What is Fracking?
Fracking is a fairly recent technology used by the natural gas and petroleum industry to maximize extraction. The process has helped make the United States the world’s leading fossil fuel producer. However, as fracking’s environmental fingerprint grows, so do environmental concerns. Here I explain the fracking process and the risks.
Fracking Produces Two-Thirds of America’s Natural Gas and Half the Oil
Fracking, short for hydraulic fracturing, is a relatively new extraction method for natural gas and petroleum, which injects water, chemicals and sand at very high pressure into shale rock formations, to release the gas and oil trapped within. Aided by new technologies such as horizontal drilling and micro seismic imaging, fracking is unlocking stores of fossil fuels that previously were thought to be unreachable for both technical and commercial reasons.
The International Energy Agency (IEA) now estimates recoverable reserves of shale gas to be an eye-popping 208 trillion cubic meters. In America, fracking has dramatically boosted domestic oil production and driven down gas prices. It may also allow coal to be phased out earlier than expected. According to the U.S. Energy Information Administration, it produces two-thirds of the nation’s natural gas and about half the oil. (1) Industry analysts calculate it provides gas security to the USA and Canada for the rest of the century. (2) Dr Fatih Birol, executive director of the IEA, said the U.S. is on course to become the world’s undisputed oil and gas growth story — and it’s all because of fracking. (3) (4)
Nevertheless, for anyone concerned about the environmental effects of fossil fuels, the idea of diverting resources away from renewable energies towards a dirty fossil fuel, will seem like lunacy. To understand why governments and fossil fuel companies are dragging their feet over climate action, see: Root Cause of Climate Change.
In This Article
- The Ohio Methane Disaster
- Fracking: History And Development
- Hydraulic Fracturing
- What Are The Environmental Problems Of Fracking?
- Carbon Dioxide Emissions
- Methane Emissions From Fracking
- Fracking May Be Causing The Current Spike In Methane Emissions
- Improper Use Of Chemicals
- Depletion Of Local Water Supplies
- Contamination Of Groundwater
- Wastewater Pollution
- Fracking Harms Local Wildlife
- Human Health Issues
- New Reports Into Fracking And Natural Gas
Oil-services giant Schlumberger Ltd once described fracking as employing “brute force and ignorance” — an observation reinforced by the fact that only recently has technology been able to monitor what happens to the fracking fluid and its chemical additives, during the process of hydraulic fracturing. 5 In any event, fracking continues to attract serious opposition from environmentalists on several accounts. It has been accused of causing earthquakes in Oklahoma and poisoning water supplies in Pennsylvania, while New York, Maryland, and Vermont have banned it. In Europe, France, Germany, Ireland and the UK, have all imposed moratoriums, as have five of Australia’s eight states. (6)
U.S. Energy Information Administration itself has numerous concerns about fracking, involving climate change as well as environmental pollution. These include: loss of water supply, destruction of aquatic habitats, contamination of groundwater, earthquakes from the injection of wastewater into deep wells for disposal, and emission of greenhouse gases, principally methane. (7)
The oil and gas industry suggest pollution problems are the results of mismanagement, rather than an inherently risky technique. They may be right, but who cares? After all, contamination is still contamination, a methane cloud is still a methane cloud, and a water shortage is still a water shortage, whether fracking is dangerous or not.
Besides, any natural gas executive must know that methane is an inherently dangerous substance, able to cause 84 times more climate damage over 20 years, than carbon dioxide.
The Ohio Methane Disaster
On Feb 15, 2018, according to a study published in the Proceedings of the National Academy of Sciences, an explosive blowout at a fracked gas well in Belmont County, Ohio, owned by ExxonMobil, led to more methane being leaked into the air over 20 days than all but three European nations emit during an entire year.
Ohio Fracking Accident
February 2018 — Ohio fracking site accident. Resulted in more methane leaking into the atmosphere in a few days, than the entire oil and gas industries of many nations in a year. (8)
According to scientists using satellite data, the methane escaped twice as fast as it did during the Aliso Canyon methane disaster in California, in 2015, when methane equivalent to the annual emissions from 572,000 cars was released. In Ohio, a total of 60 kilotons of methane were emitted into the atmosphere — roughly five times the amount ExxonMobil estimated. (9) (10)
This is the first time that methane leak from an oil or gas installation has been both detected and measured via satellite (the Tropospheric Monitoring Instrument), during routine global observation.
