Natural Gas Q & A

Natural gas is more abundant in the United States that ever before because of hydraulic fracturing—also called fracking—a technique that extracts gas that was once too difficult or expensive to reach. Gas is second only to coal in generating electricity.

Natural gas development has serious impacts on the quality of our air and water. As a result of fracking, communities in shale plays across the country have experienced increases in harmful air pollutants such as volatile organic compounds and ground level ozone.

And although natural gas burns cleaner than coal, its use may actually accelerate the pace of climate change through methane vents and leaks. Natural gas is made mostly of methane, and methane is a powerful greenhouse gas – many times more powerful than carbon dioxide. Leaks in pipes and equipment used throughout the natural gas development and distribution process mean that significant amounts of methane are being released into the atmosphere.

Learn more about the health impacts of natural gas operations below.

What is natural gas?

Natural gas is a fossil fuel formed underground over millions of years from the remains of plants, animals and microorganisms. Like all fossil fuels, it is “non renewable”—there is a finite amount of it, and once it is depleted, there is no more available for future needs. As a non-renewable resource, natural gas is consumed much faster than nature creates it.

Natural gas is generally found a mile or more beneath the earth’s surface, but is sometimes found at shallower depths.


natural gas graphic

Natural gas is a combustible mixture of hydrocarbon gases, consisting primarily of methane—but also containing smaller amounts of other substances such as ethane, propane and butane, along with hydrogen sulfide and carbon dioxide. Many of these gases, like methane, are greenhouse gases: they trap heat in the atmosphere and contribute to global warming.

What is methane?

Methane is the primary component of natural gas—typically about 70% to 90% by volume. It is a molecule, CH4, made up of one carbon atom and four hydrogen atoms. The combustion of methane produces heat, water (H20), and carbon dioxide (CO2).

Methane is a powerful greenhouse gas, many times more potent than carbon dioxide, which is currently the largest contributor to human-caused climate change. Greenhouse gases in our atmosphere trap the sun’s heat on our planet. Too much of these gases in the atmosphere trap too much heat, fundamentally changing the climate of our planet.

methane molecule graphic


Methane emissions accounted for about 10% of U.S. greenhouse gas emissions in 2012. Close to 30% of those emissions came from the production, transmission, and distribution of oil and natural gas. In the absence of new regulations, methane emissions from the oil and gas sector are projected to rise more than 25% by 2025.

Other major sources of methane emissions include crude oil production, the cattle industry, and landfills.

Methane is odorless, colorless, and tasteless. Its awful rotten-egg odor comes from mercaptan, which is deliberately added to the gas as it’s processed so that you can smell a gas leak in your home or on your block.

What is shale gas?

Shale gas is natural gas that has been mined from shale formations. Shale is fine-grained, organic-rich, sedimentary rock. Shale can contain oil and natural gas in its layers.

Millions of years ago, the remains of ancient plants were trapped in layers of mud, preventing normal decay. That mud was buried under the earth and exposed to high temperatures and pressures, chemically transforming the sediment to rock, called shale, and the trapped particles into natural gas, called shale gas. As shale was formed, clays in the mud compressed and layered—making it difficult for the trapped oil and gas to rise through the formation.

Today natural gas producers use horizontal drilling and hydraulic fracturing to break up the shale and release the trapped oil and gas. This has increased the amount of shale gas that can be extracted and brought to market.

In 2001, shale gas accounted for only 2% of total U.S. natural gas production. In one decade—because of technological developments in horizontal drilling and hydraulic fracturing–that number grew to 30%.

The U.S. Energy Information Administration projects that shale gas production will increase significantly between 2009 and 2035. By 2035, shale gas is projected to reach nearly half of total domestic natural gas production.

And natural gas consumption as a whole is predicted to increase in the coming decades. The brisk and far-reaching scope of shale gas extraction has led to profound public concern about the negative impacts of irresponsible gas development on human health and our air, water and land.

Shale plays map

Why is a “shale play”?

Most of the shale gas in North America is concentrated in ancient sedimentary basins in distinct geographical areas, or “shale plays.” There are currently over twenty active shale plays in the United States.

