Tuesday, January 31, 2006

Ethanol from Corn or BioMass (more fun with math)

In the SOTU, the President pushed for technology funding to make ethanol from wood chips and grasses. It occurred to me that it had been a while since I did the math on the reality of mass use of E85 (85% ethanol, 15% gasoline). Here are some raw numbers with references. I assume that you could find somewhat different numbers elsewhere. I am not married to these numbers. They are literally the first ones I found in each category. I did reach the same conclusion I did the last time I did this but feel free to attack them if you like.

In 2004, 3.4 billion gallons of ethanol were produced from 1.22 billion bushels of corn. That gives us a yield of 2.78 gallons of ethanol per bushel of corn.

In 2003 American's used 375 million gallons of gasoline per day. Our yearly consumption is, therefore approaching 137 billion gallons of gas (and rising).

Corn production in the US in 2000 averaged 133.9 bushels per acre. That was down a few percent so I will use a nice round 150 bushels per acre.

For calculating the mileage change of moving to E85, I select somewhat randomly a 2WD Dodge Caravan. Some cars had a bigger hit, some smaller, the Caravan of 21mpg on gas (averaging city and highway) versus 15mpg on E85 seemed to be in the middle.

So, now some math! 137B gallons of gas got us (using 21mpg) 2.877 trillion miles of travel. On E85 (using 15mpg) we need 192B gallons of fuel. That fuel is only 85% ethanol so we need 163B gallons of ethanol. We get 2.7 gallons of ethanol per bushel of corn so we need 60.4B bushels of corn. If we get 150 bushels per acre we need to plant 402 million acres of corn. The US current production of corn, wheat and soybeans is approximately 170 million acres.

So forget the cost of producing ethanol as opposed to buying or drilling for oil and refining it. All ethanol production is highly subsidized or it wouldn't be affordable for much of anything. That doesn't matter. Oil could go to $200/barrel and then that cost would look good. We cannot produce enough corn to switch the country to E85 unless we can at least 10 times (and that is probably generous) the miles driven per acre of corn. I am not saying that it won't be possible to get there. I work in the computer world. Every few years I can buy 10 times the compute power at the same price. That isn't happening in this space at this time. Don't get real excited about us being able to switch to E85 in mass while George Bush is still POTUS, and possibly not in his natural lifetime, or mine for that matter.

I am not saying anything about production from wood chips, etc, as I couldn't find good numbers to calculate how much of this "waste" biomass could reasonably be used and how much ethanol that would produce. I am, however, cynical to say the least.

My personal feeling is that putting money into building nuclear plants and funding research for physical battery production and/or hydrogen cell technology would make more sense.

One more political point, it is rumored that one can produce a lot more miles/acre with hemp/marijuana. You never hear a politician pushing those research dollars. And this is not about the "drug war". My grandfather and many others were paid to grow hemp in WW2 by the government. It was used for clothing and rope. As a result, wild hemp is all over the woods where I grew up. You don't want to try to smoke it. It is low in THC and high in tar and other toxins. But it grows huge, fast and close together. You can get a lot of biomass/acre and harvest more than once per year in most of the country. Politics say corn=good, hemp=bad irrespective of the simple scientific and mathematical realities. Politics!


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