Environmental impact of fracking
The environmental impact of fracking is related to land use and water consumption, air emissions, including methane emissions, brine and fracturing fluid leakage, water contamination, noise pollution, and health. Water and air pollution are the biggest risks to human health from fracking. Research has determined that fracking negatively affects human health and drives climate change.
Fracking fluids include proppants and other substances, which include chemicals known to be toxic, as well as unknown chemicals that may be toxic. In the United States, such additives may be treated as trade secrets by companies who use them. Lack of knowledge about specific chemicals has complicated efforts to develop risk management policies and to study health effects. In other jurisdictions, such as the United Kingdom, these chemicals must be made public and their applications are required to be nonhazardous.
Water usage by fracking can be a problem in areas that experience water shortage. Surface water may be contaminated through spillage and improperly built and maintained waste pits, in jurisdictions where these are permitted. Further, ground water can be contaminated if fracturing fluids and formation fluids are able to escape during fracking. However, the possibility of groundwater contamination from the fracturing fluid upward migration is negligible, even in a long-term period. Produced water, the water that returns to the surface after fracking, is managed by underground injection, municipal and commercial wastewater treatment, and reuse in future wells. There is potential for methane to leak into ground water and the air, though escape of methane is a bigger problem in older wells than in those built under more recent legislation.
Fracking causes induced seismicity called microseismic events or microearthquakes. The magnitude of these events is too small to be detected at the surface, being of magnitude M-3 to M-1 usually. However, fluid disposal wells have been responsible for earthquakes up to 5.6M in Oklahoma and other states.
Governments worldwide are developing regulatory frameworks to assess and manage environmental and associated health risks, working under pressure from industry on the one hand, and from anti-fracking groups on the other. In some countries like France a precautionary approach has been favored and fracking has been banned. The United Kingdom's regulatory framework is based on the conclusion that the risks associated with fracking are manageable if carried out under effective regulation and if operational best practices are implemented. It has been suggested by the authors of meta-studies that in order to avoid further negative impacts, greater adherence to regulation and safety procedures are necessary.
Air emissions
A report for the European Union on the potential risks was produced in 2012. Potential risks are "methane emissions from the wells, diesel fumes and other hazardous pollutants, ozone precursors or odours from hydraulic fracturing equipment, such as compressors, pumps, and valves". Also gases and hydraulic fracturing fluids dissolved in flowback water pose air emissions risks. One study measured various air pollutants weekly for a year surrounding the development of a newly fractured gas well and detected nonmethane hydrocarbons, methylene chloride, and polycyclic aromatic hydrocarbons. These pollutants have been shown to affect fetal outcomes.The relationship between hydraulic fracturing and air quality can influence acute and chronic respiratory illnesses, including exacerbation of asthma and COPD. For example, communities overlying the Marcellus shale have higher frequencies of asthma. Children, active young adults who spend time outdoors, and the elderly are particularly vulnerable. OSHA has also raised concerns about the long-term respiratory effects of occupational exposure to airborne silica at hydraulic fracturing sites. Silicosis can be associated with systemic autoimmune processes.
"In the UK, all oil and gas operators must minimise the release of gases as a condition of their licence from the Department of Energy and Climate Change. Natural gas may only be vented for safety reasons."
Also transportation of necessary water volume for hydraulic fracturing, if done by trucks, can cause emissions. Piped water supplies can reduce the number of truck movements necessary.
A report from the Pennsylvania Department of Environmental Protection indicated that there is little potential for radiation exposure from oil and gas operations.
Air pollution is of particular concern to workers at hydraulic fracturing well sites as the chemical emissions from storage tanks and open flowback pits combine with the geographically compounded air concentrations from surrounding wells. Thirty seven percent of the chemicals used in hydraulic fracturing operations are volatile and can become airborne.
Researchers Chen and Carter from the Department of Civil and Environmental Engineering, University of Tennessee, Knoxville used atmospheric dispersion models to estimate the potential exposure concentration of emissions for calculated radial distances of 5 m to 180m from emission sources. The team examined emissions from 60,644 hydraulic fracturing wells and found "results showed the percentage of wells and their potential acute non-cancer, chronic non-cancer, acute cancer, and chronic cancer risks for exposure to workers were 12.41%, 0.11%, 7.53%, and 5.80%, respectively. Acute and chronic cancer risks were dominated by emissions from the chemical storage tanks within a 20 m radius.
Climate change
Hydraulic fracturing is a driver of climate change. However, 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 methane 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.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. Other researchers have criticized Howarth's analysis, including Cathles et al., whose estimates were substantially lower." A 2012 industry funded report co-authored by researchers at the United States 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.
Studies which have estimated lifecycle methane leakage from natural gas development and production have found a wide range of leakage rates. According to the Environmental Protection Agency's Greenhouse Gas Inventory, the methane leakage rate is about 1.4%. A 16-part assessment of methane leakage from natural gas production initiated by the Environmental Defense Fund found that fugitive emissions in key stages of the natural gas production process are significantly higher than estimates in the EPA's national emission inventory, with a leakage rate of 2.3 percent of overall natural gas output.
Water consumption
Massive hydraulic fracturing typical of shale wells uses between of water per well, with large projects using up to. Additional water is used when wells are refractured. An average well requires of water over its lifetime. 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. Whilst the published amounts may seem large, they are small in comparison with the overall water usage in most areas. A study in Texas, which is a water shortage area, indicates "Water use for shale gas is <1% of statewide water withdrawals; however, local impacts vary with water availability and competing demands."A report by the Royal Society and the Royal Academy of Engineering shows the usage expected for hydraulic fracturing a well is approximately the amount needed to run a 1,000 MW coal-fired power plant for 12 hours. A 2011 report from the Tyndall Centre estimates that to support a gas production industry, between would be needed annually, which amounts to 0.01% of the total water abstraction nationally.
Concern has been raised over the increasing quantities of water for hydraulic fracturing in areas that experience water stress. 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. The large volumes of water required for most common hydraulic fracturing methods have raised concerns for arid regions, such as the Karoo in South Africa, and in drought-prone Texas, in North America. It may also require water overland piping from distant sources.
A 2014 life cycle analysis of natural gas electricity by the National Renewable Energy Laboratory concluded that electricity generated by natural gas from massive hydraulically fractured wells consumed between 249 gallons per megawatt-hour and 272 gal/MWhr. The water consumption for the gas from massive hydraulic fractured wells was from 52 to 75 gal/MWhr greater than the 197 gal/MWhr consumed for electricity from conventional onshore natural gas.
Some producers have developed hydraulic fracturing techniques that could reduce the need for water. Using carbon dioxide, liquid propane or other gases instead of water have been proposed to reduce water consumption. 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. Recycled flowback water can be reused in hydraulic fracturing. 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.