Environmental Engineering Reference
In-Depth Information
However, fossil fuel will likely be in good supply in the United States in the
immediate future because of aggressive policies in place to exploit shale oil
and gas reserves. These include particularly the shale gas (within layers of
rock) and “tight oil and gas” trapped in low-permeability rock formations.
Hydraulic fracturing or “fracking” might be the only way to exploit these
presently inaccessible resources. The potential for “tight oil” and “tight gas”
is so high locally that within the next few years, the United States could
well be the leading oil producer in the world (replacing Saudi Arabia) and
soon thereafter a net energy exporter. In spite of its attractiveness, however,
hydrofracking is associated with serious environmental risks. Some of these
are its link to earthquakes, the relatively high water demand for the process,
limitations of environmentally acceptable disposal choices for spent process
wastewater, risk ofgroundwater contamination, and high potential forGHG
release. Despite the opposition from environmental groups, fracking is
gaining pace in the United States.
Thankfully, the world still has considerable coal and shale gas reserves; the
United States is believed to have 261 billion tons of coal and around 827
trillion cubic feet of shale gas. The United States is presently the second
largest producer of coal, and at the present rate of consumption, reserves
of coal should last the United States about another 500 years. Not only
can coal be burnt to derive power but can also be converted to oil via the
Fischer-Tropsch chemistry. Developed in the 1920s, the Fischer-Tropsch
process converts CO and H
2
(called syngas) into liquid paraffin
hydrocarbons usingtransition metal catalysts. Syngasisobtained fromcoal:
The paraffin produced is upgraded into fuel by hydrocracking into smaller
molecules.
1.1.1.2 Coal
Already, by the mid-decade, 43% of the world's electricity supply was
30%)oftheenergyconsumedin2010wasderivedfromcoal.Atsomefuture
higherlevelofoilprices, theuseofcoaltoproducesynthetic oilmaybecome
cost-effective, and the relevant Hubbert's curve would have been pushed
back a few years or decades into the future. Coal is a cheap direct energy
source for the United States, but this reassurance of a few more centuries of
