In order for the United States to reach the grain ethanol cap scheduled for 2016 might require 40% of the 2007 size United States grain harvest.

Europe is likely to have similar problems as the ethanol yield of a bushel of grain is low and 10% of Europes transport fuels is very high.

Global warming is causing Himalaya glacial melt and might shrink rivers in India and China exacerbating the needs of their growing populations.

http://www.earthpolicy.org/Updates/2008/Update71.htm

Using all the grain in the United States each year to make ethanol might satisfy 12 percent of our oil needs, but would create a hell of a food shortage. As if food and gas prices were not bad enough; they might easily get worse unless some sort of change is wrought.

Using the entire corn and wheat harvests (14 billion bushels) to make ethanol would yield about 38 billion gallons of ethanol (2.7 gallons per bushel). The United States used more than 20 million barrels of oil per day. One barrel = 42 gallons. U.S. oil usage was more than 840 million gallons of oil per day; that is about 307 billion gallons of oil per year.