Environmental Engineering Reference
In-Depth Information
imported sugar mean that no one can afford to import foreign sugar and
turn it into ethanol the way that oil refi ners import crude oil from the
Middle East to make gasoline. Moreover, Congress imposed a tariff of
54 cents per gallon on sugar-based ethanol in order to protect corn
producers from competition. Analysis has determined that if the tariffs
were removed, prices would fall by 14 percent and almost 300 million
more gallons of ethanol would be used in the United States. Former
President George Bush proposed eliminating the ethanol tariff in 2006,
but Congress killed the proposal. President Obama voted to keep the
tariff when he was a senator, and the sugar quotas seem to be sacrosanct,
so it is unlikely that sugar-based ethanol will appear in the United States.
Corn-based ethanol contains only two-thirds as much energy as
gasoline. So even if it costs the same at the pump, it will not take
you as far on the road. In addition, low-ethanol blends such as 10
percent ethanol in gasoline increase smog levels because the addition
of ethanol increases the ease of evaporation of the fuel, so more of
the hydrocarbons evaporate into the air and create smog. But as is
common in political hassling, scientifi c realities take a back seat to
successful political lobbying.
Biodiesel
About 23 percent of the fuel used in America's motor vehicles
is diesel, almost all of it in commercial trucks, ships, and farm machinery
rather than cars.
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Because of its chemical composition and molecular
structure, corn kernels are not suitable as a feedstock for the production
of diesel fuel. Soybeans are. The relative percentages of farmland devoted
to corn and soybeans fl uctuate yearly, but both are increasing as farm-
land previously idled for environmental or other reasons is brought back
into production. Biodiesel is easy to manufacture and has a high net
energy balance; soybean-biodiesel produces a 93 percent energy gain
versus 25 percent for corn-ethanol.
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And biodiesel emits 78 percent less
carbon dioxide emissions than petroleum diesel.
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Soybeans are not the only vegetable materials suitable as a feedstock
for biodiesel. Practically any type of vegetable oil or animal fat can
be used, a fact that has not been lost on the large meat corporations.
Animal fats are cheap and plentiful. The largest chicken producers—
Tyson Foods, Perdue Farms, and Smithfi eld Foods—have established
renewable-energy divisions. Tyson Foods is the nation's biggest producer
of leftover fat from chicken. Maybe one day you will go to McDon-
ald's and order Chicken McNuggets, fries, apple pie, and 10 gallons
of fuel.
