Commonly Used Terms

Trying to make sense of CNG terminology? Here's a glossary to help you understand some of the technical language.

Btu (British Thermal Unit): Btu corresponds to the amount of energy required to raise the temperature of one pound mass of water by 1° F

DGE (Diesel Gallon Equivalent): DGE corresponds to the amount of CNG containing the same energy content as one gallon of diesel. Ultra-low sulfur diesel has slightly less energy than traditional diesel, so 1.35 therms per DGE is commonly cited conversion rate.

GGE (Gasoline Gallon Equivalent): GGE corresponds to the amount of CNG containing the same energy content as one gallon of gasoline. The typical conversion rate is 1.25 therms per GGE.

Inlet or Suction Pressure: Both inlet and suction pressure refer to the incoming pipeline gas pressure that supplies the CNG station. Inlet pressure is one of the main factors that determines the overall flow rate of a CNG station.

LNG (Liquefied Natural Gas): LNG is natural gas that has been cooled to -259 degrees Fahrenheit (-161 degrees Celsius) and then condensed into a colorless, odorless, non-corrosive and non-toxic liquid. LNG is characterized as a cryogenic liquid.

Methane: Methane (CH4), commonly known as natural gas, is an abundant, colorless gas that burns efficiently without many byproducts. As methane is naturally odorless, it has a distinctive odor added as a safety measure.

MMBtu: One Million Btu.

PSI (Pounds per Square Inch): PSI refers to pressure measured with respect to atmosphere pressure. Pressure gauges are adjusted to read zero at the surrounding atmospheric pressure.

SCF (Standard Cubic Foot): Contains approximately 1,000 BTU.

SCFM (Standard Cubic Feet per Minute): SCFM is the standard measurement for the flow rate of gas. A CNG station with a flow rate of 125 SCFM equates to 1 GGE per minute.

Therm: 100,000 British thermal units (BTU). A common measure of gas as sold by utilities.