Frequently Asked Questions About Natural Gas

Understanding the Shale Gas Revolution


The shale revolution has played the biggest role in shutting down coal in the last decade, but experts continue to disagree over methane leakage, groundwater contamination, and the possibility that cheap natural gas crowds out space for renewables and nuclear. In this comprehensive FAQ, Breakthrough presents the latest research on natural gas.

September 26, 2014 | Breakthrough Staff,

What is natural gas?

Natural gas is methane (CH4), a combustible gas than can be used as fuel for automobiles, for industrial process heat, for residential uses like cooking, and for electricity generation in power plants.

Natural gas is found in a variety of geologic formations, including coalbed seams, sandstone, limestone, shales, and, frozen methane hydrates under the ocean floor. The extraction of natural gas from the ground also produces natural gas “associates” or “gas liquids” like propane, ethane, and butane, that are typically separated from methane and used for other commercial purposes. Because natural gas takes so many different forms and exists in so many different formations, vast quantities of it are found in most parts of the world.

How is natural gas extracted?

Originally, when crude oil was extracted, natural gas was created as a byproduct, or “gas associate.”  Often, it was initially vented or flared off as a waste product, or reinjected into the petroleum well. But over time uses for natural gas, and the infrastructure to capture and transport it, were developed, allowing natural gas to become an increasingly important fuel source for residential and commercial cooking and heating, power plants, and industrial processes.

By the mid-twentieth century, a strong domestic natural gas industry had developed in the United States, producing gas from large consolidated underground reserves independent from crude oil production. More recently, gas producers have begun producing gas from more dispersed sources in shale and other porous rock formations through the process of hydraulic fracturing. In the future, nations may begin extracting gas from methane hydrates under the oceans, which Japanese researchers recently demonstrated.1

How is it used?

Once separated from gas associates and contaminants, methane is piped to natural gas storage facilities, industrial factories, and power plants. Natural gas power plants are typically classified as either “combustion” or “combined cycle.” Combustion power plants inject pressurized natural gas into a chamber and ignite it, generating steam that spins a power generator and releases waste heat and carbon dioxide. More efficient combined cycle power plants burn methane through a gas turbine and direct the waste heat through a conventional steam turbine. Combined cycle power plants are considerably more efficient compared to combustion plants and most other forms of thermal generation.

Natural gas is also piped directly to homes for heating and cooking, as a feedstock for ammonia fertilizer and hydrogen production (among other industrial processes), and as compressed natural gas (CNG) for automobiles.

What are the environmental impacts and benefits of using gas?

Natural gas, like all fossil fuels, is a chemical byproduct of the decay of ancient organic matter. Burning natural gas generates useful energy and releases carbon dioxide – a greenhouse gas – into the atmosphere.2-3 But natural gas is often a substitute for dirtier fuels that have greater environmental impact. Natural gas used for power generation is substantially cleaner than coal along every environmental and public health metric, including greenhouse gas emissions, land use,4 water pollution,5 and air pollution.6

Coal is responsible for eight times as many deaths-per-terawatt-hour as natural gas7 and creates about twice as many carbon emissions. Coal-fired power plants in the United States also emit 17 to 40 times more sulfur dioxide emissions per megawatt-hour than natural gas. Natural gas electricity uses less water than coal electricity because coal-fired power plants demand so much water as a heat exchanger.8 And where coal exploration requires altering landscapes far beyond the area where the fuel is found, aboveground natural gas equipment takes up just 1 percent of the total surface land area from where the gas will be extracted.9 In the United States, carbon emissions declined more than any other country in the last five years, and the most significant source of emissions reductions was cheap natural gas displacing coal in existing power systems.10

The environmental benefits of natural gas in the transport sector are less pronounced. Natural gas produces fewer volatile organic compounds (VOCs) and smog compared to oil, but without as significant a climate benefit when it replaces oil in the transportation sector as when it replaces coal in the power sector.11 In the developing world, liquid natural gas (LNG) is considerably preferable to traditional forms of heating and cooking that rely on wood and dung, which cause deforestation and terrible public health impacts.

What is fracking?

Hydraulic fracturing is an energy production process that involves pumping water, sand, and chemicals into drilled wells to fracture surrounding rock, releasing oil and/or gas deposits stored in the geologic formations.

Where did fracking come from?

Hydraulic fracturing was first used in the 1940s and continued to be used for decades to produce natural gas in limestone and sandstone. More recently, the use of hydraulic fracturing in shale rock formations has become commercially feasible, resulting in a revolution in oil and gas production in the United States. The revolution of technologies that allowed for the cheap extraction of natural gas from shale came from a 30-year public-private effort. Responding to 1970s OPIC oil crisis, and natural gas shortages in the United States, the US Department of Energy funded extensive demonstration projects to prove there was abundant gas in shales and to support the development of fracking technologies. Private sector oil and gas man, George Mitchell worked with the DOE and the Gas Research Institute to tinker with and combine the fracking, directional drilling, and underground mapping technologies in the 1990s.12

Is fracking worse for the environment than conventional gas?