The study reconfirms what environmentalists have been saying for years, that methane pollution from oil and gas infrastructure is significantly higher than regulators and operators are admitting to the public. For example, the Environmental Defence Fund (EDF) revealed last year that over the previous five years, its studies had discovered that emissions from the U.S. oil and gas sector were 60 percent higher than estimates from the Environmental Protection Authority (EPA).
“Research has shown that large, unpredictable events are responsible for a disproportionate share of methane emissions, ” the EDF states. But generally, these emissions have not been included in EPA inventories.” What’s more, research shows that a small proportion of natural gas wells are responsible for the majority of methane emissions through seepage or venting. Instead of venting, retrofits and methane-capture could dramatically reduce emissions but would add to costs.
What Does Natural Gas Emit — Carbon Dioxide Or Methane?
Both. Natural gas is 90 percent methane. So, any emissions from a gas pipeline or refinery will be methane. But when natural gas is burned for heat, it is converted into carbon dioxide (CO2) and water vapor (H2O). So any emissions from a gas-fired power plant will be carbon dioxide.
Fracking: History And Development
The first modern-day example of fracking occurred in 1947, following a study by Floyd Farris of Stanolind Oil & Gas. The frack took place at the Hugoton gas field in Kansas and was used to extract natural gas from limestone. Around 1,000 gallons of gelled gasoline was injected into the gas-rich limestone rock at a depth of about 2,400 feet. Although this first attempt didn’t lead to any significant amount of extra gas being produced, it heralded the beginning of a new approach to the recovery of natural gas. (11)
In 1949, the Halliburton Oil Well Cementing Company carried out the first two successful commercial frackings; one in Archer County, Texas, and one in Stephens county, Oklahoma. Soon other fracking operators, like Pan American Petroleum, joined in, developing operations in Oklahoma and further afield.
New technologies were introduced. In 1953, for instance, napalm and other petroleum products were replaced by water and gelling agents in the injection process.
During the mid-1960s, drillers in West Virginia and Kentucky used hydraulic fracturing on shale formations for the first time. In addition, the industry began to realize that the technique could be used to improve production from wells with low yields or difficult-to-exploit resources: an unusual example being sea-bed wells in North Sea oil and gas fields.
But it was the 1980s during which fracking truly came of age. Horizontal drilling was pioneered. Texan operators initiated thousands of wells in the Austin chalk and marl formation combining horizontal well bores and large slickwater lubricating treatments. An industry figure who stands out at this time is George P. Mitchell (founder of Mitchell Energy) whose company perfected the science of large-scale shale fracking. Due to his persistence and drive, Mitchell became known as the ‘father of fracking’.
Another improvement was the use of digital technology, namely micro seismic monitoring. Pioneered by Sandia Laboratory, micro seismic monitoring uses surface and near surface detectors to record events deeper underground. As the shale and other fossil fuel-rich rock formations break during fracking, popping noises can be heard. These are then carefully recorded and the locations plotted. This data can then be used to fine-tune the fracking process.
More research and development was carried out during the 1990s into the use of micro seismic monitoring in relation to hydraulic fracturing, notably by the Department of Energy and the Gas Research Institute in Colorado. This culminated, in 2000, in the successful mapping of the Barnett Shale in Texas, using micro seismic imaging, such as the natural-gas-rich area beneath Johnson, Tarrant and western Dallas counties, about a mile and a half underground. Barnett Shale was later calculated to have reserves of 40 trillion cubic feet of natural gas, making it the largest onshore natural gas field in Texas.
According to most industry analysts, the year 2003 marked the start of the shale fracking revolution with independent operators such as Chesapeake, Continental, Devon, EOG Resources, Pioneer and many others buying up exploration plots across the America.
By 2012, 2.5 million fracking operations had taken place at oil and gas wells around the world — with more than 1 million in the U.S. alone. By 2016, according to the Energy Information Administration, hydraulic fracturing accounted for more than half of all oil output in America (up from 2 percent in 2000) and over two thirds of natural gas. In December 2018, US shale oil production reached 8 million barrels per day and continues to increase.
