Carbon Footprint

I have heard many times that ethanol uses more fuel than you get out of it, or something of the sort. Hear are the real numbers. I looked these basic numbers up myself. You can too.

According to the University of Illinois, the cost of growing an acre of corn in the US will be $530 in 2009[1]. Of that $88 is spent on power, assuming it is all fuel, at $2 per gallon, thats 44 gallons of fuel, or 968 pounds of CO2 released into the air. That acre of corn will make 350 [2]gallons of ethanol. Or 2.7 lbs of CO2 per gallon, that is 13% of what a gallon of gasoline makes. A carbon reduction of 87%.

Footprint total 2.7lb/gallon

But there is more. I have not talked to you about the duel use aspect of corn based ethanol, but suffice to say that most US corn is grown as animal feed and the byproduct of making ethanol from corn is high quality animal feed. You get to make animal feed and fuel from the same crop. So lets cut that carbon foot print in half, since it is being shared with your hamburger.

Footprint total 1.35lb/gallon

Okay, so growing is not the only energy input, lets talk about shipping corn...

A semi holds 910 bushels of corn[3] thats enough corn to make 2400 gallons of ethanol. The average semi gets 5mpg or 4.4 lbs of CO2 per mile or .00183 lb of CO2 per gallon of ethanol for every mile the corn travels...or....if the corn travels 1000 miles to the ethanol plant of its choice, the resulting ethanol will have 1.8lb of CO2 per gallon because of transportation.

Footprint total 3.15 lb/gallon

But there is also energy involved in the distillation process. You make ethanol like you make moonshine. Ferment (like beer) distill (like whiskey). To bring a kg of water to boil is 357kJ in American thats .38kilowatt hours per gallon. You have to heat 10 gallons of water to get one gallon of ethanol, so 3.8kwh...you have to add to this .7kwh to vaporize the ethanol...So now we have 4.5kwh per gallon of ethanol. assuming 1.7pound per kwh thats 7.65 lbs per gallon. But we are not considering something. Ethanol plants are there to make money, they do not waste energy because that is wasted money. So lets assume that the plant recovers half of its energy so now we have 3.8 pounds per gallon(and I will bet ethanol plants recovery way more than that).

Footprint total 6.95lb/gallon
This is a third of gasoline.

Some more numbers....if you convert a gas car to run on ethanol you will get less mpg. Lets look at the average American car that gets 22mpg. On ethanol lets say its a really bad conversion and it get 15mpg. On gas, its a lb of CO2 per mile. On ethanol its .46 lb/mile. This is that same carbon footprint as getting 47mpg on gas.

Let me point out that we did not take into account the following

Using biofuels for farming (-2.7lb/gallon)
Using biofuels for transportation(-1.8 lb/gallon)
Using renewables for distillation(-3.8 lb/gallon)

If we do all of these, things, there is no carbon footprint for a gallon of ethanol. Chew on that!



[1] http://www.farmdoc.uiuc.edu/manage/newsletters/fefo08_13/fefo08_13.html
[2]http://www.pww.org/article/articleview/11474/1/383
[3] http://www.iowacorn.org/User/Docs/Corn%20Use%20Stats%20and%20Facts.pdf