ethanol from corn

I read an article in the NY Times* on E85, the alternative fuel that contains mainly ethanol (grain alcohol). The article suggested that E85 might be a renewable alternative to petroleum. After all, many US cars (including my own) can already burn E85! I disagree. I'm afraid E85 is not going to solve the oil crisis - or at least not anytime soon. Here's why:

The US consumes an enormous amount of petroleum! Our consumption in 2004 was 20.52 million barrels per day, or 7.5 billion barrrels per year. At 0.136 tonnes per barrel of oil, that's 1.02 billion tons per year.

A lot of lip service is given to producing ethanol from agricultural wastes. In theory, it can be done. The straw that's left over when grain is harvested contains cellulose. That's a carbohydrate, so fermenting it into ethanol should be possible. But that's mostly theory. Today almost all (98%) ethanol is produced using the grain, itself. And grain, though renewable, is scarcer than oil!

US 2004 corn (maize) production was 265 millions tonne. US 2004 wheat production was 180 millions tonne. So if we converted it all to ethanol with 100% efficiency, we would have 445 million tons, or about 45% of US petroleum consumption. But then what would we eat!

The actual conversion rate that has been achieved industrially is 2.5 gal per bushel (a bushel weighs 25 kgs). If I've done my arithmetic right, that's an efficiency of 18%. So we're really talking about using all of US grain production to replace 8% of US petroleum consumption. We better start A) eating light and vegan; and B) designing 200 mile per gallon cars!

US ethanol production for 2004 is estimated at 3.5 billion gallons, which is 10.5 million tonnes. That's about 4 days supply of petroleum. Somewhat less than 10% of the US corn crop is used to make it. While production has been increasing steadily, it has a long way to go before it has much of an impact on the oil crisis.

*The New Prize: Alternative Fuels, by Danny Haki, New York Times, Sept. 10, 2005.