Stage 1. Preparation of Site
All the above-ground well site infrastructure, including well pads and access roads, are constructed, in preparation for drilling. Traffic plans, noise barriers and safety procedures are created and monitored according to state and local laws.
Stage 2. Drilling
To begin with, the drill rig is transported to the well site — involving maybe 30–35 truckloads — and assembled. Then the drilling starts. First, a surface hole is drilled vertically to a depth of 100 feet below the deepest known aquifer (water-carrying rock). Next, a steel casing is cemented around the wellbore to ensure there is no risk of polluting water aquifers. Third, the “long hole” is drilled, again vertically. Once it reaches roughly 1000 feet above the underground rock formation in which the oil or natural gas is trapped, the hole is gradually turned ninety degrees, so that it now travels horizontally. The drilling may continue horizontally for 2 miles or more.
Stage 3. Cementing and Testing
Once the hole has reached its destination inside the oil/gas-rich shale or other rock formation, the drill pipe is replaced with a steel pipe is inserted. This steel casing is then cemented in place. Tests are then conducted to make sure that the casing is impermeable before proceeding to tap the natural gas or oil.
Stage 4. Holes Created in Casing
Before drillers extract any oil and natural gas, a perforating gun is lowered into the well and fired into the rock layer at the foot of the well, creating holes in the casing through which the oil of gas can escape to the surface.
Stage 5. Hydraulic Fracturing
While monitoring well pressure and other metrics, fracking fluid — 98–99 percent water and sand, the rest chemicals — is pumped at high pressure through the perforating holes to create paper-thin cracks in the shale rock, freeing the oil and natural gas trapped inside. Each fracking well uses about 3–7 million gallons of water during its lifetime. The chemicals used may include: additives to lubricate the well; acids to dissolve debris; and disinfectants to kill bacteria. Fracking firms have used about 2,500 different fracking chemicals so far, of which roughly 650 have been identified as toxic.
The last 2 stages are repeated along the horizontal length of the pipe, until all the wellbore has been fracked. This may take several days to complete.
Stage 6. Oil/Gas Production Begins
Once all the fracking is finished, production begins. Oil and natural gas flow up the well with the fracking fluid. The fluid — now contaminated with radioactive material, heavy metals, salts, and other compounds — is stored on-site in ponds or in underground “injection wells”, or off-site at water treatment facilities. The natural gas is stored in tanks on site before being piped to the refinery.
Stage 7. End of Operations. Land Restoration
When all the oil and natural gas has been extracted, some states require that the well is permanently plugged and the land is restored to the condition it was in before drilling operations started.
This is the model as described by oil and gas experts. Even this, however, cannot hide the areas of environmental concern, which we will now examine. To keep things as simple as possible, we’ll focus our attention on natural gas wells.
What Are The Environmental Problems Of Fracking?
Hydraulic fracturing is associated with numerous environmental hazards. These include: emissions of CO2, emissions of methane; improper use of chemicals; depletion of local water supplies; contamination of groundwater; wastewater pollution; earthquakes; land use and loss of habitats; and damage to human health. To critics of fossil fuels, this trail of destruction is nothing new.
Carbon Dioxide Emissions
Supporters of natural gas often claim that fracking is helping the U.S. and others to provide a cleaner, healthier type of fossil fuel energy: cleaner than coal, at any rate. This is partly true: gas combustion produces only negligible quantities of sulfur dioxide, mercury, and particulate matter (PM10 or PM2.5). It is thus less polluting than the combustion of coal or oil, and this benefits health. (12) In addition, emissions of carbon dioxide from natural gas power plants are around 55 percent of those produced by coal-fired plants.
But it’s purely relative. There’s nothing clean or healthy about emissions of carbon dioxide. The climate science is clear: CO2 fossil fuel emissions are causing global warming, and natural gas accounts for more than one fifth of them, and rising. Which is why critics of fracking believe it makes more sense to invest in the development of clean, renewable energy rather than waste money on dirty fuels.
