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 United States 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 = 1,000 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 needed to produce 36 billion gallons of biofuel annually, we need to first calculate the total energy that would be produced per year:

36 billion gallons x 3.785 L/gal x 100 MJ/L = 13.686 x 10^14 MJ/year

To convert this to the total amount of farmland needed, we divide by the annual energy production per acre:

13.686 x 10^14 MJ/year / 1000 gal/acre = 13.686 x 10^11 acres

Now we need to convert this to square miles:

13.686 x 10^11 acres x 1 mi^2/640 acres = 21.382 x 10^8 mi^2

Finally, we can calculate the fraction of total farmland in the U.S. that this represents:

21.382 x 10^8 mi^2 / 1.4 x 10^6 mi^2 = 0.04 = 4.0%

Therefore, we can conclude that about 4.0% of farmland in the United States would be needed to meet the goal of producing 36 billion gallons of biofuel annually. This could have a significant impact on other uses of farmland, such as the production of food.

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