Shale plays cross state lines, following geological rather than political boundaries. Top shale plays in the US include the Bakken, Barnett, Eagle Ford, Fayetteville, and Marcellus.

Click here for a map of U.S. shale plays.

What is fracking?

During the hydraulic fracturing process, commonly referred to as “fracking,” millions of gallons of water, combined with sand and chemicals – some of them toxic–are injected down a well bore under intense pressure to create tiny fissures in the shale, allowing the trapped oil or natural gas to flow into the well.

Hydraulic fracturing is not new. It has been used in oil and gas wells for decades. What’s new is the combination of hydraulic fracturing with horizontal drilling. With horizontal drilling technology, the well bores turn sideways – think of a bendable straw – to reach much further into and along the shale formation. It’s this recent combination of technologies that has made it profitable to produce shale gas in areas that were once prohibitively expensive for gas industry development.

Fracking is increasing. Shale gas extraction through fracking has driven US production of natural gas to record levels. More than 80,000 wells have been drilled or permitted for drilling using fracking since 2005, according to a 2013 report.

Fracked wells have short lives. They are often capped within a few years of creation. However, compared to traditional natural gas wells, they tend to be more productive.

As a result, shale gas production has increased from less than 5 billion cubic feet per day in 2000 to more than 40 billion per day today. Well pads and associated infrastructure (pipelines, condensers, separators, compressors, and more) now encroaches on urban areas, school grounds, suburbs, and other places where people live, learn, work, and play.

Why is venting?

Venting is the direct release of natural gas into the atmosphere, without burning it first. This can happen at several points along the natural gas lifecycle, including well completion, well maintenance, pipeline maintenance, and tank maintenance.

Because methane is the primary component of natural gas, venting delivers large quantities of methane directly into the atmosphere. Methane is a powerful greenhouse gas – 25 times more powerful than carbon dioxide over a 100-year period.

Methane is not the only component of natural gas, however. Wherever methane is vented, other harmful pollution such as volatile organic compounds are also entering the air. This pollution may impact the health of nearby communities and contribute to smog formation.

Together with flaring, venting was responsible for the loss of more than 260 billion cubic feet of natural gas in the US in 2013, according to the Energy Information Administration.

What is flaring?

Flaring is the practice of burning off excess gas at the well pad. It produces harmful pollution. Flaring eliminates excess gas and protects pipes from becoming over-pressured. Natural gas from oil wells is frequently flared when there is no pipeline infrastructure in place to transport the gas to market.

Flaring burns 98% of the methane in natural gas, a potent greenhouse gas that is the primary component of natural gas. Without flaring, that methane would otherwise be vented to the atmosphere, contributing to climate change. But flaring produces both carbon dioxide – a greenhouse gas – and nitrogen oxides (NOx), which contribute to smog formation. Flaring can also lead to emissions of soot, carbon monoxide and other pollutants that harm human health.

Flaring also creates light pollution. The flares of North Dakota are now visible from space.

On top of these health and environmental impacts, flaring wastes natural gas – a finite, domestic energy resource that could otherwise be used to heat our homes and power our country. The U.S. Government Accountability Office (GAO), with supporting data from EPA, estimates that around 40% of the natural gas vented and flared on onshore federal leases could be captured at a profit to the operator with currently available technologies.

More than 260,000 million cubic feet of natural gas was flared and vented in the US in 2013.

Widespread, wasteful, and polluting flaring of natural gas in shale oil fields is a failure of regulation. There are proven and typically profitable technologies that allow oil and gas companies to prevent flaring and curb methane and toxic air pollution. Robust BLM and EPA standards are needed to end wasteful flaring.

Together with venting, flaring was responsible for the loss of more than 260 billion cubic feet of natural gas in the US in 2013, according to the Energy Information Administration.

What hazardous air pollutants come from natural gas operations?

