Thursday, March 30, 2006

This post powered by ethanol.

The peak oil doom-merchants love to say "ethanol is a net energy loser! It takes more than a gallon of gas or diesel to produce a gallon of ethanol! We're doomed!"

Yesterday, I found out that this is just FUD. In hindsight, I am amazed that I was gullible enough to believe them without investigating further, but it just goes to show... Don't believe everything you read on the internet.

Here are two excellent rebuttals to the "ethanol is an energy loser" meme:



And here's my summary of what's wrong with the doom argument:

The claim that ethanol is a net energy loser seems to be based on a recent study by David Pimmental. I won't go into the full laundry list of what's wrong with his study (see the first link above) but suffice it to say: He assumes 1979 ethanol refining technology. He commits various fallacies regarding how much energy it takes to fertilize and harvest the corn. He mistakenly assumes that all of the corn harvested is used to make ethanol - in reality the byproducts of the conversion process include plant protein and corn oil, both of which we have ample use for (human and animal food).

And that's not even going into the small matter of fact that corn is not the only ethanol feedstock, nor is it even remotely the best! Ethanol can also be produced from plant cellulose, which means that native prairie grasses can be used to make ethanol. These plants once covered substantial portions of the great plains, and so they obviously don't need pesticides, fertilization, or irrigation, if polycultured, are perrenials, so they don't require the energy investment of replanting every year. The biggest benefit, of course, is that these sorts of feedstock produce far more yield per acre than corn, rendering all the ultra-pessimistic land-use estimates of the doomers null and void.

Doomers like to say that peak oil isn't about technology, it's about energy, and the foolish optimists conflate the two when saying that technology will save us. But they then completely ignore technology, which will ultimately make fools of them. The efficiency of ethanol-producing techniques has substantial room to grow, and is nowhere near running into any of the laws of physics that the doomers love to quote.

Just think about the energy involved: I've read plants are about 2% efficient at converting sunlight into chemical energy. Sounds pretty crappy. Let's assume that ethanol production from plants is 1% efficient. Also pretty crappy. The total efficiency then is 0.02%. Sounds shitty, huh? But, the average solar irradiation per square meter at north american latitudes, over a full 24 hour period, is maybe 200 watts. (I got this assuming 1000 watts for 5 hours and 0 watts for 19 hours). So, the average power production of an ethanol agriculture utilizing 55 million acres is about 9 gigawatts. That's a hell of a lot of power. Of course I just pulled that model out of my ass, but I find it completely impossible to believe that it's going to be a net energy loser.

If you don't believe my analysis, look at brazil: The unsubsidized price of ethanol in brazil is much cheaper than gasoline. (source: http://www.khoslaventures.com/presentations/Biofuels.Apr2006.ppt) If they have to burn two gallons of gas to make a gallon of ethanol, how the hell can ethanol be cheaper than gas?

People like Jim Kunstler rebut these arguments by swearing, and saying "people are letting themselves be deluded into thinking we can run all our cars on ethanol forever". This is just suppressed american puritanism at its best. Cars are evil, and the evil will be purged.

3 Comments:

At 3:04 PM, Blogger Iron Eagle said...

Another factor I'm curious about is whether we'd need fewer gallons of ethanol than we need of gasoline. The reason I ask is because ethanol is a superior racing fuel, because an ethanol/air mixture can be compressed more than a gasoline/air mixture before it detonates (knocks), and ethanol cools more when it's atomized (i.e. fuel-injected) than gasoline does.

The first property makes it possible to design engines with higher static compression ratios that hence extract more energy from combustion. Due to the gas law, the second property means that a given engine can suck in more air/fuel charge, which is helpful when you're optimizing for peak output, but not so helpful in optimizing for efficiency.

Have you seen any discussion of how our demand for ethanol would/could be different than our demand for gasoline?

 
At 3:10 PM, Blogger emtel said...

i do know that the heat content per gallon of ethanol is less than that of gasoline. Supposedly, existing flex-fuel vehicles get worse per-gallon mileage with ethanol, though the "dollarage" improves due to the cheapness of ethanol.

 
At 3:23 PM, Blogger Iron Eagle said...

Hmm, then it's likely that the racing engines I described burn ethanol faster (by volume) than similar gasoline ones.

 

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