The USDA just raised its projection for how much corn it expects the ethanol industry to burn through this year by 150 million bushels. It now expects a total of 4.1 billion bushels of corn to be turned into liquid fuel. 

That’s about double the amount of corn that went to ethanol in 2006 (2.1 billion bushels), and a third again as much as last year (3 billion bushels.)

The USDA now expects the ’08 corn harvest to hit 12.3 billion bushels. That means that 33 percent of the U.S. corn harvest will go to car fuel.

The USDA projects that farmers will harvest 79.3 million acres of corn this year. That means 26.4 million acres of prime U.S. farmland are devoted to ethanol — a land mass roughly equal in size to the state of Tennessee.

How else can we contextualize this diversion of food crops into fuel?

Here’s another way. Check out this U.S. Grains Council chart on world corn production. According to the USGC, the United States typically produces more than 40 percent of the world’s corn. So by taking a third of our total crop, our ethanol program alone will siphon off about 13 percent of all the corn grown in the world.

The USGC says that China is the globe’s second-most-prolific corn  producer, typically churning out 5.5 billion bushels. Thus the corn we’re devoting to ethanol (4 billion bushels) equals more than 70 percent of total Chinese production.

Brazil is the third-largest producer, with 1.6 billion bushels, and the entire European Union produces about 1.9 billion bushels. That means that our ethanol industry will use more corn than the total production of Brazil and the European Union combined.

Let’s think about fertilizer use now. Nitrogen fertilizer is a huge emiter of nitrous oxide, a greenhouse gas 310 times more potent than carbon. Corn, in turn, is a huge user of nitrogen fertilizer. This USDA report [PDF] tells us that in 2005, U.S. farmers used about 12 million tons of nitrogen fertilizer, and that “42 percent of total nitrogen used during the period was attributed to production of corn.”

So that tells us that in a typical year, the corn crop takes up about 5.2 million tons of nitrogen. If we use a third of that crop for ethanol, we’re using 1.7 million tons of nitrogen. That’s actually a low estimate for 2008, because a) farmers devoted more land to corn this year than they did in 2005; and b) the June floods washed away untold amounts of fertilizers, forcing many farmers to reapply.

Anyone out there have any idea of the greenhouse gas implications of 1.7 million tons of nitrogen fertilizer? Please reply in comments. 

Note that burning through this titanic amount of corn only offsets a few percentage points of total gasoline use. Also note that under the federal Renewable Fuel Standard, ethanol will suck up even more of next year’s crop — and even more for every year after that until 2015.