Environmental Engineering Reference
In-Depth Information
Fossil Fuels and Crop Production
Few Americans are aware of how dependent farming in the United States
is on fossil fuels. Seventeen percent of the oil we use each year is used
in some aspect of agriculture.
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Most of the fuel, 83 percent, is used in
the production phase, to manufacture fertilizers and pesticides; to power
tractors, cultivation, and harvesting equipment; to dry grain; and to
keep irrigation pumps working. Contrary to popular belief, transporta-
tion and delivering food from producer or processor to the point of
retail sale account for only 4 percent of the food system's greenhouse
gas emissions, even though the produce we eat has traveled an average
of 1,500 miles in eighteen-wheel trucks.
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The fact that New York City
gets its produce from California rather than from the “Garden State”
of New Jersey next door does not add greatly to greenhouse gas emis-
sions. Eating food produced locally means you are eating fresher and
probably more nutritious food, but it has little effect on the production
of greenhouse gases.
The environmental impact of food depends in part on how it was
transported, not only on the distance traveled. For example, trains are
ten times more effi cient than trucks are. So you could eat potatoes
trucked in from 100 miles away, or potatoes shipped by rail from 1,000
miles away, and the greenhouse gas emissions associated with their
transport would be roughly the same.
The largest reduction in emissions from agriculture would come from
a reduction in the consumption of beef and dairy products (fi gure 5.2).
Raising livestock accounts for 18 percent of greenhouse gas emissions—
more than from cars, buses, and airplanes. Producing meat is highly
ineffi cient because it involves eating higher on the food chain. It takes
more energy and generates more emissions to grow grain, feed it to cows,
and produce meat and dairy products for human consumption than to
feed grain to humans directly. Producing a pound of beef creates 11 times
as much greenhouse gas emission as a pound of chicken and 100 times
more than a pound of carrots. And a large percentage of the emissions
associated with meat and dairy production are methane and nitrous
oxide. Compared with carbon dioxide, methane has considerably greater
warming potential but a shorter atmospheric lifetime. Overall, methane
is 20 times as potent as carbon dioxide over a 100-year horizon. Nitrous
oxide, in contrast, is characterized by a relatively low warming effect but
a very long atmospheric lifetime, which causes it to have a global warming
potential 310 times that of carbon dioxide. In 2006, carbon dioxide,
