The natural gas industry in the U.S. has been completely
transformed over the last few years, thanks largely to a technology called
hydraulic fracturing (aka 'fracking'). And while few contest the benefits of
natural gas over oil and coal, there are many concerns about the pollution
resulting from this process.
How It Works
Hydraulic fracturing involves the injection of water, sand,
and chemicals to help retrieve natural gas or oil stored in geological
formations. These deposits can exist over a mile below the surface, making
normal extraction of fossil fuels prohibitively expensive due to poor flow
rates through the formations. Fracturing fluid (mostly water, and typically
millions of gallons) is injected into the wells and travels into the
perforations in the rock. High pressure eventually causes the rocks to crack or
fracture, helping release gas (or oil) and stimulating its movement through the
formation.
Hydraulic fracturing is the most common method for natural
gas harvesting, and uses a fracking fluid made of water (about 98.5%), sand or
other proppant (about 1%), and various chemicals (mainly lubricants corrosion
inhibitors, and biocides). Gas fracking, which uses propane, nitrogen, or
another gas as the fracking fluid, is a less common and perhaps less
controversial method, but has not yet been widely adopted.

Credit: The Texas
Tribune
Combining fracturing with techniques for directional
drilling (particularly horizontal drilling) have made it possible to access
sites previously inaccessible. However, this has also stirred controversy about
property rights and whether they apply for the ground 1000 feet below the surface...
The Groundwater
Problem
For a decade now, there has been a growing concern over the
environmental safety of hydraulic fracturing, mostly on the issues of water use
and contamination.
The water issues have been raised and discussed for years.
In additional to the large amounts of water used by the process, many claim
that aquifers and well-waters are being contaminated by methane as a result of
the fracking. Despite the fact that the"burning water" reports are undeniably
true (or rather, burning methane in water, as seen here), the evidence
does not support that the methane-containing water necessarily came from
hydraulic fracturing. The consensus among environmental officials is that the
problem stemmed from new water wells being drilled in soils with high levels of
natural methane, and that some older wells may have been inadequately sealed or
plugged. Unfortunately, the misinformation brought about by opponents of fracking (e.g. the Gasland documentary)
has not helped shed truth on the subject.

In reality, it isn't very likely that fracking fluid or the gas
released from fracturing could travel thousands of feet upward through multiple
types of rock layers to get into shallow aquifers and wells (typically less
than a hundred feet below the surface). As it stands, there have been no
conclusive independent studies that show hydraulic fracturing causes
groundwater contamination. The EPA is still in the midst of its own investigation,
and its findings will not likely be reported until sometime in 2014.
MIT did its own study, titled The Future of Natural Gas. In the 20,000 cases of fracked wells
covered, only 43 reported environmental incidents, and none of them were caused
by hydraulic fracturing. The majority of the incidents were the result of
drilling and other operations. Although these spills and leaks are still
unacceptable, the study shows that the process of hydraulic fracturing is not to
blame, and that existing problems can be remedied with better practices and
procedures.
The Air Pollution
Problem
A more recent issue that has been raised on the topic of
hydraulic fracturing is the emissions it generates. When the oil and gas are
retrieved from wells, chemicals from the fracking water and the ground come up with
them in what is called 'flowback'. These emissions include methane, VOCs, and
hazardous pollutants such as benzene, sulfur dioxide, and hexane.
In addition to the obvious problems associated with air
toxins and VOCs, the release of methane is a problem for scientists and
environmentalists concerned with global warming. This is because methane (the
primary component of natural gas) is up to 72 times more potent than CO2
in terms of warming the atmosphere over a 20 year period.
Some scientists say that the benefits of using natural gas over coal are
ultimately being offset by methane releases from fracking, and they fear the
near-term warming changes that could come as a result.
The EPA's Response
Just last week, on April 18, the EPA issued regulations on the control
of air pollution from hydraulic fracturing. These regulations will require
fracking operations to install equipment by January 2015 to reduce VOCs and hazardous
pollutants.
Unlike other pollution regulations, these standards have the
possibility of actually be cost effective. The pollution control equipment will
indirectly allow companies to capture methane, which can be sold for revenue
along with the rest of the harvested natural gas. Estimators say the
regulations could actually generate profit depending on the amount of methane
retrieved.
In addition to these regulations, the pressure is continuing
to build on fracking companies to clean up their emissions. This pressure (in
addition to concerns about water usage and spills) could slow down the momentum
of natural gas production, a very key part of the U.S.'s growing economy
(particularly in the chemical industry). But is it a necessary sacrifice?
References
C&EN
- EPA Issues Fracking Rules
EarthWorks
- Hydraulic Fracturing 101
Journal
of Natural Food & Health - Five Myths About Fracking
MIT
- The Future of Natural Gas (pdf)
Texas
Tribune - EPA Issues New Standards for Hydraulic Fracturing
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