Environmental Engineering Reference
In-Depth Information
fossil fuel comes with a forbidding environmental price tag. Coal plants are
more polluting and less costeffective compared to state-of-the-art natural
gas plants. At least 49 GW of existing coal power plants in the United States
can be retired and replaced with natural gas plants or even with wind-power
plants with significant cost savings as well as improved environmental
emissions (UCS, 2012).
There is a good justification for closely examining large-scale coal burning,
especially without capture or sequestration of CO
2
as a future strategy for
generating energy. Coal-fired power plant emissions include particulate
matter, sulfur dioxide (SO
2
), and nitrogen oxides (NOx) as well as mercury.
They are already the largest source of mercury (Hg) pollution in the United
States;theemissionsfromUSplantsin2009exceeded134,000lbs.Organic
mercury is already present in human blood though at levels below those
associated with health effects. Ingestion of mercury-contaminated food can
result in serious neurological damage in humans especially children
(Counter and Buchanan, 2009). A national standard on limiting mercury
emissions from power plants is presently being drawn up by the USEPA; it
is already being challenged by the power industry.
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1.1.1.3 Gas
Aboutaquarterofthedomesticaswellasglobalenergyconsumedisderived
from natural gas where the proven global reserves have been estimated to
meet about 64 years of production. In recent years, the domestic production
of natural gas has increased, and in 2011, the United States was the leading
producer of natural gas in the world. The dramatic growth of natural gas
industry has been even more apparent in China with investment in upscale
technologies for its cost-effective exploitation. Reserves are the largest in
these two countries. Interestingly, in the first half of the twentieth century,
natural gas was thought of as a virtually useless by-product of oil
production! Natural gas is often hailed as an example of cheap “green
energy,” but methane (the primary component of natural gas) that escapes
during the drilling process is a potent global warming gas.
Extraction of shale gas by fracturing the porous rock (fracking) involves
pumping a slurry of water, sand, and chemicals into the rock to crack them
to release the trapped gas. The process requires drilling vertically, often
through aquifers, and horizontally below them. The slurry pumped into the
ground has additive chemicals (such as acids, surfactants, and methanol)
