Environmental impact of hydraulic fracturing

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Illustration of hydraulic fracturing and related activities

Environmental impact of hydraulic fracturing includes the potential contamination of ground water, risks to air quality, noise pollution, the potential migration of gases and hydraulic fracturing chemicals to the surface, the potential mishandling of waste, and the health effects of these.[1][2] Many cases of suspected groundwater contamination have been documented.[3][4] Most of the studies on the environmental impact of hydraulic fracturing have been conducted in the United States.[citation needed] This is due to the fact that the US has not adopted a precautionary approach and therefore has decided to use fracking, conducting ex-post risk assessment, which allows to see the impacts of hydraulic fracturing on the environment. Countries that have adopted a precautionary approach like France [5] cannot evaluate such impacts since they do not undergo the potential hazards of fracking. Nevertheless, studies also exist for the North of England, Canada and Australia too, whose approach is close to the American one.

Air emissions[edit]

The main hydraulic-fracturing-related air emissions are methane emissions from the wells during fracturing and emissions from hydraulic fracturing equipment, such as compressor stations. Whether natural gas produced by hydraulic fracturing causes higher well-to-burner emissions than gas produced from conventional wells is a matter of contention. Some studies have found that hydraulic fracturing has higher emissions due to gas released during completing wells as some gas returns to the surface, together with the fracturing fluids. Depending on their treatment, the well-to-burner emissions are 3.5%–12% higher than for conventional gas.[6]

A debate has arisen particularly around a study by professor Robert W. Howarth finding shale gas significantly worse for global warming than oil or coal.[7] Other researchers have criticized Howarth's analysis,[8][9] including Cathles et al., whose estimates were substantially lower."[10] A 2012 industry funded report co-authored by researchers at the U.S. Department of Energy's National Renewable Energy Laboratory found emissions from shale gas, when burned for electricity, were "very similar" to those from so-called "conventional well" natural gas, and less than half the emissions of coal.[11]

This has led to saying shale gas could be a “transitionel fuel” to help reaching greenhouse gas emissions diminution in order to fight climate change and global warming.[12] Nevertheless, studies have demonstrated that the argument did not empirically hold in the UK. Indeed, a study conducted in 2011 by Broderick et al. said that “If the UK Government is to respect its obligations under both the Copenhagen Accord and Low Carbon Transition Plan, shale gas offers no meaningful potential as even a transitional fuel.”[13] Moreover, the 2012 Tyndall Center report stated that the US have known an increase in coal consumption that has gone on rising. They thus conclude, saying “without a meaningful cap on global emissions, the exploitation of shale gas reserves is likely to increase total emissions.” [14]

Several studies which have estimated lifecycle methane leakage from shale gas development and production have found a wide range of leakage rates, from less than 1% of total production to nearly 8%.[15][16] According to the Environmental Protection Agency's Greenhouse Gas Inventory a methane leakage rate is about 1.4%.[17] The American Gas Association, an industry trade group, calculated a 1.2% leakage rate.[18] The most comprehensive study of methane leakage from shale gas to date, initiated by the Environmental Defense Fund and released in the Proceedings of the National Academy of Sciences on September 16, 2013, finds that fugitive emissions in key stages of the natural gas production process are significantly lower than estimates in the EPA's national emissions inventory. The study reports direct measurements from 190 onshore natural gas sites, all hydraulically fractured, across the country and estimates a leakage rate of 0.42% for gas production.[15]

Also transportation of necessary water volume for hydraulic fracturing, if done by trucks, can cause high volumes of air emissions, especially particulate matter emissions.[19]

Water consumption[edit]

Hydraulic fracturing uses between 1.2 and 3.5 million US gallons (4,500 and 13,200 m3) of water per well, with large projects using up to 5 million US gallons (19,000 m3). Additional water is used when wells are refractured.[20][21] An average well requires 3 to 8 million US gallons (11,000 to 30,000 m3) of water over its lifetime.[21][22][23][24] According to the Oxford Institute for Energy Studies, greater volumes of fracturing fluids are required in Europe, where the shale depths average 1.5 times greater than in the U.S.[25]

Concern has been raised over the increasing quantities of water for hydraulic fracturing. Use of water for hydraulic fracturing can divert water from stream flow, water supplies for municipalities and industries such as power generation, as well as recreation and aquatic life.[26] The large volumes of water required for most common hydraulic fracturing methods have raised concerns for arid regions, such as Karoo in South Africa,[27] and in Pennsylvania,[28][29] and in drought-prone Texas, and Colorado in North America.[30] It may also require water overland piping from distant sources.[23]

