I did some calculations on corn ethanol. Switchgrass may yield 2 to 2.5 times the ethanol. Prepare to be amused.

1 acre = 328 gallons ethanol
1 sq mile = 640 acres
1 sq mile corn = 209,920 gallons ethanol
1 gallon ethanol = 84,200 btu or 24.67 Kwhr
1 sq mile corn = 17.675 billiion btu or 5.179 gigawatt hours annually

US energy consumption of natural gas, petroleum, and electricity = 24,413 TWhrs = 24,413,000 gigawatt hours

It would take 4.7 million square miles of farmland for corn ethanol to supply the current US demand for all combined forms of energy (electricity, natural gas, and oil). The USA is 3.5 million square miles. What a joke!