Liquefied natural gas (LNG) is natural gas (methane) converted to a liquid state for easier storage and transport.  It’s a common fuel or fuel additive in some vehicles.  LNG vehicles are most common in the medium-duty sector where set routes and fueling points are common.  It has an energy density equal to about 60% of diesel.

In its liquid state, natural gas takes up about 1/600th of the space that it would in its gaseous state.  Other advantages are that LNG is odorless, colorless, non-toxic (to the touch) and non-corrosive.  It is, however, very cold and will revert to its gaseous state when brought to warmer temperatures (making it easy to utilize as a gas).

The liquefaction process is also energy-intense compared to other methane storage types, including compressed natural gas (CNG), but because of its superior transportability, LNG remains a common choice.

The process requires the removal of some things that are found in natural gas such as dust, trace acid gases, helium, water, and heavy hydrocarbons.  The leftover, purified natural gas is then condensed under pressure until it turns liquid at a temperature of about -160°C (-260°F).  It can then be transported or stored under ambient pressure (6psi or lower) at that temperature.

Although it is occasionally used in vehicles, LNG is most commonly used as a means of transporting natural gas rather than as a way of utilizing it directly.  Specially-designed tankers for both water and road use are used for this purpose.

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