Leaks, venting, and flaring at natural gas well sites and processing plants release other pollutants besides methane that can threaten air quality and public health, including the following hazardous air pollutants (HAPs):

  • Exposure to benzene can cause skin and respiratory irritation, and long-term exposure can lead to cancer and blood, developmental and reproductive disorders;
  • Long-term exposure to toluene can cause skin and respiratory irritation, headaches, dizziness, birth defects and damage the nervous system;
  • Ethylbenzene can cause irritation of the throat and eyes, and dizziness and long-term exposure can cause blood disorders;
  • High levels of xylene exposure have numerous short-term impacts, including nausea, gastric irritation and neurological effects, and long-term exposure can negatively impact the nervous system; and
  • Exposure to n-hexane can cause dizziness, nausea and headaches, while long-term exposure can lead to numbness, muscular atrophy, blurred vision and fatigue.


Workers inspect a natural gas valve at a fracking site in
Pennsylvania’s Marcellus Shale region. 
According to EPA, areas with natural gas development can have increased levels of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs). The air quality impacts of these emissions vary based on local conditions, but they can be significant, even in rural areas. For example, wintertime ozone levels in excess of the nation’s health-based air quality standards have been recorded in parts of Wyoming and Utah, where natural gas and oil production are the only significant industrial activities.

Community air monitoring has detected high concentrations of some potentially dangerous compounds and chemical mixtures near natural gas operations in some states. Some research indicates that air pollution from natural gas operations can drift long distances, impacting air quality in downwind states.

Other sources of air pollution related to fracking include engines and other combustion sources used throughout the industry. In 2009, a Southern Methodist University study estimated that the combined amounts of VOCs and nitrogen oxides (NOx) emissions from oil and natural gas production in the Barnett Shale of North Texas were comparable to amounts of those emissions from the roughly four million cars and trucks in the Dallas Fort-Worth metro area. The Barnett Shale is a geological formation underlying 5,000 square miles of Texas, including at least 17 counties, and the city of Forth Worth.

What are injection wells?

Injection wells are holes, from hundreds to thousands of feet deep, used to dispose of industrial waste, such as polluted water from fracking.

The fracking process requires the injection of copious amounts of water into well bores, to help create fractures in the shale. Fracking one well uses more than 4 million gallons of water. That water comes back up out of the well bore as “produced water,” or wastewater – millions of gallons that may be laced with chemical additives as well as naturally occurring hazards such as salt, heavy metals, and radioactive substances.

Natural gas operators use injection wells to dispose of the water so that it doesn’t contaminate local groundwater. Although not technically part of the fracking process, injection wells are a critical component of the natural gas life cycle.

Injecting millions of gallons of highly pressurized water deep underground into injection wells across the country has increased seismic activity in some regions. According to the US Geological Survey, Oklahoma has been the hardest hit by recent increases in earthquakes; other states seeing fracking-related increases in earthquakes include Texas, Arkansas, Ohio, and Colorado.

Injection wells also pose the risk of leakage and water contamination. The wells have no special containers at the bottom of the hole; the polluted water can seep into the surrounding geological formation. Impermeable layers theoretically prevent the industrial waste from leaking or seeping; but earthquakes are among the many unpredictable factors that could alter the integrity of injection wells. Such wells do fail; there is little information about how often, or what might be the consequences.

Can fracking cause earthquakes?

While hydraulic fracturing does have micro-seismic impacts, the earthquakes that have gained attention are not the result of the hydraulic fracturing process. Rather, they are linked to the deep well injection of wastewater that is produced after a well is hydraulically fractured.

A fracking site in Bradford County, Pennsylvania. 

In deep well injection, produced water laced with salts, heavy metals, carcinogens, or radioactive substances is trucked from the well pad and injected into disposal wells – holes anywhere from hundreds to thousands of feet deep. Along with the fracking boom, injection wells are also on the rise, and these wells have been linked to increased seismic activity.

According to the US Geological Survey, Oklahoma has been the hardest hit by recent increases in earthquakes; other states seeing fracking-related increases in earthquakes include Texas, Arkansas, Ohio, and Colorado.

The increasing incidence of earthquakes points to the need for better rules for injection wells, including improved analysis of the geology surrounding injection wells and better monitoring of pressure in the wells.

