Page 589 - Environment: The Science Behind the Stories

Area of corn that
would need to be
Area of corn grown if ethanol
grown in the were to replace all
U.S. today gasoline in U.S.

FIGURE 20.19 Growing corn to produce ethanol uses up a
great deal of land. To produce enough ethanol to replace all
gasoline used by U.S. drivers, the United States would need to
more than quadruple its area planted in corn.

ethanol is variable and controversial, but recent estimates
place it around 1.3:1 (see THE SCIENCE BEHIND THE STORY,
pp. 590–591). This means that to gain 1.3 units of energy
from ethanol, we need to expend 1 unit of energy. The EROI
of Brazilian bagasse ethanol is considerably higher, but the
FIGURE 20.18 Some gas stations offer biofuels. This station extremely low ratio for corn ethanol makes this fuel ineffi-
in New Mexico sells a 20% biodiesel blend (left pump), an 85% cient. For this reason, many critics do not view corn ethanol
ethanol blend (center pump), and a standard 10% ethanol blend as an effective path to sustainable energy use.
(right pump).

need to expand its already immense corn acreage by more than If we substitute ethanol for gasoline,
four times (FIGURE 20.19). FAQ won’t that solve most of our problems
Even at our current level of production, ethanol already with oil dependence?
competes with food production and drives up food prices. In the United States, government subsidies for corn-based
Fully 40% of the U.S. corn crop today is used to make etha- ethanol have been politically popular, and many people
nol. Some by-products of ethanol production are used in live- believe that the more ethanol we produce and substitute
stock feed; with this accounted for, 28% of the U.S. corn crop for gasoline, the better off we’ll be. Increasing the propor-
goes solely toward ethanol. As farmers have shifted more tion of ethanol in gasoline does indeed help to conserve oil
corn crops to ethanol, corn supplies for food have dropped. and reduce reliance on foreign imports. However, obtain-
Skyrocketing prices in 2008 made it difficult for the poor to ing the amount of corn ethanol needed to replace gasoline
afford food, and protests and riots ensued in many nations. In entirely would require that impractically large amounts of land
Mexico, where corn tortillas are emblematic of the national be converted to corn production. Moreover, so much corn
cuisine, working-class citizens found themselves struggling to would likely be diverted from food to fuel that food prices
buy their staple food, and protests erupted across the country. would rise sharply. This is why researchers are studying other
In 2012, as drought cut into U.S. corn production, interna- plants as more efficient sources of ethanol and are trying to
tional leaders urged the United States to cut back its ethanol develop ways of producing cellulosic ethanol from crop and
production so as to free up more corn for export to nations in forestry wastes.
need of food.
Growing corn for ethanol also requires substantial inputs
of fossil fuel energy (for operating farm equipment, making Biodiesel powers diesel engines
petroleum-based pesticides and fertilizers, transporting corn
to processing plants, and heating water in refineries to distill Drivers of diesel-fueled vehicles can use biodiesel, a fuel
ethanol). Thus, simply shifting from gasoline to corn ethanol produced from vegetable oil, used cooking grease, or animal
for our transportation needs would not eliminate our reliance fat. The oil or fat is mixed with small amounts of ethanol or
on fossil fuels. methanol (wood alcohol) in the presence of a chemical cata-
Moreover, corn ethanol yields only a modest amount of lyst. In Europe, where most biodiesel is used, rapeseed oil is
energy relative to the energy that needs to be input. The EROI the oil of choice, whereas U.S. biodiesel producers use mostly
588 (energy returned on investment) ratio (p. 541) for corn-based soybean oil. Vehicles with diesel engines can run on 100%

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