Some producers have developed hydraulic fracturing techniques that could reduce the need for water.[31] Using carbon dioxide, liquid propane or other gases instead of water have been proposed to reduce water consumption.[32] After it is used, the propane returns to its gaseous state and can be collected and reused. In addition to water savings, gas fracturing reportedly produces less damage to rock formations that can impede production.[31] Recycled flowback water can be reused in hydraulic fracturing.[6] It lowers the total amount of water used and reduces the need to dispose of wastewater after use. The technique is relatively expensive, however, since the water must be treated before each reuse and it can shorten the life of some types of equipment.[33] Also, fracking converts millions of gallons of water into toxic wastewater each year, taking this water out of the water cycle and the possibility of further use, except in fracking itself after recycling.[34]

New data shows that water saved by using natural gas combined cycle plants instead of coal steam turbine plants saves 25–50 times more water than the amount of water needed to extract the gas using hydraulic fracturing.[35]

Water contamination[edit]

Although local groundwater contamination resulting from fracking has been documented, the American Environmental Protection Agency has launched a comprehensive study whose results will be released in 2014 to know if there is a general impact of hydraulic fracturing on groundwater contamination.[36]

Injected fluid[edit]

Hydraulic fracturing fluids may cause contamination both as it is injected under high pressure into the ground and as it returns to the surface.[37][38] To mitigate the effect of hydraulic fracturing on groundwater, the well and ideally the formation itself should remain hydraulically isolated from other geological formations, especially freshwater aquifers.[6]

The type of chemicals used in hydraulic fracturing and their properties vary. While most of them are common and generally harmless, some chemicals used in the United States are carcinogenic.[1] Out of 2,500 hydraulic fracturing additives, more than 650 contained known or possible human carcinogens regulated under the Safe Drinking Water Act.[1] Another 2011 study identified 632 chemicals used in United States natural gas operations, of which only 353 are well-described in the scientific literature.[39]

The European Union regulatory regime requires full disclosure of all additives.[40] In the US, the Ground Water Protection Council launched FracFocus.org, an online voluntary disclosure database for hydraulic fracturing fluids funded by oil and gas trade groups and the U.S. Department of Energy.[41][42]


As the fracturing fluid flows back through the well, it consists of spent fluids and may contain dissolved constituents such as minerals and brine waters.[43][44] In some cases, depending the geology of formation, it may concentrate uranium, radium, radon and thorium.[45] Estimates of the amount of injected fluid returning to the surface range from 15-20% to 30–70%.[44][46] Additional fluid may return to the surface through abandoned wells or other pathways.[47]

Approaches to managing these fluids, commonly known as produced water, include underground injection, municipal and commercial wastewater treatment and discharge, self‐contained systems at well sites or fields, and recycling to fracture future wells.[11][44][48][49] The vacuum multi-effect membrane distillation system as a more effective treatment system has been proposed for treatment of flowback.[50] However, the quantity of waste water needing treatment and the improper configuration of sewage plants have become an issue in some regions of the United States. Part of the wastewater from hydraulic fracturing operations is processed there by public sewage treatment plants, which are not equipped to remove radioactive material and are not required to test for it.[51][52]

A 2011 report by the MIT Energy Initiative addressed groundwater contamination, noting "there has been concern that these fractures can also penetrate shallow freshwater zones and contaminate them with fracturing fluid, but there is no evidence that this is occurring".[53]

Surface spills[edit]

Surface spills related to the hydraulic fracturing occur mainly because of equipment failure or engineering misjudgments.[54][55]

Volatile chemicals held in waste water evaporation ponds can to evaporate into the atmosphere, or overflow. The runoff can also end up in groundwater systems. Groundwater may become contaminated by trucks carrying hydraulic fracturing chemicals and wastewater if they are involved in accidents on the way to hydraulic fracturing sites or disposal destinations.[56]


Groundwater methane contamination has adverse effect on water quality and in extreme cases may lead to potential explosion.[57] A scientific study conducted by researchers of Duke University found high correlations of gas well drilling activities, including hydraulic fracturing, and methane pollution of the drinking water.[57] According to the 2011 study of the MIT Energy Initiative, "there is evidence of natural gas (methane) migration into freshwater zones in some areas, most likely as a result of substandard well completion practices i.e. poor quality cementing job or bad casing, by a few operators."[53] A 2013 Duke study suggested that both faulty construction (defective cement seals in the upper part of wells and faulty steel linings within deeper layers) and peculiarity of local geology may be allowing methane and injected fluid to seep into waters.[38] Abandoned gas and oil wells also provide conduits to the surface.[47]

