A little more than half of all homes have NG, while almost 100% of US homes have electricity. There are few public high pressure fast filling stations available, basically a non existent infrastructure that would need to be developed at high cost, while existing pipelines are failing.
The safety issue is significant. If a CNG vehicle catches fire the potential for damage is much higher than with a gasoline vehicle. Example: CNG Honda Explosion Notice the gasoline vehicles next to the CNG vehicle also caught fire but did not explode. More troubling are the high number of pipeline explosions that seem to occur, possibly with increasing frequency as older pipes fail. A Google search of "Natural Gas Explosion" brings up a long list, many with shocking video footage. This site seems to track some of the latest incidents Recent NG explosions I'm quite happy that I don't have a NG pipe going into my house or even in my neighborhood.
Using CNG in an inefficient ICE vehicle at maybe 20% efficiency makes little sense when it can be use in combined cycle generating plants at 60% efficiency to charge EV's. Additionally a few pipelines going to a few generating plants are much more efficient and easier to monitor and maintain than millions of pipelines going to millions of homes and public fill stations. If we are going to use CNG lets not waste it in ICE's, let's use it to displace coal fueled electricity.
Another more detailed look at CNG for transportation:
*Update: A recent study suggests that NG may have a larger carbon footprint than previously thought.
NG's higher emissions
Industry insiders question the realities of NG production
Problems with NG production
Smaller NG reserves than previously thought
Hinchey on Gas Reserves
Additional data on energy required to compress and transport NG by Rick Kermentz on Seeking Alpha:
The collection network (from a group of wells) is generally low pressure. The gas is scrubbed of sulfur compounds, odorant added, and compressed to 1,500 psi for long distance transport, with additional compressor stations every 40-60 miles. The pressure is dropped backed down to typically 100 psi for city distribution, and often down to 3 psi for residential distribution. A high volume NG filling station probably would access gas at 100-200 psi.http://seekingalpha.com/article/308660-electric-vehicles-ineptitude-apathy-and-piles-of-taxpayer-money#comment-2084470
To get a reasonable range in a CNG vehicle, the gas will be pressurized to 5,000-10,000 psi. Not only is there significant energy consumed compressing the gas, the thermal heat of compression is totally lost.
CNG Bus Fire
CNG Bus Explosion