What is Natural Gas?

Natural gas, a domestically produced gaseous fuel, is readily available through our country’s utility infrastructure. Whether delivered via conventional or renewable methods, this clean-burning alternative fuel must be compressed or liquefied for vehicle use.

The United States has a widespread natural gas pipeline system, which quickly and economically distributes natural gas across the lower 48 states. Gas is distributed using 300,000 miles of transmission pipelines (see map below), while an additional 1.9 million miles of distribution pipes transport gas within utility service areas. (To learn more about natural gas in Tennessee, click here to find out what laws & incentives TN has for this alternative fuel.)

How is Natural Gas Produced?

CNG is produced by compressing natural gas to less than 1% of its volume at standard atmospheric pressure. CNG is stored onboard a vehicle in a compressed gaseous state within cylinders at a pressure of 3,000 to 3,600 pounds per square inch to provide adequate driving range.

Liquefied natural gas, or LNG, is natural gas in its liquid form. LNG is produced by purifying natural gas and super-cooling it to -260°F to turn it into a liquid. During the process known as liquefaction, natural gas is cooled below its boiling point, removing most of the compounds found in the fuel.

Renewable natural gas (RNG), known as biomethane, is produced from organic materials—such as waste from landfills and livestock—through anaerobic digestion. RNG qualifies as an advanced biofuel under the Renewable Fuel Standard. Because RNG is chemically identical to fossil-derived conventional natural gas, it can use the existing natural gas distribution system and must be compressed or liquefied for vehicle use.

How is Natural Gas used?

Natural gas powers about 150,000 vehicles in the United States and roughly 15.2 million vehicles worldwide. Natural gas vehicles (NGVs) can run on compressed natural gas (CNG) or liquified natural gas (LNG). CNG is the most widely used option (as well as the most commonly used alternative fuel) and is a good choice for high-mileage, centrally fueled fleets that operate within a city or regional area. For vehicles needing to travel long distances, liquefied natural gas (LNG) enables the cars to go longer distances on natural gas. The advantages of natural gas as a transportation fuel include its domestic availability, low cost, growing infrastructure, and inherently cleaner-

Three Types of NGVs



These vehicles are designed to run only on natural gas and are spark-ignited (SI) engines.



These vehicles have two separate fueling systems that enable them to run on either natural gas or gasoline, not both.

The engines are almost always spark-ignited and use a spark plug to provide the ignition point.



These vehicles are traditionally limited to heavy-duty applications and have fuel systems that run on natural gas and diesel simultaneously.

They are compression-ignition (CI) engines and use diesel as the “spark” for ignition. They typically burn on the order of 50% natural gas and 50% diesel.

What are the benefits of Natural Gas?

Natural gas is safely and responsibly developed in 31 states across the United States, putting Americans to work in all 50 states. How many jobs? IHS Global Insight estimates that as of 2008, total natural gas production supported more than 2.8 million jobs in the United States. Increasing the development of our nation’s unconventional gas sources alone will add more than 1.4 million U.S. jobs by 2015. A recent study by PricewaterhouseCoopers for the National Association of Manufacturers forecasts an additional 1 million U.S. jobs in manufacturing by 2025, thanks to our nation’s vast, affordable natural gas supplies.

Compared with vehicles fueled by conventional diesel and gasoline, natural gas vehicles can produce lower emissions. And because CNG fuel systems are completely sealed, CNG vehicles have no evaporative emissions. Natural gas is increasingly used to replace gasoline in smaller applications, such as forklifts and commercial lawn equipment. Because natural gas is a low-carbon, clean-burning fuel, switching to natural gas in these applications can result in substantial reductions of hydrocarbon, carbon monoxide, oxides of nitrogen, and greenhouse gas emissions.

What are the emissions reductions gained from Natural Gas?

Light-duty vehicles running on compressed natural gas (CNG) and liquefied natural gas (LNG) emit approximately 6%-11% lower levels of greenhouse gases than gasoline-powered vehicles throughout the fuel life cycle.

Natural gas produced via renewable methods offers additional benefits. Renewable natural gas (RNG) is essentially biogas—the gaseous product of the decomposition of organic matter—that has been processed to purity standards. Capturing biogas from landfills and livestock operations reduces emissions by preventing methane release into the atmosphere. Methane is 25 times stronger than carbon dioxide as a greenhouse gas. Additionally, producing biogas through anaerobic digestion reduces odors and produces nutrient-rich liquid fertilizer.

  • Reduces carbon dioxide emissions 10-15%; for RNG, that numbers shoot to over 80%
  • Emits little or no particulate matter (e.g., PM-10, PM-2.5); the reductions are massive as compared to pre-2008 diesel vehicles
  • Reduces carbon monoxide emissions by 50%-97%
  • Reduces nitrogen oxide emissions 35%-60%
  • Emits fewer toxic and carcinogenic pollutants
  • Reduces non-methane hydrocarbon emissions by 50%-75%
  • Emits little or no particulate matter
  • Virtually eliminates evaporative emissions

Natural Gas In Action

Tennessee Fleets Using Natural Gas

City of Gatlinburg

City of Sevierville


Flatrock Concrete

Numerous Gas Utility Districts such as MLGW, Piedmont NG, Gibson County Utility District, Athens Utilities Board, and Knoxville Utilities Board

Scott Appalachian Industries


Waste Management

What do the acronyms mean?

CNG – Compressed natural gas

LNG – Liquified natural gas

RNG – Renewable natural gas (or CNG made from renewable sources like landfill gas or biomethane from digester operations)