Does natural gas production make smog worse?

Yes. Methane is a chemical precursor to ground level ozone, or smog. Smog is a powerful lung irritant that triggers asthma attacks, interferes with lung development, and increases heart attacks, among other health impacts. Smog is not emitted directly but instead is formed in the atmosphere through the reaction of volatile organic compounds (VOCs), such as methane, and nitrogen oxides (NOx) in the presence of sunlight.

Oil and gas development produces significant amounts of smog-forming pollution and is directly linked to ozone problems in states like Wyoming, where previously pristine air quality has deteriorated to levels that violate the nation’s health-based air quality standards for ozone. Wyoming families are now experiencing unhealthy levels of ozone concentrations on some days comparable to some of the nation’s most polluted urban areas. Natural gas operations have also been linked to smog pollution in Texas, Colorado, and Utah.

Without rigorous pollution control measures, the problem of ozone pollution will worsen as the pace of oil and gas development surges across the country. The U.S. Energy Information Administration projects that shale gas production will triple between 2009 and 2035, and that by 2035 shale gas will account for nearly 46% of domestic energy production. In some communities close to oil and gas development, there is inadequate ozone monitoring. People need to know whether the air they are breathing is safe.

Children, the elderly, and people with existing respiratory conditions are the most at risk from ozone pollution. Children are more vulnerable to the damaging effects of ozone because their lungs are still developing—and because children tend to spend more time outdoors than adults.

Ozone pollution also contributes to climate change. According to the Intergovernmental Panel on Climate Change (IPCC), ozone is the third-largest contributor to climate change after carbon dioxide and methane.

How else do natural gas operations affect nearby communities?

Air pollution is not the only area of concern for communities near natural gas operations. Here are some other issues that nearby communities are grappling with:

  • Water management—The fracking process requires the use of water to inject into well bores and help create fractures in the shale. Fracking one well uses more than 4 million gallons of water. Careful use of water is especially important in areas prone to drought and in sensitive ecosystems;
  • Wastewater management—The fracking process produces wastewater that can be laced with chemical additives and naturally occurring hazards. This water is often called “produced water.” It is generally not safe to release this water back into the groundwater system. Wastewater must be handled, stored, transported and either disposed of or recycled in ways that protect people and the environment. Spills and leaks in waste containment facilities are a major problem in the industry;
  • Well integrity—Poor construction and operation of wells – especially in casing, cementing and pressure management –can lead to the contamination of drinking water; and
  • Local community impacts—Communities can be overwhelmed by the impacts of gas development activities, such as infrastructure development, truck traffic, lights and noise, and burdens on local government resources.
Drill rig set up for winter natural gas drilling in Wyoming

How much methane leaks into the air from natural gas operations?

According to EPA data, oil and gas operations leak roughly 8 million metric tons of unburned natural gas annually. That’s enough natural gas to heat over 5 million homes.

Just how much methane is released into the atmosphere during these processes is uncertain because the measured data is limited and the technology used to extract natural gas has evolved rapidly in recent years. The Environmental Protection Agency (EPA) has estimated the methane leak rate at a little more than two percent.

But a recent study by the National Oceanic and Atmospheric Administration (NOAA) suggested it might be twice that in northern Colorado. Other studies suggest it could be higher still. An academic review of hundreds of studies indicates that official estimates of methane leaks from the oil and gas sector are considerably lower than actual leak rates.

Random leaks and malfunctions probably account for a large portion of methane emissions from oil and gas operations, highlighting the need for regular, ongoing monitoring. Leak detection, done with infrared cameras, should be a routine part of oil and gas operations; data indicate that more than 90% of the gas leaking from connectors, valves, and regulators at oil and gas facilities could be prevented through leak repair that would pay for itself within one year.

How much methane leaks from pipelines in towns and cities?

In addition to leaks from oil and gas wells and infrastructure, methane also leaks from urban natural gas pipelines. Researchers know very little about this kind of urban leakage. The leak rate may depend on the age of the pipelines and storage infrastructure.

