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If those rough estimates are accurate it would take about 92.8 percent of all the farmland in the United States to produce that many gallons of ethanol. Notice though that this does not replace all the energy consumed in a year. There is also significant additional consumption of energy from natural gas, coal, nuclear and other non renewable energy sources. Other issues include whether the gallons per bushel is gross or net. Since no sources were clear on the matter I assume gross and that net after deducting fuel used in harvesting and processing is a little lower. "Gallons used" represents total sales whether for transportation or various manufacturing processes including the production of electricity or other energy. Another thing is the meaning of "bushel." I assumed the "bushel" in bushels/acre and the "bushel" in gallons/bushel to be the same but might not be. One might include the cob the other not. Be careful in your own research. Ask necessary questions and maybe you will get the answers.