Agriculture Reference
In-Depth Information
attack on Iraq in 1991. The U.S. invasion of Iraq in 2003 certainly had energy secu-
rity implications.
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The second serious concern is that greenhouse gases (GHGs) emitted when fossil
fuels are consumed will alter the environment. An estimated 80% of GHG emis-
sions, discharges linked with global warming, are associated with consumption of
fossil fuels. One GHG of much concern is the carbon dioxide formed during burning
of fossil fuels when carbon in the fuel combines with oxygen from the air. In 2004,
an estimated 8 billion metric tons of carbon, previously sequestered in coal, petro-
leum, or natural gas, were emitted into the atmosphere as a result of fossil fuel use.
The atmospheric concentration of carbon dioxide, which had historically been fairly
constant, has risen nearly 20%, from about 315 parts per million by volume (ppmv)
in 1959 to over 377 ppmv in less than 50 years. Research has found that much of the
increase is due to use of fossil energy and has raised concern that elevated levels
of atmospheric carbon dioxide are increasing global temperature and driving other
serious environmental changes. Changes that scientists project, if not averted, may
well have costly consequences and potentially calamitous effects on Earth's climate
and, in turn, on its inhabitants. Changes of concern include sea-level rise from melt-
ing ice that could flood large inhabited areas, loss of glaciers that may cause some
major rivers to cease flowing during portions of the year, and changes in ocean cur-
rents that could significantly alter climates. Some experts feel strongly that unless
carbon emissions are stabilized within a few decades, irreversible climatic changes
will begin to occur.
To reduce carbon emissions, clean technologies that capture and sequester carbon
from fossil fuels, particularly from coal, have been proposed. Unfortunately, carbon
capture is difficult, costly, and unproven. Capture is especially difficult from dis-
tributed uses and users, including from mobile engines such as cars, planes, trucks,
trains, tractors, recreational vehicles, and outdoor power equipment. Capture from
large point sources, such as power plants, is potentially feasible but has not been com-
mercialized. Sequestration is also a challenge. Because the quantities of carbon are
large, finding locations and procedures for safe, sustainable, and economical seques-
tration is difficult. Sequestration sites include soil, where the carbon could increase
organic matter and enhance soil quality and productivity, and oil fields, where inject-
ing carbon dioxide could enhance oil recovery. Other sites proposed are aquifers,
caverns, and the ocean; however, the sustainability of sequestration in these sites is
not proven. Certainly, planting more trees would also remove and store considerable
carbon. Possibly the best method, however, to ensure safe sequestration of the carbon
in unrecovered oil, natural gas, and coal deposits is to leave those materials where
they are—in the earth unused. This also conserves these fossil natural resources.
In addition to carbon dioxide, other emissions associated with use of fossil energy,
especially coal, are problematic. These include particulate matter, sulfurous com-
pounds, nitrous oxides, and mercury. Fortunately, most of these can be controlled by
use of technology that cleans the fuel either before it is used or with aftertreatment
of combustion gases.
