Someone asked for the relative energies of natural gas compared to
 Gasoline. What I've been able to gather is :
 1 cu/ft NG=1028 BTU
 1 gal Gasoline=125000 BTU
 C. Smith

Those are "sit and burn" BTUs.

In actuality, the efficiency of gasoline as a motor fuel is very low,
while the efficiency of natural gas is very high.  Otherwise, a NG or
propane-fueled car would have pretty much no range or power.  There are
gas-powered Crown Vics in service as police cruisers!

Gasoline must be stable as a liquid, then rapidly broken down and
vaporized before it will burn, so most of a gallon of gas provides no
power.  Natural gas must simply be heated, and a far higher percentage
burns.

Keith W

Well there is still the high BTU per cubic foot of gasoline.
The tank needed for NG is also big and heavy.

Paul Lamar

That cubic foot of NG would be at STP.  Compress it to 3000 PSI and you
would have 200 cubic foot in each stored cubic foot.  205600 BTU per
stored cubic foot.

I found this table for various forms of liquid fuel:

  Rough gross values in Btu per lb
       -------------------------------------
       Crude oils                 18,300-19,500
       Gasolines                  20,500
       Kerosines                  19,800
       Benzole                    18,100
       Ethyl alcohol              11,600
       Gas oils                   19,200
       Fuel oils (bunker)         18,300
       Coal (bituminous)          10,200-14,600
       LNG                        22,300
       LPG (butane)               21,300
       -------------------------------------

LNG weighs about 3.9 lbs/gal or 29 lbs/cubic foot

So NG or LNG compares favourably to gasoline on a per pound basis, but
still need a heavy and/or bulky tank.  Doesn't sound good for aviation.

Bob W.