Liquefied Petroleum Gas (LPG) and Its Uses
LPG's chemistry and physical properties, where it comes from, how it differs from LNG, storage and shipping, global demand, autogas in Türkiye, safety and environmental effects.
LPG (liquefied petroleum gas) is a flammable mixture consisting mainly of propane and butane, held as a liquid by modest pressure or moderate refrigeration. It comes from two sources: separation during natural gas and crude oil production, and refining, where it appears as a by-product. Global supply passed 370 million tonnes in 2024.[1] The chief markets are household cooking and heating, petrochemical feedstock, road fuel (autogas) and industry.
Composition and Physical Properties
The name covers a commercial blend. Propane (C₃H₈) and butane (C₄H₁₀) dominate, sometimes with isobutane and small amounts of propylene and butylene.[2] The physical gap between the two main components explains why blends vary by climate.
| Property | Propane | n-Butane |
|---|---|---|
| Boiling point | −42 °C | −0.6 °C |
| Vapour pressure at about 21 °C | 8.4 atm | 2.05 atm |
| Vapour density relative to air | 1.55 | 2.11 |
| Explosive limits in air (by volume) | 2.1% to 9.5% | 1.6% to 8.4% |
Source: NIOSH Pocket Guide to Chemical Hazards.[3][4] Values apply to the pure substances and shift in commercial blends.
Propane still vaporises in severe cold because it boils at −42 °C. Butane boils close to the freezing point of water and tends to stay liquid in a cold cylinder, delivering little gas. Winter and cold-climate blends therefore carry more propane.[2] The liquid has a density of roughly 0.50 to 0.58 kg/L, so it floats on water, and it expands about 250 times on vaporising, which makes it easy to carry.[2]
FuelEU Maritime uses a lower calorific value of 46.0 MJ/kg for LPG, set against 40.5 MJ/kg for heavy fuel oil and 49.1 MJ/kg for LNG.[5]
Energy and Volume Arithmetic
LPG is generally traded by weight. At a density of 0.54 kg/L, 46.0 MJ/kg works out at about 25 MJ/L, against about 22 MJ/L for LNG and about 40 MJ/L for heavy fuel oil. In volumetric terms LPG therefore sits close to LNG and well short of fuel oil.
Take a cylinder holding 12 kg of propane. Its energy content is 12 × 46.0 = 552 MJ, or about 153 kWh. The liquid occupies about 22 litres and would yield about 5.5 m³ of gas at the 250-fold expansion. Burning it produces about 36 kg of CO₂ at 3.000 tonnes per tonne of fuel.[2][5]
Pressure inside the cylinder depends on temperature and has little to do with how much remains. As long as liquid and vapour coexist, pressure equals the vapour pressure at that temperature, about 8.4 atm for pure propane at about 21 °C.[3] A pressure gauge therefore tells the user almost nothing about the contents until the cylinder is nearly empty. Weighing it does.
Where LPG Comes From
Gas leaving a well can carry ethane, propane, butane and heavier fractions alongside methane. Processing plants separate them, and the propane and butane are sold as LPG. Crude production releases similar gases. Refineries yield LPG as a light product of distillation and cracking, a process outlined in the article on the oil refinery.
Argus's statistical review for the World Liquid Gas Association (WLGA) shows supply rising by about 11 million tonnes in 2024 to over 370 million. US output reached 110 million tonnes and Middle Eastern output 52.5 million, and North America supplied about two-thirds of the growth.[1][9] Commercial LPG dates back further than most fuels now in use: the American chemist Walter Snelling isolated propane from gasoline in 1910, and the first products reached the market in 1912.[2]
LPG Against Natural Gas and LNG
Natural gas is mostly methane, and methane cannot be liquefied by pressure at ambient temperature, so LNG has to be cooled to about −162 °C. Propane and butane are heavier molecules that stay liquid in an ordinary steel cylinder at room temperature. Much of the difference in infrastructure follows from this. LPG can reach a single household in a small cylinder, whereas LNG distribution depends on cryogenic tanks and terminals.
| Property | LPG | LNG |
|---|---|---|
| Main component | Propane, butane | Methane |
| How it is kept liquid | Pressure or moderate refrigeration | Cryogenic cooling |
| Carriage temperature at atmospheric pressure | About −42 °C for propane | About −162 °C |
| Vapour behaviour | Heavier than air, collects low down | Rises once warmed |
| Lower calorific value | 46.0 MJ/kg | 49.1 MJ/kg |
| Combustion CO₂ | About 65 to 66 g/MJ | About 56 g/MJ |
Source: NIOSH; FuelEU default values.[3][4][5]
Storage and Transport
Liquid LPG expands as it warms, so containers are never filled to the top. Cylinders are typically filled to 80% to 85% of capacity.[2] Cylinders and bulk tanks serve homes and small businesses, and terminals rely on large pressure spheres or refrigerated tanks at atmospheric pressure.
