What is Natural Gas?

CNG & LNG in Tennessee

Example fleets that use CNG or LNG TN: UPS, Dollywood, Scott Appalachian Industries, Waste Management, many gas utility districts, cities of Gatlinburg and Sevierville, Flatrock Concrete, Knoxville Utilities Board.

What do the acronyms mean – CNG, LNG, RNG? CNG is compressed natural gas, LNG is liquified NG and RNG is renewable natural gas (or CNG made from renewable sources like landfill gas or biomethane from digester operations).

How many CNG stations are there in Tennessee? As of fall 2016, there were 11 public CNG stations in Tennessee with numerous other fleets using CNG but with private refueling equipment. KUB in Knoxville is expected to open the newest CNG station in early 2017 just off of I-640!

image00-2 Natural gas, a domestically produced gaseous fuel, is readily available through the utility infrastructure. Whether produced via conventional or renewable methods, this clean-burning alternative fuel must be compressed or liquefied for use in vehicles

The United States has a widespread natural gas pipeline system, which can quickly and economically distribute natural gas to and from almost any location in the lower 48 states. Gas is distributed using 300,000 miles of transmission pipelines (see map), while an additional 1.9 million miles of distribution pipes transport gas within utility service areas.


How is it produced?

CNG is produced by compressing natural gas to less than 1% of its volume at standard atmospheric pressure. To provide adequate driving range, 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.

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), also 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 use in vehicles.


How is it used?

Natural gas powers about 150,000 vehicles in the United States and roughly 15.2 million vehicles worldwide. Natural gas vehicles (NGVs), which can run on compressed natural gas (CNG), are good choices for high-mileage, centrally fueled fleets that operate within a limited area. For vehicles needing to travel long distances, liquefied natural gas (LNG) is a good choice. The advantages of natural gas as a transportation fuel include its domestic availability, widespread distribution infrastructure, low cost, and inherently clean-burning qualities.

There are three types of NGVs:

  • Dedicated: These vehicles are designed to run only on natural gas.
  • Bi-fuel: These vehicles have two separate fueling systems that enable them to run on either natural gas or gasoline.
  • Dual-fuel: These vehicles are traditionally limited to heavy-duty applications, have fuel systems that run on natural gas, and use diesel fuel for ignition assistance.

Converting conventional vehicles to run on natural gas is a good option for incorporating alternative fuels into light- and heavy-duty fleet operations.


What are the benefits of natural gas?

Natural gas is safely and responsibly developed in 31 states across the United States, and it is 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 sources of gas 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 supplies of natural gas.

Compared with vehicles fueled by conventional diesel and gasoline, natural gas vehicles can produce lower levels of some emissions. And because CNG fuel systems are completely sealed, CNG vehicles produce no evaporative emissions. Natural gas is increasingly used to replace gasoline in smaller applications, such as in forklifts and commercial lawn equipment. Because natural gas is a low-carbon, clean-burning fuel, a switch 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.

Natural gas as compared to gasoline reduces emissions

  • Reduces carbon monoxide emissions 90%-97%
  • Reduces carbon dioxide emissions 25%
  • Reduces nitrogen oxide emissions 35%-60%
  • Potentially reduces non-methane hydrocarbon emissions 50%-75%
  • Emits fewer toxic and carcinogenic pollutants
  • Emits little or no particulate matter
  • Eliminates evaporative emissions

Natural gas as compared to diesel reduces emissions

  • Produce half the particulate matter of average diesel vehicles
  • Significantly reduce carbon monoxide emissions
  • Reduce nitrogen oxide and volatile organic hydrocarbon emissions by 50% or more
  • Potentially reduce carbon dioxide emissions 25% depending on the source of the natural gas
  • Drastically reduce toxic and carcinogenic pollutants
  • Increase methane emissions (not a benefit)


Find out how Waste Management powers refuse vehicles with renewable natural gas from the Altamont Landfill in California.

Natural Gas Station Locator

Natural Gas Information & Links

The Natural Gas section on the AFDC Website – Great starting point in learning about natural gas opportunities and technologies.

Fuel Economy.gov’s Natural Gas page

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