However, methane contamination is not always caused by hydraulic fracturing. Drilling for ordinary drinking water wells can also cause methane release. Most recent studies make use of tests that can distinguish between the deep thermogenic methane released during gas/oil drilling, and the shallower biogenic methane that can be released during water-well drilling. While both forms of methane result from decomposition, thermogenic methane results from geothermal assistance deeper underground.[58][59] A study by Cabot Oil and Gas examined the Duke study using a larger sample size, found that methane concentrations were related to topography, with the highest readings found in low-lying areas, rather than related to distance from gas production areas. Using a more precise isotopic analysis, they showed that the methane found in the water wells came from both the formations where hydraulic fracturing occurred, and from the shallower formations.[58] The Colorado Oil & Gas Conservation Commission has found some wells containing thermogenic methane due to oil and gas development upon investigating complaints from residents.[59] A review published in February 2012 found no direct evidence that hydraulic fracturing actual injection phase resulted in contamination of ground water, and suggests that reported problems occur due to leaks in its fluid or waste storage apparatus; the review says that methane in water wells in some areas probably comes from natural resources.[60][61]


Hydraulic fracturing causes induced seismicity called microseismic events or microearthquakes. These microseismic events are often used to map the horizontal and vertical extent of the fracturing.[62] The magnitude of these events is usually too small to be detected at the surface, although the biggest micro-earthquakes may have the magnitude of about -1.6 (Mw). However, as of late 2012, there have been three instances of hydraulic fracturing, through induced seismicity, triggering quakes large enough to be felt by people: one each in the United States, Canada, and England.[63][64] In England, two earthquakes that occurred in April and May 2011 of a magnitude of respectively 1.5 and 2.3 on the Richter scale were felt by local populations. The UK Department of Energy and Climate Change said the “observed seismicity in April and May 2011 was induced by the hydraulic fracture treatments at Preese Hall”, in the North of England.[12] The injection of waste water from gas operations, including from hydraulic fracturing, into saltwater disposal wells may cause bigger low-magnitude tremors, being registered up to 3.3 (Mw).[65]

A 2012 US Geological Survey study reported that a "remarkable" increase in the rate of M ≥ 3 earthquakes in the US midcontinent "is currently in progress", having started in 2001 and culminating in a 6-fold increase over 20th century levels in 2011. The overall increase was tied to earthquake increases in a few specific areas: the Raton Basin of southern Colorado (site of coalbed methane activity), and gas-producing areas in central and southern Oklahoma, and central Arkansas.[66] While analysis suggested that the increase is "almost certainly man-made", the USGS noted: "USGS's studies suggest that the actual hydraulic fracturing process is only very rarely the direct cause of felt earthquakes." The increased earthquakes were said to be most likely caused by increased injection of gas-well wastewater into disposal wells.[67] The injection of waste water from oil and gas operations, including from hydraulic fracturing, into saltwater disposal wells may cause bigger low-magnitude tremors, being registered up to 3.3 (Mw).[65]

Induced seismicity from hydraulic fracturing[edit]

The United States Geological Survey (USGS) has reported earthquakes induced by hydraulic fracturing and by disposal of hydraulic fracturing flowback into waste disposal wells in several locations. Bill Ellsworth, a geoscientist with the U.S. Geological Survey, has said, however: “We don't see any connection between hydraulic fracturing and earthquakes of any concern to society.”[68] The National Research Council (part of the National Academy of Sciences) has also observed that hydraulic fracturing, when used in shale gas recovery, does not pose a serious risk of causing earthquakes that can be felt.[69] In 2013, Researchers from Columbia University and the University of Oklahoma demonstrated that in the midwestern United States, some areas with increased human-induced seismicity are susceptible to additional earthquakes triggered by the seismic waves from remote earthquakes. They recommended increased seismic monitoring near fluid injection sites to determine which areas are vulnerable to remote triggering and when injection activity should be ceased.[63][70]

A British Columbia Oil and Gas Commission investigation concluded that a series of 38 earthquakes (magnitudes ranging from 2.2 to 3.8 on the Richter scale) occurring in the Horn River Basin area between 2009 and 2011 were caused by fluid injection during hydraulic fracturing in proximity to pre-existing faults. The tremors were small enough that only one of them was reported felt by people; there were no reports of injury or property damage.[71]

A report in the United Kingdom concluded that hydraulic fracturing was the likely cause of two small tremors (magnitudes 2.3 and 1.4 on the Richter scale) that occurred during hydraulic fracturing of shale in April and May 2011.[72][73][74] These tremors were felt by local populations. Because of these two events, seismicity is impact mostly related to hydraulic fracturing in the UK's public opinion.[12]

Induced seismicity from water disposal wells[edit]