There is little evidence that fracked gas wells produce significantly more greenhouse or terrestrial pollution than conventional gas wells. Several lifecycle pollution analyses find that shale gas wells produce similar volumes of greenhouse gases compared to conventional wells.13, 14 Shale wells do produce significantly less wastewater per unit energy than conventional wells.15

Done correctly, shale gas fracking is a relatively safe industrial practice. The risks of environmental contamination and local pollution are mostly related to errors in cement pouring and application, drilling near aquifers, and use of air valves and pneumatic pumps. All of these are simple technical problems with identified solutions. Major environmental infractions, which are rare, have been made mostly by small producers. Environmental regulation from the EPA and state-level agencies is appropriate to make sure the industry maintains strong safety and environmental practices and engages productively with local communities.

Like most energy technologies, fracking does have significant impacts on the surrounding landscape, intensifying industrial activity in areas unaccustomed to such practices, increasing heavy trucking activity, contributing to noise pollution, and creating conflicts within communities between those who wish to benefit economically from fracking and those who value particular aesthetic qualities of their communities.16

What about methane leakage?

Methane is not a pollutant that is a byproduct of natural gas extraction, it is the product that is being extracted. Methane leakage, as such, represents a loss of an economically valuable commodity. Reducing leakage and capturing fugitive releases increases profits from drilling operations. Not surprisingly, then, most studies find that methane leak rates are low –– less than 1.5 percent –– and lower than leak rates from conventional natural gas operations. Most leakage results from older wells and from wells operated by smaller, poorly capitalized producers, which represent a small minority.17

Methane leakage from both conventional and unconventional wells have declined substantially over time as practices have been improved and standardized.18 Despite the fact that natural gas production has grown substantially in recent decades, total methane emissions from natural gas production has been declining since the early 1990s. Once the leading source of US methane emissions, natural gas has been surpassed by the agricultural sector.19

While methane is a much more potent greenhouse gas than carbon, its impact is significantly diminished because it is far shorter lived and is emitted in vastly lower quantities than carbon dioxide.20 While some analyses have compared methane and carbon dioxide on a molecule-by-molecule basis, climate scientists and climate models rely more on atmospheric concentrations. For these reasons, methane emissions from gas production appear to have little discernible impact on long-term warming in climate models and scenarios.21 To the degree to which use of natural gas contributes to rising temperatures, the overwhelming contributor to warming will be the carbon emissions associated with gas combustion, not methane emissions associated with extraction and transport. As such, gas, when it displaces coal, has positive climate and emissions benefits.22 However, long-term climate stabilization targets will require that we transition from gas infrastructure to zero-emission sources or capture a substantial portion of carbon dioxide emissions associated with gas combustion.  

Isn’t fracking contaminating ground water?

There is little evidence that fracking fluids have contaminated ground water in the course of fracking operations underground, but there have been a few cases where wastewater associated with fracking operations has spilled or leaked out of storage tanks and ponds and contaminated surface waterways and groundwater. Industrial accidents of this type, as is the case with virtually all industrial activities, from mining to refining, are to some degree inevitable and largely preventable through improved standards, practices, and regulations.

There have been reports of methane contaminating water supplies, but most incidents have not ended up being attributable to fracking. Most incidents of high methane concentrations in groundwater have resulted from naturally occurring sources (often in regions where gas production also is occurring) or from older, conventional natural gas operations, which tend to operate at depths closer to aquifers and groundwater supplies.23 In virtually all cases, both life-cycle water intensity and pollution associated with coal production and combustion far outweigh those related to shale gas production.

If fracking isn’t any worse for the environment than conventional gas and better than coal, then why do so many people oppose it?

The rapid spread of fracking to countrysides in Colorado to Pennsylvania and Ohio has created a lot of often unpleasant disruptions — truck traffic, pollution, new development — and so it is understandable that there has been a strong backlash against natural gas production in regions that historically have not been oil- and gas-producing.24 At the same time, many advocates of climate mitigation favor natural gas. Yale University climate economist William Nordhaus praised replacing coal with gas in his 1994 book Managing the Climate Commons.25 In their widely cited “stabilization wedges” paper in 2004, Stephen Pacala and Robert Socolow achieve one wedge of their climate strategy by replacing coal with natural gas.26 Al Gore suggested that gas could contribute to emissions reductions pathways as recently as 2012.27 And President Barack Obama made a forceful case for expanded natural gas drilling in a major 2013 climate speech.28

What have been the economic impacts of the shale gas revolution?

