Fracking
I am not an expert on all this but it seems to me that the way Natural Gas is produced is pretty darned harmful to our environment. It's a process called fracking. To learn more about fracking see the documentary called "GasLand". According to the documentary fracking is very harmful to our ground water and it seems that little is being done to stop it.
So, I think while there are some benefits to propane, it's downside is very harmful and the overall cost is very high - something that we must not allow.
- Joe