According to the USGS only a small fraction of roughly 30,000 waste fluid disposal wells for oil and gas operations in the United States have induced earthquakes that are large enough to be of concern to the public.[67] Although the magnitudes of these quakes has been small, the USGS says that there is no guarantee that larger quakes will not occur.[75] In addition, the frequency of the quakes has been increasing. In 2009, there were 50 earthquakes greater than magnitude 3.0 in the area spanning Alabama and Montana, and there were 87 quakes in 2010. In 2011 there were 134 earthquakes in the same area, a sixfold increase over 20th century levels.[76] There are also concerns that quakes may damage underground gas, oil, and water lines and wells that were not designed to withstand earthquakes.[75][77]

Several earthquakes in 2011, including a 4.0 magnitude quake on New Year's Eve that hit Youngstown, Ohio, are likely linked to a disposal of hydraulic fracturing wastewater,[63] according to seismologists at Columbia University.[78] A similar series of small earthquakes occurred in 2012 in Texas. Earthquakes are not common occurrences in either area.[79]

Health risks[edit]

Concern has been expressed over the possible long and short term health effects of air and water contamination and radiation exposure by gas production.[45][80][81] Health consequences of concern include infertility, birth defects and cancer.[82][unreliable medical source?][83][84][unreliable medical source?] There are reports of health problems around compressors stations[85][unreliable medical source?] or drilling sites,[86] although a causal relationship was not established for the limited number of wells studied[86] and another Texas government analysis found no evidence of effects.[87]

Trace amounts of chemicals used in the drilling process may affect the health of those working on or living near the wells. In 2012, researchers from the Colorado School of Public Health showed that air pollution caused by hydraulic fracturing may contribute to "acute and chronic health problems" for those living near drilling sites.[88] A 2012 study concluded that risk prevention efforts should be directed towards reducing air emission exposures for persons living and working near wells during well completions.[89] A study conducted in Garfield County, Colorado and published in Endocrinology suggested that natural gas drilling operations may result in elevated endocrine-disrupting chemical activity in surface and ground water.[83]

PEHSU has linked higher vulnerability in children to health risks associated with chemical exposure to hydraulic fracturing fluids.[90] This increased risk is due to a higher ratio of consumption pound for pound versus adults' rate of consumption, along with the inability to metabolize certain toxants that the body is able to metabolize as an adult.[90] The same kind of vulnerability is also exhibited in development of the fetus during pregnancy, and health risks may involve neural tube defects, decreased birth perameters, and childhood leukemia.[90]

Safety issues[edit]

An additional concern is that oil obtained through hydraulic fracturing contains chemicals used in hydraulic fracturing, which may increase the rate at which rail tank cars and pipelines corrode, potentially releasing their load and its gases.[91][92]

Scientific debate[edit]

There are two main approaches to regulation that derive from a scientific debate over the value of risk assessment. Social sciences have raised two main critiques of risk assessment. Firstly, it takes scientific issues out of the public debate since there is no debate on the use of a technology but on its impacts. Secondly, it does not prevent environmental harm from happening since risks are taken then assessed instead of evaluated then taken as it would be the case with a precautionary approach to scientific debates. The relevance and reliability of risk assessments in fracking communities has also been debated amongst environmental groups, health scientists, and industry leaders. The risks, to some, are overplayed and the current research is insufficient in showing the link between fracking and adverse health effects, while to others the risks are obvious and risk assessment is underfunded.[12]

Different regulatory approaches have thus emerged. In France and Vermont for instance, a precautionary approach has been favored and fracking has been banned based on two principles: the precautionary principle and the prevention principle.[5][93] Nevertheless, some States such as the U.S. have adopted a risk assessment approach, which had led to many regulatory debates over the issue of hydraulic fracturing and its risks.

In the UK, the regulatory framework is largely being shaped by a report commissioned by the UK Government in 2012, whose purpose was to identify the problems around fracking and to advise the country's regulatory agencies. Jointly published by the Royal Society and the Royal Academy of Engineering, under the chairmanship of Professor Robert Mair, the report features ten recommendations covering issues such as groundwater contamination, well integrity, seismic risk, gas leakages, water management, environmental risks, best practice for risk management, and also includes advice for regulators and research councils.[94][95] The report was notable for stating that the risks associated with fracking are manageable if carried out under effective regulation and if operational best practices are implemented.

Anti-fracking movement[edit]

An anti-fracking movement has emerged both internationally with involvement of international environmental organizations and nation states such as France and locally in affected areas such as Balcombe in Sussex where the Balcombe drilling protest was in progress during summer 2013.[96]

See also[edit]


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