Methane Emissions From Fracking
But emissions of carbon dioxide, bad though they are, are only half the problem. The other half concerns methane emissions. These are a huge headache for the natural gas industry and they can occur in two ways. First, methane can escape into the atmosphere from pipelines, refineries or other installations. This seepage can continue around the clock, 365 days of the year.
After several warning studies, 13 a 2018 study in Science 14 revealed that the latest leakage rate is 2.3 percent, a figure which is about 60 percent higher than estimates made by the EPA, the environment watchdog. (15)
Why is the gas leakage rate important? There are two reasons. First, if seepage exceeds 3.2 percent, natural gas power plants lose their emissions advantage over coal. For a natural gas-fired power plant to have lower life-cycle emissions than a coal plant, the gas industry’s annual methane leakage rate must be kept below 3.2 percent. (16)
Second, leakage of unburned natural gas is always in the form of methane — one of the worst greenhouse gases — which causes far more climate damage over 20 years than carbon dioxide. A discharge of 1,000 tons of methane, for instance, has the heat-trapping power of 84,000 tons of CO2. Even over 100 years, methane is still 25 times more potent than CO2.
In a nutshell, natural gas is not quite the clean fuel it’s made out to be. And the methane emitted in 2020 will be boosting the greenhouse effect and global warming for the next century.
Fracking May Be Causing The Current Spike In Methane Emissions
As well as leaking from gas industry infrastructure, methane can also escape out of the fracking wellhead. For example, a 2015 study estimated that the North Texas Barnett Shale gas field leaked 544,000 tons of methane a year. (17)
Waste Water from Hydraulic Fracturing
Waste water from a fracking site. The oil and gas industry has flooded Pennsylvania with over 380 million barrels of liquid waste from 1991 to 2017. Chemicals found in fracked oil and gas, released into the air and water are known to cause cancer. (18)
According to another study published in the Proceedings of the National Academy of Sciences, abandoned wells in western Pennsylvania were emitting significant amounts of methane (56 milligrams per hour on average). None of it, however, is recorded by regulators. Since there are up to 500,000 abandoned oil and gas wells in Pennsylvania alone, their combined emissions could add up to a serious problem. (19) “There definitely are leaky abandoned oil and gas wells out there, and we should really consider including them in greenhouse gas inventories,” says lead researcher Mary Kang.
Another study published in 2015 found that natural gas installations lose roughly 100 billion cubic feet of natural gas each year — about eight times what EPA estimates. (20)
Study Blames Fracking For Methane Spike
An important 2015 study, led by John Worden of NASA’s Jet Propulsion Laboratory, found that methane levels — after remaining unchanged for years — increased sharply after 2006, jumping by 25 million tons a year. Using satellite data and other sources the research team found that fossil fuel production was responsible for 12–19 million tons of it with the rest likely due to biological sources. (21)
Now, new research into the chemical make-up of the additional methane, published in Biogeosciences, points the finger at gas fracking as the likely culprit for the surge in methane levels, since it occurred at the same time as the use of fracking for shale gas took off in the U.S. The quantity of methane added to the atmosphere in the past decade is also consistent with studies showing that fracking operations leak, vent, or flare between 2 and 6 percent of the natural gas produced. (22)
Improper Use Of Chemicals
Gas companies typically add chemicals to the fluid used in fracking. Those chemicals can help to decrease friction, dissolve debris, prevent corrosion, kill bacteria and so on. They typically make up between 0.5 percent to 2 percent of the fluid used. In total, something like 2,500 different chemicals have been used in fracking to date. According to one congressional report 23 the list of additives used by fracking companies includes 29 chemicals that are either known or possible carcinogens, or are regulated by the federal authorities because of other risks to human health. Hopefully, today’s frackers are more selective in their choice of chemicals, otherwise these toxic materials may leech out of their containment ponds, contaminating groundwater.
Depletion Of Local Water Supplies
Unlike most other energy-related withdrawals of water, which are usually returned to their home rivers and lakes, most of the water used for fracking is not recoverable. Depending on the rock to be fracked and the depth and location of the well, a single well can require 3 million to 12 million gallons of water when it is first fractured. Similar volumes are required each time a well undergoes a “work over,” later in its life in order to maintain well pressure and gas production. A typical shale gas well will have about two work overs during its productive life span. (24) This enormous removal of water plays havoc with local ecological systems and habitats, especially those involving aquatic life.