Three kinds of ship carry it. Fully pressurised vessels are small and hold cargo at ambient temperature. Semi-refrigerated vessels carry propane at conditions such as −10 °C and 8.5 kg/cm² and can work with either kind of terminal. Fully refrigerated ships keep cargo close to atmospheric pressure, and the largest of them, the very large gas carriers (VLGCs), run to about 80,000 m³. BW Gemini, at 84,134 m³, is one example.[6][7] Lloyd's Register counts more than 1,600 LPG carriers in service, and seaborne trade reached a record 145 million tonnes in 2025.[8]
End Uses
Global demand passed 366 million tonnes for the first time in 2024, about 100 million higher than a decade earlier. China led at about 86 million tonnes, followed by the United States at 47 million and India at 33.4 million.[1] The structure of demand differs widely among them.
Chinese growth is driven by petrochemicals, where propane and butane feed the production of propylene and ethylene. Total Chinese demand rose by 5.1 million tonnes (6.3%) in 2024, and the country added 4.1 million tonnes a year of propane dehydrogenation (PDH) capacity.[1][9] India is mainly a household market, and in 2024 it overtook China as the largest residential consumer at 27.8 million tonnes.[9] Commercial users such as restaurants and hotels took almost 20 million tonnes, about 5% of the total.[1] Industrial furnaces, crop drying and heating in rural areas beyond the gas grid make up much of the remainder.
Propane also serves as a refrigerant under the designation R-290. It does not deplete the ozone layer and has a very low global warming potential, although its flammability has to be designed for.[2]
Autogas and Türkiye
Autogas is LPG sold as road fuel, and Türkiye is one of its biggest markets. Argus data put Turkish demand at 3.3 million tonnes, second only to Russia at 3.5 million. The vehicle fleet is listed at 4.9 million in Argus's table and 5.3 million by industry speakers, served by around 10,100 retail sites.[1]
The energy regulator EMRA's report for December 2025 shows 81.63% of that month's 321,793 tonnes of sales going to autogas, 14.68% to cylinders and 3.68% to bulk, with imports of 315,339 tonnes.[10] The split refers to a single month. Argus also notes that electric vehicles have reached about 30% of Turkish new car sales, a trend with obvious implications for future autogas demand.[1]
Safety
The defining hazard is vapour density. Propane vapour is 1.55 times and butane vapour 2.11 times as dense as air,[3][4] so leaked gas gathers in basements, ducts and ship bilges instead of dispersing. Propane's lower explosive limit of 2.1% also sits well below methane's roughly 5%, meaning a smaller accumulation can form an ignitable mixture.
Pure propane and butane have no smell, so consumer products usually carry an odorant such as ethyl mercaptan.[2] At high concentration in an enclosed space the gas can displace oxygen, and skin contact with the liquid causes cold burns as it flashes off. Gas detectors in low positions and ventilation designed around heavy vapour follow directly from these properties.
Environmental Profile
LPG produces fewer particulates and less sulphur oxide than coal or heavy fuel oil. On FuelEU default values its combustion CO₂ is 65.2 g/MJ for propane and 65.9 g/MJ for butane, placing it below heavy fuel oil at 76.9 and above LNG at 56.0.[5] It remains a fossil fuel.
Bio-LPG made from renewable feedstock is chemically identical and works in existing equipment, with reductions of up to 80% reported according to feedstock.[8] Renewable LPG and DME capacity stood at just 480,000 tonnes a year at the end of 2024, a tiny fraction of global supply.[1]
Supply is exposed to geopolitics as well. The Gulf conflict of 2026 hit Qatari condensate and LPG output together with LNG.[11] Ship fuel use is covered in a separate article on LPG as an alternative marine fuel.
Frequently asked questions
What is LPG?
LPG (liquefied petroleum gas) is a flammable mixture consisting mainly of propane and butane, held as a liquid by modest pressure or moderate refrigeration.
Is LPG the same as natural gas?
No. Natural gas is mostly methane. LPG is propane and butane, its vapour is heavier than air and it can be liquefied by pressure.
Why does LPG smell?
Pure propane and butane are odourless. An odorant is added so leaks can be noticed.
Why are LPG cylinders not filled completely?
The liquid expands as it warms, so cylinders are usually filled to 80% to 85% of capacity.
What is the difference between autogas and LPG?
Autogas is the name for LPG sold as road fuel.
Sources
- Argus Media. Q&A: Global LPG Growth Defies 2024 Headwinds, 16 September 2025 (WLGA statistical review).
- Wikipedia. Liquefied Petroleum Gas (secondary source).
- US National Institute for Occupational Safety and Health (NIOSH). Pocket Guide to Chemical Hazards: Propane.
- US National Institute for Occupational Safety and Health (NIOSH). Pocket Guide to Chemical Hazards: n-Butane.
- European Commission. Guidance on the FuelEU Maritime Regulation for Shipping Companies, 8 October 2025; Regulation (EU) 2023/1805, Annex II.
- Wikipedia. Gas Carrier (secondary source).
- MarineLink. World's First LPG-Fueled Gas Carrier, 4 November 2020.
- Lloyd's Register. LPG Highlighted as a Practical Pathway to Accelerate Decarbonisation, press release, May 2026.
- Butane/Propane News. A Roundup of 2025 Global LPG Dynamics, 28 October 2025.
- Hisse.net. LPG İthalatı 2025 Sonunda Yüzde 18'in Üzerinde Arttı, 14 February 2026 (Anadolu Agency, EMRA December 2025 LPG market report).
- Al Majalla. Can China's $3bn Loan to QatarEnergy Revive LNG Exports?, 2 November 2026.
