Measuring natural gas: Equating feet to gallons
Joe Wilson is CEO of Infinity Resource Group, Inc., a professional mineral rights consulting firm in Parkersburg, W.Va., and a Registered Landman. David Pearl is managing director of a CNG patent holding company and president of a CNG fuel island development company. Your questions are welcomed by calling 412-535-9200 or by e-mailing joe@irg-energy.com.
You’d think that seasoned employees at gas companies could answer the most basic questions about compressed natural gas, like how many gallons of compressed natural gas will I need to run my car? Believe it or not, many don’t have a clue!
In pricing out gas contracts with one of the largest gas suppliers in the US we were shocked to learn that the 15 year tenured gas representative we spoke with was not even aware of the terms DGE (diesel gallon equivalents) or GGE (gasoline gallon equivalents.)
The purpose of this column is to make you smarter than (some) gas company employees!
Measuring natural gas can be very confusing. Unlike oil, which is measured in gallons or barrels, natural gas is usually measured in cubic feet. A cubic foot of gas is the amount of gas needed to fill a volume of one cubic foot under set conditions of pressure and temperature. Since both temperature and air pressure affect the energy content of a cubic foot of natural gas, the Standard Cubic Foot (SCF) is a way of standardizing the measurement; a SCF is one cubic foot of gas at 60 degrees Fahrenheit at sea level.
Gas companies sell their gas in cubic feet, and use meters to measure gas volume. However metering volume does not translate to workable measurements describing the energy content of the gas. Energy content is measured in British thermal units, commonly referred to as BTU. One BTU is the amount of natural gas that will produce enough energy to heat one pound of water (approximately a pint) by one degree Fahrenheit at normal pressure (at or close to its point of maximum density.)
One cubic foot of natural gas contains about 1,027 BTUs. When natural gas is delivered to a residence, it is measured by the gas utility in ‘therms’ for billing purposes. A therm is equivalent to 100,000 BTU, or just over 97 cubic feet, of natural gas. However in general, when measuring large amounts of natural gas, a therm is rounded up to denote 100 cubic feet and MCF is used to denote 1,000 cubic feet.
Selling natural gas for trucks and cars can hardly be sold in feet. As everyone knows, truck and car fuels are measured in gallons. Since gallons measure liquids, such as gasoline or diesel, and natural gas is sold in feet (or in therms) the natural gas industry sells natural gas in “equivalents.”
GGE, or Gasoline Gallon Equivalent, is the typical way Compressed Natural Gas (CNG) is sold at public fueling stations. One standard GGE = 900 BTUs of useable gasoline equivalent energy. CNG compresses the gas to 3,600 pounds per square inch (psi). At this compression level, one GGE requires 0.51 cubic feet of space in a CNG tank. So the interior space of a 20 GGE tank is approximately 10 cubic feet.
DGE, or Diesel Gallon Equivalent, is another way to rate CNG vehicle storage. Since Diesel has a higher energy content than gasoline (129,500 BTUs standard), 1 DGE = 1.136 GGE and 1 GGE = 0.88 DGE. If you want to calculate how many cubic feet would be required for an equivalent number of DGEs, just divide by 0.88 (in terms of Standard Cubic Feet, a DGE = 126.67/0.88 or 143.94 SCF and so forth). The reverse is also true. If, for example, you want to convert a cylinder capacity from GGE to DGE, you can multiply by 0.88. So, for example, a 24 GGE cylinder holds about 21 DGEs.
Most automobile drivers think in terms of gasoline and most truck drivers think in terms of diesel. In an effort to standardize weights and measures in the US CNG industry, the National Institute of Standards and Technology (NIST) formerly known as the National Bureau of Standards, requires that CNG fuels be standardized to GGE. Therefore truck drivers will have to start thinking in GGE instead of DGE in order to appreciate the standardized volumes and prices of CNG as the nation begins to convert to CNG.
The largest initial market converting to CNG fuels are trucks. There was a push to have the NIST standardize the CNG industry to DGE instead of GGE. However the NIST rebuffed the push and requires CNG stations to advertise official pricing and measurements in GGE. We agree with the NIST decision. We believe that CNG is the future fuel of America; although trucks are the initial market for CNG it is in the best interests of the country to have people beginning to think about CNG in terms of GGE because there is much more gasoline sold in the country than diesel fuel. Taking the long view of gasoline conversion will be better for the country, and over time, will be better for the CNG industry.
Obviously, the more demand there is for natural gas, mineral right values will likely increase. In determining whether a landowner owns valuable mineral rights, it is advisable to seek professional advice from a mineral rights consultant for an evaluation of the mineral rights. Before making any decision regarding the disposition of your mineral rights, it is always advisable to consult your lawyer and tax advisor.