Natural Gas Science Facts

Explore the chemical composition and physical properties of natural gas.

Natural gas is a gaseous mixture of several components. Below is a list of the gases that make up the average pipeline gas distributed by NW Natural and other natural gas properties.

Chemical composition: component gas formula
percentage by volume

     
 Methane   CH4   93.59 
           
 Ethane   C2H6   3.75 
           
 Propane
 C3H8   0.92 
           
 Isobutane   C4H10   0.11 
           
 Butane   C4H10   0.15 
           
 Isopentane   C5H12   0.02 
           
 Pentane   C5H12   0.02 
           
 Other Hexanes
 C6H14+   0.01 
           
 Carbon Dioxide
 C02   0.25 
           
 Nitrogen   N2   1.19 
           
 Oxygen   O2   0.01 
           
 T-Butyl Mercaptan
 C4H10S   <30 ppm
           
 Methyl Ethyl Sulfide
 C2H6S   <3 ppm
           
 Hydrogen Sulfide
 H2S   <5 ppm
     
     

Physical data

  • Freezing Point (760 mm Hg): -182.6° C (-296.7° F)
  • Boiling Point (760 mm Hg): -161.5° C (-258.7° F)
  • Gas Specific Gravity: 0.55 to 0.64 (air = 1.00)
  • Specific Gravity of Liquefied Natural Gas: 0.42 to 0.46 (water = 1.00)
  • Gas Density (varies slightly): 0.0438 lbm/scf
  • Vapor Pressure: Gaseous at 60° F,1 atmosphere and completely volatile

Physical properties

Natural gas is flammable, with no color, odor, or taste. If trace amounts of sulfur compounds are present, the gas has a characteristic garlic/rotten egg/skunk odor. Natural gas also becomes a liquid at cryogenic (super cold) temperatures (-260° F).

Energy and conversion factors

Common fuel unit btu content:

  • Natural Gas Therm 100,000
  • Propane Gallon 92,500
  • Liquefied Natural Gas Gallon 85,800
  • Electricity Kilowatt-hour 3,413
  • Diesel (Light #2, same as Heating Oil) Gallon 140,000
  • PS 300 Gallon 150,000
  • Bunker C Heavy Barrel (42 gal) 6,400,000

Conversions

  • 1 Ton A/C = 12,000 BTU per hour
  • 1 Boiler HP = 42,000 BTU Input (@ approx. 80% efficiency)
  • 100 Boiler HP = 42 Therms Input (@ approx. 80% efficiency)
  • 100 lb. Steam = 1 Therm (approx.)
  • 1 Engine HP = 10,000 BTU Input (approx.)
  • 1 British Thermal Unit = Energy required to raise the temperature of 1 lb. mass of water by 1° F
  • 1 SCF Natural Gas = 1,000 BTU (approx.)
  • 100 SCF Natural Gas = 1 Therm (approx.)
  • 1 MSCF Natural Gas = 1,000 SCF
  • 1 MSCF Natural Gas = 10 Therm
  • 1 Therm = 29.3 Kilowatt Hour
  • Standard Cubic Foot = Volume of gas at standard conditions
  • Standard Conditions = 60° F at 14.73 psia (approx.)
  • SCFH = Volume flow rate per hr. at standard conditions
  • Degrees Rankine = Degrees Fahrenheit + 459.67°