A February, 2015, study of methane leaking from natural gas pipelines, storage facilities, and other sources in the Boston area showed a leak rate as much as three times greater than previously estimated. According to the Harvard University researchers, the leaks could heat 200,000 homes a year and waste $90 million annually.

Pipeline construction and sand tankers in Wyalusing, PA (5)

Is natural gas extraction dangerous?

Yes. Current production practices – including the use of hydraulic fracturing, or fracking – have resulted in unacceptable impacts on air, water, landscapes, people and communities. Irresponsible natural gas development presents serious risks to people’s health and the environment in several ways, including:

  • Human exposure to toxic chemicals and the waste products of gas extraction;
  • Contamination of groundwater and surface water from spills, problems with well construction and operation, and failures at waste storage facilities;
  • Global warming impacts through the release of methane—a powerful greenhouse gas;
  • Harmful air pollution—both local and regional—from equipment and activities involved in drilling, extraction and pipeline transportation; and
  • Negative impacts on the quality of life in communities.

How can the natural gas industry reduce emissions?

There are many strategies that natural gas producers can use to reduce emissions of methane and other hazardous air pollutants. “Green completions” can reduce emissions from the gas well when drilling is over but production hasn’t started. That’s when the well bore must be cleaned out to get it ready for production. In the past, a significant amount of gas was vented or flared during that process.

Green completions improve the process by capturing that gas instead, generally with portable equipment brought right to the wellhead. A 2012 federal requirement made it mandatory for drillers to use green completions by 2015. This requirement may help reduce the practice of venting methane directly into the atmosphere.

Mandatory green completions are an important first step in reducing air pollution—but they cover only new sources, and don’t address existing wells, pipelines, and other oil and gas infrastructure.

New source standards for green completions don’t address venting or flaring from wells and other infrastructure that are already built or in operation. In order to address that much larger source of emissions, standards that address “existing sources” of industrial pollution from the oil and gas industry are needed.

Green completions are one example of how flaring and venting of methane and other harmful emissions from the natural gas industry can be reduced, often with economic benefits for the gas developers—who are otherwise wasting product they could be selling.

North Dakota’s Bakken shale — a primary area for fracking 

How can states limit pollution from natural gas?

Many states have made efforts to regulate natural gas production on a local level, and some have been successful.

Major oil and gas producing states like Colorado, Ohio, and Wyoming are instituting ongoing leak detection and repair programs to limit methane emissions, with the goal of reducing costly waste in the oil and gas industry, and improving public health in surrounding communities.

In February, 2014, Colorado approved regulations on the natural gas industry to reduce methane emissions. The Colorado regulations – which were backed by four of the largest natural gas developers in the state – include requirements to use leak-proof valves and conduct regular inspections for methane leaks. Learn more about Colorado’s program here.

Learn more about Ohio’s program here.

Learn more about Wyoming’s program here.

Meanwhile, dozens of localities have enacted bans and moratoria on fracking due to concerns about health impacts in nearby communities.

Modern natural gas well detail

How can the federal government limit pollution from natural gas?

The fracking industry enjoys exemptions from key provisions of the Clean Air Act and other federal environmental laws. But new and upcoming regulations may significantly limit fracking pollution.

A 2012 federal requirement made it mandatory for companies to use green completions by 2015. This requirement may help reduce the practice of venting methane directly into the atmosphere.

These standards for the oil and natural gas sector are also called New Source Performance Standards, or NSPS. They are an important first step in reducing air pollution—but they cover only new sources, and not all new gas wells are included. Moreover, they don’t address existing oil and gas wells, pipelines, or other oil and gas infrastructure – where a lot of methane can also be emitted.

In January, 2015, the Obama Administration announced that it would issue regulations of the oil and gas industry that would cut methane emissions 45% from 2012 levels by 2025. These regulations will focus on reducing leaks from oil and gas operations.

These regulations will initially address only new sources of pollution from the oil and gas industry, focusing on wells and other infrastructure that have not yet been built. Such “new source” regulations are, again, only a first step. Meaningful limits on pollution from this industry will only come when existing sources – the thousands upon thousands of wells and pipeline miles and compressor stations already in operation – come under federal anti-pollution regulations.