In Arkansas, scientists found water levels in more than half the streams to be dangerously low due to water uptake for fracking operations. (25)
Contamination Of Groundwater
Fracked gas is usually found deep underground — typically thousands of feet deeper than the water table. As a result, it is considered unlikely that any fracking fluid could migrate from the shale layer up into the groundwater, since there are dozens of layers of intervening rock. Even so, environmentalists point to the fact that badly constructed or maintained boreholes may leak fluid into the water-bearing aquifers they pass through, contaminating the drinking water. (15)
In fact, there are a number of documented cases of groundwater contamination in Ohio and Pennsylvania, caused by fracking fluids as well as by methane and volatile organic compounds. Nearly all were due to bad well construction or maintenance. (26, 27, 28)
The fracking industry produces billions of gallons of toxic wastewater (fracking fluid) each year. Sometimes, this wastewater is pumped back underground into so-called “injection wells.” Or, the water is stored in on-site tanks and holding ponds, or it is dealt with off-site at water treatment facilities. That’s not necessarily the end of the matter, however. In 2013, three water treatment plants in Pennsylvania were fined for dumping waste in the Allegheny River.
In several other cases, drinking water was contaminated from surface leaks and spills of fracking fluid, sometimes caused by failed wastewater pit liners (29) (30)
Fracking Harms Local Wildlife
The construction and land disturbance necessary for gas drilling and fracking can significantly harm local biodiversity, wildlife habitats and migration patterns. This is due to many factors including: traffic noise, exhaust pollution, surface erosion, and spillage. When gas operators clear a site, and then set up a well pad, pipelines, access roads and storage areas, the construction process can force dirt, minerals, and other harmful pollutants into nearby streams. (31)
A study into the effects of hydraulic fracturing in Michigan found abnormal levels of erosion, an increased risk of aquatic contamination from chemical spills or mechanical intrusion, habitat fragmentation, and lower surface waters due to water depletion. (32)
Human Health Issues
In a study into hydraulic fracturing in Pennsylvania, in 2018, researchers found that children born within a mile or so of a fracked well were likely to be smaller and less healthy. (33)
New Reports Into Fracking And Natural Gas
A study by economists at Carnegie Mellon University, published in Nature Sustainability, claims that the shale gas boom in Appalachia produced short term profits for the gas industry while exacting a high price from the public in the region. The study claims that, for every 3 jobs created by the shale gas industry, someone’s life in Appalachia was cut short by 12 months. In addition, the costs of air pollution from shale gas extraction exceeded employment benefits in the Ohio Valley by over $2 billion, while the climate effects add another $34 billion in estimated losses. (34)
The findings are consistent with a report published in May by ECONorthwest. After analyzing the costs of fracking in Pennsylvania, ECONorthwest economists conclude that the annual costs of fracking in the state are approximately $1.5 billion -the equivalent of 0.3 percent of the state’s GDP. If fracking were to continue at current rates, they calculate that the costs would increase to $54 billion over the next 20 years. The true cost, the study says, would include cancer, cardiac conditions, occupational hazards, groundwater contamination, seismic activity, and more.
In a paper published in the New England Journal of Medicine, four of America’s top public health doctors warned about the dangers of natural gas, claiming that it is associated with health and environmental hazards and reduced social welfare at every stage of its life cycle. They connect it to water contamination, air pollution, release of radiation, ecological damage, earth tremors, and on and on. (35)
Two other reports are also critical of gas fracking. (36)
In their May 2019 report, the Oregon and Washington Physicians for Social Responsibility found: “the fracking process degrades the environment of surrounding communities through toxic contamination of air and water with hundreds of chemicals with known associations to cancer, heart and lung disease, developmental disorders, and poor pregnancy outcomes.”
The Physicians for Social Responsibility, in their latest report on fracked gas, analyzed more than 1,700 peer-reviewed studies and independent reports. Over 80 percent found health damage related to fracking. The report also says that there is no evidence that hydraulic fracturing can operate without threatening public health directly or without endangering climate stability upon which public health depends.
