lecture 6 - Biofuels Our Future Assume biofuels = ethanol...

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1 1 Assume biofuels = ethanol. Assume 1000 gallons of ethanol per acre. 640 acres = 1 square mile Assume 1 crop per year. Assume we need 1x10 14 MJ of energy/year. About 25% of the global total The energy density of ethanol is 86 MJ/gal. How many square miles of farmland are needed to meet this demand with biofuels? Biofuels – Our Future? A) >> 10 6 B) about 10 6 C) << 10 6 2 Compare with Total land area of US = 3.4x10 6 sq mi Current farmland in US = 1.4x10 6 sq mi Area of Iowa = 5.6x10 4 sq mi miles sq 1.8x10 acres 640 mile sq 1 gal 1000 acre 1 MJ/gal 86 MJ 1x10 6 14 Biofuels Bottom Line: 5 to 10% max
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2 3 Today To Do Use quantitative reasoning skills to critical assess information regarding national energy policy. Explain what is meant by the term entropy . Explain why some processes and chemical reactions occur spontaneously. Use the relationship involving energy flow, the change in entropy, and temperature appropriately ( S =q/T). 4 Reuters, Feb. 3, 2010 “Biofuels represent one renewable energy source …Obama said, ‘By 2022, we will more than double the amount of biofuels we produce to 36 billion gallons, which will decrease our dependence on foreign oil by hundreds of millions of barrels per year.’” Give me a number, how many barrels of oil are equivalent to 36 billion gallons of biofuels (e.g. ethanol)? What fraction of our total energy demand in 2022 does this represent? What is it going to cost in terms of subsidies, increased taxes, and increased prices for food?
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3 5 What are the consequences? Price of Corn 6 Good for Professor Hanson’s friends, Joy and Myron Kuhlman, who farm 2000 acres of corn in South Dakota!
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4 8 Rudolf Clausius German Physicist 1822 - 1888 Energy, Enthalpy, & Entropy These words come from the Greek.
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lecture 6 - Biofuels Our Future Assume biofuels = ethanol...

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