Difference Between CNG and LPG

Difference Between CNG and LPG: The full form of CNG is compressed natural gas and the full form of LPG is liquefied natural gas. Both LPG and CNG are used as fuels for various purposes. The primary difference between CNG and LPG lies in the components of these fuels. While CNG is primarily made up of Methane, LPG is primarily made up of Propane and Butane. Both LPG and CNG have some of their advantages and some of their disadvantages.

In this article, we are going to discuss the definition of LPG and CNG, the difference between LPG and CNG, their composition, similarities, and their uses.

What is CNG (Compressed Natural Gas)?

CNG stands for Compressed Natural Gas. As the name suggests, it contains methane in compressed form. It is a clean and non-pollutant fuel. CNG is cheaper than high-quality coals and also it is a clean fuel. CNG is mainly composed of methane (CH₄) and also contains other hydrocarbons in a small amount. CNG is created by compressing natural methane gas to far less than 1 percent of its original volume. CNG is cheaper than other fuels. The calorific value of CNG is 35 to 40 MJ/m³. CNG is stored at ambient temperature and high pressure. CNG is a supercritical fluid (a fluid at a temperature and pressure above the critical point where distinct liquid and gas phases do not exist). The combustion of CNG produces fewer undesirable gases than many other fuels. CNG has been used as a transportation fuel, mostly in public transit as an alternative to conventional fuel.

What is LPG (Liquefied Petroleum Gas)?

LPG stands for Liquified Petroleum Gas. It is a by-product of the refinery process. LPG consists of a mixture of light gaseous hydrocarbons like propane, butane, and other light petroleum products. Propane and butane make up the majority of LPG. These gases are filled in the storage tanks under extremely high pressure and turned into a liquid. LPG is normally used in domestic and commercial cylinders for cooking and other purposes. The calorific value of LPG is 90 to 95 MJ/m³. At ambient temperatures, LPG is liquid at about 8 bar. While LPG is used as a main fuel in a few cases, it is used as an ignition fuel to support subsequent liquid fuel operations or as a secondary fuel alternative for fuel oil. LPG has a somewhat higher adiabatic flame temperature. Storage of LPG is more complex as compared to other fuel oil.

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Difference between LPG and CNG

The following table lists the differences between LPG and CNG:

Comparison Basis	LPG	CNG
Definition	LPG refers to liquefied Natural gas which contains gas in liquified form.	CNG refers to compressed natural gas which contains gas in compressed form.
Composition	LPG mainly consists of propane and butane gas.	CNG mainly consists of methane gas.
Cost	LPG is costlier than CNG.	CNG is cheaper than LPG and other fuels.
Calorific Value	LPG has calorific value of 90 to 95 KJ/m3 , which is higher than CNG.	CNG has calorific value of 35 to 40 KJ/m3 , which is lesser than LPG.
Uses	LPG has mostly been used in cooking, as an industrial fuel, and also in refrigeration.	CNG is used as a clean fuel substituting gasoline.
Thermal Efficiency	The thermal efficiency of LPG is lower than CNG.	The thermal efficiency of CNG is higher than LPG.
How it is Collected/obtained	The method of collecting natural gas from aquifers is the primary source of obtaining propane and butane gas.	Methane gas are mostly obtained from oil and gas wells and pipelines, bed methane boreholes, coal wellholes, and natural injection wells.
Storage Pressure	The storage pressure of LPG is 2 MPa.	The storage pressure of CNG is 20-25 MPa.
Gases produced after Combustion	LPG mainly produces carbon dioxide which is greenhouse gas.	CNG produces very few greenhouse gases.
Octane Rating	LPG has lower octane rating.	CNG has higher octane rating.

Similarities Between LPG and CNG

There also exist some similarities between LPG and CNG. Some of them are mentioned below :

• Both of them are non-renewable energy resource.
• They are environmentally clean.
• Both of them are less expensive than other fossils.
• They both are highly flammable.
• Both of them are colorless.
• Both of them are odorless.
• Both of them are non-corrosive.
• Both of them are non-toxic.

Summary – CNG vs LPG

CNG (Compressed Natural Gas) and LPG (Liquified Petroleum Gas) are alternative fuels used for various purposes. CNG is mainly composed of methane and is known for being clean and cost-effective. It is commonly used in public transit. On the other hand, LPG consists of propane and butane and is a by-product of the refinery process. It is widely used in cooking and other domestic applications. While both are non-renewable, clean, and flammable, they differ in composition, cost, calorific value, uses, and storage pressure. CNG is lighter and produces fewer greenhouse gases, while LPG is denser and has a higher calorific value. The choice between them depends on factors like intended use and energy content.

FAQs on CNG and LPG

1. Which is better CNG or LPG?

The choice between LPG and CNG depends on various factors such as the intended use, storage and handling, energy content, cost, performance and many more things. CNG is better in terms of cost, greenhouse gases production while LPG is better in terms of calorific value, storage and handling.

2. Which is more Flammable LPG or CNG?

Liquefied Petroleum Gas (LPG) and Compressed Natural Gas (CNG) are both flammable gases, but they have different characteristics when it comes to flammability. LPG, which is a mixture of propane and butane, is heavier than air. In case of a leak, it tends to pool near the ground and can travel along the ground to an ignition source. LPG has a higher flammability range compared to natural gas, which means it can ignite at lower concentrations in the air. CNG is lighter than air, so it tends to rise and disperse into the atmosphere rapidly in case of a leak. Methane, the primary component of CNG, has a higher ignition temperature than the components of LPG.

3. Why LPG is not used in Vehicles?

It is dangerous to use LPG for vehicles as it can turn into fatal. LPG takes more space in vehicles and have chances of leakage. LPG has a lower energy content per unit volume compared to gasoline. LPG is stored in liquid form under moderate pressure, requiring specific storage and handling considerations. LPG vehicles may have a reduced driving range compared to gasoline vehicles due to the lower energy density of LPG.

4. Can I fill LPG in CNG Cars?

NO, one cannot fill LPG in a CNG car. These both are distinct types of alternative fuels, and vehicles are designed to use one or the other. If one will attempt to use the incorrect fuel type then it can lead to serious safety hazards and damage to the Car.

5. Is LPG expensive than CNG?

Generally LPG is costlier than CNG, but the cost of LPG and CNG depend on various factors such as as geographic location, market conditions, and government policies. CNG has a higher energy content per unit volume compared to LPG. Therefore, a vehicle running on CNG might achieve slightly better fuel efficiency compared to LPG.

6. What is the main difference between CNG and LPG?

CNG Primarily composed of methane (CH4) while LPG Comprises propane (C3H8) and butane (C4H10). Also LPG Produces more emissions compared to CNG.