It is expected that the Obama Administration will issue new source pollution standards for methane emissions in the summer of 2015, and that existing source pollution standards will follow.

Does using natural gas help or hurt our climate?

We don’t yet know.

Carbon dioxide is the largest source of industrial greenhouse gas emissions. Natural gas releases far less carbon dioxide when burned than coal. Because coal accounts for a large portion of our carbon dioxide, replacing coal with natural gas for electricity generation could reduce carbon dioxide emissions.

But carbon dioxide is not the only significant greenhouse gas. Methane (CH4), the primary component of natural gas, is a greenhouse gas many times more potent than carbon dioxide (CO2), and it is an important contributor to human-made climate change.

Pound for pound, methane can trap heat about 25 times more effectively than carbon dioxide over a 100-year timeline. Over a shorter timeline, the impact of methane is even greater. This is because methane breaks down relatively quickly in the atmosphere.

This means that even small amounts of methane can significantly contribute to climate change in near-term decades. Methane can leak at many points along the natural gas life cycle. Even very small leaks at the point of production, along the pipeline system, or at the local distribution system can erase any potential climate change benefits of switching from coal to natural gas.

Leaving aside important questions about local air quality, groundwater contamination, and other community concerns relating to natural gas operations, the climate benefits of natural gas depend on a well-monitored, well-maintained, and well-regulated system from extraction to transmission to end-use.

Right now, that’s not what we have. The EPA has estimated that in 2013, the oil and gas industry released more than 7.3 million metric tons of methane into the atmosphere from their operations—a three percent increase over 2012—making it largest industrial source of methane pollution.

Is natural gas better than coal?

Natural gas has the potential to be good for our air because it means we are burning less coal. But as fracking increases, more and more concerns come to light – such as methane leaks, community impacts, and injection well failures.

Burning coal for energy releases huge amounts of climate-warming carbon dioxide and other dangerous air pollutants, including mercury. Natural gas burns cleaner than either coal or oil, with lower emissions at the smokestack of greenhouse gases, smog-forming pollutants, mercury, sulfur dioxide, soot and other contaminants. But compared to alternative energy sources such as sunlight and wind, natural gas is still a polluting fossil fuel.

Output from renewable energy technologies harnessing the wind and the sun can vary over the course of a day or a season. Since we want to increase the amount of renewables used in the US, it’s important to have readily available energy sources that can quickly fill in the gaps. Unlike coal-fired plants, natural gas power plants can adapt their output quickly, making them better suited than coal plants as supplements to intermittent wind and solar energy generation.

But the pollution caused by natural gas exploration, drilling and transport may outweigh these cleaner-at-the-power-plant benefits. That’s because of leaking toxic air pollutants and methane, a potent greenhouse gas and the major component of natural gas, all along the chain of extraction and production. The scope of such leaks is unknown; but some communities near oil and gas activity are suffering from debilitating air pollution. Research on rates of methane leakage is ongoing.

Coal fired power plants—the biggest carbon polluters–are closing at a rapid clip. Low natural gas prices play a large role in these coal plant closures. Utilities are using more natural gas as natural gas prices continue to outcompete coal.

What gives EPA authority to regulate methane emissions?

Under the Clean Air Act, EPA is required to limit pollutants that are dangerous to human life and health. A 2011 Supreme Court decision affirmed that greenhouse gases are harmful to health, laying the legal groundwork for EPA to issue regulations that limit these harmful emissions.

When the Clean Air Act was written, in the 1970s, the dangers of climate change were understood by only a handful of scientists and policymakers. However, the architects of the Act foresaw that there could be as-yet-unknown harmful pollutants that would require regulation, and so the law was written to allow for pollutants not explicitly identified in the original language of the Act.

Although methane itself, like carbon dioxide, is not a toxic pollutant, the effects of its unchecked release in our atmosphere is changing the climate in a way that is harmful to human life and health – through climate change.





TOPICS: Natural Gas

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