Difference Between CNG and LPG


LPG and CNG are the two abbreviations used for two basic types of gases that exist in nature. Mainly these two gases are different because of the constituent from which these are composed. CNG has methane as its main constituent while LPG is formed from propane and butane. We all are aware of the fact that gas is a state of matter that has the ability to expand freely in the region or container in which it is present. For gases, it is said that these neither have fixed shape nor fixed volume.

In comparison to solids and liquids, the density of gases is quite low. The particles of gases are spaced apart from each other at specific distances due to the molecular kinetic energy.

This content is all about the difference between two major classifications of gases namely, LPG and CNG. Before proceeding one must have a basic idea about the definitions of the two gases. So, let us first have a look on the same.

Difference Between CNG and LPG


On the fundamental basis, the two types of gases are differentiated according to their major constituent. The major forming element of liquefied petroleum gas is propane and butane along with some light hydrocarbon gases that exist in the atmosphere. On the other side, in case of compressed natural gas, the main constituent that forms it is methane gas.


If we consider source as one of the differentiating factors then it is known that the main source of CNG is natural gas and condensate wells, oil wells and methane wells. Basically, its production is associated with extraction process deep within the earth. When this gas is extracted then it is to be cleaned so as to eliminate dirt. Also, its production after processing give rise to byproducts like ethane, propane, butane, pentane and hydrocarbons with high molecular weight.
As against, LPG is obtained automatically at the time of extraction of natural gas. Also, these are generated at the time of refining of petroleum.


If the ground of comparison is considered weight then one should note here that the weight of CNG is lighter than air and due to this reason when any leakage occurs then the natural gas gets dispersed in air at a rapid rate. On the contrary, LPG is comparatively heavier than air and so during leakages inspite of getting dispersed, LPG reaches to the lower ground level.


CNG is comparatively available at lower cost than LPG. However, the amount of energy production is more by LPG than CNG and therefore, depending on the cost at local level LPG can be more cost efficient than CNG.

Calorific Value

The calorific value of LPG is quite higher in comparison to CNG. The range of calorific value of LPG is between 90 to 95 MJ/m3 while that of CNG is between 35 to 40 MJ/m3. Thus, LPG is known to be a highly efficient fuel than biogas, petrol, diesel, CNG, etc.


There is a huge distribution hub of both CNG as well as LPG but at the retail level LPG is highly available. Basically, pipeline network is used to distribute CNG to residential and commercial regions.

Risk Associated

The level of danger or risk associated is more in case of LPG than CNG and this is due to the fact that LPG exhibits less diffusing in air ability. Thus, CNG is comparatively safe than LPG.

Greenhouse Gas

When combustion of CNG takes place then less amount of greenhouse gas is released in the air as it is constituted from methane. However, this is not the case with LPG because its combustion gives rise to production of carbon dioxide which is a greenhouse gas.

State at high pressure

If we talk about the properties displayed by the two under pressure then it is known that the state of CNG remains unchanged during pressure this means gas remains gas even after being compressed. While though LPG is a gas at normal temperature and pressure but it changes its state from gas to liquid when compressed. Therefore, CNG as well as LPG must be stored in packed containers.


The two types of gases exhibits usage at different domains. The natural gas can be used in automobiles to run vehicles as well as in locomotives. On the other side, liquefied gases are used in cooking, refrigerators and air conditioning units. Sometimes, LPG is also used as heating oil.

Quick Comparison: LPG Vs CNG

Full FormCompressed Natural GasLiquefied Petroleum Gas
Main constituentMethanePropane and Butane
WeightLight Comparatively heavier
Calorific value35 to 40 MJ/m390 to 95 MJ/m3
Environmental SafetyIt releases less greenhouse gases thus, is safe.More greenhouse gases are released thus is less safe.
State under high pressureGasLiquid


Hence, the above discussion concludes that both CNG and LPG have their respective advantages. LPG is non-toxic and non-corrosive. While CNG exhibits non-inflammable characteristics thus are quite safe to use.

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