Natural Gas and the Environment

Natural gas well drilling operation

Source: Bureau of Land Management (public domain)

Natural gas has many qualities that make it an efficient, relatively clean, and economical energy source. There are, however, environmental and safety issues with its production and use. Many of the areas that are now being explored and developed for natural gas production are relatively pristine and or are wilderness areas, and development of these areas have large impacts on the area's environment, wildlife, and human populations.

Natural gas is a relatively clean burning fossil fuel

Burning natural gas for energy results in much fewer emissions of nearly all types of air pollutants and carbon dioxide (CO₂) per unit of heat produced than coal or refined petroleum products. About 117 pounds of carbon dioxide are produced per million Btu equivalent of natural gas compared to over 200 pounds of CO₂per million Btu of coal and over 160 pounds per million Btu of distillate fuel oil. These clean burning properties have contributed to an increase in natural gas use for electricity generation and as a transportation fuel for fleet vehicles in the United States.

Natural gas is mainly methane — A strong greenhouse gas

Natural gas is made up mostly of methane, which is a potent greenhouse gas. Some natural gas leaks into the atmosphere from oil and gas wells, storage tanks, pipelines, and processing plants. These leaks were the source of about 25% of total U.S. methane emissions, but only about 3% of total U.S. greenhouse gas emissions in 2011¹. The oil and natural gas industry tries to prevent gas leaks, and where natural gas is produced but can't be transported economically, it is "flared" or burned at well sites. This is considered to be safer and better than releasing methane into the atmosphere because CO₂ is not as potent a greenhouse gas as methane.

Natural gas exploration, drilling, and production has many environmental impacts

When geologists explore for natural gas deposits on land, they may have to disturb vegetation and soils with their vehicles. A gas well on land may require a road and clearing and leveling an area to make a drill pad. Well drilling activities produce air pollution and may disturb wildlife. Pipelines are needed to transport the gas from the wells, and this usually requires clearing land to bury the pipe. Natural gas production can also result in the production of large volumes of contaminated water. This water has to be properly handled, stored, and treated so that it does not pollute land and water.

While the natural gas that we use as a fuel is processed so that it is mainly methane, unprocessed gas from a well may contain many other compounds, including hydrogen sulfide, a very toxic gas. Natural gas with high concentrations of hydrogen sulfide is usually flared. Natural gas flaring produces CO₂, carbon monoxide, sulfur dioxide, nitrogen oxides, and many other compounds depending on the chemical composition of the natural gas and how well the gas burns in the flare. Natural gas wells and pipelines often have engines to run equipment and compressors, which produce additional air pollutants and noise.

Advances in drilling and production technologies have positive and negative impacts

New drilling and gas recovery technologies have greatly reduced the amount of area that has to be disturbed to produce each cubic foot of natural gas. Horizontal and directional drilling techniques make it possible to produce more gas from a single well than in the past, so fewer wells are needed to develop a gas field. Hydraulic fracturing (commonly called "hydrofracking," or "fracking," or "fracing") of shale rock formations is opening up large reserves of gas that were previously too expensive to develop. Hydrofracking involves pumping liquids under high pressure into a well to fracture the rock and allow gas to escape from tiny pockets in the rock. However, there are some potential environmental concerns that are also associated with the production of shale gas.

• The fracturing of wells requires large amounts of water. In some areas of the country, significant use of water for shale gas production may affect the availability of water for other uses, and can affect aquatic habitats.
• If mismanaged, hydraulic fracturing fluid — which may contain potentially hazardous chemicals — can be released by spills, leaks, faulty well construction, or other exposure pathways. Any such releases can contaminate surrounding areas.
• Hydrofracturing also produces large amounts of wastewater, which may contain dissolved chemicals and other contaminants that require treatment before disposal or reuse. Because of the quantities of water used and the complexities inherent in treating some of the wastewater components, treatment and disposal is an important and challenging issue.
• According to the United States Geological Survey, hydraulic fracturing "causes small earthquakes, but they are almost always too small to be a safety concern. In addition to natural gas, fracking fluids and formation waters are returned to the surface. These wastewaters are frequently disposed of by injection into deep wells. The injection of wastewater into the subsurface can cause earthquakes that are large enough to be felt and may cause damage."
• Natural gas may be released to the atmosphere during and after well drilling, the amounts of which are being investigated.

Strict safety regulations and standards are required for natural gas

Because a natural gas leak can cause an explosion, there are very strict government regulations and industry standards in place to ensure the safe transportation, storing, distribution, and use of natural gas. Because natural gas has no odor, natural gas companies add a strong smelling substance called mercaptan to it so that people will know if there is a leak. If you have a natural gas stove, you may have smelled this "rotten egg" smell of natural gas when the pilot light has gone out.