> Most retailers sell the NG by the pound.  This means that the gas has

been

compressed and actually becomes a liquid under compression.  Perhaps the
reference to "gallons"?
 >
 > Lloyd

People are getting things confused.

CNG = Compressed Natural Gas, is still a gas, has to be compressed to about
2000 psi to have a decent amount aboard the plane, requires sophisticated
fiber-wound tanks or heavy steel tanks to take the pressure, and will give
you about 1/2 the range of gasoline.  Also, unless the airport has a
compressor, their is no source for the high pressure natural gas (that in the
gas lines is very low pressure for safety reasons.) To fill from compressed
bottles you need a "tank farm" that has many bottles, and you progressively
fill from the lowest pressure bottle first, then the next, then the highest
pressure bottle.

LNG = Liquified Natural Gas, has been compressed (some) and COOLED to
cryogenic temperatures to get it to condense.  Not practical for airplane
use, requires cryogenic tanks, heat exchangers to vaporize it before going to
the engine, etc.  LNG is one method of shipping natural gas across the  ocean
because you can have a cryogenic insulated ship (tanker).  However, it has
not been widely used because of the hazards and expense.

LPG = Liquified Petroleum Gas, which is a mixture of propane (C3H8) or Butane
(C4H10), that does liquifiy under about 100psi pressure.  Used to heat mobile
homes and for your barbeque grill. Octane is good, burns cleanly, LPG
conversion common, but need someone to deliver the fuel.

Bill Schertz

 
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