CNG has less “firepower” than Diesel, right? I think its in the 90,000 BTU range (Therm) vs. Diesel with 140,000 BTU per gallon.
The energy density is somewhere around 26 MJ/L for LNG vs 36MJ/L for diesel...what do you bet the conversion in the chart above is by volume? If you convert by energy density, diesel and LNG look to be priced exactly the same (or pretty close).
Also, what is keeping this company from just buying a tanker full of fuel and refueling at their warehouse?
There is a "combined cycle" engine that is purported to be MORE efficient that basic diesel. Such an engine uses both natgas and diesel. Double injectors on each cylinder. The natgas injection provides most of the BTU's for driving, and a very small amount of diesel injected retains the "compression/ignition" of the diesel and obviates the need for a spark ignition source.
I suspect that for future "big rigs" that such engines will become the drive option of choice.