65. The U.S. Energy Security and Independence Act of 2007 required that 15 billion gallons of ethanol and other renewable fuels be blended with gasoline in 2015. In the United States, corn is the main source of ethanol. What percentage of total arable U.S. land (land that can be planted to crops) would be needed to raise that much corn ethanol? The contiguous United States (without Alaska or Hawaii) has hectares of arable land, which could yield about 400 gal/acre of ethanol.
65.
The arable land totals 667 million acres, which could produce gal; the 15 billion gal required would be of the total. In 2014, actual acreage planted to field corn was 92 million acres; at 400 gal/acre, that would supply 37 billion gal, so the ethanol would require about 40% of the corn crop.