Wednesday, June 21, 2006

Doing the math

Sorry to harp on the peak oil thing. I think I lose half my audience every time I bring this up. When did I turn into an activist? I'm just having a hard time shaking the idea of the end of life as we know it...

Eleutheros had a post titled "Do the Math", in which he stated that if every kernel of corn* grown worldwide were turned into ethanol, it would amount to about four days' worth of fuel for the US. He didn't include his calculations, so I thought I'd try to "do the math" myself.

"The math" in this case is just some back-of-the-napkin stuff - mostly unit conversions. Nothing fancy. If you trust my math skills, feel free to skip to the end. Note that my math skills are pretty shaky...

My sources are just whatever came up first on Google.

So here goes:

According to this link, there were 598 million metric tons of corn produced globally in 2002. (That was the first year I came across. Let's assume it's typical.)

598 million metric tons * (2204.6 lbs/metric ton)
...converts to 1.3 billion lbs of corn.

A bushel of corn is currently defined as 56 lbs.

1.3 billion lbs * (1 bushel/56 lbs)
...converts to about 23.5 million bushels of corn.

According to this article, a bushel of corn can produce 2.7 gallons of ethanol.

23.5 million bushels * (2.7 gallons/bushel)
...tells us that 63.5 million gallons of ethanol could theoretically be made from all the corn grown globally in one year.

According to this, a barrel of petroleum has 42 gallons. After refining, it could be made into about 19.5 gallons of gasoline.

So if we say that 1 gallon of ethanol can replace one gallon of gasoline, then

63.5 million gallons * (1 barrel / 19.5 gallons)
comes to 3.2 million barrels.

(The 1-to-1 ethanol-to-gasoline ratio is likely flawed, but this is
getting too complicated. Let's just say 1-to-1.)

According to this source, the United States currently uses 20 million barrels of oil per day.

3.2 million barrels * (1 day / 20 million barrels)
amounts to 0.16 days.

So if we can stop using corn for livestock feed, corn starch, corn syrup, corn oil, corn chips, corn stoves, corn bread, popcorn, candy corn**, corn on the cob, corn dogs, creamed corn... er... sorry, I was channeling Forrest Gump for a second...

If we use all of the corn grown in one year for making ethanol, and production is still propped up by using current (petroleum-heavy) farming practices, it would keep the U.S. running for just under four hours. Or, if you prefer, Argentina could last almost a week. Or we could supply Togo with their fuel needs for the entire year.

Feel free to check my math. I'm sure this must be due to rounding error.

* - Corn = maize. I know in some places "corn" is a generic grain term.
** - I checked. Corn syrup is an ingredient in Candy Corn


At 6/24/2006 7:40 AM, Blogger Eleutheros said...

e4, your math is essentially correct. But the only bit I'd add is that there is no 1 to 1 correspondence of ethanol to gasoline. Ethanol has only 67% of the energy in a gallon of gas. Your four hours is less than three.

Moreover, ethanol cannot be stored nor transported in piplelines like gasoline because any time it is exposed to atmospheric moisture, it wicks it up and suspends it.

The state of Iowa, which produces more corn than anywhere else in the world and has a modest population, could itself not be motor fuel self-sufficient on its own corn,

At 6/24/2006 11:18 AM, Blogger barefoot gardener said...

Yikes! E4, this calc is scary in the extreme. DH argues that the US cannot possibly use that much oil, which caused quite a discussion around our place about the population of the US and our gluttonous overuse of resourses. I am finding more and more that I side with you, we seem to be facing the end of the world as we know it. It's not just oil, there are so many other issues contributing to the situation. I think big changes are on the horizon for the US. I say good for you for being aware and posting your ideas about it. We as a country need to be aware of this if we are to do anything about it. Unfortunately, I think you are right in that many people just don't want to hear it.

At 6/25/2006 4:16 AM, Blogger Morgan said...

wow higher math.

Me impressed and stuff

At 6/25/2006 11:39 PM, Blogger madcapmum said...

3 hours, huh? Sounds like everyone would be spending a lot more time at home.

At 6/26/2006 7:57 PM, Blogger Mia said...

My understanding is that the oil it takes to produce ethanol leaves us barely ahead anyway. May I also remark that I HATE CORN and all of it's accompanying filth and uses.

I do hear that they have an excellen new biofuel that can be made without chemicals and with little or no oil involvement from prairie grasses such as switchgrass. Now THAT'S worth looking into.

At 6/26/2006 8:57 PM, Blogger Eleutheros said...

The Energy Retruned On Energy Invested for corn ethanol is about 1.25 and this is only if you include using the spent mash as animal feed, adding energy cost of replacing that feed into the formula. On a purely motor fuel basis, you use more energy producing ethanol than the ethanol contains.

Switchgrass doen't make oil fuel, it makes ethanol by means of breaking the cellulose into sugar.

Switchgrass has to be boiled, treated with enzymes (which consume energy to produce) and the resulting 'wort' has to be fermented and distilled. Depending on how much engergy used to produce it you are willing to ignore, it's EROEI is as low as .69.

Doing the math as e4 has done for corn ethanol shows that to use cellulose as the source material for ethanol, it would require one tenth of ALL biomass on the earth to supply the motor fuel consumed now in one year.

At 6/27/2006 12:18 AM, Blogger e4 said...

I think biofuels are an interesting niche, but a bit of a dead-end on a large scale.

If you think about it, petroleum is essentially stockpiled (albeit dirty and ancient) biofuel. We've consumed eons of this "stockpiled biofuel" in just the last hundred years or so. One year's worth of biofuel, from whatever plant matter you like, is going to be hard pressed to match that kind of energy.

(...despite the new new "Live Green. Go Yellow." campaing from General Motors... Go yellow? Am I the only one who thinks that's a terrible slogan? Maybe even worse than UPS's "What can Brown do for you?")

Sorry, I'm feeling cynical today.

At 6/27/2006 8:28 PM, Blogger roybe said...

We have an ethanol industry in queensland from sugar cane. There is an ethanol blend fuel available at service stations over here, it seems to be gaining more acceptance now.

At 6/30/2006 9:22 PM, Blogger Beo said...

Mia is correct that it takes more btu's to make ehtanol from corn thanyou get from the final ethanol. However, there are enough by products of the corn to make it have a net energy gain if you can find uses for them all. The problem is cellulose or corns lack thereof. Switchgrass (which also happens to be a perrenial, native prairie grass for the midwest[no tilling, no erosion, theoretically no herb/pesticides] has gobs of cellulose and is net energy positive by itself and sugarcane is also a good choice for those more tropical than us. Too many $300,000 dollar combines out there bought with gov corn subsidies to see us replanting the prairie any time soon.

My dream is a flexible fuel hybrid-running my Insight on switchgrass fuel would put me on sustainability overload!


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