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Natural Gas and Climate Change

Natural gas is of interest for climate change mitigation both for its potential role as a low-carbon substitute for other fossil fuels, and for the direct warming effect of uncombusted methane. As a fuel, natural gas less carbon-intensive than liquid fuels and coal, and may offer low-cost, near-term opportunities for CO2 abatement in many sectors. Steam reforming of natural gas is also the least-cost technology for production of hydrogen,⁶ which may one day be an important part of the energy system.⁷ However, uncombusted methane that escapes to the atmosphere is a potent greenhouse gas, having 25 times the global warming potential of an equivalent mass of CO2.⁸ Therefore, while using natural gas in place of alternative fuels may mitigate climate change, it can also make the problem worse if gas is released uncombusted to the atmosphere.

Where the requisite infrastructure for delivering natural gas to end users does not exist, natural gas has little value as a fuel. Natural gas tends to be most abundant in regions that also have oil reserves, and the process of drilling for oil typically produces fugitive emissions of natural gas. Therefore, in oil-rich regions without natural gas processing facilities and transportation infrastructure, the fugitive emissions of natural gas are either vented or flared. Flaring produces about 210 Mt of CO2 each year,⁹ one third of which occur in Africa,¹⁰ and another third in the Middle East.¹¹ Fugitive emissions from oil drilling operations account for about 10 Mt of methane each year, equivalent in global warming potential to 250 Mt of CO2; more than two thirds of this occurs in Africa, Latin America, the Middle East, and the Former Soviet Union.¹²

Fugitive emissions from natural gas systems and coal mining are also large globally, accounting annually for about 50 Mt CH4 and 35 Mt CH4, respectively.¹³ The prospect of extracting coal-bed methane for energy has attracted the attention of researchers and energy companies for decades,¹⁴ but the magnitude of annual emissions indicates that the practice isn't very widespread. A study of global mitigation potentials of methane found that even without any climate-motivated policy, about half of global coal-related methane emissions could be profitable to capture and market for energy uses.¹⁵

Because of the value of methane as a fuel, practices and technologies that reduce emissions of methane can be economically profitable, potentially offering cost-effective mechanisms for climate change mitigation. Worldwide, various initiatives have been undertaken to reduce methane emissions (note that not all methane emissions are from natural gas). The Methane to Markets Partnership, ¹⁶ for example,  is an voluntary international partnership aiming to minimize methane emissions from a variety of sources, stressing the importance of implementing methane capture and use projects in developing countries and countries with economies in transition.The Partnership is a collaboration between developed countries, developing countries, and countries with economies in transition—together with strong participation from the private sector. ¹⁷ The Natural Gas STAR and Natural Gas STAR International partnerships have been created in support of the Methane to Markets Partnership. ¹⁸ 

The Global Gas Flaring Reduction partnership (GGFR) is a public-private partnership of governments, state-owned companies and major international oil companies committed to reducing gas flaring and venting. The partnership facilitates and supports national efforts to capture, process, distribute, and market the natural gas from oil production. It addresses the lack of effective regulatory frameworks and the constraints on gas utilization, such as insufficient infrastructure and poor access to local and international energy markets, particularly in developing countries. ¹⁹

Formation of Natural Gas

While the origins are not known with certainty, and there is some variation in the geologic history of different reserves, scientists generally believe that gas is formed over millions of years from organic matter, usually from former marine or coastal ecosystems. Organic matter from ecosystems became covered in layers of mud and other sediments, and as more mud and other sediments piled on top of the organic matter, the pressure and temperatures increased. This pressure and temperature increase is thought to cause the organic materials to slowly transform into natural gas and oil. ²⁰ Because of its low density, once formed, it tends to rise towards the surface of the earth through fissures and pores, but may become trapped under less permeable rock layers.

Exploration 

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Recoverable reserves of natural gas tend to occur where caprocks constrain the upward movement of gas through bedrock (see figure). Geologists and geophysicists usually use seismology to find out areas which have the right conditions for a gas or oil deposit. High-speed computers that help develop three-dimensional underground maps as well as satellite image technology are also widely used to discover natural gas resources. Drilling is conducted after an initial exploration.²¹

Consumption

Natural gas is used in the electric power sector, in both baseload (generally combined cycle) plants and peak load combustion turbines. In industry, it is used as a feedstock in the manufacture of plastics, fertilizer, and other chemicals, and it is also an important fuel for producing steam, and for direct process heat.²⁹ In buildings, it is used for space heating, water heating, cooking, and other applications, and in some regions it is used as a transport fuel. In the U.S., a number of cities use compressed natural gas (CNG) as fuel for transit buses; while this practice is generally done to improve urban air quality, research indicates that low-emissions diesel may be a more cost-effective option.³⁰

