CNG & LNG – What’s the difference

Compressed Natural Gas and Liquefied Natural Gas: What’s the Difference?


Are you confused about the difference between Compressed Natural Gas and Liquefied Natural Gas? Well, while both are natural gases, they have notable differences. Read on to find more about these two gases.


What is Compressed Natural Gas?


Natural gas is the cleanest burning of all fossil fuels. Compressed natural gas produces lower greenhouse gases than gasoline and diesel and significantly less particulate emissions.


What Do You Benefit from by Using Compressed Natural Gas?


  • Compressed natural gas burns cleaner than gasoline, diesel and propane, producing fewer greenhouse gases and less particulate emissions.
  • Compressed natural gas costs less than other fuel products. A gallon of gas equivalent (GGE) is about one-third of premium-grade gasoline and half of regular gas.
  • It is easy to switch from gasoline/diesel to compressed natural gas in existing vehicles. A skilled mechanic can convert a diesel vehicle into a compressed natural gas-powered car with only a few hours of work.
  • CNG is not volatile or explosive. Since it is natural and in small amounts, it poses no danger to humans and the environment.


What is Liquefied Natural Gas?


Liquefied natural gas (LNG) is a liquid form of natural gas. It takes up about 1/600th the volume of methane in the gaseous state at standard temperature and pressure, allowing for much easier transport via tankers, ships, trucks, and pipelines. Even more, liquefied natural gas is odourless when handled as an inert substance. Most people odourise the gas for the sake of safety.


What Do You Benefit from by Using Liquefied Natural Gas?


  • High-efficiency liquefied natural gas power plants can reduce GHG emissions by up to 80% over traditional fossil fuels.
  • Liquefied natural gas is often cheaper than other fuels. In the 21st century, the cost of natural gas has dropped, and this trend is expected to continue to grow.
  • Liquefied natural gas is cleaner than other fuels. The fuel burns up cleanly with almost no residuals. It produces no sulfur dioxide or mercury, unlike coal that pollutes the air with large amounts of sulfur dioxide (SO2) and mercury, which cause respiratory problems.
  • Liquefied natural gas can be used for various purposes, including energy generation for power plants, heating houses and a backup when the electrical grid fails.
  • LNG facilities are quickly built and transported. The major components of an liquefied natural gas facility can be manufactured at a factory, shipped to the site and assembled in one place. As such, it is less expensive than multiple on-site pieces that need to be constructed.


What are the Similarities between Liquefied Natural Gas and Compressed Natural Gas?


  • Both are stored under low temperatures (-162 degrees Celsius for liquefied natural gas) as well as high pressures (up to 200 bar)
  • Both gases are natural and extracted from landfills
  • Both have an energy yield of about 42 megajoules per litre
  • Each of these fuel sources produces fewer particulates in the air than gasoline
  • CNG and LNG both have an electrical equivalent of about 60 cents per kilowatt-hour (kWh)


What are the Differences between CNG and LNG?

The Usage

Compressed natural gas is primarily used for vehicles and trains, while liquefied natural gas is used mainly for large-scale storage and transport. These applications include city buses, delivery trucks, personal passenger cars and light-duty trucks and heavy-duty trucks.


Fuel Consumption Rate

Liquefied natural gas vehicles usually have a lower fuel consumption rate than compressed natural gas when travelling at the same distance. However, you must understand that there are exceptions to this rule in both cases. It depends on the car’s manufacturers.


Production of Nitrogen Oxides

Compressed natural gas produces 90% fewer nitrogen oxides than service diesel, and liquefied natural gas has 53% fewer nitrogen oxides when combusted compared to conventional gasoline engines. While both alternative fuels do not produce toxic emissions from their exhausts, they also reduce tailpipe emissions by returning clean air into the atmosphere.


Required Pressure for Production

Liquefied natural gas and compressed natural gas are both natural gases and can be used for vehicles. Nevertheless, there are some specifications that you must understand before using either option for your car. The major difference being that compressed natural gas is produced at a higher pressure than liquefied natural gas and cannot be directly used in engine hardware designed to work with liquid natural gas. For this reason, a compressed natural gas vehicle must have two tanks, a liquefied natural gas tank to store the fuel as liquid and a compressed natural gas tank that compresses it for use in the engine.


The Storage of Liquefied Natural Gas and Compressed Natural Gas

Liquefied natural gas storage is much more economical than compressed natural gas, making it the preferred method for long-term storage and shipping. In the process of liquefied natural gas or compressed natural gas storage, almost all of the critical parts are designed to be filled with nitrogen and helium, which is completely different from air pressure tanks that store LP Gas. Even more, compressed natural gas does not need to be cooled when transporting or storing.


The Control

Liquefied natural gas is much more challenging to control than compressed natural gas. This makes it harder for manufacturers to produce non-flammable cars that run on liquefied natural gas. However, Liquefied Natural Gas is more environmentally friendly since it releases fewer particulates into the air than compressed natural gas.


How Can You Get Liquefied Natural Gas and Compressed Natural Gas?

The easiest way to buy liquefied natural gas is from a company that manufactures and distributes the fuel. Usually, these companies will install or retrofit your vehicle with the tank necessary to store liquefied natural gas. On the other hand, the best way to get compressed natural gas is at a fuelling station that stocks compressed natural gas, readily available in most areas.


Conclusion: Which is better?

Both are excellent choices, and their availability will only continue to increase as the need for cleaner, more sustainable fuel sources become more well known. While it has been around for a while, liquefied natural gas vehicles have only been available for 20 years. However, they are still not widespread as Compressed Natural Gas vehicles. On the other hand, the advantages of Compressed Natural Gas are its availability, lower cost and ‘cleaner’ emissions.

Generally, your choice of natural gas will depend on preference and application.

Part of the distribution chain for LNG involves its gasification for transport by road or rail in pressure vessels. The compressed natural gas (CNG) concept is once again being applied to sea transport as an alternative to transporting the gas in its liquid form.

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