Energy - Environmental Science - page 294

Coal-fired
electricity

Arabia. If a pipeline is built to transfer some of this
synthetic crude oil from western Canada to the north-
western United States, Canada could greatly reduce
future U.S. dependence on oil imports from the Mid-
dle East and add to Canadian income. However, even
if everything goes right, this will not provide a signif-
icant amount of oil for the United States for 10-20
years.
Extracting and processing oil sands has a severe
impact on the land and produces much more water
pollution, much more air pollution (especially sulfur
dioxide), and more CO 2 per unit of energy than ex-
ploiting conventional crude oil.
Oily rocks are another potential supply of heavy
oil. Such rocks, called oil shales (Figure 13-11, left), con-
tain a solid combustible mixture of hydrocarbons
called kerogen. It can be extracted from crushed oil
shales by heating them in a large container, a process
that yields a distillate called shale oil (Figure 13-11,
right). Before the thick shale oil can be sent by pipeline
to a refinery, it must be heated to increase its flow rate
and processed to remove sulfur, nitrogen, and other
impurities.
Estimated potential global supplies of shale oil are
about 240 times larger than estimated global supplies
of conventional oil. But most deposits are of such a
low grade that with current oil prices and technology,
it takes more energy and money to mine and convert
the kerogen to crude oil than the resulting fuel is
worth. Producing and using shale oil also has a much
higher environmental impact than exploiting conven-
tional oil.

286%

Synthetic oil and
gas produced
from coal

150%

100%

Coal

92%

Oil sand

86%

Oil

58%

Natural gas

17%

Nuclear power

Figure 13-10 Natural capital degradation: CO 2 emissions
per unit of energy produced by various fuels, expressed as
percentages of emissions produced by burning coal directly.
These emissions can enhance the earth's natural greenhouse
effect (Figure 5-5, p. 82) and lead to warming of the tropo-
sphere. (Data from U.S. Department of Energy)

x

H OW W OULD Y OU V OTE ? Do the advantages of relying
on conventional oil as the world's major energy resource
outweigh its disadvantages? Cast your vote online at
http://biology.brookscole.com/miller11.

Science and Economics: Heavy Oils
from Oil Sand and Oil Shale
Heavy oils from oil sand and oil shale could
supplement conventional oil, but there are
environmental problems.
Oil sand, or tar sand, is a mixture of clay, sand, water,
and a combustible organic material called bitumen —a
thick and sticky heavy oil with a high sulfur content.
Oil sands nearest the earth's surface are dug up by gi-
gantic electric shovels and transported by 270-metric-
ton (300-ton) trucks to huge cookers. There they are
mixed with hot water and steam to extract the bitu-
men and convert it into a low-sulfur synthetic crude
oil suitable for refining.
Northeastern Alberta in Canada has three-fourths
of the world's oil sand resources, about one-tenth of
them close enough to the surface to be recovered by
surface and underground mining. Improved technol-
ogy may allow extraction of twice that amount within
a decade.
Currently, these deposits supply about one-fifth
of Canada's oil needs, and this proportion is expected
to increase. Because of the dramatic reductions in de-
velopment and production costs, in 2003 the oil in-
dustry began counting Canada's oil sands as reserves
of conventional oil. As a consequence, Canada has
15% of the world's oil reserves, second only to Saudi

Figure 13-11 Natural capital: oil shale rock (left) and the shale oil
(right) extracted from it. Big U.S. oil shale projects have been can-
celed because of excessive costs.