Liquified Natural Gas (LNG) FAQ

What is liquefied natural gas (LNG)?

Liquefied natural gas (LNG) is natural gas that has been cooled to a temperature of around -162 degrees Celsius (-260 degrees Fahrenheit), converting it into a liquid state. Liquefaction makes natural gas easier to transport and significantly increases its energy density. LNG is a non-toxic, non-corrosive, colorless, and odorless liquid. It primarily consists of methane with low concentrations of other hydrocarbons, water, carbon dioxide, nitrogen, oxygen, and sulfur compounds.

How is LNG produced?

LNG is produced through a process called liquefaction. Natural gas is extracted from underground reservoirs and undergoes purification to remove impurities. It is then cooled in a series of heat exchangers until it reaches its liquefaction temperature, thus converting natural gas into a liquid form. When natural gas is cooled and converted to a liquid state, its density increases by about 600 times. The same volume of natural gas in its vapor form takes up only 1/600th of the space as LNG. This transformation allows LNG to possess energy content comparable to other liquid fuels, such as diesel.

What are the advantages of using LNG?

LNG offers several advantages. It is a cleaner-burning fossil fuel compared to coal and oil, releasing less carbon dioxide (CO2), sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate matter. Due to its minimal space requirements, LNG is more readily and cheaply transported long distances to areas without local gas reserves.  It can also be stored in larger quantities, making it a competitive energy source to meet future economic needs. Additionally, LNG can be used as a vehicle fuel, reducing dependence on conventional gasoline and diesel.

How is LNG transported?

The transportation of LNG requires specialized cryogenic vessels known as LNG carriers or tankers. These vessels’ design allows them to maintain the shallow temperatures necessary to keep the gas liquified. LNG can also be transported via pipelines, although this requires investment in infrastructure and is limited to certain geographical regions.

What are the primary uses of LNG?

LNG generates electricity for power plants. It’s also widely used as a heating fuel in residential, commercial, and industrial sectors. LNG is increasingly used as a transportation fuel, particularly in shipping and heavy-duty vehicles, drilling rigs, marine fuel, locomotives, and over-the-road trucks. In some instances, LNG can be converted back into its gaseous state and injected into natural gas pipelines.

Are there any safety concerns associated with LNG?

While LNG is generally safe, there are specific safety considerations. Leaks or spills are the primary concern, as LNG is flammable in its vapor form. That said, it remains a safe fuel even in vapor form due to its high ignition temperature of 1000 degrees Fahrenheit and narrow flammable range of 5 to 15 percent in air. Less than five percent does not contain enough natural gas to burn, while more than 15 percent has insufficient oxygen for combustion. LNG facilities and vessels feature stringent safety standards to mitigate these risks, including containment systems, emergency shutdown procedures, and extensive monitoring systems.

What is the environmental impact of LNG?

LNG has a lower environmental impact compared to other fossil fuels. Its combustion produces fewer greenhouse gas emissions, sulfur emissions, and particulate matter. The overall environmental impact depends on the entire life cycle of LNG, including extraction, liquefaction, transportation, and regasification. Methane leakage during these stages can impact its environmental performance.

Can LNG replace other energy sources entirely?

LNG can only partially replace some energy sources. While it can contribute to reducing greenhouse gas emissions and diversifying the energy mix, transitioning to renewable energy sources such as wind, solar, and hydroelectric power is essential for achieving long-term sustainability goals. LNG can act as a transitional fuel, helping to bridge the gap until cleaner alternatives become more widespread.

To compare the power LNG provides to other fuels, we can consider the Btu (British thermal unit) value per unit of measure. Here are the approximate Btu values:

  • One gallon of diesel: 139,000 Btu
  • One gallon of gasoline: 125,000 Btu
  • One gallon of LPG: 91,600 Btu
  • One gallon of LNG: 82,644 Btu

LNG provides around 61 percent of the energy provided by the same volume of diesel fuel.

Are there any global trends or developments related to LNG?

The LNG industry has experienced significant growth in recent years. Several countries have increased their LNG production capacities, and new LNG import terminals and regasification facilities are continuously under construction. Using LNG as a marine fuel is also gaining traction, driven by stricter emissions regulations in the shipping industry. Moreover, research and development efforts continue to focus on improving LNG storage, transportation, and regasification technologies.

How does LNG differ from LPG?

LPG, or liquid petroleum gas, is mostly propane or butane. It is a product derived from the refining process of crude oil. LPG is stored as a liquid under pressure, usually around 100 pounds per square inch gauge (psig). On the other hand, LNG gets made by cooling and liquefying natural gas. Natural gas is collected by drilling, and once processed and cooled to approximately -260 degrees Fahrenheit, it transforms into LNG.