Natural Gas 101: Pros & Cons

Natural gas is a fossil fuel, like oil and coal. It's formed from decayed organic material transformed by high temperatures and pressures over millions of years into bubbles of methane gas. Conventional sources are found in underground gas fields or oil fields. Unconventional sources are more challenging to extract because the gas is locked inside the sediment. These include coalbed methane (trapped in the coalbed), tight gas (trapped in sandstone), gas hydrates (trapped in ice) and shale gas (trapped in shale). This last source is frequently in the headlines, thanks to advances in hydraulic fracturing, more commonly known as fracking. (1)

Considerable debate surrounds the recoverable size of the world's natural gas reserves. The U.S. Energy Information Administration estimates there are at least 6,800 trillion cubic feet (TCF) of proved natural gas reserves. The world is currently consuming a hefty 120 TCF a year, which means at least another 56 years of reserves. However consumption is growing every year and the EIA projects it will have doubled by 2040. Natural gas companies will need to discover new, unproved reserves and develop new ways to extract the natural gas in order to keep up with the increasing demand. (2)

This is a stunning rise for a power source that was once considered a mere byproduct of oil drilling. Though first used to power street lights in the early 1800s, and for heating and cooking in the 1900s, it still lagged far behind coal and oil. Only in the past fifty years has natural gas taken off, as methods for extracting and transporting improved. Now considered cleaner and cheaper than coal, it supplies 22% of the world's energy, used in heating, electricity generation and even as engine fuel. It's also heavily used in industrial applications, such as producing plastics and fertilizer. (3)

The top natural gas producers are the U.S., Russia, Iran and Canada.

Natural Gas Processing

After conducting geological surveys to detect the presence of conventional gas fields, a gas company will drill down to extract the gas. With unconventional sources, gas companies have to take additional steps to free the gas that is trapped in the sediment layers. In the case of hydraulic fracturing, pressurized fluids are injected into a layer of shale to create fractures in the rock from which the trapped gas bubbles can escape and be piped up to the surface. (4)

In its natural state (“wet”) natural gas is composed primarily of methane, with small percentages of heavier hydrocarbons, like ethane, butane and propane, and often water and other chemical compounds. After being refined into pure methane (“dry”), it's ready to be transported. Typically the gas is sent overland through an extensive network of pipelines. The U.S. alone has some 500,000 miles of pipeline. Natural gas can also be transported as liquid natural gas (LNG). The gas is chilled to -260℉ , when it condenses into a liquid 1/600th the previous volume. The LNG is then ready for transport to its destination, at which point it's converted back into a gas. (5)

Once at a power plant, the gas is burned to push a turbine, either by heating water to drive a steam turbine, heating air to drive a combustion turbine, or a combined cycle system where air is heated to drive a combustion turbine, and the hot exhaust is then used to heat water to drive a steam turbine. For each of these methods, the turbine then turns an electrical generator, creating electricity. (6)

Advantages & Disadvantages of Natural Gas

Natural gas burns cleaner than other fossil fuels, producing half the carbon dioxide as coal and about a third less than oil. It also emits fewer amounts of toxic chemicals like nitrogen oxides and sulfur dioxide. In the U.S. market, it is an abundant resource and currently the cheapest source of electrical power (an average of 6 cents per kilowatt hour, vs 9 cents for coal and hydroelectric and 11 cents for solar). (7)

Methane is a very powerful greenhouse gas, up to 20 times more potent than carbon dioxide. If improperly extracted, methane can be released into the atmosphere, or burnt off as flaring at oil fields, releasing many toxic compounds into the atmosphere. There is considerable debate about the environmental damage caused by fracking. While the evidence of groundwater contamination by drilling is mixed, there is more of a danger of contamination from poor transportation, storage and disposal practices of fracking wastewater. Micro-earthquakes are also a side effect of fracking. (8)

Future Trends

Natural gas is a growing industry. Countries with large shale gas reserves, like China, are attempting to replicate the U.S.'s fracking success. Gas companies are looking at ways to make transporting liquid natural gas cheaper, with the hopes of reaching new markets without the need for building expensive pipelines. The use of compressed natural gas as vehicle fuel, though small, is steadily growing in buses, garbage trucks and other kinds of municipal fleets. Researchers are working on ways to extract the potentially vast amounts of natural gas reserves trapped beneath the ocean in gas hydrates. (9)

Natural Gas Careers

The natural gas industry employs over 600,000 people. That figure is likely to only go up as more reserves are developed. Major fields include engineering, surveying, construction and well servicing. Many environmental careers are possible. Environmental lawyers deal with permitting and contracts. Environmental inspectors ensure that drilling and disposal meets all environmental regulations. Environmental lobbyists work to persuade local, state and federal government agencies to improve existing regulations. (10)












David Newland

A frequent writer for National Geographic and Smithsonian, David is an avid follower and learner of the environment. From traveling around the world to learn and observe new cultures to writing about shark attack survival, you'll always get an interesting world class environmental approach.