In a Reuters news report dated February 3, 2010, President Obama is quoted as saying, "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." Use the following information to estimate the fraction of farmland in the U.S. that will be needed to meet this target in order to assess the impact on other uses of farmland, such as the production of food. (M = mega = 10⁶) Farmland in the U.S. = 1.4 * 10⁶ square miles
Energy density of biofuels = 100 MJ/gal
Annual biofuel production from farmland = 1000 gal/acre
640 acres = 1 square mile
1 gal = 3.785 L
Mass density of biofuels: 800 g/L

Question

Quizplus · Accepted Answer

To find the fraction of farmland required, we need to first calculate the total amount of biofuels needed to be produced annually:
36 billion gallons/year x 3.785 L/gallon = 136.86 billion L/year

Next, we need to find the total land area required to produce this amount of biofuels:
136.86 billion L/year ÷ 1000 gal/acre ÷ 800 g/L = 170,825,000 acres

Finally, we can find the fraction of farmland needed by dividing this area by the total farmland in the US:
170,825,000 acres ÷ 1.4 billion acres = 0.0406 or 4.0%

Therefore, the best choice is C) 4.0%.

In a Reuters News Report Dated February 3, 2010, President