Use of compressed natural gas, or CNG, as an alternative vehicle fuel is growing in significance with many city-owned fleets converting to the fuel. Though not renewable, CNG still holds some advantages over other fossil fuels such as petroleum. Here are five quick takeaways to help you understand the use of CNG as a transportation fuel.
The Safety of Compressed Natural Gas
One of the first questions raised about the use of CNG in vehicles is safety. Maybe it's because of its stealth persona as an odorless, colorless gas, but natural gas tends to strike fear into people over worries of explosion or related catastrophes. Yet, compressed natural gas has actually grown in popularity because it is seen, by those who actually know the facts, as a safe fuel choice. In fact, it's not too hard to see why CNG is actually considered to be safer than gasoline. Natural gas is lighter than air, so a spill won't puddle the way gasoline will nor will it sink close to the ground like propane. Instead, CNG rises into the air and then dissipates in the atmosphere. In addition, CNG has a higher ignition temperature. In other words, it's harder to ignite. Finally, CNG storage systems are much stronger than the typical gasoline tank found on a car or truck.
Where CNG Comes From
So where does CNG come from? The answer lies deep beneath your feet because natural gas is an organic compound, deposited deep within the earth. Although considered an alternative fuel, unlike many of its counterparts, natural gas is a fossil fuel and is primarily methane comprised of hydrogen and carbon. It is estimated that there are enough reachable deposits of natural gas below the Earth's surface to last long after stores of petroleum have been depleted, though the supply is not infinite by any stretch. In addition, there is controversy over the environmental impact of fracking, the method used to reach natural gas deposits lying deeper under the Earth's surface.
Using Natural Gas For Vehicles
The process of allowing natural gas to be used by a vehicle begins with natural gas being compressed and entering the vehicle through the natural gas dispenser or other filling means. From there, it goes directly into high-pressure cylinders located somewhere on the vehicle. When the car is accelerated, CNG leaves this on-board storage cylinder, passes along the fuel line and then enter the engine compartment where it enters the regulator which reduces the pressure from as high as 3,600 psi down to atmospheric pressure. A natural gas solenoid valve enables natural gas to move from the regulator into the gas mixer or fuel injectors. Mixed with air, natural gas flows on through the carburetor or the fuel injection system and from there, enters the engine's combustion chambers.
Compressed Natural Gas Vehicles
Although over 25 automakers produce nearly 100 models of natural gas vehicles and engines for the U.S. market, the only CNG vehicle available for personal consumer use is made by Honda. CNG's market in the U.S. has been primarily for transit buses, where over 10,000 are currently used in the country. It's estimated that about one in five buses currently on order are CNG vehicles. But numbers elsewhere around the world are much high with an estimated 7.5 million natural gas vehicles on the streets globally. That's twice what there was as recently as 2003. It's forecasted that by 2020, more than 65 million NGVs will be in use worldwide.
CNG is Cost Effective
CNG is also economically attractive. The U.S. Department of Energy has reported that the average nationwide price of a gallon of gas equivalent of CNG was as low as $2.04 per gallon in recent years. Prices are even lower in some areas of the country. Local and state governments have reported having their fuel bills cut in half by increasing the use of natural gas vehicles.