The 2008 US International Energy Outlook 2008 predicts that the total world natural gas consumption will increase from 104 trillion cubic in 2005 to 158 trillion cubic feet in 2030. The strongest increase comes from the non-OECD nations, where natural gas consumption grows more than twice as fast as in the OECD countries. The non-OECD nations are projected to account for 90 percent of the world’s total increase in natural gas production from 2005 to 2030. China and India are projected to almost double their production volumes from 2005 to 2015. ²⁹

Environmental Impacts

Natural Gas is often cited as the cleanest fossil fuel. Compared to the average air emissions from coal, natural gas produces half as much carbon dioxide and less than a third as much nitrogen oxides. However pollutants and heat build up in the water used in natural gas boilers and is often discharged into lakes and rivers. Natural gas extraction and exploration can also drastically change and destroy natural habitats.

Footnotes

¹³¹⁰¹³: NaturalGas.org (2004). Background.

²Energy Information Administration (2008). Nonrenewable Energy - Natural Gas. U.S. Department of Energy.

³Energy Information Administration (2008). Nonrenewable Energy - Natural Gas. U.S. Department of Energy.

⁴Energy Information Administration (2009). Fuel and Energy Source Codes and Emission Coefficients. U.S. Department of Energy, Energy Information Administration, Voluntary Reporting of Greenhouse Gases Program.

⁵Energy Information Administration (2008). Nonrenewable Energy - Natural Gas. U.S. Department of Energy.

⁶Global Energy Technology Strategy Program (2007). Hydrogen Systems.

 ⁷U.S. Department of Energy (2009). DOE Hydrogen Program Home Page.

⁸Intergovernmental Panel on Climate Change (2007). Fourth Assessment Report, Chapter 2, Table 2.14. Working Group I: The Physical Science Basis of Climate Change.

⁹Carbon Dioxide Information Analysis Center (2008). Global CO2 Emissions from Fossil-Fuel Burning, Cement Manufacture, and Gas Flaring: 1751-2005.

¹⁰Carbon Dioxide Information Analysis Center (2008). Global CO2 Emissions from Fossil-Fuel Burning, Cement Manufacture, and Gas Flaring: 1751-2005, Africa.

¹¹Carbon Dioxide Information Analysis Center (2008). Regional CO2 Emissions from Fossil-Fuel Burning, Cement Manufacture, and Gas Flaring: 1751-2005, Middle East.

¹²Netherlands Environmental Assessment Agency (2007), EDGARV32FT. Regional CH4 emissions per source category.

¹³Netherlands Environmental Assessment Agency (2007), EDGARV32FT. Regional CH4 emissions per source category.

¹⁴U.S. Geological Survey. Coal-Bed Methane: Potential and Concerns.

¹⁵Energy Modeling Forum, Methane Data for EMF 21. Coal (zip file).

¹⁶: United States Environmental Protection Agency, Methane to Markets Partnership, www.epa.gov.

¹⁷: Methane to Markets, Methane to Markets Partnership Fact Sheet, www.methanetomarkets.org.

¹⁸: United States Environmental Proection Agency, Natural Gas STAR Program, www.epa.gov.

¹⁹: The World Bank, Flared Gas Utilization Strategies: Opportunities for Small Scale Uses of Gas, 2004, www-wds.worldbank.org.

²⁰ Pacific Gas and Electricity Company, Natural Gas Formation, Exploration, and Distribution, www.pge.com.

²¹Naturalgas.org (2004). Exploration.

²²Energy Information Administration (2008). Definitions, Sources and Explanatory Notes. Petroleum Navigator.

²³Energy Information Administration (2008). Natural Gas Annual 2007. Table 1: Summary Statistics for Natural Gas in the United States.

²⁴Energy Information Administration (2008). EIA Energy Kids' Page - Natural Gas Timeline, 1937.

²⁵: US Department of State, Background Note: Quatar, US Department of State , www.state.gov.

²⁶: Pars Special Economic Energy Zone, www.pseez.ir.

²⁷Energy Information Administration (2008). Natural Gas Annual 2007. Table 1: Summary Statistics for Natural Gas in the United States.

²⁸Oak Ridge National Laboratory (2008). Transportation Energy Data Book, Appendix A. P. A-14.

²⁹Naturalgas.org (2004). Uses in Industry.

³⁰New York City Transit Department of Buses (2003). Comparison of Clean Diesel Buses to CNG Buses. DEER Conference 2003, Newport, RI.

³¹: US Energy Information Administration, International Energy Outlook 2008: Chapter 3, Natural Gas, www.eia.doe.gov.