- The Writer holds an MSc in Eurasian Political Economy & Energy from King’s College London and also an MA in European Studies from Sabancı University.
The selection of transportation fuel is determined by factors including vehicle type, length and weight limitations, type of cargo and driving conditions among others. Among the many fuel choices available today, the emerging use of natural gas for transportation has already made its mark being environmentally friendly and cheaper to use. Of the most widely available and appropriate transportation fuel, natural gas in the form of Compressed Natural Gas (CNG) or Liquefied Natural Gas (LNG) will be examined.
Both CNG and LNG predominantly compose of methane, and are essentially the same but only differ in the way they are stored. There is no specific engine type for LNG or CNG , but they are delivered to the vehicle engines in the form of natural gas.
CNG is created by multi state gas compression by 3,600 per square inch and thus occupies less than 1 percent of the volume it normally holds under standard atmospheric pressure. CNG is stored in high-pressure cylinders tanks to be used in the Natural Gas Vehicles (NGVs). Due to its ease of handling, it can be easily used in trucks that regularly refuel on a daily basis. On the other hand, LNG is stored in double-wall insulated tanks as a super cooled liquid. The cooling process compresses natural gas by 620 times.
Fuel safety is a concern and natural gas is relatively much safer than other fuels such as LPG (with specific gravity of 1.5219) since natural gas is lighter than air (with specific gravity of 0.5537), meaning that it swiftly dissipates in the air when exposed to the environment.
However, CNG and LNG are less energy dense compared to gas, but NGV’s require bigger fuel tanks, thus increasing their overall weight in transportation compared to petrol-fuelled vehicles. For instance, an LNG tank with a storage capacity of 60 diesel gallons equivalent (DGE) would weigh 498.9 kg when the tank is full, in contrast to a CNG tank with the same capacity of 60 DGE , which would weigh 725.7kg. Therefore, when choosing fuel, energy density should be considered since it will increase the overall weight of the vehicle and increase the overall fuel consumption. CNG is recommended for fleets running on shorter routes while LNG is proposed for fleets driving long distances.
For vehicles that are constantly in operations, LNG offers the better option compared to CNG because refueling is much quicker. Even though CNG offers two types of stations – the time-fill and the fast-fill, the time-fill option requires a longer period of time to refill while the fast-fill option is speedier alternative for the fleets that operate around the clock.
There is a great deal of bewilderment among fleet and truck dealers on whether CNG or LNG is the best fuel for their needs. The determining factor is in the priority of the transportation needs. It is vital to consider the right factors to clearly describe and evaluate the priorities of the company’s operations to make the most appropriate choice for optimizing fuel costs. With its quick refilling options, LNG favors fleets that are in constant operation travelling over long distances, while CNG offers a good option for fleets that travel short distances, supported by relative price advantages with less sensitivity to heavy weight.
Although major differences exist between CNG and LNG as a fuel of choice in the transportation sector, the few numbers of refueling stations is one of the most significant obstacles that hinders overall growth in NGV’s around the world. To expand CNG or LNG use as a transportation fuel would require the expansion of refueling stations for the proliferation of NGV’s. This requires further investment and government incentives to support the substantial infrastructure needed.
To move to a lower cost fuel and thereby increase the overall competitive advantage, both CNG and LNG are worthy fuels. The use of CNG will be further advanced with recent technological developments in full composite tanks that allow for lower weight with an extended lifespan, which increases the overall ability of CNG fuelled vehicles to travel longer distances.
In line with the quest to meet governments’ demands in diminishing carbon emissions and reduce heavy dependence on petroleum-fuelled vehicles, many forward looking companies and organizations have taken further steps towards achieving a future in which either CNG or LNG would provide the optimum in cleaner energy resources.
- Opinions expressed in this piece are the author’s own and do not necessarily reflect Anadolu Agency's editorial policy