fuel for your car. So I Googled ethanol on the Web. There are tons of Web sites extolling the great benefits of corn-based ethanol as a fuel. Then I found one,, that made the opposite case. You guys went to MIT. Am I missing something? The report on this site says that 131,000 BTUs are needed to make one gallon of ethanol, but each gallon of ethanol only produces 77,000 BTUs. That means we're losing 54,000 BTUs for every gallon we produce. Just wondered if you guys have an opinion. Best regards. -- Charlie

TOM: Yes. But, as usual, it's not an informed one.

RAY: This issue is not only very controversial, it's also ripe for all kinds of obfuscation from various interested parties.

TOM: Right. I mean, if guys with degrees in chemical engineering can't agree on the answer, how the heck are we supposed to know who's telling the truth?

RAY: Wait a minute. You DO have a degree in chemical engineering.

TOM: Yeah. But to understand this issue, I'd have to actually READ all those papers! That would cut into my nap time.

RAY: All right. Well, from what we can tell, the basic issue is this: When you calculate how much energy it takes to produce a gallon of ethanol, you have to make certain decisions. Everybody agrees that you need to include the energy needed to plant the corn, water it, harvest it and convert the starch to alcohol. But, for instance, do you include the energy needed to manufacture the tractors that plow the fields? Scientists disagree about that.

TOM: They also disagree about the other side of the equation. The guy whose study you refer to, David Pimentel of Cornell University, is very well regarded, and has been studying this issue for years. He adds up his calculation of the amount of energy needed to grow the corn and then subtracts the amount of energy you get from a gallon of ethanol, and gets a negative number.

RAY: But there are other credible researchers, like David Lorenz and David Morris of the Institute for Local Self-Reliance, who take Pimentel's research and say yes, BUT, a gallon of ethanol isn't the only thing you get from that corn you grow. You also get stuff like corn oil and gluten feed. So, some of the energy that goes into growing the corn has to be assigned to those other corn byproducts, too. When they do the numbers, the energy ratio of ethanol comes out positive.

TOM: So, the answer is not clear. What everybody does agree on is that ethanol made from plants with more cellulose, like switchgrass or sugar cane, will produce more ethanol per acre than corn will. And that will improve the case for ethanol -- no matter what your starting point.

RAY: People also agree that using ethanol that we grow at home reduces the amount of foreign oil we need, which may eventually mean we don't have to spend billions to send our kids to guard oil fields overseas. So, there's a national security issue here in addition to a scientific one.

TOM: And then there are other questions. Like, how much of this ethanol blitz is a big, wet, government-subsidized kiss to big agri-business and corn growers? Is it ethical to use food to fuel our cars when people are going hungry? And if I'm using the stuff in my Grand Cherokee, will the price of a corn dog go through the roof?

RAY: We don't have the answers, Charlie. But we're eager to see some more light shed on the subject. And we're eager to move beyond corn to more efficient plant-based ethanol and see what kind of scale that could achieve. Meanwhile, pass the butter, will ya?

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