Something that isn’t made clear in the text of that presentation: do those total BTU figures include solar energy or not?
Please see the text on p 1. to see where the confusion arises.
Curiosity got the better of me. I had to do the math. Solar Energy input to the field is not included the graph. I was sure it would be huge. I greatly underestimated how much.
You may disagree with some of the input numbers, but I think you will see the result at the end is so large it cannot be included in the numbers.
An acre of U.S. corn yields about 7110 pounds of corn for processing into 328 gallons of ethanol.
77,000 BTUs per gallon of ethanol
http://healthandenergy.com/ethanol.htm
I used 5 kWH/m2/day for the solar energy input.
http://www.nrel.gov/gis/images/us_csp_annual_may2004.jpg
90 day season (just a guess, please correct me)
450 kWH/m2/season
4,070 m2/acre
http://www.onlineconversion.com/area.htm
1,821,085 kWH/acre/season
3,412 BTU/kWH
http://www.onlineconversion.com/energy.htm
6,213,799,475 BTU/acre/season
18,944,511 BTU/gallon of ethanol
246 BTU Solar input per 1 BTU ethanol.
Not a fair comparison in my mind, but they definitely did not include the field's solar input in the numbers.
When you look at it from purely energy input, we should cover the field with solar cells and build lots of batteries. Of course that wouldn't produce distillers grains or winter wheat.
