One of the questions I get most after showing people my CNG Freightliner Cascadia is “Why did you choose compressed over liquid?” I’ll be honest with everyone in letting you know it was what was available to me at the time. Now, after operating it for three months, I am glad it was what was available at the time!
Now having my feet wet in the natural gas and alternative fuels segment of our industry, I tell people I would now actually make the choice to have a CNG tractor for my application if given a choice of the many alternative fuels available. Although the choice criteria will differ for each individual operation, I see CNG being incorporated into different areas of trucking all the time. Just this past weekend I actually saw an SD (Severe Duty) two-axle chassis at the dealer with a backpack CNG tank on it getting ready for delivery at my local dealer. This would have been the same type of truck I would have used back in my pneumatic hauling days, when I would occasionally go off the beaten path to deliver powdered cement and fly-ash in a set of double pneumatic tankers.
The way to compare each fuel type for your application is to look at the advantages and disadvantages of each fuel type. The biggest comparison I am asked to confront is the difference between CNG and LNG, since they are two very distinct offshoots of the same fuel type. Here is a list of advantages and disadvantages of each, the information for which was attained from the web site for Agility Fuel Systems, the builder of my CNG fuel system (www.agilityfuelsystems.com/why-natural-gas/lng-vs-cng.html):
| CNG Advantages |
CNG Disadvantages |
| Unlimited hold times w/ no fuel loss |
Cost of compression - Station energy and maintenance |
| More mature technology |
Size of storage tanks |
| Gas/Vapor instead of Cryogenic |
Possible weight disadvantage |
| Simple fuel tanks and pressure management |
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| System design can be customized for application |
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| LNG Advantages |
LNG Disadvantages |
| Fewer tanks / Less space requirements |
Tank complexity |
| Greater fuel density |
Pressure and temperature management of fuel to engine complexity |
| Lower weight storage |
High maintenance costs of cryogenic parts |
| |
Use the fuel or lose it |
| |
Reliability is challenging |
| |
Life cycle fuel cost over CNG may be higher |
This of course is just a basic comparison for consideration when dealing with the choice between the two types of natural gas platforms. For me, the weight disadvantage was not a terrible sacrifice when compared to the complexity of an LNG system for a single-truck owner operator like myself. Being in Southern California, there are plenty of stations to fuel at for either, but I find a lot more CNG stations that are accessible for me in my area. This was yet another factor in me liking the switch to CNG. So, with all this new knowledge and time in the seat of the CNG truck, it would be a no-brainer for me to do over again at this point. If given the option I would definitely choose CNG again over LNG for my operation.