The shale gas revolution suggests that significant emissions reductions can be achieved in ways that are very good for the economy. The investments American taxpayers made in the shale gas revolution paid for themselves many times over. Every year since 2007, cheaper energy prices from the shale gas revolution have contributed $100 billion to the economy.29 These profits have acted as a critical stimulus to an economy in recession, particularly saving hard-hit rustbelt states like Ohio and Pennsylvania. As such, the shale revolution seriously challenges the notion that the only way to reduce emissions is to make energy more expensive and slow economic growth.

Is natural gas a “bridge” to cleaner fuels in the future?

It certainly could be. While replacing coal with natural gas is an improvement, gas-fired electricity still creates more carbon than lower-carbon sources. If greenhouse gas emissions are to peak and then decline, the energy transition from coal to natural gas must be followed by a transition from natural gas to nuclear or modern renewables like solar and wind.30

Isn’t the gas revolution bad for renewables and nuclear?

Natural gas actually makes renewables like solar and wind viable. Because solar and wind are intermittent, natural gas or some other inexpensive back-up is required. Natural gas plants have ramping (up or down) rates that are 2 to 3 times faster than coal plants. This makes natural gas plants the default choice for supplying “peaking” power to electricity grids.31 There has been no historic correlation between the price and availability of natural gas and deployment of wind or solar power. Deployment rates of wind and solar have typically varied almost entirely based upon the level at which they are subsidized.

Cheap gas has exerted competitive pressure on nuclear, though the challenges facing nuclear — low energy demand and high upfront capital costs — predate and largely overwhelm low costs of natural gas. Natural gas can pair synergistically with nuclear, since baseload nuclear requires more flexible power generation sources to cover peaking demand. It is also the case that utilities do not want to become overly dependent on natural gas, whose price will rise if natural gas is increasingly exported to Europe and Asia.32

Is fracking occurring in other countries?

Other countries – including Poland, Argentina, South Africa, and especially China – are experimenting with fracking for natural gas inside their own borders. However, factors suggest that it will be more difficult for fracking to take off in other countries than it was in the United States. The United States is unique in granting underground mineral rights to landowners and not the state, providing greater economic incentives for gas production in more places. The United States also had a massive preexisting oil and gas sector, including the necessary workforce, investment base, infrastructure, and public RD&D capabilities.

Will the United States continue to benefit from fracking or will we just export the gas to places like China?

Linking the US gas market to other countries – where prices are often four times as high – is certainly expected to push gas prices up to some degree, although this is not expected to be too significant.33 Some experts have noted that increased prices will motivate increased exploration and production, with resulting supplies keeping prices lower. The long-term impact of exporting significant quantities of US gas remains to be seen.

Is gas really displacing coal or are we exporting the coal that we aren’t burning to other countries?

Over 95 percent of the US coal being replaced by natural gas is left in the ground — not exported abroad. Coal production fell by 171 million short tons from its peak in 2008 through 2013, while coal exports rose only 8 million short tons over the same period. (In 2011, exports were up 26 million tons over 2008 levels, but have fallen since then.)

Increased coal exports from the United States have two opposing impacts on foreign coal consumption. The first is an increased quantity of coal supply on the market, which lowers prices and encourages more consumption. The second is a displacement of other coal production, which may actually be dirtier than US exports. This complexity means that the net impact of US coal exports is unclear, although in general the consumption of coal in other countries is a phenomenon of their own making. Few would argue that China, India, South Africa, Germany, and Poland are increasing their coal consumption thanks to increased US exports.

1. Pfeifer, Sylvia. “Methane hydrates could be energy of the future.” The Financial Times. January 17, 2014.

2. Trembath, Alex; Nordhaus, Ted; Shellenberger, Michael; Luke, Max. 2013. Coal Killer: How Natural Gas Fuels the Clean Energy Revolution. Breakthrough Institute.

3. National Research Council of the National Academies, “Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use,” NRC Committee on Health, Environmental, and Other External Costs and Benefits of Energy Production and Consumption, October 2009. ate.79.pdf.

4. Clean Air Task Force, “Cradle to Grave: The Environmental Impacts of Coal,” June 2001.

5. Heather Cooley, Kristina Donnelly, “Hydraulic Fracturing and Water Resources: Separating the Frack from the Fiction,” Pacific Institute, June 2012.

6. Anil Markandya and Paul Wilkinson, “Electricity Generation and Health,” The Lancet 370: 979-990 (2007).

7. Ibid.

8. National Research Council of the National Academies, “Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use,” NRC Committee on Health, Environmental, and Other External Costs and Benefits of Energy Production and Consumption, October 2009. ate.79.pdf.