“Is your ‘natural’ gas actually fracked?” Sightline Institute. Oct 2017. (1) [↩]
“What is fracking and why is it controversial?” BBC News. 15 October 2018. (2) [↩]
“Fracking — the reality, the risks and what the future holds.” Adam Vaughan. Guardian Feb 26, 2018. (3) [↩]
“The Environmental Costs and Benefits of Fracking.” Robert B. Jackson, Avner Vengosh, J. William Carey, Richard J. Davies, Thomas H. Darrah, Francis O’Sullivan, Gabrielle Petron. Annual Review of Environment and Resources. Vol. 39: pp 327–362. October 2014. (4) [↩]
“After Decades of Fracking, We Finally Know How the Fluid Spreads Underground.” Allison McCartney, David Wethe. Bloomberg. October 25, 2019. (5) [↩]
For example, see: Environmental Aspects on Unconventional Fossil Fuels (6) [↩]
“Natural gas explained.” Natural gas and the environment. U.S. Energy Information Administration. EIA. (7) [↩]
Satellite Discovery of Anomalously Large Methane Point Sources From Oil/Gas Production by D. J. Varon et al [↩]
“Satellite observations reveal extreme methane leakage from a natural gas well blowout.” Sudhanshu Pandey, Ritesh Gautam, Sander Houweling, Hugo Denier van der Gon, Pankaj Sadavarte, Tobias Borsdorff, Otto Hasekamp, Jochen Landgraf, Paul Tol, Tim van Kempen, Ruud Hoogeveen, Richard van Hees, Steven P. Hamburg, Joannes D. Maasakkers, Ilse Aben. Proceedings of the National Academy of Sciences. December 26, 2019 116 (52) 26376–26381; first published December 16, 2019. (8) [↩]
“A blowout turned an Ohio natural gas well into a methane super-emitter.” Steven Mufson. Washington Post. Dec. 16, 2019. (9) [↩]
“A brief history of fracking.” Matt Donnelly. Fircroft.com July 31, 2019. (10) [↩]
A review of the public health impacts of unconventional natural gas development. Saunders PJ, McCoy D, Goldstein R, Saunders AT, Munroe A. Environ Geochem Health 2018; 40:1–57. (11) [↩]
“Greater focus needed on methane leakage from natural gas infrastructure.” Alvarez, R.A., S.W. Pacala, J.J. Winebrake, W.L. Chameides, S.P. Hamburg. 2012. Proceedings of the National Academy of Sciences 109(17):6435–40. April 24, 2012. (12) [↩]
“Assessment of methane emissions from the U.S. oil and gas supply chain”. Alvarez, Ramon A. et al; (2018–07–13). Science. 361 (6398): 186–188. (13) [↩]
“Oil and Gas Facilities Leak More Methane Than Previously Thought.” John Fialka. E&E News. Scientific American. June 22, 2018. (14) [↩]
“3 Big Myths about Natural Gas and our Climate.” The Climate Reality Project. July 6, 2018. (15) [↩]
“Reconciling divergent estimates of oil and gas methane emissions.” Daniel Zavala-Araiza, David R. Lyon, Ramon A. Alvarez, Kenneth J. Davis, Robert Harriss, Scott C. Herndon, Anna Karion, Eric Adam Kort, Brian K. Lamb, Xin Lan, Anthony J. Marchese, Stephen W. Pacala, Allen L. Robinson, Paul B. Shepson, Colm Sweeney, Robert Talbot, Amy Townsend-Small, Tara I. Yacovitch, Daniel J. Zimmerle, and Steven P. Hamburg. PNAS December 22, 2015 112 (51) 15597–15602; December 7, 2015. (16) [↩]
Compendium of scientific, medical and media findings demonstrating risks and harms of fracking [↩]
“Direct measurements of methane emissions from abandoned oil and gas wells in Pennsylvania.” Mary Kang, Cynthia M. Kanno, Matthew C. Reid, Xin Zhang, Denise L. Mauzerall, Michael A. Celia, Yuheng Chen, Tullis C. Onstott. PNAS. 8, Dec 2014. (17) [↩]
