Natural Gas-powered turbines are a good idea. There are a couple of chinks in the armor though.
1) Natural gas doesn't give out the energy of other, more complex molecules. In fact, it gives a lot less. Also, the very nature of gases is a
problem. If you want to store enough of it to make its use worthwhile it has to be at a high pressure. This poses 2 problems. Not only is it a hazard
if it sustains damage as the pressure tears the structure apart, but the structure required to keep the gas at high pressures adds weight to the
aircraft, never a good idea.
2) Natural gas can be found in its... Erm... Natural form from decaying matter. Garbage, sewage, detritus, all that junk. It's commonly extracted
from city dumps. However, large amounts are also made from... You guessed it. Coal and Oil. I'm not saying all of it's made by them, but a fair
chunk of it is. Unfortunately, the conversion process from oil to natural gas is not entirely efficient, which sticks us with some energy loss.
Now these points are more relevant to methane. However, propane, for example, is a little bit different. At high pressures it turns into a nice
convenient liquid, which is why propane tanks can last for a while. So it'd be more convenient to use propane. In fact, it gives out more energy than
methane so it'd be a lot more convenient.
One thing I'd kind of like to point out is the use of hydrogen. It's most definitely a better option than any fossil fuels. Not only this but it
doesn't create any carbon dioxide, the dreaded greenhouse gas of death. It doesn't give out the energy of fossil fuels, but we are quite literally
swimming in oceans of it. It's good to see that we're moving over though and we may be able to use cleaner forms of energy. It could lead to use of
alternative energy sources in automobiles, always handy.