9. Brian Lutz, “Hydraulic Fracturing versus Mountaintop-Removal Coal Mining: Comparing Environmental Impacts,” Lecture at University of Tulsa, November 28, 2012.

10. Trembath, Alex; Nordhaus, Ted; Shellenberger, Michael; Luke, Max. 2013. Coal Killer: How Natural Gas Fuels the Clean Energy Revolution. Breakthrough Institute.

11. Brandt, A. R., et al. "Methane leaks from North American natural gas systems." Science 343.6172 (2014): 733-735.

12. Michael Shellenberger, Ted Nordhaus, Jesse Jenkins, and Alex Trembath. 2012. “Where the Shale Gas Revolution Came From: Government’s Role in the Development of Hydraulic Fracturing in Shale.” Breakthrough Institute.

13. Heath, Garvin A., et al. "Harmonization of initial estimates of shale gas life cycle greenhouse gas emissions for electric power generation." Proceedings of the National Academy of Sciences (2014): 201309334.

14. Venkatesh, Aranya, et al. "Uncertainty in life cycle greenhouse gas emissions from United States natural gas end-uses and its effects on policy."Environmental science & technology 45.19 (2011): 8182-8189.

15. Brian Lutz, “Hydraulic Fracturing versus Mountaintop-Removal Coal Mining: Comparing Environmental Impacts,” Lecture at University of Tulsa, November 28, 2012.

16. Alex Trembath and Max Luke, “Gas Industry Should Embrace Regulation: Sorting Out Legitimate Concerns About Fracking,” Breakthrough Institute, September 23, 2013.  

17. Alex Trembath, “Methane Leakage from Cows Higher than from Natural Gas Development: New Data from EPA, DOE, and EDF Confirm Declining Methane Leakage,” Breakthrough Institute, March 6, 2014.

18. Alex Trembath and Max Luke, “Methane Leakage Not a Deal Breaker for Natural Gas: A Response to Anthony R. Ingraffea,” Breakthrough Institute, July 29, 2013.

19. Alex Trembath, “Methane Leakage from Cows Higher than from Natural Gas Development: New Data from EPA, DOE, and EDF Confirm Declining Methane Leakage,” Breakthrough Institute, March 6, 2014.

20. Andrew Revkin, “Two Climate Analysts Fault Gas Leaks, but Not as a Big Warming Threat,” The New York Times, August 1, 2013.

21. Levi, Michael. "Climate consequences of natural gas as a bridge fuel." Climatic change 118.3-4 (2013): 609-623.

22. Hausfather, Zeke. “Climate Impacts of Coal and Natural Gas.” Berkeley Earth. August 2014.

23. Osborn, Stephen G., et al. "Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing." proceedings of the National Academy of Sciences 108.20 (2011): 8172-8176.

24. Alex Trembath and Max Luke, “Gas Industry Should Embrace Regulation: Sorting Out Legitimate Concerns About Fracking,” Breakthrough Institute, September 23, 2013.

25. Nordhaus, William D. Managing the global commons: the economics of climate change. Vol. 31. Cambridge, MA: MIT press, 1994.

26. Pacala, Stephen, and Robert Socolow. "Stabilization wedges: solving the climate problem for the next 50 years with current technologies." Science 305.5686 (2004): 968-972.

27. David Roberts, “A chat with Al Gore on carbon taxes, natural gas, and the ‘morally wrong’ Keystone pipeline,” Grist, November 20, 2012. wrong-keystone-pipeline/.

28. Michael Shellenberger and Ted Nordhaus, “President Obama, Coal Killer: How America’s Climate Strategy Became Tied to Natural Gas,” Breakthrough Institute, July 3, 2013.

29. An analysis by graduate students at Yale University calculated that the total US economic benefit of the shale gas revolution for a single year totaled more than $100 billion, in 2010. Using a similar methodology, we estimate that this annual amount will exceed $100 billion through 2020. See Robert Ames et al., “The Arithmetic of Shale Gas,” Yale Graduates in Energy Study Group, June 2012.

30. Trembath, Alex; Nordhaus, Ted; Shellenberger, Michael; Luke, Max. 2013. Coal Killer: How Natural Gas Fuels the Clean Energy Revolution. Breakthrough Institute.

31. April Lee et al., “Interactions, Complementarities and Tensions at the Nexus of Natural Gas and Renewable Energy,” The Electricity Journal, 25 (December 2012).

32. Trembath, Alex; Nordhaus, Ted; Shellenberger, Michael; Luke, Max. 2013. Coal Killer: How Natural Gas Fuels the Clean Energy Revolution. Breakthrough Institute.

33. States,” Deloitte for Energy Solutions, January 2013. percent20Assets/Documents/Energy_us_er/us_er_GlobalImpactUSLNGExports_AmericanRenaissance_Jan2013.pdf