“Methane Emissions from United States Natural Gas Gathering and Processing.” Anthony J. Marchese, Timothy L. Vaughn, Daniel J. Zimmerle, David M. Martinez, Laurie L. Williams, Allen L. Robinson, Austin L. Mitchell, R. Subramanian, Daniel S. Tkacik, Joseph R. Roscioli, Scott C. Herndon. Environ. Sci. Technol. 2015, 49, 17, 10718–10727. August 18, 2015. (18) [↩]
“Reduced biomass burning emissions reconcile conflicting estimates of the post-2006 atmospheric methane budget.” John R. Worden, A. Anthony Bloom, Sudhanshu Pandey, Zhe Jiang, Helen M. Worden, Thomas W. Walker, Sander Houweling & Thomas Rockmann Nature Communications volume 8, Article number: 2227 (2017) (19) [↩]
Howarth, R. W.: Ideas and perspectives: is shale gas a major driver of recent increase in global atmospheric methane? August 2019. Biogeosciences, 16, 3033–3046 (20) [↩]
“Millions of Gallons of Hazardous Chemicals Injected into Wells.” New York Times. April 17, 2011 (21) [↩]
National Energy Technology Laboratory (NETL). 2009. Modern shale gas development in the United States: A Primer. United States Department of Energy. (22) [↩]
“Water Stress from High-Volume Hydraulic Fracturing Potentially Threatens Aquatic Biodiversity and Ecosystem Services in Arkansas, United States.” Sally Entrekin, Anne Trainor, James Saiers, Lauren Patterson, Kelly Maloney, Joseph Fargione, Joseph Kiesecker, Sharon Baruch-Mordo, Katherine Konschnik, Hannah Wiseman, Jean-Philippe Nicot, Joseph N. Ryan. Environ. Sci. Technol. 2018, 52, 4, 2349–2358. January 31, 2018. (23) [↩]
Pennsylvania Department of Environmental Protection (PADEP). 2009. (24) [↩]
Ohio Department of Natural Resources, Division of Mineral Resources Management. 2008. Report on the investigation of the natural gas invasion of aquifers in Bainbridge Township of Geauga County, Ohio. September 1, 2008. (25) [↩]
“Environmental Impacts of Natural Gas.” Union of Concerned Scientists. Jun 19, 2014. (26) [↩]
“Impact of shale gas development on regional water quality.” Vidic, R.D., S.L. Brantley, J.M. Vandenbossche, D. Yoxtheimer, and J.D. Abad. 2013. Science 340(6134). (27) [↩]
“Evaluating system for ground-water contamination hazards due to gas-well drilling on the glaciated Appalachian Plateau.” Harrison, S.S. 1983. Groundwater 21(6):689–700. (28) [↩]
“Field-based monitoring of sediment runoff from natural gas well sites in Denton County, Texas, USA.” H.F.L. Williams, D.L. Havens, K.E. Banks, D.J. Wachal. 2008. Environmental Geology 55:1463–1471. (29) [↩]
Burton, G.A., K.J. Nadelhoffer, and K. Presley. 2013. “Hydraulic fracturing in the state of Michigan: Environment.” University of Michigan. September 3. (30) [↩]
“Hydraulic fracturing and infant health: New evidence from Pennsylvania.” Janet Currie, Michael Greenstone, Katherine Mecke. Science Advances. Vol. 3, no. 12 Dec 13, 2017. (31) [↩]
“Cumulative environmental and employment impacts of the shale gas boom.” Erin N. Mayfield, Jared L. Cohon, Nicholas Z. Muller, Ines M. L. Azevedo, Allen L. Robinson. Nature Sustainability. Vol 2. Dec 2019. 1122–1131. (32) [↩]
“The False Promise of Natural Gas.” Philip J. Landrigan, M.D., Howard Frumkin, M.D., Dr.P.H., Brita E. Lundberg, M.D. January 9, 2020. New England Journal of Medicine. 2020; 382:104–107 (33) [↩]
“2019 Was the Year that Fracking Fell Apart.” Eric de Place. Sightline Institute. December 27, 2019. (34) [↩]